Localization of neonatal Fc receptor for IgG in aggregated lymphoid nodules area in abomasum of Bactrian camels (Camelus bactrianus) of different ages.

PubMed

Zhang, Wang-Dong; Wang, Wen-Hui; Li, Shu-Xian; Jia, Shuai; Zhang, Xue-Feng; Cao, Ting-Ting

2016-10-20

The neonatal Fc receptor (FcRn) plays a crucial role in transporting IgG and associated antigens across polarized epithelial barriers in mucosal immunity. However, it was not clear that FcRn expression in aggregated lymphoid nodules area (ALNA) in abomasum, a unique and important mucosal immune structure discovered only in Bactrian camels. In the present study, 27 Alashan Bactrian camels were divided into the following five age groups: fetus (10-13 months of gestation), young (1-2 years), pubertal (3-5 years), middle-aged (6-16 years) and old (17-20 years). The FcRn expressions were observed and analyzed in detail with histology, immunohistochemistry, micro-image analysis and statistical methods. The results showed that the FcRn was expressed in mucosal epithelial cells of ALNA from the fetus to the old group, although the expression level rapidly declined in old group; moreover, after the ALNA maturated, the FcRn expression level in the non-follicle-associated epithelium (non-FAE) was significantly higher than that in FAE (P < 0.05). In addition, the FcRn was also expressed in the vessel endothelium, smooth muscle tissue, and macrophages and dendritic cells (DCs) of secondary lymphoid follicles (sLFs). It was demonstrated that FcRn was mainly expressed in non-FAE, the effector sites, although which was expressed in FAE, the inductive sites for mucosal immunity. And it was also expressed in DCs and macrophages in sLFs of all ages of Bactrian camels. The results provided a powerful evidence that IgG (including HCAb) could participate in mucosal immune response and tolerance in ALNA of Bactrian camels through FcRn transmembrane transport.

Activation-induced proteolysis of cytoplasmic domain of zeta in T cell receptors and Fc receptors.

PubMed

Taupin, J L; Anderson, P

1994-12-01

The CD3-T cell receptor (TCR) complex on T cells and the Fc gamma receptor type III (Fc gamma RIII)-zeta-gamma complex on natural killer cells are functionally analogous activation receptors that associate with a family of disulfide-linked dimers composed of the related subunits zeta and gamma. Immunochemical analysis of receptor complexes separated on two-dimensional diagonal gels allowed the identification of a previously uncharacterized zeta-p14 heterodimer. zeta-p14 is a component of both CD3-TCR and Fc gamma RIII-zeta-gamma. Peptide mapping analysis shows that p14 is structurally related to zeta, suggesting that it is either: (i) derived from zeta proteolytically or (ii) the product of an alternatively spliced mRNA. The observation that COS cells transformed with a cDNA encoding zeta express zeta-p14 supports the former possibility. The expression of CD3-TCR complexes including zeta-p14 increases following activation with phorbol 12-myristate 13-acetate or concanavalin A, suggesting that proteolysis of zeta may contribute to receptor modulation or desensitization.

IgE Inhibits Toll-like Receptor 7- and Toll-like Receptor 9-Mediated Expression of Interferon-α by Plasmacytoid Dendritic Cells in Patients With Systemic Lupus Erythematosus.

PubMed

Khoryati, Liliane; Augusto, Jean-François; Shipley, Emilie; Contin-Bordes, Cécile; Douchet, Isabelle; Mitrovic, Stéphane; Truchetet, Marie-Elise; Lazaro, Estibaliz; Duffau, Pierre; Couzi, Lionel; Jacquemin, Clément; Barnetche, Thomas; Vacher, Pierre; Schaeverbeke, Thierry; Blanco, Patrick; Richez, Christophe

2016-09-01

Plasmacytoid dendritic cells (PDCs) play a central role in pathogenesis of systemic lupus erythematosus (SLE) through their unique ability to produce large amounts of type I interferon (IFN) upon Toll-like receptor 7 (TLR-7) and TLR-9 triggering. PDCs express specific surface regulatory receptors involved in negative regulation of IFNα secretion. These receptors use the γ-chain of high-affinity Fc receptor (FcR) for IgE, FcɛRI. We undertook this study to test our hypothesis that IgE engagement of FcɛRI on PDCs may impact IFNα production in SLE patients. Serum levels of total IgE were measured in healthy volunteers, SLE patients, and patients with IgE-dependent allergic disorders. FcɛRI expression on PDCs from SLE patients was evaluated by flow cytometry. Purified PDCs were incubated with monoclonal IgE for 24 hours, then stimulated for 18 hours with TLR agonists or immune complexes (ICs). IFNα production by PDCs was detected by quantitative real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay. Expression of TLR-7, TLR-9, and IFN regulatory factor 7 (IRF-7) in PDCs was quantified by quantitative real-time PCR. We observed significantly higher IgE levels in SLE patients with quiescent disease than in those with active disease. In SLE patients, IgE levels correlated inversely with disease activity. IgE levels were not associated with the presence of antinuclear IgE. Purified PDCs treated for 24 hours with monoclonal IgE up-regulated FcɛRI expression in an IgE dose-dependent manner. IgE-treated PDCs significantly decreased IFNα secretion and down-regulated CCR7 expression upon stimulation with TLR-7 and TLR-9 ligands and ICs from lupus patients. IgE treatment down-regulated expression of TLR-9 and IRF-7. Our results support the notion that IgE plays a protective role in SLE pathogenesis through the modulation of inflammatory response by PDCs. © 2016, American College of Rheumatology.

Structural Heterogeneity and Functional Domains of Murine Immunoglobulin G Fc Receptors

NASA Astrophysics Data System (ADS)

Ravetch, Jeffrey V.; Luster, Andrew D.; Weinshank, Richard; Kochan, Jarema; Pavlovec, Amalia; Portnoy, Daniel A.; Hulmes, Jeffrey; Pan, Yu-Ching E.; Unkeless, Jay C.

1986-11-01

Binding of antibodies to effector cells by way of receptors to their constant regions (Fc receptors) is central to the pathway that leads to clearance of antigens by the immune system. The structure and function of this important class of receptors on immune cells is addressed through the molecular characterization of Fc receptors (FcR) specific for the murine immunoglobulin G isotype. Structural diversity is encoded by two genes that by alternative splicing result in expression of molecules with highly conserved extracellular domains and different transmembrane and intracytoplasmic domains. The proteins encoded by these genes are members of the immunoglobulin supergene family, most homologous to the major histocompatibility complex molecule Eβ. Functional reconstitution of ligand binding by transfection of individual FcR genes demonstrates that the requirements for ligand binding are encoded in a single gene. These studies demonstrate the molecular basis for the functional heterogeneity of FcR's, accounting for the possible transduction of different signals in response to a single ligand.

The Human Membrane Cofactor CD46 Is a Receptor for Species B Adenovirus Serotype 3

PubMed Central

Sirena, Dominique; Lilienfeld, Benjamin; Eisenhut, Markus; Kälin, Stefan; Boucke, Karin; Beerli, Roger R.; Vogt, Lorenz; Ruedl, Christiane; Bachmann, Martin F.; Greber, Urs F.; Hemmi, Silvio

2004-01-01

Many human adenovirus (Ad) serotypes use the coxsackie B virus-Ad receptor (CAR). Recently, CD46 was suggested to be a receptor of species B Ad serotype 11 (Ad11), Ad14, Ad16, Ad21, Ad35, and Ad50. Using Sindbis virus-mediated cDNA library expression, we identify here the membrane cofactor protein CD46 as a surface receptor of species B Ad3. All four major CD46 transcripts and one minor CD46 transcript expressed in nucleated human cells were isolated. Rodent BHK cells stably expressing the BC1 form of CD46 bound radiolabeled Ad3 with a dissociation constant of 0.3 nM, identical to that of CD46-positive HeLa cells expressing twice as many Ad3 binding sites. Pull-down experiments with recombinant Ad3 fibers and a soluble form of the CD46 extracellular domain linked to the Fc portion of human immunoglobulin G (CD46ex-Fc) indicated direct interactions of the Ad3 fiber knob with CD46ex-Fc but not CARex-Fc (Fc-linked extracellular domain of CAR). Ad3 colocalized with cell surface CD46 in both rodent and human cells at the light and electron microscopy levels. Anti-CD46 antibodies and CD46ex-Fc inhibited Ad3 binding to CD46-expressing BHK cells more than 10-fold and to human cells 2-fold. In CD46-expressing BHK cells, wild-type Ad3 and a chimeric Ad consisting of the Ad5 capsid and the Ad3 fiber elicited dose-dependent cytopathic effects and transgene expression, albeit less efficiently than in human cells. Together, our results show that all of the major splice forms of CD46 are predominant and functional binding sites of Ad3 on CD46-expressing rodent and human cells but may not be the sole receptor of species B Ads on human cells. These results have implications for understanding viral pathogenesis and therapeutic gene delivery. PMID:15078926

The human membrane cofactor CD46 is a receptor for species B adenovirus serotype 3.

PubMed

Sirena, Dominique; Lilienfeld, Benjamin; Eisenhut, Markus; Kälin, Stefan; Boucke, Karin; Beerli, Roger R; Vogt, Lorenz; Ruedl, Christiane; Bachmann, Martin F; Greber, Urs F; Hemmi, Silvio

2004-05-01

Many human adenovirus (Ad) serotypes use the coxsackie B virus-Ad receptor (CAR). Recently, CD46 was suggested to be a receptor of species B Ad serotype 11 (Ad11), Ad14, Ad16, Ad21, Ad35, and Ad50. Using Sindbis virus-mediated cDNA library expression, we identify here the membrane cofactor protein CD46 as a surface receptor of species B Ad3. All four major CD46 transcripts and one minor CD46 transcript expressed in nucleated human cells were isolated. Rodent BHK cells stably expressing the BC1 form of CD46 bound radiolabeled Ad3 with a dissociation constant of 0.3 nM, identical to that of CD46-positive HeLa cells expressing twice as many Ad3 binding sites. Pull-down experiments with recombinant Ad3 fibers and a soluble form of the CD46 extracellular domain linked to the Fc portion of human immunoglobulin G (CD46ex-Fc) indicated direct interactions of the Ad3 fiber knob with CD46ex-Fc but not CARex-Fc (Fc-linked extracellular domain of CAR). Ad3 colocalized with cell surface CD46 in both rodent and human cells at the light and electron microscopy levels. Anti-CD46 antibodies and CD46ex-Fc inhibited Ad3 binding to CD46-expressing BHK cells more than 10-fold and to human cells 2-fold. In CD46-expressing BHK cells, wild-type Ad3 and a chimeric Ad consisting of the Ad5 capsid and the Ad3 fiber elicited dose-dependent cytopathic effects and transgene expression, albeit less efficiently than in human cells. Together, our results show that all of the major splice forms of CD46 are predominant and functional binding sites of Ad3 on CD46-expressing rodent and human cells but may not be the sole receptor of species B Ads on human cells. These results have implications for understanding viral pathogenesis and therapeutic gene delivery.

Principles of antibody-mediated TNF receptor activation

PubMed Central

Wajant, H

2015-01-01

From the beginning of research on receptors of the tumor necrosis factor (TNF) receptor superfamily (TNFRSF), agonistic antibodies have been used to stimulate TNFRSF receptors in vitro and in vivo. Indeed, CD95, one of the first cloned TNFRSF receptors, was solely identified as the target of cell death-inducing antibodies. Early on, it became evident from in vitro studies that valency and Fcγ receptor (FcγR) binding of antibodies targeting TNFRSF receptors can be of crucial relevance for agonistic activity. TNFRSF receptor-specific antibodies of the IgM subclass and secondary cross-linked or aggregation prone dimeric antibodies typically display superior agonistic activity compared with dimeric antibodies. Likewise, anchoring of antibodies to cell surface-expressed FcγRs potentiate their ability to trigger TNFRSF receptor signaling. However, only recently has the relevance of oligomerization and FcγR binding for the in vivo activity of antibody-induced TNFRSF receptor activation been straightforwardly demonstrated in vivo. This review discusses the crucial role of oligomerization and/or FcγR binding for antibody-mediated TNFRSF receptor stimulation in light of current models of TNFRSF receptor activation and especially the overwhelming relevance of these issues for the rational development of therapeutic TNFRSF receptor-targeting antibodies. PMID:26292758

Fc gamma RII/III and CD2 expression mark distinct subpopulations of immature CD4-CD8- murine thymocytes: in vivo developmental kinetics and T cell receptor beta chain rearrangement status.

PubMed

Rodewald, H R; Awad, K; Moingeon, P; D'Adamio, L; Rabinowitz, D; Shinkai, Y; Alt, F W; Reinherz, E L

1993-04-01

We have recently identified a dominant wave of CD4-CD8- (double-negative [DN]) thymocytes in early murine fetal development that express low affinity Fc gamma receptors (Fc gamma RII/III) and contain precursors for Ti alpha/beta lineage T cells. Here we show that Fc gamma RII/III is expressed in very immature CD4low single-positive (SP) thymocytes and that Fc gamma RII/III expression is downregulated within the DN subpopulation and before the CD3-CD8low SP stage in T cell receptor (TCR)-alpha/beta lineage-committed thymocytes. DN Fc gamma RII/III+ thymocytes also contain a small fraction of TCR-gamma/delta lineage cells in addition to TCR-alpha/beta progenitors. Fetal day 15.5 DN TCR-alpha/beta lineage progenitors can be subdivided into three major subpopulations as characterized by cell surface expression of Fc gamma RII/III vs. CD2 (Fc gamma RII/III+CD2-, Fc gamma RII/III+CD2+, Fc gamma RII/III-CD2+). Phenotypic analysis during fetal development as well as adoptive transfer of isolated fetal thymocyte subpopulations derived from C57B1/6 (Ly5.1) mice into normal, nonirradiated Ly5.2 congenic recipient mice identifies one early differentiation sequence (Fc gamma RII/III+CD2(-)-->Fc gamma RII/III+CD2(+)-->Fc gamma RII/III-CD2+) that precedes the entry of DN thymocytes into the CD4+CD8+ double-positive (DP) TCRlow/- stage. Unseparated day 15.5 fetal thymocytes develop into DP thymocytes within 2.5 d and remain at the DP stage for > 48 h before being selected into either CD4+ or CD8+ SP thymocytes. In contrast, Fc gamma RII/III+CD2- DN thymocytes follow this same developmental pathway but are delayed by approximately 24 h before entering the DP compartment, while Fc gamma RII/III-CD2+ display accelerated development by approximately 24 h compared with total day 15.5 thymocytes. Fc gamma RII/III-CD2+ are also more developmentally advanced than Fc gamma RII/III+CD2- fetal thymocytes with respect to their TCR beta chain V(D)J rearrangement. At day 15.5 in gestation, beta chain V(D)J rearrangement is mostly, if not entirely, restricted to the Fc gamma RII/III-CD2+ subset of DN fetal thymocytes. Consistent with this analysis in fetal thymocytes, > 90% of adult thymocytes derived from mice carrying a disrupting mutation at the recombination-activating gene 2 locus (RAG-2-/-) on both alleles are developmentally arrested at the DN CD2- stage. In addition, there is a fivefold increase in the relative percentage of thymocytes expressing Fc gamma RII/III in TCR and immunoglobulin gene rearrangement-incompetent homozygous RAG-2-/- mice (15% Fc gamma RII/III+) versus rearrangement-competent heterozygous RAG-2+/- mice (< 3% Fc gamma RII/III+). Thus, Fc gamma RII/III expression defines an early DN stage preceding V beta(D beta)I beta rearrangement, which in turn is followed by surface expression of CD2. Loss of Fc gamma RII/III and acquisition of CD2 expression characterize a late DN stage immediately before the conversion into DP thymocytes.

Induction of functional Fc receptors in P388 leukemia cells. Requirement for multiple differentiation signals.

PubMed

Cohen, D A; Stotelmyer, N L; Kaplan, A M

1985-04-01

The development of functional Fc receptors (FcR) during induced differentiation with the tumor promoter, phorbol myristate acetate (PMA), was studied in the murine tumor cell line, P388. PMA induced the appearance of FcR on the membranes of P388 cells as indicated by the binding of IgG-coated sheep red blood cells (IgG-SRBC). Concentrations of PMA as low as 1 ng/ml were sufficient to induce the expression of FcR as well as to inhibit cellular division and to induce adherence in the P388 tumor cell line; however, optimal FcR induction occurred at PMA concentrations of 10-100 ng/ml. Immunofluorescent analysis with heat-aggregated myeloma proteins indicated that PMA induced FcR which were capable of binding IgG2a and IgG2b immunoglobulins, but not IgG1. Adherence to a substratum was determined to be a second required signal for expression of FcR, since PMA induction of P388 tumor cells in teflon dishes failed to fully develop FcR and adherence of P388 cells to poly-L-lysine-coated culture dishes in the absence of PMA was insufficient for FcR expression. FcR which appeared after PMA induction were non-functional in the sense that membrane-bound IgG-SRBC were not ingested to any significant extent by the tumor cells. However, if FcR induction occurred in the presence conA-induced rat spleen cell culture supernatants, phagocytosis of membrane-bound erythrocytes occurred. These findings suggest that for the expression of FcR which are capable of particle internalization, at least three identifiable membrane-transmitted signals are required during differentiation.

Identification of the low affinity receptor for immunoglobulin E on mouse mast cells and macrophages as Fc gamma RII and Fc gamma RIII.

PubMed

Takizawa, F; Adamczewski, M; Kinet, J P

1992-08-01

In addition to their well characterized high affinity immunoglobulin E (IgE) receptors (Fc epsilon RI) mast cells have long been suspected to express undefined Fc receptors capable of binding IgE with low affinity. In this paper, we show that Fc gamma RII and Fc gamma RIII, but not Mac-2, on mouse mast cells and macrophages bind IgE-immune complexes. This binding is efficiently competed by 2.4G2, a monoclonal antibody against the extracellular homologous region of both Fc gamma RII and Fc gamma RIII. Furthermore, IgE-immune complexes bind specifically to Fc gamma RII or Fc gamma RIII transfected into COS-7 cells. The association constants of IgE binding estimated from competition experiments are about 3.1 x 10(5) M-1 for Fc gamma RII, and 4.8 x 10(5) M-1 for Fc gamma RIII. Engagement of Fc gamma RII and Fc gamma RIII with IgE-immune complexes (after blocking access to Fc epsilon RI) or with IgG-immune complexes triggers C57.1 mouse mast cells to release serotonin. This release is inhibited by 2.4G2, and at maximum, reaches 30-40% of the intracellular content, about half of the maximal release (60-80%) obtained after Fc epsilon RI engagement. These data demonstrate that mouse Fc gamma RII and Fc gamma RIII are not isotype specific, and that the binding of IgE-immune complexes to these receptors induces cell activation.

Identification of the low affinity receptor for immunoglobulin E on mouse mast cells and macrophages as Fc gamma RII and Fc gamma RIII

PubMed Central

1992-01-01

In addition to their well characterized high affinity immunoglobulin E (IgE) receptors (Fc epsilon RI) mast cells have long been suspected to express undefined Fc receptors capable of binding IgE with low affinity. In this paper, we show that Fc gamma RII and Fc gamma RIII, but not Mac-2, on mouse mast cells and macrophages bind IgE-immune complexes. This binding is efficiently competed by 2.4G2, a monoclonal antibody against the extracellular homologous region of both Fc gamma RII and Fc gamma RIII. Furthermore, IgE-immune complexes bind specifically to Fc gamma RII or Fc gamma RIII transfected into COS-7 cells. The association constants of IgE binding estimated from competition experiments are about 3.1 x 10(5) M-1 for Fc gamma RII, and 4.8 x 10(5) M-1 for Fc gamma RIII. Engagement of Fc gamma RII and Fc gamma RIII with IgE-immune complexes (after blocking access to Fc epsilon RI) or with IgG-immune complexes triggers C57.1 mouse mast cells to release serotonin. This release is inhibited by 2.4G2, and at maximum, reaches 30-40% of the intracellular content, about half of the maximal release (60-80%) obtained after Fc epsilon RI engagement. These data demonstrate that mouse Fc gamma RII and Fc gamma RIII are not isotype specific, and that the binding of IgE-immune complexes to these receptors induces cell activation. PMID:1386873

The effect of omalizumab treatment on the low affinity immunoglobulin E receptor (CD23/fc epsilon RII) in patients with severe allergic asthma.

PubMed

Assayag, Miri; Moshel, Shabtai; Kohan, Martin; Berkman, Neville

2018-01-01

Omalizumab is an anti-immunoglobulin E (IgE) monoclonal antibody used in the treatment of severe asthma. Its therapeutic efficacy is primarily attributed to reduction of serum-free IgE and in the expression of high-affinity IgE receptor, fc epsilon RI. However, its effect on the low-affinity IgE receptor fc epsilon RII/CD23 in vivo has not been evaluated. To determine whether CD23 plays a role in the inflammatory process in severe uncontrolled asthma and whether anti-IgE therapy modulates fc epsilon RII/CD23 expression in these patients. We evaluated the expression of IgE receptors fc epsilon RI, fc epsilon RII/CD23, and soluble CD23 (sCD23), and the activation state of peripheral blood monocytes (tumor necrosis factor alpha, interleukin (IL) 1-beta, transforming growth factor (TGF) beta expression) in the patients with severe asthma before and after 24 weeks of omalizumab treatment and in the healthy controls. Cytokine expression of monocytes in response to different stimulation (IL-4, IL-4 plus IgE, IL-4 plus IgE plus anti-IgE, and IL-4 plus IgE plus anti-IgE plus anti-CD23 for 72 hours) was determined by enzyme-linked immunosorbent assay. Treatment with omalizumab (for 24 weeks) improved disease control and pulmonary function (forced expiratory volume in the first second of expiration, 64.5 versus 74%; p = 0.021). Mean ± SE expression of fc epsilon RI on monocytes was higher in the patients with asthma versus the controls (45.7 ± 12.2% versus 18.6 ± 5.8%; p = 0.04) and was reduced after omalizumab treatment (45.7 ± 12.2% versus 15.6 ± 4.4%; p = 0.027). Mean ± SE TGF-beta levels in supernatants from monocytes were reduced in the patients treated with omalizumab (211 ± 6 pg/mL versus 184 ± 9 pg/mL; p = 0.036). Modulation of the low affinity IgE receptor CD23 in severe asthma is complex, and sCD23 may inversely reflect disease activity. Treatment with omalizumab was associated with reduced monocyte activation.

An investigation into IgE-facilitated allergen recognition and presentation by human dendritic cells

PubMed Central

2013-01-01

Background Allergen recognition by dendritic cells (DCs) is a key event in the allergic cascade leading to production of IgE antibodies. C-type lectins, such as the mannose receptor and DC-SIGN, were recently shown to play an important role in the uptake of the house dust mite glycoallergen Der p 1 by DCs. In addition to mannose receptor (MR) and DC-SIGN the high and low affinity IgE receptors, namely FcϵRI and FcϵRII (CD23), respectively, have been shown to be involved in allergen uptake and presentation by DCs. Objectives This study aims at understanding the extent to which IgE- and IgG-facilitated Der p 1 uptake by DCs influence T cell polarisation and in particular potential bias in favour of Th2. We have addressed this issue by using two chimaeric monoclonal antibodies produced in our laboratory and directed against a previously defined epitope on Der p 1, namely human IgE 2C7 and IgG1 2C7. Results Flow cytometry was used to establish the expression patterns of IgE (FcϵRI and FcϵRII) and IgG (FcγRI) receptors in relation to MR on DCs. The impact of FcϵRI, FcϵRII, FcγRI and mannose receptor mediated allergen uptake on Th1/Th2 cell differentiation was investigated using DC/T cell co-culture experiments. Myeloid DCs showed high levels of FcϵRI and FcγRI expression, but low levels of CD23 and MR, and this has therefore enabled us to assess the role of IgE and IgG-facilitated allergen presentation in T cell polarisation with minimal interference by CD23 and MR. Our data demonstrate that DCs that have taken up Der p 1 via surface IgE support a Th2 response. However, no such effect was demonstrable via surface IgG. Conclusions IgE bound to its high affinity receptor plays an important role in Der p 1 uptake and processing by peripheral blood DCs and in Th2 polarisation of T cells. PMID:24330349

An investigation into IgE-facilitated allergen recognition and presentation by human dendritic cells.

PubMed

Sharquie, Inas K; Al-Ghouleh, Abeer; Fitton, Patricia; Clark, Mike R; Armour, Kathryn L; Sewell, Herb F; Shakib, Farouk; Ghaemmaghami, Amir M

2013-12-13

Allergen recognition by dendritic cells (DCs) is a key event in the allergic cascade leading to production of IgE antibodies. C-type lectins, such as the mannose receptor and DC-SIGN, were recently shown to play an important role in the uptake of the house dust mite glycoallergen Der p 1 by DCs. In addition to mannose receptor (MR) and DC-SIGN the high and low affinity IgE receptors, namely FcεRI and FcεRII (CD23), respectively, have been shown to be involved in allergen uptake and presentation by DCs. This study aims at understanding the extent to which IgE- and IgG-facilitated Der p 1 uptake by DCs influence T cell polarisation and in particular potential bias in favour of Th2. We have addressed this issue by using two chimaeric monoclonal antibodies produced in our laboratory and directed against a previously defined epitope on Der p 1, namely human IgE 2C7 and IgG1 2C7. Flow cytometry was used to establish the expression patterns of IgE (FcεRI and FcεRII) and IgG (FcγRI) receptors in relation to MR on DCs. The impact of FcεRI, FcεRII, FcγRI and mannose receptor mediated allergen uptake on Th1/Th2 cell differentiation was investigated using DC/T cell co-culture experiments. Myeloid DCs showed high levels of FcεRI and FcγRI expression, but low levels of CD23 and MR, and this has therefore enabled us to assess the role of IgE and IgG-facilitated allergen presentation in T cell polarisation with minimal interference by CD23 and MR. Our data demonstrate that DCs that have taken up Der p 1 via surface IgE support a Th2 response. However, no such effect was demonstrable via surface IgG. IgE bound to its high affinity receptor plays an important role in Der p 1 uptake and processing by peripheral blood DCs and in Th2 polarisation of T cells.

The decoy Fcγ receptor encoded by the cytomegalovirus UL119-UL118 gene has differential affinity to IgG proteins expressing different GM allotypes.

PubMed

Pandey, Janardan P; Namboodiri, Aryan M; Radwan, Faisal F; Nietert, Paul J

2015-08-01

Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus that has been implicated in many diseases. However, there is significant divergence between HCMV seroprevalence and the prevalence of HCMV-associated diseases, implying the presence of host genetic factors that might modulate immunity to this virus. HCMV deploys many sophisticated strategies to evade host immunosurveillance. One strategy involves encoding for proteins that have functional properties of the Fcγ receptor (FcγR). The aim of the present investigation was to determine whether the UL119-UL118-encoded recombinant FcγR ectodomain binds differentially to genetically disparate IgG1 proteins. Results show that mean absorbance values for binding of HCMV UL119-UL118-encoded Fcγ receptor to the immunoglobulin GM (γ marker) 1,17-expressing IgG1 were significantly higher than to the IgG1 expressing the allelic GM 3 allotype (0.225 vs. 0.151; p=0.039). These findings suggest possible mechanisms underlying the maintenance of immunoglobulin GM gene polymorphism and its putative role in the etiology of HCMV-associated diseases. Copyright © 2015 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

Fcgamma chain deficiency on hematopoietic cells ameliorates atherosclerosis in apoe-knockout mice by promoting Th2 responses

USDA-ARS?s Scientific Manuscript database

We have previously shown that oxLDL-immune complexes (oxLDL-IC) binding to Fcgamma receptors (Fc gamma R) expressed on human monocytes leads to induction of pro-inflammatory cytokines. Four classes of mouse Fc gamma Rs have been defined: Fc gamma RI, II, III, and IV. Functionally, Fc gamma Rs can be...

Albumin-based nanoparticles as methylprednisolone carriers for targeted delivery towards the neonatal Fc receptor in glomerular podocytes

PubMed Central

Wu, Lin; Chen, Mingyu; Mao, Huijuan; Wang, Ningning; Zhang, Bo; Zhao, Xiufen; Qian, Jun; Xing, Changying

2017-01-01

Glucocorticoids (GCs) are commonly used in the treatment of nephrotic syndrome. However, high doses and long periods of GC therapy can result in severe side effects. The present study aimed to selectively deliver albumin-methylprednisolone (MP) nanoparticles towards glomerular podocytes, which highly express the specific neonatal Fc receptor (FcRn) of albumin. Bovine serum albumin (BSA) was labeled with a fluorescent dye and linked with modified MP via an amide bond. The outcome nanoparticle named BSA633-MP showed a uniform size with a diameter of approximately 10 nm and contained 12 drug molecules on average. The nanoconjugates were found to be stable at pH 7.4 and acid-sensitive at pH 4.0, with approximately 72% release of the MP drug after 48 h of incubation. The nanoparticle demonstrated a 36-fold uptake in receptor-specific cellular delivery in the FcRn-expressing human podocytes compared to the uptake in the non-FcRn-expressing control cells. Co-localization further confirmed that uptake of the nanoconjugates involved receptor-mediated endocytosis followed by lysosome associated transportation. In vitro cellular experiments indicated that the BSA633-MP ameliorated puromycin aminonucleoside-induced podocyte apoptosis. Moreover, in vivo fluorescence molecular imaging showed that BSA633-MP was mainly accumulated in the liver and kidney after intravenous dosing for 24 h. Collectively, this study may provide an approach for the effective and safe therapy of nephrotic syndrome. PMID:28259932

Mutant RBL mast cells defective in Fc epsilon RI signaling and lipid raft biosynthesis are reconstituted by activated Rho-family GTPases.

PubMed

Field, K A; Apgar, J R; Hong-Geller, E; Siraganian, R P; Baird, B; Holowka, D

2000-10-01

Characterization of defects in a variant subline of RBL mast cells has revealed a biochemical event proximal to IgE receptor (Fc epsilon RI)-stimulated tyrosine phosphorylation that is required for multiple functional responses. This cell line, designated B6A4C1, is deficient in both Fc epsilon RI-mediated degranulation and biosynthesis of several lipid raft components. Agents that bypass receptor-mediated Ca(2+) influx stimulate strong degranulation responses in these variant cells. Cross-linking of IgE-Fc epsilon RI on these cells stimulates robust tyrosine phosphorylation but fails to mobilize a sustained Ca(2+) response. Fc epsilon RI-mediated inositol phosphate production is not detectable in these cells, and failure of adenosine receptors to mobilize Ca(2+) suggests a general deficiency in stimulated phospholipase C activity. Antigen stimulation of phospholipases A(2) and D is also defective. Infection of B6A4C1 cells with vaccinia virus constructs expressing constitutively active Rho family members Cdc42 and Rac restores antigen-stimulated degranulation, and active Cdc42 (but not active Rac) restores ganglioside and GPI expression. The results support the hypothesis that activation of Cdc42 and/or Rac is critical for Fc epsilon RI-mediated signaling that leads to Ca(2+) mobilization and degranulation. Furthermore, they suggest that Cdc42 plays an important role in the biosynthesis and expression of certain components of lipid rafts.

[Construction and expression of a eukaryotic expression vector containing human CR2-Fc fusion protein].

PubMed

Li, Xinxin; Wu, Zhihao; Zhang, Chuanfu; Jia, Leili; Song, Hongbin; Xu, Yuanyong

2014-01-01

To construct a eukaryotic expression vector containing human complement receptor 2 (CR2)-Fc and express the CR2-Fc fusion protein in Chinese hamster ovary (CHO) cells. The extracellular domain of human CR2 and IgG1 Fc were respectively amplified, ligated and inserted into the eukaryotic expression vector PCI-neo. After verified by restriction enzyme digestion and sequencing, the recombinant plasmid was transfected into CHO K1 cells. The ones with stable expression of the fusion protein were obtained by means of G418 selection. The expression of the CR2-Fc fusion protein was detected and confirmed by SDS-PAGE and Western blotting. Restriction enzyme digestion and sequencing demonstrated that the recombinant plasmid was valid. SDS-PAGE showed that relative molecular mass (Mr;) of the purified product was consistent with the expected value. Western blotting further proved the single band at the same position. We constructed the eukaryotic expression vector of CR2-Fc/PCI-neo successfully. The obtained fusion protein was active and can be used for the further study of the role in HIV control.

Fusion of the Fc part of human IgG1 to CD14 enhances its binding to gram-negative bacteria and mediates phagocytosis by Fc receptors of neutrophils.

PubMed

Vida, András; Bardoel, Bart; Milder, Fin; Majoros, László; Sümegi, Andrea; Bácsi, Attila; Vereb, György; van Kessel, Kok P M; van Strijp, Jos A G; Antal-Szalmás, Péter

2012-08-30

Microbial resistance to antimicrobial drugs is promoting a search for new antimicrobial agents that target highly conservative structures of pathogens. Human CD14 - a known pattern recognition receptor (PRR) which recognizes multiple ligands from different microbes might be a worthy candidate. The aim of our work was to create a CD14/Fc dimer protein and evaluate its whole bacteria binding and opsonizing capabilities. Fusion of CD14 with the fragment crystallisable (Fc) part of human IgG1 could not only lead to an artificial opsonin but the dimerization through the Fc part might also increase its affinity to different ligands. Human CD14 and the Fc part of human IgG1 was fused and expressed in HEK293 cells. A histidine tagged CD14 (CD14/His) was also expressed as control. Using flow cytometry we could prove that CD14/Fc bound to whole Gram-negative bacteria, especially to short lipopolysaccharide (Ra and Re) mutants, and weak interaction was observed between the fusion protein and Listeria monocytogenes. Other Gram-positive bacteria and fungi did not show any association with CD14/Fc. CD14/His showed about 50-times less potent binding to Gram-negative bacteria. CD14/Fc acted as an opsonin and enhanced phagocytosis of these bacteria by neutrophil granulocytes, monocyte-derived macrophages and dendritic cells. Internalization of bacteria was confirmed by trypan blue quenching and confocal microscopy. On neutrophils the Fc part of the fusion protein was recognized by Fc receptors (CD16, CD32), as determined by blocking experiments. CD14/Fc enhanced the killing of bacteria in an ex vivo whole blood assay. Our experiments confirm that PRR/Fc fusion proteins can give a boost to FcR dependent phagocytosis and killing provided the antimicrobial part binds efficiently to microbes. Copyright © 2012 Elsevier B.V. All rights reserved.

Syk-dependent tyrosine phosphorylation of 3BP2 is required for optimal FcRγ-mediated phagocytosis and chemokine expression in U937 cells.

PubMed

Chihara, Kazuyasu; Kato, Yuji; Yoshiki, Hatsumi; Takeuchi, Kenji; Fujieda, Shigeharu; Sada, Kiyonao

2017-09-13

The adaptor protein c-Abl SH3 domain binding protein-2 (3BP2) is tyrosine phosphorylated by Syk in response to cross-linking of antigen receptors, which in turn activates various immune responses. Recently, a study using the mouse model of cherubism, a dominant inherited disorder caused by mutations in the gene encoding 3BP2, showed that 3BP2 is involved in the regulation of phagocytosis mediated by Fc receptor for IgG (FcγR) in macrophages. However, the molecular mechanisms underlying 3BP2-mediated regulation of phagocytosis and the physiological relevance of 3BP2 tyrosine phosphorylation remains elusive. In this study, we established various gene knockout U937 cell lines using the CRISPR/Cas9 system and found that 3BP2 is rapidly tyrosine phosphorylated by Syk in response to cross-linking of FcγRI. Depletion of 3BP2 caused significant reduction in the Fc receptor γ chain (FcRγ)-mediated phagocytosis in addition to the FcγRI-mediated induction of chemokine mRNA for IL-8, CCL3L3 and CCL4L2. Syk-dependent tyrosine phosphorylation of 3BP2 was required for overcoming these defects. Finally, we found that the PH and SH2 domains play important roles on FcγRI-mediated tyrosine phosphorylation of 3BP2 in HL-60 cells. Taken together, these results indicate that Syk-dependent tyrosine phosphorylation of 3BP2 is required for optimal FcRγ-mediated phagocytosis and chemokine expression.

AhR mediates an anti-inflammatory feedback mechanism in human Langerhans cells involving FcεRI and IDO.

PubMed

Koch, S; Stroisch, T J; Vorac, J; Herrmann, N; Leib, N; Schnautz, S; Kirins, H; Förster, I; Weighardt, H; Bieber, T

2017-11-01

Aryl hydrocarbon receptor (AhR), an important regulator of immune responses, is activated by UVB irradiation in the skin. Langerhans cells (LC) in the epidermis of patients with atopic dermatitis (AD) carry the high-affinity receptor for IgE, FcεRI, and are crucially involved in the pathogenesis of AD by inducing inflammatory responses and regulating tolerogenic processes. We investigated AhR and AhR repressor (AhRR) expression and functional consequences of AhR activation in human ex vivo skin cells and in in vitro-generated LC. Epidermal cells from healthy skin were analyzed for their expression of AhR and AhRR. LC generated from CD34 + hematopoietic stem cells (CD34LC) were treated with the UV photoproduct and AhR ligand 6-formylindolo[3,2-b]carbazole (FICZ). Cell surface receptors, transcription factors, and the tolerogenic tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) were analyzed using flow cytometry and quantitative PCR. Epidermal LC and CD34LC express AhR and AhRR. AhR was also found in keratinocytes, which lack AhRR. AhR activation of LC by FICZ caused downregulation of FcεRI in CD34LC without affecting their maturation. AhR-mediated regulation of FcεRI did not involve any known transcription factors related to this receptor. Furthermore, we could show upregulation of IDO mediated by AhR engagement. Our study shows that AhR activation by FICZ reduces FcεRI and upregulates IDO expression in LC. This AhR-mediated anti-inflammatory feedback mechanism may dampen the allergen-induced inflammation in AD. © 2017 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

Neutralized adenovirus-immune complexes can mediate effective gene transfer via an Fc receptor-dependent infection pathway.

PubMed

Leopold, Philip L; Wendland, Rebecca L; Vincent, Theresa; Crystal, Ronald G

2006-10-01

Neutralization of adenovirus (Ad) by anti-Ad neutralizing antibodies in serum involves formation of Ad-immune complexes that prevent the virus from interacting with target cells. We hypothesized that Ad-immune complexes likely contain viable Ad vectors which, although no longer capable of gaining access to receptors on target cells, may be able to express transgenes in cells bearing Fc receptors for immunoglobulins, i.e., that antibody-based "neutralization" of Ad vectors may be circumvented by the Fc receptor pathway. To test this hypothesis, we expressed the Fcgamma receptor IIA (FcgammaR) in A549 lung epithelial cells or human dermal fibroblasts and evaluated gene transfer in the presence of human neutralizing anti-Ad serum. FcgammaR-expressing cells bound and internalized copious amounts of Ad, with a distinct population of internalized Ad trafficking to the nucleus. The dose-response curves for inhibition of gene transfer revealed that FcgammaR-expressing cells required a more-than-10-fold higher concentration of anti-Ad serum to achieve 50% inhibition of Ad-encoded beta-galactosidase expression compared with non-FcgammaR-expressing cells. The discrepancy between neutralization of Ad during infection of FcgammaR-expressing cells and neutralization of Ad during infection of non-FcgammaR-expressing cells occurred with either heat-inactivated or non-heat-inactivated sera, was blocked by addition of purified Fc domain protein, and did not require the cytoplasmic domain of FcgammaR, suggesting that immune complex internalization proceeded via endocytosis rather than phagocytosis. FcgammaR-mediated infection by Ad-immune complexes did not require expression of the coxsackie virus-Ad receptor (CAR) since similar data were obtained when CAR-deficient human dermal fibroblasts were engineered to express FcgammaR. However, interaction of the Ad penton base with cell surface integrins contributed to the difference in neutralization between FcgammaR-expressing and non-FcgammaR-expressing cells. The data indicate that complexes formed from Ad and anti-Ad neutralizing antibodies, while compromised with respect to infection of non-FcgammaR-expressing target cells, maintain the potential to transfer genes to FcgammaR-expressing cells, with consequent expression of the transgene. The formation of Ad-immune complexes that can target viable virus to antigen-presenting cells may account for the success of Ad-based vaccines administered in the presence of low levels of neutralizing anti-Ad antibody.

Expression of FcRn receptor in placental tissue and its relationship with IgG levels in term and preterm newborns.

PubMed

Lozano, Natalia A; Lozano, Alejandro; Marini, Vanina; Saranz, Ricardo J; Blumberg, Richard S; Baker, Kristi; Agresta, Maria F; Ponzio, Marina F

2018-05-10

IgG is the only antibody class, that is, actively transferred from the mother to the fetus across the placenta by an active, neonatal Fc receptor (FcRn) mediated process during pregnancy, conferring passive immunity and protection against infections to the newborn during the first months of life. Preterm infants may not receive sufficient titers of protective antibodies, as most of them are transferred only after the 34th week of gestation. Because of the great importance of this process, we investigated in a clinical setting the placental transmission of IgG antibodies in term and preterm newborns. This work was conducted in 85 woman and their newborns, divided into four groups according to their clinical gestational age (≤37 weeks were considered as preterm). Blood samples were collected from the mothers and their newborns' umbilical cords to analyze total serum IgG concentrations, and a subgroup of 32 placentas was analyzed by immunohistochemistry to quantify the expression of the FcRn receptor. Total IgG levels in both mothers and neonates increased significantly through the third trimester of gestation. Regarding the newborns, in all groups, IgG levels exceeded their mother's values by a ~2.4%. A higher expression of FcRn was detected in placentas from newborns at week 36 of gestation onwards. Our results obtained from clinical samples, were in line with previous descriptions in model systems and confirmed that the IgG transfer from maternal serum to the fetus is positively correlated with FcRn expression in placental tissue throughout gestation. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The production of KIR-Fc fusion proteins and their use in a multiplex HLA class I binding assay.

PubMed

Hilton, Hugo G; Moesta, Achim K; Guethlein, Lisbeth A; Blokhuis, Jeroen; Parham, Peter; Norman, Paul J

2015-10-01

Soluble recombinant proteins that comprise the extracellular part of a surface expressed receptor attached to the Fc region of an IgG antibody have facilitated the determination of ligand specificity for an array of immune system receptors. Among such receptors is the family of killer cell immunoglobulin-like receptors (KIR) that recognize HLA class I ligands. These receptors, expressed on natural killer (NK) cells and T cells, play important roles in both immune defense and placental development in early pregnancy. Here we describe a method for the production of two domain KIR-Fc fusion proteins using baculovirus infected insect cells. This method is more scalable than traditional mammalian cell expression systems and produces efficiently folded proteins that carry posttranslational modifications found in native KIR. We also describe a multiplex binding assay using the Luminex platform that determines the avidity and specificity of two domain KIR-Fc for a panel of microbeads, each coated with one of 97 HLA class I allotypes. This assay is simple to perform, and represents a major improvement over the assays used previously, which were limited in the number of KIR and HLA class I combinations that could be assayed at any one time. The results obtained from this assay can be used to predict the response of NK cell and T cells when their KIR recognize HLA class I. Copyright © 2015 Elsevier B.V. All rights reserved.

The effect of FcγRIIA and FcγRIIB on coronary artery lesion formation and intravenous immunoglobulin treatment responses in children with Kawasaki disease

PubMed Central

Chang, Ling-Sai; Lo, Mao-Hung; Li, Sung-Chou; Yang, Ming-Yu; Hsieh, Kai-Sheng; Kuo, Ho-Chang

2017-01-01

Previous research has found patients with the FcγRIIIB NA1 variant having increased risk of intravenous immunoglobulin (IVIG) resistance in Kawasaki disease (KD). Our previous studies revealed that elevated FcγRIIA expression correlated with the susceptibility of KD patients. We conducted this research to determine whether and how Fcγ receptors affect the susceptibility, IVIG treatment response, and coronary artery lesions (CAL) of KD patients. The activating FcγRIIA and inhibitory FcγRIIB methylation levels of seven patients with KD and four control subjects were examined using HumanMethylation27 BeadChip. We enrolled a total of 44 KD patients and 10 control subjects with fevers. We performed real-time RT-PCR to determine the FcγRIIA and FcγRIIB expression levels, as well as a luciferase assay of FcγRIIA. We found a considerable increase in methylation of both FcγRIIA and FcγRIIB in KD patients undergoing IVIG treatment. Promoter methylation of FcγRIIA inhibited reporter activity in K562 cells using luciferase assay. The FcγRIIB mRNA expression levels were not found to increase susceptibility, CAL formation, or IVIG resistance. FcγRIIA mRNA expression levels were significantly higher in IVIG-resistant patients than in those that responded to IVIG during the pre-treatment period. Furthermore, the FcγRIIA/IIB mRNA expression ratio was considerably higher in KD patients with CAL than in those without CAL. FcγRIIA and FcγRIIB both demonstrated increased methylation levels in KD patients that underwent IVIG treatment. FcγRIIA expression influenced the IVIG treatment response of KD patients. The FcγRIIA/IIB mRNA expression ratio was greater in KD patients with CAL formation. PMID:27893416

EMMPRIN (CD147) is a novel receptor for platelet GPVI and mediates platelet rolling via GPVI-EMMPRIN interaction.

PubMed

Seizer, Peter; Borst, Oliver; Langer, Harald F; Bültmann, Andreas; Münch, Götz; Herouy, Yared; Stellos, Konstantinos; Krämer, Björn; Bigalke, Boris; Büchele, Berthold; Bachem, Max G; Vestweber, Dietmar; Simmet, Thomas; Gawaz, Meinrad; May, Andreas E

2009-04-01

The Extracellular Matrix Metalloproteinase Inducer (EMMPRIN, CD147, basigin) is an immunoglobulin-like receptor expressed in various cell types. During cellular interactions homotypic EMMPRIN-EMMPRIN interactions are known to induce the synthesis of matrix metalloproteinases. Recently, we have identified EMMPRIN as a novel receptor on platelets. To our knowledge EMMPRIN has not been shown to serve as adhesion receptor, yet. Here we characterise platelet glycoprotein VI (GPVI) as a novel adhesion receptor for EMMPRIN. Human platelets were prestimulated with ADP and perfused over immobilised recombinant EMMPRIN-Fc or Fc-fragments under arterial shear conditions. ADP-stimulated platelets showed significantly enhanced rolling (but not enhanced firm adhesion) on immobilised EMMPRIN-Fc compared to Fc. Pretreatment of platelets with blocking mAbs anti-EMMPRIN or anti-GPVI leads to a significant reduction of rolling platelets on immobilised EMMPRIN-Fc, whereas pretreatment with blocking mAbs anti-p-selectin, anti-alpha4-integrin or anti-GPIIb/IIIa complex (20 microg/ml each) had no effect. Consistently, chinese hamster ovary (CHO) cells stably transfected with GPVI showed enhanced rolling (but not adhesion) on immobilised EMMPRIN-Fc in comparison to non-transfected CHO cells. Similarly, CHO cells stably transfected with EMMPRIN showed enhanced rolling on immobilised GPVI-Fc (or EMMPRIN-Fc) compared to non transfected CHO-cells. Finally, specific binding of EMMPRIN to GPVI was demonstrated by a modified ELISA and surface plasmon resonance technology with a dissociation constant of 88 nM. Platelet GPVI is a novel receptor for EMMPRIN and can mediate platelet rolling via GPVI-EMMPRIN interaction.

Effective therapy for a murine model of human anaplastic large-cell lymphoma with the anti-CD30 monoclonal antibody, HeFi-1, does not require activating Fc receptors

PubMed Central

Zhang, Meili; Yao, Zhengsheng; Zhang, Zhuo; Garmestani, Kayhan; Goldman, Carolyn K.; Ravetch, Jeffrey V.; Janik, John; Brechbiel, Martin W.; Waldmann, Thomas A.

2006-01-01

CD30 is a member of the tumor necrosis factor receptor family. Overexpression of CD30 on some neoplasms versus its limited expression on normal tissues makes this receptor a promising target for antibody-based therapy. Anaplastic large-cell lymphoma (ALCL) represents a heterogeneous group of aggressive non-Hodgkin lymphomas characterized by the strong expression of CD30. We investigated the therapeutic efficacy of HeFi-1, a mouse IgG1 monoclonal antibody, which recognizes the ligand-binding site on CD30, and humanized anti-Tac antibody (daclizumab), which recognizes CD25, in a murine model of human ALCL. The ALCL model was established by intravenous injection of karpas299 cells into nonobese diabetic/severe combined immuno-deficient (SCID/NOD) wild-type or SCID/NOD Fc receptor common γ chain–deficient (FcRγ–/–) mice. HeFi-1, given at a dose of 100 μg weekly for 4 weeks, significantly prolonged survival of the ALCL-bearing SCID/NOD wild-type and SCID/NOD FcRγ–/– mice (P < .01) as compared with the control groups. In vitro studies showed that HeFi-1 inhibited the proliferation of karpas299 cells, whereas daclizumab did not inhibit cell proliferation. We demonstrated that the expression of FcRγ on polymorphonuclear leukocytes and monocytes was not required for HeFi-1–mediated tumor growth inhibition in vivo, although it was required for daclizumab. PMID:16551968

Fcγ receptor I alpha chain (CD64) expression in macrophages is critical for the onset of meningitis by Escherichia coli K1.

PubMed

Mittal, Rahul; Sukumaran, Sunil K; Selvaraj, Suresh K; Wooster, David G; Babu, M Madan; Schreiber, Alan D; Verbeek, J Sjef; Prasadarao, Nemani V

2010-11-18

Neonatal meningitis due to Escherichia coli K1 is a serious illness with unchanged morbidity and mortality rates for the last few decades. The lack of a comprehensive understanding of the mechanisms involved in the development of meningitis contributes to this poor outcome. Here, we demonstrate that depletion of macrophages in newborn mice renders the animals resistant to E. coli K1 induced meningitis. The entry of E. coli K1 into macrophages requires the interaction of outer membrane protein A (OmpA) of E. coli K1 with the alpha chain of Fcγ receptor I (FcγRIa, CD64) for which IgG opsonization is not necessary. Overexpression of full-length but not C-terminal truncated FcγRIa in COS-1 cells permits E. coli K1 to enter the cells. Moreover, OmpA binding to FcγRIa prevents the recruitment of the γ-chain and induces a different pattern of tyrosine phosphorylation of macrophage proteins compared to IgG2a induced phosphorylation. Of note, FcγRIa(-/-) mice are resistant to E. coli infection due to accelerated clearance of bacteria from circulation, which in turn was the result of increased expression of CR3 on macrophages. Reintroduction of human FcγRIa in mouse FcγRIa(-/-) macrophages in vitro increased bacterial survival by suppressing the expression of CR3. Adoptive transfer of wild type macrophages into FcγRIa(-/-) mice restored susceptibility to E. coli infection. Together, these results show that the interaction of FcγRI alpha chain with OmpA plays a key role in the development of neonatal meningitis by E. coli K1.

A Regulatory Role for Src Homology 2 Domain–Containing Inositol 5′-Phosphatase (Ship) in Phagocytosis Mediated by Fcγ Receptors and Complement Receptor 3 (αMβ2; Cd11b/Cd18)

PubMed Central

Cox, Dianne; Dale, Benjamin M.; Kashiwada, Masaki; Helgason, Cheryl D.; Greenberg, Steven

2001-01-01

The Src homology 2 domain–containing inositol 5′-phosphatase (SHIP) is recruited to immunoreceptor tyrosine-based inhibition motif (ITIM)–containing proteins, thereby suppressing phosphatidylinositol 3-kinase (PI 3-kinase)–dependent pathways. The role of SHIP in phagocytosis, a PI 3-kinase–dependent pathway, is unknown. Overexpression of SHIP in macrophages led to an inhibition of phagocytosis mediated by receptors for the Fc portion of IgG (FcγRs). In contrast, macrophages expressing catalytically inactive SHIP or lacking SHIP expression demonstrated enhanced phagocytosis. To determine whether SHIP regulates phagocytosis mediated by receptors that are not known to recruit ITIMs, we determined the effect of SHIP expression on complement receptor 3 (CR3; CD11b/CD18; αMβ2)–dependent phagocytosis. Macrophages overexpressing SHIP demonstrated impaired CR3-mediated phagocytosis, whereas macrophages expressing catalytically inactive SHIP demonstrated enhanced phagocytosis. CR3-mediated phagocytosis in macrophages derived from SHIP−/− mice was up to 2.5 times as efficient as that observed in macrophages derived from littermate controls. SHIP was localized to FcγR- and CR3-containing phagocytic cups and was recruited to the cytoskeleton upon clustering of CR3. In a transfected COS cell model of activation-independent CR3-mediated phagocytosis, catalytically active but not inactive SHIP also inhibited phagocytosis. We conclude that PI 3-kinase(s) and SHIP regulate multiple forms of phagocytosis and that endogenous SHIP plays a role in modulating β2 integrin outside-in signaling. PMID:11136821

Impairment of neutrophil Fc gamma receptor mediated transmembrane signalling in active rheumatoid arthritis.

PubMed Central

Goulding, N J; Guyre, P M

1992-01-01

Neutrophil Fc gamma receptor (Fc gamma R) signalling responses were compared in healthy subjects, patients with definite rheumatoid arthritis (RA), ankylosing spondylitis, and osteoarthritis. The patients with A were subdivided into those with active synovitis and those with quiescent disease. Basal intracellular calcium ion concentrations in patients with inactive RA were significantly higher than in control subjects, which in turn were greater than in patients with active RA. Transient cytosolic calcium ion fluxes were observed after binding Fc gamma RII or Fc gamma RIII with specific monoclonal antibodies and cross linking with the F(ab')2 fragment of antimouse IgG. Response times were significantly faster for Fc gamma RII than for Fc gamma RIII. Peak concentrations of intracellular calcium ions after neutrophil stimulation were comparable for Fc gamma RII and RIII in healthy subjects. Neutrophils in patients with ankylosing spondylitis and osteoarthritis responded to Fc gamma R triggering, but in the group with active RA fluxes of calcium ions were severely depressed. Neutrophils isolated from patients with RA with quiescent disease showed exaggerated responses when compared with controls. Expression of all three Fc gamma R types on neutrophils from patients with active RA, as measured by monoclonal antibody binding, was comparable with control cells. Impairment of neutrophil Fc gamma R cytosolic signalling in active RA could reflect a receptor signalling defect with potential effects on Fc mediated functions, or a fundamental defect in calcium ion homeostasis within these cells. PMID:1535494

Deletion of the Fcγ Receptor IIb in Thymic Stromal Lymphopoietin Transgenic Mice Aggravates Membranoproliferative Glomerulonephritis

PubMed Central

Mühlfeld, Anja S.; Segerer, Stephan; Hudkins, Kelly; Carling, Matthew D.; Wen, Min; Farr, Andrew G.; Ravetch, Jeffrey V.; Alpers, Charles E.

2003-01-01

Engagement of immunoglobulin-binding receptors (FcγR) on leukocytes and other cell types is one means by which immunoglobulins and immune complexes activate effector cells. One of these FcγRs, FcγRIIb, is thought to contribute to protection from autoimmune disease by down-regulation of B-cell responsiveness and myeloid cell activation. We assessed the role of FcγRIIb in a mouse model of cryoglobulin-associated membranoproliferative glomerulonephritis induced by overexpression of thymic stromal lymphopoietin (TSLP). TSLP transgenic mice were crossbred with animals deficient for FcγRIIb on the same genetic background (C57BL/6). Renal pathology was assessed in female and male animals (wild-type, FcγRIIb−/−, TSLP transgenic, and combined TSLP transgenic/FcγRIIb−/− mice) after 50 and 120 days, respectively. FcγRIIb−/− mice had no significant renal pathology, whereas overexpression of TSLP induced a membranoproliferative glomerulonephritis, as previously established. TSLP transgenic FcγRIIb−/− mice appeared sick with increased mortality. Kidney function was significantly impaired in male mice corresponding to aggravated glomerular pathology with increases in glomerular matrix and cellularity. This resulted from both a large influx of infiltrating macrophages and increased cellular proliferation. These results emphasize the important role of FcγRIIb in regulating immune responses and suggest that modulation of Fcγ receptor activation or expression may be a useful therapeutic approach for treating glomerular diseases. PMID:12937154

IgG receptor FcγRIIB plays a key role in obesity-induced hypertension.

PubMed

Sundgren, Nathan C; Vongpatanasin, Wanpen; Boggan, Brigid-Meghan D; Tanigaki, Keiji; Yuhanna, Ivan S; Chambliss, Ken L; Mineo, Chieko; Shaul, Philip W

2015-02-01

There is a well-recognized association between obesity, inflammation, and hypertension. Why obesity causes hypertension is poorly understood. We previously demonstrated using a C-reactive protein (CRP) transgenic mouse that CRP induces hypertension that is related to NO deficiency. Our prior work in cultured endothelial cells identified the Fcγ receptor IIB (FcγRIIB) as the receptor for CRP whereby it antagonizes endothelial NO synthase. Recognizing known associations between CRP and obesity and hypertension in humans, in the present study we tested the hypothesis that FcγRIIB plays a role in obesity-induced hypertension in mice. Using radiotelemetry, we first demonstrated that the hypertension observed in transgenic mouse-CRP is mediated by the receptor, indicating that FcγRIIB is capable of modifying blood pressure. We then discovered in a model of diet-induced obesity yielding equal adiposity in all study groups that whereas FcγRIIB(+/+) mice developed obesity-induced hypertension, FcγRIIB(-/-) mice were fully protected. Levels of CRP, the related pentraxin serum amyloid P component which is the CRP-equivalent in mice, and total IgG were unaltered by diet-induced obesity; FcγRIIB expression in endothelium was also unchanged. However, whereas IgG isolated from chow-fed mice had no effect, IgG from high-fat diet-fed mice inhibited endothelial NO synthase in cultured endothelial cells, and this was an FcγRIIB-dependent process. Thus, we have identified a novel role for FcγRIIB in the pathogenesis of obesity-induced hypertension, independent of processes regulating adiposity, and it may entail an IgG-induced attenuation of endothelial NO synthase function. Approaches targeting FcγRIIB may potentially offer new means to treat hypertension in obese individuals. © 2014 American Heart Association, Inc.

IgG Receptor FcγRIIB Plays a Key Role in Obesity-Induced Hypertension

PubMed Central

Sundgren, Nathan C.; Vongpatanasin, Wanpen; Boggan, Brigid-Meghan D.; Tanigaki, Keiji; Yuhanna, Ivan S.; Chambliss, Ken L.; Mineo, Chieko; Shaul, Philip W.

2015-01-01

There is a well-recognized association between obesity, inflammation, and hypertension. Why obesity causes hypertension is poorly understood. We previously demonstrated using a C-reactive protein (CRP) transgenic mouse that CRP induces hypertension that is related to NO deficiency. Our prior work in cultured endothelial cells identified the Fcγ receptor IIB (FcγRIIB) as the receptor for CRP whereby it antagonizes endothelial NO synthase. Recognizing known associations between CRP and obesity and hypertension in humans, in the present study we tested the hypothesis that FcγRIIB plays a role in obesity-induced hypertension in mice. Using radiotelemetry, we first demonstrated that the hypertension observed in transgenic mouse-CRP is mediated by the receptor, indicating that FcγRIIB is capable of modifying blood pressure. We then discovered in a model of diet-induced obesity yielding equal adiposity in all study groups that whereas FcγRIIB+/+ mice developed obesity-induced hypertension, FcγRIIB−/− mice were fully protected. Levels of CRP, the related pentraxin serum amyloid P component which is the CRP-equivalent in mice, and total IgG were unaltered by diet-induced obesity; FcγRIIB expression in endothelium was also unchanged. However, whereas IgG isolated from chow-fed mice had no effect, IgG from high-fat diet–fed mice inhibited endothelial NO synthase in cultured endothelial cells, and this was an FcγRIIB-dependent process. Thus, we have identified a novel role for FcγRIIB in the pathogenesis of obesity-induced hypertension, independent of processes regulating adiposity, and it may entail an IgG-induced attenuation of endothelial NO synthase function. Approaches targeting FcγRIIB may potentially offer new means to treat hypertension in obese individuals. PMID:25368023

Hydrodynamic delivery of plasmid DNA encoding human FcγR-Ig dimers blocks immune-complex mediated inflammation in mice.

PubMed

Shashidharamurthy, R; Machiah, D; Bozeman, E N; Srivatsan, S; Patel, J; Cho, A; Jacob, J; Selvaraj, P

2012-09-01

Therapeutic use and function of recombinant molecules can be studied by the expression of foreign genes in mice. In this study, we have expressed human Fcγ receptor-Ig fusion molecules (FcγR-Igs) in mice by administering FcγR-Ig plasmid DNAs hydrodynamically and compared their effectiveness with purified molecules in blocking immune-complex (IC)-mediated inflammation in mice. The concentration of hydrodynamically expressed FcγR-Igs (CD16A(F)-Ig, CD32A(R)-Ig and CD32A(H)-Ig) reached a maximum of 130 μg ml(-1) of blood within 24 h after plasmid DNA administration. The in vivo half-life of FcγR-Igs was found to be 9-16 days and western blot analysis showed that the FcγR-Igs were expressed as a homodimer. The hydrodynamically expressed FcγR-Igs blocked 50-80% of IC-mediated inflammation up to 3 days in a reverse passive Arthus reaction model. Comparative analysis with purified molecules showed that hydrodynamically expressed FcγR-Igs are more efficient than purified molecules in blocking IC-mediated inflammation and had a higher half-life. In summary, these results suggest that the administration of a plasmid vector with the FcγR-Ig gene can be used to study the consequences of blocking IC binding to FcγRs during the development of inflammatory diseases. This approach may have potential therapeutic value in treating IC-mediated inflammatory autoimmune diseases such as lupus, arthritis and autoimmune vasculitis.

IgA Fc receptors.

PubMed

Monteiro, Renato C; Van De Winkel, Jan G J

2003-01-01

The IgA receptor family comprises a number of surface receptors including the polymeric Ig receptor involved in epithelial transport of IgA/IgM, the myeloid specific IgA Fc receptor (FcalphaRI or CD89), the Fcalpha/muR, and at least two alternative IgA receptors. These are the asialoglycoprotein receptor and the transferrin receptor, which have been implicated in IgA catabolism, and tissue IgA deposition. In this review we focus on the biology of FcalphaRI (CD89). FcalphaRI is expressed on neutrophils, eosinophils, monocytes/macrophages, dendritic cells, and Kupffer cells. This receptor represents a heterogeneously glycosylated transmembrane protein that binds both IgA subclasses with low affinity. A single gene encoding FcalphaRI has been isolated, which is located within the leukocyte receptor cluster on chromosome 19. The FcalphaRI alpha chain lacks canonical signal transduction domains but can associate with the FcR gamma-chain that bears an activation motif (ITAM) in the cytoplasmic domain, allowing activatory functions. FcalphaRI expressed alone mediates endocytosis and recyling of IgA. No FcalphaRI homologue has been defined in the mouse, and progress in defining the in vivo role of FcalphaRI has been made using human FcalphaRI transgenic (Tg) mice. FcalphaRI-Tg mice demonstrated FcalphaRI expression on Kupffer cells and so defined a key role for the receptor in mucosal defense. The receptor functions as a second line of antibacterial defense involving serum IgA rather than secretory IgA. Studies in FcalphaRI-Tg mice, furthermore, defined an essential role for soluble FcalphaRI in the development of IgA nephropathy by formation of circulating IgA-FcalphaRI complexes. Finally, recent work points out a role for human IgA in treatment of infectious and neoplastic diseases.

Mycoplasma infection of cell lines can simulate the expression of Fc receptors by binding of the carbohydrate moiety of antibodies.

PubMed

Lemke, H; Krausse, R; Lorenzen, J; Havsteen, B

1985-05-01

During the production of Fc receptor (FcR)-bearing hybridomas it was observed with a particular monoclonal anti-sheep red blood cell antibody (anti-SRBC 1/5, IgG1) that the contamination with Mycoplasma arginini of in vitro cultured cell lines leads to an apparent FcR activity. This property did not correspond with the serological typing since other antibodies of the same isotype could not support FcR rosette formation. Another mycoplasma strain M. orale lacked this property. Analysis of the binding reaction revealed that M. arginini contains a lectin which binds the carbohydrate moiety of the anti-SRBC 1/5 antibody, i.e. anti-SRBC 1/5 synthesized under the influence of tunicamycin or deglycosylated by NaIO4 oxidation did not support rosette formation. These data suggest that binding of antibodies to certain mycoplasma strains may be a pathogenic factor during mycoplasma infections by masking the microorganisms with the host's own defense molecules. The experiments with M. arginini-infected cell lines gain immunological importance since we obtained identical results with staphylococcal protein A, as another bacteriological FcR, and cell lines expressing intrinsic membrane FcR. Although it is an open question whether the glycoconjugates are directly bound by the FcR or else by influencing the three-dimensional structure of the antibodies, it seems possible that FcR in general may be lectins.

Absence of Fc epsilonRI alpha chain results in upregulation of Fc gammaRIII-dependent mast cell degranulation and anaphylaxis. Evidence of competition between Fc epsilonRI and Fc gammaRIII for limiting amounts of FcR beta and gamma chains.

PubMed Central

Dombrowicz, D; Flamand, V; Miyajima, I; Ravetch, J V; Galli, S J; Kinet, J P

1997-01-01

In mouse mast cells, both Fc epsilonRI and Fc gammaRIII are alpha beta gamma2 tetrameric complexes in which different alpha chains confer IgE or IgG ligand recognition while the signaling FcR beta and gamma chains are identical. We used primarily noninvasive techniques (changes in body temperature, dye extravasation) to assess systemic anaphylactic responses in nonanesthetized wild-type, Fc epsilonRI alpha chain -/- and FcR gamma chain -/- mice. We confirm that systemic anaphylaxis in mice can be mediated largely through IgG1 and Fc gammaRIII and we provide direct evidence that these responses reflect activation of Fc gammaRIII rather than Fc gammaRI. Furthermore, we show that Fc gammaRIII-dependent responses are more intense in normal than in congenic mast cell-deficient KitW/KitW-v mice, indicating that Fc gammaRIII responses have mast cell-dependent and -independent components. Finally, we demonstrate that the upregulation of cell surface expression of Fc gammaRIII seen in Fc epsilonRI alpha chain -/- mice corresponds to an increased association of Fc gammaRIII alpha chains with FcR beta and gamma chains and is associated with enhanced Fc gammaRIII-dependent mast cell degranulation and systemic anaphylactic responses. Therefore, the phenotype of the Fc epsilonRI alpha chain -/- mice suggests that expression of Fc epsilonRI and Fc gammaRIII is limited by availability of the FcR beta and gamma chains and that, in normal mice, changes in the expression of one receptor (Fc epsilonRI) may influence the expression of functional responses dependent on the other (Fc gammaRIII). PMID:9062349

BINDING OF SOLUBLE IMMUNE COMPLEXES TO HUMAN LYMPHOBLASTOID CELLS

PubMed Central

Theofilopoulos, Argyrios N.; Dixon, Frank J.; Bokisch, Viktor A.

1974-01-01

In the present work we studied the expression of membrane-bound Ig (MBIg) as well as receptors for IgG Fc and complement on nine human lymphoblastoid cell lines. When MBIg and receptors for IgG Fc were compared, four categories of cell lines could be distinguished: (a) cell lines having both MBIg and receptors for IgG Fc, (b) cell lines having MBIg but lacking receptors for IgG Fc, (c) cell lines lacking MBIg but having receptors for IgG Fc, and (d) cell lines lacking both MBIg and receptors for IgG Fc. Two types of receptors for complement could be detected on the cell lines studied, one for C3-C3b and one for C3d. When sensitized red cells carrying C3b or C3d were used for rosette tests, three categories of cell lines could be distinguished: (a) cell lines having receptors for C3b and C3d, (b) cell lines having receptors only for C3d and (c) cell lines lacking both receptors. However, when a more sensitive immunofluorescent method was used instead of the rosette technique, it was found that cell lines unable to form rosettes with EAC1423bhu were able to bind soluble C3 or C3b which indicated the presence of these receptors on the cell surface. Inhibition experiments showed that receptors for C3-C3b and receptors for C3d are distinct and that receptors for C3-C3b and C3d are different from receptors for IgG Fc. A cell line (Raji) without MBIg but with receptors for IgG Fc, C3-C3b, and C3d was selected for use in studying the binding mechanism of soluble immune complexes to cell surface membrane. Aggregated human gamma globulin was used in place of immune complexes. Immune complexes containing complement bind to Raji cells only via receptors for complement, namely receptors for C3-C3b and C3d. Binding of immune complexes containing complement to cells is much greater than that of complexes without complement. Immune complexes bound to cells via receptors for complement can be partially released from the cell surface by addition of normal human serum as well as isolated human C3 or C3b. We postulate that such release is due to competition of immune complex bound C3b and free C3 or C3b for the receptors on Raji cells. PMID:4139225

Multiple elements of the allergic arm of the immune response modulate autoimmune demyelination

PubMed Central

Pedotti, Rosetta; DeVoss, Jason J.; Youssef, Sawsan; Mitchell, Dennis; Wedemeyer, Jochen; Madanat, Rami; Garren, Hideki; Fontoura, Paulo; Tsai, Mindy; Galli, Stephen J.; Sobel, Raymond A.; Steinman, Lawrence

2003-01-01

Analysis of mRNA from multiple sclerosis lesions revealed increased amounts of transcripts for several genes encoding molecules traditionally associated with allergic responses, including prostaglandin D synthase, histamine receptor type 1 (H1R), platelet activating factor receptor, Ig Fc ɛ receptor 1 (FcɛRI), and tryptase. We now demonstrate that, in the animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), mediated by T helper 1 (Th1) T cells, histamine receptor 1 and 2 (H1R and H2R) are present on inflammatory cells in brain lesions. Th1 cells reactive to myelin proteolipid protein expressed more H1R and less H2R than Th2 cells. Pyrilamine, an H1R antagonist, blocked EAE, and the platelet activating factor receptor antagonist CV6209 reduced the severity of EAE. EAE severity was also decreased in mice with disruption of the genes encoding Ig FcγRIII or both FcγRIII and FcɛRI. Prostaglandin D synthase and tryptase transcripts were elevated in EAE brain. Taken together, these data reveal extensive involvement of elements of the immune response associated with allergy in autoimmune demyelination. The pathogenesis of demyelination must now be viewed as encompassing elements of both Th1 responses and “allergic” responses. PMID:12576552

Affinity of C-Reactive Protein toward FcγRI Is Strongly Enhanced by the γ-Chain

PubMed Central

Röcker, Carlheinz; Manolov, Dimitar E.; Kuzmenkina, Elza V.; Tron, Kyrylo; Slatosch, Holger; Torzewski, Jan; Nienhaus, G. Ulrich

2007-01-01

C-reactive protein (CRP), the prototype human acute phase protein, is widely regarded as a key player in cardiovascular disease, but the identity of its cellular receptor is still under debate. By using ultrasensitive confocal imaging analysis, we have studied CRP binding to transfected COS-7 cells expressing the high-affinity IgG receptor FcγRI. Here we show that CRP binds to FcγRI on intact cells, with a kd of 10 ± 3 μmol/L. Transfection of COS-7 cells with a plasmid coding for both FcγRI and its functional counterpart, the γ-chain, markedly increases CRP affinity to FcγRI, resulting in a kd of 0.35 ± 0.10 μmol/L. The affinity increase results from an ∼30-fold enhanced association rate coefficient. The pronounced enhancement of affinity by the γ-chain suggests its crucial involvement in the CRP receptor interaction, possibly by mediating interactions between the transmembrane moieties of the receptors. Dissociation of CRP from the cell surfaces cannot be detected throughout the time course of several hours and is thus extremely slow. Considering the pentameric structure of CRP, this result indicates that multivalent binding and receptor clustering are crucially involved in the interaction of CRP with nucleated cells. PMID:17255341

Soluble glycoprotein VI dimer inhibits platelet adhesion and aggregation to the injured vessel wall in vivo.

PubMed

Massberg, Steffen; Konrad, Ildiko; Bültmann, Andreas; Schulz, Christian; Münch, Götz; Peluso, Mario; Lorenz, Michael; Schneider, Simon; Besta, Felicitas; Müller, Iris; Hu, Bin; Langer, Harald; Kremmer, Elisabeth; Rudelius, Martina; Heinzmann, Ulrich; Ungerer, Martin; Gawaz, Meinrad

2004-02-01

Platelet-collagen interactions play a fundamental role in the process of arterial thrombosis. The major platelet collagen receptor is the glycoprotein VI (GPVI). Here, we determined the effects of a soluble dimeric form of GPVI on platelet adhesion in vitro and in vivo. We fused the extracellular domain of GPVI with the human immunoglobulin Fc domain. The soluble dimeric form of GPVI (GPVI-Fc) specifically bound to immobilized collagen. Binding of GPVI-Fc to collagen was inhibited competitively by soluble GPVI-Fc, but not control Fc lacking the external GPVI domain. GPVI-Fc inhibited the adhesion of CHO cells that stably express human GPVI and of platelets on collagen and attenuated thrombus formation under shear conditions in vitro. To test the effects of GPVI-Fc in vivo, arterial thrombosis was induced in the mouse carotid artery, and platelet-vessel wall interactions were visualized by intravital fluorescence microscopy. Infusion of GPVI-Fc but not of control Fc virtually abolished stable arrest and aggregation of platelets following vascular injury. Importantly, GPVI-Fc but not control Fc, was detected at areas of vascular injury. These findings further substantiate the critical role of the collagen receptor GPVI in the initiation of thrombus formation at sites of vascular injury and identify soluble GPVI as a promising antithrombotic strategy.

Chimeric antigen receptor T cells targeting Fc μ receptor selectively eliminate CLL cells while sparing healthy B cells.

PubMed

Faitschuk, Elena; Hombach, Andreas A; Frenzel, Lukas P; Wendtner, Clemens-Martin; Abken, Hinrich

2016-09-29

Adoptive cell therapy of chronic lymphocytic leukemia (CLL) with chimeric antigen receptor (CAR)-modified T cells targeting CD19 induced lasting remission of this refractory disease in a number of patients. However, the treatment is associated with prolonged "on-target off-tumor" toxicities due to the targeted elimination of healthy B cells demanding more selectivity in targeting CLL cells. We identified the immunoglobulin M Fc receptor (FcμR), also known as the Fas apoptotic inhibitory molecule-3 or TOSO, as a target for a more selective treatment of CLL by CAR T cells. FcμR is highly and consistently expressed by CLL cells; only minor levels are detected on healthy B cells or other hematopoietic cells. T cells with a CAR specific for FcμR efficiently responded toward CLL cells, released a panel of proinflammatory cytokines and lytic factors, like soluble FasL and granzyme B, and eliminated the leukemic cells. In contrast to CD19 CAR T cells, anti-FcμR CAR T cells did not attack healthy B cells. T cells with anti-FcμR CAR delayed outgrowth of Mec-1-induced leukemia in a xenograft mouse model. T cells from CLL patients in various stages of the disease, modified by the anti-FcμR CAR, purged their autologous CLL cells in vitro without reducing the number of healthy B cells, which is the case with anti-CD19 CAR T cells. Compared with the currently used therapies, the data strongly imply a superior therapeutic index of anti-FcμR CAR T cells for the treatment of CLL. © 2016 by The American Society of Hematology.

Neonatal Fc receptor expression in dendritic cells mediates protective immunity against colorectal cancer.

PubMed

Baker, Kristi; Rath, Timo; Flak, Magdalena B; Arthur, Janelle C; Chen, Zhangguo; Glickman, Jonathan N; Zlobec, Inti; Karamitopoulou, Eva; Stachler, Matthew D; Odze, Robert D; Lencer, Wayne I; Jobin, Christian; Blumberg, Richard S

2013-12-12

Cancers arising in mucosal tissues account for a disproportionately large fraction of malignancies. Immunoglobulin G (IgG) and the neonatal Fc receptor for IgG (FcRn) have an important function in the mucosal immune system that we have now shown extends to the induction of CD8(+) T cell-mediated antitumor immunity. We demonstrate that FcRn within dendritic cells (DCs) was critical for homeostatic activation of mucosal CD8(+) T cells that drove protection against the development of colorectal cancers and lung metastases. FcRn-mediated tumor protection was driven by DCs activation of endogenous tumor-reactive CD8(+) T cells via the cross-presentation of IgG complexed antigens (IgG IC), as well as the induction of cytotoxicity-promoting cytokine secretion, particularly interleukin-12, both of which were independently triggered by the FcRn-IgG IC interaction in murine and human DCs. FcRn thus has a primary role within mucosal tissues in activating local immune responses that are critical for priming efficient anti-tumor immunosurveillance. Copyright © 2013 Elsevier Inc. All rights reserved.

Surface receptors on human haematopoietic cell lines.

PubMed Central

Huber, C; Sundström, C; Nilsson, K; Wigzell, H

1976-01-01

The expression of complement receptors, of Fc receptors, of SRBC receptors and of S-Ig was investigated on human haematopoietic cell lines of proved malignant derivation. According to their origin and to a panel of phenotypic markers these lines have been classified into lymphoma lines, myeloma lines and leukemia lines. Results were compared with those obtained on non-malignant EBV carrying lymphoblastoid cell lines (LCL). Among the lymphoid cell lines the LCL showed a pattern of B-lymphocyte surface markers, i.e. surface immunoglobulins, C3 receptors but low density of Fc receptors. The non-Burkitt lymphoma lines bore in varying degree these B-lymphocyte markers. The lines U-698 M and DG-75 were exceptional in having only surface immunoglobulin. The Burkitt lymphoma lines had all B-lymphocyte markers. The myeloma lines differed from the lymphoid lines in lacking C3 and Fc receptors and showed only trace amounts of surface immunoglobulins. In contrast to lymphoid and myeloma lines, the leukaemia lines were completely lacking surface immunoglobulins, but showed C3 and Fc receptors in variable densities. On line, the ALL derived line MOLT-3 showed the capacity to spontaneous rosette formation with SRBC. The findings that LCL presented a homogeneous pattern of B-lymphocyte surface markers may be of value in order to discriminate between these lines and lines derived from haematopoietic malignancies other than Burkitt lymphomas. PMID:963908

A novel 1,2-benzenediamine derivative FC-99 suppresses TLR3 expression and ameliorates disease symptoms in a mouse model of sepsis.

PubMed

Gong, Wei; Hu, Erling; Dou, Huan; Song, Yuxian; Yang, Liu; Ji, Jianjian; Li, Erguang; Tan, Renxiang; Hou, Yayi

2014-11-01

Sepsis is a clinical condition characterized by overwhelming systemic inflammation with high mortality rate and high prevalence, but effective treatment is still lacking. Toll-like receptor 3 (TLR3) is an endogenous sensor, thought to regulate the amplification of immune response during sepsis. Modulators of TLR3 have an advantage in the treatment of sepsis. Here, we aimed to explore the mechanism of a monosubstituted 1,2-benzenediamine derivative FC-99 {N(1) -[(4-methoxy)methyl]-4-methyl-1,2-benzenediamine}on modulating TLR3 expression and its therapeutic potential on mouse model of sepsis. Cells were pretreated with FC-99 followed by poly(I:C) or IFN-α stimulation; TLR3 and other indicators were assayed. Female C57BL/6 mice were subjected to sham or caecal ligation puncture (CLP) surgery after i.p. injection of vehicle or FC-99; serum and tissues were collected for further experiments. FC-99 suppressed inflammatory response induced by poly(I:C) with no effect on cell viability or uptake of poly(I:C). FC-99 also inhibited TLR3 expression induced by not only poly(I:C) but also by exogenous IFN-α. This inhibition of FC-99 was related to the poly(I:C)-evoked IRF3/IFN-α/JAK/STAT1 signalling pathway. In CLP-induced model of sepsis, FC-99 administration decreased mice mortality and serum levels of inflammatory factors, attenuated multiple organ dysfunction and enhanced bacterial clearance. Accordingly, systemic and local expression of TLR3 was reduced by FC-99 in vivo. FC-99 reversed TLR3 expression and ameliorate CLP-induced sepsis in mice. Thus, FC-99 will be a potential therapeutic candidate for sepsis. © 2014 The British Pharmacological Society.

FcγRIIa ligation induces platelet hypersensitivity to thrombotic stimuli.

PubMed

Berlacher, Mark D; Vieth, Joshua A; Heflin, Brittany C; Gay, Steven R; Antczak, Adam J; Tasma, Brian E; Boardman, Holly J; Singh, Navinderjit; Montel, Angela H; Kahaleh, M Bashar; Worth, Randall G

2013-01-01

Platelets are known for their important role in hemostasis, however their significance in other functions, including inflammation and infection, are becoming more apparent. Patients with systemic lupus erythematosus (SLE) are known to have circulating IgG complexes in their blood and are highly susceptible to thrombotic events. Because platelets express a single receptor for IgG, we tested the hypothesis that ligation of this receptor (FcγRIIa) induces platelet hypersensitivity to thrombotic stimuli. Platelets from SLE patients were considerably more sensitive to thrombin compared to healthy volunteers, and this correlated with elevated levels of surface IgG on SLE platelets. To test whether FcγRIIa ligation stimulated thrombin hypersensitivity, platelets from healthy volunteers were incubated with buffer or heat-aggregated IgG, then stimulated with increasing concentrations of thrombin. Interestingly, heat-aggregated IgG-stimulated platelets, but not buffer-treated platelets, were hypersensitive to thrombin, and hypersensitivity was blocked by an anti-FcγRIIa monoclonal antibody (mAb). Thrombin hypersensitivity was not due to changes in thrombin receptor expression (GPIbα or PAR1) but is dependent on activation of shared signaling molecules. These observations suggest that ligation of platelet FcγRIIa by IgG complexes induces a hypersensitive state whereby small changes in thrombotic stimuli may result in platelet activation and subsequent vascular complications such as transient ischemic attacks or stroke. Copyright © 2013 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

In vivo activation of equine eosinophils and neutrophils by experimental Strongylus vulgaris infections.

PubMed

Dennis, V A; Klei, T R; Chapman, M R; Jeffers, G W

1988-12-01

Eosinophils and neutrophils from ponies with Strongylus vulgaris-induced eosinophilia (eosinophilic ponies; activated eosinophils and neutrophils) were assayed in vitro for chemotactic and chemokinetic responses to zymosan-activated serum (ZAS) using the filter system in Boyden chambers, for Fc and complement (C) receptors using the EA and EAC-rosette assays, respectively, and for phagocytic and bactericidal activities using opsonized Escherichia coli and the acridine orange method. The responses of activated eosinophils and neutrophils in the above assays were compared with those of eosinophils and neutrophils from S. vulgaris-naive ponies without eosinophilia (noneosinophilic ponies; nonactivated eosinophils and neutrophils). Differences in cell density following centrifugation in a continuous Percoll gradient were used to further characterize the heterogeneity of activated eosinophils and neutrophils. Activated and nonactivated eosinophils demonstrated similar chemotactic responses to ZAS while activated and nonactivated neutrophils demonstrated similar chemokinetic responses to ZAS. A higher percentage of activated eosinophils and neutrophils expressed Fc and C receptors compared with nonactivated cells (P less than 0.05). Generally, higher percentages of eosinophils and neutrophils expressed C than Fc receptors. However, the percentage of neutrophils with both receptors was higher than that of eosinophils. Phagocytosis and killing of E. coli by either type of eosinophil were not consistently observed. Both activated and nonactivated neutrophils phagocytized E. coli and significant differences between the two cell types were not observed. The bacterial activity, however, of activated neutrophils was significantly greater than that obtained using nonactivated neutrophils (P less than 0.05). Activated eosinophils and neutrophils were both separated into two distinct fractions based on differences in cell densities. A higher percentage of band 2 eosinophils (density of 1.106) expressed C receptors than did band 1 eosinophils (density of 1.049) (P less than 0.05). A higher percentage of band 1 neutrophils (density of 1.072) expressed both Fc and C receptors and these neutrophils were more phagocytic and bactericidal than were band 2 neutrophils (density of 1.082) (P less than 0.05). These data suggest that equine eosinophils and neutrophils are activated by chronic S. vulgaris infections.

Binding of phycoerythrin and its conjugates to murine low affinity receptors for immunoglobulin G.

PubMed

Takizawa, F; Kinet, J P; Adamczewski, M

1993-06-18

Conjugates of R-phycoerythrin are widely used for immunohistochemistry, especially for two-color flow cytometry. Their use is however limited by their apparent tendency to bind non-specifically. Using cells transfected with cDNAs for the murine low affinity receptors for immunoglobulin G (Fc gamma RII and -III) and cells naturally expressing these receptors, we demonstrate that R-phycoerythrin and its conjugates bind specifically and inhibitably to Fc gamma RII and -III. Immunofluorescence stainings of cells bearing these receptors, such as macrophages, monocytes, neutrophils, mast cells, subsets of T cells, and natural killer cells, may therefore not reflect the binding of antibody to antigen, but rather the binding of R-phycoerythrin to the receptors.

Plant-expressed Fc-fusion protein tetravalent dengue vaccine with inherent adjuvant properties.

PubMed

Kim, Mi Young; Copland, Alastair; Nayak, Kaustuv; Chandele, Anmol; Ahmed, Muhammad S; Zhang, Qibo; Diogo, Gil R; Paul, Matthew J; Hofmann, Sven; Yang, Moon-Sik; Jang, Yong-Suk; Ma, Julian K-C; Reljic, Rajko

2017-12-09

Dengue is a major global disease requiring improved treatment and prevention strategies. The recently licensed Sanofi Pasteur Dengvaxia vaccine does not protect children under the age of nine, and additional vaccine strategies are thus needed to halt this expanding global epidemic. Here, we employed a molecular engineering approach and plant expression to produce a humanized and highly immunogenic poly-immunoglobulin G scaffold (PIGS) fused to the consensus dengue envelope protein III domain (cEDIII). The immunogenicity of this IgG Fc receptor-targeted vaccine candidate was demonstrated in transgenic mice expressing human FcγRI/CD64, by induction of neutralizing antibodies and evidence of cell-mediated immunity. Furthermore, these molecules were able to prime immune cells from human adenoid/tonsillar tissue ex vivo as evidenced by antigen-specific CD4 + and CD8 + T-cell proliferation, IFN-γ and antibody production. The purified polymeric fraction of dengue PIGS (D-PIGS) induced stronger immune activation than the monomeric form, suggesting a more efficient interaction with the low-affinity Fcγ receptors on antigen-presenting cells. These results show that the plant-expressed D-PIGS have the potential for translation towards a safe and easily scalable single antigen-based tetravalent dengue vaccine. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Altered regulation of Fc gamma RII on aged follicular dendritic cells correlates with immunoreceptor tyrosine-based inhibition motif signaling in B cells and reduced germinal center formation.

PubMed

Aydar, Yüksel; Balogh, Péter; Tew, John G; Szakal, Andras K

2003-12-01

Aging is associated with reduced trapping of Ag in the form of in immune complexes (ICs) by follicular dendritic cells (FDCs). We postulated that this defect was due to altered regulation of IC trapping receptors. The level of FDC-M1, complement receptors 1 and 2, FcgammaRII, and FDC-M2 on FDCs was immunohistochemically quantitated in draining lymph nodes of actively immunized mice for 10 days after Ag challenge. Initially, FDC FcgammaRII levels were similar but by day 3 a drastic reduction in FDC-FcgammaRII expression was apparent in old mice. FDC-M2 labeling, reflecting IC trapping, was also reduced and correlated with a dramatic reduction in germinal center (GC) B cells as indicated by reduced GC size and number. Nevertheless, labeling of FDC reticula with FDC-M1 and anti-complement receptors 1 and 2 was preserved, indicating that FDCs were present. FDCs in active GCs normally express high levels of FcRs that are thought to bind Fc portions of Abs in ICs and minimize their binding to FcRs on B cells. Thus, cross-linking of B cell receptor and FcR via IC is minimized, thereby reducing signaling via the immunoreceptor tyrosine-based inhibition motif. Old FDCs taken at day 3, when they lack FcgammaRII, were incapable of preventing immunoreceptor tyrosine-based inhibition motif signaling in wild-type B cells but old FDCs stimulated B cells from FcgammaRIIB(-/-) mice to produce near normal levels of specific Ab. The present data support the concept that FcR are regulated abnormally on old FDCs. This abnormality correlates with a reduced IC retention and with a reduced capacity of FDCs to present ICs in a way that will activate GC B cells.

Differential Fc-receptor engagement drives an anti-tumor vaccinal effect

PubMed Central

DiLillo, David J.; Ravetch, Jeffrey V.

2015-01-01

Summary Passively-administered anti-tumor mAbs rapidly kill tumor targets via FcγR-mediated cytotoxicity (ADCC), a short-term process. However, anti-tumor mAb treatment can also induce a vaccinal effect, in which mAb-mediated tumor death induces a long-term anti-tumor cellular immune response. To determine how such responses are generated, we utilized a murine model of an anti-tumor vaccinal effect against a model neoantigen. We demonstrate that FcγR expression by CD11c+ antigen-presenting cells is required to generate anti-tumor T cell responses upon ADCC-mediated tumor clearance. Using FcγR-humanized mice, we demonstrate that anti-tumor huIgG1 must engage hFcγRIIIA on macrophages to mediate ADCC, but also engage hFcγRIIA, the sole hFcγR expressed by human DCs, to generate a potent vaccinal effect. Thus, while next-generation anti-tumor antibodies with enhanced binding to only hFcγRIIIA are now in clinical use, ideal anti-tumor antibodies must be optimized for both cytotoxic effects as well as hFcγRIIA engagement on DCs to stimulate long-term anti-tumor cellular immunity. PMID:25976835

Serum Levels of Two Immunological Markers, the Soluble Low Affinity Receptor for IGE (SFCERII, SCD23) and their Correlation with Age, Gender and the Onset of Childhood Atopy

DTIC Science & Technology

1993-01-01

immunoglobulin receptor because it is the only known Fc Receptor which does not belong to the same gene I 0 superfamily as its ligand. (9, 14, 46). This FC...type) animal lectins. (2, 3, 4, 6, 8, 9, 13, 14, 20, 46). This homology domain spanning from cysteine 163 through cysteine 282, contAins four highly...substantial amount of CD23a and CD23b. (12) The expression of CD23 is lost after immunoglobulin isotype switching and during the differentiation of B cells into

Regulation of ITAM adaptor molecules and their receptors by inhibition of calcineurin-NFAT signalling during late stage osteoclast differentiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zawawi, M.S.F.; Discipline of Anatomy and Pathology, School of Medical Sciences, University of Adelaide, Adelaide, SA 5005; Dharmapatni, A.A.S.S.K.

2012-10-19

Highlights: Black-Right-Pointing-Pointer Calcineurin/NFAT inhibitors FK506 and VIVIT treated human PBMC derived osteoclasts in vitro. Black-Right-Pointing-Pointer Differential regulation of ITAM receptors and adaptor molecules by calcineurin/NFAT inhibitors. Black-Right-Pointing-Pointer FK506 and VIVIT suppress ITAM factors during late phase osteoclast differentiation. -- Abstract: Osteoclasts are specialised bone resorptive cells responsible for both physiological and pathological bone loss. Osteoclast differentiation and activity is dependent upon receptor activator NF-kappa-B ligand (RANKL) interacting with its receptor RANK to induce the transcription factor, nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1). The immunoreceptor tyrosine-based activation motif (ITAM)-dependent pathway has been identified as a co-stimulatory pathway inmore » osteoclasts. Osteoclast-associated receptor (OSCAR) and triggering receptor expressed in myeloid cells (TREM2) are essential receptors that pair with adaptor molecules Fc receptor common gamma chain (FcR{gamma}) and DNAX-activating protein 12 kDa (DAP12) respectively to induce calcium signalling. Treatment with calcineurin-NFAT inhibitors, Tacrolimus (FK506) and the 11R-VIVIT (VIVIT) peptide, reduces NFATc1 expression consistent with a reduction in osteoclast differentiation and activity. This study aimed to investigate the effects of inhibiting calcineurin-NFAT signalling on the expression of ITAM factors and late stage osteoclast genes including cathepsin K (CathK), Beta 3 integrin ({beta}3) and Annexin VIII (AnnVIII). Human peripheral blood mononuclear cells (PBMCs) were differentiated with RANKL and macrophage-colony stimulating factor (M-CSF) over 10 days in the presence or absence of FK506 or VIVIT. Osteoclast formation (as assessed by tartrate resistant acid phosphatase (TRAP)) and activity (assessed by dentine pit resorption) were significantly reduced with treatment. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis demonstrated that FK506 treatment significantly (p < 0.05) reduced the expression of NFATc1, CathK, OSCAR, FcR{gamma}, TREM2 and DAP12 during the terminal stage of osteoclast formation. VIVIT treatment significantly (p < 0.05) decreased CathK, OSCAR, FcR{gamma}, and AnnVIII, gene expression. This data suggest FK506 and VIVIT act differently in targeting the calcineurin-NFAT signalling cascade to suppress key mediators of the ITAM pathway during late stage osteoclast differentiation and this is associated with a reduction in both osteoclast differentiation and activity.« less

Activatory and Inhibitory Fcγ Receptors Augment Rituximab-mediated Internalization of CD20 Independent of Signaling via the Cytoplasmic Domain*

PubMed Central

Vaughan, Andrew T.; Chan, Claude H. T.; Klein, Christian; Glennie, Martin J.; Beers, Stephen A.; Cragg, Mark S.

2015-01-01

Type I anti-CD20 mAb such as rituximab and ofatumumab engage with the inhibitory FcγR, FcγRIIb on the surface of B cells, resulting in immunoreceptor tyrosine-based inhibitory motif (ITIM) phosphorylation. Internalization of the CD20·mAb·FcγRIIb complex follows, the rate of which correlates with FcγRIIb expression. In contrast, although type II anti-CD20 mAb such as tositumomab and obinutuzumab also interact with and activate FcγRIIb, this interaction fails to augment the rate of CD20·mAb internalization, raising the question of whether ITIM phosphorylation plays any role in this process. We have assessed the molecular requirements for the internalization process and demonstrate that in contrast to internalization of IgG immune complexes, FcγRIIb-augmented internalization of rituximab-ligated CD20 occurs independently of the FcγRIIb ITIM, indicating that signaling downstream of FcγRIIb is not required. In transfected cells, activatory FcγRI, FcγRIIa, and FcγRIIIa augmented internalization of rituximab-ligated CD20 in a similar manner. However, FcγRIIa mediated a slower rate of internalization than cells expressing equivalent levels of the highly homologous FcγRIIb. The difference was maintained in cells expressing FcγRIIa and FcγRIIb lacking cytoplasmic domains and in which the transmembrane domains had been exchanged. This difference may be due to increased degradation of FcγRIIa, which traffics to lysosomes independently of rituximab. We conclude that the cytoplasmic domain of FcγR is not required for promoting internalization of rituximab-ligated CD20. Instead, we propose that FcγR provides a structural role in augmenting endocytosis that differs from that employed during the endocytosis of immune complexes. PMID:25568316

Activatory and inhibitory Fcγ receptors augment rituximab-mediated internalization of CD20 independent of signaling via the cytoplasmic domain.

PubMed

Vaughan, Andrew T; Chan, Claude H T; Klein, Christian; Glennie, Martin J; Beers, Stephen A; Cragg, Mark S

2015-02-27

Type I anti-CD20 mAb such as rituximab and ofatumumab engage with the inhibitory FcγR, FcγRIIb on the surface of B cells, resulting in immunoreceptor tyrosine-based inhibitory motif (ITIM) phosphorylation. Internalization of the CD20·mAb·FcγRIIb complex follows, the rate of which correlates with FcγRIIb expression. In contrast, although type II anti-CD20 mAb such as tositumomab and obinutuzumab also interact with and activate FcγRIIb, this interaction fails to augment the rate of CD20·mAb internalization, raising the question of whether ITIM phosphorylation plays any role in this process. We have assessed the molecular requirements for the internalization process and demonstrate that in contrast to internalization of IgG immune complexes, FcγRIIb-augmented internalization of rituximab-ligated CD20 occurs independently of the FcγRIIb ITIM, indicating that signaling downstream of FcγRIIb is not required. In transfected cells, activatory FcγRI, FcγRIIa, and FcγRIIIa augmented internalization of rituximab-ligated CD20 in a similar manner. However, FcγRIIa mediated a slower rate of internalization than cells expressing equivalent levels of the highly homologous FcγRIIb. The difference was maintained in cells expressing FcγRIIa and FcγRIIb lacking cytoplasmic domains and in which the transmembrane domains had been exchanged. This difference may be due to increased degradation of FcγRIIa, which traffics to lysosomes independently of rituximab. We conclude that the cytoplasmic domain of FcγR is not required for promoting internalization of rituximab-ligated CD20. Instead, we propose that FcγR provides a structural role in augmenting endocytosis that differs from that employed during the endocytosis of immune complexes. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Variation in the expression of macrophage Fc epsilon receptors in relation to experimental rat schistosome infection.

PubMed

Pestel, J; Joseph, M; Dessaint, J P; Capron, A

1988-01-01

The relationship between IgE and rat peritoneal macrophages during the course of Schistosoma mansoni infection was examined. Immune macrophages exhibited an IgE-dependent schistosomulicidal activity mainly between the 5th and the 7th weeks. At this period the percentages of anti-IgE rosettes whose variations appeared consecutive to the variations in the serum IgE level were higher. Following incubation in a serum-free medium immune macrophages could release membrane-associated IgE, to a certain extent, and consequently formed rosettes with IgE-coated erythrocytes, indicating the existence of Fc epsilon receptors. Thus, in terms of rosettes, their number varied in the course of the disease. In fact IgE-rich serum (i.e. at day 42) as IgE molecules could induce this macrophage Fc epsilon receptor. Moreover when transferred to syngeneic rats in association with parasite-specific IgE Fc epsilon R2+ macrophages led to some protection against challenge infection. All the data reported here emphasize the determining role of macrophages and IgE in immunity to schistosomiasis.

The neonatal Fc receptor (FcRn) binds independently to both sites of the IgG homodimer with identical affinity.

PubMed

Abdiche, Yasmina Noubia; Yeung, Yik Andy; Chaparro-Riggers, Javier; Barman, Ishita; Strop, Pavel; Chin, Sherman Michael; Pham, Amber; Bolton, Gary; McDonough, Dan; Lindquist, Kevin; Pons, Jaume; Rajpal, Arvind

2015-01-01

The neonatal Fc receptor (FcRn) is expressed by cells of epithelial, endothelial and myeloid lineages and performs multiple roles in adaptive immunity. Characterizing the FcRn/IgG interaction is fundamental to designing therapeutic antibodies because IgGs with moderately increased binding affinities for FcRn exhibit superior serum half-lives and efficacy. It has been hypothesized that 2 FcRn molecules bind an IgG homodimer with disparate affinities, yet their affinity constants are inconsistent across the literature. Using surface plasmon resonance biosensor assays that eliminated confounding experimental artifacts, we present data supporting an alternate hypothesis: 2 FcRn molecules saturate an IgG homodimer with identical affinities at independent sites, consistent with the symmetrical arrangement of the FcRn/Fc complex observed in the crystal structure published by Burmeister et al. in 1994. We find that human FcRn binds human IgG1 with an equilibrium dissociation constant (KD) of 760 ± 60 nM (N = 14) at 25°C and pH 5.8, and shows less than 25% variation across the other human subtypes. Human IgG1 binds cynomolgus monkey FcRn with a 2-fold higher affinity than human FcRn, and binds both mouse and rat FcRn with a 10-fold higher affinity than human FcRn. FcRn/IgG interactions from multiple species show less than a 2-fold weaker affinity at 37°C than at 25°C and appear independent of an IgG's variable region. Our in vivo data in mouse and rat models demonstrate that both affinity and avidity influence an IgG's serum half-life, which should be considered when choosing animals, especially transgenic systems, as surrogates.

Altered polymorphonuclear leukocyte Fc gamma R expression contributes to decreased candicidal activity during intraabdominal sepsis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simms, H.H.; D'Amico, R.; Monfils, P.

We investigated the effects of untreated intraabdominal sepsis on polymorphonuclear leukocyte (PMN) candicidal activity. Two groups of swine were studied. Group I (n=6) underwent sham laparotomy, group II (n=7) underwent cecal ligation and incision. Untreated intraabdominal sepsis resulted in a progressive decrease in PMN candicidal activity. Concomitant rosetting and phagocytosis assays demonstrated a decrease in both the attachment and phagocytosis of Candida albicans opsonized with both normal and septic swine serum by PMNs in group II. Iodine 125-labeled swine immunoglobulin G (IgG) and fluorescein isothioalanate (FITC)-labeled swine IgG were used to investigate Fc gamma receptor ligand interactions. Scatchard analyses demonstratedmore » a progressive decline in both the binding affinity constant and number of IgG molecules bound per PMN. Stimulation of the oxidative burst markedly reduced 125I-labeled IgG binding in both group I and group II, with a greater decrement being seen in animals with intraabdominal sepsis. Further, in group II, PMN recycling of the Fc gamma receptor to the cell surface after generation of the oxidative burst was reduced by postoperative day 4. Binding of monoclonal antibodies to Fc gamma receptor II, but not Fc gamma receptor I/III markedly reduced intracellular candicidal activity. Immunofluorescence studies revealed a homogeneous pattern of FITC-IgG uptake by nearly all group I PMNs, whereas by postoperative day 8 a substantial number of PMNs from group II failed to internalize the FITC-IgG. These studies suggest that untreated intraabdominal sepsis reduces PMN candicidal activity and that this is due, in part, to altered PMN Fc gamma receptor ligand interactions.« less

Recombinant anthrax toxin receptor-Fc fusion proteins produced in plants protect rabbits against inhalational anthrax.

PubMed

Wycoff, Keith L; Belle, Archana; Deppe, Dorothée; Schaefer, Leah; Maclean, James M; Haase, Simone; Trilling, Anke K; Liu, Shihui; Leppla, Stephen H; Geren, Isin N; Pawlik, Jennifer; Peterson, Johnny W

2011-01-01

Inhalational anthrax, a zoonotic disease caused by the inhalation of Bacillus anthracis spores, has a ∼50% fatality rate even when treated with antibiotics. Pathogenesis is dependent on the activity of two toxic noncovalent complexes: edema toxin (EdTx) and lethal toxin (LeTx). Protective antigen (PA), an essential component of both complexes, binds with high affinity to the major receptor mediating the lethality of anthrax toxin in vivo, capillary morphogenesis protein 2 (CMG2). Certain antibodies against PA have been shown to protect against anthrax in vivo. As an alternative to anti-PA antibodies, we produced a fusion of the extracellular domain of human CMG2 and human IgG Fc, using both transient and stable tobacco plant expression systems. Optimized expression led to the CMG2-Fc fusion protein being produced at high levels: 730 mg/kg fresh leaf weight in Nicotiana benthamiana and 65 mg/kg in N. tabacum. CMG2-Fc, purified from tobacco plants, fully protected rabbits against a lethal challenge with B. anthracis spores at a dose of 2 mg/kg body weight administered at the time of challenge. Treatment with CMG2-Fc did not interfere with the development of the animals' own immunity to anthrax, as treated animals that survived an initial challenge also survived a rechallenge 30 days later. The glycosylation of the Fc (or lack thereof) had no significant effect on the protective potency of CMG2-Fc in rabbits or on its serum half-life, which was about 5 days. Significantly, CMG2-Fc effectively neutralized, in vitro, LeTx-containing mutant forms of PA that were not neutralized by anti-PA monoclonal antibodies.

Membrane and functional characterization of lymphoid and macrophage populations of Peyer's patches from adult and aged mice.

PubMed Central

Vĕtvicka, V; Tlaskalová-Hogenová, H; Fornůsek, L; Ríhová, B; Holán, V

1987-01-01

Properties of macrophages isolated from Peyer's patches were compared with properties of peritoneal macrophages. We found a very low expression of all types of Fc receptors as well as a low expression of Ia antigens on Peyer's patch macrophages. No substantial changes in the levels of FcR and Ia antigen expression were found during the process of ageing. The investigation of phagocytic activity showed the activated state of Peyer's patch macrophages. Comparing the surface markers of lymphocytes obtained from Peyer's patches of mice of different ages, we found no differences in the numbers of sIg+, Thy-+ or L3T4+ lymphocytes. The numbers of FcR+ and Lyt 2.2+ lymphocytes decreased markedly with age. PMID:3477526

ERE environment- and cell type-specific transcriptional effects of estrogen in normal endometrial cells.

PubMed

Lascombe, I; Sallot, M; Vuillermoz, C; Weisz, A; Adessi, G L; Jouvenot, M

1998-04-30

Our previous results have suggested a repression of E2 (17beta-estradiol) effect on the c-fos gene of cultured guinea-pig endometrial cells. To investigate this repression, the expression of three human c-fos gene recombinants, pFC1-BL (-2250/+41), pFC2-BL (-1400/+41) and pFC2E (-1300/-1050 and -230/+41), known to be E2-responsive in Hela cells, was studied in stromal (SC) and glandular epithelial cells (GEC). In both cellular types, pFC1-BL was not induced by E2, even in the presence of growth factors or co-transfected estrogen receptor. The pattern of pFC2-BL and pFC2E expression was strikingly different and depended on the cellular type: pFC2-BL and pFC2E induction was restricted to the glandular epithelial cells and did not occur in the SCs. We argue for a repression of E2 action which is dependent on the estrogen-responsive cis-acting element (ERE) environment and also cell type-specific involving DNA/protein and/or protein/protein interactions with cellular type-specific factors.

Basophil FcεRI Expression in Chronic Spontaneous Urticaria: A Potential Immunological Predictor of Response to Omalizumab Therapy.

PubMed

Deza, Gustavo; Bertolín-Colilla, Marta; Pujol, Ramon M; Curto-Barredo, Laia; Soto, Dulce; García, Maribel; Hernández, Pilar; Gimeno, Ramon; Giménez-Arnau, Ana M

2017-06-09

Although the efficacy of omalizumab has been clearly demonstrated in the treatment of chronic spontaneous urticaria (CSU), its mechanism of action, which results in improvement in CSU symptoms, is not entirely understood. This study investigated the effect of omalizumab on expression of the high-affinity IgE receptor (FcεRI) on blood basophils from patients with active CSU, and its association with the clinical response. Patients exhibiting significant clinical improvement showed a sharp reduction in the levels of basophil FcεRI after 4 weeks, which was maintained throughout the total duration of the treatment. Such evolution was not observed in non-responder patients. Furthermore, non-responders showed significantly lower baseline levels of FcεRI than responders. Baseline basophil FcεRI expression was found to be a potential immunological predictor of response to omalizumab (100% sensitivity and 73.2% specificity). The results of this study contribute to our knowledge of the therapeutic benefit and mechanism of action of anti-IgE therapy in CSU.

Effects of granulocyte colony-stimulating factor (G-CSF) treatment on granulocyte function and receptor expression in patients with ventilator-dependent pneumonia

PubMed Central

Hustinx, W N M; Van Kessel, C P M; Heezius, E; Burgers, S; Lammers, J-W; Hoepelman, I M

1998-01-01

Considerable experimental evidence in animals suggests that treatment with G-CSF may have a beneficial effect in the management of severe infections in non-neutropenic hosts. This beneficial effect is attributed to an enhancement of granulopoiesis and neutrophil function, the latter possibly involving up-regulation of receptors on neutrophils that are involved in antibody-mediated cytotoxicity and killing of microorganisms. We compared neutrophil function and phenotype in blood and bronchoalveolar lavage fluid (BALF) of 10 patients with severe ventilator-dependent pneumonia, at baseline and following initiation of G-CSF treatment as adjunct to standard therapy. G-CSF treatment was associated with three-fold increased blood neutrophil counts at day 3 of treatment compared with baseline counts. Mean serum G-CSF concentration increased from 313 to 2007 pg/ml. After correction for lavage dilution effects, BALF G-CSF levels did not differ significantly from baseline, nor did neutrophil receptor expression (FcγRI, FcγRII, FcγRIII, CR3, and l-selectin) or indicators of neutrophil function such as respiratory burst activity, phagocytosis and killing of Candida albicans in BALF or blood. The mortality in this group of patients was 30% and compared favourably to the APACHE II-derived predicted mortality of 60%. We conclude that the possible therapeutic benefit of G-CSF administration in the early phase of severe bacterial pneumonia is not readily explained by its effect on baseline indicators of neutrophil function or receptor expression. PMID:9649199

A novel 1,2-benzenediamine derivative FC-99 suppresses TLR3 expression and ameliorates disease symptoms in a mouse model of sepsis

PubMed Central

Gong, Wei; Hu, Erling; Dou, Huan; Song, Yuxian; Yang, Liu; Ji, Jianjian; Li, Erguang; Tan, Renxiang; Hou, Yayi

2014-01-01

Background and Purpose Sepsis is a clinical condition characterized by overwhelming systemic inflammation with high mortality rate and high prevalence, but effective treatment is still lacking. Toll-like receptor 3 (TLR3) is an endogenous sensor, thought to regulate the amplification of immune response during sepsis. Modulators of TLR3 have an advantage in the treatment of sepsis. Here, we aimed to explore the mechanism of a monosubstituted 1,2-benzenediamine derivative FC-99 {N1-[(4-methoxy)methyl]-4-methyl-1,2-benzenediamine}on modulating TLR3 expression and its therapeutic potential on mouse model of sepsis. Experimental Approach Cells were pretreated with FC-99 followed by poly(I:C) or IFN-α stimulation; TLR3 and other indicators were assayed. Female C57BL/6 mice were subjected to sham or caecal ligation puncture (CLP) surgery after i.p. injection of vehicle or FC-99; serum and tissues were collected for further experiments. Key Results FC-99 suppressed inflammatory response induced by poly(I:C) with no effect on cell viability or uptake of poly(I:C). FC-99 also inhibited TLR3 expression induced by not only poly(I:C) but also by exogenous IFN-α. This inhibition of FC-99 was related to the poly(I:C)-evoked IRF3/IFN-α/JAK/STAT1 signalling pathway. In CLP-induced model of sepsis, FC-99 administration decreased mice mortality and serum levels of inflammatory factors, attenuated multiple organ dysfunction and enhanced bacterial clearance. Accordingly, systemic and local expression of TLR3 was reduced by FC-99 in vivo. Conclusion and Implications FC-99 reversed TLR3 expression and ameliorate CLP-induced sepsis in mice. Thus, FC-99 will be a potential therapeutic candidate for sepsis. PMID:24903157

A new C-type lectin (FcLec5) from the Chinese white shrimp Fenneropenaeus chinensis.

PubMed

Xu, Wen-Teng; Wang, Xian-Wei; Zhang, Xiao-Wen; Zhao, Xiao-Fan; Yu, Xiao-Qiang; Wang, Jin-Xing

2010-11-01

C-type lectins are one family of pattern recognition receptors (PRRs) that play important roles in innate immunity. In this work, cDNA and genomic sequences for a new C-type lectin (FcLec5) were obtained from the Chinese white shrimp Fenneropenaeus chinensis. FcLec5 cDNA contains an open reading frame of 1,008 bp and its genomic sequence is 1,137 bp with 4 exons and 3 introns. The predicted FcLec5 protein contains a signal peptide and two carbohydrate recognition domains (CRDs). The N-terminal CRD of FcLec5 has a predicted carbohydrate recognition motif of Gln-Pro-Asp (QPD), while the C-terminal CRD contains a motif of Glu-Pro-Gln (EPQ). Northern blot analysis showed that FcLec5 mRNA was specifically expressed in hepatopancreas. FcLec5 protein was expressed in hepatopancreas and secreted into hemolymph. Real-time PCR showed that FcLec5 transcript exhibited different expression profiles after immune-challenged with Vibrio anguillarum or White Spot Syndrome Virus (WSSV). Recombinant FcLec5 and its two individual CRDs could agglutinate most bacteria tested, and the agglutinating activity was Ca2+-dependent. Besides, the agglutinating activity to gram-negative bacteria is higher than that to gram-positive bacteria. Direct binding assay showed that recombinant FcLec5 could bind to all microorganisms tested (five gram-positive and four gram-negative bacteria, as well as yeast) in a Ca2+-independent manner. Recombinant FcLec5 also directly bound to bacterial peptidoglycan, lipopolysaccharide and lipoteichoic acids. These results suggest that FcLec5 may act as a PRR for bacteria via binding to bacterial cell wall polysaccharides in Chinese white shrimp.

Fcγ receptor IIIa single-nucleotide polymorphisms and haplotypes affect human IgG binding and are associated with lupus nephritis in African Americans.

PubMed

Dong, Chaoling; Ptacek, Travis S; Redden, David T; Zhang, Kui; Brown, Elizabeth E; Edberg, Jeffrey C; McGwin, Gerald; Alarcón, Graciela S; Ramsey-Goldman, Rosalind; Reveille, John D; Vilá, Luis M; Petri, Michelle; Qin, Aijian; Wu, Jianming; Kimberly, Robert P

2014-05-01

To investigate whether the Fcγ receptor IIIa-66L/R/H (FcγRIIIa-66L/R/H) polymorphism influences net effective receptor function and to assess if the FCGR3A combined genotypes formed by FcγRIIIa-66L/R/H and FcγRIIIa-176F/V, as well as copy number variation (CNV), confer risk of developing systemic lupus erythematosus (SLE) and lupus nephritis. FcγRIIIa variants, expressed on A20 IIA1.6 cells, were used in flow cytometry-based human IgG-binding assays. Using Pyrosequencing methodology, FCGR3A single-nucleotide polymorphism and CNV genotypes were determined in a cohort of 1,728 SLE patients and 2,404 healthy controls. The FcγRIIIa-66L/R/H (rs10127939) polymorphism influenced ligand binding capacity in the presence of the FcγRIIIa-176V (rs396991) allele. There was a trend toward an association of the low-binding FcγRIIIa-176F allele with lupus nephritis among African Americans (P = 0.0609) but not among European Americans (P > 0.10). Nephritis among African American patients with SLE was associated with FcγRIIIa low-binding haplotypes containing the 66L/R/H and 176F variants (P = 0.03) and with low-binding genotype combinations (P = 0.002). No association was observed among European American patients with SLE. The distribution of FCGR3A CNV was not significantly different among controls and SLE patients with or without nephritis. FcγRIIIa-66L/R/H influences ligand binding. The low-binding haplotypes formed by 66L/R/H and 176F confer enhanced risk of lupus nephritis in African Americans. FCGR3A CNVs are not associated with SLE or lupus nephritis in either African Americans or European Americans. Copyright © 2014 by the American College of Rheumatology.

Neonatal Fc Receptor Regulation of Lung Immunoglobulin and CD103+ Dendritic Cells Confers Transient Susceptibility to Tuberculosis.

PubMed

Vogelzang, Alexis; Lozza, Laura; Reece, Stephen T; Perdomo, Carolina; Zedler, Ulrike; Hahnke, Karin; Oberbeck-Mueller, Dagmar; Dorhoi, Anca; Kaufmann, Stefan H E

2016-10-01

The neonatal Fc receptor (FcRn) extends the systemic half-life of IgG antibodies by chaperoning bound Fc away from lysosomal degradation inside stromal and hematopoietic cells. FcRn also transports IgG across mucosal barriers into the lumen, and yet little is known about how FcRn modulates immunity in the lung during homeostasis or infection. We infected wild-type (WT) and FcRn-deficient (fcgrt(-/-)) mice with Pseudomonas aeruginosa or Mycobacterium tuberculosis to investigate whether recycling and transport of IgG via FcRn influences innate and adaptive immunity in the lung in response to bacterial infection. We found that FcRn expression maintains homeostatic IgG levels in lung and leads to preferential secretion of low-affinity IgG ligands into the lumen. Fcgrt(-/-) animals exhibited no evidence of developmental impairment of innate immunity in the lung and were able to efficiently recruit neutrophils in a model of acute bacterial pneumonia. Although local humoral immunity in lung increased independently of the presence of FcRn during tuberculosis, there was nonetheless a strong impact of FcRn deficiency on local adaptive immunity. We show that the quantity and quality of IgG in airways, as well as the abundance of dendritic cells in the lung, are maintained by FcRn. FcRn ablation transiently enhanced local T cell immunity and neutrophil recruitment during tuberculosis, leading to a lower bacterial burden in lung. This novel understanding of tissue-specific modulation of mucosal IgG isotypes in the lung by FcRn sheds light on the role of mucosal IgG in immune responses in the lung during homeostasis and bacterial disease. Copyright © 2016 Vogelzang et al.

Ephrin reverse signaling mediates palatal fusion and epithelial-to-mesenchymal transition independently of Tgfß3.

PubMed

Serrano, Maria J; Liu, Jingpeng; Svoboda, Kathy K H; Nawshad, Ali; Benson, M Douglas

2015-12-01

The mammalian secondary palate forms from shelves of epithelia-covered mesenchyme that meet at midline and fuse. The midline epithelial seam (MES) is thought to degrade by apoptosis, epithelial-to-mesenchymal transition (EMT), or both. Failure to degrade the MES blocks fusion and causes cleft palate. It was previously thought that transforming growth factor ß3 (Tgfß3) is required to initiate fusion. Members of the Eph tyrosine kinase receptor family and their membrane-bound ephrin ligands are expressed on the MES. We demonstrated that treatment of mouse palates with recombinant EphB2/Fc to activate ephrin reverse signaling (where the ephrin acts as a receptor and transduces signals from its cytodomain) was sufficient to cause mouse palatal fusion when Tgfß3 signaling was blocked by an antibody against Tgfß3 or by an inhibitor of the TgfßrI serine/threonine receptor kinase. Cultured palatal epithelial cells traded their expression of epithelial cell markers for that of mesenchymal cells and became motile after treatment with EphB2/Fc. They concurrently increased their expression of the EMT-associated transcription factors Snail, Sip1, and Twist1. EphB2/Fc did not cause apoptosis in these cells. These data reveal that ephrin reverse signaling directs palatal fusion in mammals through a mechanism that involves EMT but not apoptosis and activates a gene expression program not previously associated with ephrin reverse signaling. © 2015 Wiley Periodicals, Inc.

Tyrosine phosphorylation and association of Syk with Fc gamma RII in monocytic THP-1 cells.

PubMed Central

Ghazizadeh, S; Bolen, J B; Fleit, H B

1995-01-01

Although the cytoplasmic portion of the low-affinity receptor for immunoglobulin G, Fc gamma RII, does not contain a kinase domain, rapid tyrosine phosphorylation of intracellular substrates occurs in response to aggregation of the receptor. The use of specific tyrosine kinase inhibitors has suggested that these phosphorylations are required for subsequent cellular responses. We previously demonstrated the coprecipitation of a tyrosine kinase activity with Fc gamma RII, suggesting that non-receptor tyrosine kinases might associate with the cytoplasmic domain of Fc gamma RII. Anti-receptor immune complex kinase assays revealed the coprecipitation of several phosphoproteins, most notably p56/53lyn, an Src-family protein tyrosine kinase (PTK), and a 72 kDa phosphoprotein. Here we identify the 72 kDa Fc gamma RII-associated protein as p72syk (Syk), a member of a newly described family of non-receptor PTKs. A rapid and transient tyrosine phosphorylation of Syk was observed following Fc gamma RII activation. Syk was also tyrosyl-phosphorylated following aggregation of the high-affinity Fc gamma receptor, Fc gamma RI. The Fc gamma RI activation did not result in association of Syk with Fc gamma RII, implying that distinct pools of Syk are activated upon aggregation of each receptor in a localized manner. These results demonstrate a physical association between Syk and Fc gamma RII and suggest that the molecules involved in Fc gamma RII signalling are very similar to the ones utilized by multichain immune recognition receptors such as the B-cell antigen receptor and the high-affinity IgE receptor. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:7530449

The Neonatal Fc Receptor (FcRn) Enhances Human Immunodeficiency Virus Type 1 (HIV-1) Transcytosis across Epithelial Cells

PubMed Central

Gupta, Sandeep; Gach, Johannes S.; Becerra, Juan C.; Phan, Tran B.; Pudney, Jeffrey; Moldoveanu, Zina; Joseph, Sarah B.; Landucci, Gary; Supnet, Medalyn Jude; Ping, Li-Hua; Corti, Davide; Moldt, Brian; Hel, Zdenek; Lanzavecchia, Antonio; Ruprecht, Ruth M.; Burton, Dennis R.; Mestecky, Jiri; Anderson, Deborah J.; Forthal, Donald N.

2013-01-01

The mechanisms by which human immunodeficiency virus type 1 (HIV-1) crosses mucosal surfaces to establish infection are unknown. Acidic genital secretions of HIV-1-infected women contain HIV-1 likely coated by antibody. We found that the combination of acidic pH and Env-specific IgG, including that from cervicovaginal and seminal fluids of HIV-1-infected individuals, augmented transcytosis across epithelial cells as much as 20-fold compared with Env-specific IgG at neutral pH or non-specific IgG at either pH. Enhanced transcytosis was observed with clinical HIV-1 isolates, including transmitted/founder strains, and was eliminated in Fc neonatal receptor (FcRn)-knockdown epithelial cells. Non-neutralizing antibodies allowed similar or less transcytosis than neutralizing antibodies. However, the ratio of total:infectious virus was higher for neutralizing antibodies, indicating that they allowed transcytosis while blocking infectivity of transcytosed virus. Immunocytochemistry revealed abundant FcRn expression in columnar epithelia lining the human endocervix and penile urethra. Acidity and Env-specific IgG enhance transcytosis of virus across epithelial cells via FcRn and could facilitate translocation of virus to susceptible target cells following sexual exposure. PMID:24278022

Crosslinking of surface antibodies and Fc sub. gamma. receptors: Theory and application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wofsy, C.; Goldstein, B.

1991-03-15

In an immune response, the crosslinking of surface immunoglobulin (sIg) on B cells by multiply-bound ligand activates a range of cell responses, culminating in the production of antibody-secreting cells. However, when the crosslinking agent is itself an antibody, B cell activation is inhibited. Solution antibody (IgG) can bind simultaneously to sIg and to another cell surface receptor, Fc{sub {gamma}}R, co-crosslinking' the distinct receptors. Experiments point to co-crosslinking as the inhibitory signal. It is not clear how co-crosslinking inhibits B cell stimulation. The authors construct and analyze a mathematical model aimed at clarifying the nature and mechanisms of action of themore » separate cell signals controlling B cell responses to antibodies. Basophils and mast cells respond to the crosslinking of cell surface antibody by releasing histamine. Like B cells, basophils also express FC{sub {gamma}}R. They use their model to analyze new data on the effect of antibody-induced co-crosslinking of the two types of receptor on this family of cells. Predictions of the model indicate that an observed difference between the response patterns induced by antibodies and by antibody fragments that cannot bind to FC{sub {gamma}}R can be explained if co-crosslinking is neither inhibitory nor stimulatory in this system.« less

Human IgG lacking effector functions demonstrate lower FcRn-binding and reduced transplacental transport.

PubMed

Stapleton, Nigel M; Armstrong-Fisher, Sylvia S; Andersen, Jan Terje; van der Schoot, C Ellen; Porter, Charlene; Page, Kenneth R; Falconer, Donald; de Haas, Masja; Williamson, Lorna M; Clark, Michael R; Vidarsson, Gestur; Armour, Kathryn L

2018-03-01

We have previously generated human IgG1 antibodies that were engineered for reduced binding to the classical Fcγ receptors (FcγRI-III) and C1q, thereby eliminating their destructive effector functions (constant region G1Δnab). In their potential use as blocking agents, favorable binding to the neonatal Fc receptor (FcRn) is important to preserve the long half-life typical of IgG. An ability to cross the placenta, which is also mediated, at least in part, by FcRn is desirable in some indications, such as feto-maternal alloimmune disorders. Here, we show that G1Δnab mutants retain pH-dependent binding to human FcRn but that the amino acid alterations reduce the affinity of the IgG1:FcRn interaction by 2.0-fold and 1.6-fold for the two antibodies investigated. The transport of the modified G1Δnab mutants across monolayers of human cell lines expressing FcRn was approximately 75% of the wild-type, except that no difference was observed with human umbilical vein endothelial cells. G1Δnab mutation also reduced transport in an ex vivo placenta model. In conclusion, we demonstrate that, although the G1Δnab mutations are away from the FcRn-binding site, they have long-distance effects, modulating FcRn binding and transcellular transport. Our findings have implications for the design of therapeutic human IgG with tailored effector functions. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Molecular and functional characterization of FcγRIIIb receptor-ligand interaction: implications for neutrophil mediated immune mechanisms in malaria.

PubMed

Simtong, Piyapong; Romphruk, Amornrat V; Traum, Annalena; Burg-Roderfeld, Monika; Bein, Gregor; Jakubowski, Konstantin; Dominik, Andreas; Theisen, Michael; Kana, Ikhlaq Hussain; Sachs, Ulrich J; Santoso, Sentot

2018-05-21

The Fcγ receptor IIIb (FcγRIIIb) is a low-affinity receptor of IgG and is essential in neutrophil mediated effector functions. Different allelic forms of FcγRIIIb carrying human neutrophil antigen (HNA-1a, -1b, -1c and -1d) have been identified. Here, we have generated stable transfected HEK293 cell lines expressing HNA-1aa, -1bb, and -1bc. Of these, cells expressing HNA-1bc interacted significantly stronger (2.277 versus 0.743) with human IgG than cells expressing the HNA-1aa or -1bb alloforms. The higher affinity of IgG towards the HNA-1c alloform was confirmed using neutrophils derived from German blood donors. Neutrophils from HNA-1abc phenotyped individuals bound IgG significantly stronger (1.825 versus 0.903) than neutrophils from HNA-1ab typed individuals. These findings were confirmed by the SPR analysis demonstrating that recombinant HNA-1bc had a higher affinity (KD 7.24 x 10 -6 M) than recombinant HNA-1bb (KD 1.15 x 10 -5 M) against normal IgG. Finally, we demonstrated that Plasmodium falciparum merozoites opsonized with human IgG affinity purified against P. falciparum Glutamate rich protein (GLURP) enhanced stronger ROS emission in neutrophils obtained from HNA-1abc donors compared to neutrophils from HNA-1ab donors. Collectively, these results indicate that the amino acid substitution Ala 78 Asp resulting in the HNA-1c allotype leads to higher affinity towards human IgG, enhancement of neutrophil activation and possibly effective clearance of malaria by intracellular ROS. Copyright © 2018 American Society for Microbiology.

High resolution mapping of the binding site on human IgG1 for Fc gamma RI, Fc gamma RII, Fc gamma RIII, and FcRn and design of IgG1 variants with improved binding to the Fc gamma R.

PubMed

Shields, R L; Namenuk, A K; Hong, K; Meng, Y G; Rae, J; Briggs, J; Xie, D; Lai, J; Stadlen, A; Li, B; Fox, J A; Presta, L G

2001-03-02

Immunoglobulin G (IgG) Fc receptors play a critical role in linking IgG antibody-mediated immune responses with cellular effector functions. A high resolution map of the binding site on human IgG1 for human Fc gamma RI, Fc gamma RIIA, Fc gamma RIIB, Fc gamma RIIIA, and FcRn receptors has been determined. A common set of IgG1 residues is involved in binding to all Fc gamma R; Fc gamma RII and Fc gamma RIII also utilize residues outside this common set. In addition to residues which, when altered, abrogated binding to one or more of the receptors, several residues were found that improved binding only to specific receptors or simultaneously improved binding to one type of receptor and reduced binding to another type. Select IgG1 variants with improved binding to Fc gamma RIIIA exhibited up to 100% enhancement in antibody-dependent cell cytotoxicity using human effector cells; these variants included changes at residues not found at the binding interface in the IgG/Fc gamma RIIIA co-crystal structure (Sondermann, P., Huber, R., Oosthuizen, V., and Jacob, U. (2000) Nature 406, 267-273). These engineered antibodies may have important implications for improving antibody therapeutic efficacy.

Human IgG subclass cross-species reactivity to mouse and cynomolgus monkey Fcγ receptors.

PubMed

Derebe, Mehabaw G; Nanjunda, Rupesh K; Gilliland, Gary L; Lacy, Eilyn R; Chiu, Mark L

2018-05-01

In therapeutic antibody discovery and early development, mice and cynomolgus monkey are used as animal models to assess toxicity, efficacy and other properties of candidate molecules. As more candidate antibodies are based on human immunoglobulin (IgG) subclasses, many strategies are pursued to simulate the human system in the test animal. However, translation rate from a successful preclinical trial to an approved drug is extremely low. This may partly be due to differences in interaction of human IgG based candidate molecules to endogenous Fcγ receptors of model animals in comparison to those of human Fcγ receptors. In this study, we compare binding characteristics of human IgG subclasses commonly used in drug development (IgG1, IgG2, IgG4) and their respective Fc silent versions (IgG1σ, IgG2σ, IgG4 PAA) to human, mouse, and cynomolgus monkey Fcγ receptors. To control interactions between Fab and Fc domains, the test IgGs all have the same variable region sequences. We found distinct variations of interaction of human IgG subclasses to model animal Fcγ receptors in comparison to their human counterparts. Particularly, cynomolgus monkey Fcγ receptors showed consistently tighter binding to human IgGs than human Fcγ receptors. Moreover, the presumably Fc silent human IgG4 PAA framework bound to cynomolgus monkey FcγRI with nanomolar affinity while only very weak binding was observed for the human FcγRI. Our results highlighted the need for a thorough in vitro affinity characterization of candidate IgGs against model animal Fcγ receptors and careful design of preclinical studies. Copyright © 2018. Published by Elsevier B.V.

Analysis of the Fc Gamma Receptor-Dependent Component of Neutralization Measured by Anthrax Toxin Neutralization Assays▿

PubMed Central

Verma, Anita; Ngundi, Miriam M.; Meade, Bruce D.; De Pascalis, Roberto; Elkins, Karen L.; Burns, Drusilla L.

2009-01-01

Anthrax toxin neutralization assays are used to measure functional antibody levels elicited by anthrax vaccines in both preclinical and clinical studies. In this study, we investigated the magnitude and molecular nature of Fc gamma (Fcγ) receptor-dependent toxin neutralization observed in commonly used forms of the anthrax toxin neutralization assay. Significantly more Fcγ receptor-dependent neutralization was observed in the J774A.1 cell-based assay than in the RAW 264.7 cell-based assay, a finding that could be due to the larger numbers of Fcγ receptors that we found on J774A.1 cells by using flow cytometry. Thus, the extent to which Fcγ receptor-dependent neutralization contributes to the total neutralization measured by the assay depends on the specific cell type utilized in the assay. Using Fcγ receptor blocking monoclonal antibodies, we found that at least three murine Fcγ receptor classes, IIB, III, and IV, can contribute to Fcγ receptor-dependent neutralization. When antibodies elicited by immunization of rabbits with protective-antigen-based anthrax vaccines were analyzed, we found that the magnitude of Fcγ receptor-dependent neutralization observed in the J774A.1 cell-based assay was dependent on the concentration of protective antigen utilized in the assay. Our results suggest that the characteristics of the antibodies analyzed in the assay (e.g., species of origin, isotype, and subclass), as well as the assay design (e.g., cell type and protective antigen concentration), could significantly influence the extent to which Fcγ receptor-dependent neutralization contributes to the total neutralization measured by anthrax toxin neutralization assays. These findings should be considered when interpreting anthrax toxin neutralization assay output. PMID:19656993

IgE enhances Fc epsilon RI expression and IgE-dependent TNF-alpha release from canine skin mast cells.

PubMed

Brazís, P; De Mora, F; Ferrer, L; Puigdemont, A

2002-03-01

The role of IgE on mast cell (MC) activation is well known. Recent studies have demonstrated that IgE also has the ability to up-regulate the high affinity IgE receptor (Fc epsilon RI) on the surface of human and murine MC, leading to an increased production of cytokines and chemokines. In the present study, we have examined the influence of IgE levels on Fc epsilon RI expression, and its consequences on TNF-alpha production from canine skin MC. Mature MC were enzymatically dispersed from the skin biopsies of 6-8 dogs and were cultured for up to 5 days in medium supplemented with recombinant canine stem cell factor (SCF) (6 ng/ml), in the presence of increasing serum IgE concentrations (ranging from 0 to 80 microg/ml). Subsequently, skin MC were activated with anti-IgE, and TNF-alpha concentration was assessed 5h post-activation by a cytotoxic bioassay. Fc epsilon RI receptors were identified in MC surface by flow cytometry. MC cultured for up to 5 days in the presence of high serum IgE concentration (8 microg/ml) produced twice the quantity of TNF-alpha than MC cultured in the absence of serum IgE, in response to stimulation with anti-IgE. Moreover, the percentage of Fc epsilon RI-positive skin cells was found to be approximately double in cells cultured with serum IgE compared to that cultured in the absence of IgE, following saturation of IgE receptors. These results suggest that, as found in human and murine MC, IgE may induce an up-regulation of the Fc epsilon RI density and an enhancement in the secretory activity of canine skin MC. This study could be of great interest in designing new therapeutic strategies for controlling MC activation in inflammatory and allergic processes.

Cloning of the cDNA for a hematopoietic cell-specific protein related to CD20 and the {beta} subunit of the high-affinity IgE receptor: Evidence for a family of proteins with four membrane-spanning regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adra, C.N.; Morrison, P.; Lim, B.

1994-10-11

The authors report the cloning of the cDNA for a human gene whose mRNA is expressed specifically in hematopoietic cells. A long open reading frame in the 1.7-kb mRNA encodes a 214-aa protein of 25 kDa with four hydrophobic regions consistent with a protein that traverses the membrane four times. To reflect the structure and expression of this gene in diverse hematopoietic lineages of lymphoid and myeloid origin, the authors named the gene HTm{sub 4}. The protein is about 20% homologous to two other {open_quotes}four-transmembrane{close_quotes} proteins; the B-cell-specific antigen CD20 and the {beta} subunit of the high-affinity receptor for IgE,more » Fc{sub {epsilon}}RI{beta}. The highest homologies among the three proteins are found in the transmembrane domains, but conserved residues are also recognized in the inter-transmembrane domains and in the N and C termini. Using fluorescence in situ hybridization, they localized HTm{sub 4} to human chromosome 11q12-13.1, where the CD20 and Fc{sub {epsilon}}RI{beta} genes are also located. Both the murine homologue for CD20, Ly-44, and the murine Fc{sub {epsilon}}RI{beta} gene map to the same region in murine chromosome 19. The authors propose that the HTm{sub 4}, CD20, and Fc{sub {epsilon}}RI{beta} genes evolved from the same ancestral gene to form a family of four-transmembrane proteins. It is possible that other related members exist. Similar to CD20 and Fc{sub {epsilon}}RI{beta}, it is likely that Htm{sub 4} has a role in signal transduction and, like Fc{sub {epsilon}}RI{beta}, might be a subunit associated with receptor complexes.« less

Structure of FcRY, an avian immunoglobulin receptor related to mammalian mannose receptors, and its complex with IgY

PubMed Central

He, Yongning; Bjorkman, Pamela J.

2011-01-01

Fc receptors transport maternal antibodies across epithelial cell barriers to passively immunize newborns. FcRY, the functional counterpart of mammalian FcRn (a major histocompatibility complex homolog), transfers IgY across the avian yolk sac, and represents a new class of Fc receptor related to the mammalian mannose receptor family. FcRY and FcRn bind immunoglobulins at pH ≤6.5, but not pH ≥7, allowing receptor–ligand association inside intracellular vesicles and release at the pH of blood. We obtained structures of monomeric and dimeric FcRY and an FcRY–IgY complex and explored FcRY's pH-dependent binding mechanism using electron cryomicroscopy (cryoEM) and small-angle X-ray scattering. The cryoEM structure of FcRY at pH 6 revealed a compact double-ring “head,” in which the N-terminal cysteine-rich and fibronectin II domains were folded back to contact C-type lectin-like domains 1–6, and a “tail” comprising C-type lectin-like domains 7–8. Conformational changes at pH 8 created a more elongated structure that cannot bind IgY. CryoEM reconstruction of FcRY dimers at pH 6 and small-angle X-ray scattering analysis at both pH values confirmed both structures. The cryoEM structure of the FcRY–IgY revealed symmetric binding of two FcRY heads to the dimeric FcY, each head contacting the CH4 domain of one FcY chain. FcRY shares structural properties with mannose receptor family members, including a head and tail domain organization, multimerization that may regulate ligand binding, and pH-dependent conformational changes. Our results facilitate understanding of immune recognition by the structurally related mannose receptor family and comparison of diverse methods of Ig transport across evolution. PMID:21746914

Measles Virus (MV) Nucleoprotein Binds to a Novel Cell Surface Receptor Distinct from FcγRII via Its C-Terminal Domain: Role in MV-Induced Immunosuppression

PubMed Central

Laine, David; Trescol-Biémont, Marie-Claude; Longhi, Sonia; Libeau, Geneviève; Marie, Julien C.; Vidalain, Pierre-Olivier; Azocar, Olga; Diallo, Adama; Canard, Bruno; Rabourdin-Combe, Chantal; Valentin, Hélène

2003-01-01

During acute measles virus (MV) infection, an efficient immune response occurs, followed by a transient but profound immunosuppression. MV nucleoprotein (MV-N) has been reported to induce both cellular and humoral immune responses and paradoxically to account for immunosuppression. Thus far, this latter activity has been attributed to MV-N binding to human and murine FcγRII. Here, we show that apoptosis of MV-infected human thymic epithelial cells (TEC) allows the release of MV-N in the extracellular compartment. This extracellular N is then able to bind either to MV-infected or uninfected TEC. We show that recombinant MV-N specifically binds to a membrane protein receptor, different from FcγRII, highly expressed on the cell surface of TEC. This new receptor is referred to as nucleoprotein receptor (NR). In addition, different Ns from other MV-related morbilliviruses can also bind to FcγRII and/or NR. We show that the region of MV-N responsible for binding to NR maps to the C-terminal fragment (NTAIL). Binding of MV-N to NR on TEC triggers sustained calcium influx and inhibits spontaneous cell proliferation by arresting cells in the G0 and G1 phases of the cell cycle. Finally, MV-N binds to both constitutively expressed NR on a large spectrum of cells from different species and to human activated T cells, leading to suppression of their proliferation. These results provide evidence that MV-N, after release in the extracellular compartment, binds to NR and thereby plays a role in MV-induced immunosuppression. PMID:14557619

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wurzburg, Beth A.; Kim, Beomkyu; Tarchevskaya, Svetlana S.

IgE antibodies interact with the high affinity IgE Fc receptor, FcϵRI, and activate inflammatory pathways associated with the allergic response. The IgE-Fc region, comprising the C-terminal domains of the IgE heavy chain, binds FcϵRI and can adopt different conformations ranging from a closed form incompatible with receptor binding to an open, receptor-bound state. A number of intermediate states are also observed in different IgE-Fc crystal forms. To further explore this apparent IgE-Fc conformational flexibility and to potentially trap a closed, inactive state, we generated a series of disulfide bond mutants. Here we describe the structure and biochemical properties of anmore » IgE-Fc mutant that is trapped in the closed, non-receptor binding state via an engineered disulfide at residue 335 (Cys-335). Reduction of the disulfide at Cys-335 restores the ability of IgE-Fc to bind to its high affinity receptor, FcϵRIα. The structure of the Cys-335 mutant shows that its conformation is within the range of previously observed, closed form IgE-Fc structures and that it retains the hydrophobic pocket found in the hinge region of the closed conformation. Locking the IgE-Fc into the closed state with the Cys-335 mutation does not affect binding of two other IgE-Fc ligands, omalizumab and DARPin E2_79, demonstrating selective blocking of the high affinity receptor binding.« less

Ability of Bruton's Tyrosine Kinase Inhibitors to Sequester Y551 and Prevent Phosphorylation Determines Potency for Inhibition of Fc Receptor but not B-Cell Receptor Signaling.

PubMed

Bender, Andrew T; Gardberg, Anna; Pereira, Albertina; Johnson, Theresa; Wu, Yin; Grenningloh, Roland; Head, Jared; Morandi, Federica; Haselmayer, Philipp; Liu-Bujalski, Lesley

2017-03-01

Bruton's tyrosine kinase (Btk) is expressed in a variety of hematopoietic cells. Btk has been demonstrated to regulate signaling downstream of the B-cell receptor (BCR), Fc receptors (FcRs), and toll-like receptors. It has become an attractive drug target because its inhibition may provide significant efficacy by simultaneously blocking multiple disease mechanisms. Consequently, a large number of Btk inhibitors have been developed. These compounds have diverse binding modes, and both reversible and irreversible inhibitors have been developed. Reported herein, we have tested nine Btk inhibitors and characterized on a molecular level how their interactions with Btk define their ability to block different signaling pathways. By solving the crystal structures of Btk inhibitors bound to the enzyme, we discovered that the compounds can be classified by their ability to trigger sequestration of Btk residue Y551. In cells, we found that sequestration of Y551 renders it inaccessible for phosphorylation. The ability to sequester Y551 was an important determinant of potency against FcεR signaling as Y551 sequestering compounds were more potent for inhibiting basophils and mast cells. This result was true for the inhibition of FcγR signaling as well. In contrast, Y551 sequestration was less a factor in determining potency against BCR signaling. We also found that Btk activity is regulated differentially in basophils and B cells. These results elucidate important determinants for Btk inhibitor potency against different signaling pathways and provide insight for designing new compounds with a broader inhibitory profile that will likely result in greater efficacy. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

Developing the IVIG biomimetic, Hexa-Fc, for drug and vaccine applications

PubMed Central

Czajkowsky, Daniel M.; Andersen, Jan Terje; Fuchs, Anja; Wilson, Timothy J.; Mekhaiel, David; Colonna, Marco; He, Jianfeng; Shao, Zhifeng; Mitchell, Daniel A.; Wu, Gang; Dell, Anne; Haslam, Stuart; Lloyd, Katy A.; Moore, Shona C.; Sandlie, Inger; Blundell, Patricia A.; Pleass, Richard J.

2015-01-01

The remarkable clinical success of Fc-fusion proteins has driven intense investigation for even more potent replacements. Using quality-by-design (QbD) approaches, we generated hexameric-Fc (hexa-Fc), a ~20 nm oligomeric Fc-based scaffold that we here show binds low-affinity inhibitory receptors (FcRL5, FcγRIIb, and DC-SIGN) with high avidity and specificity, whilst eliminating significant clinical limitations of monomeric Fc-fusions for vaccine and/or cancer therapies, in particular their poor ability to activate complement. Mass spectroscopy of hexa-Fc reveals high-mannose, low-sialic acid content, suggesting that interactions with these receptors are influenced by the mannose-containing Fc. Molecular dynamics (MD) simulations provides insight into the mechanisms of hexa-Fc interaction with these receptors and reveals an unexpected orientation of high-mannose glycans on the human Fc that provides greater accessibility to potential binding partners. Finally, we show that this biosynthetic nanoparticle can be engineered to enhance interactions with the human neonatal Fc receptor (FcRn) without loss of the oligomeric structure, a crucial modification for these molecules in therapy and/or vaccine strategies where a long plasma half-life is critical. PMID:25912958

The high-affinity receptor for IgG, FcγRI, of humans and non-human primates.

PubMed

Chenoweth, Alicia M; Trist, Halina M; Tan, Peck-Szee; Wines, Bruce D; Hogarth, P Mark

2015-11-01

Non-human primate (NHP) models, especially involving macaques, are considered important models of human immunity and have been essential in preclinical testing for vaccines and therapeutics. Despite this, much less characterization of macaque Fc receptors has occurred compared to humans or mice. Much of the characterization of macaque Fc receptors so far has focused on the low-affinity Fc receptors, particularly FcγRIIIa. From these studies, it is clear that there are distinct differences between the human and macaque low-affinity receptors and their interaction with human IgG. Relatively little work has been performed on the high-affinity IgG receptor, FcγRI, especially in NHPs. This review will focus on what is currently known of how FcγRI interacts with IgG, from mutation studies and recent crystallographic studies of human FcγRI, and how amino acid sequence differences in the macaque FcγRI may affect this interaction. Additionally, this review will look at the functional consequences of differences in the amino acid sequences between humans and macaques. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Quantitative cumulative biodistribution of antibodies in mice: effect of modulating binding affinity to the neonatal Fc receptor.

PubMed

Yip, Victor; Palma, Enzo; Tesar, Devin B; Mundo, Eduardo E; Bumbaca, Daniela; Torres, Elizabeth K; Reyes, Noe A; Shen, Ben Q; Fielder, Paul J; Prabhu, Saileta; Khawli, Leslie A; Boswell, C Andrew

2014-01-01

The neonatal Fc receptor (FcRn) plays an important and well-known role in antibody recycling in endothelial and hematopoietic cells and thus it influences the systemic pharmacokinetics (PK) of immunoglobulin G (IgG). However, considerably less is known about FcRn's role in the metabolism of IgG within individual tissues after intravenous administration. To elucidate the organ distribution and gain insight into the metabolism of humanized IgG1 antibodies with different binding affinities FcRn, comparative biodistribution studies in normal CD-1 mice were conducted. Here, we generated variants of herpes simplex virus glycoprotein D-specific antibody (humanized anti-gD) with increased and decreased FcRn binding affinity by genetic engineering without affecting antigen specificity. These antibodies were expressed in Chinese hamster ovary cell lines, purified and paired radiolabeled with iodine-125 and indium-111. Equal amounts of I-125-labeled and In-111-labeled antibodies were mixed and intravenously administered into mice at 5 mg/kg. This approach allowed us to measure both the real-time IgG uptake (I-125) and cumulative uptake of IgG and catabolites (In-111) in individual tissues up to 1 week post-injection. The PK and distribution of the wild-type IgG and the variant with enhanced binding for FcRn were largely similar to each other, but vastly different for the rapidly cleared low-FcRn-binding variant. Uptake in individual tissues varied across time, FcRn binding affinity, and radiolabeling method. The liver and spleen emerged as the most concentrated sites of IgG catabolism in the absence of FcRn protection. These data provide an increased understanding of FcRn's role in antibody PK and catabolism at the tissue level.

Mucosal CXCR4+ IgG plasma cells contribute to the pathogenesis of human ulcerative colitis through FcγR-mediated CD14 macrophage activation.

PubMed

Uo, Michihide; Hisamatsu, Tadakazu; Miyoshi, Jun; Kaito, Daiki; Yoneno, Kazuaki; Kitazume, Mina T; Mori, Maiko; Sugita, Akira; Koganei, Kazutaka; Matsuoka, Katsuyoshi; Kanai, Takanori; Hibi, Toshifumi

2013-12-01

Chronic inflammation characterised by IgG-producing plasma cell infiltration of colonic mucosa is a histological hallmark of ulcerative colitis (UC); however, whether its function is pathogenic or protective remains unclear. To explore the contribution of intestinal IgG plasma cells to UC pathogenesis. We isolated lamina propria mononuclear cells (LPMCs) from intestinal mucosa of UC patients and analysed the characteristics of intestinal plasma cells (expression profiles of differentiation molecules and chemokine receptors). We investigated the involvement of IgG-immune complex (IC)-Fc gamma receptor (FcγR) signalling in intestinal inflammation by examining the cytokine production by LPMCs in response to IgG-IC stimulation. IgG plasma cells that were markedly increased in number in the inflamed mucosa of UC patients showed a distinct expression profile (CD19(+)CD27(low), CCR10(low)CXCR4(high)) compared with IgA plasma cells (CD19(+/-)CD27(high), CCR10(high)CXCR4(-/low)). In vitro IgG-IC stimulation activated intestinal CD14 macrophages that were increased in number in the inflamed mucosa of UC patients via FcγRI and FcγRII, and induced the extensive production of pro-inflammatory cytokines such as tumour necrosis factor (TNF) and interleukin-1β (IL-1β), comparable to the effect of commensal bacteria stimulation. Co-stimulation with IgG-IC and commensal bacteria increased TNF and IL-1β production more than stimulation with the latter alone. Furthermore, IgG-IC notably up-regulated the expression of TL1A, whereas commensal bacteria specifically induced IL-23. Collectively, these results demonstrate a novel aspect of UC pathogenesis in which unique IgG plasma cells infiltrate the inflamed mucosa via CXCR4, and critically influence UC pathogenesis by exacerbating mucosal inflammation through the activation of 'pathogenic' intestinal CD14 macrophages via IgG-IC-FcγR signalling.

Treatment with soluble activin type IIB-receptor improves bone mass and strength in a mouse model of Duchenne muscular dystrophy.

PubMed

Puolakkainen, Tero; Ma, Hongqian; Kainulainen, Heikki; Pasternack, Arja; Rantalainen, Timo; Ritvos, Olli; Heikinheimo, Kristiina; Hulmi, Juha J; Kiviranta, Riku

2017-01-19

Inhibition of activin/myostatin pathway has emerged as a novel approach to increase muscle mass and bone strength. Duchenne muscular dystrophy (DMD) is a neuromuscular disorder that leads to progressive muscle degeneration and also high incidence of fractures. The aim of our study was to test whether inhibition of activin receptor IIB ligands with or without exercise could improve bone strength in the mdx mouse model for DMD. Thirty-two mdx mice were divided to running and non-running groups and to receive either PBS control or soluble activin type IIB-receptor (ActRIIB-Fc) once weekly for 7 weeks. Treatment of mdx mice with ActRIIB-Fc resulted in significantly increased body and muscle weights in both sedentary and exercising mice. Femoral μCT analysis showed increased bone volume and trabecular number (BV/TV +80%, Tb.N +70%, P < 0.05) in both ActRIIB-Fc treated groups. Running also resulted in increased bone volume and trabecular number in PBS-treated mice. However, there was no significant difference in trabecular bone structure or volumetric bone mineral density between the ActRIIB-Fc and ActRIIB-Fc-R indicating that running did not further improve bone structure in ActRIIB-Fc-treated mice. ActRIIB-Fc increased bone mass also in vertebrae (BV/TV +20%, Tb.N +30%, P < 0.05) but the effects were more modest. The number of osteoclasts was decreased in histological analysis and the expression of several osteoblast marker genes was increased in ActRIIB-Fc treated mice suggesting decreased bone resorption and increased bone formation in these mice. Increased bone mass in femurs translated into enhanced bone strength in biomechanical testing as the maximum force and stiffness were significantly elevated in ActRIIB-Fc-treated mice. Our results indicate that treatment of mdx mice with the soluble ActRIIB-Fc results in a robust increase in bone mass, without any additive effect by voluntary running. Thus ActRIIB-Fc could be an attractive option in the treatment of musculoskeletal disorders.

Inhibition of B cell proliferation by antisense DNA to both alpha and beta forms of Fc epsilon R II.

PubMed

Bhatti, L; Behle, K; Stevens, R H

1992-10-01

Epstein-Barr Virus (EBV) infection activates B lymphocyte proliferation through partially understood mechanisms, resulting in phenotypic changes, including the appearance of new antigens. One such antigen is Fc epsilon R II/CD-23 which may be relevant for B cell proliferation. We have used anti-sense oligonucleotides to study the importance of the two forms of this molecule for proliferation in the EBV-transformed, Fc epsilon R II +ve lymphoblastoid B cell line, RPMI 8866. Anti-sense oligodeoxynucleotides were generated to the two forms of Fc epsilon R II; Fc epsilon R IIa (alpha) and IIb (beta) which differ only in their intracytoplasmic domains. Addition of increasing concentrations of anti-sense oligonucleotides, ranging from 1 to 30 microM, significantly decreased cellular proliferation as measured by the incorporation of [3H]thymidine (inhibition range 8-88%). Optimum inhibition of cellular proliferation was apparent at 15 microM concentration of both anti-sense Fc epsilon R IIa and IIb (Fc epsilon R IIa, mean +/- SE = 75 +/- 7% inhibition, p less than 0.001; Fc epsilon R IIb, mean +/- SE = 71 +/- 7% inhibition, p less than 0.001). Anti-sense oligonucleotides complementary to the common part of Fc epsilon R II resulted in a similar inhibition of proliferation. Sense oligonucleotides did not induce significant inhibition. Preincubation of sense and anti-sense oligonucleotides resulted in an abrogation of proliferation inhibition. Moreover, none of these oligonucleotides had any effect on a Fc epsilon R II -ve cell line. Incubation with both anti-sense IIa and IIb resulted in additive, but not synergistic inhibition of proliferation. Addition of soluble Fc epsilon R II did not reverse inhibition of proliferation, suggesting that membrane-bound or intracellular rather than soluble Fc epsilon R II was important for the induced proliferation. Analysis of cell surface expression for Fc epsilon II indicated that while there was a pronounced effect on cell number following incubation with anti-sense oligonucleotides, surface expression of Fc epsilon R II was consistent as measured over different time points. PCR analysis revealed that while most cells expressed either the alpha or the beta form of Fc epsilon R II, EBV-transformed cell lines, particularly RPMI 8866, were found to express both alpha and beta forms simultaneously. This may constitute a mechanism whereby EBV infection confers an immortal state to the cell, resulting in its uncontrolled proliferation. Cell lines expressing only one receptor form, either alpha or beta, were unaffected after incubation with anti-sense oligonucleotides.(ABSTRACT TRUNCATED AT 400 WORDS)

Signaling by Antibodies: Recent Progress

PubMed Central

Bournazos, Stylianos; Wang, Taia T.; Dahan, Rony; Maamary, Jad; Ravetch, Jeffrey V.

2017-01-01

IgG antibodies mediate a diversity of immune functions by coupling of antigen specificity through the Fab domain to signal transduction via Fc-Fc receptor interactions. Indeed, balanced IgG signaling through Type I and Type II Fc receptors is required for the control of pro-inflammatory, anti-inflammatory, and immunomodulatory processes. In this review, we discuss the mechanisms that govern IgG-Fc receptor interactions, highlighting the diversity of Fc receptor-mediated effector functions that regulate immunity and inflammation, as well as determine susceptibility to infection and autoimmunity, and responsiveness to antibody-based therapeutics, and vaccine responses. PMID:28446061

Progress on research of chicken IgY antibody-FcRY receptor combination and transfer.

PubMed

Tian, Zehua; Zhang, Xiaoying

2012-10-01

The transfer of maternal immunoglobulins (Igs) plays a significant role in fetal initial humoral immunity, of which process has changed and diversified during the evolution of vertebrates. IgY is a key molecular in antibody evolution which links ancient Igs and mammalian Igs such as IgG and IgE. IgY's transfer to the embryo is a two-step receptor-mediated process, including the transfer from the maternal bloodstream to the yolk sac, and from the yolk sac to the embryo. IgY's neonatal Fc receptor (FcRY) mainly functions in the second process. This article reviews IgY's status in antibody evolution and IgY's structure and application. Furthermore, this review compares the binding and transferring mechanism between mammalian IgG, and IgG's neonatal Fc receptor and chicken IgY-FcRY. Details of IgY-FcRY combination, such as combining conditions required, IgY-FcRY binding stoichiometry and exact binding sites on both FcRY and IgY are discussed. Likewise, the endocytosis, the main mechanism of IgY-FcRY transfer and recycling mechanism are analyzed. Related knowledge might be important for better understanding antibody and receptor evolution, antibody-receptor interaction and antibody function. Furthermore, such kind of knowledge might be useful for antibody drug research and development.

The TAM-family receptor Mer mediates production of HGF through the RhoA-dependent pathway in response to apoptotic cells.

PubMed

Park, Hyun-Jung; Baen, Ji-Yeon; Lee, Ye-Ji; Choi, Youn-Hee; Kang, Jihee Lee

2012-08-01

The TAM receptor protein tyrosine kinases Tyro3, Axl, and Mer play important roles in macrophage function. We investigated the roles of the TAM receptors in mediating the induction of hepatocyte growth factor (HGF) during the interaction of macrophages with apoptotic cells. Mer-specific neutralizing antibody, small interfering RNA (siRNA), and a recombinant Mer protein (Mer/Fc) inhibited HGF mRNA and protein expression, as well as activation of RhoA, Akt, and specific mitogen-activated protein (MAP) kinases in response to apoptotic cells. Inhibition of Axl or Tyro3 with specific antibodies, siRNA, or Fc-fusion proteins did not prevent apoptotic cell-induced HGF mRNA and protein expression and did not inhibit activation of the postreceptor signaling molecules RhoA and certain MAP kinases, including extracellular signal-regulated protein kinase and c-Jun NH(2)-terminal kinase. However, Axl- and Tyro3-specific blockers did inhibit the activation of Akt and p38 MAP kinase in response to apoptotic cells. In addition, none of the TAM receptors mediated the effects of apoptotic cells on transforming growth factor-β or epidermal growth factor mRNA expression. However, they were involved in the induction of vascular endothelial growth factor mRNA expression. Our data provide evidence that when macrophages interact with apoptotic cells, only Mer of the TAM-family receptors is responsible for mediating transcriptional HGF production through a RhoA-dependent pathway.

FcγRII-binding Centyrins mediate agonism and antibody-dependent cellular phagocytosis when fused to an anti-OX40 antibody

PubMed Central

Zhang, Di; Whitaker, Brian; Derebe, Mehabaw G.; Chiu, Mark L.

2018-01-01

ABSTRACT Immunostimulatory antibodies against the tumor necrosis factor receptors (TNFR) are emerging as promising cancer immunotherapies. The agonism activity of such antibodies depends on crosslinking to Fc gamma RIIB receptor (FcγRIIB) to enable the antibody multimerization that drives TNFR activation. Previously, Fc engineering was used to enhance the binding of such antibodies to Fcγ receptors. Here, we report the identification of Centyrins as alternative scaffold proteins with binding affinities to homologous FcγRIIB and FcγRIIA, but not to other types of Fcγ receptors. One Centyrin, S29, was engineered at distinct positions of an anti-OX40 SF2 antibody to generate bispecific and tetravalent molecules named as mAbtyrins. Regardless of the position of S29 on the SF2 antibody, SF2-S29 mAbtyrins could bind FcγRIIB and FcγRIIA specifically while maintaining binding to OX40 receptors. In a NFκB reporter assay, attachment of S29 Centyrin molecules at the C-termini, but not the N-termini, resulted in SF2 antibodies with increased agonism owing to FcγRIIB crosslinking. The mAbtyrins also showed agonism in T-cell activation assays with immobilized FcγRIIB and FcγRIIA, but this activity was confined to mAbtyrins with S29 specifically at the C-termini of antibody heavy chains. Furthermore, regardless of the position of the molecule, S29 Centyrin could equip an otherwise Fc-silent antibody with antibody-dependent cellular phagocytosis activity without affecting the antibody's intrinsic antibody-dependent cell-meditated cytotoxicity and complement-dependent cytotoxicity. In summary, the appropriate adoption FcγRII-binding Centyrins as functional modules represents a novel strategy to engineer therapeutic antibodies with improved functionalities. PMID:29359992

Identification and characterization of highly versatile peptide-vectors that bind non-competitively to the low-density lipoprotein receptor for in vivo targeting and delivery of small molecules and protein cargos

PubMed Central

David, Marion; Lécorché, Pascaline; Masse, Maxime; Faucon, Aude; Abouzid, Karima; Gaudin, Nicolas; Varini, Karine; Gassiot, Fanny; Ferracci, Géraldine; Jacquot, Guillaume; Vlieghe, Patrick

2018-01-01

Insufficient membrane penetration of drugs, in particular biotherapeutics and/or low target specificity remain a major drawback in their efficacy. We propose here the rational characterization and optimization of peptides to be developed as vectors that target cells expressing specific receptors involved in endocytosis or transcytosis. Among receptors involved in receptor-mediated transport is the LDL receptor. Screening complex phage-displayed peptide libraries on the human LDLR (hLDLR) stably expressed in cell lines led to the characterization of a family of cyclic and linear peptides that specifically bind the hLDLR. The VH411 lead cyclic peptide allowed endocytosis of payloads such as the S-Tag peptide or antibodies into cells expressing the hLDLR. Size reduction and chemical optimization of this lead peptide-vector led to improved receptor affinity. The optimized peptide-vectors were successfully conjugated to cargos of different nature and size including small organic molecules, siRNAs, peptides or a protein moiety such as an Fc fragment. We show that in all cases, the peptide-vectors retain their binding affinity to the hLDLR and potential for endocytosis. Following i.v. administration in wild type or ldlr-/- mice, an Fc fragment chemically conjugated or fused in C-terminal to peptide-vectors showed significant biodistribution in LDLR-enriched organs. We have thus developed highly versatile peptide-vectors endowed with good affinity for the LDLR as a target receptor. These peptide-vectors have the potential to be further developed for efficient transport of therapeutic or imaging agents into cells -including pathological cells—or organs that express the LDLR. PMID:29485998

Humoral Immunity Provides Resident Intestinal Eosinophils Access to Luminal Antigen via Eosinophil-Expressed Low-Affinity Fcγ Receptors.

PubMed

Smith, Kalmia M; Rahman, Raiann S; Spencer, Lisa A

2016-11-01

Eosinophils are native to the healthy gastrointestinal tract and are associated with inflammatory diseases likely triggered by exposure to food allergens (e.g., food allergies and eosinophilic gastrointestinal disorders). In models of allergic respiratory diseases and in vitro studies, direct Ag engagement elicits eosinophil effector functions, including degranulation and Ag presentation. However, it was not known whether intestinal tissue eosinophils that are separated from luminal food Ags by a columnar epithelium might similarly engage food Ags. Using an intestinal ligated loop model in mice, in this study we determined that resident intestinal eosinophils acquire Ag from the lumen of Ag-sensitized but not naive mice in vivo. Ag acquisition was Ig-dependent; intestinal eosinophils were unable to acquire Ag in sensitized Ig-deficient mice, and passive immunization with immune serum or Ag-specific IgG was sufficient to enable intestinal eosinophils in otherwise naive mice to acquire Ag in vivo. Intestinal eosinophils expressed low-affinity IgG receptors, and the activating receptor FcγRIII was necessary for Ig-mediated acquisition of Ags by isolated intestinal eosinophils in vitro. Our combined data suggest that intestinal eosinophils acquire lumen-derived food Ags in sensitized mice via FcγRIII Ag focusing and that they may therefore participate in Ag-driven secondary immune responses to oral Ags. Copyright © 2016 by The American Association of Immunologists, Inc.

Humoral immunity provides resident intestinal eosinophils access to luminal antigen via eosinophil-expressed low affinity Fc gamma receptors

PubMed Central

Smith, Kalmia M.; Rahman, Raiann S.; Spencer, Lisa A.

2016-01-01

Eosinophils are native to the healthy gastrointestinal tract, and are associated with inflammatory diseases likely triggered by exposure to food allergens (e.g. food allergies and eosinophilic gastrointestinal disorders). In models of allergic respiratory diseases and in vitro studies, direct antigen engagement elicits eosinophil effector functions including degranulation and antigen presentation. However, it was not known whether intestinal tissue eosinophils that are separated from luminal food antigens by a columnar epithelium might similarly engage food antigens. Using an intestinal ligated loop model in mice, here we determined that resident intestinal eosinophils acquire antigen from the lumen of antigen-sensitized but not naïve mice in vivo. Antigen acquisition was immunoglobulin-dependent; intestinal eosinophils were unable to acquire antigen in sensitized immunoglobulin-deficient mice, and passive immunization with immune serum or antigen-specific IgG was sufficient to enable intestinal eosinophils in otherwise naïve mice to acquire antigen in vivo. Intestinal eosinophils expressed low affinity IgG receptors, and the activating receptor FcγRIII was necessary for immunoglobulin-mediated acquisition of antigens by isolated intestinal eosinophils in vitro. Our combined data suggest that intestinal eosinophils acquire lumen-derived food antigens in sensitized mice via FcγRIII antigen focusing, and may therefore participate in antigen-driven secondary immune responses to oral antigens. PMID:27683752

Escherichia coli K1 induces pterin production for enhanced expression of Fcγ receptor I to invade RAW 264.7 macrophages

PubMed Central

Shanmuganathan, Muthusamy V.; Krishnan, Subramanian; Fu, Xiaowei; Prasadarao, Nemani V.

2013-01-01

Macrophages serve as permissive niches for Escherichia coli (E. coli) K1 to attain high grade bacteremia in the pathogenesis of meningitis in neonates. Although pterin levels are a diagnostic marker for immune activation, the role of macrophages in pterin production and in the establishment of meningitis is unknown. Here, we demonstrate that macrophages infected with E. coli K1 produce both neopterin and biopterin through increased expression of GTP-cyclohydrolase 1 (GCH1). Of note, increased production of biopterin enhances the expression of Fc-gamma receptor I (CD64), which in turn, aided the entry of E. coli K1 in macrophages while increased neopterin suppresses reactive oxygen species (ROS), thereby aiding bacterial survival. Inhibition of GCH1 by 2, 4-Diamino-6-hydroxypyrimidine (DAHP) prevented the E. coli K1 induced expression of CD64 in macrophages in vitro and the development of bacteremia in a newborn mouse model of meningitis. These studies suggest that targeting GCH1 could be therapeutic strategy for preventing neonatal meningitis by E. coli K1. PMID:24161960

Hyperactivity and reactivity of peripheral blood neutrophils in chronic periodontitis

PubMed Central

Matthews, J B; Wright, H J; Roberts, A; Cooper, P R; Chapple, I L C

2007-01-01

Some evidence exists that peripheral neutrophils from patients with chronic periodontitis generate higher levels of reactive oxygen species (ROS) after Fcγ-receptor stimulation than those from healthy controls. We hypothesized that peripheral neutrophils in periodontitis also show both hyper-reactivity to plaque organisms and hyperactivity in terms of baseline, unstimulated generation and release of ROS. Peripheral neutrophils from chronic periodontitis patients and age/sex/smoking-matched healthy controls (18 pairs) were assayed for total ROS generation and extracellular ROS release, with and without stimulation (Fcγ-receptor and Fusobacterium nucleatum), using luminol and isoluminol chemiluminescence. Assays were performed with and without priming with Escherichia coli lipopolysaccharide (LPS) and granulocyte–macrophage colony-stimulating factor (GM-CSF). Phox gene expression (p22, p47, p67, gp91) was investigated using reverse transcription–polymerase chain reaction (RT–PCR). Neutrophils from patients produced higher mean levels of ROS in all assays. Total generation and extracellular release of ROS by patients' cells were significantly greater than those from controls after FcγR-stimulation, with (P = 0·023) and without (P ≤ 0·023) priming with GM-CSF. Differences in unstimulated total ROS generation were not significant. By contrast, patients' cells demonstrated greater baseline, extracellular ROS release than those from controls (P = 0·004). This difference was maintained after priming with LPS (P = 0·028) but not GM-CSF (P = 0·217). Phox gene expression was similar in patient and control cells at baseline and stimulation with F. nucleatum (3 h) consistently reduced gp91PHOX transcripts. Our data demonstrate that peripheral neutrophils from periodontitis patients exhibit hyper-reactivity following stimulation (Fcγ-receptor and F. nucleatum) and hyperactivity in terms of excess ROS release in the absence of exogenous stimulation. This hyperactive/-reactive neutrophil phenotype is not associated with elevated phox gene expression. PMID:17223966

Fcγ receptor-mediated influx of S100A8/A9-producing neutrophils as inducer of bone erosion during antigen-induced arthritis.

PubMed

Di Ceglie, Irene; Ascone, Giuliana; Cremers, Niels A J; Sloetjes, Annet W; Walgreen, Birgitte; Vogl, Thomas; Roth, Johannes; Verbeek, J Sjef; van de Loo, Fons A J; Koenders, Marije I; van der Kraan, Peter M; Blom, Arjen B; van den Bosch, Martijn H J; van Lent, Peter L E M

2018-05-02

Osteoclast-mediated bone erosion is a central feature of rheumatoid arthritis (RA). Immune complexes, present in a large percentage of patients, bind to Fcγ receptors (FcγRs), thereby modulating the activity of immune cells. In this study, we investigated the contribution of FcγRs, and FcγRIV in particular, during antigen-induced arthritis (AIA). AIA was induced in knee joints of wild-type (WT), FcγRI,II,III -/- , and FcγRI,II,III,IV -/- mice. Bone destruction, numbers of tartrate-resistant acid phosphatase-positive (TRAP + ) osteoclasts, and inflammation were evaluated using histology; expression of the macrophage marker F4/80, neutrophil marker NIMPR14, and alarmin S100A8 was evaluated using immunohistochemistry. The percentage of osteoclast precursors in the bone marrow was determined using flow cytometry. In vitro osteoclastogenesis was evaluated with TRAP staining, and gene expression was assessed using real-time PCR. FcγRI,II,III,IV -/- mice showed decreased bone erosion compared with WT mice during AIA, whereas both the humoral and cellular immune responses against methylated bovine serum albumin were not impaired in FcγRI,II,III,IV -/- mice. The percentage of osteoclast precursors in the bone marrow of arthritic mice and their ability to differentiate into osteoclasts in vitro were comparable between FcγRI,II,III,IV -/- and WT mice. In line with these observations, numbers of TRAP + osteoclasts on the bone surface during AIA were comparable between the two groups. Inflammation, a process that strongly activates osteoclast activity, was reduced in FcγRI,II,III,IV -/- mice, and of note, mainly decreased numbers of neutrophils were present in the joint. In contrast to FcγRI,II,III,IV -/- mice, AIA induction in knee joints of FcγRI,II,III -/- mice resulted in increased bone erosion, inflammation, and numbers of neutrophils, suggesting a crucial role for FcγRIV in the joint pathology by the recruitment of neutrophils. Finally, significant correlations were found between bone erosion and the number of neutrophils present in the joint as well as between bone erosion and the number of S100A8-positive cells, with S100A8 being an alarmin strongly produced by neutrophils that stimulates osteoclast resorbing activity. FcγRs play a crucial role in the development of bone erosion during AIA by inducing inflammation. In particular, FcγRIV mediates bone erosion in AIA by inducing the influx of S100A8/A9-producing neutrophils into the arthritic joint.

Formation of infectious dengue virus-antibody immune complex in vivo in marmosets (Callithrix jacchus) after passive transfer of anti-dengue virus monoclonal antibodies and infection with dengue virus.

PubMed

Moi, Meng Ling; Ami, Yasushi; Shirai, Kenji; Lim, Chang-Kweng; Suzaki, Yuriko; Saito, Yuka; Kitaura, Kazutaka; Saijo, Masayuki; Suzuki, Ryuji; Kurane, Ichiro; Takasaki, Tomohiko

2015-02-01

Infection with a dengue virus (DENV) serotype induces cross-reactive, weakly neutralizing antibodies to different dengue serotypes. It has been postulated that cross-reactive antibodies form a virus-antibody immune complex and enhance DENV infection of Fc gamma receptor (FcγR)-bearing cells. We determined whether infectious DENV-antibody immune complex is formed in vivo in marmosets after passive transfer of DENV-specific monoclonal antibody (mAb) and DENV inoculation and whether infectious DENV-antibody immune complex is detectable using FcγR-expressing cells. Marmosets showed that DENV-antibody immune complex was exclusively infectious to FcγR-expressing cells on days 2, 4, and 7 after passive transfer of each of the mAbs (mAb 4G2 and mAb 6B6C) and DENV inoculation. Although DENV-antibody immune complex was detected, contribution of the passively transferred antibody to overall viremia levels was limited in this study. The results indicate that DENV cross-reactive antibodies form DENV-antibody immune complex in vivo, which is infectious to FcγR-bearing cells but not FcγR-negative cells. © The American Society of Tropical Medicine and Hygiene.

Expression and function of dopamine receptors in the developing medial frontal cortex and striatum of the rat

PubMed Central

Sillivan, Stephanie E.; Konradi, Christine

2011-01-01

The timeline of dopamine (DA) system maturation and the signaling properties of dopamine receptors (DRs) during rat brain development are not fully characterized. We used in situ hybridization and quantitative PCR to map DR mRNA transcripts in the medial frontal cortex (mFC) and striatum (STR) of the rat from embryonic day (E) 15 to E21. The developmental trajectory of DR mRNAs revealed distinct patterns of DA receptors 1 and 2 (DRD1, DRD2) in these brain regions. Whereas the mFC had a steeper increase in DRD1 mRNA, the STR had a steeper increase in DRD2 mRNA. Both DR mRNAs were expressed at a higher level in the STR compared to the mFC. To identify the functional properties of DRs during embryonic development, the phosphorylation states of cyclic AMP response element binding protein (CREB), extracellular signal-regulated kinase 1/2 (ERK1/2), and glycogen synthase kinase 3 beta (GSK3β) were examined after DR stimulation in primary neuronal cultures obtained from E15 and E18 embryos and cultured for 3 days to ensure a stable baseline level. DR-mediated signaling cascades were functional in E15 cultures in both brain regions. Because DA fibers do not reach the mFC by E15, and DA was not present in cultures, these data indicate that DRs can become functional in the absence of DA innervation. Since activation of DR signal transduction pathways can affect network organization of the developing brain, maternal exposure to drugs that affect DR activity may be liable to interfere with fetal brain development. PMID:22015925

A soluble bone morphogenetic protein type IA receptor increases bone mass and bone strength

PubMed Central

Baud’huin, Marc; Solban, Nicolas; Cornwall-Brady, Milton; Sako, Dianne; Kawamoto, Yoshimi; Liharska, Katia; Lath, Darren; Bouxsein, Mary L.; Underwood, Kathryn W.; Ucran, Jeffrey; Kumar, Ravindra; Pobre, Eileen; Grinberg, Asya; Seehra, Jasbir; Canalis, Ernesto; Pearsall, R. Scott; Croucher, Peter I.

2012-01-01

Diseases such as osteoporosis are associated with reduced bone mass. Therapies to prevent bone loss exist, but there are few that stimulate bone formation and restore bone mass. Bone morphogenetic proteins (BMPs) are members of the TGFβ superfamily, which act as pleiotropic regulators of skeletal organogenesis and bone homeostasis. Ablation of the BMPR1A receptor in osteoblasts increases bone mass, suggesting that inhibition of BMPR1A signaling may have therapeutic benefit. The aim of this study was to determine the skeletal effects of systemic administration of a soluble BMPR1A fusion protein (mBMPR1A–mFc) in vivo. mBMPR1A–mFc was shown to bind BMP2/4 specifically and with high affinity and prevent downstream signaling. mBMPR1A–mFc treatment of immature and mature mice increased bone mineral density, cortical thickness, trabecular bone volume, thickness and number, and decreased trabecular separation. The increase in bone mass was due to an early increase in osteoblast number and bone formation rate, mediated by a suppression of Dickkopf-1 expression. This was followed by a decrease in osteoclast number and eroded surface, which was associated with a decrease in receptor activator of NF-κB ligand (RANKL) production, an increase in osteoprotegerin expression, and a decrease in serum tartrate-resistant acid phosphatase (TRAP5b) concentration. mBMPR1A treatment also increased bone mass and strength in mice with bone loss due to estrogen deficiency. In conclusion, mBMPR1A–mFc stimulates osteoblastic bone formation and decreases bone resorption, which leads to an increase in bone mass, and offers a promising unique alternative for the treatment of bone-related disorders. PMID:22761317

Genetic deletion of muscle RANK or selective inhibition of RANKL is not as effective as full-length OPG-fc in mitigating muscular dystrophy.

PubMed

Dufresne, Sébastien S; Boulanger-Piette, Antoine; Bossé, Sabrina; Argaw, Anteneh; Hamoudi, Dounia; Marcadet, Laetitia; Gamu, Daniel; Fajardo, Val A; Yagita, Hideo; Penninger, Josef M; Russell Tupling, A; Frenette, Jérôme

2018-04-24

Although there is a strong association between osteoporosis and skeletal muscle atrophy/dysfunction, the functional relevance of a particular biological pathway that regulates synchronously bone and skeletal muscle physiopathology is still elusive. Receptor-activator of nuclear factor κB (RANK), its ligand RANKL and the soluble decoy receptor osteoprotegerin (OPG) are the key regulators of osteoclast differentiation and bone remodelling. We thus hypothesized that RANK/RANKL/OPG, which is a key pathway for bone regulation, is involved in Duchenne muscular dystrophy (DMD) physiopathology. Our results show that muscle-specific RANK deletion (mdx-RANK mko ) in dystrophin deficient mdx mice improves significantly specific force [54% gain in force] of EDL muscles with no protective effect against eccentric contraction-induced muscle dysfunction. In contrast, full-length OPG-Fc injections restore the force of dystrophic EDL muscles [162% gain in force], protect against eccentric contraction-induced muscle dysfunction ex vivo and significantly improve functional performance on downhill treadmill and post-exercise physical activity. Since OPG serves a soluble receptor for RANKL and as a decoy receptor for TRAIL, mdx mice were injected with anti-RANKL and anti-TRAIL antibodies to decipher the dual function of OPG. Injections of anti-RANKL and/or anti-TRAIL increase significantly the force of dystrophic EDL muscle [45% and 17% gains in force, respectively]. In agreement, truncated OPG-Fc that contains only RANKL domains produces similar gains, in terms of force production, than anti-RANKL treatments. To corroborate that full-length OPG-Fc also acts independently of RANK/RANKL pathway, dystrophin/RANK double-deficient mice were treated with full-length OPG-Fc for 10 days. Dystrophic EDL muscles exhibited a significant gain in force relative to untreated dystrophin/RANK double-deficient mice, indicating that the effect of full-length OPG-Fc is in part independent of the RANKL/RANK interaction. The sarco/endoplasmic reticulum Ca 2+ ATPase (SERCA) activity is significantly depressed in dysfunctional and dystrophic muscles and full-length OPG-Fc treatment increased SERCA activity and SERCA-2a expression. These findings demonstrate the superiority of full-length OPG-Fc treatment relative to truncated OPG-Fc, anti-RANKL, anti-TRAIL or muscle RANK deletion in improving dystrophic muscle function, integrity and protection against eccentric contractions. In conclusion, full-length OPG-Fc represents an efficient alternative in the development of new treatments for muscular dystrophy in which a single therapeutic approach may be foreseeable to maintain both bone and skeletal muscle functions.

Fc gamma receptor 3a genotype predicts overall survival in follicular lymphoma patients treated on SWOG trials with combined monoclonal antibody plus chemotherapy but not chemotherapy alone

PubMed Central

Persky, Daniel O.; Dornan, David; Goldman, Bryan H.; Braziel, Rita M.; Fisher, Richard I.; LeBlanc, Michael; Maloney, David G.; Press, Oliver W.; Miller, Thomas P.; Rimsza, Lisa M.

2012-01-01

Background Fc gamma receptor polymorphisms were linked to outcome in follicular lymphoma patients treated with single-agent rituximab, an anti-CD20 monoclonal antibody. In particular, 158F/F genotype of Fc gamma receptor 3A and 131R/R genotype of Fc gamma receptor 2A correlated with worse outcome compared to high-affinity 158V/V and 131H/H, respectively. We examined this association in the context of anti-CD20 monoclonal antibody combined with chemotherapy, as compared to chemotherapy alone, in follicular lymphoma patients treated on SWOG clinical trials. Design and Methods Tissue from 142 SWOG patients treated with chemotherapy alone (protocol S8809, n=70) or combined chemotherapy and anti-CD20 monoclonal antibody (rituximab and Iodine I-131 tositumomab on protocols S9800 and S9911, n=30 and 42, respectively) was analyzed. DNA was extracted and assayed for Fc gamma receptor 3A V158F and 2A R131H polymorphisms using a TaqMan SNP assay. Stratified Cox’s regression was used to assess association with overall survival. Results For Fc gamma receptor 3A, there was an association with overall survival in the combination therapy trials but not in the chemotherapy-only trial. Having at least one Fc gamma receptor 3A V allele was associated with improved overall survival versus F/F (HR=0.33, 95% CI, 0.11, 0.96, P=0.042). For overall survival, there was evidence of a statistical interaction between the use of mAb and the number of V alleles (0, 1, or 2) (P=0.006). There was no such association for Fc gamma receptor 2A. Conclusions Fc gamma receptor 3A polymorphism status may be predictive of survival in follicular lymphoma patients receiving treatments containing an anti-CD20 antibody but not treatment with chemotherapy alone. Thus, Fc gamma receptor 3A polymorphisms may be important to consider in designing new follicular lymphoma trials and new anti-CD20 monoclonal antibodies. PMID:22271896

Chronic Mild Stress Alters Kynurenine Pathways Changing the Glutamate Neurotransmission in Frontal Cortex of Rats.

PubMed

Martín-Hernández, David; Tendilla-Beltrán, Hiram; Madrigal, José L M; García-Bueno, Borja; Leza, Juan C; Caso, Javier R

2018-05-03

Immune stimulation might be involved in the pathophysiology of major depressive disorder (MDD). This stimulation induces indoleamine 2,3-dioxygenase (IDO), an enzyme that reduces the tryptophan bioavailability to synthesize serotonin. IDO products, kynurenine metabolites, exert neurotoxic/neuroprotective actions through glutamate receptors. Thus, we study elements of these pathways linked to kynurenine metabolite activity examining whether antidepressants (ADs) can modulate them. Male Wistar rats were exposed to chronic mild stress (CMS), and some of them were treated with ADs. The expression of elements of the IDO pathway, including kynurenine metabolites, and their possible modulation by ADs was studied in the frontal cortex (FC). CMS increased IDO expression in FC compared to control group, and ADs restored the IDO expression levels to control values. CMS-induced IDO expression led to increased levels of the excitotoxic quinolinic acid (QUINA) compared to control, and ADs prevented the rise in such levels. Neither CMS nor ADs changed significantly the antiexcitotoxic kynurenic acid (KYNA) levels. The QUINA/KYNA ratio, calculated as excitotoxicity risk indicator, increased after CMS and ADs prevented this increase. CMS lowered excitatory amino acid transporter (EAAT)-1 and EAAT-4 expression, and some ADs restored their expression levels. Furthermore, CMS decreased N-methyl-D-aspartate receptor (NMDAR)-2A and 2B protein expression, and ADs mitigated this decrease. Our research examines the link between CMS-induced pro-inflammatory cytokines and the kynurenine pathway; it shows that CMS alters the kynurenine pathway in rat FC. Importantly, it also reveals the ability of classic ADs to prevent potentially harmful situations related to the brain scenario caused by CMS.

Soluble and insoluble immune complexes activate human neutrophil NADPH oxidase by distinct Fc gamma receptor-specific mechanisms.

PubMed

Crockett-Torabi, E; Fantone, J C

1990-11-01

Signal transduction initiated by interaction of immune complexes (IC) with Fc gamma RII and Fc gamma RIII receptors on human neutrophils was studied by investigating the capacity of well-defined complexes to stimulate O2- generation in neutrophils. IC consisting of polyclonal rabbit antibody to human albumin were prepared at equivalence (insoluble complexes) and at five times Ag excess (soluble complexes). Stimulation of human neutrophils with soluble and insoluble IC caused a dose-dependent activation of the respiratory burst and O2- generation. Incubation of neutrophils with cytochalasin B significantly enhanced O2- generation in neutrophils stimulated with soluble IC. In contrast, cytochalasin B treatment had a minimal effect on O2- generation in neutrophils stimulated with insoluble IC. Treatment of neutrophils with PGE1 or pertussis toxin (PTx) significantly inhibited O2- generation by soluble IC-stimulated neutrophils. However, neither PGE1 nor PTx treatment significantly altered O2- generation in neutrophils stimulated with insoluble complexes. Although O2- generation induced by soluble IC was significantly inhibited by mAb against both Fc gamma RII and Fc gamma RIII receptor, insoluble IC stimulation of neutrophil O2- generation was significantly diminished only by mAb against Fc gamma RIII receptor. Cross-linking of either Fc gamma RII or Fc gamma RIII receptors on neutrophil surfaces induced O2- generation, and this activation was inhibited by both PGE1 and PTx treatment. These findings indicate that soluble and insoluble ICs induce O2- production in human neutrophils through distinct mechanisms. Soluble IC induce activation of neutrophils through a PTx- and PGE1-sensitive pathway that is dependent upon both Fc gamma RII and Fc gamma RIII receptors. Although insoluble IC induce O2- production through a PTx and PGE1 insensitive pathway mediated primarily through Fc gamma RIII receptor.

Divergent Requirement of Fc-Fcγ Receptor Interactions for In Vivo Protection against Influenza Viruses by Two Pan-H5 Hemagglutinin Antibodies

PubMed Central

Wang, Shuangshuang; Ren, Huanhuan; Jiang, Wenbo; Chen, Honglin; Hu, Hongxing; Chen, Zhiwei

2017-01-01

ABSTRACT Recent studies have shown that Fc-Fcγ receptor (FcγR) interactions are required for in vivo protection against influenza viruses by broadly reactive anti-hemagglutinin (HA) stem, but not virus strain-specific, anti-receptor binding site (RBS), antibodies (Abs). Since only a few Abs recognizing epitopes in the head region but outside the RBS have been tested against single-challenge virus strains, it remains unknown whether Fc-FcγR interactions are required for in vivo protection by Abs recognizing epitopes outside the RBS and whether the requirement is virus strain specific or epitope specific. In the present study, we therefore investigated the requirements for in vivo protection using two pan-H5 Abs, 65C6 and 100F4. We generated chimeric Abs, 65C6/IgG2a and 100F4/IgG2a, which preferentially engage activating FcγRs, and isogenic forms, 65C6/D265A and 100F4/D265A, which do not bind FcγR. Virus neutralizing activity, binding, antibody-dependent cellular cytotoxicity (ADCC), and in vivo protection of these Abs were compared using three H5 strains, A/Shenzhen/406H/2006 (SZ06), A/chicken/Shanxi/2/2006 (SX06), and A/chicken/Netherlands/14015526/2014 (NE14). We found that all four chimeric Abs bound and neutralized the SZ06 and NE14 strains but poorly inhibited the SX06 strain. 65C6/IgG2a and 100F4/IgG2a, but not 65C6/D265A and 100F4/D265A, mediated ADCC against target cells expressing HA derived from all three virus strains. Interestingly, both 65C6/IgG2a and 65C6/D265A demonstrated comparable protection against all three virus strains in vivo; however, 100F4/IgG2a, but not 100F4/D265A, showed in vivo protection. Thus, we conclude that Fc-FcγR interactions are required for in vivo protection by 100F4, but not by 65C6, and therefore, protection is not virus strain specific but epitope specific. IMPORTANCE Abs play an important role in immune protection against influenza virus infection. Fc-FcγR interactions are required for in vivo protection by broadly neutralizing antistem, but not by virus strain-specific, anti-receptor binding site (RBS), Abs. Whether such interactions are necessary for protection by Abs that recognize epitopes outside RBS is not fully understood. In the present study, we investigated in vivo protection mechanisms against three H5 strains by two pan-H5 Abs, 65C6 and 100F4. We show that although these two Abs have similar neutralizing, binding, and ADCC activities against all three H5 strains in vitro, they have divergent requirements for Fc-FcγR interactions to protect against the three H5 strains in vivo. The Fc-FcγR interactions are required for in vivo protection by 100F4, but not by 65C6. Thus, we conclude that Fc-FcγR interactions for in vivo protection by pan-H5 Abs is not strain specific, but epitope specific. PMID:28331095

Divergent Requirement of Fc-Fcγ Receptor Interactions for In Vivo Protection against Influenza Viruses by Two Pan-H5 Hemagglutinin Antibodies.

PubMed

Wang, Shuangshuang; Ren, Huanhuan; Jiang, Wenbo; Chen, Honglin; Hu, Hongxing; Chen, Zhiwei; Zhou, Paul

2017-06-01

Recent studies have shown that Fc-Fcγ receptor (FcγR) interactions are required for in vivo protection against influenza viruses by broadly reactive anti-hemagglutinin (HA) stem, but not virus strain-specific, anti-receptor binding site (RBS), antibodies (Abs). Since only a few Abs recognizing epitopes in the head region but outside the RBS have been tested against single-challenge virus strains, it remains unknown whether Fc-FcγR interactions are required for in vivo protection by Abs recognizing epitopes outside the RBS and whether the requirement is virus strain specific or epitope specific. In the present study, we therefore investigated the requirements for in vivo protection using two pan-H5 Abs, 65C6 and 100F4. We generated chimeric Abs, 65C6/IgG2a and 100F4/IgG2a, which preferentially engage activating FcγRs, and isogenic forms, 65C6/D265A and 100F4/D265A, which do not bind FcγR. Virus neutralizing activity, binding, antibody-dependent cellular cytotoxicity (ADCC), and in vivo protection of these Abs were compared using three H5 strains, A/Shenzhen/406H/2006 (SZ06), A/chicken/Shanxi/2/2006 (SX06), and A/chicken/Netherlands/14015526/2014 (NE14). We found that all four chimeric Abs bound and neutralized the SZ06 and NE14 strains but poorly inhibited the SX06 strain. 65C6/IgG2a and 100F4/IgG2a, but not 65C6/D265A and 100F4/D265A, mediated ADCC against target cells expressing HA derived from all three virus strains. Interestingly, both 65C6/IgG2a and 65C6/D265A demonstrated comparable protection against all three virus strains in vivo ; however, 100F4/IgG2a, but not 100F4/D265A, showed in vivo protection. Thus, we conclude that Fc-FcγR interactions are required for in vivo protection by 100F4, but not by 65C6, and therefore, protection is not virus strain specific but epitope specific. IMPORTANCE Abs play an important role in immune protection against influenza virus infection. Fc-FcγR interactions are required for in vivo protection by broadly neutralizing antistem, but not by virus strain-specific, anti-receptor binding site (RBS), Abs. Whether such interactions are necessary for protection by Abs that recognize epitopes outside RBS is not fully understood. In the present study, we investigated in vivo protection mechanisms against three H5 strains by two pan-H5 Abs, 65C6 and 100F4. We show that although these two Abs have similar neutralizing, binding, and ADCC activities against all three H5 strains in vitro , they have divergent requirements for Fc-FcγR interactions to protect against the three H5 strains in vivo The Fc-FcγR interactions are required for in vivo protection by 100F4, but not by 65C6. Thus, we conclude that Fc-FcγR interactions for in vivo protection by pan-H5 Abs is not strain specific, but epitope specific. Copyright © 2017 American Society for Microbiology.

A novel pair of immunoglobulin-like receptors expressed by B cells and myeloid cells

PubMed Central

Kubagawa, Hiromi; Burrows, Peter D.; Cooper, Max D.

1997-01-01

An Fcα receptor probe of human origin was used to identify novel members of the Ig gene superfamily in mice. Paired Ig-like receptors, named PIR-A and PIR-B, are predicted from sequence analysis of the cDNAs isolated from a mouse splenic library. Both type I transmembrane proteins possess similar ectodomains with six Ig-like loops, but have different transmembrane and cytoplasmic regions. The predicted PIR-A protein has a short cytoplasmic tail and a charged Arg residue in the transmembrane region that, by analogy with the FcαR relative, suggests the potential for association with an additional transmembrane protein to form a signal transducing unit. In contrast, the PIR-B protein has an uncharged transmembrane region and a long cytoplasmic tail containing four potential immunoreceptor tyrosine-based inhibitory motifs. These features are shared by the related killer inhibitory receptors. PIR-A proteins appear to be highly variable, in that predicted peptide sequences differ for seven randomly selected PIR-A clones, whereas PIR-B cDNA clones are invariant. Southern blot analysis with PIR-B and PIR-A-specific probes suggests only one PIR-B gene and multiple PIR-A genes. The PIR-A and PIR-B genes are expressed in B lymphocytes and myeloid lineage cells, wherein both are expressed simultaneously. The characteristics of the highly-conserved PIR-A and PIR-B genes and their coordinate cellular expression suggest a potential regulatory role in humoral, inflammatory, and allergic responses. PMID:9144225

Restoration of Tumor Immune Surveillance via Targeting of IL-13Receptor-α2

PubMed Central

Fichtner-Feigl, Stefan; Terabe, Masaki; Kitani, Atsushi; Young, Cheryl A.; Fuss, Ivan; Geissler, Edward K.; Schlitt, Hans-Jürgen; Berzofsky, Jay A.; Strober, Warren

2009-01-01

In previous studies we described a “counter-immunosurveillance” mechanism initiated by tumor-activated, IL-13-producing NKT cells that signal Gr-1+ cells to produce TGF-β1, a cytokine that suppresses the activity of tumor-inhibiting cytolytic CD8+ T cells. Here we show that in two tumor models (the CT-26 metastatic colon cancer and the 15-12RM fibrosarcoma regressor models) this counter-surveillance mechanism requires the expression of a novel IL-13 receptor, IL-13Rα2, on Gr-1intermediate cells, since down-regulation of IL-13Rα2 expression or the AP-1 signal generated by the receptor via in vivo administration of specific siRNA or decoy oligonucleotides leads to loss of TGF-β1 production. Furthermore, acting on prior studies showing that IL-13Rα2 expression is induced (in part) by TNF-α, we show that receptor expression and TGF-β1 production is inhibited by administration of a TNF-α neutralizing substance, TNF-αR-Fc (etanercept). Taking advantage of this latter fact, we then demonstrate in the CT-26 model that counter-immunosurveillance could be inhibited, anti-CT-26-specific CD8+ cytolytic activity restored, and CT-26 metastatic tumor nodules greatly decreased by administration of TNF-αR-Fc. Corroborative data was obtained using the 15-12RM fibrosarcoma model. These studies point to the prevention of metastatic cancer with an available agent with already known clinically acceptable adverse effects and toxicity. PMID:18451175

Generation and characterization of a human-mouse chimeric antibody against the extracellular domain of claudin-1 for cancer therapy using a mouse model.

PubMed

Hashimoto, Yosuke; Tada, Minoru; Iida, Manami; Nagase, Shotaro; Hata, Tomoyuki; Watari, Akihiro; Okada, Yoshiaki; Doi, Takefumi; Fukasawa, Masayoshi; Yagi, Kiyohito; Kondoh, Masuo

2016-08-12

Claudin-1 (CLDN-1), an integral transmembrane protein, is an attractive target for drug absorption, prevention of infection, and cancer therapy. Previously, we generated mouse anti-CLDN-1 monoclonal antibodies (mAbs) and found that they enhanced epidermal absorption of a drug and prevented hepatitis C virus infection in human hepatocytes. Here, we investigated anti-tumor activity of a human-mouse chimeric IgG1, xi-3A2, from one of the anti-CLDN-1 mAbs, clone 3A2. Xi-3A2 accumulated in the tumor tissues in mice bearing with human CLDN-1-expressing tumor cells. Xi-3A2 activated Fcγ receptor IIIa-expressing reporter cells in the presence of human CLDN-1-expressing cells, suggesting xi-3A2 has a potential to exhibit antibody-dependent cellular cytotoxicity against CLDN-1 expressing tumor cells. We also constructed a mutant xi-3A2 antibody with Gly, Ser, and Ile substituted with Ala, Asp, and Arg at positions 236, 239, and 332 of the Fc domain. This mutant antibody showed greater activation of Fcγ receptor IIIa and in vivo anti-tumor activity in mice bearing human CLDN-1-expressing tumors than xi-3A2 did. These findings indicate that the G236A/S239D/I332E mutant of xi-3A2 might be a promising lead for tumor therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

Modulation of IgG1 immunoeffector function by glycoengineering of the GDP-fucose biosynthesis pathway.

PubMed

Kelly, Ronan M; Kowle, Ronald L; Lian, Zhirui; Strifler, Beth A; Witcher, Derrick R; Parekh, Bhavin S; Wang, Tongtong; Frye, Christopher C

2018-03-01

Cross-linking of the Fcγ receptors expressed on the surface of hematopoietic cells by IgG immune complexes triggers the activation of key immune effector mechanisms, including antibody-dependent cell mediated cytotoxicity (ADCC). A conserved N-glycan positioned at the N-terminal region of the IgG C H 2 domain is critical in maintaining the quaternary structure of the molecule for Fcγ receptor engagement. The removal of a single core fucose residue from the N-glycan results in a considerable increase in affinity for FcγRIIIa leading to an enhanced receptor-mediated immunoeffector function. The enhanced potency of the molecule translates into a number of distinct advantages in the development of IgG antibodies for cancer therapy. In an effort to significantly increase the potency of an anti-CD20, IgG1 molecule, we selectively targeted the de novo GDP-fucose biosynthesis pathway of the host CHO cell line to generate >80% afucosylated IgG1 resulting in enhanced FcγRIIIa binding (13-fold) and in vitro ADCC cell-based activity (11-fold). In addition, this effective glycoengineering strategy also allowed for the utilization of the alternate GDP-fucose salvage pathway to provide a fast and efficient mechanism to manipulate the N-glycan fucosylation level to modulate IgG immune effector function. © 2017 Wiley Periodicals, Inc.

Mast cells and company.

PubMed

Jönsson, Friederike; Daëron, Marc

2012-01-01

Classically, allergy depends on IgE antibodies and on high-affinity IgE receptors expressed by mast cells and basophils. This long accepted IgE/FcεRI/mast cell paradigm, on which the definition of immediate hypersensitivity was based in the Gell and Coomb's classification, appears too reductionist. Recently accumulated evidence indeed requires that not only IgE but also IgG antibodies, that not only FcεRI but also FcγR of the different types, that not only mast cells and basophils but also neutrophils, monocytes, macrophages, eosinophils, and other myeloid cells be considered as important players in allergy. This view markedly changes our understanding of allergic diseases and, possibly, their treatment.

The Fc and not CD4 Receptor Mediates Antibody Enhancement of HIV Infection in Human Cells

NASA Astrophysics Data System (ADS)

Homsy, Jacques; Meyer, Mia; Tateno, Masatoshi; Clarkson, Sarah; Levy, Jay A.

1989-06-01

Antibodies that enhance human immunodeficiency virus (HIV) infectivity have been found in the blood of infected individuals and in infected or immunized animals. These findings raise serious concern for the development of a safe vaccine against acquired immunodeficiency syndrome. To address the in vivo relevance and mechanism of this phenomenon, antibody-dependent enhancement of HIV infectivity in peripheral blood macrophages, lymphocytes, and human fibroblastoid cells was studied. Neither Leu3a, a monoclonal antibody directed against the CD4 receptor, nor soluble recombinant CD4 even at high concentrations prevented this enhancement. The addition of monoclonal antibody to the Fc receptor III (anti-FcRIII), but not of antibodies that react with FcRI or FcRII, inhibited HIV type 1 and HIV type 2 enhancement in peripheral blood macrophages. Although enhancement of HIV infection in CD4+ lymphocytes could not be blocked by anti-FcRIII, it was inhibited by the addition of human immunoglobulin G aggregates. The results indicate that the FcRIII receptor on human macrophages and possibly another Fc receptor on human CD4+ lymphocytes mediate antibody-dependent enhancement of HIV infectivity and that this phenomenon proceeds through a mechanism independent of the CD4 protein.

Impact of linker and conjugation chemistry on antigen binding, Fc receptor binding and thermal stability of model antibody-drug conjugates

PubMed Central

Acchione, Mauro; Kwon, Hyewon; Jochheim, Claudia M.; Atkins, William M.

2012-01-01

Antibody-drug conjugates (ADCs) with biotin as a model cargo tethered to IgG1 mAbs via different linkers and conjugation methods were prepared and tested for thermostability and ability to bind target antigen and Fc receptor. Most conjugates demonstrated decreased thermostability relative to unconjugated antibody, based on DSC, with carbohydrate and amine coupled ADCs showing the least effect compared with thiol coupled conjugates. A strong correlation between biotin-load and loss of stability is observed with thiol conjugation to one IgG scaffold, but the stability of a second IgG scaffold is relatively insensitive to biotin load. The same correlation for amine coupling was less significant. Binding of antibody to antigen and Fc receptor was investigated using surface plasmon resonance. None of the conjugates exhibited altered antigen affinity. Fc receptor FcγIIb (CD32b) interactions were investigated using captured antibody conjugate. Protein G and Protein A, known inhibitors of Fc receptor (FcR) binding to IgG, were also used to extend the analysis of the impact of conjugation on Fc receptor binding. H10NPEG4 was the only conjugate to show significant negative impact to FcR binding, which is likely due to higher biotin-load compared with the other ADCs. The ADC aHISNLC and aHISTPEG8 demonstrated some loss in affinity for FcR, but to much lower extent. The general insensitivity of target binding and effector function of the IgG1 platform to conjugation highlight their utility. The observed changes in thermostability require consideration for the choice of conjugation chemistry, depending on the system being pursued and particular application of the conjugate. PMID:22531451

Protective role of endogenous plasmalogens against hepatic steatosis and steatohepatitis in mice.

PubMed

Jang, Jung Eun; Park, Han-Sol; Yoo, Hyun Ju; Baek, In-Jeoung; Yoon, Ji Eun; Ko, Myoung Seok; Kim, Ah-Ram; Kim, Hyoun Sik; Park, Hye-Sun; Lee, Seung Eun; Kim, Seung-Whan; Kim, Su Jung; Leem, Jaechan; Kang, Yu Mi; Jung, Min Kyo; Pack, Chan-Gi; Kim, Chong Jai; Sung, Chang Ohk; Lee, In-Kyu; Park, Joong-Yeol; Fernández-Checa, José C; Koh, Eun Hee; Lee, Ki-Up

2017-08-01

Free cholesterol (FC) accumulation in the liver is an important pathogenic mechanism of nonalcoholic steatohepatitis (NASH). Plasmalogens, key structural components of the cell membrane, act as endogenous antioxidants and are primarily synthesized in the liver. However, the role of hepatic plasmalogens in metabolic liver disease is unclear. In this study, we found that hepatic levels of docosahexaenoic acid (DHA)-containing plasmalogens, expression of glyceronephosphate O-acyltransferase (Gnpat; the rate-limiting enzyme in plasmalogen biosynthesis), and expression of Pparα were lower in mice with NASH caused by accumulation of FC in the liver. Cyclodextrin-induced depletion of FC transactivated Δ-6 desaturase by increasing sterol regulatory element-binding protein 2 expression in cultured hepatocytes. DHA, the major product of Δ-6 desaturase activation, activated GNPAT, thereby explaining the association between high hepatic FC and decreased Gnpat expression. Gnpat small interfering RNA treatment significantly decreased peroxisome proliferator-activated receptor α (Pparα) expression in cultured hepatocytes. In addition to GNPAT, DHA activated PPARα and increased expression of Pparα and its target genes, suggesting that DHA in the DHA-containing plasmalogens contributed to activation of PPARα. Accordingly, administration of the plasmalogen precursor, alkyl glycerol (AG), prevented hepatic steatosis and NASH through a PPARα-dependent increase in fatty acid oxidation. Gnpat +/- mice were more susceptible to hepatic lipid accumulation and less responsive to the preventive effect of fluvastatin on NASH development, suggesting that endogenous plasmalogens prevent hepatic steatosis and NASH. Increased hepatic FC in animals with NASH decreased plasmalogens, thereby sensitizing animals to hepatocyte injury and NASH. Our findings uncover a novel link between hepatic FC and plasmalogen homeostasis through GNPAT regulation. Further study of AG or other agents that increase hepatic plasmalogen levels may identify novel therapeutic strategies against NASH. (Hepatology 2017;66:416-431). © 2017 by the American Association for the Study of Liver Diseases.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, Keng-Hsueh; Shih, Yi-Sheng; Chang, Cheng Allen

Highlights: Black-Right-Pointing-Pointer EGFR-expressing epithelial cancers account for significant portion of cancer deaths. Black-Right-Pointing-Pointer EGF-EGFR signaling pathway is validated as an important anticancer drug target. Black-Right-Pointing-Pointer EGF and Fcy fusion protein (Fcy-hEGF) can bind to EGFR and convert 5-FC to 5-FU. Black-Right-Pointing-Pointer Fcy-hEGF combined with 5-FC preferentially inhibits EGFR-expressing cells viability. -- Abstract: Human epithelial cancers account for approximately 50% of all cancer deaths. This type of cancer is characterized by excessive activation and expression of the epidermal growth factor receptor (EGFR). The EGFR pathway is critical for cancer cell proliferation, survival, metastasis and angiogenesis. The EGF-EGFR signaling pathway has beenmore » validated as an important anticancer drug target. Increasing numbers of targeted therapies against this pathway have been either approved or are currently under development. Here, we adopted a prodrug system that uses 5-fluorocytosine (5-FC) and human EGF (hEGF) fused with yeast cytosine deaminase (Fcy) to target EGFR-overexpressing cancer cells and to convert 5-FC to a significantly more toxic chemotherapeutic, 5-fluorouracil (5-FU). We cloned and purified the Fcy-hEGF fusion protein from Pichia pastoris yeast. This fusion protein specifically binds to EGFR with a similar affinity as hEGF, approximately 10 nM. Fcy-hEGF binds tightly to A431 and MDA-MB-468 cells, which overexpress EGFR, but it binds with a lower affinity to MDA-MB-231 and MCF-7, which express lower levels of EGFR. Similarly, the viability of EGFR-expressing cells was suppressed by Fcy-hEGF in the presence of increasing concentrations of 5-FC, and the IC{sub 50} values for A431 and MDA-MB-468 were approximately 10-fold lower than those of MDA-MB-231 and MCF-7. This novel prodrug system, Fcy-hEGF/5-FC, might represent a promising addition to the available class of inhibitors that specifically target EGFR-expressing cancers.« less

Modulation of Dengue/Zika Virus Pathogenicity by Antibody-Dependent Enhancement and Strategies to Protect Against Enhancement in Zika Virus Infection.

PubMed

Khandia, Rekha; Munjal, Ashok; Dhama, Kuldeep; Karthik, Kumaragurubaran; Tiwari, Ruchi; Malik, Yashpal Singh; Singh, Raj Kumar; Chaicumpa, Wanpen

2018-01-01

Antibody-dependent enhancement (ADE) is a phenomenon in which preexisting poorly neutralizing antibodies leads to enhanced infection. It is a serious concern with mosquito-borne flaviviruses such as Dengue virus (DENV) and Zika virus (ZIKV). In vitro experimental evidences have indicated the preventive, as well as a pathogenicity-enhancing role, of preexisting DENV antibodies in ZIKV infections. ADE has been confirmed in DENV but not ZIKV infections. Principally, the Fc region of the anti-DENV antibody binds with the fragment crystallizable gamma receptor (FcγR), and subsequent C1q interactions and immune effector functions are responsible for the ADE. In contrast to normal DENV infections, with ADE in DENV infections, inhibition of STAT1 phosphorylation and a reduction in IRF-1 gene expression, NOS2 levels, and RIG-1 and MDA-5 expression levels occurs. FcγRIIA is the most permissive FcγR for DENV-ADE, and under hypoxic conditions, hypoxia-inducible factor-1 alpha transcriptionally enhances expression levels of FcγRIIA, which further enhances ADE. To produce therapeutic antibodies with broad reactivity to different DENV serotypes, as well as to ZIKV, bispecific antibodies, Fc region mutants, modified Fc regions, and anti-idiotypic antibodies may be engineered. An in-depth understanding of the immunological and molecular mechanisms of DENV-ADE of ZIKV pathogenicity will be useful for the design of common and safe therapeutics and prophylactics against both viral pathogens. The present review discusses the role of DENV antibodies in modulating DENV/ZIKV pathogenicity/infection and strategies to counter ADE to protect against Zika infection.

Expression, Purification, and Biophysical Characterization of a Secreted Anthrax Decoy Fusion Protein in Nicotiana benthamiana.

PubMed

Karuppanan, Kalimuthu; Duhra-Gill, Sifti; Kailemia, Muchena J; Phu, My L; Lebrilla, Carlito B; Dandekar, Abhaya M; Rodriguez, Raymond L; Nandi, Somen; McDonald, Karen A

2017-01-04

Anthrax toxin receptor-mediated drug development for blocking anthrax toxin action has received much attention in recent decades. In this study, we produced a secreted anthrax decoy fusion protein comprised of a portion of the human capillary morphogenesis gene-2 ( CMG2 ) protein fused via a linker to the fragment crystallizable (Fc) domain of human immunoglobulin G1 in Nicotiana benthamiana plants using a transient expression system. Using the Cauliflower Mosaic Virus ( CaMV ) 35S promoter and co-expression with the p19 gene silencing suppressor, we were able to achieve a high level of recombinant CMG2-Fc-Apo (rCMG2-Fc-Apo) protein accumulation. Production kinetics were observed up to eight days post-infiltration, and maximum production of 826 mg/kg fresh leaf weight was observed on day six. Protein A affinity chromatography purification of the rCMG2-Fc-Apo protein from whole leaf extract and apoplast wash fluid showed the homodimeric form under non-reducing gel electrophoresis and mass spectrometry analysis confirmed the molecular integrity of the secreted protein. The N -glycosylation pattern of purified rCMG2-Fc-Apo protein was analysed; the major portion of N -glycans consists of complex type structures in both protein samples. The most abundant (>50%) N -glycan structure was GlcNAc₂(Xy l )Man₃(Fuc)GlcNAc₂ in rCMG2-Fc-Apo recovered from whole leaf extract and apoplast wash fluid. High mannose N -glycan structures were not detected in the apoplast wash fluid preparation, which confirmed the protein secretion. Altogether, these findings demonstrate that high-level production of rCMG2-Fc-Apo can be achieved by transient production in Nicotiana benthamiana plants with apoplast targeting.

Profilings of MicroRNAs in the Liver of Common Carp (Cyprinus carpio) Infected with Flavobacterium columnare

PubMed Central

Zhao, Lijuan; Lu, Hong; Meng, Qinglei; Wang, Jinfu; Wang, Weimin; Yang, Ling; Lin, Li

2016-01-01

MicroRNAs (miRNAs) play important roles in regulation of many biological processes in eukaryotes, including pathogen infection and host interactions. Flavobacterium columnare (FC) infection can cause great economic loss of common carp (Cyprinus carpio) which is one of the most important cultured fish in the world. However, miRNAs in response to FC infection in common carp has not been characterized. To identify specific miRNAs involved in common carp infected with FC, we performed microRNA sequencing using livers of common carp infected with and without FC. A total of 698 miRNAs were identified, including 142 which were identified and deposited in the miRbase database (Available online: http://www.mirbase.org/) and 556 had only predicted miRNAs. Among the deposited miRNAs, eight miRNAs were first identified in common carp. Thirty of the 698 miRNAs were differentially expressed miRNAs (DIE-miRNAs) between the FC infected and control samples. From the DIE-miRNAs, seven were selected randomly and their expression profiles were confirmed to be consistent with the microRNA sequencing results using RT-PCR and qRT-PCR. In addition, a total of 27,363 target genes of the 30 DIE-miRNAs were predicted. The target genes were enriched in five Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including focal adhesion, extracellular matrix (ECM)-receptor interaction, erythroblastic leukemia viral oncogene homolog (ErbB) signaling pathway, regulation of actin cytoskeleton, and adherent junction. The miRNA expression profile of the liver of common carp infected with FC will pave the way for the development of effective strategies to fight against FC infection. PMID:27092486

The Major Histocompatibility Complex–related Fc Receptor for IgG (FcRn) Binds Albumin and Prolongs Its Lifespan

PubMed Central

Chaudhury, Chaity; Mehnaz, Samina; Robinson, John M.; Hayton, William L.; Pearl, Dennis K.; Roopenian, Derry C.; Anderson, Clark L.

2003-01-01

The inverse relationship between serum albumin concentration and its half-life suggested to early workers that albumin would be protected from a catabolic fate by a receptor-mediated mechanism much like that proposed for IgG. We show here that albumin binds FcRn in a pH dependent fashion, that the lifespan of albumin is shortened in FcRn-deficient mice, and that the plasma albumin concentration of FcRn-deficient mice is less than half that of wild-type mice. These results affirm the hypothesis that the major histocompatibility complex–related Fc receptor protects albumin from degradation just as it does IgG, prolonging the half-lives of both. PMID:12566415

Ethanol Inhibits High-Affinity Immunoglobulin E Receptor (FcεRI) Signaling in Mast Cells by Suppressing the Function of FcεRI-Cholesterol Signalosome

PubMed Central

Draberova, Lubica; Paulenda, Tomas; Halova, Ivana; Potuckova, Lucie; Bugajev, Viktor; Bambouskova, Monika; Tumova, Magda; Draber, Petr

2015-01-01

Ethanol has multiple effects on biochemical events in a variety of cell types, including the high-affinity immunoglobulin E receptor (FcεRI) signaling in antigen-activated mast cells. However, the underlying molecular mechanism remains unknown. To get better understanding of the effect of ethanol on FcεRI-mediated signaling we examined the effect of short-term treatment with non-toxic concentrations of ethanol on FcεRI signaling events in mouse bone marrow-derived mast cells. We found that 15 min exposure to ethanol inhibited antigen-induced degranulation, calcium mobilization, expression of proinflammatory cytokine genes (tumor necrosis factor-α, interleukin-6, and interleukin-13), and formation of reactive oxygen species in a dose-dependent manner. Removal of cellular cholesterol with methyl-β-cyclodextrin had a similar effect and potentiated some of the inhibitory effects of ethanol. In contrast, exposure of the cells to cholesterol-saturated methyl-β-cyclodextrin abolished in part the inhibitory effect of ethanol on calcium response and production of reactive oxygen species, supporting lipid-centric theories of ethanol action on the earliest stages of mast cell signaling. Further studies showed that exposure to ethanol and/or removal of cholesterol inhibited early FcεRI activation events, including tyrosine phosphorylation of the FcεRI β and γ subunits, SYK kinases, LAT adaptor protein, phospholipase Cγ, STAT5, and AKT and internalization of aggregated FcεRI. Interestingly, ethanol alone, and particularly in combination with methyl-β-cyclodextrin, enhanced phosphorylation of negative regulatory tyrosine 507 of LYN kinase. Finally, we found that ethanol reduced passive cutaneous anaphylactic reaction in mice, suggesting that ethanol also inhibits FcεRI signaling under in vivo conditions. The combined data indicate that ethanol interferes with early antigen-induced signaling events in mast cells by suppressing the function of FcεRI-cholesterol signalosomes at the plasma membrane. PMID:26658290

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Mi; University of Chinese Academy of Sciences, Beijing 100049; Liu, Lianqing, E-mail: lqliu@sia.cn

Highlights: •Nanoscale cellular ultra-structures of macrophages were observed. •The binding affinities of FcγRs were measured directly on macrophages. •The nanoscale distributions of FcγRs were mapped on macrophages. -- Abstract: Fc gamma receptors (FcγR), widely expressed on effector cells (e.g., NK cells, macrophages), play an important role in clinical cancer immunotherapy. The binding of FcγRs to the Fc portions of antibodies that are attached to the target cells can activate the antibody-dependent cell-mediated cytotoxicity (ADCC) killing mechanism which leads to the lysis of target cells. In this work, we used atomic force microscopy (AFM) to observe the cellular ultra-structures and measuremore » the biophysical properties (affinity and distribution) of FcγRs on single macrophages in aqueous environments. AFM imaging was used to obtain the topographies of macrophages, revealing the nanoscale cellular fine structures. For molecular interaction recognition, antibody molecules were attached onto AFM tips via a heterobifunctional polyethylene glycol (PEG) crosslinker. With AFM single-molecule force spectroscopy, the binding affinities of FcγRs were quantitatively measured on single macrophages. Adhesion force mapping method was used to localize the FcγRs, revealing the nanoscale distribution of FcγRs on local areas of macrophages. The experimental results can improve our understanding of FcγRs on macrophages; the established approach will facilitate further research on physiological activities involved in antibody-based immunotherapy.« less

Escherichia coli K1 induces pterin production for enhanced expression of Fcγ receptor I to invade RAW 264.7 macrophages.

PubMed

Shanmuganathan, Muthusamy V; Krishnan, Subramanian; Fu, Xiaowei; Prasadarao, Nemani V

2014-02-01

Macrophages serve as permissive niches for Escherichia coli (E. coli) K1 to attain high grade bacteremia in the pathogenesis of meningitis in neonates. Although pterin levels are a diagnostic marker for immune activation, the role of macrophages in pterin production and in the establishment of meningitis is unknown. Here, we demonstrate that macrophages infected with E. coli K1 produce both neopterin and biopterin through increased expression of GTP-cyclohydrolase 1 (GCH1). Of note, increased production of biopterin enhances the expression of Fc-gamma receptor I (CD64), which in turn, aided the entry of E. coli K1 in macrophages while increased neopterin suppresses reactive oxygen species (ROS), thereby aiding bacterial survival. Inhibition of GCH1 by 2, 4-Diamino-6-hydroxypyrimidine (DAHP) prevented the E. coli K1 induced expression of CD64 in macrophages in vitro and the development of bacteremia in a newborn mouse model of meningitis. These studies suggest that targeting GCH1 could be therapeutic strategy for preventing neonatal meningitis by E. coli K1. Copyright © 2013 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Effects of chronic inhalation of electronic cigarettes containing nicotine on glial glutamate transporters and α-7 nicotinic acetylcholine receptor in female CD-1 mice.

PubMed

Alasmari, Fawaz; Crotty Alexander, Laura E; Nelson, Jessica A; Schiefer, Isaac T; Breen, Ellen; Drummond, Christopher A; Sari, Youssef

2017-07-03

Alteration in glutamate neurotransmission has been found to mediate the development of drug dependence, including nicotine. We and others, through using western blotting, have reported that exposure to drugs of abuse reduced the expression of glutamate transporter-1 (GLT-1) as well as cystine/glutamate antiporter (xCT), which consequently increased extracellular glutamate concentrations in the mesocorticolimbic area. However, our previous studies did not reveal any changes in glutamate/aspartate transporter (GLAST) following exposure to drugs of abuse. In the present study, for the first time, we investigated the effect of chronic exposure to electronic (e)-cigarette vapor containing nicotine, for one hour daily for six months, on GLT-1, xCT, and GLAST expression in frontal cortex (FC), striatum (STR), and hippocampus (HIP) in outbred female CD1 mice. In this study, we also investigated the expression of alpha-7 nicotinic acetylcholine receptor (α-7 nAChR), a major pre-synaptic nicotinic receptor in the glutamatergic neurons, which regulates glutamate release. We found that inhalation of e-cigarette vapor for six months increased α-7 nAChR expression in both FC and STR, but not in the HIP. In addition, chronic e-cigarette exposure reduced GLT-1 expression only in STR. Moreover, e-cigarette vapor inhalation induced downregulation of xCT in both the STR and HIP. We did not find any significant changes in GLAST expression in any brain region. Finally, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques, we detected high concentrations of nicotine and cotinine, a major metabolite of nicotine, in the FC tissues of e-cigarette exposed mice. These data provide novel evidence about the effects of chronic nicotine inhalation on the expression of key glial glutamate transporters as well as α-7 nAChR. Our work may suggest that nicotine exposure via chronic inhalation of e-cigarette vapor may be mediated in part by alterations in the glutamatergic system. Copyright © 2017 Elsevier Inc. All rights reserved.

Antibody-dependent enhancement of HIV-1 infection in human term syncytiotrophoblast cells cultured in vitro.

PubMed Central

Tóth, F D; Mosborg-Petersen, P; Kiss, J; Aboagye-Mathiesen, G; Zdravkovic, M; Hager, H; Aranyosi, J; Lampé, L; Ebbesen, P

1994-01-01

We examined if Fc receptor-mediated antibody-dependent enhancement (FcR-ADE) or complement-mediated antibody-dependent enhancement (C'-ADE) of virus infection can contribute to increasing replication of HIV-1 in human syncytiotrophoblast (ST) cells. Here we report that both FcR-ADE and C'-ADE may result in enhanced virus release from HIV-1-infected ST cells. We show that FcR-ADE of HIV-1 infection in ST cells is mediated by FcRIII and other FcR(s) belonging to undetermined Fc classes and does not require CD4 receptors, whereas C'-ADE uses both CD4 and CR2-like receptors. FcR-ADE seems to be more efficient in enhancing HIV-1 replication than C'-ADE. While FcR-ADE leads to increased internalization of HIV-1, C'-ADE does not result in enhanced endocytosis of the virus. In addition, antibodies mediating FcR-ADE are reactive with the gp120 viral envelope antigen, whereas antibodies involved in C'-ADE react with the viral transmembrane glycoprotein gp41. Data suggest that both FcR-ADE and C'-ADE may contribute to the spread of HIV-1 from mother to the fetus. PMID:8004808

Antibody-dependent enhancement of HIV-1 infection in human term syncytiotrophoblast cells cultured in vitro.

PubMed

Tóth, F D; Mosborg-Petersen, P; Kiss, J; Aboagye-Mathiesen, G; Zdravkovic, M; Hager, H; Aranyosi, J; Lampé, L; Ebbesen, P

1994-06-01

We examined if Fc receptor-mediated antibody-dependent enhancement (FcR-ADE) or complement-mediated antibody-dependent enhancement (C'-ADE) of virus infection can contribute to increasing replication of HIV-1 in human syncytiotrophoblast (ST) cells. Here we report that both FcR-ADE and C'-ADE may result in enhanced virus release from HIV-1-infected ST cells. We show that FcR-ADE of HIV-1 infection in ST cells is mediated by FcRIII and other FcR(s) belonging to undetermined Fc classes and does not require CD4 receptors, whereas C'-ADE uses both CD4 and CR2-like receptors. FcR-ADE seems to be more efficient in enhancing HIV-1 replication than C'-ADE. While FcR-ADE leads to increased internalization of HIV-1, C'-ADE does not result in enhanced endocytosis of the virus. In addition, antibodies mediating FcR-ADE are reactive with the gp120 viral envelope antigen, whereas antibodies involved in C'-ADE react with the viral transmembrane glycoprotein gp41. Data suggest that both FcR-ADE and C'-ADE may contribute to the spread of HIV-1 from mother to the fetus.

Peripheral formalin injection induces unique spinal cord microglial phenotypic changes

PubMed Central

Fu, Kai-Yuan; Tan, Yong-Hui; Sung, Backil; Mao, Jianren

2014-01-01

Microglia are resident immune cells of brain and activated by peripheral tissue injury. In the present study, we investigated the possible induction of several microglial surface immunomolecules in the spinal cord, including leukocyte common antigen (LCA/CD45), MHC class I antigen, MHC class II antigen, Fc receptor, and CD11c following formalin injection into the rat’s hind paw. CD45 and MHC class I were upregulated in the activated microglia, which was evident on day 3 with the peak expression on day 7 following peripheral formalin injection. There was a very low basal expression of MHC class II, CD11c, and the Fc receptor, which did not change after the formalin injection. These results, for the first time, indicate that peripheral formalin injection can induce phenotypic changes of microglia with distinct upregulation of CD45 and MHC class I antigen. The data suggest that phenotypic changes of the activated microglia may be a unique pattern of central changes following peripheral tissue injury. PMID:19015000

Generation of a novel artificial TrkB agonist, BM17d99, using T7 phage-displayed random peptide libraries.

PubMed

Ohnishi, Toshiyuki; Sakamoto, Kotaro; Asami-Odaka, Asano; Nakamura, Kimie; Shimizu, Ayako; Ito, Takashi; Asami, Taiji; Ohtaki, Tetsuya; Inooka, Hiroshi

2017-01-29

Tropomyosin receptor kinase B (TrkB) is a known receptor of brain-derived neurotrophic factor (BDNF). Because it plays a critical role in the regulation of neuronal development, maturation, survival, etc., TrkB is a good target for drugs against central nervous system diseases. In this study, we aimed to generate peptidic TrkB agonists by applying random peptide phage display technology. After the phage panning against recombinant Fc-fused TrkB (TrkB-Fc), agonistic phages were directly screened against TrkB-expressing HEK293 cells. Through subsequent screening of the first-hit BM17 peptide-derived focus library, we successfully obtained the BM17d99 peptide, which had no sequence similarity with BDNF but had TrkB-binding capacity. We then synthesized a dimeric BM17d99 analog peptide that could phosphorylate or activate TrkB by facilitating receptor homodimerization. Treatment of TrkB-expressing HEK293 cells with the dimeric BM17d99 analog peptide significantly induced the phosphorylation of TrkB, suggesting that homodimerization of TrkB was enhanced by the dimeric peptide. This report demonstrates that our approach is useful for the generation of artificial peptidic agonists of cell surface receptors. Copyright © 2016 Elsevier Inc. All rights reserved.

Toll-Like Receptor 2 and Mincle Cooperatively Sense Corynebacterial Cell Wall Glycolipids.

PubMed

Schick, Judith; Etschel, Philipp; Bailo, Rebeca; Ott, Lisa; Bhatt, Apoorva; Lepenies, Bernd; Kirschning, Carsten; Burkovski, Andreas; Lang, Roland

2017-07-01

Nontoxigenic Corynebacterium diphtheriae and Corynebacterium ulcerans cause invasive disease in humans and animals. Host sensing of corynebacteria is largely uncharacterized, albeit the recognition of lipoglycans by Toll-like receptor 2 (TLR2) appears to be important for macrophage activation by corynebacteria. The members of the order Corynebacterineae (e.g., mycobacteria, nocardia, and rhodococci) share a glycolipid-rich cell wall dominated by mycolic acids (termed corynomycolic acids in corynebacteria). The mycolic acid-containing cord factor of mycobacteria, trehalose dimycolate, activates the C-type lectin receptor (CLR) Mincle. Here, we show that glycolipid extracts from the cell walls of several pathogenic and nonpathogenic Corynebacterium strains directly bound to recombinant Mincle in vitro Macrophages deficient in Mincle or its adapter protein Fc receptor gamma chain (FcRγ) produced severely reduced amounts of granulocyte colony-stimulating factor (G-CSF) and of nitric oxide (NO) upon challenge with corynebacterial glycolipids. Consistently, cell wall extracts of a particular C. diphtheriae strain (DSM43989) lacking mycolic acid esters neither bound Mincle nor activated macrophages. Furthermore, TLR2 but not TLR4 was critical for sensing of cell wall extracts and whole corynebacteria. The upregulation of Mincle expression upon encountering corynebacteria required TLR2. Thus, macrophage activation by the corynebacterial cell wall relies on TLR2-driven robust Mincle expression and the cooperative action of both receptors. Copyright © 2017 American Society for Microbiology.

Toll-Like Receptor 2 and Mincle Cooperatively Sense Corynebacterial Cell Wall Glycolipids

PubMed Central

Schick, Judith; Etschel, Philipp; Bailo, Rebeca; Ott, Lisa; Bhatt, Apoorva; Lepenies, Bernd; Kirschning, Carsten

2017-01-01

ABSTRACT Nontoxigenic Corynebacterium diphtheriae and Corynebacterium ulcerans cause invasive disease in humans and animals. Host sensing of corynebacteria is largely uncharacterized, albeit the recognition of lipoglycans by Toll-like receptor 2 (TLR2) appears to be important for macrophage activation by corynebacteria. The members of the order Corynebacterineae (e.g., mycobacteria, nocardia, and rhodococci) share a glycolipid-rich cell wall dominated by mycolic acids (termed corynomycolic acids in corynebacteria). The mycolic acid-containing cord factor of mycobacteria, trehalose dimycolate, activates the C-type lectin receptor (CLR) Mincle. Here, we show that glycolipid extracts from the cell walls of several pathogenic and nonpathogenic Corynebacterium strains directly bound to recombinant Mincle in vitro. Macrophages deficient in Mincle or its adapter protein Fc receptor gamma chain (FcRγ) produced severely reduced amounts of granulocyte colony-stimulating factor (G-CSF) and of nitric oxide (NO) upon challenge with corynebacterial glycolipids. Consistently, cell wall extracts of a particular C. diphtheriae strain (DSM43989) lacking mycolic acid esters neither bound Mincle nor activated macrophages. Furthermore, TLR2 but not TLR4 was critical for sensing of cell wall extracts and whole corynebacteria. The upregulation of Mincle expression upon encountering corynebacteria required TLR2. Thus, macrophage activation by the corynebacterial cell wall relies on TLR2-driven robust Mincle expression and the cooperative action of both receptors. PMID:28483856

C-type lectin Mincle is an activating receptor for pathogenic fungus, Malassezia

PubMed Central

Yamasaki, Sho; Matsumoto, Makoto; Takeuchi, Osamu; Matsuzawa, Tetsuhiro; Ishikawa, Eri; Sakuma, Machie; Tateno, Hiroaki; Uno, Jun; Hirabayashi, Jun; Mikami, Yuzuru; Takeda, Kiyoshi; Akira, Shizuo; Saito, Takashi

2009-01-01

Mincle (also called as Clec4e and Clecsf9) is a C-type lectin receptor expressed in activated phagocytes. Recently, we have demonstrated that Mincle is an FcRγ-associated activating receptor that senses damaged cells. To search an exogenous ligand(s), we screened pathogenic fungi using cell line expressing Mincle, FcRγ, and NFAT-GFP reporter. We found that Mincle specifically recognizes the Malassezia species among 50 different fungal species tested. Malassezia is a pathogenic fungus that causes skin diseases, such as tinea versicolor and atopic dermatitis, and fatal sepsis. However, the specific receptor on host cells has not been identified. Mutation of the putative mannose-binding motif within C-type lectin domain of Mincle abrogated Malassezia recognition. Analyses of glycoconjugate microarray revealed that Mincle selectively binds to α-mannose but not mannan. Thus, Mincle may recognize specific geometry of α-mannosyl residues on Malassezia species and use this to distinguish them from other fungi. Malassezia activated macrophages to produce inflammatory cytokines/chemokines. To elucidate the physiological function of Mincle, Mincle-deficient mice were established. Malassezia-induced cytokine/chemokine production by macrophages from Mincle−/− mice was significantly impaired. In vivo inflammatory responses against Malassezia was also impaired in Mincle−/− mice. These results indicate that Mincle is the first specific receptor for Malassezia species to be reported and plays a crucial role in immune responses to this fungus. PMID:19171887

The binding of human and guinea-pig IgG subclasses to homologous macrophage and monocyte Fc receptors.

PubMed Central

Alexander, M D; Andrews, J A; Leslie, R G; Wood, N J

1978-01-01

Guinea-pig IgG2 and IgT1 bind to contiguous Fc receptors on homologous peritoneal macrophages. Equilibrium association constants determined for the binding of human IgG subclasses to homologous peripheral blood monocytes show that the order of binding is IgG1 greater than IgG3 greater than IgG4 greater than IgG2. Direct binding and rosette assay techniques independently established that both guinea-pig IgG2 and human IgG bind to homologous macrophage-monocyte Fc receptors through a site present in whole Fc (CH2. CH3)2, but absent in pFc' subfragments (CH3)2. PMID:680795

Nociceptive neuronal Fc-gamma receptor I is involved in IgG immune complex induced pain in the rat.

PubMed

Jiang, Haowu; Shen, Xinhua; Chen, Zhiyong; Liu, Fan; Wang, Tao; Xie, Yikuan; Ma, Chao

2017-05-01

Antigen-specific immune diseases such as rheumatoid arthritis are often accompanied by pain and hyperalgesia. Our previous studies have demonstrated that Fc-gamma-receptor type I (FcγRI) is expressed in a subpopulation of rat dorsal root ganglion (DRG) neurons and can be directly activated by IgG immune complex (IgG-IC). In this study we investigated whether neuronal FcγRI contributes to antigen-specific pain in the naïve and rheumatoid arthritis model rats. In vitro calcium imaging and whole-cell patch clamp recordings in dissociated DRG neurons revealed that only the small-, but not medium- or large-sized DRG neurons responded to IgG-IC. Accordingly, in vivo electrophysiological recordings showed that intradermal injection of IgG-IC into the peripheral receptive field could sensitize only the C- (but not A-) type sensory neurons and evoke action potential discharges. Pain-related behavioral tests showed that intradermal injection of IgG-IC dose-dependently produced mechanical and thermal hyperalgesia in the hindpaw of rats. These behavioral effects could be alleviated by localized administration of non-specific IgG or an FcγRI antibody, but not by mast cell stabilizer or histamine antagonist. In a rat model of antigen-induced arthritis (AIA) produced by methylated bovine serum albumin, FcγRI were found upregulated exclusively in the small-sized DRG neurons. In vitro calcium imaging revealed that significantly more small-sized DRG neurons responded to IgG-IC in the AIA rats, although there was no significant difference between the AIA and control rats in the magnitude of calcium changes in the DRG neurons. Moreover, in vivo electrophysiological recordings showed that C-nociceptive neurons in the AIA rats exhibited a greater incidence of action potential discharges and stronger responses to mechanical stimuli after IgG-IC was injected to the receptive fields. These results suggest that FcγRI expressed in the peripheral nociceptors might be directly activated by IgG-IC and contribute to antigen-specific pain in pathological conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

IgY: a key isotype in antibody evolution.

PubMed

Zhang, Xiaoying; Calvert, Rosaleen A; Sutton, Brian J; Doré, Katy A

2017-11-01

Immunoglobulin Y (IgY) is central to our understanding of immunoglobulin evolution. It has links to antibodies from the ancestral IgM to the mucosal IgX and IgA, as well as to mammalian serum IgG and IgE. IgY is found in amphibians, birds and reptiles, and as their most abundant serum antibody, is orthologous to mammalian IgG. However, IgY has the same domain architecture as IgM and IgE, lacking a hinge region and comprising four heavy-chain constant domains. The relationship between IgY and the mucosal antibodies IgX and IgA is discussed herein, in particular the question of how IgA could have contributed to the emergence of IgY. Although IgY does not contain a hinge region, amphibian IgF and duck-billed platypus IgY/O, which are closely related to IgY, do contain this region, as does mammalian IgG, IgA and IgD. A hinge region must therefore have evolved at least three times independently by convergent evolution. In the absence of three-dimensional structural information for the complete Fc fragment of chicken IgY (IgY-Fc), it remains to be discovered whether IgY displays the same conformational properties as IgM and IgE, which exhibit substantial flexibility in their Fc regions. IgY has three characterised Fc receptors, chicken Ig-like receptor AB1 (CHIR-AB1), the chicken yolk sac IgY receptor (FcRY) and Gallus gallus Fc receptor (ggFcR). These receptors bind to IgY at sites that are structurally homologous to mammalian counterparts; IgA/FcαRI for CHIR-AB1, IgG/FcRn for FcRY and IgE/FcϵRI and IgG/FcγR for ggFcR. These resemblances reflect the close evolutionary relationships between IgY and IgA, IgG and IgE. However, the evolutionary distance between birds and mammals allows for the ready generation of IgY antibodies to conserved mammalian proteins for medical and biotechnological applications. Furthermore, the lack of reactivity of IgY with mammalian Fc receptors, and the fact that large quantities of IgY can be made quickly and cheaply in chicken eggs, offers important advantages and considerable potential for IgY in research, diagnostics and therapeutics. © 2017 Cambridge Philosophical Society.

Interleukin‑12B is upregulated by decoy receptor 3 in rheumatoid synovial fibroblasts.

PubMed

Fukuda, Koji; Miura, Yasushi; Maeda, Toshihisa; Hayashi, Shinya; Kurosaka, Masahiro

2016-04-01

Decoy receptor 3 (DcR3) competitively binds to three ligands, Fas ligand, lymphotoxin‑related inducible ligand that competes for glycoprotein D binding to herpesvirus entry mediator on T cells and tumor necrosis factor‑like ligand 1A (TL1A), to prevent their effects. Recent studies have suggested that DcR3 directly affects cells as a ligand. Using a microarray assay, our group newly identified interleukin (IL)‑12B, which encodes the p40 subunit common to IL‑12 and IL‑23, as one of the genes for which expression in fibroblast‑like synoviocytes from patients with rheumatoid arthritis (RA‑FLS) is induced by DcR3. The present study demonstrated that IL‑12B mRNA expression was upregulated by DcR3‑Fc in RA‑FLS in a dose‑dependent manner, but not in OA‑FLS. IL‑12B p40 protein in RA‑FLS was increased when stimulated with DcR3‑Fc. Pre‑treatment with anti‑TL1A antibody suppressed the upregulation of IL‑12B mRNA in RA‑FLS stimulated with DcR3‑Fc. DcR3 mRNA expression in RA‑FLS was induced by IL‑23, but not by IL‑12. These results indicated that DcR3 may increase IL‑12 or IL‑23 by inducing IL‑12B p40 expression via membrane‑bound TL1A on RA‑FLS and that IL‑23 reciprocally induces DcR3 expression in RA‑FLS. DcR3 and IL‑23 may interact in a feedback loop that aggravates local inflammation in patients with RA.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sprague, E.R.; Wang, C.; Baker, D.

Herpes simplex virus type-1 expresses a heterodimeric Fc receptor, gE-gI, on the surfaces of virions and infected cells that binds the Fc region of host immunoglobulin G and is implicated in the cell-to-cell spread of virus. gE-gI binds immunoglobulin G at the basic pH of the cell surface and releases it at the acidic pH of lysosomes, consistent with a role in facilitating the degradation of antiviral antibodies. Here we identify the C-terminal domain of the gE ectodomain (CgE) as the minimal Fc-binding domain and present a 1.78-{angstrom} CgE structure. A 5-{angstrom} gE-gI/Fc crystal structure, which was independently verified bymore » a theoretical prediction method, reveals that CgE binds Fc at the C{sub H}2-C{sub H}3 interface, the binding site for several mammalian and bacterial Fc-binding proteins. The structure identifies interface histidines that may confer pH-dependent binding and regions of CgE implicated in cell-to-cell spread of virus. The ternary organization of the gE-gI/Fc complex is compatible with antibody bipolar bridging, which can interfere with the antiviral immune response.« less

HA Antibody-Mediated FcγRIIIa Activity Is Both Dependent on FcR Engagement and Interactions between HA and Sialic Acids.

PubMed

Cox, Freek; Kwaks, Ted; Brandenburg, Boerries; Koldijk, Martin H; Klaren, Vincent; Smal, Bastiaan; Korse, Hans J W M; Geelen, Eric; Tettero, Lisanne; Zuijdgeest, David; Stoop, Esther J M; Saeland, Eirikur; Vogels, Ronald; Friesen, Robert H E; Koudstaal, Wouter; Goudsmit, Jaap

2016-01-01

Interactions with receptors for the Fc region of IgG (FcγRs) have been shown to contribute to the in vivo protection against influenza A viruses provided by broadly neutralizing antibodies (bnAbs) that bind to the viral hemagglutinin (HA) stem. In particular, Fc-mediated antibody-dependent cellular cytotoxicity (ADCC) has been shown to contribute to protection by stem-binding bnAbs. Fc-mediated effector functions appear not to contribute to protection provided by strain-specific HA head-binding antibodies. We used a panel of anti-stem and anti-head influenza A and B monoclonal antibodies with identical human IgG1 Fc domains and investigated their ability to mediate ADCC-associated FcγRIIIa activation. Antibodies which do not interfere with sialic acid binding of HA can mediate FcγRIIIa activation. However, the FcγRIIIa activation was inhibited when a mutant HA, unable to bind sialic acids, was used. Antibodies which block sialic acid receptor interactions of HA interfered with FcγRIIIa activation. The inhibition of FcγRIIIa activation by HA head-binding and sialic acid receptor-blocking antibodies was confirmed in plasma samples of H5N1 vaccinated human subjects. Together, these results suggest that in addition to Fc-FcγR binding, interactions between HA and sialic acids on immune cells are required for optimal Fc-mediated effector functions by anti-HA antibodies.

SLP-76 is required for high-affinity IgE receptor- and IL-3 receptor-mediated activation of basophils.

PubMed

Hidano, Shinya; Kitamura, Daisuke; Kumar, Lalit; Geha, Raif S; Goitsuka, Ryo

2012-11-01

Basophils have been reported to play a critical role in allergic inflammation by secreting IL-4 in response to IL-3 or high-affinity IgE receptor (FcεRI)-cross-linking. However, the signaling pathways downstream of FcεRI and the IL-3 receptor in basophils have yet to be determined. In the present study, we used mice deficient in SLP-76 (Src homology 2 domain-containing leukocyte phosphoprotein of 76kDa) to demonstrate critical functions of this adaptor molecule in transducing FcεRI- and IL-3 receptor-mediated signals that induce basophil activation. Although SLP-76 was dispensable for in vivo differentiation, as well as IL-3-induced in vitro proliferation of basophils, IL-4 production induced by both stimuli was completely ablated by SLP-76 deficiency. Biochemical analyses revealed that IL-3-induced phosphorylation of phospholipase C (PLC) γ2 and Akt, but not STAT5, was severely reduced in SLP-76-deficient basophils, whereas FcεRI cross-linking phosphorylation of PLCγ2, but not Akt, was abrogated by SLP-76 deficiency, suggesting important differences in the requirement of SLP-76 for Akt activation between FcεRI- and IL-3 receptor-mediated signaling pathways in basophils. Because IL-3-induced IL-4 production was sensitive to calcineurin inhibitors and an intracellular calcium chelator, in addition to PI3K inhibitors, SLP-76 appears to regulate FcεRI- and IL-3 receptor-induced IL-4 production via mediating PLCγ2 activation in basophils. Taken together, these findings indicate that SLP-76 is an essential signaling component for basophil activation downstream of both FcεRI and the IL-3 receptor.

Distinct Fcγ receptors mediate the effect of Serum Amyloid P on neutrophil adhesion and fibrocyte differentiation

PubMed Central

Cox, Nehemiah; Pilling, Darrell; Gomer, Richard H.

2014-01-01

The plasma protein Serum Amyloid P (SAP) reduces neutrophil adhesion, inhibits the differentiation of monocytes into fibroblast-like cells called fibrocytes, and promotes phagocytosis of cell debris by macrophages. Together, these effects of SAP reduce key aspects of inflammation and fibrosis, and SAP injections improve lung function in pulmonary fibrosis patients. SAP functions are mediated in part by Fcγ receptors, but the contribution of each Fcγ receptor is not fully understood. We found that amino acids Q55 and E126 in human SAP affect human fibrocyte differentiation and SAP binding to FcγRI. E126, K130 and Q128 affect neutrophil adhesion and SAP affinity for FcγRIIa. Q128 also affects phagocytosis by macrophages and SAP affinity for FcγRI. All the identified functionally significant amino acids in SAP form a binding site that is distinct from the previously described SAP-FcγRIIa binding site. Blocking FcγRI with an IgG blocking antibody reduces the SAP effect on fibrocyte differentiation, and ligating FcγRIIa with antibodies reduces neutrophil adhesion. Together, these results suggest that SAP binds to FcγRI on monocytes to inhibit fibrocyte differentiation, and binds to FcγRIIa on neutrophils to reduce neutrophil adhesion. PMID:25024390

EphrinA1-EphA2 interaction-mediated apoptosis and Flt3L-induced immunotherapy inhibits tumor growth in a breast cancer mouse model

PubMed Central

Tandon, Manish; Vemula, Sai V.; Sharma, Anurag; Ahi, Yadvinder S.; Mittal, Shalini; Bangari, Dinesh S.; Mittal, Suresh K.

2014-01-01

Background The receptor tyrosine kinase EphA2 is overexpressed in several types of cancers and is currently being pursued as a target for breast cancer therapeutics. The EphA2 ligand EphrinA1 induces EphA2 phosphorylation and intracellular internalization and degradation, thus inhibiting tumor progression. The hematopoietic growth factor, FMS-like tyrosine kinase receptor ligand (Flt3L), promotes expansion and mobilization of functional dendritic cells. Methods We tested the EphrinA1-EphA2 interaction in MDA-MB-231 breast cancer cells focusing on the receptor-ligand-mediated apoptosis of breast cancer cells. In order to determine whether the EphrinA1-EphA2 interaction-associated apoptosis and Flt3L-mediated immunotherapy would have an additive effect in inhibiting tumor growth, we used an immunocompetent mouse model of breast cancer to evaluate intratumoral (i.t.) inoculation strategies with human adenovirus (HAd) vectors expressing either EphrinA1 (HAd-EphrinA1-Fc), Flt3L (HAd-Flt3L) or a combination of EphrinA1-Fc + Flt3L (HAd-EphrinA1-Fc + HAd-Flt3L). Results In vitro analysis demonstrated that an EphrinA1-EphA2 interaction led to apoptosis-related changes in breast cancer cells. In vivo, three i.t. inoculations of HAd-EphrinA1-Fc showed potent inhibition of tumor growth. Furthermore, increased inhibition in tumor growth was observed with the combination of HAd-EphrinA1-Fc and HAd-Flt3L accompanied by the generation of an anti-tumor adaptive immune response. Conclusions The results indicating induction of apoptosis and inhibition of mammary tumor growth show the potential therapeutic benefits of HAd-EphrinA1-Fc. In combination with HAd-Flt3L, this represents a promising strategy to effectively induce mammary tumor regression by HAd vector-based therapy. PMID:22228563

Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high-affinity receptor FcεRI.

PubMed

Sabban, Sari; Ye, Hongtu; Helm, Birgit

2014-11-01

The interaction of IgE with its high-affinity Fc receptor (FcεRI) followed by an antigenic challenge is the principal pathway in IgE mediated allergic reactions. As a consequence of the high affinity binding between IgE and FcεRI, along with the continuous production of IgE by B cells, allergies usually persist throughout life, with currently no permanent cure available. Horses, especially race horses, which are commonly inbred, are a species of mammals that are very prone to the development of hypersensitivity responses, which can seriously affect their performance. Physiological responses to allergic sensitization in horses mirror that observed in humans and dogs. In this paper we describe the development of an in situ assay system for the quantitative assessment of the release of mediators of the allergic response pertaining to the equine system. To this end, the gene encoding equine FcεRIα was transfected into and expressed onto the surface of parental Rat Basophil Leukemia (RBL-2H3.1) cells. The gene product of the transfected equine α-chain formed a functional receptor complex with the endogenous rat β- and γ-chains. The resultant assay system facilitated an assessment of the quantity of mediator secreted from equine FcεRIα transfected RBL-2H3.1 cells following sensitization with equine IgE and antigenic challenge using β-hexosaminidase release as a readout. Mediator release peaked at 36.68% ± 4.88% at 100 ng ml(-1) of antigen. This assay was modified from previous assays used to study human and canine allergic responses. We have also shown that this type of assay system has multiple applications for the development of diagnostic tools and the safety assessment of potential therapeutic intervention strategies in allergic disease.

Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high-affinity receptor FcεRI

PubMed Central

Sabban, Sari; Ye, Hongtu; Helm, Birgit

2014-01-01

The interaction of IgE with its high-affinity Fc receptor (FcεRI) followed by an antigenic challenge is the principal pathway in IgE mediated allergic reactions. As a consequence of the high affinity binding between IgE and FcεRI, along with the continuous production of IgE by B cells, allergies usually persist throughout life, with currently no permanent cure available. Horses, especially race horses, which are commonly inbred, are a species of mammals that are very prone to the development of hypersensitivity responses, which can seriously affect their performance. Physiological responses to allergic sensitization in horses mirror that observed in humans and dogs. In this paper we describe the development of an in situ assay system for the quantitative assessment of the release of mediators of the allergic response pertaining to the equine system. To this end, the gene encoding equine FcεRIα was transfected into and expressed onto the surface of parental Rat Basophil Leukemia (RBL-2H3.1) cells. The gene product of the transfected equine α-chain formed a functional receptor complex with the endogenous rat β- and γ-chains 1. The resultant assay system facilitated an assessment of the quantity of mediator secreted from equine FcεRIα transfected RBL-2H3.1 cells following sensitization with equine IgE and antigenic challenge using β-hexosaminidase release as a readout 2, 3. Mediator release peaked at 36.68% ± 4.88% at 100 ng ml-1 of antigen. This assay was modified from previous assays used to study human and canine allergic responses 4, 5. We have also shown that this type of assay system has multiple applications for the development of diagnostic tools and the safety assessment of potential therapeutic intervention strategies in allergic disease 6, 2, 3. PMID:25406512

Differential control of the tyrosine kinases Lyn and Syk by the two signaling chains of the high affinity immunoglobulin E receptor.

PubMed

Jouvin, M H; Adamczewski, M; Numerof, R; Letourneur, O; Vallé, A; Kinet, J P

1994-02-25

Nonreceptor tyrosine kinases such as the newly described 70-kDa (ZAP-70/Syk) and Src-related tyrosine kinases are coupled to a variety of receptors, including the antigen receptors on B- and T-cells and the Fc receptors for IgE (Fc epsilon RI) and IgG (Fc gamma RI, Fc gamma RIII/CD16). Various subunits of these receptors contain homologous activation motifs which appear capable of autonomously triggering cell activation. Two forms of this motif are present in the Fc epsilon RI multimeric complex: one in the beta chain and one in the gamma chain. Here we show that each of the two tyrosine kinases known to be involved in Fc epsilon RI signaling is controlled by a distinct motif-containing chain. Lyn associates with the nonactivated beta chain, whereas gamma promotes the activation of Syk. We also show that neither the beta nor the gamma motif alone can account for the full signaling capacity of the entire receptor. We propose that, upon triggering of the tetrameric receptor, Lyn already bound to beta becomes activated and phosphorylates beta and gamma; the phosphorylation of gamma induces the association of Syk with gamma and also the activation of Syk, resulting in the phosphorylation and activation of phospholipase C gamma 1. Cooperative recruitment of specific kinases by the various signaling chains found in this family of antigen receptors could represent a way to achieve the full signaling capacity of the multimeric complexes.

Association of a coding polymorphism in Fc gamma receptor 2A and graft survival in re-transplant candidates.

PubMed

Arnold, Marie-Luise; Fuernrohr, Barbara G; Weiß, Katrin M; Harre, Ulrike; Wiesener, Michael S; Spriewald, Bernd M

2015-10-01

The family of Fc gamma receptors (FcγRs) is involved in mediating immunological effector functions. FcγRs are differentially expressed on immune cells and can act either activating or inhibitory, with FcγR2A belonging to the first group. The polymorphism H131R (rs1801274) in FCGR2A has been associated with acute rejection and can shift the overall balance between activating and inhibitory FcγRs. Anti-HLA allo-antibodies in transplant recipients have been identified as risk factor for organ survival after transplantation. In this study we genotyped FCGR2A H131R in 200 patients who had undergone kidney transplantation and experienced loss of graft function. FCGR2A polymorphism was related to graft survival and anti-HLA antibodies. Graft survival was calculated as the time interval between transplantation and return to chronic dialysis after transplantation. The gene frequency of FCGR2A R/R131 was found significantly more often in patients with earlier (⩽60months) compared to patients with later (>60months) graft failure. Overall patients homozygous for R/R131 had a significantly shorter graft survival, compared to H/H131 or H/R131 which is even more pronounced, when anti-HLA antibodies were present. These data suggest, that FCGR2A polymorphisms constitute a risk factor for graft loss following kidney transplantation and that this effect is related to anti-HLA antibodies. Copyright © 2015 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

Production and characterization of soluble human TNFRI-Fc and human HO-1(HMOX1) transgenic pigs by using the F2A peptide.

PubMed

Park, Sol Ji; Cho, Bumrae; Koo, Ok Jae; Kim, Hwajung; Kang, Jung Taek; Hurh, Sunghoon; Kim, Su Jin; Yeom, Hye Jung; Moon, Joonho; Lee, Eun Mi; Choi, Ji Yei; Hong, Ju Ho; Jang, Goo; Hwang, Joing-Ik; Yang, Jaeseok; Lee, Byeong Chun; Ahn, Curie

2014-06-01

Generation of transgenic pigs for xenotransplantation is one of the most promising technologies for resolving organ shortages. Human heme oxygenase-1 (hHO-1/HMOX1) can protect transplanted organs by its strong anti-oxidative, anti-apoptotic, and anti-inflammatory effects. Soluble human TNFRI-Fc (shTNFRI-Fc) can inhibit the binding of human TNF-α (hTNF-α) to TNF receptors on porcine cells, and thereby, prevent hTNF-α-mediated inflammation and apoptosis. Herein, we successfully generated shTNFRI-Fc-F2A-HA-hHO-1 transgenic (TG) pigs expressing both shTNFRI-Fc and hemagglutinin-tagged-human heme oxygenase-1 (HA-hHO-1) by using an F2A self-cleaving peptide. shTNFRI-Fc and HA-hHO-1 transgenes containing the F2A peptide were constructed under the control of the CAG promoter. Transgene insertion and copy number in the genome of transgenic pigs was confirmed by polymerase chain reaction (PCR) and Southern blot analysis. Expressions of shTNFRI-Fc and HA-hHO-1 in TG pigs were confirmed using PCR, RT-PCR, western blot, ELISA, and immunohistochemistry. shTNFRI-Fc and HA-hHO-1 were expressed in various organs, including the heart, lung, and spleen. ELISA assays detected shTNFRI-Fc in the sera of TG pigs. For functional analysis, fibroblasts isolated from a shTNFRI-Fc-F2A-HA-hHO-1 TG pig (i.e., #14; 1 × 10(5) cells) were cultured with hTNF-α (20 ng/mL) and cycloheximide (10 μg/mL). The viability of shTNFRI-Fc-F2A-HA-hHO-1 TG pig fibroblasts was significantly higher than that of the wild type (wild type vs. shTNFRI-Fc-F2A-HA-hHO-1 TG at 24 h, 31.6 ± 3.2 vs. 60.4 ± 8.3 %, respectively; p < 0.05). Caspase-3/-7 activity of the shTNFRI-Fc-F2A-HA-hHO-1 TG pig fibroblasts was lower than that of the wild type pig fibroblasts (wild type vs. shTNFRI-Fc-F2A-HA-hHO-1 TG at 12 h, 812,452 ± 113,078 RLU vs. 88,240 ± 10,438 RLU, respectively; p < 0.05). These results show that shTNFRI-Fc and HA-hHO-1 TG pigs generated by the F2A self-cleaving peptide express both shTNFRI-Fc and HA-hHO-1 molecules, which provides protection against oxidative and inflammatory injury. Utilization of the F2A self-cleaving peptide is a promising tool for generating multiple TG pigs for xenotransplantation.

Protective effects of Fc-fused PD-L1 on two different animal models of colitis.

PubMed

Song, Mi-Young; Hong, Chun-Pyo; Park, Seong Jeong; Kim, Jung-Hwan; Yang, Bo-Gie; Park, Yunji; Kim, Sae Won; Kim, Kwang Soon; Lee, Ji Yeung; Lee, Seung-Woo; Jang, Myoung Ho; Sung, Young-Chul

2015-02-01

Programmed death-ligand 1 (PD-L1) has been shown to negatively regulate immune responses via its interaction with PD-1 receptor. In this study, we investigated the effects of PD-L1-Fc treatment on intestinal inflammation using two murine models of inflammatory colitis induced by dextran sulfate sodium (DSS) and T-cell transfer. The anti-colitis effect of adenovirus expressing Fc-conjugated PD-L1 (Ad/PD-L1-Fc) and recombinant PD-L1-Fc protein was evaluated in DSS-treated wild-type and Rag-1 knockout (KO) mice. We examined differentiation of T-helper cells, frequency of innate immune cells, and cytokine production by dendritic cells (DCs) in the colon from DSS-treated mice after PD-L1-Fc administration. In Rag-1 KO mice reconstituted with CD4 CD45RB(high) T cells, we assessed the treatment effect of PD-L1-Fc protein on the development of colitis. Administration of Ad/PD-L1-Fc significantly ameliorated DSS-induced colitis, which was accompanied by diminished frequency of interleukin (IL)-17A-producing CD4 T cells and increased interferon-γ-producing CD4 T cells in the colon of DSS-fed mice. The anti-colitic effect of PD-L1-Fc treatment was also observed in DSS-treated Rag-1 KO mice, indicating lymphoid cell independency. PD-L1-Fc modulated cytokine production by colonic DCs and the effect was dependent on PD-1 expression. Furthermore, PD-L1-Fc protein could significantly reduce the severity of colitis in CD4 CD45RB(high) T-cell-transferred Rag-1 KO mice. Based on the protective effect of PD-L1-Fc against DSS-induced and T-cell-induced colitis, our results suggest that PD-1-mediated inhibitory signals have a crucial role in limiting the development of colonic inflammation. This implicates that PD-L1-Fc may provide a novel therapeutic approach to treat inflammatory bowel disease. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Targeting Mast Cells and Basophils with Anti-FcεRIα Fab-Conjugated Celastrol-Loaded Micelles Suppresses Allergic Inflammation.

PubMed

Peng, Xia; Wang, Juan; Li, Xianyang; Lin, Lihui; Xie, Guogang; Cui, Zelin; Li, Jia; Wang, Yuping; Li, Li

2015-12-01

Mast cells and basophils are effector cells in the pathophysiology of allergic diseases. Targeted elimination of these cells may be a promising strategy for the treatment of allergic disorders. Our present study aims at targeted delivery of anti-FcεRIα Fab-conjugated celastrol-loaded micelles toward FcεRIα receptors expressed on mast cells and basophils to have enhanced anti-allergic effect. To achieve this aim, we prepared celastrol-loaded (PEO-block-PPO-block-PEO, Pluronic) polymeric nanomicelles using thin-film hydration method. The anti-FcεRIα Fab Fragment was then conjugated to carboxyl groups on drug-loaded micelles via EDC amidation reaction. The anti-FcεRIα Fab-conjugated celastrol-loaded micelles revealed uniform particle size (93.43 ± 12.93 nm) with high loading percentage (21.2 ± 1.5% w/w). The image of micelles showed oval and rod like. The anti-FcεRIα Fab-conjugated micelles demonstrated enhanced cellular uptake and cytotoxity toward target KU812 cells than non-conjugated micelles in vitro. Furthermore, diffusion of the drug into the cells allowed an efficient induction of cell apoptosis. In mouse model of allergic asthma, treatment with anti-FcεRIα Fab-conjugated micelles increased lung accumulation of micelles, and significantly reduced OVA-sIgE, histamine and Th2 cytokines (IL-4, IL-5, TNF-α) levels, eosinophils infiltration and mucus production. In addition, in mouse model of passive cutaneous anaphylaxis, anti-FcεRIα Fab-conjugated celastrol-loaded micelles treatment significantly decreased extravasated evan's in the ear. These results indicate that anti-FcεRIα Fab-conjugated celastrol-loaded micelles can target and selectively kill mast cells and basophils which express FcεRIα, and may be efficient reagents for the treatment of allergic disorders and mast cell related diseases.

Benzenediamine analog FC-99 inhibits TLR2 and TLR4 signaling in peritoneal macrophage in vitro.

PubMed

Yang, Liu; Dou, Huan; Song, Yuxian; Hou, Yayi

2016-01-01

Inflammatory bowel disease (IBD) is an inflammatory disorder, characterized by abnormally increased expression of Toll-like receptors TLR2 and TLR4 in the colon and increased pro-inflammatory cytokine production by macrophages. In the present study, we explored the effect of FC-99, a novel benzenediamine analog, on dextran sulfate sodium (DSS)-induced mouse colitis and investigated its potential mechanism. The results revealed that FC-99 improved the colon morphology and the clinical parameters in DSS-induced mouse colitis. FC-99 inhibited the increase of DSS-induced T helper cells (Th) 1 and Th17 and enhanced the number of regulatory T cells (Treg) in mesenteric lymph nodes (MLN), but had no effect on Th2 cells. FC-99 also suppressed the DSS-induced secretion of interleukin (IL)-1β, IL-6, and the tumor necrosis factor (TNF)-α in the colon and hindered the infiltration of macrophages into colon lamina propria. Flow cytometric analysis also confirmed that FC-99 reduced CD11b(+)F4/80(+) colon macrophages, and down-regulated TNF-α level in situ. Moreover, FC-99 inhibited concentration-dependently the expression of TNF-α and IL-6 in vitro from mouse peritoneal macrophages, which were induced by TLR ligands: PamCSK4 and peptidoglycan (PGN, TLR2 ligand) as well as LPS (TLR4 ligand). Of note, FC-99 also suppressed the activation of TLR2 and TLR4 signaling pathways and the downstream nuclear factor-κB (NF-κB) in the DSS-induced mouse colitis. FC-99 improved the condition of DSS-induced mouse colitis by inhibiting the activation of TLR2 and TLR4 signaling pathways in macrophage. These results suggest that FC-99 may be developed as a new therapeutic drug for IBD. Copyright © 2015 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Jinghua; Marnell, Lorraine L.; Marjon, Kristopher D.

Pentraxins are a family of ancient innate immune mediators conserved throughout evolution. The classical pentraxins include serum amyloid P component (SAP) and C-reactive protein, which are two of the acute-phase proteins synthesized in response to infection. Both recognize microbial pathogens and activate the classical complement pathway through C1q. More recently, members of the pentraxin family were found to interact with cell-surface Fc{gamma} receptors (Fc{gamma}R) and activate leukocyte-mediated phagocytosis. Here we describe the structural mechanism for pentraxin's binding to Fc{gamma}R and its functional activation of Fc{gamma}R-mediated phagocytosis and cytokine secretion. The complex structure between human SAP and Fc{gamma}RIIa reveals a diagonallymore » bound receptor on each SAP pentamer with both D1 and D2 domains of the receptor contacting the ridge helices from two SAP subunits. The 1:1 stoichiometry between SAP and Fc{gamma}RIIa infers the requirement for multivalent pathogen binding for receptor aggregation. Mutational and binding studies show that pentraxins are diverse in their binding specificity for Fc{gamma}R isoforms but conserved in their recognition structure. The shared binding site for SAP and IgG results in competition for Fc{gamma}R binding and the inhibition of immune-complex-mediated phagocytosis by soluble pentraxins. These results establish antibody-like functions for pentraxins in the Fc{gamma}R pathway, suggest an evolutionary overlap between the innate and adaptive immune systems, and have new therapeutic implications for autoimmune diseases.« less

Decoy receptor 3 down-regulates centrosomal protein 70 kDa specifically in rheumatoid synovial fibroblasts.

PubMed

Fukuda, Koji; Miura, Yasushi; Maeda, Toshihisa; Hayashi, Shinya; Kuroda, Ryosuke

2018-03-01

Decoy receptor 3 (DcR3) competitively binds to Fas ligand, lymphotoxin-related inducible ligand that competes for glycoprotein D binding to herpes virus entry mediator on T cells (LIGHT) and TNF-like ligand 1A (TL1A), thereby preventing their effects. Using a microarray assay, we previously newly identified centrosomal protein 70 kDa (CEP70) as one of the genes whose expression in fibroblast-like synoviocytes from patients with rheumatoid arthritis (RA-FLS) is reduced by DcR3. Here, we investigated the significance of DcR3 regulation of CEP70 for RA-FLS. Synovial samples were obtained from RA patients who had never been treated with biologics and from osteoarthritis (OA) patients. CEP70 mRNA expression was quantified using RT-qPCR analysis. CEP70 protein expression was assessed using immunohistochemical and western blot analyses. CEP70 was expressed predominantly in the superficial lining layer in RA synovial tissue. CEP70 expression was dose-dependently downregulated by DcR3-Fc in RA-FLS but was not downregulated in OA-FLS. TL1A antibody prevented the DcR3-Fc inhibitory effects on CEP70 expression in RA-FLS. These results indicated that DcR3 reduces CEP70 expression in RA-FLS by binding to membrane-bound TL1A and may suppress RA-FLS proliferation. The reduction in CEP70 expression by DcR3/TL1A signaling may control the hyperplasia of RA synovium.

Structural characterization of the Man5 glycoform of human IgG3 Fc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shah, Ishan S.; Lovell, Scott; Mehzabeen, Nurjahan

Immunoglobulin G (IgG) consists of four subclasses in humans: IgG1, IgG2, IgG3 and IgG4, which are highly conserved but have unique differences that result in subclass-specific effector functions. Though IgG1 is the most extensively studied IgG subclass, study of other subclasses is important to understand overall immune function and for development of new therapeutics. When compared to IgG1, IgG3 exhibits a similar binding profile to Fcγ receptors and stronger activation of complement. All IgG subclasses are glycosylated at N297, which is required for Fcγ receptor and C1q complement binding as well as maintaining optimal Fc conformation. We have determined themore » crystal structure of homogenously glycosylated human IgG3 Fc with a GlcNAc2Man5 (Man5) high mannose glycoform at 1.8 Å resolution and compared its structural features with published structures from the other IgG subclasses. Although the overall structure of IgG3 Fc is similar to that of other subclasses, some structural perturbations based on sequence differences were revealed. For instance, the presence of R435 in IgG3 (and H435 in the other IgG subclasses) has been implicated to result in IgG3-specific properties related to binding to protein A, protein G and the neonatal Fc receptor (FcRn). The IgG3 Fc structure helps to explain some of these differences. Additionally, protein-glycan contacts observed in the crystal structure appear to correlate with IgG3 affinity for Fcγ receptors as shown by binding studies with IgG3 Fc glycoforms. Finally, this IgG3 Fc structure provides a template for further studies aimed at engineering the Fc for specific gain of function.« less

The differentiation and isolation of mouse embryonic stem cells toward hepatocytes using galactose-carrying substrata.

PubMed

Meng, Qingyuan; Haque, Amranul; Hexig, Bayar; Akaike, Toshihiro

2012-02-01

A simple culture system to achieve the differentiation of embryonic stem (ES) cells toward hepatocytes with high efficiency is crucial in providing a cell source for the medical application. In this study, we report the effect of a matrix-dependent enrichment of ES cell-derived hepatocytes using immobilized poly(N-p-vinylbenzyl-4-O-β-D-galactopyranosyl-D-gluconamide) (PVLA) with E-cadherin-IgG Fc (E-cad-Fc) as a galactose-carrying substratum. PVLA and E-cad-Fc were confirmed to be stably co-adsorbed onto polystyrene surface by quartz crystal microbalance (QCM). We showed that the E-cad-Fc/PVLA hybrid substratum was efficient in culturing primary hepatocytes and maintaining liver functions, on which the undifferentiated ES cells also maintained high proliferative capability. Furthermore, ES cell-derived hepatocytes on this hybrid matrix expressed elevated level of liver specific genes and functions together with early expression of definitive hepatocyte marker, asialoglycoprotein receptor (ASGPR). Finally, we isolated a high percentage of cells (about 60%) with ASGPR expression after re-seeding onto PVLA-coated surface, and observed the elimination of the poorly differentiated cells (Gata6(+) and Sox17(+)) and the ones toward another cell lineage (brachyury(+) and Pdx1(+)). The system uses a glycopolymer as an extracellular substratum for isolation and enrichment of ES cell-derived hepatocytes with adequate homogeneity and functionality. Copyright © 2011 Elsevier Ltd. All rights reserved.

Postneonatal Mortality and Liver Changes in Cloned Pigs Associated with Human Tumor Necrosis Factor Receptor I-Fc and Human Heme Oxygenase-1 Overexpression

PubMed Central

Kim, Geon A.; Jin, Jun-Xue; Lee, Sanghoon; Taweechaipaisankul, Anukul; Oh, Hyun Ju; Hwang, Joing-Ik; Ahn, Curie

2017-01-01

Soluble human tumor necrosis factor (shTNFRI-Fc) and human heme oxygenase 1 (hHO-1) are key regulators for protection against oxidative and inflammatory injury for xenotransplantation. Somatic cells with more than 10 copy numbers of shTNFRI-Fc and hHO-1 were employed in somatic cell nuclear transfer to generate cloned pigs, thereby resulting in seven cloned piglets. However, produced piglets were all dead within 24 hours after birth. Obviously, postnatal death with liver apoptosis was reported in the higher copy number of shTNFRI-Fc and hHO-1 piglets. In liver, the transcript levels of ferritin heavy chain, light chain, transferrin, and inducible nitric oxide synthase were significantly highly expressed compared to those of lower copy number of shTNFRI-Fc and hHO-1 piglets (P < 0.05). Also, H2O2 contents were increased, and superoxide dismutase was significantly lower in the higher copy number of shTNFRI-Fc and hHO-1 piglets (P < 0.05). These results indicate that TNFRI-Fc and hHO-1 overexpression may apparently induce free iron in the liver and exert oxidative stress by enhancing reactive oxygen species production and block normal postneonatal liver metabolism. PMID:28503569

Postneonatal Mortality and Liver Changes in Cloned Pigs Associated with Human Tumor Necrosis Factor Receptor I-Fc and Human Heme Oxygenase-1 Overexpression.

PubMed

Kim, Geon A; Jin, Jun-Xue; Lee, Sanghoon; Taweechaipaisankul, Anukul; Oh, Hyun Ju; Hwang, Joing-Ik; Ahn, Curie; Saadeldin, Islam M; Lee, Byeong Chun

2017-01-01

Soluble human tumor necrosis factor (shTNFRI-Fc) and human heme oxygenase 1 (hHO-1) are key regulators for protection against oxidative and inflammatory injury for xenotransplantation. Somatic cells with more than 10 copy numbers of shTNFRI-Fc and hHO-1 were employed in somatic cell nuclear transfer to generate cloned pigs, thereby resulting in seven cloned piglets. However, produced piglets were all dead within 24 hours after birth. Obviously, postnatal death with liver apoptosis was reported in the higher copy number of shTNFRI-Fc and hHO-1 piglets. In liver, the transcript levels of ferritin heavy chain, light chain, transferrin, and inducible nitric oxide synthase were significantly highly expressed compared to those of lower copy number of shTNFRI-Fc and hHO-1 piglets ( P < 0.05). Also, H 2 O 2 contents were increased, and superoxide dismutase was significantly lower in the higher copy number of shTNFRI-Fc and hHO-1 piglets ( P < 0.05). These results indicate that TNFRI-Fc and hHO-1 overexpression may apparently induce free iron in the liver and exert oxidative stress by enhancing reactive oxygen species production and block normal postneonatal liver metabolism.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wurzburg, Beth A; Jardetzky, Theodore S; Stanford)

The structure of immunoglobulin E (IgE)-Fc 3-4 has been solved in three new crystal forms, providing 13 snapshots of the Fc conformation and revealing a diverse range of open-closed motions among subunit chains and dimers. A more detailed analysis of the open-to-closed motion of IgE-Fc 3-4 was possible with so many structures, and the new structures allow a more thorough examination of the flexibility of IgE-Fc and its implications for receptor binding. The existence of a hydrophobic pocket at the elbow region of the Fc appears to be conformation dependent and suggests a means of regulating the IgE-Fc conformation (andmore » potentially receptor binding) with small molecules.« less

The Impact of HLA Class I-Specific Killer Cell Immunoglobulin-Like Receptors on Antibody-Dependent Natural Killer Cell-Mediated Cytotoxicity and Organ Allograft Rejection.

PubMed

Rajalingam, Raja

2016-01-01

Natural killer (NK) cells of the innate immune system are cytotoxic lymphocytes that play an important roles following transplantation of solid organs and hematopoietic stem cells. Recognition of self-human leukocyte antigen (HLA) class I molecules by inhibitory killer cell immunoglobulin-like receptors (KIRs) is involved in the calibration of NK cell effector capacities during the developmental stage, allowing the subsequent recognition and elimination of target cells with decreased expression of self-HLA class I (due to virus infection or tumor transformation) or HLA class I disparities (in the setting of allogeneic transplantation). NK cells expressing an inhibitory KIR-binding self-HLA can be activated when confronted with allografts lacking a ligand for the inhibitory receptor. Following the response of the adaptive immune system, NK cells can further destroy allograft endothelium by antibody-dependent cell-mediated cytotoxicity (ADCC), triggered through cross-linking of the CD16 Fc receptor by donor-specific antibodies bound to allograft. Upon recognizing allogeneic target cells, NK cells also secrete cytokines and chemokines that drive maturation of dendritic cells to promote cellular and humoral adaptive immune responses against the allograft. The cumulative activating and inhibitory signals generated by ligation of the receptors regulates mature NK cell killing of target cells and their production of cytokines and chemokines. This review summarizes the role of NK cells in allograft rejection and proposes mechanistic concepts that indicate a prominent role for KIR-HLA interactions in facilitating NK cells for Fc receptor-mediated ADCC effector function involved in antibody-mediated rejection of solid organ transplants.

Use of LDL receptor-targeting peptide vectors for in vitro and in vivo cargo transport across the blood-brain barrier.

PubMed

Molino, Yves; David, Marion; Varini, Karine; Jabès, Françoise; Gaudin, Nicolas; Fortoul, Aude; Bakloul, Karima; Masse, Maxime; Bernard, Anne; Drobecq, Lucile; Lécorché, Pascaline; Temsamani, Jamal; Jacquot, Guillaume; Khrestchatisky, Michel

2017-05-01

The blood-brain barrier (BBB) prevents the entry of many drugs into the brain and, thus, is a major obstacle in the treatment of CNS diseases. There is some evidence that the LDL receptor (LDLR) is expressed at the BBB and may participate in the transport of endogenous ligands from blood to brain, a process referred to as receptor-mediated transcytosis. We previously described a family of peptide vectors that were developed to target the LDLR. In the present study, in vitro BBB models that were derived from wild-type and LDLR-knockout animals ( ldlr -/- ) were used to validate the specific LDLR-dependent transcytosis of LDL via a nondegradative route. We next showed that LDLR-targeting peptide vectors, whether in fusion or chemically conjugated to an Ab Fc fragment, promote binding to apical LDLR and transendothelial transfer of the Fc fragment across BBB monolayers via the same route as LDL. Finally, we demonstrated in vivo that LDLR significantly contributes to the brain uptake of vectorized Fc. We thus provide further evidence that LDLR is a relevant receptor for CNS drug delivery via receptor-mediated transcytosis and that the peptide vectors we developed have the potential to transport drugs, including proteins or Ab based, across the BBB.-Molino, Y., David, M., Varini, K., Jabès, F., Gaudin, N., Fortoul, A., Bakloul, K., Masse, M., Bernard, A., Drobecq, L., Lécorché, P., Temsamani, J., Jacquot, G., Khrestchatisky, M. Use of LDL receptor-targeting peptide vectors for in vitro and in vivo cargo transport across the blood-brain barrier. © FASEB.

Fc receptors for mouse IgG1 on human monocytes: polymorphism and role in antibody-induced T cell proliferation.

PubMed

Tax, W J; Hermes, F F; Willems, R W; Capel, P J; Koene, R A

1984-09-01

In previous studies, it was shown that there is polymorphism in the mitogenic effect of mouse IgG1 monoclonal antibodies against the T3 antigen of human T cells. This polymorphism implies that IgG1 anti-T3 antibodies are not mitogenic for T cells from 30% of healthy individuals. The present results demonstrate that this polymorphism is caused by polymorphism of an Fc receptor for mouse IgG1, present on human monocytes. The Fc receptor for murine IgG1 could be detected by a newly developed rosetting assay on monocytes from all individuals responsive to the mitogenic effect of IgG1 anti-T3 antibodies. This Fc receptor was not detectable on monocytes from those individuals exhibiting no mitogenic responses to IgG1 anti-T3 monoclonal antibodies. Cross-linking of T3 antigens appears to be essential for antibody-induced mitosis of T cells, because mononuclear cells that did not proliferate in response to WT 31 (an IgG1 antibody against T3 antigen) showed a proliferative response to Sepharose beads coated with WT 31. The Fc receptor--if functionally present--may be involved in the cross-linking of T3 antigens through anti-T3 antibodies. Further evidence for the involvement of this Fc receptor in antibody-induced T cell proliferation was provided by inhibition studies. Immune complexes containing IgG1 antibodies were able to inhibit the proliferative response to IgG1 anti-T3 antibodies. This inhibition by immune complexes appears to be mediated through the monocyte Fc receptor for mouse IgG1. These findings are important for the interpretation of previously described inhibitory effects of anti-T cell monoclonal antibodies on T cell proliferation, and show that such inhibitory effects may be monocyte-mediated (via immune complexes) rather than caused by a direct involvement of the respective T cell antigens in T cell mitosis. The Fc receptor for mouse IgG1 plays a role in antibody-induced T cell proliferation. Its polymorphism may have important implications for the therapeutic use of IgG1 monoclonal antibodies.

Structural and Physical Basis for Anti-IgE Therapy

NASA Astrophysics Data System (ADS)

Wright, Jon D.; Chu, Hsing-Mao; Huang, Chun-Hsiang; Ma, Che; Wen Chang, Tse; Lim, Carmay

2015-06-01

Omalizumab, an anti-IgE antibody, used to treat severe allergic asthma and chronic idiopathic urticaria, binds to IgE in blood or membrane-bound on B lymphocytes but not to IgE bound to its high (FcɛRI) or low (CD23) affinity receptor. Mutagenesis studies indicate overlapping FcɛRI and omalizumab-binding sites in the Cɛ3 domain, but crystallographic studies show FcɛRI and CD23-binding sites that are far apart, so how can omalizumab block IgE from binding both receptors? We report a 2.42-Å omalizumab-Fab structure, a docked IgE-Fc/omalizumab-Fab structure consistent with available experimental data, and the free energy contributions of IgE residues to binding omalizumab, CD23, and FcɛRI. These results provide a structural and physical basis as to why omalizumab cannot bind receptor-bound IgE and why omalizumab-bound IgE cannot bind to CD23/FcɛRI. They reveal the key IgE residues and their roles in binding omalizumab, CD23, and FcɛRI.

Glucocorticoid-induced tumor necrosis factor receptor family-related ligand triggering upregulates vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 and promotes leukocyte adhesion.

PubMed

Lacal, Pedro Miguel; Petrillo, Maria Grazia; Ruffini, Federica; Muzi, Alessia; Bianchini, Rodolfo; Ronchetti, Simona; Migliorati, Graziella; Riccardi, Carlo; Graziani, Grazia; Nocentini, Giuseppe

2013-10-01

The interaction of glucocorticoid-induced tumor necrosis factor receptor-family related (GITR) protein with its ligand (GITRL) modulates different functions, including immune/inflammatory response. These effects are consequent to intracellular signals activated by both GITR and GITRL. Previous results have suggested that lack of GITR expression in GITR(-/-) mice decreases the number of leukocytes within inflamed tissues. We performed experiments to analyze whether the GITRL/GITR system modulates leukocyte adhesion and extravasation. For that purpose, we first evaluated the capability of murine splenocytes to adhere to endothelial cells (EC). Our results indicated that adhesion of GITR(-/-) splenocytes to EC was reduced as compared with wild-type cells, suggesting that GITR plays a role in adhesion and that this effect may be due to GITRL-GITR interaction. Moreover, adhesion was increased when EC were pretreated with an agonist GITR-Fc fusion protein, thus indicating that triggering of GITRL plays a role in adhesion by EC regulation. In a human in vitro model, the adhesion to human EC of HL-60 cells differentiated toward the monocytic lineage was increased by EC pretreatment with agonist GITR-Fc. Conversely, antagonistic anti-GITR and anti-GITRL Ab decreased adhesion, thus further indicating that GITRL triggering increases the EC capability to support leukocyte adhesion. EC treatment with GITR-Fc favored extravasation, as demonstrated by a transmigration assay. Notably, GITRL triggering increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression and anti-ICAM-1 and anti-VCAM-1 Abs reversed GITR-Fc effects. Our study demonstrates that GITRL triggering in EC increases leukocyte adhesion and transmigration, suggesting new anti-inflammatory therapeutic approaches based on inhibition of GITRL-GITR interaction.

Cell surface control of the multiubiquitination and deubiquitination of high-affinity immunoglobulin E receptors.

PubMed Central

Paolini, R; Kinet, J P

1993-01-01

Multiubiquitination of proteins is a critical step leading to selective degradation for many polypeptides. Therefore, activation-induced multiubiquitination of cell surface receptors, such as the platelet-derived growth factor (PDGF) receptor and the T cell antigen (TCR) receptor, may correspond to a degradation pathway for ligand-receptor complexes. Here we show that the antigen-induced engagement of high-affinity immunoglobulin E receptors (Fc epsilon RI) results in the immediate multiubiquitination of Fc epsilon RI beta and gamma chains. This ubiquitination is independent of receptor phosphorylation and is restricted to activated receptors. Surprisingly, receptor multiubiquitination is immediately reversible when receptors are disengaged. Therefore, multiubiquitination and deubiquitination of Fc epsilon RI receptors is controlled at the cell surface by receptor engagement and disengagement. The rapidity, specificity and, most importantly, the reversibility of the activation-induced receptor multiubiquitination suggest that this process may turn on/off a cell surface receptor signaling function thus far unsuspected. Images PMID:8382611

Accelerated Disassembly of IgE:Receptor Complexes by a Disruptive Macromolecular Inhibitor

PubMed Central

Kim, Beomkyu; Eggel, Alexander; Tarchevskaya, Svetlana S.; Vogel, Monique; Prinz, Heino; Jardetzky, Theodore S.

2012-01-01

IgE antibodies bind the high affinity IgE Fc receptor (FcεRI), found primarily on mast cells and basophils, and trigger inflammatory cascades of the allergic response1,2. Inhibitors of IgE:FcεRI binding have been identified and an anti-IgE therapeutic antibody (omalizumab) is used to treat severe allergic asthma3,4. However, preformed IgE:FcεRI complexes that prime cells prior to allergen exposure dissociate extremely slowly5 and cannot be disrupted by strictly competitive inhibitors. IgE-Fc conformational flexibility indicated that inhibition could be mediated by allosteric or other non-classical mechanisms6–8. Here we demonstrate that an engineered protein inhibitor, DARPin E2_799–11, acts through a non-classical inhibition mechanism, not only blocking IgE:FcεRI interactions, but actively stimulating the dissociation of preformed ligand-receptor complexes. The structure of the E2_79:IgE-Fc3-4 complex predicts the presence of two non-equivalent E2_79 sites in the asymmetric IgE:FcεRI complex, with Site 1 distant from the receptor and Site 2 exhibiting partial steric overlap. While the structure is suggestive of an allosteric inhibition mechanism, mutational studies and quantitative kinetic modeling indicate that E2_79 acts through a facilitated dissociation mechanism at Site 2 alone. These results demonstrate that high affinity IgE:FcεRI complexes can be actively dissociated to block the allergic response and suggest that protein:protein complexes may be more generally amenable to active disruption by macromolecular inhibitors. PMID:23103871

Neonatal Fc receptor for IgG (FcRn) regulates cross-presentation of IgG immune complexes by CD8−CD11b+ dendritic cells

PubMed Central

Baker, Kristi; Qiao, Shuo-Wang; Kuo, Timothy T.; Aveson, Victoria G.; Platzer, Barbara; Andersen, Jan-Terje; Sandlie, Inger; Chen, Zhangguo; de Haar, Colin; Lencer, Wayne I.; Fiebiger, Edda; Blumberg, Richard S.

2011-01-01

Cross-presentation of IgG-containing immune complexes (ICs) is an important means by which dendritic cells (DCs) activate CD8+ T cells, yet it proceeds by an incompletely understood mechanism. We show that monocyte-derived CD8−CD11b+ DCs require the neonatal Fc receptor for IgG (FcRn) to conduct cross-presentation of IgG ICs. Consequently, in the absence of FcRn, Fcγ receptor (FcγR)-mediated antigen uptake fails to initiate cross-presentation. FcRn is shown to regulate the intracellular sorting of IgG ICs to the proper destination for such cross-presentation to occur. We demonstrate that FcRn traps antigen and protects it from degradation within an acidic loading compartment in association with the rapid recruitment of key components of the phagosome-to-cytosol cross-presentation machinery. This unique mechanism thus enables cross-presentation to evolve from an atypically acidic loading compartment. FcRn-driven cross-presentation is further shown to control cross-priming of CD8+ T-cell responses in vivo such that during chronic inflammation, FcRn deficiency results in inadequate induction of CD8+ T cells. These studies thus demonstrate that cross-presentation in CD8−CD11b+ DCs requires a two-step mechanism that involves FcγR-mediated internalization and FcRn-directed intracellular sorting of IgG ICs. Given the centrality of FcRn in controlling cross-presentation, these studies lay the foundation for a unique means to therapeutically manipulate CD8+ T-cell responses. PMID:21628593

Bimolecular fluorescence complementation: lighting up seven transmembrane domain receptor signalling networks

PubMed Central

Rose, Rachel H; Briddon, Stephen J; Holliday, Nicholas D

2010-01-01

There is increasing complexity in the organization of seven transmembrane domain (7TM) receptor signalling pathways, and in the ability of their ligands to modulate and direct this signalling. Underlying these events is a network of protein interactions between the 7TM receptors themselves and associated effectors, such as G proteins and β-arrestins. Bimolecular fluorescence complementation, or BiFC, is a technique capable of detecting these protein–protein events essential for 7TM receptor function. Fluorescent proteins, such as those from Aequorea victoria, are split into two non-fluorescent halves, which then tag the proteins under study. On association, these fragments refold and regenerate a mature fluorescent protein, producing a BiFC signal indicative of complex formation. Here, we review the experimental criteria for successful application of BiFC, considered in the context of 7TM receptor signalling events such as receptor dimerization, G protein and β-arrestin signalling. The advantages and limitations of BiFC imaging are compared with alternative resonance energy transfer techniques. We show that the essential simplicity of the fluorescent BiFC measurement allows high-content and advanced imaging applications, and that it can probe more complex multi-protein interactions alone or in combination with resonance energy transfer. These capabilities suggest that BiFC techniques will become ever more useful in the analysis of ligand and 7TM receptor pharmacology at the molecular level of protein–protein interactions. This article is part of a themed section on Imaging in Pharmacology. To view the editorial for this themed section visit http://dx.doi.org/10.1111/j.1476-5381.2010.00685.x PMID:20015298

The neonatal Fc receptor, FcRn, as a target for drug delivery and therapy.

PubMed

Sockolosky, Jonathan T; Szoka, Francis C

2015-08-30

Immunoglobulin G (IgG)-based drugs are arguably the most successful class of protein therapeutics due in part to their remarkably long blood circulation. This arises from IgG interaction with the neonatal Fc receptor, FcRn. FcRn is the central regulator of IgG and albumin homeostasis throughout life and is increasingly being recognized as an important player in autoimmune disease, mucosal immunity, and tumor immune surveillance. Various engineering approaches that hijack or disrupt the FcRn-mediated transport pathway have been devised to develop long-lasting and non-invasive protein therapeutics, protein subunit vaccines, and therapeutics for treatment of autoimmune and infectious disease. In this review, we highlight the diverse biological functions of FcRn, emerging therapeutic opportunities, as well as the associated challenges of targeting FcRn for drug delivery and disease therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

Rho is Required for the Initiation of Calcium Signaling and Phagocytosis by Fcγ Receptors in Macrophages

PubMed Central

Hackam, David J.; Rotstein, Ori D.; Schreiber, Alan; Zhang, Wei-jian; Grinstein, Sergio

1997-01-01

Phagocytosis of bacteria by macrophages and neutrophils is an essential component of host defense against infection. The mechanism whereby the interaction of opsonized particles with Fcγ receptors triggers the engulfment of opsonized particles remains incompletely understood, although activation of tyrosine kinases has been recognized as an early step. Recent studies in other systems have demonstrated that tyrosine kinases can in turn signal the activation of small GTPases of the ras superfamily. We therefore investigated the possible role of Rho in Fc receptor–mediated phagocytosis. To this end we microinjected J774 macrophages with C3 exotoxin from Clostridium botulinum, which ADP-ribosylates and inactivates Rho. C3 exotoxin induced the retraction of filopodia, the disappearance of focal complexes, and a global decrease in the F-actin content of J774 cells. In addition, these cells exhibited increased spreading and the formation of vacuolar structures. Importantly, inactivation of Rho resulted in the complete abrogation of phagocytosis. Inhibition of Fcγ receptor–mediated phagocytosis by C3 exotoxin was confirmed in COS cells, which become phagocytic upon transfection of the FcγRIIA receptor. Rho was found to be essential for the accumulation of phosphotyrosine and of F-actin around phagocytic cups and for Fcγ receptor–mediated Ca2+ signaling. The clustering of receptors in response to opsonin, an essential step in Fcγ-induced signaling, was the earliest event shown to be inhibited by C3 exotoxin. The effect of the toxin was specific, since clustering and internalization of transferrin receptors were unaffected by microinjection of C3. These data identify a role for small GTPases in Fcγ receptor–mediated phagocytosis by leukocytes. PMID:9294149

NK Cell–Mediated Antitumor Effects of a Folate-Conjugated Immunoglobulin are Enhanced by Cytokines

PubMed Central

Kondadasula, SriVidya; Skinner, Cassandra C.; Mundy-Bosse, Bethany L.; Luedke, Eric; Jones, Natalie B.; Mani, Aruna; Roda, Julie; Karpa, Volodymyr; Li, Hong; Li, Jilong; Elavazhagan, Saranya; La Perle, Krista M.; Schmitt, Alessandra C.; Lu, Yanhui; Zhang, Xiaoli; Pan, Xueliang; Mao, Hsaioyin; Davis, Melanie; Jarjoura, David; Butchar, Jonathan P.; Poi, Ming; Phelps, Mitch; Tridandapani, Susheela; Byrd, John C.; Caligiuri, Michael A.; Lee, Robert J.; Carson, William E.

2016-01-01

Optimally effective antitumor therapies would not only activate immune effector cells, but engage them at the tumor. Folate-conjugated to immunoglobulin (F-IgG) could direct innate immune cells with Fc receptors to folate receptor–expressing cancer cells. F-IgG bound to human KB and HeLa cells, as well as murine L1210JF, a folate receptor (FR) overexpressing cancer cell line, as determined by flow cytometry. Recognition of F-IgG by NK cell Fc receptors led to phosphorylation of the ERK transcription factor and increased NK cell expression of CD69. Lysis of KB tumor cells by NK cells increased about 5-fold after treatment with F-IgG, an effect synergistically enhanced by treatment with IL2, IL12, IL15, or IL21 (P < 0.001). F-IgG also enhanced the lysis of chronic lymphocytic leukemia cells by autologous NK cells. NK cells significantly increased production of IFNγ, MIP-1α, and RANTES in response to F-IgG–coated KB target cells in the presence of the NK cell–activating cytokine IL12, and these coculture supernatants induced significant T cell chemotaxis P < 0.001). F-IgG–coated targets also stimulated FcR-mediated monocyte effector functions. Studies in a murine leukemia model confirmed the intratumoral localization and antitumor activity of F-IgG, as well as enhancement of its effects by IL12 (P = 0.05). The antitumor effect of this combination was dependent on NK cells and led to decreased tumor cell proliferation in vivo. Thus, F-IgG can induce an immune response against FR-positive tumor cells that is mediated by NK cells and can be augmented by cytokine therapy. PMID:26865456

Cooperative integrin/ITAM signaling in platelets enhances thrombus formation in vitro and in vivo

PubMed Central

Zhi, Huiying; Rauova, Lubica; Hayes, Vincent; Gao, Cunji; Boylan, Brian; Newman, Debra K.; McKenzie, Steven E.; Cooley, Brian C.; Poncz, Mortimer; Newman, Peter J.

2013-01-01

The integrin family is composed of a series of 24 αβ heterodimer transmembrane adhesion receptors that mediate cell-cell and cell-extracellular matrix interactions. Adaptor molecules bearing immunoreceptor tyrosine-based activation motifs (ITAMs) have recently been shown to cooperate with specific integrins to increase the efficiency of transmitting ligand-binding–induced signals into cells. In human platelets, Fc receptor γ-chain IIa (FcγRIIa) has been identified as an ITAM-bearing transmembrane receptor responsible for mediating “outside-in” signaling through αIIbβ3, the major adhesion receptor on the platelet surface. To explore the importance of FcγRIIa in thrombosis and hemostasis, we subjected FcγRIIa-negative and FcγRIIa-positive murine platelets to a number of well-accepted models of platelet function. Compared with their FcγRIIa-negative counterparts, FcγRIIa-positive platelets exhibited increased tyrosine phosphorylation of Syk and phospholipase Cγ2 and increased spreading upon interaction with immobilized fibrinogen, retracted a fibrin clot faster, and showed markedly enhanced thrombus formation when perfused over a collagen-coated flow chamber under conditions of arterial and venous shear. They also displayed increased thrombus formation and fibrin deposition in in vivo models of vascular injury. Taken together, these data establish FcγRIIa as a physiologically important functional conduit for αIIbβ3-mediated outside-in signaling, and suggest that modulating the activity of this novel integrin/ITAM pair might be effective in controlling thrombosis. PMID:23264598

The binding of an anti-PD-1 antibody to FcγRΙ has a profound impact on its biological functions.

PubMed

Zhang, Tong; Song, Xiaomin; Xu, Lanlan; Ma, Jie; Zhang, Yanjuan; Gong, Wenfeng; Zhang, Yilu; Zhou, Xiaosui; Wang, Zuobai; Wang, Yali; Shi, Yingdi; Bai, Huichen; Liu, Ning; Yang, Xiaolong; Cui, Xinxin; Cao, Yanping; Liu, Qi; Song, Jing; Li, Yucheng; Tang, Zhiyu; Guo, Mingming; Wang, Lai; Li, Kang

2018-04-23

Antibodies targeting PD-1 have been demonstrated durable anti-cancer activity in certain cancer types. However, the anti-PD-1 antibodies are less or not efficacious in many situations, which might be attributed to co-expression of multiple inhibitory receptors or presence of immunosuppressive cells in the tumor microenvironment. Most of the anti-PD-1 antibodies used in clinical studies are of IgG4 isotype with the S228P mutation (IgG4 S228P ). The functional impact by the interaction of anti-PD-1 IgG4 S228P antibody with Fc gamma receptors (FcγRs) is poorly understood. To assess the effects, we generated a pair of anti-PD-1 antibodies: BGB-A317/IgG4 S228P and BGB-A317/IgG4-variant (abbreviated as BGB-A317), with the same variable regions but two different IgG4 Fc-hinge sequences. There was no significant difference between these two antibodies in binding to PD-1. However, BGB-A317/IgG4 S228P binds to human FcγRI with high affinity and mediates crosslinking between PD-1 and FcγRI. In contrast, BGB-A317 does neither. Further cell-based assays showed that such crosslinking could reverse the function of an anti-PD-1 antibody from blocking to activating. More importantly, the crosslinking induces FcγRI + macrophages to phagocytose PD-1 + T cells. In a mouse model transplanted with allogeneic human cancer cells and PBMCs, BGB-A317 showed significant tumor growth inhibition, whereas BGB-A317/IgG4 S228P had no such inhibition. Immunohistochemistry study revealed an inverse correlation between FcγRI + murine macrophage infiltration and the density of CD8 + PD-1 + human T cells within tumors in the BGB-A317/IgG4 S228P -treated group. These evidences suggested that FcγRI + binding and crosslinking had negative impact on the anti-PD-1 antibody-mediated anti-cancer activity.

Dynamics of mononuclear phagocyte system Fc receptor function in systemic lupus erythematosus. Relation to disease activity and circulating immune complexes.

PubMed Central

Kimberly, R P; Parris, T M; Inman, R D; McDougal, J S

1983-01-01

Seventeen pairs of longitudinal studies of mononuclear phagocyte system (MPS) Fc receptor function in 15 patients with systemic lupus were performed to explore the dynamic range of Fc receptor dysfunction in lupus and to establish the relationships between MPS function, clinical disease activity and circulating immune complexes (CIC). Fc receptor function was measured by the clearance of IgG sensitized autologous erythrocytes. At the time of first study the degree of MPS dysfunction was correlated with both clinical activity (P less than 0.05) and CIC (P less than 0.05). At follow-up patients with a change in clinical status show significantly larger changes in clearance function compared to clinically stable patients (206 min vs 7 min; P less than 0.001). MPS function changed concordantly with a change in clinical status in all cases (P = 0.002). Longitudinal assessments did not demonstrate concordance of changes in MPS function and CIC, measured by three different assays. The MPS Fc receptor defect in systemic lupus is dynamic and closely associated with disease activity. The lack of concordance of the defect with changes in CIC suggests that either CIC does not adequately reflect receptor site saturation or that other factors may also contribute to the magnitude of MPS dysfunction. PMID:6839542

Immunomodulation by blockade of the TRANCE co-stimulatory pathway in murine allogeneic islet transplantation

PubMed Central

Wojtusciszyn, Anne; Andres, Axel; Morel, Philippe; Charvier, Solange; Armanet, Mathieu; Toso, Christian; Choi, Yongwon; Bosco, Domenico; Berney, Thierry

2010-01-01

We explore herein the effect of TRANCE costimulatory pathway blockade on islet survival after allograft transplantation. Expression of TRANCE on murine C57BL/6 (B6) CD4+ T-cells after allogeneic activation was analysed by FACS. The effect of a TRANCE receptor fusion protein (TR-Fc) and anti-CD154 antibody (MR1) on B6 spleen cell proliferation after allogeneic activation was assessed by MLR. Three groups of B6 mice were transplanted with allogeneic islets (DBA2): Control; short-term TR-Fc-treatment (days 0–4); and prolonged TR-Fc-treatment (days -1–13). Donor-specific transfusion (DST) was performed at the time of islet transplantation in one independent experiment. Transplantectomy samples were analyzed by immunohistochemistry. TRANCE expression was upregulated in stimulated CD4+ T-cells in vitro. In MLR experiments, TR-Fc and MR1 both reduced spleen cell proliferation, but less than the combination of both molecules. Short course TR-Fc treatment did not prolong islet graft survival as compared to controls (10.6±1.9 vs 10.7±1.5 days) in contrast to prolonged treatment (20.7±3.2 days; p<0.05). After DST, primary non-function (PNF) was observed in half of control mice, but never in TR-Fc-treated mice. Immunofluorescence staining for Mac-1 showed a clear decrease in macrophage recruitment in the treated groups. TRANCE targeting may be an effective strategy for the prolongation of allogeneic islet graft survival, thanks to its inhibitory effects on costimulatory signals and macrophage recruitment. PMID:19453995

Anthrax toxin receptor 1 is the cellular receptor for Seneca Valley virus

PubMed Central

Miles, Linde A.; Burga, Laura N.; Gardner, Eric E.; Bostina, Mihnea; Poirier, John T.; Rudin, Charles M.

2017-01-01

Seneca Valley virus (SVV) is an oncolytic picornavirus with selective tropism for neuroendocrine cancers. It has shown promise as a cancer therapeutic in preclinical studies and early-phase clinical trials. Here, we have identified anthrax toxin receptor 1 (ANTXR1) as the receptor for SVV using genome-wide loss-of-function screens. ANTXR1 is necessary for permissivity in vitro and in vivo. However, robust SVV replication requires an additional innate immune defect. We found that SVV interacts directly and specifically with ANTXR1, that this interaction is required for SVV binding to permissive cells, and that ANTXR1 expression is necessary and sufficient for infection in cell lines with decreased expression of antiviral IFN genes at baseline. Finally, we identified the region of the SVV capsid that is responsible for receptor recognition using cryoelectron microscopy of the SVV-ANTXR1-Fc complex. These studies identify ANTXR1, a class of receptor that is shared by a mammalian virus and a bacterial toxin, as the cellular receptor for SVV. PMID:28650343

A direct GABAergic output from the basal ganglia to frontal cortex

PubMed Central

Saunders, Arpiar; Oldenburg, Ian A.; Berezovskii, Vladimir K.; Johnson, Caroline A.; Kingery, Nathan D.; Elliott, Hunter L.; Xie, Tiao; Gerfen, Charles R.; Sabatini, Bernardo L.

2014-01-01

The basal ganglia (BG) are phylogenetically conserved subcortical nuclei necessary for coordinated motor action and reward learning1. Current models postulate that the BG modulate cerebral cortex indirectly via an inhibitory output to thalamus, bidirectionally controlled by the BG via direct (dSPNs) and indirect (iSPNs) pathway striatal projection neurons2–4. The BG thalamic output sculpts cortical activity by interacting with signals from sensory and motor systems5. Here we describe a direct projection from the globus pallidus externus (GP), a central nucleus of the BG, to frontal regions of the cerebral cortex (FC). Two cell types make up the GP-FC projection, distinguished by their electrophysiological properties, cortical projections and expression of choline acetyltransferase (ChAT), a synthetic enzyme for the neurotransmitter acetylcholine (ACh). Despite these differences, ChAT+ cells, which have been historically identified as an extension of the nucleus basalis (NB), as well as ChAT− cells, release the inhibitory neurotransmitter GABA (γ-aminobutyric acid) and are inhibited by iSPNs and dSPNs of dorsal striatum. Thus GP-FC cells comprise a direct GABAergic/cholinergic projection under the control of striatum that activates frontal cortex in vivo. Furthermore, iSPN inhibition of GP-FC cells is sensitive to dopamine 2 receptor signaling, revealing a pathway by which drugs that target dopamine receptors for the treatment of neuropsychiatric disorders can act in the BG to modulate frontal cortices. PMID:25739505

Immune complexes stimulate CCR7-dependent dendritic cell migration to lymph nodes

PubMed Central

Clatworthy, Menna R.; Aronin, Caren E. Petrie; Mathews, Rebeccah J.; Morgan, Nicole; Smith, Kenneth G.C.; Germain, Ronald N.

2014-01-01

Antibodies are critical for defence against a variety of microbes but may also be pathogenic in some autoimmune diseases. Many effector functions of antibody are mediated by Fcγ receptors (FcγRs), which are found on most immune cells, including dendritic cells (DCs). DCs are important antigen presenting cells and play a central role in inducing antigen-specific tolerance or immunity1,2. Following antigen acquisition in peripheral tissues, DCs migrate to draining lymph nodes via lymphatics to present antigen to T cells. In this study we demonstrate that FcγR engagement by IgG immune complexes (IC) stimulates DC migration from peripheral tissues to the paracortex of draining lymph nodes. In vitro, IC-stimulated murine and human DCs showed enhanced directional migration in a CCL19 gradient and increased CCR7 expression. Using intravital two-photon microscopy, we observed that local administration of IC resulted in dermal DC mobilisation. We confirmed that dermal DC migration to lymph nodes was CCR7-dependent and increased in the absence of the inhibitory receptor, FcγRIIb. These observations have relevance to autoimmunity, because autoantibody-containing serum from mice and humans with SLE also increased dermal DC migration to lymph nodes in vivo, suggesting that this process may occur in lupus, potentially driving the inappropriate localisation of autoantigen-bearing DCs. PMID:25384086

Plasmacytoid Dendritic Cells: Neglected Regulators of the Immune Response to Staphylococcus aureus

PubMed Central

Bekeredjian-Ding, Isabelle; Greil, Johann; Ammann, Sandra; Parcina, Marijo

2014-01-01

Plasmacytoid dendritic cells (pDC) are a rare subset of leukocytes equipped with Fcγ and Fcε receptors, which exert contrary effects on sensing of microbial nucleic acids by endosomal Toll-like receptors. In this article, we explain how pDC contribute to the immune response to Staphylococcus aureus. Under normal circumstances the pDC participates in the memory response to the pathogen: pDC activation is initiated by uptake of staphylococcal immune complexes with IgG or IgE. However, protein A-expressing S. aureus strains additionally trigger pDC activation in the absence of immunoglobulin. In this context, staphylococci exploit the pDC to induce antigen-independent differentiation of IL-10 producing plasmablasts, an elegant means to propagate immune evasion. We further discuss the role of type I interferons in infection with S. aureus and the implications of these findings for the development of immune based therapies and vaccination. PMID:24904586

Mac-1 (CD11b/CD18) is essential for Fc receptor-mediated neutrophil cytotoxicity and immunologic synapse formation.

PubMed

van Spriel, A B; Leusen, J H; van Egmond, M; Dijkman, H B; Assmann, K J; Mayadas, T N; van de Winkel, J G

2001-04-15

Receptors for human immunoglobulin (Ig)G and IgA initiate potent cytolysis of antibody (Ab)-coated targets by polymorphonuclear leukocytes (PMNs). Mac-1 (complement receptor type 3, CD11b/CD18) has previously been implicated in receptor cooperation with Fc receptors (FcRs). The role of Mac-1 in FcR-mediated lysis of tumor cells was characterized by studying normal human PMNs, Mac-1-deficient mouse PMNs, and mouse PMNs transgenic for human FcR. All PMNs efficiently phagocytosed Ab-coated particles. However, antibody-dependent cellular cytotoxicity (ADCC) was abrogated in Mac-1(-/-) PMNs and in human PMNs blocked with anti-Mac-1 monoclonal Ab (mAb). Mac-1(-/-) PMNs were unable to spread on Ab-opsonized target cells and other Ab-coated surfaces. Confocal laser scanning and electron microscopy revealed a striking difference in immunologic synapse formation between Mac-1(-/-) and wild-type PMNs. Also, respiratory burst activity could be measured outside membrane-enclosed compartments by using Mac-1(-/-) PMNs bound to Ab-coated tumor cells, in contrast to wild-type PMNs. In summary, these data document an absolute requirement of Mac-1 for FcR-mediated PMN cytotoxicity toward tumor targets. Mac-1(-/-) PMNs exhibit defective spreading on Ab-coated targets, impaired formation of immunologic synapses, and absent tumor cytolysis.

IgG Fc domains that bind C1q but not effector Fcγ receptors delineate the importance of complement-mediated effector functions.

PubMed

Lee, Chang-Han; Romain, Gabrielle; Yan, Wupeng; Watanabe, Makiko; Charab, Wissam; Todorova, Biliana; Lee, Jiwon; Triplett, Kendra; Donkor, Moses; Lungu, Oana I; Lux, Anja; Marshall, Nicholas; Lindorfer, Margaret A; Goff, Odile Richard-Le; Balbino, Bianca; Kang, Tae Hyun; Tanno, Hidetaka; Delidakis, George; Alford, Corrine; Taylor, Ronald P; Nimmerjahn, Falk; Varadarajan, Navin; Bruhns, Pierre; Zhang, Yan Jessie; Georgiou, George

2017-08-01

Engineered crystallizable fragment (Fc) regions of antibody domains, which assume a unique and unprecedented asymmetric structure within the homodimeric Fc polypeptide, enable completely selective binding to the complement component C1q and activation of complement via the classical pathway without any concomitant engagement of the Fcγ receptor (FcγR). We used the engineered Fc domains to demonstrate in vitro and in mouse models that for therapeutic antibodies, complement-dependent cell-mediated cytotoxicity (CDCC) and complement-dependent cell-mediated phagocytosis (CDCP) by immunological effector molecules mediated the clearance of target cells with kinetics and efficacy comparable to those of the FcγR-dependent effector functions that are much better studied, while they circumvented certain adverse reactions associated with FcγR engagement. Collectively, our data highlight the importance of CDCC and CDCP in monoclonal-antibody function and provide an experimental approach for delineating the effect of complement-dependent effector-cell engagement in various therapeutic settings.

Salivary Immunoglobulin Gene Expression in Patients with Caries

PubMed Central

Santín, Gema Regina Guadarrama; Salgado, Angel Visoso; Bastida, Norma Margarita Montiel; Gómez, Isaías de la Rosa; Benítez, Jonnathan Guadalupe Santillán; Zerón, Hugo Mendieta

2017-01-01

BACKGROUND: Immunoglobulins mediate the host’s humoral immune response are expressed in saliva. AIM: To quantify the FcαR, FcγRIIB, and FcαμR gene expression in the saliva of Mexican patients with caries in mixed and permanent dentition. SUBJECTS AND METHODS: This was a comparative cross-sectional study. mRNA was isolated from 200 μL of saliva following the RNA III Tissue Fresh-frozen protocol of the MagNA Pure LC Instrument 2.0 (Roche Diagnostics GmbH, Nederland BV) and the FcαR, FcαμR and FcγRIIB were quantified through TaqMan Assays. RESULTS: One hundred individuals, 50 with mixed dentition and 50 with permanent dentition, were included in the study. Statistically, it was found a significant difference (p = 0.025) in the IgG (FcγRIIB) expression between the studied groups. CONCLUSION: Although we confirmed the existence of FcαR, FcγRIIB and FcαμR gene expression in saliva, only a significant difference in the expression of FcγRIIB between the mixed dentition and permanent dentition was found. PMID:28507635

Immunoglobulin G1 Fc domain motions: implications for Fc engineering

PubMed Central

Frank, Martin; Walker, Ross C.; Lanzilotta, William N.; Prestegard, James H.; Barb, Adam W.

2014-01-01

The fragment crystallizable (Fc) region links the key pathogen identification and destruction properties of immunoglobulin G(IgG). Pathogen opsonization positions Fcs to activate pro-inflammatory Fcγ receptors (FcγRs) on immune cells. The cellular response and committal to a damaging, though protective, immune response is tightly controlled at multiple levels. Control mechanisms are diverse and in many cases unclear, but one frequently suggested contribution originates in Fcγ receptor affinity being modulated through shifts in Fc conformational sampling. Here we report a previously unseen IgG1 Fc conformation. This observation motivated an extensive molecular dynamics (MD) investigation of polypeptide and glycan motions that revealed greater amplitude of motion for the N-terminal Cγ2 domains and N-glycan than previously observed. Residues in the Cγ2/Cγ3 interface and disulphide-bonded hinge were identified as influencing the Cγ2 motion. Our results are consistent with a model of Fc that is structurally dynamic. Conformational states that are competent to bind immune-stimulating FcγRs interconverted with Fc conformations distinct from those observed in FcγR complexes, which may represent a transient, nonbinding population. PMID:24522230

A Two-pronged Binding Mechanism of IgG to the Neonatal Fc Receptor Controls Complex Stability and IgG Serum Half-life*

PubMed Central

Schoch, Angela; Larraillet, Vincent; Hilger, Maximiliane; Schlothauer, Tilman; Emrich, Thomas

2017-01-01

The success of recombinant monoclonal immunoglobulins (IgG) is rooted in their ability to target distinct antigens with high affinity combined with an extraordinarily long serum half-life, typically around 3 weeks. The pharmacokinetics of IgGs is intimately linked to the recycling mechanism of the neonatal Fc receptor (FcRn). For long serum half-life of therapeutic IgGs, the highly pH-dependent interaction with FcRn needs to be balanced to allow efficient FcRn binding and release at slightly acidic pH and physiological pH, respectively. Some IgGs, like the antibody briakinumab has an unusually short half-life of ∼8 days. Here we dissect the molecular origins of excessive FcRn binding in therapeutic IgGs using a combination of hydrogen/deuterium exchange mass spectrometry and FcRn affinity chromatography. We provide experimental evidence for a two-pronged IgG-FcRn binding mechanism involving direct FcRn interactions with both the Fc region and the Fab regions of briakinumab, and correlate the occurrence of excessive FcRn binding to an unusually strong Fab-FcRn interaction. PMID:28062799

The adaptor protein Crk controls activation and inhibition of natural killer cells.

PubMed

Liu, Dongfang; Peterson, Mary E; Long, Eric O

2012-04-20

Natural killer (NK) cell inhibitory receptors recruit tyrosine phosphatases to prevent activation, induce phosphorylation and dissociation of the small adaptor Crk from cytoskeleton scaffold complexes, and maintain NK cells in a state of responsiveness to subsequent activation events. How Crk contributes to inhibition is unknown. We imaged primary NK cells over lipid bilayers carrying IgG1 Fc to stimulate CD16 and human leukocyte antigen (HLA)-E to inhibit through receptor CD94-NKG2A. HLA-E alone induced Crk phosphorylation in NKG2A(+) NK cells. At activating synapses with Fc alone, Crk was required for the movement of Fc microclusters and their ability to trigger activation signals. At inhibitory synapses, HLA-E promoted central accumulation of both Fc and phosphorylated Crk and blocked the Fc-induced buildup of F-actin. We propose a unified model for inhibitory receptor function: Crk phosphorylation prevents essential Crk-dependent activation signals and blocks F-actin network formation, thereby reducing constraints on subsequent engagement of activation receptors. Copyright © 2012 Elsevier Inc. All rights reserved.

Effects of meal composition and meal timing on the expression of genes involved in hepatic drug metabolism in rats

PubMed Central

Oosterman, J. E.; Eggink, H. M.; de Goede, P.; Sen, S.; Foppen, E.; Boudzovitch-Surovtseva, O.; Boelen, A.; Romijn, J. A.

2017-01-01

Introduction With chronotherapy, drug administration is synchronized with daily rhythms in drug clearance and pharmacokinetics. Daily rhythms in gene expression are centrally mastered by the suprachiasmatic nucleus of the hypothalamus as well as by tissue clocks containing similar molecular mechanisms in peripheral organs. The central timing system is sensitive to changes in the external environment such as those of the light-dark cycle, meal timing and meal composition. We investigated how changes in diet composition and meal timing would affect the daily hepatic expression rhythms of the nuclear receptors PXR and CAR and of enzymes involved in P450 mediated drug metabolism, as such changes could have consequences for the practice of chronotherapy. Materials and methods Rats were subjected to either a regular chow or a free choice high-fat-high-sugar (fcHFHS) diet. These diets were provided ad libitum, or restricted to either the light phase or the dark phase. In a second experiment, rats had access to chow either ad libitum or in 6 meals equally distributed over 24 hours. Results Pxr, Alas1 and Por displayed significant day-night rhythms under ad libitum chow fed conditions, which for Pxr was disrupted under fcHFHS diet conditions. Although no daily rhythms were detected in expression of CAR, Cyp2b2 and Cyp3a2, the fcHFHS diet did affect basal expression of these genes. In chow fed rats, dark phase feeding induced a diurnal rhythm in Cyp2b2 expression while light phase feeding induced a diurnal rhythm in Car expression and completely shifted the peak expression of Pxr, Car, Cyp2b2, Alas1 and Por. The 6-meals-a-day feeding only abolished the Pxr rhythm but not the rhythms of the other genes. Conclusion We conclude that although nuclear receptors and enzymes involved in the regulation of hepatic drug metabolism are sensitive to meal composition, changes in meal timing are mainly effectuated via changes in the molecular clock. PMID:28968417

Antibody glycosylation and its impact on the pharmacokinetics and pharmacodynamics of monoclonal antibodies and Fc-fusion proteins.

PubMed

Liu, Liming

2015-06-01

Understanding the impact of glycosylation and keeping a close control on glycosylation of product candidates are required for both novel and biosimilar monoclonal antibodies (mAbs) and Fc-fusion protein development to ensure proper safety and efficacy profiles. Most therapeutic mAbs are of IgG class and contain a glycosylation site in the Fc region at amino acid position 297 and, in some cases, in the Fab region. For Fc-fusion proteins, glycosylation also frequently occurs in the fusion partners. Depending on the expression host, glycosylation patterns in mAb or Fc-fusions can be significantly different, thus significantly impacting the pharmacokinetics (PK) and pharmacodynamics (PD) of mAbs. Glycans that have a major impact on PK and PD of mAb or Fc-fusion proteins include mannose, sialic acids, fucose (Fuc), and galactose (Gal). Mannosylated glycans can impact the PK of the molecule, leading to reduced exposure and potentially lower efficacy. The level of sialic acid, N-acetylneuraminic acid (NANA), can also have a significant impact on the PK of Fc-fusion molecules. Core Fuc in the glycan structure reduces IgG antibody binding to IgG Fc receptor IIIa relative to IgG lacking Fuc, resulting in decreased antibody-dependent cell-mediated cytotoxicity (ADCC) activities. Glycoengineered Chinese hamster ovary (CHO) expression systems can produce afucosylated mAbs that have increased ADCC activities. Terminal Gal in a mAb is important in the complement-dependent cytotoxicity (CDC) in that lower levels of Gal reduce CDC activity. Glycans can also have impacts on the safety of mAb. mAbs produced in murine myeloma cells such as NS0 and SP2/0 contain glycans such as Galα1-3Galβ1-4N-acetylglucosamine-R and N-glycolylneuraminic acid (NGNA) that are not naturally present in humans and can be immunogenic when used as therapeutics. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

FcRn Rescues Recombinant Factor VIII Fc Fusion Protein from a VWF Independent FVIII Clearance Pathway in Mouse Hepatocytes

PubMed Central

van der Flier, Arjan; Liu, Zhan; Tan, Siyuan; Chen, Kai; Drager, Douglas; Liu, Tongyao; Patarroyo-White, Susannah; Jiang, Haiyan; Light, David R.

2015-01-01

We recently developed a longer lasting recombinant factor VIII-Fc fusion protein, rFVIIIFc, to extend the half-life of replacement FVIII for the treatment of people with hemophilia A. In order to elucidate the biological mechanism for the elongated half-life of rFVIIIFc at a cellular level we delineated the roles of VWF and the tissue-specific expression of the neonatal Fc receptor (FcRn) in the biodistribution, clearance and cycling of rFVIIIFc. We find the tissue biodistribution is similar for rFVIIIFc and rFVIII and that liver is the major clearance organ for both molecules. VWF reduces the clearance and the initial liver uptake of rFVIIIFc. Pharmacokinetic studies in FcRn chimeric mice show that FcRn expressed in somatic cells (hepatocytes or liver sinusoidal endothelial cells) mediates the decreased clearance of rFVIIIFc, but FcRn in hematopoietic cells (Kupffer cells) does not affect clearance. Immunohistochemical studies show that when rFVIII or rFVIIIFc is in dynamic equilibrium binding with VWF, they mostly co localize with VWF in Kupffer cells and macrophages, confirming a major role for liver macrophages in the internalization and clearance of the VWF-FVIII complex. In the absence of VWF a clear difference in cellular localization of VWF-free rFVIII and rFVIIIFc is observed and neither molecule is detected in Kupffer cells. Instead, rFVIII is observed in hepatocytes, indicating that free rFVIII is cleared by hepatocytes, while rFVIIIFc is observed as a diffuse liver sinusoidal staining, suggesting recycling of free-rFVIIIFc out of hepatocytes. These studies reveal two parallel linked clearance pathways, with a dominant pathway in which both rFVIIIFc and rFVIII complexed with VWF are cleared mainly by Kupffer cells without FcRn cycling. In contrast, the free fraction of rFVIII or rFVIIIFc unbound by VWF enters hepatocytes, where FcRn reduces the degradation and clearance of rFVIIIFc relative to rFVIII by cycling rFVIIIFc back to the liver sinusoid and into circulation, enabling the elongated half-life of rFVIIIFc. PMID:25905473

A dual positive and negative regulation of monocyte activation by leukocyte Ig-like receptor B4 depends on the position of the tyrosine residues in its ITIMs.

PubMed

Park, Mijeong; Liu, Robert W; An, Hongyan; Geczy, Carolyn L; Thomas, Paul S; Tedla, Nicodemus

2017-05-01

The leukocyte Ig-like receptor B4 (LILRB4) is an inhibitory cell surface receptor, primarily expressed on mono-myeloid cells. It contains 2 C-type Ig-like extracellular domains and a long cytoplasmic domain that contains three intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Data suggest that LILRB4 suppresses Fc receptor-dependent monocyte functions via its ITIMs, but relative contributions of the three ITIMs are not characterised. To address this, tyrosine (Tyr) residues at positions 337, 389 and 419 were single, double or triple mutated to phenylalanine and stably transfected into a human monocytic cell line, THP-1. Intact Tyr 389 was sufficient to maximally inhibit FcγRI-mediated TNF-α production in THP-1 cells, but, paradoxically, Tyr 337 significantly enhanced TNF-α production. In contrast, bactericidal activity was significantly enhanced in mutants containing Tyr 419 , while Tyr 337 markedly inhibited bacteria killing. Taken together, these results indicate that LILRB4 might have dual inhibitory and activating functions, depending on the position of the functional tyrosine residues in its ITIMs and/or the nature of the stimuli.

Fc-Binding Ligands of Immunoglobulin G: An Overview of High Affinity Proteins and Peptides

PubMed Central

Choe, Weonu; Durgannavar, Trishaladevi A.; Chung, Sang J.

2016-01-01

The rapidly increasing application of antibodies has inspired the development of several novel methods to isolate and target antibodies using smart biomaterials that mimic the binding of Fc-receptors to antibodies. The Fc-binding domain of antibodies is the primary binding site for e.g., effector proteins and secondary antibodies, whereas antigens bind to the Fab region. Protein A, G, and L, surface proteins expressed by pathogenic bacteria, are well known to bind immunoglobulin and have been widely exploited in antibody purification strategies. Several difficulties are encountered when bacterial proteins are used in antibody research and application. One of the major obstacles hampering the use of bacterial proteins is sample contamination with trace amounts of these proteins, which can invoke an immune response in the host. Many research groups actively develop synthetic ligands that are able to selectively and strongly bind to antibodies. Among the reported ligands, peptides that bind to the Fc-domain of antibodies are attractive tools in antibody research. Besides their use as high affinity ligands in antibody purification chromatography, Fc-binding peptides are applied e.g., to localize antibodies on nanomaterials and to increase the half-life of proteins in serum. In this review, recent developments of Fc-binding peptides are presented and their binding characteristics and diverse applications are discussed. PMID:28774114

Characterization and screening of IgG binding to the neonatal Fc receptor

PubMed Central

Neuber, Tobias; Frese, Katrin; Jaehrling, Jan; Jäger, Sebastian; Daubert, Daniela; Felderer, Karin; Linnemann, Mechthild; Höhne, Anne; Kaden, Stefan; Kölln, Johanna; Tiller, Thomas; Brocks, Bodo; Ostendorp, Ralf; Pabst, Stefan

2014-01-01

The neonatal Fc receptor (FcRn) protects immunoglobulin G (IgG) from degradation and increases the serum half-life of IgG, thereby contributing to a higher concentration of IgG in the serum. Because altered FcRn binding may result in a reduced or prolonged half-life of IgG molecules, it is advisable to characterize Fc receptor binding of therapeutic antibody lead candidates prior to the start of pre-clinical and clinical studies. In this study, we characterized the interactions between FcRn of different species (human, cynomolgus monkey, mouse and rat) and nine IgG molecules from different species and isotypes with common variable heavy (VH) and variable light chain (VL) domains. Binding was analyzed at acidic and neutral pH using surface plasmon resonance (SPR) and biolayer interferometry (BLI). Furthermore, we transferred the well-accepted, but low throughput SPR-based method for FcRn binding characterization to the BLI-based Octet platform to enable a higher sample throughput allowing the characterization of FcRn binding already during early drug discovery phase. We showed that the BLI-based approach is fit-for-purpose and capable of discriminating between IgG molecules with significant differences in FcRn binding affinities. Using this high-throughput approach we investigated FcRn binding of 36 IgG molecules that represented all VH/VL region combinations available in the fully human, recombinant antibody library Ylanthia®. Our results clearly showed normal FcRn binding profiles for all samples. Hence, the variations among the framework parts, complementarity-determining region (CDR) 1 and CDR2 of the fragment antigen binding (Fab) domain did not significantly change FcRn binding. PMID:24802048

The Impact of HLA Class I-Specific Killer Cell Immunoglobulin-Like Receptors on Antibody-Dependent Natural Killer Cell-Mediated Cytotoxicity and Organ Allograft Rejection

PubMed Central

Rajalingam, Raja

2016-01-01

Natural killer (NK) cells of the innate immune system are cytotoxic lymphocytes that play an important roles following transplantation of solid organs and hematopoietic stem cells. Recognition of self-human leukocyte antigen (HLA) class I molecules by inhibitory killer cell immunoglobulin-like receptors (KIRs) is involved in the calibration of NK cell effector capacities during the developmental stage, allowing the subsequent recognition and elimination of target cells with decreased expression of self-HLA class I (due to virus infection or tumor transformation) or HLA class I disparities (in the setting of allogeneic transplantation). NK cells expressing an inhibitory KIR-binding self-HLA can be activated when confronted with allografts lacking a ligand for the inhibitory receptor. Following the response of the adaptive immune system, NK cells can further destroy allograft endothelium by antibody-dependent cell-mediated cytotoxicity (ADCC), triggered through cross-linking of the CD16 Fc receptor by donor-specific antibodies bound to allograft. Upon recognizing allogeneic target cells, NK cells also secrete cytokines and chemokines that drive maturation of dendritic cells to promote cellular and humoral adaptive immune responses against the allograft. The cumulative activating and inhibitory signals generated by ligation of the receptors regulates mature NK cell killing of target cells and their production of cytokines and chemokines. This review summarizes the role of NK cells in allograft rejection and proposes mechanistic concepts that indicate a prominent role for KIR–HLA interactions in facilitating NK cells for Fc receptor-mediated ADCC effector function involved in antibody-mediated rejection of solid organ transplants. PMID:28066408

Determination of the binding mode for the cyclopentapeptide CXCR4 antagonist FC131 using a dual approach of ligand modifications and receptor mutagenesis

PubMed Central

Thiele, S; Mungalpara, J; Steen, A; Rosenkilde, M M; Våbenø, J

2014-01-01

Background and Purpose The cyclopentapeptide FC131 (cyclo(-L-Arg1-L-Arg2-L-2-Nal3-Gly4-D-Tyr5-)) is an antagonist at the CXC chemokine receptor CXCR4, which plays a role in human immunodeficiency virus infection, cancer and stem cell recruitment. Binding modes for FC131 in CXCR4 have previously been suggested based on molecular docking guided by structure–activity relationship (SAR) data; however, none of these have been verified by in vitro experiments. Experimental Approach Heterologous 125I-12G5-competition binding and functional assays (inhibition of CXCL12-mediated activation) of FC131 and three analogues were performed on wild-type CXCR4 and 25 receptor mutants. Computational modelling was used to rationalize the experimental data. Key Results The Arg2 and 2-Nal3 side chains of FC131 interact with residues in TM-3 (His113, Asp171) and TM-5 (hydrophobic pocket) respectively. Arg1 forms charge-charge interactions with Asp187 in ECL-2, while D-Tyr5 points to the extracellular side of CXCR4. Furthermore, the backbone of FC131 interacts with the chemokine receptor-conserved Glu288 via two water molecules. Intriguingly, Tyr116 and Glu288 form a H-bond in CXCR4 crystal structures and mutation of either residue to Ala abolishes CXCR4 activity. Conclusions and Implications Ligand modification, receptor mutagenesis and computational modelling approaches were used to identify the binding mode of FC131 in CXCR4, which was in agreement with binding modes suggested from previous SAR studies. Furthermore, insights into the mechanism for CXCR4 activation by CXCL12 were gained. The combined findings will facilitate future design of novel CXCR4 antagonists. PMID:25039237

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

PubMed Central

DuSablon, Augustin; Parks, Justin; Whitehurst, K’Shylah; Estes, Heather; Chase, Robert; Vlahos, Eleftherios; Sharma, Uma; Wert, David

2017-01-01

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult. PMID:29236774

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice.

PubMed

DuSablon, Augustin; Parks, Justin; Whitehurst, K'Shylah; Estes, Heather; Chase, Robert; Vlahos, Eleftherios; Sharma, Uma; Wert, David; Virag, Jitka

2017-01-01

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

Opposing Effects of Acute versus Chronic Blockade of Frontal Cortex Somatostatin-Positive Inhibitory Neurons on Behavioral Emotionality in Mice

PubMed Central

Soumier, Amelie; Sibille, Etienne

2014-01-01

Reduced expression of somatostatin (SST) is reported across chronic brain conditions including major depression and normal aging. SST is a signaling neuropeptide and marker of gamma-amino butyric acid (GABA) neurons, which specifically inhibit pyramidal neuron dendrites. Studies in auditory cortex suggest that chronic reduction in dendritic inhibition induces compensatory homeostatic adaptations that oppose the effects of acute inhibition. Whether such mechanisms occur in frontal cortex (FC) and affect behavioral outcome is not known. Here, we used two complementary viral vector strategies to examine the effects of acute vs chronic inhibition of SST-positive neurons on behavioral emotionality in adult mice. SST-IRES-Cre mice were injected in FC (prelimbic/precingulate) with CRE-dependent adeno-associated viral (AAV) vector encoding the engineered Gi/o-coupled human muscarinic M4 designer receptor exclusively activated by a designer drug (DREADD-hM4Di) or a control reporter (AAV-DIO-mCherry) for acute or chronic cellular inhibition. A separate cohort was injected with CRE-dependent AAV vectors expressing diphtheria toxin (DTA) to selectively ablate FC SST neurons. Mice were assessed for anxiety- and depressive-like behaviors (defined as emotionality). Results indicate that acute inhibition of FC SST neurons increased behavioral emotionality, whereas chronic inhibition decreased behavioral emotionality. Furthermore, ablation of FC SST neurons also decreased behavioral emotionality under baseline condition and after chronic stress. Together, our results reveal opposite effects of acute and chronic inhibition of FC SST neurons on behavioral emotionality and suggest the recruitment of homeostatic plasticity mechanisms that have implications for understanding the neurobiology of chronic brain conditions affecting dendritic-targeting inhibitory neurons. PMID:24690741

Opposing effects of acute versus chronic blockade of frontal cortex somatostatin-positive inhibitory neurons on behavioral emotionality in mice.

PubMed

Soumier, Amelie; Sibille, Etienne

2014-08-01

Reduced expression of somatostatin (SST) is reported across chronic brain conditions including major depression and normal aging. SST is a signaling neuropeptide and marker of gamma-amino butyric acid (GABA) neurons, which specifically inhibit pyramidal neuron dendrites. Studies in auditory cortex suggest that chronic reduction in dendritic inhibition induces compensatory homeostatic adaptations that oppose the effects of acute inhibition. Whether such mechanisms occur in frontal cortex (FC) and affect behavioral outcome is not known. Here, we used two complementary viral vector strategies to examine the effects of acute vs chronic inhibition of SST-positive neurons on behavioral emotionality in adult mice. SST-IRES-Cre mice were injected in FC (prelimbic/precingulate) with CRE-dependent adeno-associated viral (AAV) vector encoding the engineered Gi/o-coupled human muscarinic M4 designer receptor exclusively activated by a designer drug (DREADD-hM4Di) or a control reporter (AAV-DIO-mCherry) for acute or chronic cellular inhibition. A separate cohort was injected with CRE-dependent AAV vectors expressing diphtheria toxin (DTA) to selectively ablate FC SST neurons. Mice were assessed for anxiety- and depressive-like behaviors (defined as emotionality). Results indicate that acute inhibition of FC SST neurons increased behavioral emotionality, whereas chronic inhibition decreased behavioral emotionality. Furthermore, ablation of FC SST neurons also decreased behavioral emotionality under baseline condition and after chronic stress. Together, our results reveal opposite effects of acute and chronic inhibition of FC SST neurons on behavioral emotionality and suggest the recruitment of homeostatic plasticity mechanisms that have implications for understanding the neurobiology of chronic brain conditions affecting dendritic-targeting inhibitory neurons.

Ephrin-B2 is differentially expressed in the intestinal epithelium in Crohn’s disease and contributes to accelerated epithelial wound healing in vitro

PubMed Central

Hafner, Christian; Meyer, Stefanie; Langmann, Thomas; Schmitz, Gerd; Bataille, Frauke; Hagen, Ilja; Becker, Bernd; Roesch, Alexander; Rogler, Gerhard; Landthaler, Michael; Vogt, Thomas

2005-01-01

AIM: Eph receptor tyrosine kinases and their membrane bound receptor-like ligands, the ephrins, represent a bi-directional cell-cell contact signaling system that directs epithelial movements in development. The meaning of this system in the adult human gut is unknown. We investigated the Eph/ephrin mRNA expression in the intestinal epithelium of healthy controls and patients with inflammatory bowel disease (IBD). METHODS: mRNA expression profiles of all Eph/ephrin family members in normal small intestine and colon were established by real-time RT-PCR. In addition, differential expression in IBD was investigated by cDNA array technology, and validated by both real-time RT-PCR and immunohistochemistry. Potential effects of enhanced EphB/ephrin-B signaling were analyzed in an in vitro IEC-6 cell scratch wound model. RESULTS: Human adult intestinal mucosa exhibits a complex pattern of Eph receptors and ephrins. Beside the known prominent co-expression of EphA2 and ephrinA1, we found abundantly co-expressed EphB2 and ephrin-B1/2. Interestingly, cDNA array data, validated by real-time PCR and immunohistochemistry, showed upregulation of ephrin-B2 in both perilesional and lesional intestinal epithelial cells of IBD patients, suggesting a role in epithelial homeostasis. Stimulation of ephrin-B signaling in ephrin-B1/2 expressing rat IEC-6-cells with recombinant EphB1-Fc resulted in a significant dose-dependent acceleration of wound closure. Furthermore, fluorescence microscopy showed that EphB1-Fc induced coordinated migration of wound edge cells is associated with enhanced formation of lamellipodial protrusions into the wound, increased actin stress fiber assembly and production of laminin at the wound edge. CONCLUSION: EphB/ephrin-B signaling might represent a novel protective mechanism that promotes intestinal epithelial wound healing, with potential impact on epithelial restitution in IBD. PMID:15996027

Quantitative cumulative biodistribution of antibodies in mice

PubMed Central

Yip, Victor; Palma, Enzo; Tesar, Devin B; Mundo, Eduardo E; Bumbaca, Daniela; Torres, Elizabeth K; Reyes, Noe A; Shen, Ben Q; Fielder, Paul J; Prabhu, Saileta; Khawli, Leslie A; Boswell, C Andrew

2014-01-01

The neonatal Fc receptor (FcRn) plays an important and well-known role in antibody recycling in endothelial and hematopoietic cells and thus it influences the systemic pharmacokinetics (PK) of immunoglobulin G (IgG). However, considerably less is known about FcRn’s role in the metabolism of IgG within individual tissues after intravenous administration. To elucidate the organ distribution and gain insight into the metabolism of humanized IgG1 antibodies with different binding affinities FcRn, comparative biodistribution studies in normal CD-1 mice were conducted. Here, we generated variants of herpes simplex virus glycoprotein D-specific antibody (humanized anti-gD) with increased and decreased FcRn binding affinity by genetic engineering without affecting antigen specificity. These antibodies were expressed in Chinese hamster ovary cell lines, purified and paired radiolabeled with iodine-125 and indium-111. Equal amounts of I-125-labeled and In-111-labeled antibodies were mixed and intravenously administered into mice at 5 mg/kg. This approach allowed us to measure both the real-time IgG uptake (I-125) and cumulative uptake of IgG and catabolites (In-111) in individual tissues up to 1 week post-injection. The PK and distribution of the wild-type IgG and the variant with enhanced binding for FcRn were largely similar to each other, but vastly different for the rapidly cleared low-FcRn-binding variant. Uptake in individual tissues varied across time, FcRn binding affinity, and radiolabeling method. The liver and spleen emerged as the most concentrated sites of IgG catabolism in the absence of FcRn protection. These data provide an increased understanding of FcRn’s role in antibody PK and catabolism at the tissue level. PMID:24572100

FcγRIIIa SNPs and haplotypes affect human IgG binding and association with lupus nephritis in African Americans

PubMed Central

Dong, Chaoling; Ptacek, Travis S; Redden, David T; Zhang, Kui; Brown, Elizabeth E.; Edberg, Jeffrey C.; McGwin, Gerald; Alarcón, Graciela S.; Ramsey-Goldman, Rosalind; Reveille, John D.; Vilá, Luis M.; Petri, Michelle; Qin, Aijian; Wu, Jianming; Kimberly, Robert P.

2014-01-01

Objective To investigate whether the FcγRIIIa-66R/H/L polymorphism influences net effective receptor function and to assess if the FCGR3A combined genotypes formed by FcγRIIIa-66R/H/L and FcγRIIIa-176F/V as well as copy number variation (CNV) confer risk for development of SLE and lupus nephritis. Methods FcγRIIIa variants, expressed on A20 IIA1.6 cells, were used in flow cytometry-based human IgG binding assays. FCGR3A SNP and CNV genotypes were determined by Pyrosequencing methodology in a cohort of 1728 SLE patients and 2404 healthy controls. Results The FcγRIIIa-66L/H/R (rs10127939) polymorphism influences ligand binding capacity in the context of the FcγRIIIa-176V (rs396991) allele. The low binding FcγRIIIa-176F allele was associated with SLE nephritis (p = 0.0609) in African Americans but not in European Americans (p > 0.10). Nephritis among African American SLE subjects was associated with FcγRIIIa low binding haplotypes containing the 66R/H/L and 176F variants (p = 0.03) and with low binding genotype combinations (p = 0.002). No association was observed in European American SLE patients. The distribution of FCGR3A CNV was not significantly different between controls and SLE patients with or without nephritis. Conclusion FcγRIIIa-66R/H/L influences ligand binding. The low binding haplotypes formed by 66R/H/L and 176F confer enhanced risk for lupus nephritis in African Americans. FCGR3A CNVs are not associated with SLE or SLE nephritis in either African Americans or European Americans. PMID:24782186

Microglial Fc Receptors Mediate Physiological Changes Resulting From Antibody Cross-Linking of Myelin Oligodendrocyte Glycoprotein

PubMed Central

Marta, Cecilia B.; Bansal, Rashmi; Pfeiffer, Steven E.

2009-01-01

Antibodies to myelin oligodendrocyte glycoprotein (MOG) have been implicated in Multiple Sclerosis demyelination through activation of complement and/or macrophage-effector processes. We presented a novel mechanism, whereby MOG on oligodendrocytes, when cross-linked with anti-MOG and secondary antibody resulted in its repartitioning into lipid rafts, and changes in protein phosphorylation and morphology. Here, we show that similar events occur when anti-MOG is cross-linked with Fc receptors (FcRs) present on microglia but not with complement. These results indicate that FcRs are endogenous antigen/antibody cross-linkers in vitro, suggesting that FcRs could be physiologically relevant in vivo and possible targets for therapy in Multiple Sclerosis. PMID:18406472

Effect of TLR ligands co-encapsulated with multiepitopic antigen in nanoliposomes targeted to human DCs via Fc receptor for cancer vaccines.

PubMed

Rueda, Felix; Eich, Christina; Cordobilla, Begoña; Domingo, Pere; Acosta, Gerardo; Albericio, Fernando; Cruz, Luis J; Domingo, Joan C

2017-11-01

Nanoliposomes (NLs) hold promise as new highly specific nanomedicine for anti-tumor vaccines, since they could be targeted to specific receptors on dendritic cell (DC) to induce maturation and activation and increase the anti-tumor immune response. Here we studied a NLs formulation targeted or not to FcR (the receptor for the IgG Fc fragment) for the treatment of androgen-responsive prostate cancer. Luteinizing-hormone-releasing hormone (LHRH) peptide (B- and T-cell epitopes), in tandem with a tetanus toxoid T-helper epitope (830-844 region) and several TLR (Toll-Like Receptor) ligands as adjuvants were co-encapsulated. Specific uptake in vitro of LHRH-TT liposomes targeted to the FcRs of human DCs was enhanced. DC maturation/activation, cytokine production and lymphocyte activation were consistently higher in targeted than non-targeted liposomes. Similar increase was observed as more adjuvants were administrated. Targeting to specific receptor and co-encapsulation of several TLR adjuvants are essential factors for the immune response in peptide based liposome vaccine. Copyright © 2017 Elsevier GmbH. All rights reserved.

Ecto-Fc MS identifies ligand-receptor interactions through extracellular domain Fc fusion protein baits and shotgun proteomic analysis

PubMed Central

Savas, Jeffrey N.; De Wit, Joris; Comoletti, Davide; Zemla, Roland; Ghosh, Anirvan

2015-01-01

Ligand-receptor interactions represent essential biological triggers which regulate many diverse and important cellular processes. We have developed a discovery-based proteomic biochemical protocol which couples affinity purification with multidimensional liquid chromatographic tandem mass spectrometry (LCLC-MS/MS) and bioinformatic analysis. Compared to previous approaches, our analysis increases sensitivity, shortens analysis duration, and boosts comprehensiveness. In this protocol, receptor extracellular domains are fused with the Fc region of IgG to generate fusion proteins that are purified from transfected HEK293T cells. These “ecto-Fcs” are coupled to protein A beads and serve as baits for binding assays with prey proteins extracted from rodent brain. After capture, the affinity purified proteins are digested into peptides and comprehensively analyzed by LCLC-MS/MS with ion trap mass spectrometers. In four working days, this protocol can generate shortlists of candidate ligand-receptor protein-protein interactions. Our “Ecto-Fc MS” approach outperforms antibody-based approaches and provides a reproducible and robust framework to identify extracellular ligand – receptor interactions. PMID:25101821

Phosphorylation of SNAP-23 at Ser95 causes a structural alteration and negatively regulates Fc receptor-mediated phagosome formation and maturation in macrophages.

PubMed

Sakurai, Chiye; Itakura, Makoto; Kinoshita, Daiki; Arai, Seisuke; Hashimoto, Hitoshi; Wada, Ikuo; Hatsuzawa, Kiyotaka

2018-05-17

SNAP-23 is a plasma membrane-localized SNARE protein involved in Fc receptor (FcR)-mediated phagocytosis. However, the regulatory mechanism underlying its function remains elusive. Using phosphorylation specific-antibodies, SNAP-23 was found to be phosphorylated at Ser95 in macrophages. To understand the role of this phosphorylation, we established macrophage lines overexpressing the non-phosphorylatable S95A or the phospho-mimicking S95D mutation. The efficiency of phagosome formation and maturation was severely reduced in SNAP-23-S95D-overexpressing cells. To examine whether phosphorylation at Ser95 affected SNAP-23 structure, we constructed intramolecular Förster resonance energy transfer (FRET) probes of SNAP-23 designed to evaluate the approximation of the N-termini of the two SNARE motifs. Interestingly, a high FRET efficiency was detected on the membrane when the S95D probe was used, indicating that phosphorylation at Ser95 caused a dynamic structural shift to the closed form. Co-expression of IκB kinase (IKK) 2 enhanced the FRET efficiency of the wild-type probe on the phagosome membrane. Furthermore, the enhanced phagosomal FRET signal in interferon-γ-activated macrophages was largely dependent on IKK2, and this kinase mediated a delay in phagosome-lysosome fusion. These results suggested that SNAP-23 phosphorylation at Ser95 played an important role in the regulation of SNARE-dependent membrane fusion during FcR-mediated phagocytosis.

The Interaction of Pneumocystis with the C-Type Lectin Receptor Mincle Exerts a Significant Role in Host Defense Against Infection

PubMed Central

Kottom, Theodore J.; Hebrink, Deanne M.; Jenson, Paige E.; Nandakumar, Vijayalakshmi; Wüthrich, Marcel; Wang, Huafeng; Klein, Bruce; Yamasaki, Sho; Lepenies, Bernd; Limper, Andrew H.

2017-01-01

Pneumocystis pneumonia (PCP) remains a major cause of morbidity and mortality within immunocompromised patients. In this study, we examined the potential role of Mincle (Macrophage inducible C-type lectin) for host defense against Pneumocystis. Binding assays implementing soluble Mincle Carbohydrate Recognition Domain (CRD) fusion proteins demonstrated binding to intact Pneumocystis carinii (Pc) as well as to organism homogenates, and purified major surface glycoprotein/glycoprotein A derived from the organism. Additional experiments showed that rats with Pneumocystis pneumonia (PCP) expressed increased Mincle mRNA levels. Mouse macrophages over-expressing Mincle displayed increased binding to Pc life forms and enhanced protein tyrosine phosphorylation. The binding of Pc to Mincle resulted in activation of Fc receptor γ (FcRγ) mediated cell signaling. RNA silencing of Mincle in mouse macrophages resulted in decreased activation of Syk kinase after Pc challenge, critical in downstream inflammatory signaling. Mincle deficient CD-4 depleted (Mincle−/−) mice showing a significant defect in organism clearance from the lungs with higher organism burdens and altered lung cytokine responses during Pneumocystis murina (Pm) pneumonia. Interestingly, Mincle−/− did not demonstrate worsened survival during PCP compared to wild type mice, despite the markedly increased organism burdens. This may be related to increased expression of anti-inflammatory factors such as IL-1Ra during infection in the Mincle−/− mice. Of note, the Pm infected Mincle−/− mice demonstrated increased expression of known C-type lectin receptors Dectin-1, Dectin-2, and MCL compared to infected wild type mice. Taken together, these data support a significant role for Mincle in Pneumocystis modulating host defense during infection. PMID:28298521

Selective targeting of a TNFR decoy receptor pharmaceutical to the primate brain as a receptor-specific IgG fusion protein.

PubMed

Boado, Ruben J; Hui, Eric Ka-Wai; Lu, Jeff Zhiqiang; Zhou, Qing-Hui; Pardridge, William M

2010-03-01

Decoy receptors, such as the human tumor necrosis factor receptor (TNFR), are potential new therapies for brain disorders. However, decoy receptors are large molecule drugs that are not transported across the blood-brain barrier (BBB). To enable BBB transport of a TNFR decoy receptor, the human TNFR-II extracellular domain was re-engineered as a fusion protein with a chimeric monoclonal antibody (MAb) against the human insulin receptor (HIR). The HIRMAb acts as a molecular Trojan horse to ferry the TNFR therapeutic decoy receptor across the BBB. The HIRMAb-TNFR fusion protein was expressed in stably transfected CHO cells, and was analyzed with electrophoresis, Western blotting, size exclusion chromatography, and binding assays for the HIR and TNFalpha. The HIRMAb-TNFR fusion protein was radio-labeled by trititation, in parallel with the radio-iodination of recombinant TNFR:Fc fusion protein, and the proteins were co-injected in the adult Rhesus monkey. The TNFR:Fc fusion protein did not cross the primate BBB in vivo, but the uptake of the HIRMAb-TNFR fusion protein was high and 3% of the injected dose was taken up by the primate brain. The TNFR was selectively targeted to brain, relative to peripheral organs, following fusion to the HIRMAb. This study demonstrates that decoy receptors may be re-engineered as IgG fusion proteins with a BBB molecular Trojan horse that selectively targets the brain, and enables penetration of the BBB in vivo. IgG-decoy receptor fusion proteins represent a new class of human neurotherapeutics. Copyright 2010 Elsevier B.V. All rights reserved.

BiFC Assay to Detect Calmodulin Binding to Plant Receptor Kinases.

PubMed

Fischer, Cornelia; Sauter, Margret; Dietrich, Petra

2017-01-01

Plant receptor-like kinases (RLKs) are regulated at various levels including posttranscriptional modification and interaction with regulatory proteins. Calmodulin (CaM) is a calcium-sensing protein that was shown to bind to some RLKs such as the PHYTOSULFOKINE RECEPTOR1 (PSKR1). The CaM-binding site is embedded in subdomain VIa of the kinase domain. It is possible that many more of RLKs interact with CaM than previously described. To unequivocally confirm CaM binding, several methods exist. Bimolecular fluorescence complementation (BiFC) and pull-down assays have been successfully used to study CaM binding to PSKR1 and are described in this chapter (BiFC) and in Chapter 15 (pull down). The two methods are complementary. BiFC is useful to show localization and interaction of soluble as well as of membrane-bound proteins in planta.

Utilization of Fc Receptors as a Mucosal Vaccine Strategy against an Intracellular Bacterium, Francisella tularensis1

PubMed Central

Rawool, Deepak B.; Bitsaktsis, Constantine; Li, Ying; Gosselin, Diane R.; Lin, Yili; Kurkure, Nitin V.; Metzger, Dennis W.; Gosselin, Edmund J.

2013-01-01

Numerous studies have demonstrated that targeting Ag to Fc receptors (FcR) on APCs can enhance humoral and cellular immunity. However, studies are lacking that examine both the use of FcR-targeting in generating immune protection against infectious agents and the use of FcRs in the induction of mucosal immunity. Francisella tularensis is a category A intracellular mucosal pathogen. Thus, intense efforts are underway to develop a vaccine against this organism. We hypothesized that protection against mucosal infection with F. tularensis would be significantly enhanced by targeting inactivated F. tularensis live vaccine strain (iFt) to FcRs at mucosal sites, via intranasal immunization with mAb-iFt complexes. These studies demonstrate for the first time that: 1) FcR-targeted immunogen enhances immunogen-specific IgA production and protection against subsequent infection in an IgA-dependent manner, 2) FcγR and neonatal FcR are crucial to this protection, and 3) inactivated F. tularensis, when targeted to FcRs, enhances protection against the highly virulent SchuS4 strain of F. tularensis, a category A biothreat agent. In summary, these studies show for the first time the use of FcRs as a highly effective vaccination strategy against a highly virulent mucosal intracellular pathogen. PMID:18390739

Role of polymorphic Fc receptor Fc gammaRIIa in cytokine release and adverse effects of murine IgG1 anti-CD3/T cell receptor antibody (WT31).

PubMed

Tax, W J; Tamboer, W P; Jacobs, C W; Frenken, L A; Koene, R A

1997-01-15

Anti-CD3 monoclonal antibody (mAb) OKT3 is immunosuppressive, but causes severe adverse effects during the first administration ("first-dose reaction"). These adverse effects are presumably caused by cytokine release that results from T-cell activation. In vitro, T-cell activation by anti-CD3 mAb requires interaction with monocyte Fc receptors. The Fc receptor for murine IgG1, Fc gammaRIIa, is polymorphic. In some individuals, murine IgG1 anti-CD3 mAb causes T-cell proliferation and cytokine release in vitro (high responders [HR]), whereas in individuals with the low-responder (LR) phenotype it does not. We have now investigated the role of this Fc gammaRIIa polymorphism in the release of cytokines in vivo and the occurrence of adverse effects after the administration of WT31, a murine IgG1 anti-CD3/T cell receptor mAb. WT31 caused an increase of plasma tumor necrosis factor-alpha in all four HR patients and none of the five LR patients. In all HR patients except one, plasma gamma-interferon and interleukin 6 also increased, and a first-dose response was observed, whereas no cytokine release or adverse effects occurred in any of the LR patients. WT31 caused lymphopenia in all HR and none of the LR patients. FACS analysis demonstrated that in HR patients, after the initial disappearance of CD3+ cells from peripheral blood, modulation of CD3 occurred, whereas in LR patients a high degree of coating of the lymphocytes was observed. Surprisingly, WT31 also induced a marked granulocytopenia, as well as a decrease of thrombocytes, in three of the four HR patients (and in none of the LR patients). These data provide direct clinical evidence that Fc receptor interaction determines the release of cytokines and the occurrence of adverse effects after administration of anti-CD3/T cell receptor mAb. Furthermore, these data suggest that tumor necrosis factor-alpha by itself is not sufficient to induce the first-dose reaction.

Comparative analysis of the internalization of the macrophage receptor sialoadhesin in human and mouse primary macrophages and cell lines.

PubMed

De Schryver, Marjorie; Leemans, Annelies; Pintelon, Isabel; Cappoen, Davie; Maes, Louis; Caljon, Guy; Cos, Paul; Delputte, Peter L

2017-06-01

Sialoadhesin (Sn) is a surface receptor expressed on resident macrophages with the ability to bind with sialic acids. During inflammation, an upregulation of Sn is observed. Upon binding of monoclonal antibodies to Sn, the receptor becomes internalized and this has been observed in multiple species. The latter characteristic, combined with the strong upregulation of Sn on inflammatory macrophages and the fact that Sn-positive macrophages contribute to certain inflammatory diseases, makes Sn an interesting entry portal for phenotype-modulating or cytotoxic drugs. Such drugs or toxins can be linked to Sn-specific antibodies which should enable their targeted uptake by macrophages. However, the activity of such drugs depends not only on their internalization but also on the intracellular trafficking and final fate in the endolysosomal system. Although information is available for porcine Sn, the detailed mechanisms of human and mouse Sn internalization and subsequent intracellular trafficking are currently unknown. To allow development of Sn-targeted therapies, differences across species and cellular background need to be characterized in more detail. In the current report, we show that internalization of human and mouse Sn is dynamin-dependent and clathrin-mediated, both in primary macrophages and CHO cell lines expressing a recombinant Sn. In primary macrophages, internalized Sn-specific F(ab') 2 fragments are located mostly in the early endosomes. With Fc containing Sn-specific antibodies, there is a slight shift towards lysosomal localization in mouse macrophages, possibly because of an interaction with Fc receptors. Surprisingly, in CHO cell lines expressing Sn, there is a predominant lysosomal localization. Our results show that the mechanism of Sn internalization and intracellular trafficking is concurrent in the tested species. The cellular background in which Sn is expressed and the type of antibody used can affect the intracellular fate, which in turn can impact the activity of antibody-based therapeutic interventions via Sn. Copyright © 2016 Elsevier GmbH. All rights reserved.

TTI-621 (SIRPαFc): A CD47-Blocking Innate Immune Checkpoint Inhibitor with Broad Antitumor Activity and Minimal Erythrocyte Binding.

PubMed

Petrova, Penka S; Viller, Natasja Nielsen; Wong, Mark; Pang, Xinli; Lin, Gloria H Y; Dodge, Karen; Chai, Vien; Chen, Hui; Lee, Vivian; House, Violetta; Vigo, Noel T; Jin, Debbie; Mutukura, Tapfuma; Charbonneau, Marilyse; Truong, Tran; Viau, Stephane; Johnson, Lisa D; Linderoth, Emma; Sievers, Eric L; Maleki Vareki, Saman; Figueredo, Rene; Pampillo, Macarena; Koropatnick, James; Trudel, Suzanne; Mbong, Nathan; Jin, Liqing; Wang, Jean C Y; Uger, Robert A

2017-02-15

Purpose: The ubiquitously expressed transmembrane glycoprotein CD47 delivers an anti-phagocytic (do not eat) signal by binding signal-regulatory protein α (SIRPα) on macrophages. CD47 is overexpressed in cancer cells and its expression is associated with poor clinical outcomes. TTI-621 (SIRPαFc) is a fully human recombinant fusion protein that blocks the CD47-SIRPα axis by binding to human CD47 and enhancing phagocytosis of malignant cells. Blockade of this inhibitory axis using TTI-621 has emerged as a promising therapeutic strategy to promote tumor cell eradication. Experimental Design: The ability of TTI-621 to promote macrophage-mediated phagocytosis of human tumor cells was assessed using both confocal microscopy and flow cytometry. In vivo antitumor efficacy was evaluated in xenograft and syngeneic models and the role of the Fc region in antitumor activity was evaluated using SIRPαFc constructs with different Fc tails. Results: TTI-621 enhanced macrophage-mediated phagocytosis of both hematologic and solid tumor cells, while sparing normal cells. In vivo , TTI-621 effectively controlled the growth of aggressive AML and B lymphoma xenografts and was efficacious in a syngeneic B lymphoma model. The IgG1 Fc tail of TTI-621 plays a critical role in its antitumor activity, presumably by engaging activating Fcγ receptors on macrophages. Finally, TTI-621 exhibits minimal binding to human erythrocytes, thereby differentiating it from CD47 blocking antibodies. Conclusions: These data indicate that TTI-621 is active across a broad range of human tumors. These results further establish CD47 as a critical regulator of innate immune surveillance and form the basis for clinical development of TTI-621 in multiple oncology indications. Clin Cancer Res; 23(4); 1068-79. ©2016 AACR . ©2016 American Association for Cancer Research.

Contributions of F-BAR and SH2 Domains of Fes Protein Tyrosine Kinase for Coupling to the FcɛRI Pathway in Mast Cells▿ †

PubMed Central

McPherson, Victor A.; Everingham, Stephanie; Karisch, Robert; Smith, Julie A.; Udell, Christian M.; Zheng, Jimin; Jia, Zongchao; Craig, Andrew W. B.

2009-01-01

This study investigates the roles of Fer-CIP4 homology (FCH)-Bin/amphiphysin/Rvs (F-BAR) and SH2 domains of Fes protein tyrosine kinase in regulating its activation and signaling downstream of the high-affinity immunoglobulin G (IgE) receptor (FcɛRI) in mast cells. Homology modeling of the Fes F-BAR domain revealed conservation of some basic residues implicated in phosphoinositide binding (R113/K114). The Fes F-BAR can bind phosphoinositides and induce tubulation of liposomes in vitro. Mutation of R113/K114 to uncharged residues (RK/QQ) caused a significant reduction in phosphoinositide binding in vitro and a more diffuse cytoplasmic localization in transfected COS-7 cells. RBL-2H3 mast cells expressing full-length Fes carrying the RK/QQ mutation show defects in FcɛRI-induced Fes tyrosine phosphorylation and degranulation compared to cells expressing wild-type Fes. This correlated with reduced localization to Lyn kinase-containing membrane fractions for the RK/QQ mutant compared to wild-type Fes in mast cells. The Fes SH2 domain also contributes to Fes signaling in mast cells, via interactions with the phosphorylated FcɛRI β chain and the actin regulatory protein HS1. We show that Fes phosphorylates C-terminal tyrosine residues in HS1 implicated in actin stabilization. Thus, coordinated actions of the F-BAR and SH2 domains of Fes allow for coupling to FcɛRI signaling and potential regulation the actin reorganization in mast cells. PMID:19001085

Protein tyrosine phosphatase-PEST (PTP-PEST) regulates mast cell-activating signals in PTP activity-dependent and -independent manners.

PubMed

Motohashi, Satoru; Koizumi, Karen; Honda, Reika; Maruyama, Atsuko; Palmer, Helen E F; Mashima, Keisuke

2014-01-01

Aggregation of the high-affinity IgE receptor (FcεRI) in mast cells leads to degranulation and production of numerous cytokines and lipid mediators that promote allergic inflammation. Tyrosine phosphorylation of proteins in response to FcεRI aggregation has been implicated in mast cell activation. Here, we determined the role of PTP-PEST (encoded by PTPN12) in the regulation of mast cell activation using the RBL-2H3 rat basophilic leukemia cell line as a model. PTP-PEST expression was significantly induced upon FcεRI-crosslinking, and aggregation of FcεRI induced the phosphorylation of PTP-PEST at Ser39, thus resulting in the suppression of PTP activity. By overexpressing a phosphatase-dead mutant (PTP-PEST CS) and a constitutively active mutant (PTP-PEST SA) in RBL-2H3 cells, we showed that PTP-PEST decreased degranulation and enhanced IL-4 and IL-13 transcription in FcεRI-crosslinked RBL-2H3 cells, but PTP activity of PTP-PEST was not necessary for this regulation. However, FcεRI-induced TNF-α transcription was increased by the overexpression of PTP-PEST SA and suppressed by the overexpression of PTP-PEST CS. Taken together, these results suggest that PTP-PEST is involved in the regulation of FcεRI-mediated mast cell activation through at least two different processes represented by PTP activity-dependent and -independent pathways. Copyright © 2014 Elsevier Inc. All rights reserved.

Association of C-Type Lectin Mincle with FcεRIβγ Subunits Leads to Functional Activation of RBL-2H3 Cells through Syk.

PubMed

Honjoh, Chisato; Chihara, Kazuyasu; Yoshiki, Hatsumi; Yamauchi, Shota; Takeuchi, Kenji; Kato, Yuji; Hida, Yukio; Ishizuka, Tamotsu; Sada, Kiyonao

2017-04-10

Macrophage-inducible C-type lectin (Mincle) interacts with the γ-subunit of high-affinity IgE receptor (FcεRIγ) and activates Syk by recognizing its specific ligand, trehalose-6,6'-dimycolate, a glycolipid produced by Mycobacterium tuberculosis. It has been suggested that mast cells participate in the immune defense against pathogenic microbes including M. tuberculosis, although the functions are still uncertain. In this study, we examined the Mincle-mediated signaling pathway and cellular responses using RBL-2H3 cells. Mincle formed a protein complex with not only FcεRIγ but also FcεRIβ in a stable cell line expressing myc-tagged Mincle. In addition, engagement of Mincle increased the levels of protein tyrosine phosphorylation and ERK phosphorylation. A pull-down assay demonstrated that cross-linking of Mincle induced binding of FcεRIβγ subunits to the Src homology 2 domain of Syk. Pharmacological and genetic studies indicated that activation of Syk was critical for Mincle-mediated activation of phospholipase Cγ2, leading to the activation of ERK and nuclear factor of activated T cells. Moreover, engagement of Mincle efficiently induced up-regulation of characteristic mast cell genes in addition to degranulation. Taken together, our present results suggest that mast cells contribute to Mincle-mediated immunity through Syk activation triggered by association with the FcεRIβγ complex.

Identification of CD22 Ligands on Bone Marrow Sinusoidal Endothelium Implicated in CD22-dependent Homing of Recirculating B Cells

PubMed Central

Nitschke, Lars; Floyd, Helen; Ferguson, David J.P.; Crocker, Paul R.

1999-01-01

CD22 is a B cell–specific transmembrane protein known to function as a negative regulator of B cell signaling. It has also been implicated in cell adhesion through recognition of α2,6-linked sialic acids on glycans of target cells. Previous studies showed that CD22-deficient mice had a strongly reduced population of mature recirculating B cells in the bone marrow despite normal B cell development. Using a soluble recombinant form of the receptor (CD22-Fc), we demonstrate here that sialylated ligands for CD22 are expressed on sinusoidal endothelial cells of murine bone marrow but not on endothelial cells in other tissues examined. Injection of CD22-Fc revealed that the CD22 ligands in the bone marrow were accessible to the circulation. Treatment of mice with either CD22-Fc or affinity-purified anti-CD22 antibody led to an ∼50% reduction in mature recirculating B cells in the bone marrow without affecting numbers in the spleen. Finally, consistent with the notion that CD22 is a homing receptor, we show that compared with wild-type mice, CD22-deficient animals have a lower number of immunoglobulin M–secreting plasma cells in the bone marrow. PMID:10224292

Gestation age dependent transfer of human immunoglobulins across placenta in timed-pregnant guinea pigs.

PubMed

Xu, Yanqun; Ma, Li; Norton, Malgorzata G; Stuart, Christine; Zhao, Zhong; Toibero, Denise; Dahlen, Shelby; Zhong, Lilin; Zhang, Pei; Struble, Evi B

2015-12-01

When administered during pregnancy, antibodies and other biologic drugs that contain the Fc part of the IgG molecule can traverse the placenta. Although it is generally accepted that the FcRn receptor mediates this process, gaps remain in our understanding of underlying details in humans and in common laboratory animal species. We expanded our previous studies in timed-pregnant guinea pigs to both measure the transport of human (h) IgG at earlier gestation ages in vivo and evaluate FcRn function in vitro using Surface Plasmon Resonance (SPR) and Madin-Darby canine kidney cells (MDCK) that express guinea pig (gp) FcRn. In timed-pregnant guinea pigs both the average concentration of hIgG in the fetus and its ratio to maternal hIgG concentration increase exponentially with gestation age. Thus, hIgG fetal:maternal concentration ratios increase from an average of 1% to 3%, 17%, and 76% on GD ∼26, 35, 46, and 54, respectively. In vitro, gpFcRn immobilized on a solid surface can bind hIgG and gpIgG preparations in a similar manner. All engineered human Fc isotype-specific constructs were internalized by MDCK-gpFcRn cells at significant levels. While not significant, their recycling and hIgG transcytosis by this cell line also trend higher than background controls. Pregnant guinea pigs exhibit similarities with humans in the degree and timing of transplacental transfer as well as the ability of their FcRn to bind and internalize hIgG in vitro. Further studies are needed to guide building appropriate systems for the evaluation of FcRn mediated function of human immunoglobulin therapies. Published by Elsevier Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amagai, Yosuke; Tanaka, Akane; Ohmori, Keitaro

Much is known regarding participations of mast cells with innate and acquired immunity by secreting various cytokines and chemical mediators. However, details of mast cell biology still remain unclear. In this study, we successfully established a novel growth factor-independent mast cell line (MPT-1) derived from canine mast cell tumor. MPT-1 cells manifested factor-independent proliferation as floating cells containing a large amount of histamine, as well as chymase-like dog mast cell protease 3, in cytosolic granules. Particularly, MPT-1 cells expressed high-affinity IgE receptors (Fc{epsilon}RI) and wild-type c-kit receptors. Degranulation of MPT-1 cells was induced not only by stimulation with calcium ionophoremore » but also by cross-linkage of the surface IgE. Given that MPT-1 is the first mast cell line with Fc{epsilon}RI which has no c-kit mutations, MPT-1 cells may provide great contribution for investigation of IgE-mediated activation mechanisms of mast cells, leading to development of effective treatment for allergic disorders.« less

FcγRIII in ITP: it ain't over 'til it's over.

PubMed

McCrae, Keith R

2016-01-07

In this issue of Blood, Yu et al describe a novel anti–Fcγ receptor III (FcγRIII)-albumin fusion protein that inhibits the development of thrombocytopenia in a murine model of immune thrombocytopenia (ITP).1 The unique aspect of this protein is that it blocks FcγRIII-mediated uptake of antibody-coated platelets without activating FcγRIII and the associated inflammatory response.

Chicken IgY Fc expressed by Eimeria mitis enhances the immunogenicity of E. mitis.

PubMed

Qin, Mei; Tang, Xinming; Yin, Guangwen; Liu, Xianyong; Suo, Jingxia; Tao, Geru; Ei-Ashram, Saeed; Li, Yuan; Suo, Xun

2016-03-21

Eimeria species are obligate intracellular apicomplexan parasites, causing great economic losses in the poultry industry. Currently wild-and attenuated- type anticoccidial vaccines are used to control coccidiosis. However, their use in fast growing broilers is limited by vaccination side effects caused by medium and/or low immunogenic Eimeria spp. There is, therefore, a need for a vaccine with high immunogenicity for broilers. The avian yolk sac IgY Fc is the avian counterpart of the mammalian IgG Fc, which enhances immunogenicity of Fc-fusion proteins. Here, we developed a stable transgenic Eimeria mitis expressing IgY Fc (Emi.chFc) and investigated whether the avian IgY Fc fragment enhances the immunogenicity of E. mitis. Two-week-old broilers were immunized with either Emi.chFc or wild type Eimeria and challenged with wild type E. mitis to analyze the protective properties of transgenic Emi.chFc. Chickens immunized with Emi.chFc had significantly lower oocyst output, in comparison with PBS, mock control (transgenic E. mitis expressing HA1 from H9N2 avian influenza virus) and wildtype E. mitis immunized groups after challenge, indicating that IgY Fc enhanced the immunogenicity of E. mitis. Our findings suggest that IgY Fc-expressing Eimeria may be a better coccidiosis vaccine, and transgenic Eimeria expressing Fc-fused exogenous antigens may be used as a novel vaccine-delivery vehicle against a wide variety of pathogens.

Fascaplysin sensitizes cells to TRAIL-induced apoptosis through upregulating DR5 expression

NASA Astrophysics Data System (ADS)

Wang, Feng; Chen, Haimin; Yan, Xiaojun; Zheng, Yanling

2013-05-01

This study investigated the molecular mechanism of anti-tumor effect of fascaplysin, a nitrogenous red pigment firstly isolated from a marine sponge. Microarray analysis show that the TNF and TNF receptor superfamily in human umbilical vein endothelial cells (HUVEC) and human hepatocarcinoma cells (BEL-7402) were significantly regulated by fascaplysin. Western Blot results reveal that fascaplysin increased the expression of cleaved caspase-9, active caspase-3, and decreased the level of procaspase-8 and Bid. Flow cytometry and cytotoxicity tests indicate that fascaplysin sensitized cells to tumor necrosis-related apoptosisinducing ligand-(TRAIL) induced apoptosis, which was markedly blocked by TRAIL R2/Fc chimera, a dominant negative form of TRAIL receptor DR5. Therefore, our results demonstrate that fascaplysin promotes apoptosis through the activation of TRAIL signaling pathway by upregulating DR5 expression.

Signals of monocyte activation in patients with SLE.

PubMed Central

Kávai, M; Zsindely, A; Sonkoly, I; Major, M; Demján, I; Szegedi, G

1983-01-01

The Fc receptor mediated reaction, the beta-glucuronidase and the lactic dehydrogenase activities of monocytes and the serum lysozyme level were tested together with the circulating immune complex content of patients with systemic lupus erythematosus. Simultaneously with the increasing FC receptor-mediated reaction and the elevated enzyme activities of patient monocytes, the secretion of lysozyme and the immune complex content of the sera were higher than those of the controls. A positive correlation was demonstrated between the Fc receptor-mediated reaction, the beta-glucuronidase activity, the lysozyme secretion and the immune complex content of the sera. Thus, the monocytes of patients appeared to be activated by the circulating immune complexes. PMID:6839541

Evidence for an asialoglycoprotein receptor on nonparenchymal cells for O-linked glycoproteins.

PubMed

Stefanich, Eric G; Ren, Song; Danilenko, Dimitry M; Lim, Amy; Song, An; Iyer, Suhasini; Fielder, Paul J

2008-11-01

B cell-activating factor receptor 3 (BR3)-Fc is an IgG1-receptor dimeric fusion protein that has multiple O-linked glycosylation sites and sialylation levels that can vary in the manufacturing process. Increased sialic acid levels resulted from increased site occupancy with the O-linked N-acetylgalactosamine (GalNAc-Gal), but because the ratio of sialic acid per mole of oligosaccharide remained approximately 1, this led to increased asialo terminal GalNAc. Previous studies have demonstrated an effect of terminal asialo Gal or GalNAc on the clearance of glycoproteins due to uptake and degradation by lectin receptors in the liver. However, the previous studies examined N-linked oligosaccharides, and there are less data regarding O-linked oligosaccharides. The objective of these studies was to determine the effects on the pharmacokinetics and distribution of the asialo terminal GalNAc and varying amounts of sialic acid residues on BR3-Fc. The results of the data presented here suggest that exposed Gal on the desialylated BR3-Fc led to rapid clearance due to uptake and degradation in the liver that was associated with nonparenchymal cells. It is interesting to note that the data indicated a decreased clearance and increased exposure of BR3-Fc as the sialic acid levels increased, even though increased sialic acid was associated with increased asialo GalNAc. Therefore, the exposed GalNAc did not seem to play a role in the clearance of BR3-Fc; although the Gal linked to the hydroxyl group at position 3 may have prevented an interaction. Because we did not see uptake of desialylated BR3-Fc in hepatocytes where the asialoglycoprotein receptor is localized, this nonparenchymal cell lectin may have preference for O-linked glycoproteins.

Transgenic Tobacco Lines Expressing Sense or Antisense FERROCHELATASE 1 RNA Show Modified Ferrochelatase Activity in Roots and Provide Experimental Evidence for Dual Localization of Ferrochelatase 1.

PubMed

Hey, Daniel; Ortega-Rodes, Patricia; Fan, Tingting; Schnurrer, Florian; Brings, Lea; Hedtke, Boris; Grimm, Bernhard

2016-12-01

In plants, two genes encode ferrochelatase (FC), which catalyzes iron chelation into protoporphyrin IX at the final step of heme biosynthesis. FERROCHELATASE1 (FC1) is continuously, but weakly expressed in roots and leaves, while FC2 is dominantly active in leaves. As a continuation of previous studies on the physiological consequences of FC2 inactivation in tobacco, we aimed to assign FC1 function in plant organs. While reduced FC2 expression leads to protoporphyrin IX accumulation in leaves, FC1 down-regulation and overproduction caused reduced and elevated FC activity in root tissue, respectively, but were not associated with changes in macroscopic phenotype, plant development or leaf pigmentation. In contrast to the lower heme content resulting from a deficiency of the dominant FC2 expression in leaves, a reduction of FC1 in roots and leaves does not significantly disturb heme accumulation. The FC1 overexpression was used for an additional approach to re-examine FC activity in mitochondria. Transgenic FC1 protein was immunologically shown to be present in mitochondria. Although matching only a small portion of total cellular FC activity, the mitochondrial FC activity in a FC1 overexpressor line increased 5-fold in comparison with wild-type mitochondria. Thus, it is suggested that FC1 contributes to mitochondrial heme synthesis. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

M. tuberculosis-Initiated Human Mannose Receptor Signaling Regulates Macrophage Recognition and Vesicle Trafficking by FcRγ-Chain, Grb2, and SHP-1.

PubMed

Rajaram, Murugesan V S; Arnett, Eusondia; Azad, Abul K; Guirado, Evelyn; Ni, Bin; Gerberick, Abigail D; He, Li-Zhen; Keler, Tibor; Thomas, Lawrence J; Lafuse, William P; Schlesinger, Larry S

2017-10-03

Despite its prominent role as a C-type lectin (CTL) pattern recognition receptor, mannose receptor (MR, CD206)-specific signaling molecules and pathways are unknown. The MR is highly expressed on human macrophages, regulating endocytosis, phagocytosis, and immune responses and mediating Mycobacterium tuberculosis (M.tb) phagocytosis by human macrophages, thereby limiting phagosome-lysosome (P-L) fusion. We identified human MR-associated proteins using phosphorylated and non-phosphorylated MR cytoplasmic tail peptides. We found that MR binds FcRγ-chain, which is required for MR plasma membrane localization and M.tb cell association. Additionally, we discovered that MR-mediated M.tb association triggers immediate MR tyrosine residue phosphorylation and Grb2 recruitment, activating the Rac/Pak/Cdc-42 signaling cascade important for M.tb uptake. MR activation subsequently recruits SHP-1 to the M.tb-containing phagosome, where its activity limits PI(3)P generation at the phagosome and M.tb P-L fusion and promotes M.tb growth. In sum, we identify human MR signaling pathways that temporally regulate phagocytosis and P-L fusion during M.tb infection. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Possible orientational constraints determine secretory signals induced by aggregation of IgE receptors on mast cells.

PubMed Central

Ortega, E; Schweitzer-Stenner, R; Pecht, I

1988-01-01

Three biologically active monoclonal antibodies (mAbs) specific for the monovalent, high-affinity membrane receptor for IgE (Fc epsilon R) were employed in analysing the secretory response of mast cells of the RBL-2H3 line to crosslinking of their Fc epsilon R. All three mAbs (designated F4, H10 and J17) compete with each other and with IgE for binding to the Fc epsilon R. Their stoichiometry of binding is 1 Fab:1 Fc epsilon R, hence, the intact mAbs can aggregate the Fc epsilon Rs to dimers only. Since all three mAbs induce secretion, we conclude that Fc epsilon R dimers constitute a sufficient 'signal element' for secretion of mediators for RBL-2H3 cells. The secretory dose-response of the cells to these three mAbs are, however, markedly different: F4 caused rather high secretion, reaching almost 80% of the cells' content, while J17 and H10 induced release of only 30-40% mediators content. Both the intrinsic affinities and equilibrium constants for the receptor dimerization were derived from analysis of binding data of the Fab fragments and intact mAbs. These parameters were used to compute the extent of Fc epsilon R dimerization caused by each of the antibodies. However, the different secretory responses to the three mAbs could not be rationalized simply in terms of the extent of Fc epsilon R dimerization which they produce. This suggests that it is not only the number of crosslinked Fc epsilon Rs which determines the magnitude of secretion-causing signal, but rather other constraints imposed by each individual mAb are also important.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2977332

Molecular determinants of dengue virus 2 envelope protein important for virus entry in FcγRIIA-mediated antibody-dependent enhancement of infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chotiwan, Nunya; Roehrig, John T.; Schlesinger, Jacob J.

Antibody-dependent enhancement (ADE) of infection may cause severe illness in patients suffering a secondary infection by a heterologous dengue virus (DENV) serotype. During ADE of infection, cross-reactive non- or poorly-neutralizing antibodies form infectious virus-Ab complexes with the newly infecting serotype and enhance virus infection by binding to the Fcγ receptors (FcγR) on FcγR-bearing cells. In this study, we determined that molecular determinants of DENV2 envelope protein critical for virus entry during non-ADE infection are also required for ADE infection mediated by FcγRIIA, and binding of virus-Ab complexes with FcγRIIA alone is not sufficient for ADE of infection. The FcγRIIA mainlymore » plays an auxiliary role in concentrating the virus–Ab complex to the cell surface, and other primary cellular receptors are required for virus entry. Understanding the viral entry pathway in ADE of DENV infection will greatly facilitate rational designs of anti-viral therapeutics against severe dengue disease associated with ADE. - Highlights: • KKK305/307/310 in DENV2 E-DIII is critical for virus attachment in ADE and non-ADE infection. • Binding of DENV2–Ab complex with FcγRII alone is not sufficient for virus entry in ADE infection. • Other primary receptors were required for DENV2 internalization during FcγRII–mediated ADE. • G104 and L135 of DENV2 E are critical for virus-mediated membrane fusion. • DENV2 virus-mediated membrane fusion is required for both ADE and non-ADE infection.« less

Regulation by CD45 of the tyrosine phosphorylation of high affinity IgE receptor beta- and gamma-chains.

PubMed

Adamczewski, M; Numerof, R P; Koretzky, G A; Kinet, J P

1995-04-01

Previous studies using tyrosine phosphatase inhibitors have implicated tyrosine phosphatases in the signal transduction pathway initiated by aggregation of Fc epsilon RI, the high affinity receptor for IgE. To define more precisely a role for the tyrosine phosphatase CD45 in Fc epsilon RI-mediated signaling, we have transfected the three subunits of Fc epsilon RI into wild-type Jurkat and a CD45-deficient Jurkat derivative. Here we demonstrate that CD45 is necessary for the initiation of calcium flux through the transfected Fc epsilon RI. In contrast to the effect of phosphatase inhibitors, the tyrosine phosphorylation levels of beta and gamma after aggregation of Fc epsilon RI are surprisingly reduced, relative to wild-type Jurkat, in the CD45-deficient cells. After reconstitution of the CD45-deficient cells with a chimeric molecule containing the cytoplasmic phosphatase domains of CD45, both the base line and activation-induced tyrosine phosphorylation levels are increased. By examining Lck autophosphorylation, we find that Fc epsilon RI aggregation induces an increase in Lck enzymatic activity only in wild-type Jurkat and the CD45-deficient Jurkat reconstituted with chimeric CD45. This regulation of src-family tyrosine kinase activity may be the means by which CD45 controls aggregation-induced receptor phosphorylation.

Autoantibody-induced internalization of CNS AQP4 water channel and EAAT2 glutamate transporter requires astrocytic Fc receptor.

PubMed

Hinson, Shannon R; Clift, Ian C; Luo, Ningling; Kryzer, Thomas J; Lennon, Vanda A

2017-05-23

Aquaporin-4 (AQP4) water channel-specific IgG distinguishes neuromyelitis optica (NMO) from multiple sclerosis and causes characteristic immunopathology in which central nervous system (CNS) demyelination is secondary. Early events initiating the pathophysiological outcomes of IgG binding to astrocytic AQP4 are poorly understood. CNS lesions reflect events documented in vitro following IgG interaction with AQP4: AQP4 internalization, attenuated glutamate uptake, intramyelinic edema, interleukin-6 release, complement activation, inflammatory cell recruitment, and demyelination. Here, we demonstrate that AQP4 internalization requires AQP4-bound IgG to engage an astrocytic Fcγ receptor (FcγR). IgG-lacking Fc redistributes AQP4 within the plasma membrane and induces interleukin-6 release. However, AQP4 endocytosis requires an activating FcγR's gamma subunit and involves astrocytic membrane loss of an inhibitory FcγR, CD32B. Interaction of the IgG-AQP4 complex with FcγRs triggers coendocytosis of the excitatory amino acid transporter 2 (EAAT2). Requirement of FcγR engagement for internalization of two astrocytic membrane proteins critical to CNS homeostasis identifies a complement-independent, upstream target for potential early therapeutic intervention in NMO.

Generation of Mast Cells from Mouse Fetus: Analysis of Differentiation and Functionality, and Transcriptome Profiling Using Next Generation Sequencer

PubMed Central

Fukuishi, Nobuyuki; Igawa, Yuusuke; Kunimi, Tomoyo; Hamano, Hirofumi; Toyota, Masao; Takahashi, Hironobu; Kenmoku, Hiromichi; Yagi, Yasuyuki; Matsui, Nobuaki; Akagi, Masaaki

2013-01-01

While gene knockout technology can reveal the roles of proteins in cellular functions, including in mast cells, fetal death due to gene manipulation frequently interrupts experimental analysis. We generated mast cells from mouse fetal liver (FLMC), and compared the fundamental functions of FLMC with those of bone marrow-derived mouse mast cells (BMMC). Under electron microscopy, numerous small and electron-dense granules were observed in FLMC. In FLMC, the expression levels of a subunit of the FcεRI receptor and degranulation by IgE cross-linking were comparable with BMMC. By flow cytometry we observed surface expression of c-Kit prior to that of FcεRI on FLMC, although on BMMC the expression of c-Kit came after FcεRI. The surface expression levels of Sca-1 and c-Kit, a marker of putative mast cell precursors, were slightly different between bone marrow cells and fetal liver cells, suggesting that differentiation stage or cell type are not necessarily equivalent between both lineages. Moreover, this indicates that phenotypically similar mast cells may not have undergone an identical process of differentiation. By comprehensive analysis using the next generation sequencer, the same frequency of gene expression was observed for 98.6% of all transcripts in both cell types. These results indicate that FLMC could represent a new and useful tool for exploring mast cell differentiation, and may help to elucidate the roles of individual proteins in the function of mast cells where gene manipulation can induce embryonic lethality in the mid to late stages of pregnancy. PMID:23573287

CD14(hi)CD16+ monocytes phagocytose antibody-opsonised Plasmodium falciparum infected erythrocytes more efficiently than other monocyte subsets, and require CD16 and complement to do so.

PubMed

Zhou, Jingling; Feng, Gaoqian; Beeson, James; Hogarth, P Mark; Rogerson, Stephen J; Yan, Yan; Jaworowski, Anthony

2015-07-07

With more than 600,000 deaths from malaria, mainly of children under five years old and caused by infection with Plasmodium falciparum, comes an urgent need for an effective anti-malaria vaccine. Limited details on the mechanisms of protective immunity are a barrier to vaccine development. Antibodies play an important role in immunity to malaria and monocytes are key effectors in antibody-mediated protection by phagocytosing antibody-opsonised infected erythrocytes (IE). Eliciting antibodies that enhance phagocytosis of IE is therefore an important potential component of an effective vaccine, requiring robust assays to determine the ability of elicited antibodies to stimulate this in vivo. The mechanisms by which monocytes ingest IE and the nature of the monocytes which do so are unknown. Purified trophozoite-stage P. falciparum IE were stained with ethidium bromide, opsonised with anti-erythrocyte antibodies and incubated with fresh whole blood. Phagocytosis of IE and TNF production by individual monocyte subsets was measured by flow cytometry. Ingestion of IE was confirmed by imaging flow cytometry. CD14(hi)CD16+ monocytes phagocytosed antibody-opsonised IE and produced TNF more efficiently than CD14(hi)CD16- and CD14(lo)CD16+ monocytes. Blocking experiments showed that Fcγ receptor IIIa (CD16) but not Fcγ receptor IIa (CD32a) or Fcγ receptor I (CD64) was necessary for phagocytosis. CD14(hi)CD16+ monocytes ingested antibody-opsonised IE when peripheral blood mononuclear cells were reconstituted with autologous serum but not heat-inactivated autologous serum. Antibody-opsonised IE were rapidly opsonised with complement component C3 in serum (t1/2 = 2-3 minutes) and phagocytosis of antibody-opsonised IE was inhibited in a dose-dependent manner by an inhibitor of C3 activation, compstatin. Compared to other monocyte subsets, CD14(hi)CD16+ monocytes expressed the highest levels of complement receptor 4 (CD11c) and activated complement receptor 3 (CD11b) subunits. We show a special role for CD14(hi)CD16+ monocytes in phagocytosing opsonised P. falciparum IE and production of TNF. While ingestion was mediated by Fcγ receptor IIIa, this receptor was not sufficient to allow phagocytosis; despite opsonisation with antibody, phagocytosis of IE also required complement opsonisation. Assays which measure the ability of vaccines to elicit a protective antibody response to P. falciparum should consider their ability to promote phagocytosis and fix complement.

AMPKα, hs-CRP and FcγR in diabetic nephropathy and drug intervention.

PubMed

Sun, Ping; Lu, Lei; Chen, Jun; Liu, Xiao Dan; Zhang, Qing; Wang, Xu

2018-06-01

The aim of this study was to investigate the roles of AMP-activated protein kinase α subunit (AMPKα), hypersensitive C-reactive protein (hs-CRP) and Fcγ receptor (FcγR) in diabetic nephropathy and drug intervention effects. Sixty Sprague Dawley male rats were randomly divided into the control (n=30) and observation (n=30) groups. The model of type 2 diabetic nephropathy was established by high-fat and high-glucose diet and streptozotocin injection. The rats in the observation group were treated with baicalein and the rats in control group did not receive any drug intervention. The pathological changes of kidneys were observed by hematoxylin and eosin (H&E) staining. The expression of AMPKα mRNA in renal tissue was detected by reverse transcription-polymerase chain reaction (RT-PCR). The levels of hs-CRP and FcγR were measured by enzyme-linked immunosorbent assay (ELISA) at 1, 4, 6 and 8 weeks after drug intervention and blood urea nitrogen (BUN) and the 24 h urinary micro-albumin (U-ALB) levels were compared at 1, 4, 6 and 8 weeks after intervention. After 8 weeks of drug intervention, the pathological changes of kidneys in the observation group were significantly lower than those in the control group (p<0.05), while the relative expression levels of AMPKα mRNA and protein in the control group were higher than those in the observation group (p<0.05). The levels of hs-CRP, BUN and 24 h U-ALB in the control group were significantly higher than those in the observation group at different time-points after drug intervention and the level of FcγR in the control group was significantly lower than that in the observation group (p<0.05). Baicalein may protect renal function by inhibiting the expression of AMPKα and inflammatory reaction, and can also decrease BUN and 24 h U-ALB levels and improve the pathological changes of the kidney.

β1,4-galactosyltransferase 1 is a novel receptor for IgA in human mesangial cells.

PubMed

Molyneux, Karen; Wimbury, David; Pawluczyk, Izabella; Muto, Masahiro; Bhachu, Jasraj; Mertens, Peter R; Feehally, John; Barratt, Jonathan

2017-12-01

IgA nephropathy is characterized by mesangial deposition of IgA, mesangial cell proliferation, and extracellular matrix production. Mesangial cells bind IgA, but the identity of all potential receptors involved remains incomplete. The transferrin receptor (CD71) acts as a mesangial cell IgA receptor and its expression is upregulated in many forms of glomerulonephritis, including IgA nephropathy. CD71 is not expressed in healthy glomeruli and blocking CD71 does not completely abrogate mesangial cell IgA binding. Previously we showed that mesangial cells express a receptor that binds the Fc portion of IgA and now report that this receptor is an isoform of β-1,4-galactosyltransferase. A human mesangial cell cDNA library was screened for IgA binding proteins and β-1,4-galactosyltransferase identified. Cell surface expression of the long isoform of β-1,4-galactosyltransferase was shown by flow cytometry and confocal microscopy and confirmed by immunoblotting. Glomerular β-1,4-galactosyltransferase expression was increased in IgA nephropathy. IgA binding and IgA-induced mesangial cell phosphorylation of spleen tyrosine kinase and IL-6 synthesis were inhibited by a panel of β-1,4-galactosyltransferase-specific antibodies, suggesting IgA binds to the catalytic domain of β-1,4-galactosyltransferase. Thus, β-1,4-galactosyltransferase is a constitutively expressed mesangial cell IgA receptor with an important role in both mesangial IgA clearance and the initial response to IgA deposition. Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Changes in complementarity-determining regions significantly alter IgG binding to the neonatal Fc receptor (FcRn) and pharmacokinetics

PubMed Central

King, Amy C.; Kavosi, Mania; Wang, Mengmeng; O'Hara, Denise M.; Tchistiakova, Lioudmila; Katragadda, Madan

2018-01-01

ABSTRACT A large body of data exists demonstrating that neonatal Fc receptor (FcRn) binding of an IgG via its Fc CH2-CH3 interface trends with the pharmacokinetics (PK) of IgG. We have observed that PK of IgG molecules vary widely, even when they share identical Fc domains. This led us to hypothesize that domains distal from the Fc could contribute to FcRn binding and affect PK. In this study, we explored the role of these IgG domains in altering the affinity between IgG and FcRn. Using a surface plasmon resonance-based assay developed to examine the steady-state binding affinity (KD) of IgG molecules to FcRn, we dissected the contributions of IgG domains in modulating the affinity between FcRn and IgG. Through analysis of a broad collection of therapeutic antibodies containing more than 50 unique IgG molecules, we demonstrated that variable domains, and in particular complementarity-determining regions (CDRs), significantly alter binding affinity to FcRn in vitro. Furthermore, a panel of IgG molecules differing only by 1–5 mutations in CDRs altered binding affinity to FcRn in vitro, by up to 79-fold, and the affinity values correlated with calculated isoelectric point values of both variable domains and CDR-L3. In addition, tighter affinity values trend with faster in vivo clearance of a set of IgG molecules differing only by 1–3 mutations in human FcRn transgenic mice. Understanding the role of CDRs in modulation of IgG affinity to FcRn in vitro and their effect on PK of IgG may have far-reaching implications in the optimization of IgG therapeutics. PMID:28991504

The Role of FcRn in Antigen Presentation

PubMed Central

Baker, Kristi; Rath, Timo; Pyzik, Michal; Blumberg, Richard S.

2014-01-01

Immunoglobulins are unique molecules capable of simultaneously recognizing a diverse array of antigens and themselves being recognized by a broad array of receptors. The abundance specifically of the IgG subclass and the variety of signaling receptors to which it binds render this an important immunomodulatory molecule. In addition to the classical Fcγ receptors that bind IgG at the cell surface, the neonatal Fc receptor (FcRn) is a lifelong resident of the endolysosomal system of most hematopoietic cells where it determines the intracellular fate of both IgG and IgG-containing immune complexes (IgG IC). Cross-linking of FcRn by multivalent IgG IC within antigen presenting cells such as dendritic cells initiates specific mechanisms that result in trafficking of the antigen-bearing IgG IC into compartments from which the antigen can successfully be processed into peptide epitopes compatible with loading onto both major histocompatibility complex class I and II molecules. In turn, this enables the synchronous activation of both CD4+ and CD8+ T cell responses against the cognate antigen, thereby bridging the gap between the humoral and cellular branches of the adaptive immune response. Critically, FcRn-driven T cell priming is efficient at very low doses of antigen due to the exquisite sensitivity of the IgG-mediated antigen delivery system through which it operates. FcRn-mediated antigen presentation has important consequences in tissue compartments replete with IgG and serves not only to determine homeostatic immune activation at a variety of sites but also to induce inflammatory responses upon exposure to antigens perceived as foreign. Therapeutically targeting the pathway by which FcRn enables T cell activation in response to IgG IC is thus a highly attractive prospect not only for the treatment of diseases that are driven by immune complexes but also for manipulating local immune responses against defined antigens such as those present during infections and cancer. PMID:25221553

Induction of apoptosis in breast cancer cells in vitro by Fas ligand reverse signaling.

PubMed

Kolben, Thomas; Jeschke, Udo; Reimer, Toralf; Karsten, Nora; Schmoeckel, Elisa; Semmlinger, Anna; Mahner, Sven; Harbeck, Nadia; Kolben, Theresa M

2018-02-01

The Fas-antigen is a cell surface receptor that transduces apoptotic signals into cells. The purpose of this study was to evaluate FasL expression in breast cancer and to elucidate the role of its signaling in different breast cancer cell lines. T47D and MCF7 cells were used and cultured in Dulbecco's modified Eagle's medium. FasL translocation to the membrane was achieved by culturing the cells in the presence of human interferon-γ (IFNγ). Translocation was detected by immunofluorescence. The ability of a Fas:Fc fusion protein to trigger apoptosis in these cells was investigated by cell death detection ELISA. After incubation with IFNγ for 4 h and 18 h, apoptosis was assessed in response to treatment with Fas:Fc. Immunofluorescence revealed that the used cell lines were positive for FasL which was increased and changed to more membrane-bound FasL expression after IFNγ stimulation. After stimulation with 50 IU/ml IFNγ, Fas:Fc significantly increased MCF7 apoptosis (1.39 ± 0.06-fold, p = 0.0004) after 18 h. After stimulation with 100 IU/ml, Fas:Fc significantly increased apoptosis both after 4 h (1.49 ± 0.15-fold, p = 0.018) and 18 h (1.30 ± 0.06-fold, p = 0.013). In T47D cells this effect was seen after 4 h of stimulation with 50 IU/ml and addition of Fas:Fc (1.6 ± 0.08-fold, p = 0.03). Membrane-bound FasL expression could be induced by IFNγ in a breast cancer cell model. More importantly, in the presence of IFNγ the Fas:Fc fusion protein was able to transmit pro-apoptotic signals to T47D and MCF7 cells, significantly inducing apoptosis. The current findings support further in vivo studies regarding FasL activation as a potential target for therapeutic intervention in breast cancer.

Evaluation of Human FcγRIIA (CD32) and FcγRIIIB (CD16) Polymorphisms in Caucasians and African-Americans Using Salivary DNA

PubMed Central

van Schie, Rob C. A. A.; Wilson, Mark E.

2000-01-01

Two classes of low-affinity receptors for the Fc region of immunoglobulin G (IgG) (FcγR) are constitutively expressed on resting human neutrophils. These receptors, termed FcγRIIa (CD32) and FcγRIIIb (CD16), display biallelic polymorphisms which have functional consequences with respect to binding and/or ingestion of targets opsonized by human IgG subclass antibodies. The H131-R131 polymorphism of CD32 influences binding of human IgG2 and, to a lesser extent, human IgG3 to neutrophils. The neutrophil antigen (NA1-NA2) polymorphism of CD16 influences the efficiency of phagocytosis of bacteria opsonized by human IgG1 and IgG3. These polymorphisms may influence host susceptibility to certain infectious and/or autoimmune diseases, prompting interest in the development of facile methods for determination of CD32 and CD16 genotype in various clinical settings. We previously reported that genomic DNA from saliva is a suitable alternative to DNA from blood in PCR-based analyses of CD32 and CD16 polymorphisms. In the present study, we utilized for the first time this salivary DNA-based methodology to define CD32 and CD16 genotypes in 271 Caucasian and 118 African-American subjects and to investigate possible linkage disequilibrium between certain CD32 and CD16 genotypes in these two ethnic groups. H131 and R131 gene frequencies were 0.45 and 0.55, respectively, among Caucasians and 0.59 among African-Americans. NA1 and NA2 gene frequencies were 0.38 and 0.62 among Caucasians and 0.39 and 0.61 among African-Americans. Since FcγRIIa and FcγRIIIb synergize in triggering neutrophils, we also assessed the frequency of different CD32 and CD16 genotype combinations in these two groups. In both groups, the R/R131-NA2/NA2 genotype combination was more common than the H/H131-NA1/NA1 combination (threefold for Caucasians versus sevenfold for African-Americans). Whether individuals with the combined R/R131-NA2/NA2 genotype are at greater risk for development of infectious and/or autoimmune diseases requires further investigation, which can be conveniently performed using DNA from saliva rather than blood. PMID:10882671

Cross-species analysis of Fc engineered anti-Lewis-Y human IgG1 variants in human neonatal receptor transgenic mice reveal importance of S254 and Y436 in binding human neonatal Fc receptor

PubMed Central

Burvenich, Ingrid J. G.; Farrugia, William; Lee, Fook T.; Catimel, Bruno; Liu, Zhanqi; Makris, Dahna; Cao, Diana; O'Keefe, Graeme J.; Brechbiel, Martin W.; King, Dylan; Spirkoska, Violeta; Allan, Laura C.; Ramsland, Paul A.; Scott, Andrew M.

2016-01-01

ABSTRACT IgG has a long half-life through engagement of its Fc region with the neonatal Fc receptor (FcRn). The FcRn binding site on IgG1 has been shown to contain I253 and H310 in the CH2 domain and H435 in the CH3 domain. Altering the half-life of IgG has been pursued with the aim to prolong or reduce the half-life of therapeutic IgGs. More recent studies have shown that IgGs bind differently to mouse and human FcRn. In this study we characterize a set of hu3S193 IgG1 variants with mutations in the FcRn binding site. A double mutation in the binding site is necessary to abrogate binding to murine FcRn, whereas a single mutation in the FcRn binding site is sufficient to no longer detect binding to human FcRn and create hu3S193 IgG1 variants with a half-life similar to previously studied hu3S193 F(ab')2 (t1/2β, I253A, 12.23 h; H310A, 12.94; H435A, 12.57; F(ab')2, 12.6 h). Alanine substitutions in S254 in the CH2 domain and Y436 in the CH3 domain showed reduced binding in vitro to human FcRn and reduced elimination half-lives in huFcRn transgenic mice (t1/2β, S254A, 37.43 h; Y436A, 39.53 h; wild-type, 83.15 h). These variants had minimal effect on half-life in BALB/c nu/nu mice (t1/2β, S254A, 119.9 h; Y436A, 162.1 h; wild-type, 163.1 h). These results provide insight into the interaction of human Fc by human FcRn, and are important for antibody-based therapeutics with optimal pharmacokinetics for payload strategies used in the clinic. PMID:27030023

Regulation of the steady state level of Fc gamma RI mRNA by IFN-gamma and dexamethasone in human monocytes, neutrophils, and U-937 cells.

PubMed

Pan, L Y; Mendel, D B; Zurlo, J; Guyre, P M

1990-07-01

The high affinity IgG FcR Fc gamma RI, CD64, plays important roles in the immune response. Fc gamma RI is predominantly expressed on monocytes and macrophages, and barely detectable on neutrophils. rIFN-gamma markedly increases the expression of Fc gamma RI on neutrophils, monocytes, macrophages and myeloid cell lines such as U-937, HL-60, and THP-1. Glucocorticoids inhibit the augmentation of Fc gamma RI expression by rIFN-gamma on neutrophils and myeloid cell lines, but enhance the augmentation of Fc gamma RI expression by rIFN-gamma on monocytes. In this study, we examined the effect of rIFN-gamma and dexamethasone (Dex) on the steady state level of Fc gamma RI mRNA in U-937 cells, neutrophils, and monocytes by hybridizing total RNA with the Fc gamma RI cDNA probe, p135. We found that the amount of Fc gamma RI mRNA increased within 1 h of treatment with rIFN-gamma in all three cell types. This initial induction of Fc gamma RI mRNA by rIFN-gamma was completely blocked by an inhibitor of RNA synthesis, actinomycin D, suggesting that the rIFN-gamma-mediated induction of Fc gamma RI mRNA is dependent on gene transcription. Dex, used in combination with rIFN-gamma, partially blocked the induction of Fc gamma RI mRNA by rIFN-gamma in U-937 cells and neutrophils, but caused a synergistic increase in Fc gamma RI mRNA levels in monocytes. The inhibitory effect of Dex on the steady state level of Fc gamma RI mRNA in U-937 cells was blocked by an inhibitor of protein synthesis, cycloheximide, suggesting that Dex-induced proteins were involved in the regulation of Fc gamma RI expression. This study indicates that the regulation of Fc gamma RI expression on U-937 cells, neutrophils, and monocytes by rIFN-gamma and Dex occurs, at least in part, at the mRNA level. rIFN-gamma increases the steady state level of Fc gamma RI mRNA through a common pathway among U-937 cells, neutrophils, and monocytes, whereas the effect of Dex on rIFN-gamma-induced Fc gamma RI mRNA is cell-type specific.

Structural basis for pH-insensitive inhibition of immunoglobulin G recycling by an anti-neonatal Fc receptor antibody

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenniston, Jon A.; Taylor, Brandy M.; Conley, Gregory P.

The neonatal Fc receptor FcRn plays a critical role in the trafficking of IgGs across tissue barriers and in retaining high circulating concentrations of both IgG and albumin. Although generally beneficial from an immunological perspective in maintaining IgG populations, FcRn can contribute to the pathogenesis of autoimmune disorders when an abnormal immune response targets normal biological components. We previously described a monoclonal antibody (DX-2507) that binds to FcRn with high affinity at both neutral and acidic pH, prevents the simultaneous binding of IgG, and reduces circulating IgG levels in preclinical animal models. Here, we report a 2.5 Å resolution X-raymore » crystal structure of an FcRn–DX-2507 Fab complex, revealing a nearly complete overlap of the IgG–Fc binding site in FcRn by complementarity-determining regions in DX-2507. This overlap explains how DX-2507 blocks IgG binding to FcRn and thereby shortens IgG half-life by preventing IgGs from recycling back into circulation. Moreover, the complex structure explains how the DX-2507 interaction is pH-insensitive unlike normal Fc interactions and how serum albumin levels are unaffected by DX-2507 binding. These structural studies could inform antibody-based therapeutic approaches for limiting the effects of IgG-mediated autoimmune disease.« less

Disrupted functional connectivity of the hippocampus in patients with hyperthyroidism: evidence from resting-state fMRI.

PubMed

Zhang, Wei; Liu, Xianjun; Zhang, Yi; Song, Lingheng; Hou, Jingming; Chen, Bing; He, Mei; Cai, Ping; Lii, Haitao

2014-10-01

The hippocampus expresses high levels of thyroid hormone receptors, suggesting that hippocampal functions, including cognition and regulation of mood, can be disrupted by thyroid pathology. Indeed, structural and functional alterations within the hippocampus have been observed in hyperthyroid patients. In addition to internal circuitry, hippocampal processing is dependent on extensive connections with other limbic and neocortical structures, but the effects of hyperthyroidism on functional connectivity (FC) with these areas have not been studied. The purpose of this study was to investigate possible abnormalities in the FC between the hippocampus and other neural structures in hyperthyroid patients using resting-state fMRI. Seed-based correlation analysis was performed on resting-state fMRI data to reveal possible differences in hippocampal FC between hyperthyroid patients and healthy controls. Correlation analysis was used to investigate the relationships between the strength of FC in regions showing significant group differences and clinical variables. Compared to controls, hyperthyroid patients showed weaker FC between the bilateral hippocampus and both the bilateral anterior cingulate cortex (ACC) and bilateral posterior cingulate cortex (PCC), as well as between the right hippocampus and right medial orbitofrontal cortex (mOFC). Disease duration was negatively correlated with FC strength between the bilateral hippocampus and bilateral ACC and PCC. Levels of depression and anxiety were negatively correlated with FC strength between the bilateral hippocampus and bilateral ACC. Decreased functional connectivity between the hippocampus and bilateral ACC, PCC, and right mOFC may contribute to the emotional and cognitive dysfunction associated with hyperthyroidism. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

The number and distribution of AMPA receptor channels containing fast kinetic GluA3 and GluA4 subunits at auditory nerve synapses depend on the target cells.

PubMed

Rubio, María E; Matsui, Ko; Fukazawa, Yugo; Kamasawa, Naomi; Harada, Harumi; Itakura, Makoto; Molnár, Elek; Abe, Manabu; Sakimura, Kenji; Shigemoto, Ryuichi

2017-11-01

The neurotransmitter receptor subtype, number, density, and distribution relative to the location of transmitter release sites are key determinants of signal transmission. AMPA-type ionotropic glutamate receptors (AMPARs) containing GluA3 and GluA4 subunits are prominently expressed in subsets of neurons capable of firing action potentials at high frequencies, such as auditory relay neurons. The auditory nerve (AN) forms glutamatergic synapses on two types of relay neurons, bushy cells (BCs) and fusiform cells (FCs) of the cochlear nucleus. AN-BC and AN-FC synapses have distinct kinetics; thus, we investigated whether the number, density, and localization of GluA3 and GluA4 subunits in these synapses are differentially organized using quantitative freeze-fracture replica immunogold labeling. We identify a positive correlation between the number of AMPARs and the size of AN-BC and AN-FC synapses. Both types of AN synapses have similar numbers of AMPARs; however, the AN-BC have a higher density of AMPARs than AN-FC synapses, because the AN-BC synapses are smaller. A higher number and density of GluA3 subunits are observed at AN-BC synapses, whereas a higher number and density of GluA4 subunits are observed at AN-FC synapses. The intrasynaptic distribution of immunogold labeling revealed that AMPAR subunits, particularly GluA3, are concentrated at the center of the AN-BC synapses. The central distribution of AMPARs is absent in GluA3-knockout mice, and gold particles are evenly distributed along the postsynaptic density. GluA4 gold labeling was homogenously distributed along both synapse types. Thus, GluA3 and GluA4 subunits are distributed at AN synapses in a target-cell-dependent manner.

Intracerebroventricular administration of TNF-like weak inducer of apoptosis induces depression-like behavior and cognitive dysfunction in non-autoimmune mice

PubMed Central

Wen, Jing; Chen, Chris; Stock, Ariel; Doerner, Jessica; Gulinello, Maria; Putterman, Chaim

2016-01-01

Fn14, the sole known signaling receptor for the TNF family member TWEAK, is inducibly expressed in the central nervous system (CNS) in endothelial cells, astrocytes, microglia, and neurons. There is increasing recognition of the importance of the TWEAK/Fn14 pathway in autoimmune neurologic conditions, including experimental autoimmune encephalomyelitis and neuropsychiatric lupus. Previously, we had found that Fn14 knockout lupus-prone MRL/lpr mice display significantly attenuated neuropsychiatric manifestations. To investigate whether this improvement in disease is secondary to inhibition of TWEAK/Fn14 signaling within the CNS or the periphery, and determine whether TWEAK-mediated neuropsychiatric effects are strain dependent, we performed intracerebroventricular (ICV) injection of Fc-TWEAK or an isotype matched control protein to C57Bl6/J non-autoimmune mice. We found that Fc-TWEAK injected C57Bl6/J mice developed significant depression-like behavior and cognitive dysfunction. Inflammatory mediators associated with lupus brain disease, including CCL2, C3, and iNOS, were significantly elevated in the brains of Fc-TWEAK treated mice. Furthermore, Fc-TWEAK directly increased blood brain barrier (BBB) permeability, as demonstrated by increased IgG deposition in the brain and reduced aquaporin-4 expression. Finally, Fc-TWEAK increased apoptotic cell death in the cortex and hippocampus. In conclusion, TWEAK can contribute to lupus-associated neurobehavioral deficits including depression and cognitive dysfunction by acting within the CNS to enhance production of inflammatory mediators, promote disruption of the BBB, and induce apoptosis in resident brain cells. Our study provides further support that the TWEAK/Fn14 signaling pathway may be a potential therapeutic target for inflammatory diseases involving the CNS. PMID:26721417

Combination of RNA interference and virus receptor trap exerts additive antiviral activity in coxsackievirus B3-induced myocarditis in mice.

PubMed

Stein, Elisabeth A; Pinkert, Sandra; Becher, Peter Moritz; Geisler, Anja; Zeichhardt, Heinz; Klopfleisch, Robert; Poller, Wolfgang; Tschöpe, Carsten; Lassner, Dirk; Fechner, Henry; Kurreck, Jens

2015-02-15

Coxsackievirus B3 (CVB3) is a major heart pathogen against which no therapy exists to date. The potential of a combination treatment consisting of a proteinaceous virus receptor trap and an RNA interference-based component to prevent CVB3-induced myocarditis was investigated. A soluble variant of the extracellular domain of the coxsackievirus-adenovirus receptor (sCAR-Fc) was expressed from an adenoviral vector and 2 short hairpin RNAs (shRdRp2.4) directed against CVB3 were delivered by an adeno-associated virus (AAV) vector. Cell culture experiments revealed additive antiviral activity of the combined application. In a CVB3-induced mouse myocarditis model, both components applied individually significantly reduced inflammation and viral load in the heart. The combination exerted an additive antiviral effect and reduced heart pathology. Hemodynamic measurement revealed that infection with CVB3 resulted in impaired heart function, as illustrated by a drastically reduced cardiac output and impaired contractility and relaxation. Treatment with either sCAR-Fc or shRdRp2.4 significantly improved these parameters. Importantly, the combination of both components led to a further significant improvement of heart function. Combination of sCAR-Fc and shRdRp2.4 exerted additive effects and was significantly more effective than either of the single treatments in inhibiting CVB3-induced myocarditis and preventing cardiac dysfunction. © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Rapid desensitization of mice with anti-FcγRIIb/FcγRIII mAb safely prevents IgG-mediated anaphylaxis.

PubMed

Khodoun, Marat V; Kucuk, Zeynep Yesim; Strait, Richard T; Krishnamurthy, Durga; Janek, Kevin; Clay, Corey D; Morris, Suzanne C; Finkelman, Fred D

2013-12-01

Stimulatory IgG receptors (FcγRs) on bone marrow-derived cells contribute to the pathogenesis of several autoimmune and inflammatory disorders. Monoclonal antibodies that block FcγRs might suppress these diseases, but they can induce anaphylaxis. We wanted to determine whether a rapid desensitization approach can safely suppress IgG/FcγR-mediated anaphylaxis. Mice were injected with serially increasing doses of 2.4G2, a rat mAb that blocks the inhibitory FcγR, FcγRIIb, and the stimulatory receptor, FcγRIII. Rectal temperature was used to detect the development of anaphylaxis. Passive and active IgG-mediated anaphylaxis were evaluated in mice that had been rapidly desensitized with 2.4G2 or mock-desensitized in mice in which monocyte/macrophages, basophils, or neutrophils had been depleted or desensitized and in mice in which FcγRI, FcγRIII, and/or FcγRIV had been deleted or blocked. Rapid desensitization with 2.4G2 prevented 2.4G2-induced shock and completely suppressed IgG-mediated anaphylaxis. Rapid desensitization of ovalbumin-sensitized mice with 2.4G2 was safer and more effective than rapid desensitization with ovalbumin. 2.4G2 treatment completely blocked FcγRIII and removed most FcγRI and FcγRIV from nucleated peripheral blood cells. Because IgG(2a)-mediated anaphylaxis was partially FcγRI and FcγRIV dependent, the effects of 2.4G2 on FcγRI and FcγRIV were probably crucial for its complete inhibition of IgG(2a)-mediated anaphylaxis. IgG(2a)-mediated anaphylaxis was partially inhibited by depletion or desensitization of monocyte/macrophages, basophils, or neutrophils. IgG-mediated anaphylaxis can be induced by ligation of FcγRI, FcγRIII, or FcγRIV on monocycte/macrophages, basophils, or neutrophils and can be safely suppressed by rapid desensitization with anti-FcγRII/RIII mAb. A similar approach may safely suppress other FcγR-dependent immunopathology. Published by Mosby, Inc.

Investigating the Interaction between the Neonatal Fc Receptor and Monoclonal Antibody Variants by Hydrogen/Deuterium Exchange Mass Spectrometry*

PubMed Central

Jensen, Pernille Foged; Larraillet, Vincent; Schlothauer, Tilman; Kettenberger, Hubert; Hilger, Maximiliane; Rand, Kasper D.

2015-01-01

The recycling of immunoglobulins by the neonatal Fc receptor (FcRn) is of crucial importance in the maintenance of antibody levels in plasma and is responsible for the long half-lives of endogenous and recombinant monoclonal antibodies. From a therapeutic point of view there is great interest in understanding and modulating the IgG–FcRn interaction to optimize antibody pharmacokinetics and ultimately improve efficacy and safety. Here we studied the interaction between a full-length human IgG1 and human FcRn via hydrogen/deuterium exchange mass spectrometry and targeted electron transfer dissociation to map sites perturbed by binding on both partners of the IgG–FcRn complex. Several regions in the antibody Fc region and the FcRn were protected from exchange upon complex formation, in good agreement with previous crystallographic studies of FcRn in complex with the Fc fragment. Interestingly, we found that several regions in the IgG Fab region also showed reduced deuterium uptake. Our findings indicate the presence of hitherto unknown FcRn interaction sites in the Fab region or a possible conformational link between the IgG Fc and Fab regions upon FcRn binding. Further, we investigated the role of IgG glycosylation in the conformational response of the IgG–FcRn interaction. Removal of antibody glycans increased the flexibility of the FcRn binding site in the Fc region. Consequently, FcRn binding did not induce a similar conformational stabilization of deglycosylated IgG as observed for the wild-type glycosylated IgG. Our results provide new molecular insight into the IgG–FcRn interaction and illustrate the capability of hydrogen/deuterium exchange mass spectrometry to advance structural proteomics by providing detailed information on the conformation and dynamics of large protein complexes in solution. PMID:25378534

Fc-fusion proteins and FcRn: structural insights for longer-lasting and more effective therapeutics

PubMed Central

Rath, Timo; Baker, Kristi; Dumont, Jennifer A.; Peters, Robert T.; Jiang, Haiyan; Qiao, Shuo-Wang; Lencer, Wayne I.; Pierce, Glenn F.; Blumberg, Richard S.

2016-01-01

Nearly 350 IgG-based therapeutics are approved for clinical use or are under development for many diseases lacking adequate treatment options. These include molecularly engineered biologicals comprising the IgG Fc-domain fused to various effector molecules (so-called Fc-fusion proteins) that confer the advantages of IgG, including binding to the neonatal Fc receptor (FcRn) to facilitate in vivo stability, and the therapeutic benefit of the specific effector functions. Advances in IgG structure-function relationships and an understanding of FcRn biology have provided therapeutic opportunities for previously unapproachable diseases. This article discusses approved Fc-fusion therapeutics, novel Fc-fusion proteins and FcRn-dependent delivery approaches in development, and how engineering of the FcRn–Fc interaction can generate longer-lasting and more effective therapeutics. PMID:24156398

Scavenger receptor B1, the HDL receptor, is expressed abundantly in liver sinusoidal endothelial cells

PubMed Central

Ganesan, Latha P.; Mates, Jessica M.; Cheplowitz, Alana M.; Avila, Christina L.; Zimmerer, Jason M.; Yao, Zhili; Maiseyeu, Andrei; Rajaram, Murugesan V. S.; Robinson, John M.; Anderson, Clark L.

2016-01-01

Cholesterol from peripheral tissue, carried by HDL, is metabolized in the liver after uptake by the HDL receptor, SR-B1. Hepatocytes have long been considered the only liver cells expressing SR-B1; however, in this study we describe two disparate immunofluorescence (IF) experiments that suggest otherwise. Using high-resolution confocal microscopy employing ultrathin (120 nm) sections of mouse liver, improving z-axis resolution, we identified the liver sinusoidal endothelial cells (LSEC), marked by FcγRIIb, as the cell within the liver expressing abundant SR-B1. In contrast, the hepatocyte, identified with β-catenin, expressed considerably weaker levels, although optical resolution of SR-B1 was inadequate. Thus, we moved to a different IF strategy, first separating dissociated liver cells by gradient centrifugation into two portions, hepatocytes (parenchymal cells) and LSEC (non-parenchymal cells). Characterizing both portions for the cellular expression of SR-B1 by flow cytometry, we found that LSEC expressed considerable amounts of SR-B1 while in hepatocytes SR-B1 expression was barely perceptible. Assessing mRNA of SR-B1 by real time PCR we found messenger expression in LSEC to be about 5 times higher than in hepatocytes. PMID:26865459

An immunologically relevant rodent model demonstrates safety of therapy using a tumour-specific IgE.

PubMed

Josephs, Debra H; Nakamura, Mano; Bax, Heather J; Dodev, Tihomir S; Muirhead, Gareth; Saul, Louise; Karagiannis, Panagiotis; Ilieva, Kristina M; Crescioli, Silvia; Gazinska, Patrycja; Woodman, Natalie; Lomardelli, Cristina; Kareemaghay, Sedigeh; Selkirk, Christopher; Lentfer, Heike; Barton, Claire; Canevari, Silvana; Figini, Mariangela; Downes, Noel; Dombrowicz, David; Corrigan, Christopher J; Nestle, Frank O; Jones, Paul S; Gould, Hannah J; Blower, Philip J; Tsoka, Sophia; Spicer, James F; Karagiannis, Sophia N

2018-04-13

Designing biologically informative models for assessing the safety of novel agents, especially for cancer immunotherapy, carries substantial challenges. The choice of an in vivo system for studies on IgE antibodies represents a major impediment to their clinical translation, especially with respect to class-specific immunological functions and safety. Fcε receptor expression and structure are different in humans and mice, so that the murine system is not informative when studying human IgE biology. By contrast, FcεRI expression and cellular distribution in rats mirrors that of humans. We are developing MOv18 IgE, a human chimeric antibody recognizing the tumour-associated antigen folate receptor alpha. We created an immunologically congruent surrogate rat model likely to recapitulate human IgE-FcεR interactions, and engineered a surrogate rat IgE equivalent to MOv18. Employing this model, we examined in vivo safety and efficacy of anti-tumour IgE antibodies. In immunocompetent rats, rodent IgE restricted growth of syngeneic tumours in the absence of clinical, histopathological or metabolic signs associated with obvious toxicity. No physiological or immunological evidence of a 'cytokine-storm' or allergic response was seen, even at 50 mg/kg weekly doses. IgE treatment was associated with elevated serum concentrations of TNFα, a mediator previously linked with IgE-mediated anti-tumour and anti-parasitic functions, alongside evidence of substantially elevated tumoural immune cell infiltration and immunological pathway activation in tumour-bearing lungs. Our findings indicate safety of MOv18 IgE, in conjunction with efficacy and immune activation, supporting the translation of this therapeutic approach to the clinical arena. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Inhibition of bone morphogenetic protein signaling attenuates anemia associated with inflammation

PubMed Central

Steinbicker, Andrea U.; Sachidanandan, Chetana; Vonner, Ashley J.; Yusuf, Rushdia Z.; Deng, Donna Y.; Lai, Carol S.; Rauwerdink, Kristen M.; Winn, Julia C.; Saez, Borja; Cook, Colleen M.; Szekely, Brian A.; Roy, Cindy N.; Seehra, Jasbir S.; Cuny, Gregory D.; Scadden, David T.; Peterson, Randall T.; Bloch, Kenneth D.

2011-01-01

Anemia of inflammation develops in settings of chronic inflammatory, infectious, or neoplastic disease. In this highly prevalent form of anemia, inflammatory cytokines, including IL-6, stimulate hepatic expression of hepcidin, which negatively regulates iron bioavailability by inactivating ferroportin. Hepcidin is transcriptionally regulated by IL-6 and bone morphogenetic protein (BMP) signaling. We hypothesized that inhibiting BMP signaling can reduce hepcidin expression and ameliorate hypoferremia and anemia associated with inflammation. In human hepatoma cells, IL-6–induced hepcidin expression, an effect that was inhibited by treatment with a BMP type I receptor inhibitor, LDN-193189, or BMP ligand antagonists noggin and ALK3-Fc. In zebrafish, the induction of hepcidin expression by transgenic expression of IL-6 was also reduced by LDN-193189. In mice, treatment with IL-6 or turpentine increased hepcidin expression and reduced serum iron, effects that were inhibited by LDN-193189 or ALK3-Fc. Chronic turpentine treatment led to microcytic anemia, which was prevented by concurrent administration of LDN-193189 or attenuated when LDN-193189 was administered after anemia was established. Our studies support the concept that BMP and IL-6 act together to regulate iron homeostasis and suggest that inhibition of BMP signaling may be an effective strategy for the treatment of anemia of inflammation. PMID:21393479

Vitamin A-coupled liposome system targeting free cholesterol accumulation in hepatic stellate cells offers a beneficial therapeutic strategy for liver fibrosis.

PubMed

Furuhashi, Hirotaka; Tomita, Kengo; Teratani, Toshiaki; Shimizu, Motonori; Nishikawa, Makoto; Higashiyama, Masaaki; Takajo, Takeshi; Shirakabe, Kazuhiko; Maruta, Koji; Okada, Yoshikiyo; Kurihara, Chie; Watanabe, Chikako; Komoto, Shunsuke; Aosasa, Suefumi; Nagao, Shigeaki; Yamamoto, Junji; Miura, Soichiro; Hokari, Ryota

2018-04-01

Liver fibrosis is a life-threatening disorder for which no approved therapy is available. Recently, we reported that mouse hepatic stellate cell (HSC) activation increased free cholesterol (FC) accumulation, partly by enhancing signaling through sterol regulatory element-binding protein 2 (SREBP2) and microRNA-33a (miR-33a), which resulted in HSC sensitization to transforming growth factor-β (TGFβ)-induced activation in a "vicious cycle" of liver fibrosis. Human HSCs were isolated from surgical liver specimens from control patients and patients with liver fibrosis. C57BL/6 mice were treated with carbon tetrachloride for 4 weeks and concurrently given SREBP2-siRNA- or anti-miR-33a-bearing vitamin A-coupled liposomes. In human activated HSCs obtained from patients with liver fibrosis, FC accumulation was enhanced independently of serum cholesterol levels through increased signaling by both SREBP2 and miR-33a. This increased FC accumulation enhanced Toll-like receptor 4 (TLR4) protein levels and lowered the TGFβ-pseudoreceptor Bambi (bone morphogenetic protein and activin membrane-bound inhibitor) mRNA levels in HSCs. Notably, in a mouse liver fibrosis model, reduction of FC accumulation, specifically in activated HSCs by suppression of SREBP2 or miR-33a expression using SREBP2-siRNA- or anti-miR-33a-bearing vitamin A-coupled liposomes, downregulated TLR4 signaling, increased Bambi expression, and consequently ameliorated liver fibrosis. Our results suggest that FC accumulation in HSCs, as an intracellular mediator promoting HSC activation, contributes to a vicious cycle of HSC activation in human and mouse liver fibrosis independent of serum cholesterol levels. Targeting FC accumulation-related molecules in HSCs through a vitamin A-coupled liposomal system represents a favorable therapeutic strategy for liver fibrosis. © 2017 The Japan Society of Hepatology.

Opsonization of Toxoplasma gondii tachyzoites with nonspecific immunoglobulins promotes their phagocytosis by macrophages and inhibits their proliferation in nonphagocytic cells in tissue culture.

PubMed

Vercammen, M; Scorza, T; El Bouhdidi, A; Van Beeck, K; Carlier, Y; Dubremetz, J F; Verschueren, H

1999-11-01

We have recently shown that Toxoplasma gondii tachyzoites grown in in vitro culture can bind unspecific immunoglobulin (Ig) through their Fc moiety. We show now that Fc receptors are also present on T. gondii within the host animal, and that intraperitoneal parasites in immunocompetent mice are saturated with unspecific Ig. We have also investigated the effect of the parasite's Fc receptor on the interaction of tachyzoites with mammalian cells, using the Vero cell line as a model for nonphagocytic host cells and murine peritoneal macrophages in primary culture as a model for phagocytic cells. Coating of tachyzoites with parasite-unrelated Ig did not enhance their invasive capacity in either target cell type, but slightly decreased the parasite proliferation. Moreover, phagocytosis by macrophages was increased by approximately 50% when parasites were coated with unspecific Ig. These results indicate that the Fc receptor on T. gondii affects the balance between invasion and phagocytosis in a way that is detrimental to the parasites.

Impact of SPR biosensor assay configuration on antibody: Neonatal Fc receptor binding data

PubMed Central

Wang, Xiangdan; McKay, Patrick; Dutina, George; Hass, Philip E.; Nijem, Ihsan; Allison, David; Cowan, Kyra J.; Lin, Kevin; Quarmby, Valerie; Yang, Jihong

2017-01-01

ABSTRACT Binding interactions with the neonatal Fc receptor (FcRn) are one determinant of pharmacokinetic properties of recombinant human monoclonal antibody (rhumAb) therapeutics, and a conserved binding motif in the crystallizable fragment (Fc) region of IgG molecules interacts with FcRn. Surface plasmon resonance (SPR) biosensor assays are often used to characterize interactions between FcRn and rhumAb therapeutics. In such assays, generally either the rhumAb (format 1) or the FcRn protein (format 2) is immobilized on a biosensor chip. However, because evidence suggests that, in some cases, the variable domains of a rhumAb may also affect FcRn binding, we evaluated the effect of SPR assay configuration on binding data. We sought to assess FcRn binding properties of 2 rhumAbs (rhumAb1 and rhumAb2) to FcRn proteins using these 2 biosensor assay formats. The two rhumAbs have greater than 99% sequence identity in the Fc domain but differ in their Fab regions. rhumAb2 contains a positively charged patch in the variable domain that is absent in rhumAb1. Our results showed that binding of rhumAb1 to FcRn was independent of biosensor assay configuration, while binding of rhumAb2 to FcRn was highly SPR assay configuration dependent. Further investigations revealed that the format dependency of rhumAb2-FcRn binding is linked to the basic residues that form a positively charged patch in the variable domain of rhumAb2. Our work highlights the importance of analyzing rhumAb-FcRn binding interactions using 2 alternate SPR biosensor assay configurations. This approach may also provide a simple way to identify the potential for non-Fc-driven FcRn binding interactions in otherwise typical IgGs. PMID:28001487

Decoy receptor 3: an endogenous immunomodulator in cancer growth and inflammatory reactions.

PubMed

Hsieh, Shie-Liang; Lin, Wan-Wan

2017-06-19

Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor (TNFR) superfamily member 6b (TNFRSF6B), is a soluble decoy receptor which can neutralize the biological functions of three members of tumor necrosis factor superfamily (TNFSF): Fas ligand (FasL), LIGHT, and TL1A. In addition to 'decoy' function, recombinant DcR3.Fc is able to modulate the activation and differentiation of dendritic cells (DCs) and macrophages via 'non-decoy' action. DcR3-treated DCs skew T cell differentiation into Th2 phenotype, while DcR3-treated macrophages behave M2 phenotype. DcR3 is upregulated in various cancer cells and several inflammatory tissues, and is regarded as a potential biomarker to predict inflammatory disease progression and cancer metastasis. However, whether DcR3 is a pathogenic factor or a suppressor to attenuate inflammatory reactions, has not been discussed comprehensively yet. Because mouse genome does not have DcR3, it is not feasible to investigate its physiological functions by gene-knockout approach. However, DcR3-mediated effects in vitro are determined via overexpressing DcR3 or addition of recombinant DcR3.Fc fusion protein. Moreover, CD68-driven DcR3 transgenic mice are used to investigate DcR3-mediated systemic effects in vivo. Upregulation of DcR3 during inflammatory reactions exerts negative-feedback to suppress inflammation, while tumor cells hijack DcR3 to prevent apoptosis and promote tumor growth and invasion. Thus, 'switch-on' of DcR3 expression may be feasible for the treatment of inflammatory diseases and enhance tissue repairing, while 'switch-off' of DcR3 expression can enhance tumor apoptosis and suppress tumor growth in vivo.

FcγRIIIa Expression on Monocytes in Rheumatoid Arthritis: Role in Immune-Complex Stimulated TNF Production and Non-Response to Methotrexate Therapy

PubMed Central

Cooper, Dawn L.; Martin, Stephen G.; Robinson, James I.; Mackie, Sarah L.; Charles, Christopher J.; Nam, Jackie; Consortium, YEAR; Isaacs, John D.; Emery, Paul; Morgan, Ann W.

2012-01-01

Objective The expression of FcγRIIIa/CD16 may render monocytes targets for activation by IgG-containing immune complexes (IC). We investigated whether FcγRIIIa/CD16 was upregulated in rheumatoid arthritis (RA), associated with TNF production in response to IC-stimulation, and if this predicted response to methotrexate therapy. Methods FcγRIIIa/CD16 expression on CD14low and CD14++ monocytes was measured by flow cytometry in healthy controls and RA patients (early and long-standing disease). Intracellular TNF-staining was carried out after in vitro LPS or heat-aggregated immunoglobulin (HAG) activation. FcγRIIIa/CD16 expression pre- and post-steroid/methotrexate treatment was examined. Results Increased FcγRIIIa/CD16 expression on CD14++ monocytes in long-standing RA patients compared to controls was demonstrated (p = 0.002) with intermediate levels in early-RA patients. HAG-induced TNF-production in RA patients was correlated with the percentage of CD14++ monocytes expressing FcγRIIIa/CD16 (p<0.001). The percentage of CD14++ monocytes expressing FcγRIIIa/CD16 at baseline in early DMARD-naïve RA patients was negatively correlated with DAS28-ESR improvement 14-weeks post-methotrexate therapy (p = 0.003) and was significantly increased in EULAR non-responders compared to moderate (p = 0.01) or good responders (p = 0.003). FcγRIIIa/CD16 expression was not correlated with age, presence of systemic inflammation or autoantibody titers. Conclusion Increased FcγRIIIa/CD16 expression on CD14++ monocytes in RA may result in a cell that has increased responsiveness to IC-stimulation. This monocyte subset may contribute to non-response to methotrexate therapy. PMID:22235253

Autoantibody-induced internalization of CNS AQP4 water channel and EAAT2 glutamate transporter requires astrocytic Fc receptor

PubMed Central

Hinson, Shannon R.; Clift, Ian C.; Luo, Ningling; Kryzer, Thomas J.; Lennon, Vanda A.

2017-01-01

Aquaporin-4 (AQP4) water channel-specific IgG distinguishes neuromyelitis optica (NMO) from multiple sclerosis and causes characteristic immunopathology in which central nervous system (CNS) demyelination is secondary. Early events initiating the pathophysiological outcomes of IgG binding to astrocytic AQP4 are poorly understood. CNS lesions reflect events documented in vitro following IgG interaction with AQP4: AQP4 internalization, attenuated glutamate uptake, intramyelinic edema, interleukin-6 release, complement activation, inflammatory cell recruitment, and demyelination. Here, we demonstrate that AQP4 internalization requires AQP4-bound IgG to engage an astrocytic Fcγ receptor (FcγR). IgG-lacking Fc redistributes AQP4 within the plasma membrane and induces interleukin-6 release. However, AQP4 endocytosis requires an activating FcγR’s gamma subunit and involves astrocytic membrane loss of an inhibitory FcγR, CD32B. Interaction of the IgG–AQP4 complex with FcγRs triggers coendocytosis of the excitatory amino acid transporter 2 (EAAT2). Requirement of FcγR engagement for internalization of two astrocytic membrane proteins critical to CNS homeostasis identifies a complement-independent, upstream target for potential early therapeutic intervention in NMO. PMID:28461494

Effects of Opsonization and Gamma Interferon on Growth of Brucella Melitensis 16M in Mouse Peritoneal Macrophages In Vitro

DTIC Science & Technology

2000-01-01

bacterial CFU (Fig. 3). Macrophages cultured without brucel - lae or cultured with brucellae but without IFN-7 made ɘ.3 nmol of nitrite/200 JJLI well...receptors used for the uptake of nonopsonized brucel - lae are unknown. Synergy between the receptor for the Fc domain of immunoglobulin G (FcR) and

Label-free Fab and Fc affinity/avidity profiling of the antibody complex half-life for polyclonal and monoclonal efficacy screening.

PubMed

Read, Thomas; Olkhov, Rouslan V; Williamson, E Diane; Shaw, Andrew M

2015-09-01

A unified approach to affinity screening for Fab and Fc interactions of an antibody for its antigen and FcγR receptor has been developed. An antigen array is used for the Fab affinity and cross-reactivity screening and protein A/G proxy is the FcγR receptor. The affinities are derived using a simple 1:1 binding model with a consistent error analysis. The association and dissociation kinetics are measured over optimised times for accurate determination. The Fab/Fc affinities are derived for ten antibodies: mAb-actin (mouse), pAb-BSA (sheep), pAb-collagen V (rabbit), pAb-CRP (goat), mAb-F1 (mouse), mAbs (mouse) 7.3, 12.3, 29.3, 36.3 and 46.3 raised against LcrV in Yersinia pestis. The rate of the dissociation of antigen-antibody complexes relates directly to their immunological function as does the Fc-FcγR complex and a new half-life plot has been defined with a Fab/Fc half-life range of 17-470 min. The upper half-life value points to surface avidity. Two antibodies that are protective as an immunotherapy define a Fab half-life >250 min and an Fc half-life >50 min as characteristics of ideal interactions which can form the basis of an antibody screen for immunotherapy.

Establishment and characterization of mouse bone marrow-derived mast cell hybridomas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawahara, Takeshi, E-mail: tkawafb@shinshu-u.ac.jp

2012-11-01

Interleukin (IL)-3-dependent mouse bone marrow-derived mast cells (BMMCs) are an important model for studying the function of mucosal-type mast cells. In the present study, BMMCs were successfully immortalized by cell fusion using a hypoxanthine-aminopterin-thymidine medium-sensitive variant of P815 mouse mastocytoma (P815-6TgR) as a partner cell line. The established mouse mast cell hybridomas (MMCHs) expressed {alpha}, {beta}, and {gamma} subunits of high-affinity immunoglobulin E (IgE) receptor (Fc{epsilon}RI) and possessed cytoplasmic granules devoid of or partially filled with electron-dense material. Four independent MMCH clones continuously proliferated without supplemental exogenous IL-3 and showed a degranulation response on stimulation with IgE+antigen. Furthermore, histamine synthesismore » and release by degranulation were confirmed in MMCH-D5, a MMCH clone that showed the strongest degranulation response. MMCH-D5 exhibited elevated levels of IL-3, IL-4, IL-13, granulocyte-macrophage colony-stimulating factor, tumor necrosis factor (TNF)-{alpha}, and cyclooxygenase 2, and production of prostaglandin D{sub 2} and leukotriene C{sub 4} in response to IgE-induced stimulation. MMCH clones also expressed Toll-like receptors (TLRs) 1, 2, 4, and 6 and showed elevated levels of TNF-{alpha} expression in response to stimulation with TLR2 and TLR4 ligands. The MMCHs established using this method should be suitable for studies on Fc{epsilon}RI- and TLR-mediated effector functions of mast cells.« less

Osteoprotegerin and β2-Agonists Mitigate Muscular Dystrophy in Slow- and Fast-Twitch Skeletal Muscles.

PubMed

Dufresne, Sébastien S; Boulanger-Piette, Antoine; Frenette, Jérôme

2017-03-01

Our recent work showed that daily injections of osteoprotegerin (OPG)-immunoglobulin fragment complex (OPG-Fc) completely restore the function of fast-twitch extensor digitorum longus muscles in dystrophic mdx mice, a murine model of Duchenne muscular dystrophy. However, despite marked improvements, OPG-Fc was not as effective in preventing the loss of function of slow-twitch soleus and diaphragm muscles. Because β 2 -agonists enhance the function of slow- and fast-twitch dystrophic muscles and because their use is limited by their adverse effects on bone and cardiac tissues, we hypothesized that OPG-Fc, a bone and skeletal muscle protector, acts synergistically with β 2 -agonists and potentiates their positive effects on skeletal muscles. We observed that the content of β 2 -adrenergic receptors, which are mainly expressed in skeletal muscle, is significantly reduced in dystrophic muscles but is rescued by the injection of OPG-Fc. Most important, OPG-Fc combined with a low dose of formoterol, a member of a new generation of β 2 -agonists, histologically and functionally rescued slow-twitch dystrophic muscles. This combination of therapeutic agents, which have already been tested and approved for human use, may open up new therapeutic avenues for Duchenne muscular dystrophy and possibly other neuromuscular diseases. Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Monomeric C-reactive protein and Notch-3 co-operatively increase angiogenesis through PI3K signalling pathway.

PubMed

Boras, Emhamed; Slevin, Mark; Alexander, M Yvonne; Aljohi, Ali; Gilmore, William; Ashworth, Jason; Krupinski, Jerzy; Potempa, Lawrence A; Al Abdulkareem, Ibrahim; Elobeid, Adila; Matou-Nasri, Sabine

2014-10-01

C-reactive protein (CRP) is the most acute-phase reactant serum protein of inflammation and a strong predictor of cardiovascular disease. Its expression is associated with atherosclerotic plaque instability and the formation of immature micro-vessels. We have previously shown that CRP upregulates endothelial-derived Notch-3, a key receptor involved in vascular development, remodelling and maturation. In this study, we investigated the links between the bioactive monomeric CRP (mCRP) and Notch-3 signalling in angiogenesis. We used in vitro (cell counting, wound-healing and tubulogenesis assays) and in vivo (chorioallantoic membrane) angiogenic assays and Western blotting to study the angiogenic signalling pathways induced by mCRP and Notch-3 activator chimera protein (Notch-3/Fc). Our results showed an additive effect on angiogenesis of mCRP stimulatory effect combined with Notch-3/Fc promoting bovine aortic endothelial cell (BAEC) proliferation, migration, tube formation in Matrigel(TM) with up-regulation of phospho-Akt expression. The pharmacological blockade of PI3K/Akt survival pathway by LY294002 fully inhibited in vitro and in vivo angiogenesis induced by mCRP/Notch-3/Fc combination while blocking Notch signalling by gamma-secretase inhibitor (DAPT) partially inhibited mCRP/Notch-3/Fc-induced angiogenesis. Using a BAEC vascular smooth muscle cell co-culture sprouting angiogenesis assay and transmission electron microscopy, we showed that activation of both mCRP and Notch-3 signalling induced the formation of thicker sprouts which were shown later by Western blotting to be associated with an up-regulation of N-cadherin expression and a down-regulation of VE-cadherin expression. Thus, mCRP combined with Notch-3 activator promote angiogenesis through the PI3K/Akt pathway and their therapeutic combination has potential to promote and stabilize vessel formation whilst reducing the risk of haemorrhage from unstable plaques. Copyright © 2014 Elsevier Ltd. All rights reserved.

Generation of CMAHKO/GTKO/shTNFRI-Fc/HO-1 quadruple gene modified pigs.

PubMed

Kim, Geon A; Lee, Eun Mi; Jin, Jun-Xue; Lee, Sanghoon; Taweechaipaisankul, Anukul; Hwang, Jong Ik; Alam, Zahid; Ahn, Curie; Lee, Byeong Chun

2017-08-01

As an alternative source of organs for transplantation into humans, attention has been directed to pigs due to their similarities in biological features and organ size. However, severe immune rejection has prevented successful xenotransplantation using pig organs and tissues. To overcome immune rejection, recently developed genetic engineering systems such as TALEN coupled with somatic cell nuclear transfer (SCNT) to make embryos could be used to produce pigs compatible with xenotransplantation. We used the TALEN system to target the non-Gal antigen cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH) gene in pigs that is naturally deleted in humans. Gal-deleted cells expressing both soluble human tumor necrosis factor receptor I IgG 1 -Fc (shTNFRI-Fc) and human hemagglutinin -tagged-human heme oxygenase-1 (hHO-1) were transfected with a TALEN target for CMAH. Cells lacking CMAH were negatively selected using N-glyconeuraminic acid (Neu5Gc)/magnetic beads and the level of Neu5Gc expression of isolated cells were analyzed by FACS and DNA sequencing. Cloned embryos using 3 different genetically modified cell clones were respectively transferred into 3 recipients, with 55.6% (5/9) becoming pregnant and three cloned pigs were produced. Successful genetic disruption of the CMAH gene was confirmed by sequencing, showing lack of expression of CMAH in tail-derived fibroblasts of the cloned piglets. Besides decreased expression of Neu5Gc in piglets produced by SCNT, antibody-mediated complement-dependent cytotoxicity assays and natural antibody binding for examining immuno-reactivity of the quadruple gene modified pigs derived from endothelial cells and fibroblasts were reduced significantly compared to those of wild type animals. We conclude that by combining the TALEN system and transgenic cells, targeting of multiple genes could be useful for generating organs for xenotransplantation. We produced miniature pigs with quadruple modified genes CMAHKO/GTKO/shTNFRI-Fc/hHO-1 that will be suitable for xenotransplantation by overcoming hyperacute, acute and anti-inflammatory rejection.

GluA2 trafficking is involved in apoptosis of retinal ganglion cells induced by activation of EphB/EphrinB reverse signaling in a rat chronic ocular hypertension model.

PubMed

Dong, Ling-Dan; Gao, Feng; Wang, Xiao-Han; Miao, Yanying; Wang, Shu-Yue; Wu, Yi; Li, Fang; Wu, Jihong; Cheng, Xiang-Lin; Sun, Xing-Huai; Yang, Xiong-Li; Wang, Zhongfeng

2015-04-01

EphB1, expressed in Müller cells, and ephrinB2, expressed in both Müller cells and retinal ganglion cells (RGCs), constitute an EphB/ephrinB reverse signaling in RGCs. Whether and how this reverse signaling is involved in RGC apoptosis in a rat chronic ocular hypertension (COH) model was investigated. In the COH model, both EphB1 and ephrinB2 were significantly increased and the reverse signaling was activated, which was accompanied by increased protein levels of phosphorylated (p) src, GluA2, and p-GluA2. Intravitreal injection of EphB2-Fc, an activator of ephrinB2, induced an increase in TUNEL-positive signals in normal retinae. A coimmunoprecipitation assay demonstrated direct interactions among ephrinB2, p-src, and GluA2. Moreover, in COH rats the expression of GluA2 proteins on the surface of retinal cells was decreased. Such GluA2 endocytosis could be prevented by preoperational intravitreal injection of 4-amino-3-(4-chlorophenyl)-1-(t-butyl)-1H-pyrazolo [3,4-d] pyrimidine (PP2), an inhibitor of src family tyrosine kinases, and possibly involved the protein interacting with C kinase 1 and phosphorylation of GluA2. In normal rats, intravitreal injection of EphB2-Fc caused changes in these protein levels similar to those observed in COH rats, which all could be avoided by preinjection of PP2. Patch-clamp experiments further showed that the current-voltage relationship of AMPA receptor-mediated EPSCs of RGCs exhibited stronger inward rectification in EphB2-Fc-injected rats. Furthermore, preinjection of PP2 or N-[3-[[4-[(3-aminopropyl)amino]butyl]amino]propyl]-1-naphthaleneacetamide trihydrochloride) (Naspm), a Ca(2+)-permeable GluA2-lacking AMPA receptor inhibitor, remarkably inhibited RGC apoptosis in either EphB2-Fc-injected or COH rats. Together, elevated GluA2 trafficking induced by activated EphB2/ephrinB2 reverse signaling likely contributes to RGC apoptosis in COH rats. Copyright © 2015 the authors 0270-6474/15/355409-13$15.00/0.

Insight into small molecule binding to the neonatal Fc receptor by X-ray crystallography and 100 kHz magic-angle-spinning NMR

PubMed Central

Macpherson, Alex; Smith-Penzel, Susanne; Basse, Nicolas; Lecomte, Fabien; Deboves, Hervé; Taylor, Richard D.; Norman, Tim; Porter, John; Waters, Lorna C.; Westwood, Marta; Cossins, Ben; Cain, Katharine; White, James; Griffin, Robert; Prosser, Christine; Kelm, Sebastian; Sullivan, Amy H.; Fox, David; Carr, Mark D.; Henry, Alistair; Taylor, Richard; Meier, Beat H.; Oschkinat, Hartmut; Lawson, Alastair D.

2018-01-01

Aiming at the design of an allosteric modulator of the neonatal Fc receptor (FcRn)–Immunoglobulin G (IgG) interaction, we developed a new methodology including NMR fragment screening, X-ray crystallography, and magic-angle-spinning (MAS) NMR at 100 kHz after sedimentation, exploiting very fast spinning of the nondeuterated soluble 42 kDa receptor construct to obtain resolved proton-detected 2D and 3D NMR spectra. FcRn plays a crucial role in regulation of IgG and serum albumin catabolism. It is a clinically validated drug target for the treatment of autoimmune diseases caused by pathogenic antibodies via the inhibition of its interaction with IgG. We herein present the discovery of a small molecule that binds into a conserved cavity of the heterodimeric, extracellular domain composed of an α-chain and β2-microglobulin (β2m) (FcRnECD, 373 residues). X-ray crystallography was used alongside NMR at 100 kHz MAS with sedimented soluble protein to explore possibilities for refining the compound as an allosteric modulator. Proton-detected MAS NMR experiments on fully protonated [13C,15N]-labeled FcRnECD yielded ligand-induced chemical-shift perturbations (CSPs) for residues in the binding pocket and allosteric changes close to the interface of the two receptor heterodimers present in the asymmetric unit as well as potentially in the albumin interaction site. X-ray structures with and without ligand suggest the need for an optimized ligand to displace the α-chain with respect to β2m, both of which participate in the FcRnECD–IgG interaction site. Our investigation establishes a method to characterize structurally small molecule binding to nondeuterated large proteins by NMR, even in their glycosylated form, which may prove highly valuable for structure-based drug discovery campaigns. PMID:29782488

Insight into small molecule binding to the neonatal Fc receptor by X-ray crystallography and 100 kHz magic-angle-spinning NMR.

PubMed

Stöppler, Daniel; Macpherson, Alex; Smith-Penzel, Susanne; Basse, Nicolas; Lecomte, Fabien; Deboves, Hervé; Taylor, Richard D; Norman, Tim; Porter, John; Waters, Lorna C; Westwood, Marta; Cossins, Ben; Cain, Katharine; White, James; Griffin, Robert; Prosser, Christine; Kelm, Sebastian; Sullivan, Amy H; Fox, David; Carr, Mark D; Henry, Alistair; Taylor, Richard; Meier, Beat H; Oschkinat, Hartmut; Lawson, Alastair D

2018-05-01

Aiming at the design of an allosteric modulator of the neonatal Fc receptor (FcRn)-Immunoglobulin G (IgG) interaction, we developed a new methodology including NMR fragment screening, X-ray crystallography, and magic-angle-spinning (MAS) NMR at 100 kHz after sedimentation, exploiting very fast spinning of the nondeuterated soluble 42 kDa receptor construct to obtain resolved proton-detected 2D and 3D NMR spectra. FcRn plays a crucial role in regulation of IgG and serum albumin catabolism. It is a clinically validated drug target for the treatment of autoimmune diseases caused by pathogenic antibodies via the inhibition of its interaction with IgG. We herein present the discovery of a small molecule that binds into a conserved cavity of the heterodimeric, extracellular domain composed of an α-chain and β2-microglobulin (β2m) (FcRnECD, 373 residues). X-ray crystallography was used alongside NMR at 100 kHz MAS with sedimented soluble protein to explore possibilities for refining the compound as an allosteric modulator. Proton-detected MAS NMR experiments on fully protonated [13C,15N]-labeled FcRnECD yielded ligand-induced chemical-shift perturbations (CSPs) for residues in the binding pocket and allosteric changes close to the interface of the two receptor heterodimers present in the asymmetric unit as well as potentially in the albumin interaction site. X-ray structures with and without ligand suggest the need for an optimized ligand to displace the α-chain with respect to β2m, both of which participate in the FcRnECD-IgG interaction site. Our investigation establishes a method to characterize structurally small molecule binding to nondeuterated large proteins by NMR, even in their glycosylated form, which may prove highly valuable for structure-based drug discovery campaigns.

Activation of Basophils Is a New and Sensitive Marker of Biocompatibility in Hemodialysis

PubMed Central

Aljadi, Zenib; Mansouri, Ladan; Nopp, Anna; Paulsson, Josefin M; Winqvist, Ola; Russom, Aman; Ståhl, Mårten; Hylander, Britta; Jacobson, Stefan H; Lundahl, Joachim

2014-01-01

The hemodialysis procedure involves contact between peripheral blood and the surface of dialyzer membranes, which may lead to alterations in the pathways of innate and adaptive immunity. We aimed to study the effect of blood–membrane interaction on human peripheral basophils and neutrophils in hemodialysis with high- and low-permeability polysulfone dialyzers. The surface expression of CD203c (basophil selection marker) and CD63 (activation marker) after activation by the bacterial peptide formyl-methionyl-leucyl-phenylalanine (fMLP) or anti-Fcε receptor I (FcεRI) antibody and the absolute number of basophils was investigated before and after hemodialysis with each of the dialyzers. Moreover, the expression on neutrophils of CD11b, the CD11b active epitope, and CD88 was analyzed in the same groups of individuals. The expression of CD63 in basophils following activation by fMLP was significantly higher in the patient group compared with that in healthy controls, but no differences were observed after activation by anti-FcεRI. During the hemodialysis procedure, the low-flux membrane induced up-regulation of CD63 expression on basophils, while passage through the high-flux membrane did not significantly alter the responsiveness. In addition, the absolute number of basophils was unchanged after hemodialysis with either of the dialyzers and compared with healthy controls. We found no significant differences in the expression of the neutrophil activation markers (CD11b, the active epitope of CD11b, and CD88) comparing the two different dialyzers before and after dialysis and healthy controls. Together, these findings suggest that alterations in basophil activity may be a useful marker of membrane bioincompatibility in hemodialysis. PMID:24712758

Antibody Functional Assays as Measures of Fc Receptor-Mediated Immunity to HIV - New Technologies and their Impact on the HIV Vaccine Field

PubMed Central

Wines, Bruce D.; Billings, Hugh; Mclean, Milla R.; Kent, Stephen J.; Hogarth, P. Mark

2017-01-01

Background: There is now intense interest in the role of HIV-specific antibodies and the engagement of FcγR functions in the control and prevention of HIV infection. The analyses of the RV144 vaccine trial, natural progression cohorts, and macaque models all point to a role for Fc-dependent effector functions, such as cytotoxicity (ADCC) or phagocytosis (ADCP), in the control of HIV. However, reliable assays that can be reproducibly used across different laboratories to measure Fc-dependent functions, such as antibody dependent cellular cytotoxicity (ADCC) are limited. Method: This brief review highlights the importance of Fc properties for immunity to HIV, particular-ly via FcγR diversity and function. We discuss assays used to study FcR mediated functions of HIV-specific Ab, including our recently developed novel cell-free ELISA using homo-dimeric FcγR ecto-domains to detect functionally relevant viral antigen-specific antibodies. Results: The binding of these dimeric FcγR ectodomains, to closely spaced pairs of IgG Fc, mimics the engagement and cross-linking of Fc receptors by IgG opsonized virions or infected cells as the es-sential prerequisite to the induction of Ab-dependent effector functions. The dimeric FcγR ELISA reli-ably correlates with ADCC in patient responses to influenza. The assay is amenable to high throughput and could be standardized across laboratories. Conclusion: We propose the assay has broader implications for the evaluation of the quality of anti-body responses in viral infections and for the rapid evaluation of responses in vaccine development campaigns for HIV and other viral infections. PMID:28322167

Distribution of Endo180 receptor and ligand in developing articular cartilage.

PubMed

Howard, M J; Chambers, M G; Mason, R M; Isacke, C M

2004-01-01

To investigate the expression of a novel member of the mannose receptor family, Endo180 (also known as uPARAP), and the distribution of Endo180 ligand(s) in the articular cartilage and growth plate of normal CBA mice and STR/ort mice, a well characterized model of spontaneous osteoarthritis. A polyclonal anti-Endo180 antibody was used to determine receptor expression. The Endo180 extracellular domain fused to a human immunoglobulin Fc tail was used to detect ligand. Endo180 receptor was strongly expressed in chondrocytes both in vitro and throughout the articular cartilage of young CBA and STR/ort mice. Expression decreased in older animals. In STR/ort mice with osteoarthritic lesions, no upregulation of Endo180 was detected. In the developing growth plate, Endo180 was expressed strongly by the proliferating chondrocytes. In contrast, Endo180 ligand was detected most strongly in hypertrophic zone of the growth plate and only at low levels in articular cartilage. In cultured chondrocytes, Endo180 was localized on the cell surface and in intracellular vesicles. Constitutively recycling endocytic receptors function to internalize ligand from the extracellular milieu and the ability of Endo180 to bind both glycosylated ligands and collagens suggests a role in extracellular matrix remodeling. Expression of Endo180 in articular cartilage chondrocytes of young, but not old, mice and the reciprocal expression of Endo180 and its ligands in the growth plate suggest that this receptor is involved in cartilage development but not in cartilage homeostasis. In addition, our data indicates that Endo180 does not appear to play a role in the development or progression of murine osteoarthritis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Meichun; Department of Physiology, Hubei University of Medicine, Shiyan; Li, Jianjie

Mast cells play a key role in the pathogenesis of asthma and are a promising target for therapeutic intervention in asthma. This study investigated the effects of polydatin (PD), a resveratrol glucoside, on mast cell degranulation upon cross-linking of the high-affinity IgE receptors (FcεRI), as well as the anti-allergic activity of PD in vivo. Herein, we demonstrated that PD treatment for 30 min suppressed FcεRI-mediated mast cell degranulation in a dose-dependent manner. Concomitantly, PD significantly decreased FcεRI-mediated Ca{sup 2+} increase in mast cells. The suppressive effects of PD on FcεRI-mediated Ca{sup 2+} increase were largely inhibited by using LaCl{sub 3}more » to block the Ca{sup 2+} release-activated Ca{sup 2+} channels (CRACs). Furthermore, PD significantly inhibited Ca{sup 2+} entry through CRACs evoked by thapsigargin (TG). Knocking down protein expression of Orai1, the pore-forming subunit of CRACs, significantly decreased PD suppression of FcεRI-induced intracellular Ca{sup 2+} influx and mast cell degranulation. In a mouse model of mast cell-dependent passive cutaneous anaphylaxis (PCA), in vivo PD administration suppressed mast cell degranulation and inhibited anaphylaxis. Taken together, our data indicate that PD stabilizes mast cells by suppressing FcεRI-induced Ca{sup 2+} mobilization mainly through inhibiting Ca{sup 2+} entry via CRACs, thus exerting a protective effect against PCA. -- Highlights: ► Polydatin can prevent the pathogenesis of passive cutaneous anaphylaxis in mice. ► Polydatin stabilizes mast cells by decreasing FcεRI-mediated degranulation. ► Polydatin suppresses Ca{sup 2+} entry through CRAC channels in mast cells.« less

Neutrophil cell surface receptors and their intracellular signal transduction pathways☆

PubMed Central

Futosi, Krisztina; Fodor, Szabina; Mócsai, Attila

2013-01-01

Neutrophils play a critical role in the host defense against bacterial and fungal infections, but their inappropriate activation also contributes to tissue damage during autoimmune and inflammatory diseases. Neutrophils express a large number of cell surface receptors for the recognition of pathogen invasion and the inflammatory environment. Those include G-protein-coupled chemokine and chemoattractant receptors, Fc-receptors, adhesion receptors such as selectins/selectin ligands and integrins, various cytokine receptors, as well as innate immune receptors such as Toll-like receptors and C-type lectins. The various cell surface receptors trigger very diverse signal transduction pathways including activation of heterotrimeric and monomeric G-proteins, receptor-induced and store-operated Ca2 + signals, protein and lipid kinases, adapter proteins and cytoskeletal rearrangement. Here we provide an overview of the receptors involved in neutrophil activation and the intracellular signal transduction processes they trigger. This knowledge is crucial for understanding how neutrophils participate in antimicrobial host defense and inflammatory tissue damage and may also point to possible future targets of the pharmacological therapy of neutrophil-mediated autoimmune or inflammatory diseases. PMID:23994464

[Construction and eukaryotic expression of PVAX1-hPV58mE6E7fcGB composite gene vaccine].

PubMed

Wang, He; Yu, Jiyun; Li, Li

2013-10-01

To construct and express a composite gene vaccine for human papillomavirus 58(HPV58)-associated cervical cancer, we inserted HPV58mE6E7 fusion gene into pCI-Fc-GPI eukaryotic expression vector, constructing a recombinant plasmid named pCI-sig-HPV58mE6E7-Fc-GPI. Then we further inserted fragment of sig-HPV58mE6E7Fc-GPI into the novel vaccine vector PVAX1-IRES-GM/B7, constructing PVAX1-HPV58mE6E7FcGB composite gene vaccine. PVAX1-HPV58mE6E7FcGB vaccine was successfully constructed and identified by restriction endonuclease and sequencing analysis. Eukaryotic expression of fusion antigen sig-HPV58mE6E7-Fc-GPI and molecular ad-juvant GM-CSF and B7. 1 were proved to be realized at the same time by flow cytometry and immunofluorescence. So PVAX1-HPV58mE6E7FcGB can be taken as a candidate of therapeutic vaccine for HPV58-associated tumors and their precancerous transformations.

Importance of IgG subclasses of anti-Rh antibodies for the detection of Fc-receptor-bearing human lymphocytes.

PubMed

Zupańska, B; Maślanka, K; van Loghem, E

1982-11-01

13 anti-Rh sera were compared for their usefulness in the detection of Fc-receptor-bearing lymphocytes (EAhum test). IgG subclasses of anti-Rh antibodies were determined by the antiglobulin test with monospecific sera and by the detection of Gm allotypic markers in the haemagglutination inhibition test. Six sera with IgG1 + IgG3 or IgG1 + IgG2 + IgG3 antibodies and one with pure IgG3 antibodies were found to be useful, whereas six other sera with only IgG1 were unsuitable for the EAhum test. G3m markers were detected only on the anti-Rh antibodies which were capable of forming rosettes with lymphocytes. The data show that human peripheral lymphocytes possess Fc receptors for IgG3 immunoglobulins.

Fc-fusion Proteins in Therapy: An Updated View.

PubMed

Jafari, Reza; Zolbanin, Naime M; Rafatpanah, Houshang; Majidi, Jafar; Kazemi, Tohid

2017-01-01

Fc-fusion proteins are composed of Fc region of IgG antibody (Hinge-CH2-CH3) and a desired linked protein. Fc region of Fc-fusion proteins can bind to neonatal Fc receptor (FcRn) thereby rescuing it from degradation. The first therapeutic Fc-fusion protein was introduced for the treatment of AIDS. The molecular designing is the first stage in production of Fc-fusion proteins. The amino acid residues in the Fc region and linked protein are very important in the bioactivity and affinity of the fusion proteins. Although, therapeutic monoclonal antibodies are the top selling biologics but the application of therapeutic Fc-fusion proteins in clinic is in progress and among these medications Etanercept is the most effective in therapy. At present, eleven Fc-fusion proteins have been approved by FDA. There are novel Fc-fusion proteins which are in pre-clinical and clinical development. In this article, we review the molecular and biological characteristics of Fc-fusion proteins and then further discuss the features of novel therapeutic Fc-fusion proteins. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Single chain Fc-dimer-human growth hormone fusion protein for improved drug delivery.

PubMed

Zhou, Li; Wang, Hsuan-Yao; Tong, Shanshan; Okamoto, Curtis T; Shen, Wei-Chiang; Zaro, Jennica L

2017-02-01

Fc fusion protein technology has been successfully used to generate long-acting forms of several protein therapeutics. In this study, a novel Fc-based drug carrier, single chain Fc-dimer (sc(Fc) 2 ), was designed to contain two Fc domains recombinantly linked via a flexible linker. Since the Fc dimeric structure is maintained through the flexible linker, the hinge region was omitted to further stabilize it against proteolysis and reduce FcγR-related effector functions. The resultant sc(Fc) 2 candidate preserved the neonatal Fc receptor (FcRn) binding. sc(Fc) 2 -mediated delivery was then evaluated using a therapeutic protein with a short plasma half-life, human growth hormone (hGH), as the protein drug cargo. This novel carrier protein showed a prolonged in vivo half-life and increased hGH-mediated bioactivity compared to the traditional Fc-based drug carrier. sc(Fc) 2 technology has the potential to greatly advance and expand the use of Fc-technology for improving the pharmacokinetics and bioactivity of protein therapeutics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Critical role of FcR gamma-chain, LAT, PLCgamma2 and thrombin in arteriolar thrombus formation upon mild, laser-induced endothelial injury in vivo.

PubMed

Kalia, Neena; Auger, Jocelyn M; Atkinson, Ben; Watson, Steve P

2008-05-01

The role of collagen receptor complex GPVI-FcR gamma-chain, PLCgamma2 and LAT in laser-induced thrombosis is unclear. Controversy surrounds whether collagen is exposed in this model or whether thrombosis is dependent on thrombin. This study hypothesized that collagen exposure plays a critical role in thrombus formation in this model, which was tested by investigating contributions of FcR gamma-chain, LAT, PLCgamma2 and thrombin. Thrombi were monitored using intravital microscopy in anesthetized wild-type and FcR gamma-chain, LAT and PLCgamma2 knockout mice. Hirudin (thrombin inhibitor) was administered to wild-type and FcR gamma-chain knockout mice. Significantly reduced thrombus formation was observed in FcR gamma-chain and PLCgamma2 knockouts with a greater decrease observed in LAT knockouts. Dramatic reduction was observed in wild-types treated with hirudin, with abolished thrombus formation only observed in FcR gamma-chain knockouts treated with hirudin. GPVI-FcR gamma-chain, LAT and PLCgamma2 are essential for thrombus generation and stability in this laser-induced model of injury. More importantly, a greater role for LAT was identified, which may reflect a role for it downstream of a second matrix protein receptor. However, inhibition of platelet activation by matrix proteins and thrombin generation are both required to maximally prevent thrombus formation.

A benzenediamine derivate FC-99 attenuates lupus nephritis in MRL/lpr mice via inhibiting myeloid dendritic cell-secreted BAFF

PubMed Central

Ji, Jianjian; Xu, Jingjing; Li, Fanlin; Li, Xiaojing; Gong, Wei; Song, Yuxian; Dou, Huan; Hou, Yayi

2016-01-01

Myeloid dendritic cells (DCs) can produce B-cell-activating factor (BAFF) that modulates survival and differentiation of B cells and plays a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). Toll-like receptor 4 (TLR4) signaling has important functions in the process of BAFF production. Our previous study showed that a benzenediamine derivate FC-99 possesses anti-inflammation activity and directly interacts with interleukin-1 receptor-associated kinase 4 (IRAK4), which was a pivotal molecule in TLR4 signaling. In this study, we demonstrated that FC-99 attenuated lupus nephritis in the MRL/lpr mice. FC-99 also decreased the levels of total immunoglobulin G (IgG), total IgG2a and IgM in sera, as well as the activation of B cells in the spleens of MRL/lpr mice. Moreover, FC-99 inhibited abnormal activation of myeloid DCs in spleens and reduced the levels of BAFF in sera, spleens, and kidneys of MRL/lpr mice. Furthermore, upon TLR4 stimulation with lipopolysaccharide in vitro, FC-99 inhibited IRAK4 phosphorylation, as well as the activation and BAFF production in murine bone marrow-derived DCs. These data indicate that FC-99 attenuates lupus nephritis in MRL/lpr mice via inhibiting DC-secreted BAFF, suggesting that FC-99 may be a potential therapeutic candidate for the treatment of SLE. PMID:27121231

SCM, the M Protein of Streptococcus canis Binds Immunoglobulin G

PubMed Central

Bergmann, Simone; Eichhorn, Inga; Kohler, Thomas P.; Hammerschmidt, Sven; Goldmann, Oliver; Rohde, Manfred; Fulde, Marcus

2017-01-01

The M protein of Streptococcus canis (SCM) is a virulence factor and serves as a surface-associated receptor with a particular affinity for mini-plasminogen, a cleavage product of the broad-spectrum serine protease plasmin. Here, we report that SCM has an additional high-affinity immunoglobulin G (IgG) binding activity. The ability of a particular S. canis isolate to bind to IgG significantly correlates with a scm-positive phenotype, suggesting a dominant role of SCM as an IgG receptor. Subsequent heterologous expression of SCM in non-IgG binding S. gordonii and Western Blot analysis with purified recombinant SCM proteins confirmed its IgG receptor function. As expected for a zoonotic agent, the SCM-IgG interaction is species-unspecific, with a particular affinity of SCM for IgGs derived from human, cats, dogs, horses, mice, and rabbits, but not from cows and goats. Similar to other streptococcal IgG-binding proteins, the interaction between SCM and IgG occurs via the conserved Fc domain and is, therefore, non-opsonic. Interestingly, the interaction between SCM and IgG-Fc on the bacterial surface specifically prevents opsonization by C1q, which might constitute another anti-phagocytic mechanism of SCM. Extensive binding analyses with a variety of different truncated SCM fragments defined a region of 52 amino acids located in the central part of the mature SCM protein which is important for IgG binding. This binding region is highly conserved among SCM proteins derived from different S. canis isolates but differs significantly from IgG-Fc receptors of S. pyogenes and S. dysgalactiae sub. equisimilis, respectively. In summary, we present an additional role of SCM in the pathogen-host interaction of S. canis. The detailed analysis of the SCM-IgG interaction should contribute to a better understanding of the complex roles of M proteins in streptococcal pathogenesis. PMID:28401063

Improved isolation and purification of functional human Fas receptor extracellular domain using baculovirus-silkworm expression system.

PubMed

Muraki, Michiro; Honda, Shinya

2011-11-01

To achieve an efficient isolation of human Fas receptor extracellular domain (hFasRECD), a fusion protein of hFasRECD with human IgG1 heavy chain Fc domain containing thrombin cleavage sequence at the junction site was overexpressed using baculovirus-silkworm larvae expression system. The hFasRECD part was separated from the fusion protein by the effective cleavage of the recognition site with bovine thrombin. Protein G column treatment of the reaction mixture and the subsequent cation-exchange chromatography provided purified hFasRECD with a final yield of 13.5mg from 25.0 ml silkworm hemolymph. The functional activity of the product was examined by size-exclusion chromatography analysis. The isolated hFasRECD less strongly interacted with human Fas ligand extracellular domain (hFasLECD) than the Fc domain-bridged counterpart, showing the contribution of antibody-like avidity in the latter case. The purified glycosylated hFasRECD presented several discrete bands in the disulphide-bridge non-reducing SDS-PAGE analysis, and virtually all of the components were considered to participate in the binding to hFasLECD. The attached glycans were susceptible to PNGase F digestion, but mostly resistant to Endo Hf digestion under denaturing conditions. One of the components exhibited a higher susceptibility to PNGase F digestion under non-denaturing conditions. Copyright © 2011 Elsevier Inc. All rights reserved.

Rethinking reverse cholesterol transport and dysfunctional high-density lipoproteins.

PubMed

Gillard, Baiba K; Rosales, Corina; Xu, Bingqing; Gotto, Antonio M; Pownall, Henry J

2018-04-12

Human plasma high-density lipoprotein cholesterol concentrations are a negative risk factor for atherosclerosis-linked cardiovascular disease. Pharmacological attempts to reduce atherosclerotic cardiovascular disease by increasing plasma high-density lipoprotein cholesterol have been disappointing so that recent research has shifted from HDL quantity to HDL quality, that is, functional vs dysfunctional HDL. HDL has varying degrees of dysfunction reflected in impaired reverse cholesterol transport (RCT). In the context of atheroprotection, RCT occurs by 2 mechanisms: one is the well-known trans-hepatic pathway comprising macrophage free cholesterol (FC) efflux, which produces early forms of FC-rich nascent HDL (nHDL). Lecithin:cholesterol acyltransferase converts HDL-FC to HDL-cholesteryl ester while converting nHDL from a disc to a mature spherical HDL, which transfers its cholesteryl ester to the hepatic HDL receptor, scavenger receptor B1 for uptake, conversion to bile salts, or transfer to the intestine for excretion. Although widely cited, current evidence suggests that this is a minor pathway and that most HDL-FC and nHDL-FC rapidly transfer directly to the liver independent of lecithin:cholesterol acyltransferase activity. A small fraction of plasma HDL-FC enters the trans-intestinal efflux pathway comprising direct FC transfer to the intestine. SR-B1 -/- mice, which have impaired trans-hepatic FC transport, are characterized by high plasma levels of a dysfunctional FC-rich HDL that increases plasma FC bioavailability in a way that produces whole-body hypercholesterolemia and multiple pathologies. The design of future therapeutic strategies to improve RCT will have to be formulated in the context of these dual RCT mechanisms and the role of FC bioavailability. Copyright © 2018 National Lipid Association. Published by Elsevier Inc. All rights reserved.

Antibody Functional Assays as Measures of Fc Receptor-Mediated Immunity to HIV - New Technologies and their Impact on the HIV Vaccine Field.

PubMed

Wines, Bruce D; Billings, Hugh; Mclean, Milla R; Kent, Stephen J; Hogarth, P Mark

2017-01-01

There is now intense interest in the role of HIV-specific antibodies and the engagement of FcγR functions in the control and prevention of HIV infection. The analyses of the RV144 vaccine trial, natural progression cohorts, and macaque models all point to a role for Fc-dependent effector functions, such as cytotoxicity (ADCC) or phagocytosis (ADCP), in the control of HIV. However, reliable assays that can be reproducibly used across different laboratories to measure Fcdependent functions, such as antibody dependent cellular cytotoxicity (ADCC) are limited. This brief review highlights the importance of Fc properties for immunity to HIV, particularly via FcγR diversity and function. We discuss assays used to study FcR mediated functions of HIV-specific Ab, including our recently developed novel cell-free ELISA using homo-dimeric FcγR ectodomains to detect functionally relevant viral antigen-specific antibodies. The binding of these dimeric FcγR ectodomains, to closely spaced pairs of IgG Fc, mimics the engagement and cross-linking of Fc receptors by IgG opsonized virions or infected cells as the essential prerequisite to the induction of Ab-dependent effector functions. The dimeric FcγR ELISA reliably correlates with ADCC in patient responses to influenza. The assay is amenable to high throughput and could be standardized across laboratories. We propose the assay has broader implications for the evaluation of the quality of antibody responses in viral infections and for the rapid evaluation of responses in vaccine development campaigns for HIV and other viral infections. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Interaction of human, rat, and mouse immunoglobulin A (IgA) with Staphylococcal superantigen-like 7 (SSL7) decoy protein and leukocyte IgA receptor.

PubMed

Wines, Bruce D; Ramsland, Paul A; Trist, Halina M; Gardam, Sandra; Brink, Robert; Fraser, John D; Hogarth, P Mark

2011-09-23

Host survival depends on an effective immune system and pathogen survival on the effectiveness of immune evasion mechanisms. Staphylococcus aureus utilizes a number of molecules to modulate host immunity, including the SSL family of which SSL7 binds IgA and inhibits Fcα receptor I (FcαRI)-mediated function. Other Gram-positive bacterial pathogens produce IgA binding proteins, which, similar to SSL7, also bind the Fc at the CH2/CH3 interface (the junction between constant domains 2 and 3 of the heavy chain). The opposing activities of the host FcαRI-IgA receptor ligand pair and the pathogen decoy proteins select for host and pathogen variants, which exert stronger protection or evasion, respectively. Curiously, mouse but not rat IgA contains a putative N-linked glycosylation site in the center of this host receptor and pathogen-binding site. Here, we demonstrate that this site is glycosylated and that the effect of amino acid changes and glycosylation of the CH2/CH3 interface inhibits interaction with the pathogen IgA binding protein SSL7, while maintaining binding of pIgR, essential to the biosynthesis and transport of SIgA.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanchez-Miranda, Elizabeth; Ibarra-Sanchez, Alfredo; Gonzalez-Espinosa, Claudia, E-mail: cgonzal@cinvestav.mx

IgE-antigen-dependent crosslinking of the high affinity IgE receptor (Fc{epsilon}RI) on mast cells leads to degranulation, leukotriene synthesis and cytokine production. Calcium (Ca{sup 2+}) mobilization is a sine qua non requisite for degranulation, allowing the rapid secretion of stored pro-inflammatory mediators responsible for allergy symptoms. Fyn is a Src-family kinase that positively controls Fc{epsilon}RI-induced mast cell degranulation. However, our understanding of the mechanism connecting Fyn activation to secretion of pre-synthesized mediators is very limited. We analyzed Fc{epsilon}RI-dependent Ca{sup 2+} mobilization in bone marrow-derived mast cells (BMMCs) differentiated from WT and Fyn -/- knock out mice. Fyn -/- BMMCs showed a markedmore » defect in extracellular Ca{sup 2+} influx after Fc{epsilon}RI crosslinking but not after thapsigargin addition. High concentrations of Gadolinium (Gd{sup 3+}) partially blocked Fc{epsilon}RI-induced Ca{sup 2+} influx in WT cells but, in contrast, completely inhibited Ca{sup 2+} mobilization in Fyn -/- cells. Low concentrations of an inhibitor of the canonical transient receptor potential (TRPC) Ca{sup 2+} channels (2-aminoethoxyphenyl-borane, 2-APB) blocked Fc{epsilon}RI-induced maximal Ca{sup 2+} rise in WT but not in Fyn -/- cells. Ca{sup 2+} entry through Fyn-controlled, 2-APB sensitive channels was found to be important for full degranulation and IL-2 mRNA accumulation in WT cells. Immunoprecipitation assays showed that Fyn kinase interacts with TRPC 3/6/7 channels after IgE-antigen stimulation, but its association is not related to protein tyrosine phosphorylation. Results indicate Fyn kinase mediates the receptor-dependent activation of TRPC channels that contribute to degranulation in Fc{epsilon}RI-stimulated mast cells.« less

NKG2A inhibits NKG2C effector functions of γδ T cells: implications in health and disease.

PubMed

Angelini, Daniela F; Zambello, Renato; Galandrini, Ricciarda; Diamantini, Adamo; Placido, Roberta; Micucci, Federica; Poccia, Fabrizio; Semenzato, Giuseppe; Borsellino, Giovanna; Santoni, Angela; Battistini, Luca

2011-01-01

The CD94/NKG2 complex is expressed on T and NK lymphocytes. CD94 molecules covalently associate to activating or inhibitory NKG2 molecules, and their expression finely tunes cell responses. Human γδ T cells express several NKRs. Expression of these receptors is confined to the cytolytic Vδ2 subset, which coexpresses the FcγRIII CD16 and CD45RA and has been defined as Vγ9Vδ2 T(EMRA) cells. We show that the CD94/NKG2C complex, associated with KARAP/DAP12, is fully functional in γδ T cells, as determined by measuring IFN-γ production, T cell proliferation, and cytolytic activity by γδ lymphocytes. In contrast, NKG2A expression was found on all γδ T cell memory subsets, suggesting a crucial role of the inhibitory signal provided by this receptor on γδ T cell responses. Moreover, we found Vγ9Vδ2 T(EMRA), NK, and CD8+ αβ T cells coexpressing NKG2A and NKG2C receptors. Functional experiments showed that the inhibitory signal mediated by the NKG2A receptor prevails when double-positive cells are activated. Finally, NKG2A expression on γδ LDGL correlates with asymptomatic pathology, even in the presence of NKG2C coexpression, whereas in symptomatic patients affected by severe disease, the inhibitory NKG2A receptor is absent, and a variety of activatory NKRs was found. We propose that the silent behavior of γδ cells in LDGL patients is a result of effective inhibitory HLA class I receptors.

STAT1-Induced HLA class I Upregulation Enhances Immunogenicity and Clinical Response to anti-EGFR mAb Cetuximab Therapy in HNC Patients

PubMed Central

Srivastava, Raghvendra M.; Trivedi, Sumita; Concha-Benavente, Fernando; Hyun-bae, Jie; Wang, Lin; Seethala, Raja R.; Branstetter, Barton F.; Ferrone, Soldano; Ferris, Robert L.

2015-01-01

The goal of this study was to characterize the molecular mechanisms underlying cetuximab-mediated upregulation of HLA class I antigen-processing machinery components in head and neck cancer (HNC) cells and to determine the clinical significance of these changes in cetuximab-treated HNC patients. Flow cytometry, signaling studies and chromatin immunoprecipitation (ChIP) assays were performed using HNC cells treated with cetuximab alone or with Fcγ receptor (FcγR)-bearing lymphocytes to establish the mechanism of EGFR-dependent regulation of HLA APM expression. A prospective phase II clinical trial of neoadjuvant cetuximab was utilized to correlate HLA class I expression with clinical response in HNC patients. EGFR blockade triggered STAT1 activation and HLA upregulation, in a src homology-containing protein (SHP)-2-dependent fashion, more prominently in HLA-B/C than in HLA-A alleles. EGFR signaling blockade also enhanced IFNγ receptor 1 (IFNAR) expression, augmenting induction of HLA class I and TAP1/2 expression by IFNγ, which was abrogated in STAT1−/− cells. Cetuximab enhanced HNC cell recognition by EGFR853–861-specific CTLs, and notably enhanced surface presentation of a non-EGFR peptide (MAGE-3271–279). HLA class I upregulation was significantly associated with clinical response in cetuximab-treated HNC patients. EGFR induces HLA downregulation through SHP-2/STAT1 suppression. Reversal of HLA class I downregulation was more prominent in clinical responders to cetuximab therapy, supporting an important role for adaptive immunity in cetuximab antitumor activity. Abrogating EGFR-induced immune escape mechanisms and restoring STAT1 signaling to reverse HLA downregulation using cetuximab should be combined with strategies to enhance adaptive cellular immunity. PMID:25972070

Anticancer effects of the engineered stem cells transduced with therapeutic genes via a selective tumor tropism caused by vascular endothelial growth factor toward HeLa cervical cancer cells.

PubMed

Kim, Hye-Sun; Yi, Bo-Rim; Hwang, Kyung-A; Kim, Seung U; Choi, Kyung-Chul

2013-10-01

The aim of the present study was to investigate the therapeutic efficacy of genetically engineered stem cells (GESTECs) expressing bacterial cytosine deaminase (CD) and/or human interferon-beta (IFN-β) gene against HeLa cervical cancer and the migration factors of the GESTECs toward the cancer cells. Anticancer effect of GESTECs was examined in a co-culture with HeLa cells using MTT assay to measure cell viability. A transwell migration assay was performed so as to assess the migration capability of the stem cells to cervical cancer cells. Next, several chemoattractant ligands and their receptors related to a selective migration of the stem cells toward HeLa cells were determined by real-time PCR. The cell viability of HeLa cells was decreased in response to 5-fluorocytosine (5-FC), a prodrug, indicating that 5-fluorouracil (5-FU), a toxic metabolite, was converted from 5-FC by CD gene and it caused the cell death in a co-culture system. When IFN-β was additionally expressed with CD gene by these GESTECs, the anticancer activity was significantly increased. In the migration assay, the GESTECs selectively migrated to HeLa cervical cancer cells. As results of real-time PCR, chemoattractant ligands such as MCP-1, SCF, and VEGF were expressed in HeLa cells, and several receptors such as uPAR, VEGFR2, and c-kit were produced by the GESTECs. These GESTECs transduced with CD gene and IFN-β may provide a potential of a novel gene therapy for anticervical cancer treatments via their selective tumor tropism derived from VEGF and VEGFR2 expressions between HeLa cells and the GESTECs.

[Role of Langerhans cells in the physiopathology of atopic dermatitis].

PubMed

Bieber, T

1995-12-01

The demonstration of IgE receptors on the surface of epidermal dendritic cells and on other antigen presenting cells is a crucial element in the understanding of the pathophysiological role of these cells in the genesis of atopic disease, and especially the atopic dermatitis (AD). The sensibilisation phase to an aeroallergen at the level of nasal or bronchial mucosa and even at the skin may be mediated by dendritic cells expressing Fc epsilon RI. Distinct forms of AD may then represent the equivalent of the ellicitation phase of the classical allergic contact dermatitis. Fc epsilon RI would lead, via specific IgE, to an efficient antigen capture, to the activation of the dendritic cells and finally to an antigen presentation. Thus, AD may represent the paradigma of an IgE-mediated type IV reaction.

PF4/heparin-antibody complex induces monocyte tissue factor expression and release of tissue factor positive microparticles by activation of FcγRI

PubMed Central

Glover, Sam L.; Jonas, William; McEachron, Troy; Pawlinski, Rafal; Arepally, Gowthami M.; Key, Nigel S.; Mackman, Nigel

2012-01-01

Heparin-induced thrombocytopenia (HIT) is a potentially devastating form of drug-induced thrombocytopenia that occurs in patients receiving heparin for prevention or treatment of thrombosis. Patients with HIT develop autoantibodies to the platelet factor 4 (PF4)/heparin complex, which is termed the HIT Ab complex. Despite a decrease in the platelet count, the most feared complication of HIT is thrombosis. The mechanism of thrombosis in HIT remains poorly understood. We investigated the effects of the HIT Ab complex on tissue factor (TF) expression and release of TF-positive microparticles in peripheral blood mononuclear cells and monocytes. To model these effects ex vivo, we used a murine mAb specific for the PF4/heparin complex (KKO), as well as plasma from patients with HIT. We found that the HIT Ab complex induced TF expression in monocytes and the release of TF-positive microparticles. Further, we found that induction of TF is mediated via engagement of the FcγRI receptor and activation of the MEK1-ERK1/2 signaling pathway. Our data suggest that monocyte TF may contribute to the development of thrombosis in patients with HIT. PMID:22394597

Functional Haplotypes of Fc gamma (Fcγ) receptor (FcγRIIA and FcγRIIIB) predict risk to repeated episodes of severe malarial anemia and mortality in Kenyan children

PubMed Central

Ouma, Collins; Davenport, Gregory C.; Garcia, Steven; Kempaiah, Prakasha; Chaudhary, Ateefa; Were, Tom; Anyona, Samuel B.; Raballah, Evans; Konah, Stephen N.; Hittner, James B.; Vulule, John M.; Ong’echa, John M.; Perkins, Douglas J.

2011-01-01

Development of protective immunity against Plasmodium falciparum is partially mediated through binding of malaria-specific IgG to Fc gamma (γ) receptors. Variation in human FcγRIIA-H/R-131 and FcγRIIIB-NA1/NA2 affect differential binding of IgG sub-classes. Since variability in FcγR may play an important role in severe malarial anemia (SMA) pathogenesis by mediating phagocytosis of red blood cells and triggering cytokine production, the relationship between FcγRIIA-H/R131 and FcγRIIIB-NA1/NA2 haplotypes and susceptibility to SMA (Hb<6.0g/dL) was investigated in Kenyan children (n=528) with acute malaria residing in a holoendemic P. falciparum transmission region. In addition, the association between carriage of the haplotypes and repeated episodes of SMA and all-cause mortality were investigated over a three-year follow-up period. Since variability in FcγR can alter interferon (IFN)-γ production, a mediator of innate and adaptive immune responses, functional associations between the haplotypes and IFN-γ were also explored. During acute malaria, children with SMA had elevated peripheral IFN-γ levels (P=0.006). Although multivariate logistic regression analyses (controlling for covariates) revealed no associations between the FcγR haplotypes and susceptibility to SMA during acute infection, the FcγRIIA-131H/FcγRIIIB-NA1 haplotype was associated with decreased peripheral IFN-γ (P=0.046). Longitudinal analyses showed that carriage of the FcγRIIA-131H/FcγRIIIB-NA1 haplotype was associated with reduced risk of SMA (RR; 0.65, 95%CI, 0.46-0.90; P=0.012) and all-cause mortality (P=0.002). In contrast, carriers of the FcγRIIA-131H/FcγRIIIB-NA2 haplotype had increased susceptibility to SMA (RR; 1.47, 95%CI, 1.06-2.04; P=0.020). Results here demonstrate that variation in the FcγR gene alters susceptibility to repeated episodes of SMA and mortality, as well as functional changes in IFN-γ production. PMID:21818580

Macrophage ABCA1 reduces MyD88-dependent Toll-like receptor trafficking to lipid rafts by reduction of lipid raft cholesterol[S

PubMed Central

Zhu, Xuewei; Owen, John S.; Wilson, Martha D.; Li, Haitao; Griffiths, Gary L.; Thomas, Michael J.; Hiltbold, Elizabeth M.; Fessler, Michael B.; Parks, John S.

2010-01-01

We previously showed that macrophages from macrophage-specific ATP-binding cassette transporter A1 (ABCA1) knockout (Abca1-M/-M) mice had an enhanced proinflammatory response to the Toll-like receptor (TLR) 4 agonist, lipopolysaccharide (LPS), compared with wild-type (WT) mice. In the present study, we demonstrate a direct association between free cholesterol (FC), lipid raft content, and hyper-responsiveness of macrophages to LPS in WT mice. Abca1-M/-M macrophages were also hyper-responsive to specific agonists to TLR2, TLR7, and TLR9, but not TLR3, compared with WT macrophages. We hypothesized that ABCA1 regulates macrophage responsiveness to TLR agonists by modulation of lipid raft cholesterol and TLR mobilization to lipid rafts. We demonstrated that Abca1-M/-M vs. WT macrophages contained 23% more FC in isolated lipid rafts. Further, mass spectrometric analysis suggested raft phospholipid composition was unchanged. Although cell surface expression of TLR4 was similar between Abca1-M/-M and WT macrophages, significantly more TLR4 was distributed in membrane lipid rafts in Abca1-M/-M macrophages. Abca1-M/-M macrophages also exhibited increased trafficking of the predominantly intracellular TLR9 into lipid rafts in response to TLR9-specific agonist (CpG). Collectively, our data suggest that macrophage ABCA1 dampens inflammation by reducing MyD88-dependent TLRs trafficking to lipid rafts by selective reduction of FC content in lipid rafts. PMID:20650929

Accelerated dissociation of IgE:FcεRI complexes by disruptive inhibitors actively desensitizes allergic effector cells

PubMed Central

Eggel, Alexander; Baravalle, Günther; Hobi, Gabriel; Kim, Beomkyu; Buschor, Patrick; Forrer, Patrik; Shin, Jeoung-Sook; Vogel, Monique; Stadler, Beda M.; Dahinden, Clemens A.; Jardetzky, Theodore S.

2014-01-01

Background The remarkably stable interaction of immunoglobulin E (IgE) with its high-affinity receptor FcεRI on basophils and mast cells is critical for the induction of allergic hypersensitivity reactions. Due to the exceptionally slow dissociation rate of IgE:FcεRI complexes such allergic effector cells permanently display allergen-specific IgE on their surface and immediately respond to allergen challenge by releasing inflammatory mediators. We have recently described a novel macromolecular inhibitor that actively promotes the dissociation of IgE from FcεRI through a molecular mechanism termed facilitated dissociation. Objective Here, we assessed the therapeutic potential of this non-immunoglobulin based IgE inhibitor DARPin E2_79 as well as a novel engineered biparatopic DARPin bi53_79 and directly compared them to the established anti-IgE antibody omalizumab. Methods: IgE:FcεRI complex dissociation was analyzed in vitro using recombinant proteins in ELISA and surface plasmon resonance, ex vivo using human primary basophils with flow cytometry and in vivo using human FcεRI transgenic mice in a functional passive cutaneous anaphylaxis test. Results We show that E2_79 mediated removal of IgE from primary human basophils fully abrogates IgE-dependent cell activation and release of pro-inflammatory mediators ex vivo. Furthermore, we report that omalizumab also accelerates the dissociation of IgE from FcεRI albeit much less efficiently than E2_79. Using the biparatopic IgE targeting approach we further improved the disruptive potency of E2_79 by ~100 fold and show that disruptive IgE inhibitors efficiently prevent passive cutaneous anaphylaxis in mice expressing the human FcεRI alpha chain. Conclusion Our findings highlight the potential of such novel IgE inhibitors as important diagnostic and therapeutic tools to managing allergic diseases. PMID:24642143

Absence of Tec Family Kinases Interleukin-2 Inducible T cell Kinase (Itk) and Bruton's Tyrosine Kinase (Btk) Severely Impairs FcϵRI-dependent Mast Cell Responses*

PubMed Central

Iyer, Archana S.; Morales, J. Luis; Huang, Weishan; Ojo, Folake; Ning, Gang; Wills, Elizabeth; Baines, Joel D.; August, Avery

2011-01-01

Mast cells are critical effector cells in the pathophysiology of allergic asthma and other IgE-mediated diseases. The Tec family of tyrosine kinases Itk and Btk serve as critical signal amplifiers downstream of antigen receptors. Although both kinases are expressed and activated in mast cells following FcϵRI stimulation, their individual contributions are not clear. To determine whether these kinases play unique and/or complementary roles in FcϵRI signaling and mast cell function, we generated Itk and Btk double knock-out mice. Analyses of these mice show decreased mast cell granularity and impaired passive systemic anaphylaxis responses. This impaired response is accompanied by a significant elevation in serum IgE in Itk/Btk double knock-out mice. In vitro analyses of bone marrow-derived mast cells (BMMCs) indicated that Itk/Btk double knock-out BMMCs are defective in degranulation and cytokine secretion responses downstream to FcϵRI activation. These responses were accompanied by a significant reduction in PLCγ2 phosphorylation and severely impaired calcium responses in these cells. This defect also results in altered NFAT1 nuclear localization in double knock-out BMMCs. Network analysis suggests that although they may share substrates, Itk plays both positive and negative roles, while Btk primarily plays a positive role in mast cell FcϵRI-induced cytokine secretion. PMID:21212279

A myostatin and activin decoy receptor enhances bone formation in mice.

PubMed

Bialek, P; Parkington, J; Li, X; Gavin, D; Wallace, C; Zhang, J; Root, A; Yan, G; Warner, L; Seeherman, H J; Yaworsky, P J

2014-03-01

Myostatin is a member of the bone morphogenetic protein/transforming growth factor-β (BMP/TGFβ) super-family of secreted differentiation factors. Myostatin is a negative regulator of muscle mass as shown by increased muscle mass in myostatin deficient mice. Interestingly, these mice also exhibit increased bone mass suggesting that myostatin may also play a role in regulating bone mass. To investigate the role of myostatin in bone, young adult mice were administered with either a myostatin neutralizing antibody (Mstn-mAb), a soluble myostatin decoy receptor (ActRIIB-Fc) or vehicle. While both myostatin inhibitors increased muscle mass, only ActRIIB-Fc increased bone mass. Bone volume fraction (BV/TV), as determined by microCT, was increased by 132% and 27% in the distal femur and lumbar vertebrae, respectively. Histological evaluation demonstrated that increased BV/TV in both locations was attributed to increased trabecular thickness, trabecular number and bone formation rate. Increased BV/TV resulted in enhanced vertebral maximum compressive force compared to untreated animals. The fact that ActRIIB-Fc, but not Mstn-mAb, increased bone volume suggested that this soluble decoy receptor may be binding a ligand other than myostatin, that plays a role in regulating bone mass. This was confirmed by the significant increase in BV/TV in myostatin deficient mice treated with ActRIIB-Fc. Of the other known ActRIIB-Fc ligands, BMP3 has been identified as a negative regulator of bone mass. However, BMP3 deficient mice treated with ActRIIB-Fc showed similar increases in BV/TV as wild type (WT) littermates treated with ActRIIB-Fc. This result suggests that BMP3 neutralization is not the mechanism responsible for increased bone mass. The results of this study demonstrate that ActRIIB-Fc increases both muscle and bone mass in mice. Therefore, a therapeutic that has this dual activity represents a potential approach for the treatment of frailty. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

Chlorophyll metabolism in pollinated vs. parthenocarpic fig fruits throughout development and ripening.

PubMed

Rosianskey, Yogev; Dahan, Yardena; Yadav, Sharawan; Freiman, Zohar E; Milo-Cochavi, Shira; Kerem, Zohar; Eyal, Yoram; Flaishman, Moshe A

2016-08-01

Expression of 13 genes encoding chlorophyll biosynthesis and degradation was evaluated. Chlorophyll degradation was differentially regulated in pollinated and parthenocarpic fig fruits, leading to earlier chlorophyll degradation in parthenocarpic fruits. Varieties of the common fig typically yield a commercial summer crop that requires no pollination, although it can be pollinated. Fig fruit pollination results in larger fruit size, greener skin and darker interior inflorescence color, and slows the ripening process compared to non-pollinated fruits. We evaluated the effect of pollination on chlorophyll content and levels of transcripts encoding enzymes of the chlorophyll metabolism in fruits of the common fig 'Brown Turkey'. We cloned and evaluated the expression of 13 different genes. All 13 genes showed high expression in the fruit skin, inflorescences and leaves, but extremely low expression in roots. Pollination delayed chlorophyll breakdown in the ripening fruit skin and inflorescences. This was correlated with the expression of genes encoding enzymes in the chlorophyll biosynthesis and degradation pathways. Expression of pheophorbide a oxygenase (PAO) was strongly negatively correlated with chlorophyll levels during ripening in pollinated fruits; along with its high expression levels in yellow leaves, this supports a pivotal role for PAO in chlorophyll degradation in figs. Normalizing expression levels of all chlorophyll metabolism genes in the pollinated and parthenocarpic fruit skin and inflorescences showed three synthesis (FcGluTR1, FcGluTR2 and FcCLS1) and three degradation (FcCLH1, FcCLH2 and FcRCCR1) genes with different temporal expression in the pollinated vs. parthenocarpic fruit skin and inflorescences. FcCAO also showed different expressions in the parthenocarpic fruit skin. Thus, chlorophyll degradation is differentially regulated in the pollinated and parthenocarpic fruit skin and inflorescences, leading to earlier and more sustained chlorophyll degradation in the parthenocarpic fruit.

Platelet receptor polymorphisms do not influence Staphylococcus aureus–platelet interactions or infective endocarditis

PubMed Central

Daga, Shruti; Shepherd, James G.; Callaghan, J. Garreth S.; Hung, Rachel K.Y.; Dawson, Dana K.; Padfield, Gareth J.; Hey, Shi Y.; Cartwright, Robyn A.; Newby, David E.; Fitzgerald, J. Ross

2011-01-01

Cardiac vegetations result from bacterium–platelet adherence, activation and aggregation, and are associated with increased morbidity and mortality in infective endocarditis. The GPIIb/IIIa and FcγRIIa platelet receptors play a central role in platelet adhesion, activation and aggregation induced by endocarditis pathogens such as Staphylococcus aureus, but the influence of known polymorphisms of these receptors on the pathogenesis of infective endocarditis is unknown. We determined the GPIIIa platelet antigen PlA1/A2 and FcγRIIa H131R genotype of healthy volunteers (n = 160) and patients with infective endocarditis (n = 40), and investigated the influence of these polymorphisms on clinical outcome in infective endocarditis and S. aureus–platelet interactions in vitro. Platelet receptor genotype did not correlate with development of infective endocarditis, vegetation characteristics on echocardiogram or the composite clinical end-point of embolism, heart failure, need for surgery or mortality (P > 0.05 for all), even though patients with the GPIIIa PlA1/A1 genotype had increased in vivo platelet activation (P = 0.001). Furthermore, neither GPIIIa PlA1/A2 nor FcγRIIa H131R genotype influenced S. aureus-induced platelet adhesion, activation or aggregation in vitro (P > 0.05). Taken together, our data suggest that the GPIIIa and FcγRIIa platelet receptor polymorphisms do not influence S. aureus–platelet interactions in vitro or the clinical course of infective endocarditis. PMID:21044892

Isolation and purification of an early pregnancy factor-like molecule from culture supernatants obtained from lymphocytes of pregnant women: II. Identification of the molecule as a Fc-receptor-like molecule: a preliminary report.

PubMed

Aranha, C; Bordekar, A; Shahani, S

1998-11-01

Early pregnancy factor (EPF)-like activity from culture supernatants obtained from stimulated lymphocytes of pregnant women was characterized and identified. The enzyme-linked immunosorbent assay depending on the presence of "Fc" receptors on bovine spermatozoa was used to identify the EPF-like molecule purified by gel filtration and reverse-phase high-performance liquid chromatography. The results indicated that the crude lymphocyte culture supernatant, the EPF-positive G IV fraction obtained on gel filtration, and the EPF-positive reverse-phase high-performance liquid chromatography protein readily bound with the different concentrations of aggregated human gamma-globulin in a manner similar to that in which the standard control of aggregated human gamma-globulin binds to the bovine spermatozoa. EPF-like activity synthesized and secreted by lymphocytes during pregnancy may be a Fc-receptor-like molecule.

Interactions of phagocytes with the Lyme disease spirochete: role of the Fc receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benach, J.L.; Fleit, H.B.; Habicht, G.S.

1984-10-01

The phagocytic capacity of murine and human mononuclear and polymorphonuclear phagocytes (including peripheral blood monocytes and neutrophils), rabbit and murine peritoneal exudate cells, and the murine macrophage cell line P388D1 against the Lyme disease spirochete was studied. All of these cells were capable of phagocytosing the spirochete; phagocytosis was measured by the uptake of radiolabeled spirochetes, the appearance of immunofluorescent bodies in phagocytic cells, and electron microscopy. Both opsonized and nonopsonized organisms were phagocytosed. The uptake of opsonized organisms by neutrophils was blocked by a monoclonal antibody specific for the Fc receptor and by immune complexes; these findings suggested thatmore » most phagocytosis is mediated by the Fc receptor. Similarly, the uptake of opsonized organisms by human monocytes was inhibited by human monomeric IgG1 and by immune complexes. These results illustrate the role of immune phagocytosis of spirochetes in host defense against Lyme disease.« less

Clearance of Human IgG1-Sensitised Red Blood Cells In Vivo in Humans Relates to the In Vitro Properties of Antibodies from Alternative Cell Lines

PubMed Central

Armour, Kathryn L.; Smith, Cheryl S.; Ip, Natasha C. Y.; Ellison, Cara J.; Kirton, Christopher M.; Wilkes, Anthony M.; Williamson, Lorna M.; Clark, Michael R.

2014-01-01

We previously produced a recombinant version of the human anti-RhD antibody Fog-1 in the rat myeloma cell line, YB2/0. When human, autologous RhD-positive red blood cells (RBC) were sensitised with this IgG1 antibody and re-injected, they were cleared much more rapidly from the circulation than had been seen earlier with the original human-mouse heterohybridoma-produced Fog-1. Since the IgG have the same amino acid sequence, this disparity is likely to be due to alternative glycosylation that results from the rat and mouse cell lines. By comparing the in vitro properties of YB2/0-produced Fog-1 IgG1 and the same antibody produced in the mouse myeloma cell line NS0, we now have a unique opportunity to pinpoint the cause of the difference in ability to clear RBC in vivo. Using transfected cell lines that express single human FcγR, we showed that IgG1 made in YB2/0 and NS0 cell lines bound equally well to receptors of the FcγRI and FcγRII classes but that the YB2/0 antibody was superior in FcγRIII binding. When measuring complexed IgG binding, the difference was 45-fold for FcγRIIIa 158F, 20-fold for FcγRIIIa 158V and approximately 40-fold for FcγRIIIb. The dissimilarity was greater at 100-fold in monomeric IgG binding assays with FcγRIIIa. When used to sensitise RBC, the YB2/0 IgG1 generated 100-fold greater human NK cell antibody-dependent cell-mediated cytotoxicity and had a 103-fold advantage over the NS0 antibody in activating NK cells, as detected by CD54 levels. In assays of monocyte activation and macrophage adherence/phagocytosis, where FcγRI plays major roles, RBC sensitised with the two antibodies produced much more similar results. Thus, the alternative glycosylation profiles of the Fog-1 antibodies affect only FcγRIII binding and FcγRIII-mediated functions. Relating this to the in vivo studies confirms the importance of FcγRIII in RBC clearance. PMID:25302805

Clearance of human IgG1-sensitised red blood cells in vivo in humans relates to the in vitro properties of antibodies from alternative cell lines.

PubMed

Armour, Kathryn L; Smith, Cheryl S; Ip, Natasha C Y; Ellison, Cara J; Kirton, Christopher M; Wilkes, Anthony M; Williamson, Lorna M; Clark, Michael R

2014-01-01

We previously produced a recombinant version of the human anti-RhD antibody Fog-1 in the rat myeloma cell line, YB2/0. When human, autologous RhD-positive red blood cells (RBC) were sensitised with this IgG1 antibody and re-injected, they were cleared much more rapidly from the circulation than had been seen earlier with the original human-mouse heterohybridoma-produced Fog-1. Since the IgG have the same amino acid sequence, this disparity is likely to be due to alternative glycosylation that results from the rat and mouse cell lines. By comparing the in vitro properties of YB2/0-produced Fog-1 IgG1 and the same antibody produced in the mouse myeloma cell line NS0, we now have a unique opportunity to pinpoint the cause of the difference in ability to clear RBC in vivo. Using transfected cell lines that express single human FcγR, we showed that IgG1 made in YB2/0 and NS0 cell lines bound equally well to receptors of the FcγRI and FcγRII classes but that the YB2/0 antibody was superior in FcγRIII binding. When measuring complexed IgG binding, the difference was 45-fold for FcγRIIIa 158F, 20-fold for FcγRIIIa 158V and approximately 40-fold for FcγRIIIb. The dissimilarity was greater at 100-fold in monomeric IgG binding assays with FcγRIIIa. When used to sensitise RBC, the YB2/0 IgG1 generated 100-fold greater human NK cell antibody-dependent cell-mediated cytotoxicity and had a 103-fold advantage over the NS0 antibody in activating NK cells, as detected by CD54 levels. In assays of monocyte activation and macrophage adherence/phagocytosis, where FcγRI plays major roles, RBC sensitised with the two antibodies produced much more similar results. Thus, the alternative glycosylation profiles of the Fog-1 antibodies affect only FcγRIII binding and FcγRIII-mediated functions. Relating this to the in vivo studies confirms the importance of FcγRIII in RBC clearance.

CSF1 Restores Innate Immunity After Liver Injury in Mice and Serum Levels Indicate Outcomes of Patients With Acute Liver Failure

PubMed Central

Stutchfield, Benjamin M.; Antoine, Daniel J.; Mackinnon, Alison C.; Gow, Deborah J.; Bain, Calum C.; Hawley, Catherine A.; Hughes, Michael J.; Francis, Benjamin; Wojtacha, Davina; Man, Tak Y.; Dear, James W.; Devey, Luke R.; Mowat, Alan M.; Pollard, Jeffrey W.; Park, B. Kevin; Jenkins, Stephen J.; Simpson, Kenneth J.; Hume, David A.; Wigmore, Stephen J.; Forbes, Stuart J.

2015-01-01

Background & Aims Liver regeneration requires functional liver macrophages, which provide an immune barrier that is compromised after liver injury. The numbers of liver macrophages are controlled by macrophage colony-stimulating factor (CSF1). We examined the prognostic significance of the serum level of CSF1 in patients with acute liver injury and studied its effects in mice. Methods We measured levels of CSF1 in serum samples collected from 55 patients who underwent partial hepatectomy at the Royal Infirmary Edinburgh between December 2012 and October 2013, as well as from 78 patients with acetaminophen-induced acute liver failure admitted to the Royal Infirmary Edinburgh or the University of Kansas Medical Centre. We studied the effects of increased levels of CSF1 in uninjured mice that express wild-type CSF1 receptor or a constitutive or inducible CSF1-receptor reporter, as well as in chemokine receptor 2 (Ccr2)-/- mice; we performed fate-tracing experiments using bone marrow chimeras. We administered CSF1-Fc (fragment, crystallizable) to mice after partial hepatectomy and acetaminophen intoxication, and measured regenerative parameters and innate immunity by clearance of fluorescent microbeads and bacterial particles. Results Serum levels of CSF1 increased in patients undergoing liver surgery in proportion to the extent of liver resected. In patients with acetaminophen-induced acute liver failure, a low serum level of CSF1 was associated with increased mortality. In mice, administration of CSF1-Fc promoted hepatic macrophage accumulation via proliferation of resident macrophages and recruitment of monocytes. CSF1-Fc also promoted transdifferentiation of infiltrating monocytes into cells with a hepatic macrophage phenotype. CSF1-Fc increased innate immunity in mice after partial hepatectomy or acetaminophen-induced injury, with resident hepatic macrophage as the main effector cells. Conclusions Serum CSF1 appears to be a prognostic marker for patients with acute liver injury. CSF1 might be developed as a therapeutic agent to restore innate immune function after liver injury. PMID:26344055

Fusion partners can increase the expression of recombinant interleukins via transient transfection in 2936E cells

PubMed Central

Carter, Jane; Zhang, Jue; Dang, Thien-Lan; Hasegawa, Haruki; Cheng, Janet D; Gianan, Irene; O'Neill, Jason W; Wolfson, Martin; Siu, Sophia; Qu, Sheldon; Meininger, David; Kim, Helen; Delaney, John; Mehlin, Christopher

2010-01-01

The expression levels of five secreted target interleukins (IL-11, 15, 17B, 32, and IL23 p19 subunit) were tested with three different fusion partners in 2936E cells. When fused to the N-terminus, human serum albumin (HSA) was found to enhance the expression of both IL-17B and IL-15, cytokines which did not express at measurable levels on their own. Although the crystallizable fragment of an antibody (Fc) was also an effective fusion partner for IL-17B, Fc did not increase expression of IL-15. Fc was superior to HSA for the expression of the p19 subunit of IL-23, but no partner led to measurable levels of IL-32γ secretion. Glutathione S-transferase (GST) did not enhance the expression of any target and suppressed the production of IL-11, a cytokine which expressed robustly both on its own and when fused to HSA or Fc. Cleavage of the fusion partner was not always possible. The use of HSA or Fc as N-terminal fusions can be an effective technique to express difficult proteins, especially for applications in which the fusion partner need not be removed. PMID:20014434

Expression of Glycoproteins in Wild-Type and Vaccine Strains of Varicella Zoster Virus

DTIC Science & Technology

1990-06-18

gpV vaccinia recombinants 142 XI LIST OF FIGURES ^ig^rfi Page 1 . Structural model of the herpesvirus virion 8 2. A diagram of the VZV and HSV ...gpIV-specific antiserum 139 36. Fc receptor activity in HSV - 1 and VZV glycoprotein recombinant vaccinia viruses 145 37. The gene 14 transcription...subfamily alphaherpesvirinae. The human alphaherpesviruses are comprised of VZV and herpes simplex viruses 1 and 2 ( HSV - 1 and HSV -2). Four other

Novel Therapeutic Approaches Targeting MDSC in Myelodysplastic Syndrome

DTIC Science & Technology

2017-09-01

anti-Fc Fab fragment antibody for half hour on ice before culture for 48 hours at which point total RNA was collected for gene expression analysis...MDS BMMNCs (Figure 3A). We then cross-linked BI 836858 or CD33Ab with a respective anti- Fab antibody on ice for 30 minutes followed by 24 hour...or CD33Ab with a respective anti- Fab antibody on ice for 30 min followed by 24 h culture to mimic ligand binding to the receptor. We found that cross

Asymptomatic Dengue Infection in a Cuban Population Confirms the Protective Role of the RR Variant of the FcγRIIa Polymorphism

PubMed Central

García, Gissel; Sierra, Beatriz; Pérez, Ana B.; Aguirre, Eglys; Rosado, Ileana; Gonzalez, Narjara; Izquierdo, Alienys; Pupo, Maritza; Danay Díaz, Didye Ruiz; Sánchez, Lizet; Marcheco, Beatriz; Hirayama, Kenji; Guzmán, María G.

2010-01-01

The role of human Fcγ receptors (FcγR) has been recognized considerably over the last years. These receptors vary in their affinity for IgG subclasses and the intracellular signals elicited by them. Allelic variants of FcγR genes may influence the biological phagocyte activity, accounting for an inherited pre-disposition to disease. The specific FcγRIIa (CD32) contains a polymorphic variant (H/R131) that has been associated to a reduced risk for developing dengue hemorrhagic fever (DHF). Here, we investigated the role of this polymorphism in a very well-characterized group of Cuban individuals with antecedents of DHF, dengue fever (DF), or subclinical dengue infection. The HH131 genotype was significantly associated with dengue disease, either DF (*P = 0.016; odds ratio = 4.425; 95% confidence interval = 1.10–20.52) or DHF (P = 0.00018; odds ratio = 10.56; 95% confidence interval = 2.33–54.64) with respect to the subclinical infection. PMID:20519616

Human intravenous immunoglobulin (IVIG) preparations degranulate human neutrophils in vitro

PubMed Central

Teeling, J L; de Groot, E R; Eerenberg, A J M; Bleeker, W K; Van Mierlo, G; Aarden, L A; Hack, C E

1998-01-01

IVIG preparations have biological effects in vivo that are not fully understood. Possible effects include the property to stimulate Fc receptors on various cell types. To study whether IVIG may interact with neutrophils we developed an in vitro system, in which neutrophils, in whole blood or purified, were incubated with IVIG and assessed for degranulation by measuring the release of elastase and lactoferrin in culture medium. All commercially available IVIG preparations tested induced degranulation of neutrophils when incubated for 2 h at therapeutically relevant concentrations. In studies with blocking antibodies against Fc receptors (FcR), this degranulation was shown to be dependent on FcγRII, whereas FcγRIII had no effect. Experiments with purified neutrophils as well as binding experiments with labelled IVIG preparations indicated that neutrophil degranulation resulted from a direct interaction of IVIG with neutrophils. Using gel filtration fractions, it was found that polymeric and dimeric IgG present in IVIG was mainly responsible for the degranulation. We suggest that degranulation of neutrophils may contribute to the (side)effects of IVIG treatment in vivo. PMID:9822286

Muscle hypertrophy induced by myostatin inhibition accelerates degeneration in dysferlinopathy.

PubMed

Lee, Yun-Sil; Lehar, Adam; Sebald, Suzanne; Liu, Min; Swaggart, Kayleigh A; Talbot, C Conover; Pytel, Peter; Barton, Elisabeth R; McNally, Elizabeth M; Lee, Se-Jin

2015-10-15

Myostatin is a secreted signaling molecule that normally acts to limit muscle growth. As a result, there is extensive effort directed at developing drugs capable of targeting myostatin to treat patients with muscle loss. One potential concern with this therapeutic approach in patients with muscle degenerative diseases like muscular dystrophy is that inducing hypertrophy may increase stress on dystrophic fibers, thereby accelerating disease progression. To investigate this possibility, we examined the effect of blocking the myostatin pathway in dysferlin-deficient (Dysf(-/-)) mice, in which membrane repair is compromised, either by transgenic expression of follistatin in skeletal muscle or by systemic administration of the soluble form of the activin type IIB receptor (ACVR2B/Fc). Here, we show that myostatin inhibition by follistatin transgene expression in Dysf(-/-) mice results in early improvement in histopathology but ultimately exacerbates muscle degeneration; this effect was not observed in dystrophin-deficient (mdx) mice, suggesting that accelerated degeneration induced by follistatin transgene expression is specific to mice lacking dysferlin. Dysf(-/-) mice injected with ACVR2B/Fc showed significant increases in muscle mass and amelioration of fibrotic changes normally seen in 8-month-old Dysf(-/-) mice. Despite these potentially beneficial effects, ACVR2B/Fc treatment caused increases in serum CK levels in some Dysf(-/-) mice, indicating possible muscle damage induced by hypertrophy. These findings suggest that depending on the disease context, inducing muscle hypertrophy by myostatin blockade may have detrimental effects, which need to be weighed against the potential gains in muscle growth and decreased fibrosis. © The Author 2015. Published by Oxford University Press.

Antibody-mediated platelet phagocytosis by human macrophages is inhibited by siRNA specific for sequences in the SH2 tyrosine kinase, Syk.

PubMed

Lu, Ying; Wang, Weiming; Mao, Huiming; Hu, Hai; Wu, Yanling; Chen, Bing-Guan; Liu, Zhongmin

2011-01-01

Immune thrombocytopenia depends upon Fc receptor-mediated phagocytosis that involves signaling through the SH2 tyrosine kinase, Syk. We designed small interfering (siRNA) sequences complementary to Syk coding regions to decrease the expression of Syk in the human macrophage cell line, THP-1. To evaluate the functional effect of siRNA on phagocytosis, we developed a new in vitro assay for antibody-mediated platelet ingestion by THP-1 cells. Incubation of THP-1 cells at 37°C with fluorescence-labeled platelets and anti-platelet antibody promoted ingestion of platelets that could be quantitated by flow cytometry. Transfection of THP-1 cells with Syk-specific siRNA resulted in a reduction in the amount of FcγRII-associated Syk protein. Coincident with decreased Syk expression, we observed inhibition of antibody-mediated platelet ingestion. These results confirm a key role for Syk in antibody-mediated phagocytosis and suggest Syk-specific siRNA as a possible therapeutic candidate for immune thrombocytopenia. Copyright © 2011 Elsevier Inc. All rights reserved.

Insights into islet development and biology through characterization of a human iPSC-derived endocrine pancreas model

PubMed Central

van de Bunt, Martijn; Lako, Majlinda; Barrett, Amy; Gloyn, Anna L.; Hansson, Mattias; McCarthy, Mark I.; Honoré, Christian

2016-01-01

ABSTRACT Directed differentiation of stem cells offers a scalable solution to the need for human cell models recapitulating islet biology and T2D pathogenesis. We profiled mRNA expression at 6 stages of an induced pluripotent stem cell (iPSC) model of endocrine pancreas development from 2 donors, and characterized the distinct transcriptomic profiles associated with each stage. Established regulators of endodermal lineage commitment, such as SOX17 (log2 fold change [FC] compared to iPSCs = 14.2, p-value = 4.9 × 10−5) and the pancreatic agenesis gene GATA6 (log2 FC = 12.1, p-value = 8.6 × 10−5), showed transcriptional variation consistent with their known developmental roles. However, these analyses highlighted many other genes with stage-specific expression patterns, some of which may be novel drivers or markers of islet development. For example, the leptin receptor gene, LEPR, was most highly expressed in published data from in vivo-matured cells compared to our endocrine pancreas-like cells (log2 FC = 5.5, p-value = 2.0 × 10−12), suggesting a role for the leptin pathway in the maturation process. Endocrine pancreas-like cells showed significant stage-selective expression of adult islet genes, including INS, ABCC8, and GLP1R, and enrichment of relevant GO-terms (e.g. “insulin secretion”; odds ratio = 4.2, p-value = 1.9 × 10−3): however, principal component analysis indicated that in vitro-differentiated cells were more immature than adult islets. Integration of the stage-specific expression information with genetic data from T2D genome-wide association studies revealed that 46 of 82 T2D-associated loci harbor genes present in at least one developmental stage, facilitating refinement of potential effector transcripts. Together, these data show that expression profiling in an iPSC islet development model can further understanding of islet biology and T2D pathogenesis. PMID:27246810

Soluble activin receptor type IIB decoy receptor differentially impacts murine osteogenesis imperfecta muscle function.

PubMed

Jeong, Youngjae; Daghlas, Salah A; Kahveci, Alp S; Salamango, Daniel; Gentry, Bettina A; Brown, Marybeth; Rector, R Scott; Pearsall, R Scott; Phillips, Charlotte L

2018-02-01

Osteogenesis imperfecta (OI) is characterized by skeletal fragility and muscle weakness. In this study we investigated the effects of soluble activin type IIB receptor (sActRIIB-mFc) on muscle mass and function in 2 distinct mouse models of OI: osteogenesis imperfecta murine (oim) and +/G610C. Wild-type (WT), +/G610C, and oim/oim mice were treated from 2 to 4 months of age with Tris-buffered saline (vehicle) or sActRIIB-mFc and their hindlimb muscles evaluated for mass, morphology, and contractile function. sActRIIB-mFc-treated WT, +/G610C, and oim/oim mice had increased hindlimb muscle weights and myofiber cross-sectional area compared with vehicle-treated counterparts. sActRIIB-mFc-treated oim/oim mice also exhibited increased contractile function relative to vehicle-treated counterparts. Blocking endogenous ActRIIB was effective at increasing muscle size in mouse models of OI, and increasing contractile function in oim/oim mice. ActRIIB inhibitors may provide a potential mutation-specific therapeutic option for compromised muscle function in OI. Muscle Nerve 57: 294-304, 2018. © 2017 Wiley Periodicals, Inc.

Clinical efficacy of omalizumab in chronic spontaneous urticaria is associated with a reduction of FcεRI-positive cells in the skin.

PubMed

Metz, Martin; Staubach, Petra; Bauer, Andrea; Brehler, Randolf; Gericke, Janine; Kangas, Michael; Ashton-Chess, Joanna; Jarvis, Philip; Georgiou, Panayiotis; Canvin, Janice; Hillenbrand, Rainer; Erpenbeck, Veit J; Maurer, Marcus

2017-01-01

Background. Treatment with omalizumab, a humanized recombinant monoclonal anti-IgE antibody, results in clinical efficacy in patients with Chronic Spontaneous Urticaria (CSU). The mechanism of action of omalizumab in CSU has not been elucidated in detail. Objectives. To determine the effects of omalizumab on levels of high affinity IgE receptor-positive (FcεRI + ) and IgE-positive (IgE + ) dermal cells and blood basophils. Treatment efficacy and safety were also assessed. Study design. In a double-blind study, CSU patients aged 18‑75 years were randomized to receive 300 mg omalizumab (n=20) or placebo (n=10) subcutaneously every 4 weeks for 12 weeks. Changes in disease activity were assessed by use of the weekly Urticaria Activity Score (UAS7). Circulating IgE levels, basophil numbers and levels of expression of FcεRI + and IgE + cells in the skin and in blood basophils were determined. Results. Patients receiving omalizumab showed a significantly greater decrease in UAS7 compared with patients receiving placebo. At Week 12 the mean difference in UAS7 between treatment groups was -14.82 (p=0.0027), consistent with previous studies. Total IgE levels in serum were increased after omalizumab treatment and remained elevated up to Week 12. Free IgE levels decreased after omalizumab treatment. Mean levels of FcεRI + skin cells in patients treated with omalizumab 300 mg were decreased at Week 12 compared with baseline in the dermis of both non-lesional and lesional skin, reaching levels comparable with those seen in healthy volunteers (HVs). There were no statistically significant changes in mean FcɛRI + cell levels in the placebo group. Similar results were seen for changes in IgE + cells, although the changes were not statistically significant. The level of peripheral blood basophils increased immediately after treatment start and returned to Baseline values after the follow-up period. The levels of FcεRI and IgE expression on peripheral blood basophils were rapidly reduced by omalizumab treatment up to Week 12. Conclusions. Treatment with omalizumab resulted in rapid clinical benefits in patients with CSU. Treatment with omalizumab was associated with reduction in FcɛRI + and IgE + basophils and intradermal cells.

Unravelling Immunoglobulin G Fc N-Glycosylation: A Dynamic Marker Potentiating Predictive, Preventive and Personalised Medicine.

PubMed

Russell, Alyce; Adua, Eric; Ugrina, Ivo; Laws, Simon; Wang, Wei

2018-01-29

Multiple factors influence immunoglobulin G glycosylation, which in turn affect the glycoproteins' function on eliciting an anti-inflammatory or pro-inflammatory response. It is prudent to underscore these processes when considering the use of immunoglobulin G N -glycan moieties as an indication of disease presence, progress, or response to therapeutics. It has been demonstrated that the altered expression of genes that encode enzymes involved in the biosynthesis of immunoglobulin G N -glycans, receptors, or complement factors may significantly modify immunoglobulin G effector response, which is important for regulating the immune system. The immunoglobulin G N -glycome is highly heterogenous; however, it is considered an interphenotype of disease (a link between genetic predisposition and environmental exposure) and so has the potential to be used as a dynamic biomarker from the perspective of predictive, preventive, and personalised medicine. Undoubtedly, a deeper understanding of how the multiple factors interact with each other to alter immunoglobulin G glycosylation is crucial. Herein we review the current literature on immunoglobulin G glycoprotein structure, immunoglobulin G Fc glycosylation, associated receptors, and complement factors, the downstream effector functions, and the factors associated with the heterogeneity of immunoglobulin G glycosylation.

Activation of mTOR controls the loss of TCRζ in lupus T cells through HRES-1/Rab4-regulated lysosomal degradation

PubMed Central

Fernandez, David R.; Telarico, Tiffany; Bonilla, Eduardo; Li, Qing; Banerjee, Sanjay; Middleton, Frank A.; Phillips, Paul E.; Crow, Mary K.; Oess, Stefanie; Muller-Esterl, Werner; Perl, Andras

2008-01-01

Persistent mitochondrial hyperpolarization (MHP) and enhanced calcium fluxing underlie aberrant T-cell activation and death pathway selection in systemic lupus erythematosus. Treatment with rapamycin, which effectively controls disease activity, normalizes CD3/CD28-induced calcium fluxing but fails to influence MHP, suggesting that altered calcium fluxing is downstream or independent of mitochondrial dysfunction. Here, we show that activity of the mammalian target of rapamycin (mTOR), which is a sensor of the mitochondrial transmembrane potential, is increased in lupus T cells. Activation of mTOR causes the over-expression of the Rab5A and HRES-1/Rab4 small GTPases that regulate endocytic recycling of surface receptors. Pull-down studies revealed a direct interaction of HRES-1/Rab4 with the T-cell receptor/CD3ζ chain (TCRζ). Importantly, the deficiency of the TCRζ chain and Lck and compensatory upregulation of the Fcε receptor type I γ chain (FcεRIγ) and Syk, which mediate enhanced calcium fluxing in lupus T cells, was reversed in patients treated with rapamcyin in vivo. Knockdown of HRES-1/Rab4 by siRNA and inhibitors of lysosomal function augmented TCRζ protein levels. The results suggest that activation of mTOR causes the loss of TCRζ in lupus T cells through HRES-1/Rab4-dependent lysosomal degradation. PMID:19201859

Expression and biological effects of high levels of serum IgE in epsilon heavy chain transgenic mice.

PubMed

Adamczewski, M; Köhler, G; Lamers, M C

1991-03-01

We have generated and examined transgenic mice carrying a rearranged immunoglobulin transgene coding for the heavy chain of an IgE antibody. These mice produce the secreted form of the recombinant epsilon heavy chain. Serum IgE levels were increased at least 100-fold over control values. Transgenic epsilon mRNA was detected in spleen and thymus, not in liver and heart. Transgenic epsilon production in vitro was slightly up-regulated by T cells, but not affected by interleukin 4 in vitro or Nippostrongylus infestation in vivo. The B cell and T cell compartments and antigen-specific IgE, IgG1 and IgM responses as well as the increase in endogenous IgE after Nippostrongylus infestation in transgenic mice were normal. These data indicate that the presence of high levels of transgenic IgE did not induce class-specific suppressive mechanisms. Transgenic IgE bound to Fc epsilon receptor type I and Fc epsilon receptor type II and mediated histamine release from mast cells in vitro and an allergic skin reaction in vivo. It inhibited an ovalbumin-specific skin reaction in ovalbumin-immunized transgenic mice only during the initial phases of the immune response. This result has a bearing on the feasibility of immune therapy of allergic diseases with substances that block binding of IgE to its receptors.

Decoy Receptor 3 Improves Survival in Experimental Sepsis by Suppressing the Inflammatory Response and Lymphocyte Apoptosis.

PubMed

Liang, DongYu; Hou, YanQiang; Lou, XiaoLi; Chen, HongWei

2015-01-01

Unbalanced inflammatory response and lymphocyte apoptosis is associated with high mortality in septic patients. Decoy receptor 3 (DcR3), a member of the tumor necrosis factor receptor superfamily, is an anti-inflammatory and anti-apoptotic factor. Recently, DcR3 expression was found to be increased in septic patients. This study evaluated the therapeutic effect and mechanisms of DcR3 on cecal ligation and puncture (CLP)-induced sepsis in mice. C57BL/6 mice were subjected to CLP-induced polymicrobial sepsis. DcR3 Fc was intravenously injected 30 min before and 6 h after CLP. Bacterial clearance, cytokine production, histology, lymphocyte apoptosis and survival were evaluated. Furthermore, we investigated the systemic effects of DcR3 in in vitro lymphocyte apoptosis regulation. Our results demonstrated that DcR3 protein treatments significantly improved survival in septic mice (p <0.05). Treatment with DcR3 protein significantly reduced the inflammatory response and decreased lymphocyte apoptosis in the thymus and spleen. Histopathological findings of the lung and liver showed milder impairment after DcR3 administration. In vitro experiments showed that DcR3 Fc inhibited Fas-FasL mediated lymphocyte apoptosis. Treatment with the DcR3 protein protects mice from sepsis by suppressing the inflammatory response and lymphocyte apoptosis. DcR3 protein may be useful in treatment of sepsis.

Immobilization free electrochemical biosensor for folate receptor in cancer cells based on terminal protection.

PubMed

Ni, Jiancong; Wang, Qingxiang; Yang, Weiqiang; Zhao, Mengmeng; Zhang, Ying; Guo, Longhua; Qiu, Bin; Lin, Zhenyu; Yang, Huang-Hao

2016-12-15

The determination of folate receptor (FR) that over expressed in vast quantity of cancerous cells frequently is significant for the clinical diagnosis and treatment of cancers. Many DNA-based electrochemical biosensors have been developed for FR detection with high selectivity and sensitivity, but most of them need complicated immobilization of DNA on the electrode surface firstly, which is tedious and therefore results in the poor reproducibility. In this study, a simple, sensitive, and selective electrochemical FR biosensor in cancer cells has been proposed, which combines the advantages of the convenient immobilization-free homogeneous indium tin oxide (ITO)-based electrochemical detection strategy and the high selectivity of the terminal protection of small molecule linked DNA. The small molecule of folic acid (FA) and an electroactive molecule of ferrocence (Fc) were tethered to 3'- and 5'-end of an arbitrary single-stranded DNA (ssDNA), respectively, forming the FA-ssDNA-Fc complex. In the absence of the target FR, the FA-ssDNA-Fc was degraded by exonuclease I (Exo I) from 3'-end and produced a free Fc, diffusing freely to the ITO electrode surface and resulting in strong electrochemical signal. When the target FR was present, the FA-ssDNA-Fc was bound to FR through specific interaction with FA anchored at the 3'-end, effectively protecting the ssDNA strand from hydrolysis by Exo I. The FR-FA-ssDNA-Fc could not diffuse easily to the negatively charged ITO electrode surface due to the electrostatic repulsion between the DNA strand and the negatively charged ITO electrode, so electrochemical signal reduced. The decreased electrochemical signal has a linear relationship with the logarithm of FR concentration in range of 10fM to 10nM with a detection limit of 3.8fM (S/N=3). The proposed biosensor has been applied to detect FR in HeLa cancer cells, and the decreased electrochemical signal has a linear relationship with the logarithm of cell concentration ranging from 100-10000cell/mL. Compared with the traditional heterogeneous electrochemical FR biosensors, the proposed biosensor owns the merits of the simplicity and high specificity, presenting the great potential application in the area of early diagnosis of cancers. Copyright © 2016 Elsevier B.V. All rights reserved.

Autocrine hemokinin-1 functions as endogenous adjuvant for IgE-mediated mast cell inflammatory responses

PubMed Central

Sumpter, Tina L.; Ho, Chin H.; Pleet, Anna R.; Tkacheva, Olga A.; Shufesky, William J.; Rojas-Canales, Darling M.; Morelli, Adrian E.; Larregina, Adriana T.

2014-01-01

Background Efficient development of atopic diseases requires interaction between allergen and adjuvant to initiate and amplify underlying inflammatory responses. Substance P (SP) and hemokinin-1 (HK-1) are neuropeptides that signal via the neurokinin-1 receptor (NK1R) to promote inflammation. Mast cells initiate the symptoms and tissue effects of atopic disorders, secreting TNF and IL-6 following FcεRI crosslinking by Ag-IgE complexes, (FcεRI-MCs). Additionally, MCs express the NK1R suggesting an adjuvant role of NK1R agonists for FcεRI-MC mediated pathologies, however in depth research addressing this relevant aspect of MC biology is lacking. Objective To investigate the effect of NK1R-signaling and the individual roles of SP and HK-1 as potential adjuvants for FcεRI-MC mediated allergic disorders. Methods Bone marrow (BM) MCs derived from C57BL/6-wild type (WT) or NK1R−/− mice were used to investigate the effects of NK1R signaling of FcεRI-activated MCs. BMMCs generated from Tac1−/− mice or following culture with Tac4 siRNA were used to address the adjuvancy of SP and HK-1. WT, NK1R−/− and c-KitW-sh/W-sh mice reconstituted with WT or NK1R−/− BMMCs were utilized to evaluate NK1R signaling on FcεRI-MC-mediated passive local and systemic anaphylaxis and airway inflammation. Results FcεRI-activated MCs up-regulated NK1R and HK-1 transcripts and protein synthesis, without modifying SP. In a positive signaling loop, HK-1 promoted TNF and IL6 secretion by MC degranulation and protein synthesis the later via the PI3K/Akt/NFκB pathways. In vivo, NK1R signaling was necessary for development of passive local and systemic anaphylaxis and chronic airway inflammation. Conclusions FcεRI-stimulation of MCs promotes autocrine secretion of HK-1 which signals via NK1R to provide adjuvancy for efficient development of FcεRI-MC-mediated disorders. PMID:25201259

Interleukin-15 receptor blockade in non-human primate kidney transplantation.

PubMed

Haustein, Silke; Kwun, Jean; Fechner, John; Kayaoglu, Ayhan; Faure, Jean-Pierre; Roenneburg, Drew; Torrealba, Jose; Knechtle, Stuart J

2010-04-27

Interleukin (IL)-15 is a chemotactic factor to T cells. It induces proliferation and promotes survival of activated T cells. IL-15 receptor blockade in mouse cardiac and islet allotransplant models has led to long-term engraftment and a regulatory T-cell environment. This study investigated the efficacy of IL-15 receptor blockade using Mut-IL-15/Fc in an outbred non-human primate model of renal allotransplantation. Male cynomolgus macaque donor-recipient pairs were selected based on ABO typing, major histocompatibility complex class I typing, and carboxy-fluorescein diacetate succinimidyl ester-based mixed lymphocyte responses. Once animals were assigned to one of six treatment groups, they underwent renal transplantation and bilateral native nephrectomy. Serum creatinine level was monitored twice weekly and as indicated, and protocol biopsies were performed. Rejection was defined as a increase in serum creatinine to 1.5 mg/dL or higher and was confirmed histologically. Complete blood counts and flow cytometric analyses were performed periodically posttransplant; pharmacokinetic parameters of Mut-IL-15/Fc were assessed. Compared with control animals, Mut-IL-15/Fc-treated animals did not demonstrate increased graft survival despite adequate serum levels of Mut-IL-15/Fc. Flow cytometric analysis of white blood cell subgroups demonstrated a decrease in CD8 T-cell and natural killer cell numbers, although this did not reach statistical significance. Interestingly, two animals receiving Mut-IL-15/Fc developed infectious complications, but no infection was seen in control animals. Renal pathology varied widely. Peritransplant IL-15 receptor blockade does not prolong allograft survival in non-human primate renal transplantation; however, it reduces the number of CD8 T cells and natural killer cells in the peripheral blood.

Analysis of the Effects of the Bruton's tyrosine kinase (Btk) Inhibitor Ibrutinib on Monocyte Fcγ Receptor (FcγR) Function*

PubMed Central

Ren, Li; Campbell, Amanda; Fang, Huiqing; Gautam, Shalini; Elavazhagan, Saranya; Fatehchand, Kavin; Mehta, Payal; Stiff, Andrew; Reader, Brenda F.; Mo, Xiaokui; Byrd, John C.; Carson, William E.; Butchar, Jonathan P.; Tridandapani, Susheela

2016-01-01

The irreversible Bruton's tyrosine kinase (Btk) inhibitor ibrutinib has shown efficacy against B-cell tumors such as chronic lymphocytic leukemia and B-cell non-Hodgkin lymphoma. Fcγ receptors (FcγR) on immune cells such as macrophages play an important role in tumor-specific antibody-mediated immune responses, but many such responses involve Btk. Here we tested the effects of ibrutinib on FcγR-mediated activities in monocytes. We found that ibrutinib did not affect monocyte FcγR-mediated phagocytosis, even at concentrations higher than those achieved physiologically, but suppressed FcγR-mediated cytokine production. We confirmed these findings in macrophages from Xid mice in which Btk signaling is defective. Because calcium flux is a major event downstream of Btk, we tested whether it was involved in phagocytosis. The results showed that blocking intracellular calcium flux decreased FcγR-mediated cytokine production but not phagocytosis. To verify this, we measured activation of the GTPase Rac, which is responsible for actin polymerization. Results showed that ibrutinib did not inhibit Rac activation, nor did the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis(acetoxymethyl ester). We next asked whether the effect of ibrutinib on monocyte FcγR-mediated cytokine production could be rescued by IFNγ priming because NK cells produce IFNγ in response to antibody therapy. Pretreatment of monocytes with IFNγ abrogated the effects of ibrutinib on FcγR-mediated cytokine production, suggesting that IFNγ priming could overcome this Btk inhibition. Furthermore, in monocyte-natural killer cell co-cultures, ibrutinib did not inhibit FcγR-mediated cytokine production despite doing so in single cultures. These results suggest that combining ibrutinib with monoclonal antibody therapy could enhance chronic lymphocytic leukemia cell killing without affecting macrophage effector function. PMID:26627823

Analysis of the Effects of the Bruton's tyrosine kinase (Btk) Inhibitor Ibrutinib on Monocyte Fcγ Receptor (FcγR) Function.

PubMed

Ren, Li; Campbell, Amanda; Fang, Huiqing; Gautam, Shalini; Elavazhagan, Saranya; Fatehchand, Kavin; Mehta, Payal; Stiff, Andrew; Reader, Brenda F; Mo, Xiaokui; Byrd, John C; Carson, William E; Butchar, Jonathan P; Tridandapani, Susheela

2016-02-05

The irreversible Bruton's tyrosine kinase (Btk) inhibitor ibrutinib has shown efficacy against B-cell tumors such as chronic lymphocytic leukemia and B-cell non-Hodgkin lymphoma. Fcγ receptors (FcγR) on immune cells such as macrophages play an important role in tumor-specific antibody-mediated immune responses, but many such responses involve Btk. Here we tested the effects of ibrutinib on FcγR-mediated activities in monocytes. We found that ibrutinib did not affect monocyte FcγR-mediated phagocytosis, even at concentrations higher than those achieved physiologically, but suppressed FcγR-mediated cytokine production. We confirmed these findings in macrophages from Xid mice in which Btk signaling is defective. Because calcium flux is a major event downstream of Btk, we tested whether it was involved in phagocytosis. The results showed that blocking intracellular calcium flux decreased FcγR-mediated cytokine production but not phagocytosis. To verify this, we measured activation of the GTPase Rac, which is responsible for actin polymerization. Results showed that ibrutinib did not inhibit Rac activation, nor did the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester). We next asked whether the effect of ibrutinib on monocyte FcγR-mediated cytokine production could be rescued by IFNγ priming because NK cells produce IFNγ in response to antibody therapy. Pretreatment of monocytes with IFNγ abrogated the effects of ibrutinib on FcγR-mediated cytokine production, suggesting that IFNγ priming could overcome this Btk inhibition. Furthermore, in monocyte-natural killer cell co-cultures, ibrutinib did not inhibit FcγR-mediated cytokine production despite doing so in single cultures. These results suggest that combining ibrutinib with monoclonal antibody therapy could enhance chronic lymphocytic leukemia cell killing without affecting macrophage effector function. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

The acute effect of a mineralocorticoid receptor agonist on corticotrope secretion in Addison's disease.

PubMed

Berardelli, R; Karamouzis, I; D'Angelo, V; Fussotto, B; Minetto, M A; Ghigo, E; Giordano, R; Arvat, E

2016-05-01

Mineralocorticoid receptors (MR) in the hippocampus display an important role in the control of hypothalamic-pituitary-adrenal (HPA) axis, mediating the ''proactive'' feedback of glucocorticoids (GC). Fludrocortisone (FC), a potent MR agonist, has been shown to decrease HPA activity through a hippocampal mechanism. Since it has been demonstrated that FC shows a significant inhibition of the HPA axis response to hCRH stimulus in normal subjects, also at doses usually administered as replacement therapy in patients with Addison's disease, an FC effect at MRs in human pituitary or a GR-pituitary agonism stronger than believed until now has been postulated. Ten patients affected by autoimmune Addison's disease received: (1) placebo p.o. + placebo i.v., (2) hydrocortisone (H) 10 mg p.o. + placebo i.v., (3) FC 0.1 mg p.o. + placebo i.v., (4) FC 0.1 mg and H 10 mg p.o. + placebo i.v. to verify a possible GR FC-mediated effect that might display a repercussion on the GC-replacement therapy. H reduced ACTH (p < 0.01) and increased cortisol levels (p < 0.01) with respect to the placebo session, while FC did not affect either ACTH or cortisol levels compared to placebo, and higher ACTH and lower cortisol levels (p < 0.03 and p < 0.01) were observed compared with the H session; furthermore the co-administration of FC + H showed ACTH and cortisol profiles similar to that observed during H alone. Our study showed a lack of FC effect on corticotrope secretion in Addison's disease, thus making unlikely the hypothesis of its GR pituitary agonism and the risk of glucocorticoid excess in primary adrenal insufficiency.

Site-selective conjugation of an anticoagulant aptamer to recombinant albumins and maintenance of neonatal Fc receptor binding

NASA Astrophysics Data System (ADS)

Schmøkel, Julie; Voldum, Anders; Tsakiridou, Georgia; Kuhlmann, Matthias; Cameron, Jason; Sørensen, Esben S.; Wengel, Jesper; Howard, Kenneth A.

2017-05-01

Aptamers are an attractive molecular medicine that offers high target specificity. Nucleic acid-based aptamers, however, are prone to nuclease degradation and rapid renal excretion that require blood circulatory half-life extension enabling technologies. The long circulatory half-life, predominately facilitated by engagement with the cellular recycling neonatal Fc receptor (FcRn), and ligand transport properties of albumin promote it as an attractive candidate to improve the pharmacokinetic profile of aptamers. This study investigates the effect of Cys34 site-selective covalent attachment of a factor IXa anticoagulant aptamer on aptamer functionality and human FcRn (hFcRn) engagement using recombinant human albumin (rHA) of either a wild type (WT) or an engineered human FcRn high binding variant (HB). Albumin-aptamer conjugates, connected covalently through a heterobifunctional succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate linker, were successfully prepared and purified by high performance liquid chromatography as confirmed by gel electrophoresis band-shift analysis and matrix-assisted laser desorption/ionization time of flight. Minimal reduction (∼25%) in activity of WT-linked aptamer to that of aptamer alone was found using an anticoagulant activity assay measuring temporal levels of activated partial thrombin. Covalent albumin-aptamer conjugation, however, substantially compromized binding to hFcRn, to 10% affinity of that of non-conjugated WT, determined by biolayer interferometry. Binding could be rescued by aptamer conjugation to recombinant albumin engineered for higher FcRn affinity (HB) that exhibited an 8-fold affinity compared to WT alone. This work describes a novel albumin-based aptamer delivery system whose hFcRn binding can be increased using a HB engineered albumin.

Site-selective conjugation of an anticoagulant aptamer to recombinant albumins and maintenance of neonatal Fc receptor binding.

PubMed

Schmøkel, Julie; Voldum, Anders; Tsakiridou, Georgia; Kuhlmann, Matthias; Cameron, Jason; Sørensen, Esben S; Wengel, Jesper; Howard, Kenneth A

2017-05-19

Aptamers are an attractive molecular medicine that offers high target specificity. Nucleic acid-based aptamers, however, are prone to nuclease degradation and rapid renal excretion that require blood circulatory half-life extension enabling technologies. The long circulatory half-life, predominately facilitated by engagement with the cellular recycling neonatal Fc receptor (FcRn), and ligand transport properties of albumin promote it as an attractive candidate to improve the pharmacokinetic profile of aptamers. This study investigates the effect of Cys34 site-selective covalent attachment of a factor IXa anticoagulant aptamer on aptamer functionality and human FcRn (hFcRn) engagement using recombinant human albumin (rHA) of either a wild type (WT) or an engineered human FcRn high binding variant (HB). Albumin-aptamer conjugates, connected covalently through a heterobifunctional succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate linker, were successfully prepared and purified by high performance liquid chromatography as confirmed by gel electrophoresis band-shift analysis and matrix-assisted laser desorption/ionization time of flight. Minimal reduction (∼25%) in activity of WT-linked aptamer to that of aptamer alone was found using an anticoagulant activity assay measuring temporal levels of activated partial thrombin. Covalent albumin-aptamer conjugation, however, substantially compromized binding to hFcRn, to 10% affinity of that of non-conjugated WT, determined by biolayer interferometry. Binding could be rescued by aptamer conjugation to recombinant albumin engineered for higher FcRn affinity (HB) that exhibited an 8-fold affinity compared to WT alone. This work describes a novel albumin-based aptamer delivery system whose hFcRn binding can be increased using a HB engineered albumin.

The ambiguous ripening nature of the fig (Ficus carica L.) fruit: a gene-expression study of potential ripening regulators and ethylene-related genes

PubMed Central

Freiman, Zohar E.; Rosianskey, Yogev; Dasmohapatra, Rajeswari; Kamara, Itzhak; Flaishman, Moshe A.

2015-01-01

The traditional definition of climacteric and non-climacteric fruits has been put into question. A significant example of this paradox is the climacteric fig fruit. Surprisingly, ripening-related ethylene production increases following pre- or postharvest 1-methylcyclopropene (1-MCP) application in an unexpected auto-inhibitory manner. In this study, ethylene production and the expression of potential ripening-regulator, ethylene-synthesis, and signal-transduction genes are characterized in figs ripening on the tree and following preharvest 1-MCP application. Fig ripening-related gene expression was similar to that in tomato and apple during ripening on the tree, but only in the fig inflorescence–drupelet section. Because the pattern in the receptacle is different for most of the genes, the fig drupelets developed inside the syconium are proposed to function as parthenocarpic true fruit, regulating ripening processes for the whole accessory fruit. Transcription of a potential ripening regulator, FcMADS8, increased during ripening on the tree and was inhibited following 1-MCP treatment. Expression patterns of the ethylene-synthesis genes FcACS2, FcACS4, and FcACO3 could be related to the auto-inhibition reaction of ethylene production in 1-MCP-treated fruit. Along with FcMADS8 suppression, gene expression analysis revealed upregulation of FcEBF1, and downregulation of FcEIL3 and several FcERFs by 1-MCP treatment. This corresponded with the high storability of the treated fruit. One FcERF was overexpressed in the 1-MCP-treated fruit, and did not share the increasing pattern of most FcERFs in the tree-ripened fig. This demonstrates the potential of this downstream ethylene-signal-transduction component as an ethylene-synthesis regulator, responsible for the non-climacteric auto-inhibition of ethylene production in fig. PMID:25956879

Fibrin activates GPVI in human and mouse platelets

PubMed Central

Alshehri, Osama M.; Montague, Samantha; Watson, Stephanie K.; Frampton, Jon; Bender, Markus; Watson, Steve P.

2015-01-01

The glycoprotein VI (GPVI)-Fc receptor γ (FcRγ) chain is the major platelet signaling receptor for collagen. Paradoxically, in a FeCl3 injury model, occlusion, but not initiation of thrombus formation, is delayed in GPVI-deficient and GPVI-depleted mice. In this study, we demonstrate that GPVI is a receptor for fibrin and speculate that this contributes to development of an occlusive thrombus. We observed a marked increase in tyrosine phosphorylation, including the FcRγ chain and Syk, in human and mouse platelets induced by thrombin in the presence of fibrinogen and the αIIbβ3 blocker eptifibatide. This was not seen in platelets stimulated by a protease activated receptor (PAR)-4 peptide, which is unable to generate fibrin from fibrinogen. The pattern of tyrosine phosphorylation was similar to that induced by activation of GPVI. Consistent with this, thrombin did not induce tyrosine phosphorylation of Syk and the FcRγ chain in GPVI-deficient mouse platelets. Mouse platelets underwent full spreading on fibrin but not fibrinogen, which was blocked in the presence of a Src kinase inhibitor or in the absence of GPVI. Spreading on fibrin was associated with phosphatidylserine exposure (procoagulant activity), and this too was blocked in GPVI-deficient platelets. The ectodomain of GPVI was shown to bind to immobilized monomeric and polymerized fibrin. A marked increase in embolization was seen following FeCl3 injury in GPVI-deficient mice, likely contributing to the delay in occlusion in this model. These results demonstrate that GPVI is a receptor for fibrin and provide evidence that this interaction contributes to thrombus growth and stability. PMID:26282541

The Role of CD38 in Fcγ Receptor (FcγR)-mediated Phagocytosis in Murine Macrophages*

PubMed Central

Kang, John; Park, Kwang-Hyun; Kim, Jwa-Jin; Jo, Eun-Kyeong; Han, Myung-Kwan; Kim, Uh-Hyun

2012-01-01

Phagocytosis is a crucial event in the immune system that allows cells to engulf and eliminate pathogens. This is mediated through the action of immunoglobulin (IgG)-opsonized microbes acting on Fcγ receptors (FcγR) on macrophages, which results in sustained levels of intracellular Ca2+ through the mobilization of Ca2+ second messengers. It is known that the ADP-ribosyl cyclase is responsible for the rise in Ca2+ levels after FcγR activation. However, it is unclear whether and how CD38 is involved in FcγR-mediated phagocytosis. Here we show that CD38 is recruited to the forming phagosomes during phagocytosis of IgG-opsonized particles and produces cyclic-ADP-ribose, which acts on ER Ca2+ stores, thus allowing an increase in FcγR activation-mediated phagocytosis. Ca2+ data show that pretreatment of J774A.1 macrophages with 8-bromo-cADPR, ryanodine, blebbistatin, and various store-operated Ca2+ inhibitors prevented the long-lasting Ca2+ signal, which significantly reduced the number of ingested opsonized particles. Ex vivo data with macrophages extracted from CD38−/− mice also shows a reduced Ca2+ signaling and phagocytic index. Furthermore, a significantly reduced phagocytic index of Mycobacterium bovis BCG was shown in macrophages from CD38−/− mice in vivo. This study suggests a crucial role of CD38 in FcγR-mediated phagocytosis through its recruitment to the phagosome and mobilization of cADPR-induced intracellular Ca2+ and store-operated extracellular Ca2+ influx. PMID:22396532

A benzenediamine derivate FC-99 attenuates lupus nephritis in MRL/lpr mice via inhibiting myeloid dendritic cell-secreted BAFF.

PubMed

Ji, Jianjian; Xu, Jingjing; Li, Fanlin; Li, Xiaojing; Gong, Wei; Song, Yuxian; Dou, Huan; Hou, Yayi

2016-05-01

Myeloid dendritic cells (DCs) can produce B-cell-activating factor (BAFF) that modulates survival and differentiation of B cells and plays a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). Toll-like receptor 4 (TLR4) signaling has important functions in the process of BAFF production. Our previous study showed that a benzenediamine derivate FC-99 possesses anti-inflammation activity and directly interacts with interleukin-1 receptor-associated kinase 4 (IRAK4), which was a pivotal molecule in TLR4 signaling. In this study, we demonstrated that FC-99 attenuated lupus nephritis in the MRL/lpr mice. FC-99 also decreased the levels of total immunoglobulin G (IgG), total IgG2a and IgM in sera, as well as the activation of B cells in the spleens of MRL/lpr mice. Moreover, FC-99 inhibited abnormal activation of myeloid DCs in spleens and reduced the levels of BAFF in sera, spleens, and kidneys of MRL/lpr mice. Furthermore, upon TLR4 stimulation with lipopolysaccharide in vitro, FC-99 inhibited IRAK4 phosphorylation, as well as the activation and BAFF production in murine bone marrow-derived DCs. These data indicate that FC-99 attenuates lupus nephritis in MRL/lpr mice via inhibiting DC-secreted BAFF, suggesting that FC-99 may be a potential therapeutic candidate for the treatment of SLE. © The Author 2016. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

Generation of high-affinity, internalizing anti-FGFR2 single-chain variable antibody fragment fused with Fc for targeting gastrointestinal cancers.

PubMed

Borek, Aleksandra; Sokolowska-Wedzina, Aleksandra; Chodaczek, Grzegorz; Otlewski, Jacek

2018-01-01

Fibroblast growth factor receptors (FGFRs) are promising targets for antibody-based cancer therapies, as their substantial overexpression has been found in various tumor cells. Aberrant activation of FGF receptor 2 (FGFR2) signaling through overexpression of FGFR2 and/or its ligands, mutations, or receptor amplification has been reported in multiple cancer types, including gastric, colorectal, endometrial, ovarian, breast and lung cancer. In this paper, we describe application of the phage display technology to produce a panel of high affinity single chain variable antibody fragments (scFvs) against the extracellular ligand-binding domain of FGFR2 (ECD_FGFR2). The binders were selected from the human single chain variable fragment scFv phage display libraries Tomlinson I + J and showed high specificity and binding affinity towards human FGFR2 with nanomolar KD values. To improve the affinity of the best binder selected, scFvF7, we reformatted it to a bivalent diabody format, or fused it with the Fc region (scFvF7-Fc). The scFvF7-Fc antibody construct presented the highest affinity for FGFR2, with a KD of 0.76 nM, and was selectively internalized into cancer cells overexpressing FGFR2, Snu-16 and NCI-H716. Finally, we prepared a conjugate of scFvF7-Fc with the cytotoxic drug monomethyl-auristatin E (MMAE) and evaluated its cytotoxicity. The conjugate delivered MMAE selectively to FGFR2-positive tumor cells. These results indicate that scFvF7-Fc-vcMMAE is a highly potent molecule for the treatment of cancers with FGFR2 overexpression.

Bio-nanocapsule-based scaffold improves the sensitivity and ligand-binding capacity of mammalian receptors on the sensor chip.

PubMed

Iijima, Masumi; Yoshimoto, Nobuo; Niimi, Tomoaki; Maturana, Andrés D; Kuroda, Shun'ichi

2016-06-01

Mammalian receptors are recognized as target molecules for drug discovery, and chemical libraries have been screened for both potential antagonists and agonists mainly by ligand-binding assays using immobilized receptors. A bio-nanocapsule (BNC) of approximately 30 nm that displays a tandem form of the protein A-derived immunoglobulin G (IgG) Fc-binding Z domains (denoted as ZZ-BNC) has been developed for both clustering and oriented immobilization of IgGs on the solid phase of immunosensors. In this study, human IgG1 Fc-fused vascular endothelial growth factor (VEGF) receptor was immobilized through ZZ-BNC on the sensor chip of quartz crystal microbalance (ZZ-BNC-coating). When compared with direct adsorption and protein A-coating, the sensor chip showed higher sensitivity (∽46- and ∽165-fold, respectively) and larger ligand-binding capacity (∽4- and ∽18-fold, respectively). Furthermore, the number of VEGF molecules bound to its receptor increased from 0.20 (direct adsorption) to 2.06 by ZZ-BNC-coating, strongly suggesting that ZZ-BNC reduced the steric hindrance near ligand recognition sites through oriented immobilization. Similarly, the sensitivity and ligand-binding capacity of leptin and prolactin receptors were both enhanced at a level comparable to that observed for the VEGF receptor. Thus, the combination of ZZ-BNC and Fc-fused receptors could significantly improve the function of ligand-binding assays. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cetuximab-activated natural killer (NK) and dendritic cells (DC) collaborate to trigger tumor antigen-specific T cell immunity in head and neck cancer patients

PubMed Central

Srivastava, Raghvendra M.; Lee, Steve C.; Filho, Pedro A. Andrade; Lord, Christopher A.; Jie, Hyun-bae; Davidson, H. Carter; López-Albaitero, Andrés; Gibson, Sandra P.; Gooding, William E.; Ferrone, Soldano; Ferris, Robert L.

2013-01-01

Purpose Tumor antigen (TA)-specific monoclonal antibodies (mAb) block oncogenic signaling and induce Fcγ receptor (FcγR)-mediated cytotoxicity. However, the role of CD8+ cytotoxic T lymphocyte (CTL) and FcγR in initiating innate and adaptive immune responses in mAb-treated human cancer patients is still emerging. Experimental Design FcγRIIIa codon 158 polymorphism was correlated with survival in 107 cetuximab-treated head and neck cancer (HNC) patients. Flow cytometry was performed to quantify EGFR-specific T cells in cetuximab-treated HNC patients. The effect of cetuximab on NK cell, dendritic cell (DC), and T cell activation was measured using IFN-γ release assays and flow cytometry. Results FcγR IIIa polymorphism did not predict clinical outcome in cetuximab-treated HNC patients, however elevated circulating EGFR -specific CD8+ 853-861 T cells were found in cetuximab-treated HNC patients (p<0.005). Cetuximab promoted EGFR-specific cellular immunity through the interaction of EGFR+ tumor cells and FcγRIIIa on NK cells, but not on the polymorphism per se. Cetuximab-activated NK cells induced IFN-γ dependent expression of DC maturation markers, antigen presentation machinery (APM) components such as TAP-1/2, and Th1 chemokines through NKG2D/MICA binding. Cetuximab initiated adaptive immune responses via NK-cell induced DC maturation, which enhanced cross-presentation to CTL specific for EGFR as well as another TA, MAGE-3. Conclusion Cetuximab-activated NK cells promote DC maturation and CD8+ T cell priming, leading to TA spreading and Th1 cytokine release through ‘NK-DC cross-talk.’ FcγRIIIa polymorphism did not predict clinical response to cetuximab, but was necessary for NK-DC interaction and mAb induced cross-presentation. EGFR-specific T cells in cetuximab treated HNC patients may contribute to clinical response. PMID:23444227

Multivariate Pattern Classification of Facial Expressions Based on Large-Scale Functional Connectivity.

PubMed

Liang, Yin; Liu, Baolin; Li, Xianglin; Wang, Peiyuan

2018-01-01

It is an important question how human beings achieve efficient recognition of others' facial expressions in cognitive neuroscience, and it has been identified that specific cortical regions show preferential activation to facial expressions in previous studies. However, the potential contributions of the connectivity patterns in the processing of facial expressions remained unclear. The present functional magnetic resonance imaging (fMRI) study explored whether facial expressions could be decoded from the functional connectivity (FC) patterns using multivariate pattern analysis combined with machine learning algorithms (fcMVPA). We employed a block design experiment and collected neural activities while participants viewed facial expressions of six basic emotions (anger, disgust, fear, joy, sadness, and surprise). Both static and dynamic expression stimuli were included in our study. A behavioral experiment after scanning confirmed the validity of the facial stimuli presented during the fMRI experiment with classification accuracies and emotional intensities. We obtained whole-brain FC patterns for each facial expression and found that both static and dynamic facial expressions could be successfully decoded from the FC patterns. Moreover, we identified the expression-discriminative networks for the static and dynamic facial expressions, which span beyond the conventional face-selective areas. Overall, these results reveal that large-scale FC patterns may also contain rich expression information to accurately decode facial expressions, suggesting a novel mechanism, which includes general interactions between distributed brain regions, and that contributes to the human facial expression recognition.

Multivariate Pattern Classification of Facial Expressions Based on Large-Scale Functional Connectivity

PubMed Central

Liang, Yin; Liu, Baolin; Li, Xianglin; Wang, Peiyuan

2018-01-01

It is an important question how human beings achieve efficient recognition of others’ facial expressions in cognitive neuroscience, and it has been identified that specific cortical regions show preferential activation to facial expressions in previous studies. However, the potential contributions of the connectivity patterns in the processing of facial expressions remained unclear. The present functional magnetic resonance imaging (fMRI) study explored whether facial expressions could be decoded from the functional connectivity (FC) patterns using multivariate pattern analysis combined with machine learning algorithms (fcMVPA). We employed a block design experiment and collected neural activities while participants viewed facial expressions of six basic emotions (anger, disgust, fear, joy, sadness, and surprise). Both static and dynamic expression stimuli were included in our study. A behavioral experiment after scanning confirmed the validity of the facial stimuli presented during the fMRI experiment with classification accuracies and emotional intensities. We obtained whole-brain FC patterns for each facial expression and found that both static and dynamic facial expressions could be successfully decoded from the FC patterns. Moreover, we identified the expression-discriminative networks for the static and dynamic facial expressions, which span beyond the conventional face-selective areas. Overall, these results reveal that large-scale FC patterns may also contain rich expression information to accurately decode facial expressions, suggesting a novel mechanism, which includes general interactions between distributed brain regions, and that contributes to the human facial expression recognition. PMID:29615882

Dexamethasone Regulates EphA5, a Potential Inhibitory Factor with Osteogenic Capability of Human Bone Marrow Stromal Cells

PubMed Central

Yamada, Tsuyoshi; Yoshii, Toshitaka; Yasuda, Hiroaki; Okawa, Atsushi; Sotome, Shinichi

2016-01-01

We previously demonstrated the importance of quality management procedures for the handling of human bone marrow stromal cells (hBMSCs) and provided evidence for the existence of osteogenic inhibitor molecules in BMSCs. One candidate inhibitor is the ephrin type-A receptor 5 (EphA5), which is expressed in hBMSCs and upregulated during long-term culture. In this study, forced expression of EphA5 diminished the expression of osteoblast phenotypic markers. Downregulation of endogenous EphA5 by dexamethasone treatment promoted osteoblast marker expression. EphA5 could be involved in the normal growth regulation of BMSCs and could be a potential marker for replicative senescence. Although Eph forward signaling stimulated by ephrin-B-Fc promoted the expression of ALP mRNA in BMSCs, exogenous addition of EphA5-Fc did not affect the ALP level. The mechanism underlying the silencing of EphA5 in early cultures remains unclear. EphA5 promoter was barely methylated in hBMSCs while histone deacetylation could partially suppress EphA5 expression in early-passage cultures. In repeatedly passaged cultures, the upregulation of EphA5 independent of methylation could competitively inhibit osteogenic signal transduction pathways such as EphB forward signaling. Elucidation of the potential inhibitory function of EphA5 in hBMSCs may provide an alternative approach for lineage differentiation in cell therapy strategies and regenerative medicine. PMID:27057165

Acute inhibition of myostatin-family proteins preserves skeletal muscle in mouse models of cancer cachexia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benny Klimek, Margaret E.; Aydogdu, Tufan; Link, Majik J.

2010-01-15

Cachexia, progressive loss of fat and muscle mass despite adequate nutrition, is a devastating complication of cancer associated with poor quality of life and increased mortality. Myostatin is a potent tonic muscle growth inhibitor. We tested how myostatin inhibition might influence cancer cachexia using genetic and pharmacological approaches. First, hypermuscular myostatin null mice were injected with Lewis lung carcinoma or B16F10 melanoma cells. Myostatin null mice were more sensitive to tumor-induced cachexia, losing more absolute mass and proportionately more muscle mass than wild-type mice. Because myostatin null mice lack expression from development, however, we also sought to manipulate myostatin acutely.more » The histone deacetylase inhibitor Trichostatin A has been shown to increase muscle mass in normal and dystrophic mice by inducing the myostatin inhibitor, follistatin. Although Trichostatin A administration induced muscle growth in normal mice, it failed to preserve muscle in colon-26 cancer cachexia. Finally we sought to inhibit myostatin and related ligands by administration of the Activin receptor extracellular domain/Fc fusion protein, ACVR2B-Fc. Systemic administration of ACVR2B-Fc potently inhibited muscle wasting and protected adipose stores in both colon-26 and Lewis lung carcinoma cachexia, without affecting tumor growth. Enhanced cachexia in myostatin knockouts indicates that host-derived myostatin is not the sole mediator of muscle wasting in cancer. More importantly, skeletal muscle preservation with ACVR2B-Fc establishes that targeting myostatin-family ligands using ACVR2B-Fc or related molecules is an important and potent therapeutic avenue in cancer cachexia.« less

Acute inhibition of myostatin-family proteins preserves skeletal muscle in mouse models of cancer cachexia.

PubMed

Benny Klimek, Margaret E; Aydogdu, Tufan; Link, Majik J; Pons, Marianne; Koniaris, Leonidas G; Zimmers, Teresa A

2010-01-15

Cachexia, progressive loss of fat and muscle mass despite adequate nutrition, is a devastating complication of cancer associated with poor quality of life and increased mortality. Myostatin is a potent tonic muscle growth inhibitor. We tested how myostatin inhibition might influence cancer cachexia using genetic and pharmacological approaches. First, hypermuscular myostatin null mice were injected with Lewis lung carcinoma or B16F10 melanoma cells. Myostatin null mice were more sensitive to tumor-induced cachexia, losing more absolute mass and proportionately more muscle mass than wild-type mice. Because myostatin null mice lack expression from development, however, we also sought to manipulate myostatin acutely. The histone deacetylase inhibitor Trichostatin A has been shown to increase muscle mass in normal and dystrophic mice by inducing the myostatin inhibitor, follistatin. Although Trichostatin A administration induced muscle growth in normal mice, it failed to preserve muscle in colon-26 cancer cachexia. Finally we sought to inhibit myostatin and related ligands by administration of the Activin receptor extracellular domain/Fc fusion protein, ACVR2B-Fc. Systemic administration of ACVR2B-Fc potently inhibited muscle wasting and protected adipose stores in both colon-26 and Lewis lung carcinoma cachexia, without affecting tumor growth. Enhanced cachexia in myostatin knockouts indicates that host-derived myostatin is not the sole mediator of muscle wasting in cancer. More importantly, skeletal muscle preservation with ACVR2B-Fc establishes that targeting myostatin-family ligands using ACVR2B-Fc or related molecules is an important and potent therapeutic avenue in cancer cachexia. Copyright 2009 Elsevier Inc. All rights reserved.

The immunomodulator decoy receptor 3 improves locomotor functional recovery after spinal cord injury.

PubMed

Chiu, Chuan-Wen; Huang, Wen-Hung; Lin, Shao-Ji; Tsai, May-Jywan; Ma, Hsu; Hsieh, Shie-Liang; Cheng, Henrich

2016-06-17

Spinal cord injury (SCI) causes loss of neurons and axons and results in motor and sensory function impairments. SCI elicits an inflammatory response and induces the infiltration of immune cells, predominantly macrophages, to the injured site. Decoy receptor 3 (DcR3), also known as tumor necrosis factor receptor superfamily member (TNFRSF)-6B, is a pleiotropic immunomodulator capable of inducing macrophage differentiation into the M2 phenotype and enhancing angiogenesis. Because M2 macrophages are crucial for the recovery of impaired motor functions, we ask whether DcR3 is beneficial for the functional recovery of locomotion in Sprague-Dawley (SD) rats after SCI. Contusion injury of the spinal cord was performed using a New York University impactor at the ninth thoracic vertebrae, followed by intrathecal injection of 15 μg recombinant protein comprising DcR3 (DcR3.Fc) in 5 μl of normal saline as the treatment, or 5 μl of normal saline as the control, into the injury epicenter. Functional recovery was evaluated using an open-field test weekly up to 6 weeks after injury. The cavity size and myelin sparing in the rostral-to-caudal region, including the epicenter of the injury, were then examined in SCI rats by histological staining. The expression of anti-inflammatory cytokines and the presence of M2 macrophages were determined by quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry at 7 day after SCI. Statistical analysis was performed using a two-tailed Student's t test. Intrathecal administration of DcR3.Fc significantly improved locomotor function and reduced secondary injury with a smaller wound cavity and increased myelin sparing at the lesion site. Compared with the control group, DcR3.Fc-treated rats had increased vascularization at the injury epicenter along with higher levels of interleukin (IL)-4 and IL-10 and lower level of IL-1β on DcR3.Fc-treated rats at day 7 after SCI. Moreover, higher levels of arginase I (Arg I) and CD206 (M2 macrophage markers) and RECA-1 (endothelial marker) were observed in the epicenter on day 7 after SCI by immunofluorescence staining. These results indicated that DcR3.Fc may promote the M2 macrophage infiltration and enhanced angiogenesis at the lesion site, thus preserving a greater amount of spinal cord tissues and enhancing functional recovery after SCI.

Cadherin-11 Regulation of Fibrosis through Modulation of Epithelial-to-Mesenchymal Transition: Implications for Pulmonary Fibrosis in Scleroderma

DTIC Science & Technology

2013-10-01

4A, TGFbeta decreased E- cadherin expression and increase Col1a1 expression in MLE12 cells. Soluble Cad11 Fc fusion protein inhibited EMT induced by...TGFbeta as noted my higher E-cadherin levels and a significant reduction in Col1a1 mRNA. In contrast, when Cad11 Fc fusion protein was immobilized...Fc fusion protein alone was able to induce Col1a1 expression at the 50 ug/ml concentration, although E-cadherin expression was also increased. In

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pennington, Luke F.; Tarchevskaya, Svetlana; Brigger, Daniel

Omalizumab is a widely used therapeutic anti-IgE antibody. Here we report the crystal structure of the omalizumab–Fab in complex with an IgE-Fc fragment. This structure reveals the mechanism of omalizumab-mediated inhibition of IgE interactions with both high- and low-affinity IgE receptors, and explains why omalizumab selectively binds free IgE. The structure of the complex also provides mechanistic insight into a class of disruptive IgE inhibitors that accelerate the dissociation of the high-affinity IgE receptor from IgE. We use this structural data to generate a mutant IgE-Fc fragment that is resistant to omalizumab binding. Treatment with this omalizumab-resistant IgE-Fc fragment, inmore » combination with omalizumab, promotes the exchange of cell-bound full-length IgE with omalizumab-resistant IgE-Fc fragments on human basophils. Furthermore, this combination treatment also blocks basophil activation more efficiently than either agent alone, providing a novel approach to probe regulatory mechanisms underlying IgE hypersensitivity with implications for therapeutic interventions.« less

Obeticholic acid raises LDL-cholesterol and reduces HDL-cholesterol in the Diet-Induced NASH (DIN) hamster model.

PubMed

Briand, François; Brousseau, Emmanuel; Quinsat, Marjolaine; Burcelin, Rémy; Sulpice, Thierry

2018-01-05

The use of rat and mouse models limits the translation to humans for developing novel drugs targeting nonalcoholic steatohepatitis (NASH). Obeticholic acid (OCA) illustrates this limitation since its dyslipidemic effect in humans cannot be observed in these rodents. Conversely, Golden Syrian hamsters have a lipoprotein metabolism mimicking human dyslipidemia since it does express the cholesteryl ester transfer protein (CETP). We therefore developed a Diet-Induced NASH (DIN) hamster model and evaluated the impact of OCA. Compared with chow fed controls, hamsters fed for 20 weeks with a free-choice (FC) diet, developed obesity, insulin resistance, dyslipidemia and NASH (microvesicular steatosis, inflammation, hepatocyte ballooning and perisinusoidal to bridging fibrosis). After 20 weeks of diet, FC fed hamsters were treated without or with obeticholic acid (15mg/kg/day) for 5 weeks. Although a non-significant trend towards higher dietary caloric intake was observed, OCA significantly lowered body weight after 5 weeks of treatment. OCA significantly increased CETP activity and LDL-C levels by 20% and 27%, and reduced HDL-C levels by 20%. OCA blunted hepatic gene expression of Cyp7a1 and Cyp8b1 and reduced fecal bile acids mass excretion by 64% (P < 0.05). Hamsters treated with OCA showed a trend towards higher scavenger receptor Class B type I (SR-BI) and lower LDL-receptor hepatic protein expression. OCA reduced NAS score for inflammation (P < 0.01) and total NAS score, although not significantly. Compared to mouse and rat models, the DIN hamster replicates benefits and side effects of OCA as observed in humans, and should be useful for evaluating novel drugs targeting NASH. Copyright © 2017 Elsevier B.V. All rights reserved.

IL-6 promotes an increase in human mast cell number and reactivity through suppression of SOCS3

PubMed Central

Desai, Avanti; Jung, Mi-Yeon; Olivera, Ana; Gilfillan, Alasdair M.; Prussin, Calman; Kirshenbaum, Arnold S.; Beaven, Michael A.; Metcalfe, Dean D.

2015-01-01

Background IL-6, which is reported to be elevated in association with mastocytosis, asthma and urticaria, is used in conjunction with stem cell factor (SCF) to generate human MCs (HuMCs) from progenitor (CD34+) cells. Despite these associations, the effects on, and mechanisms by which prolonged exposure to IL-6 alters HuMC number and function are not well understood. Objectives To study the effect of IL-6 on HuMC function, the mechanisms by which IL-6 exerts its effects, and the relationship of these findings to mastocytosis. Methods HuMCs were cultured in SCF with or without IL-6. The responses to FcεRI aggregation, and the expression of proteases and receptors including the soluble IL-6 receptor (sIL-6R) were then quantitated. Epigenetic changes in SOCS3 were determined using methylation specific PCR. Serum samples from healthy controls and patients with mastocytosis were assayed for IL-6, tryptase, and sIL-6R. Results IL-6 enhanced MC proliferation, maturation, and reactivity following FcεRI aggregation. IL-6 reduced expression of SOCS3, which correlated with methylation of the SOCS3 promoter, and increased expression and activation of STAT3. IL-6 also suppressed constitutive production of sIL-6R and serum levels of sIL-6R were similarly reduced in patients with mastocytosis. Conclusion IL-6 increases mast cell proliferation and formation of a more reactive phenotype enabled by suppressing proteolytic cleavage of sIL-6R from IL-6R and down regulation of the SOCS3 auto-inhibitory pathway. We suggest IL-6 blockade might ameliorate MC related symptoms and pathology in MC-related diseases associated with elevated IL-6 including mastocytosis. PMID:26774658

REVERSE SIGNALING BY GPI-LINKED MANDUCA EPHRIN REQUIRES A SRC FAMILY KINASE TO RESTRICT NEURONAL MIGRATION IN VIVO

PubMed Central

Coate, Thomas M.; Swanson, Tracy L.; Copenhaver, Philip F.

2011-01-01

Reverse signaling via GPI-linked Ephrins may help control cell proliferation and outgrowth within the nervous system, but the mechanisms underlying this process remain poorly understood. In the embryonic enteric nervous system (ENS) of the moth Manduca sexta, migratory neurons forming the enteric plexus (EP cells) express a single Ephrin ligand (GPI-linked MsEphrin), while adjacent midline cells that are inhibitory to migration express the cognate receptor (MsEph). Knocking down MsEph receptor expression in cultured embryos with antisense morpholino oligonucleotides allowed the EP cells to cross the midline inappropriately, consistent with the model that reverse signaling via MsEphrin mediates a repulsive response in the ENS. Src family kinases have been implicated in reverse signaling by type-A Ephrins in other contexts, and MsEphrin colocalizes with activated forms of endogenous Src in the leading processes of the EP cells. Pharmacological inhibition of Src within the developing ENS induced aberrant midline crossovers, similar to the effect of blocking MsEphrin reverse signaling. Hyperstimulating MsEphrin reverse signaling with MsEph-Fc fusion proteins induced the rapid activation of endogenous Src specifically within the EP cells, as assayed by Western blots of single embryonic gut explants and by whole-mount immunostaining of cultured embryos. In longer cultures, treatment with MsEph-Fc caused a global inhibition of EP cell migration and outgrowth, an effect that was prevented by inhibiting Src activation. These results support the model that MsEphrin reverse signaling induces the Src-dependent retraction of EP cell processes away from the enteric midline, thereby helping to confine the neurons to their appropriate pathways. PMID:19295147

Optimization of ELISA Conditions to Quantify Colorectal Cancer Antigen-Antibody Complex Protein (GA733-FcK) Expressed in Transgenic Plant

PubMed Central

Ahn, Junsik; Lee, Kyung Jin

2014-01-01

The purpose of this study is to optimize ELISA conditions to quantify the colorectal cancer antigen GA733 linked to the Fc antibody fragment fused to KDEL, an ER retention motif (GA733-FcK) expressed in transgenic plant. Variable conditions of capture antibody, blocking buffer, and detection antibody for ELISA were optimized with application of leaf extracts from transgenic plant expressing GA733-FcK. In detection antibody, anti-EpCAM/CD362 IgG recognizing the GA733 did not detect any GA733-FcK whereas anti-human Fc IgG recognizing the human Fc existed in plant leaf extracts. For blocking buffer conditions, 3% BSA buffer clearly blocked the plate, compared to the 5% skim-milk buffer. For capture antibody, monoclonal antibody (MAb) CO17-1A was applied to coat the plate with different amounts (1, 0.5, and 0.25 μg/well). Among the amounts of the capture antibody, 1 and 0.5 μg/well (capture antibody) showed similar absorbance, whereas 0.25 μg/well of the capture antibody showed significantly less absorbance. Taken together, the optimized conditions to quantify plant-derived GA733-FcK were 0.5 μg/well of MAb CO17-1A per well for the capture antibody, 3% BSA for blocking buffer, and anti-human Fc conjugated HRP. To confirm the optimized ELISA conditions, correlation analysis was conducted between the quantified amount of GA733-FcK in ELISA and its protein density values of different leaf samples in Western blot. The co-efficient value R2 between the ELISA quantified value and protein density was 0.85 (p<0.01), which indicates that the optimized ELISA conditions feasibly provides quantitative information of GA733-FcK expression in transgenic plant. PMID:24555929

PD-1 immunoreceptor inhibits B cell receptor-mediated signaling by recruiting src homology 2-domain-containing tyrosine phosphatase 2 to phosphotyrosine

PubMed Central

Okazaki, Taku; Maeda, Akito; Nishimura, Hiroyuki; Kurosaki, Tomohiro; Honjo, Tasuku

2001-01-01

PD-1 is an immunoreceptor that belongs to the immunoglobulin (Ig) superfamily and contains two tyrosine residues in the cytoplasmic region. Studies on PD-1-deficient mice have shown that PD-1 plays critical roles in establishment and/or maintenance of peripheral tolerance, but the mode of action is totally unknown. To study the molecular mechanism for negative regulation of lymphocytes through the PD-1 receptor, we generated chimeric molecules composed of the IgG Fc receptor type IIB (FcγRIIB) extracellular region and the PD-1 cytoplasmic region and expressed them in a B lymphoma cell line, IIA1.6. Coligation of the cytoplasmic region of PD-1 with the B cell receptor (BCR) in IIA1.6 transformants inhibited BCR-mediated growth retardation, Ca2+ mobilization, and tyrosine phosphorylation of effector molecules, including Igβ, Syk, phospholipase C-γ2 (PLCγ2), and ERK1/2, whereas phosphorylation of Lyn and Dok was not affected. Mutagenesis studies indicated that these inhibitory effects do not require the N-terminal tyrosine in the immunoreceptor tyrosine-based inhibitory motif-like sequence, but do require the other tyrosine residue in the C-terminal tail. This tyrosine was phosphorylated and recruited src homology 2-domain-containing tyrosine phosphatase 2 (SHP-2) on coligation of PD-1 with BCR. These results show that PD-1 can inhibit BCR signaling by recruiting SHP-2 to its phosphotyrosine and dephosphorylating key signal transducers of BCR signaling. PMID:11698646

Asymmetrical Fc Engineering Greatly Enhances Antibody-dependent Cellular Cytotoxicity (ADCC) Effector Function and Stability of the Modified Antibodies*

PubMed Central

Liu, Zhi; Gunasekaran, Kannan; Wang, Wei; Razinkov, Vladimir; Sekirov, Laura; Leng, Esther; Sweet, Heather; Foltz, Ian; Howard, Monique; Rousseau, Anne-Marie; Kozlosky, Carl; Fanslow, William; Yan, Wei

2014-01-01

Antibody-dependent cellular cytotoxicity (ADCC) is mediated through the engagement of the Fc segment of antibodies with Fcγ receptors (FcγRs) on immune cells upon binding of tumor or viral antigen. The co-crystal structure of FcγRIII in complex with Fc revealed that Fc binds to FcγRIII asymmetrically with two Fc chains contacting separate regions of the FcγRIII by utilizing different residues. To fully explore this asymmetrical nature of the Fc-FcγR interaction, we screened more than 9,000 individual clones in Fc heterodimer format in which different mutations were introduced at the same position of two Fc chains using a high throughput competition AlphaLISA® assay. To this end, we have identified a panel of novel Fc variants with significant binding improvement to FcγRIIIA (both Phe-158 and Val-158 allotypes), increased ADCC activity in vitro, and strong tumor growth inhibition in mice xenograft human tumor models. Compared with previously identified Fc variants in conventional IgG format, Fc heterodimers with asymmetrical mutations can achieve similar or superior potency in ADCC-mediated tumor cell killing and demonstrate improved stability in the CH2 domain. Fc heterodimers also allow more selectivity toward activating FcγRIIA than inhibitory FcγRIIB. Afucosylation of Fc variants further increases the affinity of Fc to FcγRIIIA, leading to much higher ADCC activity. The discovery of these Fc variants will potentially open up new opportunities of building the next generation of therapeutic antibodies with enhanced ADCC effector function for the treatment of cancers and infectious diseases. PMID:24311787

A Novel Dual Expression Platform for High Throughput Functional Screening of Phage Libraries in Product like Format.

PubMed

Xiao, Xiaodong; Chen, Yan; Mugabe, Sheila; Gao, Changshou; Tkaczyk, Christine; Mazor, Yariv; Pavlik, Peter; Wu, Herren; Dall'Acqua, William; Chowdhury, Partha Sarathi

2015-01-01

High throughput screenings of single chain Fv (scFv) antibody phage display libraries are currently done as soluble scFvs produced in E.coli. Due to endotoxin contaminations from bacterial cells these preparations cannot be reliably used in mammalian cell based assays. The monovalent nature and lack of Fc in soluble scFvs prevent functional assays that are dependent on target cross linking and/or Fc functions. A convenient approach is to convert scFvs into scFv.Fc fusion proteins and express them in mammalian cell lines for screening. This approach is low throughput and is only taken after primary screening of monovalent scFvs that are expressed in bacteria. There is no platform at present that combines the benefits of both bacterial and mammalian expression system for screening phage library output. We have, therefore, developed a novel dual expression vector, called pSplice, which can be used to express scFv.Fc fusion proteins both in E.coli and mammalian cell lines. The hallmark of the vector is an engineered intron which houses the bacterial promoter and signal peptide for expression and secretion of scFv.Fc in E.coli. When the vector is transfected into a mammalian cell line, the intron is efficiently spliced out resulting in a functional operon for expression and secretion of the scFv.Fc fusion protein into the culture medium. By applying basic knowledge of mammalian introns and splisosome, we designed this vector to enable screening of phage libraries in a product like format. Like IgG, the scFv.Fc fusion protein is bi-valent for the antigen and possesses Fc effector functions. Expression in E.coli maintains the speed of the bacterial expression platform and is used to triage clones based on binding and other assays that are not sensitive to endotoxin. Triaged clones are then expressed in a mammalian cell line without the need for any additional cloning steps. Conditioned media from the mammalian cell line containing the fusion proteins are then used for different types of cell based assays. Thus this system retains the speed of the current screening system for phage libraries and adds additional functionality to it.

Disentangling dynamic networks: Separated and joint expressions of functional connectivity patterns in time.

PubMed

Leonardi, Nora; Shirer, William R; Greicius, Michael D; Van De Ville, Dimitri

2014-12-01

Resting-state functional connectivity (FC) is highly variable across the duration of a scan. Groups of coevolving connections, or reproducible patterns of dynamic FC (dFC), have been revealed in fluctuating FC by applying unsupervised learning techniques. Based on results from k-means clustering and sliding-window correlations, it has recently been hypothesized that dFC may cycle through several discrete FC states. Alternatively, it has been proposed to represent dFC as a linear combination of multiple FC patterns using principal component analysis. As it is unclear whether sparse or nonsparse combinations of FC patterns are most appropriate, and as this affects their interpretation and use as markers of cognitive processing, the goal of our study was to evaluate the impact of sparsity by performing an empirical evaluation of simulated, task-based, and resting-state dFC. To this aim, we applied matrix factorizations subject to variable constraints in the temporal domain and studied both the reproducibility of ensuing representations of dFC and the expression of FC patterns over time. During subject-driven tasks, dFC was well described by alternating FC states in accordance with the nature of the data. The estimated FC patterns showed a rich structure with combinations of known functional networks enabling accurate identification of three different tasks. During rest, dFC was better described by multiple FC patterns that overlap. The executive control networks, which are critical for working memory, appeared grouped alternately with externally or internally oriented networks. These results suggest that combinations of FC patterns can provide a meaningful way to disentangle resting-state dFC. © 2014 The Authors. Human Brain Mapping published by Wiley Periodicals, Inc.

The leukocyte receptor CD84 inhibits Fc epsilon RI-mediated signaling through homophilic interaction in transfected RBL-2H3 cells.

PubMed

Oliver-Vila, Irene; Saborit-Villarroya, Ifigènia; Engel, Pablo; Martin, Margarita

2008-04-01

Signaling through the high-affinity receptor for immunoglobulin E (Fc epsilon RI) results in the coordinated activation of tyrosine kinases, thus leading to calcium mobilization, degranulation, and leukotriene and cytokine synthesis. Here, we show that CD84, a member of the CD150 family of leukocyte receptors, inhibits Fc epsilon RI-mediated mast cell degranulation in CD84-transfected rat basophilic leukaemia-2H3 mast cell line cells (RBL-2H3) through homophilic interaction. There was no reduction in overall protein phosphorylation following IgE triggering in CD84 RBL-2H3 cells. Indeed, phosphorylation of Dok-1 and c-Cbl increased in CD84 RBL-2H3, suggesting that inhibition is mediated by these molecules. MAP kinase phosphorylation (ERK1/2, JNK and p38) and cytokine synthesis were impaired in CD84 RBL-2H3. This inhibitory mechanism was independent of SAP and SHP-2 recruitment. Interestingly, CD84 mutants in tyrosines (Y279F and DeltaY324) reversed this inhibitory profile. These data suggest that CD84 may play a role in modulating Fc epsilon RI-mediated signaling in mast cells. Thus, CD84 could play a protective role against undesired allergic and inflammatory responses.

A Freeze Substitution Fixation-Based Gold Enlarging Technique for EM Studies of Endocytosed Nanogold-Labeled Molecules

PubMed Central

He, Wanzhong; Kivork, Christine; Machinani, Suman; Morphew, Mary K.; Gail, Anna M.; Tesar, Devin B.; Tiangco, Noreen E.; McIntosh, J. Richard; Bjorkman, Pamela J.

2007-01-01

We have developed methods to locate individual ligands that can be used for electron microscopy studies of dynamic events during endocytosis and subsequent intracellular trafficking. The methods are based on enlargement of 1.4 nm Nanogold attached to an endocytosed ligand. Nanogold, a small label that does not induce misdirection of ligand-receptor complexes, is ideal for labeling ligands endocytosed by live cells, but is too small to be routinely located in cells by electron microscopy. Traditional pre-embedding enhancement protocols to enlarge Nanogold are not compatible with high pressure freezing/freeze substitution fixation (HPF/FSF), the most accurate method to preserve ultrastructure and dynamic events during trafficking. We have developed an improved enhancement procedure for chemically-fixed samples that reduced autonucleation, and a new pre-embedding gold-enlarging technique for HPF/FSF samples that preserved contrast and ultrastructure and can be used for high-resolution tomography. We evaluated our methods using labeled Fc as a ligand for the neonatal Fc receptor. Attachment of Nanogold to Fc did not interfere with receptor binding or uptake, and gold-labeled Fc could be specifically enlarged to allow identification in 2D projections and in tomograms. These methods should be broadly applicable to many endocytosis and transcytosis studies. PMID:17723309

Glial cell line-derived neurotrophic factor (GDNF) induces neuritogenesis in the cochlear spiral ganglion via neural cell adhesion molecule (NCAM)

PubMed Central

Euteneuer, Sara; Yang, Kuo H.; Chavez, Eduardo; Leichtle, Anke; Loers, Gabriele; Olshansky, Adel; Pak, Kwang; Schachner, Melitta; Ryan, Allen F.

2013-01-01

Glial cell line-derived neurotrophic factor (GDNF) increases survival and neurite extension of spiral ganglion neurons (SGNs), the primary neurons of the auditory system, via yet unknown signaling mechanisms. In other cell types, signaling is achieved by the GPI-linked GDNF family receptor α1 (GFRα1) via recruitment of transmembrane receptors: Ret (re-arranged during transformation) and/or NCAM (neural cell adhesion molecule). Here we show that GDNF enhances neuritogenesis in organotypic cultures of spiral ganglia from 5-day-old rats and mice. Addition of GFRα1-Fc increases this effect. GDNF/GFRα1-Fc stimulation activates intracellular PI3K/Akt and MEK/Erk signaling cascades as detected by Western blot analysis of cultures prepared from rats at postnatal days 5 (P5, before the onset of hearing) and 20 (P20, after the onset of hearing). Both cascades mediate GDNF stimulation of neuritogenesis, since application of the Akt inhibitor Wortmannin or the Erk inhibitor U0126 abolished GDNF/GFRα1-Fc stimulated neuritogenesis in P5 rats. Since cultures of P5 NCAM-deficient mice failed to respond by neuritogenesis to GDNF/GFRα1-Fc, we conclude that NCAM serves as a receptor for GDNF signaling responsible for neuritogenesis in early postnatal spiral ganglion. PMID:23262364

Immune antibodies and helminth products promote CXCR2-dependent repair of parasite-induced injury

USDA-ARS?s Scientific Manuscript database

Helminth parasites cause massive damage when migrating through host tissues, thus making rapid tissue repair imperative to prevent bleeding and bacterial dissemination. We observed that mice lacking antibodies (AID-/-) or activating Fc receptors (FcR'-/-) displayed impaired intestinal repair followi...

Pathological reorganization of NMDA receptors subunits and postsynaptic protein PSD-95 distribution in Alzheimer's disease.

PubMed

Leuba, Genevieve; Vernay, Andre; Kraftsik, Rudolf; Tardif, Eric; Riederer, Beat Michel; Savioz, Armand

2014-01-01

In Alzheimer's disease (AD), synaptic alterations play a major role and are often correlated with cognitive changes. In order to better understand synaptic modifications, we compared alterations in NMDA receptors and postsynaptic protein PSD-95 expression in the entorhinal cortex (EC) and frontal cortex (FC; area 9) of AD and control brains. We combined immunohistochemical and image analysis methods to quantify on consecutive sections the distribution of PSD-95 and NMDA receptors GluN1, GluN2A and GluN2B in EC and FC from 25 AD and control cases. The density of stained receptors was analyzed using multivariate statistical methods to assess the effect of neurodegeneration. In both regions, the number of neuronal profiles immunostained for GluN1 receptors subunit and PSD-95 protein was significantly increased in AD compared to controls (3-6 fold), while the number of neuronal profiles stained for GluN2A and GluN2B receptors subunits was on the contrary decreased (3-4 fold). The increase in marked neuronal profiles was more prominent in a cortical band corresponding to layers 3 to 5 with large pyramidal cells. Neurons positive for GluN1 or PSD-95 staining were often found in the same localization on consecutive sections and they were also reactive for the anti-tau antibody AD2, indicating a neurodegenerative process. Differences in the density of immunoreactive puncta representing neuropile were not statistically significant. Altogether these data indicate that GluN1 and PSD-95 accumulate in the neuronal perikarya, but this is not the case for GluN2A and GluN2B, while the neuropile compartment is less subject to modifications. Thus, important variations in the pattern of distribution of the NMDA receptors subunits and PSD-95 represent a marker in AD and by impairing the neuronal network, contribute to functional deterioration.

Comparison of the antiviral potential among soluble forms of herpes simplex virus type-2 glycoprotein D receptors, herpes virus entry mediator A, nectin-1 and nectin-2, in transgenic mice.

PubMed

Fujimoto, Yoshikazu; Tomioka, Yukiko; Ozaki, Kinuyo; Takeda, Keiko; Suyama, Haruka; Yamamoto, Sayo; Takakuwa, Hiroki; Morimatsu, Masami; Uede, Toshimitsu; Ono, Etsuro

2017-07-01

Herpesvirus entry mediator A (HVEM), nectin-1 and nectin-2 are cellular receptors of glycoprotein D (gD) of herpes simplex virus type-2 (HSV-2). It has been shown that soluble forms of HSV gD receptors have the antiviral potential in cultured cells and transgenic mice. Here, to compare antiviral potential of soluble forms of HVEM, nectin-1 and nectin-2 against HSV-2 infections in vivo, transgenic mice expressing fusion proteins consisting of the entire ectodomain of HVEM, nectin-1 or nectin-2 and the Fc portion of human IgG (HVEMIg, nectin-1Ig and nectin-2Ig, respectively) were intraperitoneally infected with HSV-2. In the infection with 3 MLD50 (50 % mouse lethal dose), effective resistance was not observed in transgenic mice expressing nectin-2Ig. In a transgenic mouse line with high expression of nectin-1Ig, significant protection from the infection with 30 and 300 MLD50 was observed (survival rate of 100 and 71 %, respectively). On the other hand, transgenic mice expressing HVEMIg showed a complete resistance to the lethal infection even with 300 MLD50 (survival rate of 100 %). These results demonstrated that HVEMIg could exert effective antiviral activities against HSV-2 infections in vivo as compared with other soluble forms of HSV gD receptors.

Anti-Streptococcus IgM Antibodies Induce Repetitive Stereotyped Movements: Cell Activation and Co-Localization with Fcα/μ Receptors in the Striatum and Motor Cortex

PubMed Central

Zhang, Danhui; Patel, Ankur; Zhu, Youhua; Siegel, Allan; Zalcman, Steven S.

2012-01-01

Group A beta-hemolytic streptococcus (GABHS) infections are implicated in neuropsychiatric disorders associated with an increased expression of repetitive stereotyped movements. Anti-streptococcus IgG presumably cross-reacts with elements on basal ganglia cells, modifies their function, and triggers symptoms. IgM may play a unique role in precipitating behavioral disturbances since variations in cortico-striatal activity occur in temporal congruity with peak IgM titers during an orchestrated immune response. We discovered in Balb/c mice that single subcutaneous injections of mouse monoclonal IgM antibodies to Streptococcus Group A bacteria induce marked dose-dependent increases in repetitive stereotyped movements, including head bobbing, sniffing, and intense grooming. Effects were antibody- and antigen-specific: anti-streptococcus IgG stimulated ambulatory activity and vertical activity but not these stereotypies, while anti-KLH IgM reduced activity. We suggest that anti-streptococcus IgM and IgG play unique roles in provoking GABHS-related behavioral disturbances. Paralleling its stereotypy-inducing effects, anti-streptococcus IgM stimulated Fos-like immunoreactivity in regions linked to cortico-striatal projections involved in motor control, including subregions of the caudate, nucleus accumbens, and motor cortex. This is the first evidence that anti-streptococcus IgM antibodies induce in vivo functional changes in these structures. Moreover, there was a striking similarity in the distributions of anti-streptococcus IgM deposits and Fos-like immunoreactivity in these regions. Of further importance, Fcα/μ receptors, which bind IgM, were present- and co-localized with anti-streptococcus IgM in these structures. We suggest that anti-streptococcus IgM-induced alterations of cell activity reflect local actions of IgM that involve Fcα/μ receptors. These findings support the use of anti-streptococcus monoclonal antibody administration in Balb/c mice to model GABHS-related behavioral disturbances and identify underlying mechanisms. PMID:22285613

The incomplete anti-Rh antibody agglutination mechanism of trypsinized ORh+ red cells.

PubMed Central

Margni, R A; Leoni, J; Bazzurro, M

1977-01-01

The capacity for binding to trypsinized and non-trypsinized ORh+ red cells, of the IgG incomplete anti-Rh antibody and its F(ab')2 and Fc fragments has been investigated. An analysis has also been made of the capacity of non-specific human IgG, aggregated non-specific human IgG, human IgM (19S) and IgM (7S), and of fragments Fcgamma, Fcmu and Fc5mu to inhibit the agglutination of trypsinized ORh+ red cells by the IgG incomplete anti-Rh antibody. The results obtained indicate that these antibodies behave in a similar manner to that of nonprecipitating antibodies, and that the agglutination of trypsinized red cells seems to be a mixed reaction due to the interaction of an Fab fragment with its Rh antigenic determinant present in the surface of a red cell and the Fc of the same molecule with a receptor for Fc present in adjacent red cells. The trypsin treatment apparently results in the liberation of occult Fc receptors. It has also been demonstrated that in the agglutination of ORh+ red cells by IgG incomplete anti-Rh antibody in the presence of albumin, interaction must occur in some manner between the albumin and the Fc fragment since the F(ab')2 fragment does not give rise to agglutination under such conditions. Images Figure 1 PMID:415968

Identification and characterization of a Fc receptor activity on the Toxoplasma gondii tachyzoite.

PubMed

Vercammen, M; el Bouhdidi, A; Ben Messaoud, A; de Meuter, F; Bazin, H; Dubremetz, J F; Carlier, Y

1998-01-01

The Immunoglobulin (Ig) binding capacity of Toxoplasma gondii tachyzoites was investigated using fluorescence flow-cytometry analysis. Polyclonal mouse, human and rat immunoglobulins without specific anti-Toxoplasma activity bound to parasites in a concentration-dependent manner, saturating them at circulating serum concentrations. The immunoglobulin class and subclass specificity of binding was investigated using irrelevant monoclonal antibodies. IgM, IgA and IgG reacted with the parasite membrane. The attachment of mouse IgM to the parasite surface was hampered by mouse IgG1, IgG2a, IgG2b and IgG3. The binding of mouse IgG was proportionally reduced with increasing concentrations of mouse monoclonal IgM. The binding of murine immunoglobulin was diminished when in presence of human IgG. Purified Fc- but not Fab portions of immunoglobulins, fixed to parasites. Using labelled calibrated beads, the Ig binding capacity of parasites was estimated to be 6900 +/- 500 sites per tachyzoite. The Kd of the T. gondii Fc Receptor (FcR) activity was determined at 1.4 +/- 0.1 microM (mean +/- SEM). Such FcR activity was reduced by phospholipase C, trypsin and pronase treatment of the parasites. These data show a low affinity FcR activity on T. gondii tachyzoites which recognizes Ig of different species and isotypes and is likely supported by a glycosyl-phosphatidylinositol (GPI)-anchored surface protein of the parasite.

1,25-Dihydroxyvitamin D3 Suppresses TLR8 Expression and TLR8-Mediated Inflammatory Responses in Monocytes In Vitro and Experimental Autoimmune Encephalomyelitis In Vivo

DTIC Science & Technology

2013-03-14

was supported by funding from the Telemedicine and Advanced Technology Research Center (TATRC) at the US Army Medical Research and Materiel Command...instructions. Specific primers were synthesized by Integrated DNA Technologies (San Diego, CA) as shown in Table S1. Real-time PCR was performed with SYBR...PFA for 1 h at 4uC and then permeablized in a buffer containing 0.1% saponin . Nonspecific antibody binding to Fc receptors was blocked by incubation

Dendritic and tumor cell fusions transduced with adenovirus encoding CD40L eradicate B-cell lymphoma and induce a Th17-type response.

PubMed

Alvarez, E; Moga, E; Barquinero, J; Sierra, J; Briones, J

2010-04-01

Fusion of dendritic cells and tumor cells (FCs) constitutes a promising tool for generating an antitumor response because of their capacity to present tumor antigens and provide appropriate costimulatory signals. CD40-CD40L interaction has an important role in the maturation and survival of dendritic cells and provides critical help for T-cell priming. In this study, we sought to improve the effectiveness of FC vaccines in a murine model of B-cell lymphoma by engineering FCs to express CD40L by means of an adenovirus encoding CD40L (Adv-CD40L). Before transduction with Adv-CD40L, no CD40L expression was detected in FCs, DCs or tumor cells. The surface expression of CD40L in FC transduced with Adv-CD40L (FC-CD40L) ranged between 50 and 60%. FC-CD40L showed an enhanced expression of CD80, CD86, CD54 and MHC class II molecules and elicited a strong in vitro immune response in a syngeneic mixed lymphocyte reaction. Furthermore, FC-CD40L showed enhanced migration to secondary lymphoid organs. Splenocytes from mice treated with FC-CD40L had a dramatic increase in the production of IL-17, IL-6 and IFN-gamma, compared with controls. Treatment with the FC-CD40L vaccine induced regression of established tumors and increased survival. Our data demonstrate that FC transduced with Adv-CD40L enhances the antitumor effect of FC vaccines in a murine lymphoma model and this is associated with an increased Th17-type immune response.

Activin Decoy Receptor ActRIIB:Fc Lowers FSH and Therapeutically Restores Oocyte Yield, Prevents Oocyte Chromosome Misalignments and Spindle Aberrations, and Increases Fertility in Midlife Female SAMP8 Mice.

PubMed

Bernstein, Lori R; Mackenzie, Amelia C L; Lee, Se-Jin; Chaffin, Charles L; Merchenthaler, István

2016-03-01

Women of advanced maternal age (AMA) (age ≥ 35) have increased rates of infertility, miscarriages, and trisomic pregnancies. Collectively these conditions are called "egg infertility." A root cause of egg infertility is increased rates of oocyte aneuploidy with age. AMA women often have elevated endogenous FSH. Female senescence-accelerated mouse-prone-8 (SAMP8) has increased rates of oocyte spindle aberrations, diminished fertility, and rising endogenous FSH with age. We hypothesize that elevated FSH during the oocyte's FSH-responsive growth period is a cause of abnormalities in the meiotic spindle. We report that eggs from SAMP8 mice treated with equine chorionic gonadotropin (eCG) for the period of oocyte growth have increased chromosome and spindle misalignments. Activin is a molecule that raises FSH, and ActRIIB:Fc is an activin decoy receptor that binds and sequesters activin. We report that ActRIIB:Fc treatment of midlife SAMP8 mice for the duration of oocyte growth lowers FSH, prevents egg chromosome and spindle misalignments, and increases litter sizes. AMA patients can also have poor responsiveness to FSH stimulation. We report that although eCG lowers yields of viable oocytes, ActRIIB:Fc increases yields of viable oocytes. ActRIIB:Fc and eCG cotreatment markedly reduces yields of viable oocytes. These data are consistent with the hypothesis that elevated FSH contributes to egg aneuploidy, declining fertility, and poor ovarian response and that ActRIIB:Fc can prevent egg aneuploidy, increase fertility, and improve ovarian response. Future studies will continue to examine whether ActRIIB:Fc works via FSH and/or other pathways and whether ActRIIB:Fc can prevent aneuploidy, increase fertility, and improve stimulation responsiveness in AMA women.

Optimization and qualification of an Fc Array assay for assessments of antibodies against HIV-1/SIV.

PubMed

Brown, Eric P; Weiner, Joshua A; Lin, Shu; Natarajan, Harini; Normandin, Erica; Barouch, Dan H; Alter, Galit; Sarzotti-Kelsoe, Marcella; Ackerman, Margaret E

2018-04-01

The Fc Array is a multiplexed assay that assesses the Fc domain characteristics of antigen-specific antibodies with the potential to evaluate up to 500 antigen specificities simultaneously. Antigen-specific antibodies are captured on antigen-conjugated beads and their functional capacity is probed via an array of Fc-binding proteins including antibody subclassing reagents, Fcγ receptors, complement proteins, and lectins. Here we present the results of the optimization and formal qualification of the Fc Array, performed in compliance with Good Clinical Laboratory Practice (GCLP) guidelines. Assay conditions were optimized for performance and reproducibility, and the final version of the assay was then evaluated for specificity, accuracy, precision, limits of detection and quantitation, linearity, range and robustness. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Transmembrane domain dependent inhibitory function of FcγRIIB.

PubMed

Wang, Junyi; Li, Zongyu; Xu, Liling; Yang, Hengwen; Liu, Wanli

2018-03-01

FcγRIIB, the only inhibitory IgG Fc receptor, functions to suppress the hyper-activation of immune cells. Numerous studies have illustrated its inhibitory function through the ITIM motif in the cytoplasmic tail of FcγRIIB. However, later studies revealed that in addition to the ITIM, the transmembrane (TM) domain of FcγRIIB is also indispensable for its inhibitory function. Indeed, recent epidemiological studies revealed that a non-synonymous single nucleotide polymorphism (rs1050501) within the TM domain of FcγRIIB, responsible for the I232T substitution, is associated with the susceptibility to systemic lupus erythematosus (SLE). In this review, we will summarize these epidemiological and functional studies of FcγRIIB-I232T in the past few years, and will further discuss the mechanisms accounting for the functional loss of FcγRIIB-I232T. Our review will help the reader gain a deeper understanding of the importance of the TM domain in mediating the inhibitory function of FcγRIIB and may provide insights to a new therapeutic target for the associated diseases.

Granulocyte colony-stimulating factor enhances protection by anti-K1 capsular IgM antibody in murine Escherichia coli sepsis.

PubMed

Hustinx, W; Benaissa-Trouw, B; Van Kessel, K; Kuenen, J; Tavares, L; Kraaijeveld, K; Verhoef, J; Hoepelman, A

1997-12-01

Combined prophylactic treatment with recombinant murine granulocyte colony-stimulating factor (G-CSF) and a suboptimal dose of anti-K1 capsular IgM monoclonal antibody (MAb) significantly enhanced survival in an experimental mouse Escherichia coli O7:K1 peritonitis model compared with untreated animals (67% vs. 11% survival; P < 0.001) and with either treatment alone (67 vs. 29% and 27% survival, respectively; P < 0.01), which suggests synergism between these agents. Enhanced survival by combined treatment was associated with increased neutrophil counts in blood and peritoneal lavage fluid, lower systemic and higher levels of local tumour necrosis factor (TNF) and lower bacterial counts in blood cultures. Mouse neutrophils treated with G-CSF but not infected with E. coli showed enhanced phagocytic and respiratory burst capacity, down-regulation of L-selectin receptors and enhanced expression of Fc RII-III receptors but not of complement receptors.

Plant-produced anti-dengue virus monoclonal antibodies exhibit reduced antibody-dependent enhancement of infection activity.

PubMed

Dent, Matthew; Hurtado, Jonathan; Paul, Amber M; Sun, Haiyan; Lai, Huafang; Yang, Ming; Esqueda, Adrian; Bai, Fengwei; Steinkellner, Herta; Chen, Qiang

2016-12-01

The mAb E60 has the potential to be a desirable therapeutic molecule since it efficiently neutralizes all four serotypes of dengue virus (DENV). However, mammalian-cell-produced E60 exhibits antibody-dependent enhancement of infection (ADE) activity, rendering it inefficacious in vivo, and treated animals more susceptible to developing more severe diseases during secondary infection. In this study, we evaluated a plant-based expression system for the production of therapeutically suitable E60. The mAb was transiently expressed in Nicotiana benthamianaWT and a ∆XFT line, a glycosylation mutant lacking plant-specific N-glycan residues. The mAb was efficiently expressed and assembled in leaves and exhibited highly homogenous N-glycosylation profiles, i.e. GnGnXF3 or GnGn structures, depending on the expression host. Both E60 glycovariants demonstrated equivalent antigen-binding specificity and in vitro neutralization potency against DENV serotypes 2 and 4 compared with their mammalian-cell-produced counterpart. By contrast, plant-produced E60 exhibited reduced ADE activity in Fc gamma receptor expressing human cells. Our results suggest the ability of plant-produced antibodies to minimize ADE, which may lead to the development of safe and highly efficacious antibody-based therapeutics against DENV and other ADE-prone viral diseases. Our study provides so far unknown insight into the relationship between mAb N-glycosylation and ADE, which contributes to our understanding of how sugar moieties of antibodies modulate Fc-mediated functions and viral pathogenesis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szymanska, Ewelina; Korzeniowski, Marek; Raynal, Patrick

Receptor Fc{gamma}IIA (Fc{gamma}RIIA) associates with plasma membrane rafts upon activation to trigger signaling cascades leading to actin polymerization. We examined whether compartmentalization of PI(4,5)P{sub 2} and PI(4,5)P{sub 2}-synthesizing PIP5-kinase I{alpha} to rafts contributes to Fc{gamma}RIIA signaling. A fraction of PIP5-kinase I{alpha} was detected in raft-originating detergent-resistant membranes (DRM) isolated from U937 monocytes and other cells. The DRM of U937 monocytes contained also a major fraction of PI(4,5)P{sub 2}. PIP5-kinase I{alpha} bound PI(4,5)P{sub 2}, and depletion of the lipid displaced PIP5-kinase I{alpha} from the DRM. Activation of Fc{gamma}RIIA in BHK transfectants led to recruitment of the kinase to the plasma membranemore » and enrichment of DRM in PI(4,5)P{sub 2}. Immunofluorescence studies revealed that in resting cells the kinase was associated with the plasma membrane, cytoplasmic vesicles and the nucleus. After Fc{gamma}RIIA activation, PIP5-kinase I{alpha} and PI(4,5)P{sub 2} co-localized transiently with the activated receptor at distinct cellular locations. Immunoelectron microscopy studies revealed that PIP5-kinase I{alpha} and PI(4,5)P{sub 2} were present at the edges of electron-dense assemblies containing activated Fc{gamma}RIIA in their core. The data suggest that activation of Fc{gamma}RIIA leads to membrane rafts coalescing into signaling platforms containing PIP5-kinase I{alpha} and PI(4,5)P{sub 2}.« less

Inhibitory effect of carotenoids on the degranulation of mast cells via suppression of antigen-induced aggregation of high affinity IgE receptors.

PubMed

Sakai, Shota; Sugawara, Tatsuya; Matsubara, Kiminori; Hirata, Takashi

2009-10-09

Carotenoids have been demonstrated to possess antioxidative and anti-inflammatory effects. However, there is no report that the effects of carotenoids on degranulation of mast cell is critical for type I allergy. In this study, we focused on the effect of carotenoids on antigen-induced degranulation of mast cells. Fucoxanthin, astaxanthin, zeaxanthin, and beta-carotene significantly inhibited the antigen-induced release of beta-hexosaminidase in rat basophilic leukemia 2H3 cells and mouse bone marrow-derived mast cells. Those carotenoids also inhibited antigen-induced aggregation of the high affinity IgE receptor (Fc epsilonRI), which is the most upstream of the degranulating signals of mast cells. Furthermore, carotenoids inhibited Fc epsilonRI-mediated intracellular signaling, such as phosphorylation of Lyn kinase and Fyn kinase. It suggests that the inhibitory effect of carotenoids on the degranulation of mast cells were mainly due to suppressing the aggregation of Fc epsilonRI followed by intracellular signaling. In addition, those carotenoids inhibited antigen-induced translocation of Fc epsilonRI to lipid rafts, which are known as platforms of the aggregation of Fc epsilonRI. We assume that carotenoids may modulate the function of lipid rafts and inhibit the translocation of Fc epsilonRI to lipid rafts. This is the first report that focused on the aggregation of Fc epsilonRI to investigate the mechanism of the inhibitory effects on the degranulation of mast cells and evaluated the functional activity of carotenoids associated with lipid rafts.

Inhibitory Effect of Carotenoids on the Degranulation of Mast Cells via Suppression of Antigen-induced Aggregation of High Affinity IgE Receptors*

PubMed Central

Sakai, Shota; Sugawara, Tatsuya; Matsubara, Kiminori; Hirata, Takashi

2009-01-01

Carotenoids have been demonstrated to possess antioxidative and anti-inflammatory effects. However, there is no report that the effects of carotenoids on degranulation of mast cell is critical for type I allergy. In this study, we focused on the effect of carotenoids on antigen-induced degranulation of mast cells. Fucoxanthin, astaxanthin, zeaxanthin, and β-carotene significantly inhibited the antigen-induced release of β-hexosaminidase in rat basophilic leukemia 2H3 cells and mouse bone marrow-derived mast cells. Those carotenoids also inhibited antigen-induced aggregation of the high affinity IgE receptor (FcϵRI), which is the most upstream of the degranulating signals of mast cells. Furthermore, carotenoids inhibited FcϵRI-mediated intracellular signaling, such as phosphorylation of Lyn kinase and Fyn kinase. It suggests that the inhibitory effect of carotenoids on the degranulation of mast cells were mainly due to suppressing the aggregation of FcϵRI followed by intracellular signaling. In addition, those carotenoids inhibited antigen-induced translocation of FcϵRI to lipid rafts, which are known as platforms of the aggregation of FcϵRI. We assume that carotenoids may modulate the function of lipid rafts and inhibit the translocation of FcϵRI to lipid rafts. This is the first report that focused on the aggregation of FcϵRI to investigate the mechanism of the inhibitory effects on the degranulation of mast cells and evaluated the functional activity of carotenoids associated with lipid rafts. PMID:19700409

Fc-dependent depletion of tumor-infiltrating regulatory T cells co-defines the efficacy of anti–CTLA-4 therapy against melanoma

PubMed Central

Simpson, Tyler R.; Li, Fubin; Montalvo-Ortiz, Welby; Sepulveda, Manuel A.; Bergerhoff, Katharina; Arce, Frederick; Roddie, Claire; Henry, Jake Y.; Yagita, Hideo; Wolchok, Jedd D.; Peggs, Karl S.; Ravetch, Jeffrey V.

2013-01-01

Treatment with monoclonal antibody specific for cytotoxic T lymphocyte–associated antigen 4 (CTLA-4), an inhibitory receptor expressed by T lymphocytes, has emerged as an effective therapy for the treatment of metastatic melanoma. Although subject to debate, current models favor a mechanism of activity involving blockade of the inhibitory activity of CTLA-4 on both effector (T eff) and regulatory (T reg) T cells, resulting in enhanced antitumor effector T cell activity capable of inducing tumor regression. We demonstrate, however, that the activity of anti–CTLA-4 antibody on the T reg cell compartment is mediated via selective depletion of T reg cells within tumor lesions. Importantly, T reg cell depletion is dependent on the presence of Fcγ receptor–expressing macrophages within the tumor microenvironment, indicating that T reg cells are depleted in trans in a context-dependent manner. Our results reveal further mechanistic insight into the activity of anti-CTLA-4–based cancer immunotherapy, and illustrate the importance of specific features of the local tumor environment on the final outcome of antibody-based immunomodulatory therapies. PMID:23897981

Generation of Gene-Engineered Chimeric DNA Molecules for Specific Therapy of Autoimmune Diseases

PubMed Central

Gesheva, Vera; Szekeres, Zsuzsanna; Mihaylova, Nikolina; Dimitrova, Iliyana; Nikolova, Maria; Erdei, Anna; Prechl, Jozsef

2012-01-01

Abstract Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the development of self-reactive B and T cells and autoantibody production. In particular, double-stranded DNA-specific B cells play an important role in lupus progression, and their selective elimination is a reasonable approach for effective therapy of SLE. DNA-based vaccines aim at the induction of immune response against the vector-encoded antigen. Here, we are exploring, as a new DNA-based therapy of SLE, a chimeric DNA molecule encoding a DNA-mimotope peptide, and the Fv but not the immunogenic Fc fragment of an FcγRIIb-specific monoclonal antibody. This DNA construct was inserted in the expression vector pNut and used as a naked DNA vaccine in a mouse model of lupus. The chimeric DNA molecule can be expressed in eukaryotic cells and cross-links cell surface receptors on DNA-specific B cells, delivering an inhibitory intracellular signal. Intramuscular administration of the recombinant DNA molecule to lupus-prone MRL/lpr mice prevented increase in IgG anti-DNA antibodies and was associated with a low degree of proteinuria, modulation of cytokine profile, and suppression of lupus nephritis. PMID:23075110

Systemic Sclerosis Patients Present Alterations in the Expression of Molecules Involved in B-Cell Regulation

PubMed Central

Soto, Lilian; Ferrier, Ashley; Aravena, Octavio; Fonseca, Elianet; Berendsen, Jorge; Biere, Andrea; Bueno, Daniel; Ramos, Verónica; Aguillón, Juan Carlos; Catalán, Diego

2015-01-01

The activation threshold of B cells is tightly regulated by an array of inhibitory and activator receptors in such a way that disturbances in their expression can lead to the appearance of autoimmunity. The aim of this study was to evaluate the expression of activating and inhibitory molecules involved in the modulation of B cell functions in transitional, naive, and memory B-cell subpopulations from systemic sclerosis patients. To achieve this, blood samples were drawn from 31 systemic sclerosis patients and 53 healthy individuals. Surface expression of CD86, MHC II, CD19, CD21, CD40, CD22, Siglec 10, CD35, and FcγRIIB was determined by flow cytometry. IL-10 production was evaluated by intracellular flow cytometry from isolated B cells. Soluble IL-6 and IL-10 levels were measured by ELISA from supernatants of stimulated B cells. Systemic sclerosis patients exhibit an increased frequency of transitional and naive B cells related to memory B cells compared with healthy controls. Transitional and naive B cells from patients express higher levels of CD86 and FcγRIIB than healthy donors. Also, B cells from patients show high expression of CD19 and CD40, whereas memory cells from systemic sclerosis patients show reduced expression of CD35. CD19 and CD35 expression levels associate with different autoantibody profiles. IL-10+ B cells and secreted levels of IL-10 were markedly reduced in patients. In conclusion, systemic sclerosis patients show alterations in the expression of molecules involved in B-cell regulation. These abnormalities may be determinant in the B-cell hyperactivation observed in systemic sclerosis. PMID:26483788

Advances in medical education and practice: student perceptions of the flipped classroom

PubMed Central

Ramnanan, Christopher J; Pound, Lynley D

2017-01-01

The flipped classroom (FC) approach to teaching has been increasingly employed in undergraduate medical education in recent years. In FC applications, students are first exposed to content via online resources. Subsequent face-to-face class time can then be devoted to student-centered activities that promote active learning. Although the FC has been well received by students in other contexts, the perceptions of medical students regarding this innovation are unclear. This review serves as an early exploration into medical student perceptions of benefits and limitations of the FC. Medical students have generally expressed strong appreciation for the pre-class preparation activities (especially when facilitated by concise, readily accessed online tools) as well as for interactive, engaging small group classroom activities. Some students have expressed concerns with the FC and noted that suboptimal student preparation and insufficient direction and structure during active learning sessions may limit the student-centered benefits. Although students generally perceive that FC approaches can improve their learning and knowledge, this has not been conclusively shown via performances on assessment tools, which may be related to caveats with the assessment tools used. In any case, lifelong self-directed learning skills are perceived by medical students to be enhanced by the FC. In conclusion, medical students have generally expressed strong satisfaction with early applications of the FC to undergraduate medical education, and generally prefer this method to lecture-based instruction. PMID:28144171

Advances in medical education and practice: student perceptions of the flipped classroom.

PubMed

Ramnanan, Christopher J; Pound, Lynley D

2017-01-01

The flipped classroom (FC) approach to teaching has been increasingly employed in undergraduate medical education in recent years. In FC applications, students are first exposed to content via online resources. Subsequent face-to-face class time can then be devoted to student-centered activities that promote active learning. Although the FC has been well received by students in other contexts, the perceptions of medical students regarding this innovation are unclear. This review serves as an early exploration into medical student perceptions of benefits and limitations of the FC. Medical students have generally expressed strong appreciation for the pre-class preparation activities (especially when facilitated by concise, readily accessed online tools) as well as for interactive, engaging small group classroom activities. Some students have expressed concerns with the FC and noted that suboptimal student preparation and insufficient direction and structure during active learning sessions may limit the student-centered benefits. Although students generally perceive that FC approaches can improve their learning and knowledge, this has not been conclusively shown via performances on assessment tools, which may be related to caveats with the assessment tools used. In any case, lifelong self-directed learning skills are perceived by medical students to be enhanced by the FC. In conclusion, medical students have generally expressed strong satisfaction with early applications of the FC to undergraduate medical education, and generally prefer this method to lecture-based instruction.

Macrophage-mediated trogocytosis leads to death of antibody-opsonized tumor cells

PubMed Central

Velmurugan, Ramraj; Challa, Dilip K.; Ram, Sripad; Ober, Raimund J.; Ward, E. Sally

2016-01-01

Understanding the complex behavior of effector cells such as monocytes or macrophages in regulating cancerous growth is of central importance for cancer immunotherapy. Earlier studies using CD20-specific antibodies have demonstrated that the Fcγ receptor (FcγR)-mediated transfer of the targeted receptors from tumor cells to these effector cells through trogocytosis can enable escape from antibody therapy, leading to the viewpoint that this process is pro-tumorigenic. In the current study we demonstrate that persistent trogocytic attack results in the killing of HER2-overexpressing breast cancer cells. Further, antibody engineering to increase FcγR interactions enhances this tumoricidal activity. These studies extend the complex repertoire of activities of macrophages to trogocytic-mediated cell death of HER2-overexpressing target cells and have implications for the development of effective antibody-based therapies. PMID:27226489

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wurzburg, Beth A.; Tarchevskaya, Svetlana S.; Jardetzky, Theodore S.

CD23, the low-affinity receptor for IgE (Fc{var_epsilon}RII), regulates IgE synthesis and also mediates IgE-dependent antigen transport and processing. CD23 is a unique Fc receptor belonging to the C-type lectin-like domain superfamily and binds IgE in an unusual, non-lectin-like manner, requiring calcium but not carbohydrate. We have solved the high-resolution crystal structures of the human CD23 lectin domain in the presence and absence of Ca{sup 2+}. The crystal structures differ significantly from a previously determined NMR structure and show that calcium binding occurs at the principal binding site, but not at an auxiliary site that appears to be absent in humanmore » CD23. Conformational differences between the apo and Ca{sup 2+} bound structures suggest how IgE-Fc binding can be both calcium-dependent and carbohydrate-independent.« less

Fc Gamma Receptor 3A Polymorphism and Risk for HIV-Associated Cryptococcal Disease

PubMed Central

Rohatgi, Soma; Gohil, Shruti; Kuniholm, Mark H.; Schultz, Hannah; Dufaud, Chad; Armour, Kathryn L.; Badri, Sheila; Mailliard, Robbie B.; Pirofski, Liise-anne

2013-01-01

ABSTRACT Cryptococcus neoformans is one of the most common causes of fungal disease in HIV-infected persons, but not all of those who are infected develop cryptococcal disease (CD). Although CD4+ T cell deficiency is a risk factor for HIV-associated CD, polymorphisms of phagocytic Fc gamma receptors (FCGRs) have been linked to CD risk in HIV-uninfected persons. To investigate associations between FCGR2A 131 H/R and FCGR3A 158 F/V polymorphisms and CD risk in HIV-infected persons, we performed PCR-based genotyping on banked samples from 164 men enrolled in the Multicenter AIDS Cohort Study (MACS): 55 who were HIV infected and developed CD and a matched control group of 54 who were HIV infected and 55 who were HIV uninfected. Using additive and allelic statistical models for analysis, the high-affinity FCGR3A 158V allele was significantly associated with CD status after adjusting for race/ethnicity (odds ratio [OR], 2.1; P = 0.005), as was the FCGR3A 158 VV homozygous genotype after adjusting for race/ethnicity, rate of CD4+ T cell decline, and nadir CD4+ T cell count (OR, 21; P = 0.005). No associations between CD and FCGR2A 131 H/R polymorphism were identified. In binding studies, human IgG (hIgG)-C. neoformans complexes exhibited more binding to CHO-K1 cells expressing FCGR3A 158V than to those expressing FCGR3A 158F, and in cytotoxicity assays, natural killer (NK) cells expressing FCGR3A 158V induced more C. neoformans-infected monocyte cytotoxicity than those expressing FCGR3A 158F. Together, these results show an association between the FCGR3A 158V allele and risk for HIV-associated CD and suggest that this polymorphism could promote C. neoformans pathogenesis via increased binding of C. neoformans immune complexes, resulting in increased phagocyte cargo and/or immune activation. PMID:23982074

Rab17 Regulates Membrane Trafficking through Apical Recycling Endosomes in Polarized Epithelial Cells

PubMed Central

Zacchi, Paola; Stenmark, Harald; Parton, Robert G.; Orioli, Donata; Lim, Filip; Giner, Angelika; Mellman, Ira; Zerial, Marino; Murphy, Carol

1998-01-01

A key feature of polarized epithelial cells is the ability to maintain the specific biochemical composition of the apical and basolateral plasma membrane domains while selectively allowing transport of proteins and lipids from one pole to the opposite by transcytosis. The small GTPase, rab17, a member of the rab family of regulators of intracellular transport, is specifically induced during cell polarization in the developing kidney. We here examined its intracellular distribution and function in both nonpolarized and polarized cells. By confocal immunofluorescence microscopy, rab17 colocalized with internalized transferrin in the perinuclear recycling endosome of BHK-21 cells. In polarized Eph4 cells, rab17 associated with the apical recycling endosome that has been implicated in recycling and transcytosis. The localization of rab17, therefore, strengthens the proposed homology between this compartment and the recycling endosome of nonpolarized cells. Basolateral to apical transport of two membrane-bound markers, the transferrin receptor and the FcLR 5-27 chimeric receptor, was specifically increased in Eph4 cells expressing rab17 mutants defective in either GTP binding or hydrolysis. Furthermore, the mutant proteins stimulated apical recycling of FcLR 5-27. These results support a role for rab17 in regulating traffic through the apical recycling endosome, suggesting a function in polarized sorting in epithelial cells. PMID:9490718

IgG Fc variant cross-reactivity between human and rhesus macaque FcγRs

PubMed Central

Boesch, Austin W.; Miles, Adam R.; Chan, Ying N.; Osei-Owusu, Nana Y.; Ackerman, Margaret E.

2017-01-01

ABSTRACT Non-human primate (NHP) studies are often an essential component of antibody development efforts before human trials. Because the efficacy or toxicity of candidate antibodies may depend on their interactions with Fcγ receptors (FcγR) and their resulting ability to induce FcγR-mediated effector functions such as antibody-dependent cell-meditated cytotoxicity and phagocytosis (ADCP), the evaluation of human IgG variants with modulated affinity toward human FcγR is becoming more prevalent in both infectious disease and oncology studies in NHP. Reliable translation of these results necessitates analysis of the cross-reactivity of these human Fc variants with NHP FcγR. We report evaluation of the binding affinities of a panel of human IgG subclasses, Fc amino acid point mutants and Fc glycosylation variants against the common allotypes of human and rhesus macaque FcγR by applying a high-throughput array-based surface plasmon resonance platform. The resulting data indicate that amino acid variation present in rhesus FcγRs can result in disrupted, matched, or even increased affinity of IgG Fc variants compared with human FcγR orthologs. These observations emphasize the importance of evaluating species cross-reactivity and developing an understanding of the potential limitations or suitability of representative in vitro and in vivo models before human clinical studies when either efficacy or toxicity may be associated with FcγR engagement. PMID:28055295

Spontaneous food allergy in Was-/- mice occurs independent of FcεRI-mediated mast cell activation.

PubMed

Lexmond, W S; Goettel, J A; Sallis, B F; McCann, K; Rings, E H H M; Jensen-Jarolim, E; Nurko, S; Snapper, S B; Fiebiger, E

2017-12-01

Food allergies are a growing health problem, and the development of therapies that prevent disease onset is limited by the lack of adjuvant-free experimental animal models. We compared allergic sensitization in patients with food allergy or Wiskott-Aldrich syndrome (WAS) and defined whether spontaneous disease in Was -/- mice recapitulates the pathology of a conventional disease model and/or human food allergy. Comparative ImmunoCAP ISAC microarray was performed in patients with food allergy or WAS. Spontaneous food allergy in Was -/- mice was compared to an adjuvant-based model in wild-type mice (WT-OVA/alum). Intestinal and systemic anaphylaxis was assessed, and the role of the high-affinity IgE Fc receptor (FcεRI) in allergic sensitization was evaluated using Was -/- Fcer1a -/- mice. Polysensitization to food was detected in both WAS and food-allergic patients which was recapitulated in the Was -/- model. Oral administration of ovalbumin (OVA) in Was -/- mice induced low titers of OVA-specific IgE compared to the WT-OVA/alum model. Irrespectively, 79% of Was -/- mice developed allergic diarrhea following oral OVA challenge. Systemic anaphylaxis occurred in Was -/- mice (95%) with a mortality rate >50%. Spontaneous sensitization and intestinal allergy occurred independent of FcεRI expression on mast cells (MCs) and basophils. Was -/- mice provide a model of food allergy with the advantage of mimicking polysensitization and low food-antigen IgE titers as observed in humans with clinical food allergy. This model will facilitate studies on aberrant immune responses during spontaneous disease development. Our results imply that therapeutic targeting of the IgE/FcεRI activation cascade will not affect sensitization to food. © 2017 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

Circulating CD21low B cells in common variable immunodeficiency resemble tissue homing, innate-like B cells

PubMed Central

Rakhmanov, Mirzokhid; Keller, Baerbel; Gutenberger, Sylvia; Foerster, Christian; Hoenig, Manfred; Driessen, Gertjan; van der Burg, Mirjam; van Dongen, Jacques J.; Wiech, Elisabeth; Visentini, Marcella; Quinti, Isabella; Prasse, Antje; Voelxen, Nadine; Salzer, Ulrich; Goldacker, Sigune; Fisch, Paul; Eibel, Hermann; Schwarz, Klaus; Peter, Hans-Hartmut; Warnatz, Klaus

2009-01-01

The homeostasis of circulating B cell subsets in the peripheral blood of healthy adults is well regulated, but in disease it can be severely disturbed. Thus, a subgroup of patients with common variable immunodeficiency (CVID) presents with an extraordinary expansion of an unusual B cell population characterized by the low expression of CD21. CD21low B cells are polyclonal, unmutated IgM+IgD+ B cells but carry a highly distinct gene expression profile which differs from conventional naïve B cells. Interestingly, while clearly not representing a memory population, they do share several features with the recently defined memory-like tissue, Fc receptor-like 4 positive B cell population in the tonsils of healthy donors. CD21low B cells show signs of previous activation and proliferation in vivo, while exhibiting defective calcium signaling and poor proliferation in response to B cell receptor stimulation. CD21low B cells express decreased amounts of homeostatic but increased levels of inflammatory chemokine receptors. This might explain their preferential homing to peripheral tissues like the bronchoalveolar space of CVID or the synovium of rheumatoid arthritis patients. Therefore, as a result of the close resemblance to the gene expression profile, phenotype, function and preferential tissue homing of murine B1 B cells, we suggest that CD21low B cells represent a human innate-like B cell population. PMID:19666505

Structural basis of omalizumab therapy and omalizumab-mediated IgE exchange

DOE PAGES

Pennington, Luke F.; Tarchevskaya, Svetlana; Brigger, Daniel; ...

2016-05-19

Omalizumab is a widely used therapeutic anti-IgE antibody. Here we report the crystal structure of the omalizumab–Fab in complex with an IgE-Fc fragment. This structure reveals the mechanism of omalizumab-mediated inhibition of IgE interactions with both high- and low-affinity IgE receptors, and explains why omalizumab selectively binds free IgE. The structure of the complex also provides mechanistic insight into a class of disruptive IgE inhibitors that accelerate the dissociation of the high-affinity IgE receptor from IgE. We use this structural data to generate a mutant IgE-Fc fragment that is resistant to omalizumab binding. Treatment with this omalizumab-resistant IgE-Fc fragment, inmore » combination with omalizumab, promotes the exchange of cell-bound full-length IgE with omalizumab-resistant IgE-Fc fragments on human basophils. Furthermore, this combination treatment also blocks basophil activation more efficiently than either agent alone, providing a novel approach to probe regulatory mechanisms underlying IgE hypersensitivity with implications for therapeutic interventions.« less

Age-related guanine nucleotide exchange factor, mouse Zizimin2, induces filopodia in bone marrow-derived dendritic cells

PubMed Central

2012-01-01

Background We recently isolated and identified Zizimin2 as a functional factor that is highly expressed in murine splenic germinal center B cells after immunization with T-cell-dependent antigen. Zizimin2 was revealed to be a new family member of Dock (dedicator of cytokinesis), Dock11, which is the guanine nucleotide exchange factor for Cdc42, a low-molecular-weight GTPase. However, the molecular function of Zizimin2 in acquired immunity has not been elucidated. Results In this study, we show that the protein expression of Zizimin2, which is also restricted to lymphoid tissues and lymphocytes, is reduced in aged mice. Over-expression of full-length Zizimin2 induced filopodial formation in 293T cells, whereas expression of CZH2 domain inhibited it. Stimulation of Fcγ receptor and Toll-like receptor 4 triggered Zizimin2 up-regulation and Cdc42 activation in bone marrow-derived dendritic cells. Conclusions These data suggest that Zizimin2 is an immune-related and age-regulated guanine nucleotide exchange factor, which facilitates filopodial formation through activation of Cdc42, which results in activation of cell migration. PMID:22494997

[Eukaryotic Expression and Immunogenic Research of Recombination Ebola Virus Membrane Protein Gp-Fc].

PubMed

Zhang, Xiaoguang; Yang, Ren; Wang, Jiao; Wang, Xuan; Hou, Mieling; An, Lina; Zhu, Ying; Cao, Yuxi; Zeng, Yi

2016-01-01

We used 293 cells to express the recombinant membrane protein of the Ebola virus. Then, the immunogenicity of the recombinant protein was studied by immunized BALB/c mice. According to the codon use frequency of humans, the gene encoding the extracellular domain of the Ebola virus membrane protein was optimized, synthesized, and inserted into the eukaryotic expression plasmid pXG-Fc to construct the human IgG Fc and Ebola GP fusion protein expression plasmid pXG-modGP-Fc. To achieve expression, the fusion protein expression vector was transfected into high-density 293 cells using transient transfection technology. The recombinant protein was purified by protein A affinity chromatography. BALB/c mice were immunized with the purified fusion protein, and serum antibody titers evaluated by an indirect enzyme-linked immunosorbent assay (ELISA). Purification and analyses of the protein revealed that the eukaryotic expression vector could express the recombinant protein GP-Fc effectively, and that the recombinant protein in the supernatant of the cell culture was present as a dimer. After immunization with the purified recombinant protein, a high titer of antigen-specific IgG could be detected in the serum of immunized mice by indirect ELISA, showing that the recombinant protein had good immunogenicity. These data suggest that we obtained a recombinant protein with good immunogenicity. Our study is the basis for development of a vaccine against the Ebola virus and for screening of monoclonal antibodies.

Putative suppressing effect of IgG Fc-conjugated haemagglutinin (HA) stalk of influenza virus H7N9 on the neutralizing immunogenicity of Fc-conjugated HA head: implication for rational design of HA-based influenza vaccines.

PubMed

He, B; Xia, S; Yu, F; Fu, Y; Li, W; Wang, Q; Lu, L; Jiang, S

2016-02-01

The emergence of influenza A H7N9 in infection has posed a great threat to public health globally. Poor immunogenicity of H7N9 haemagglutinin (HA) is a major obstacle to the development of an effective H7N9 vaccine. Here, we found that the vaccine containing the H7HA head conjugated with IgG Fc (Hd-Fc) induced strong neutralizing antibody responses and protection against H7N9 infection, whilst the Fc-conjugated H7HA stalk (St-Fc)-based vaccine could not induce neutralizing antibodies, although the St-Fc-immunized mice were partially protected. The vaccines containing the full-length extracellular domain of HA conjugated with Fc and the mixture of Hd-Fc plus St-Fc induced significantly lower neutralizing antibody and haemagglutination inhibition titres than the Hd-Fc-based vaccine. These results suggest that the St-Fc may have inhibitory effects on the neutralizing immunogenicity of Hd-Fc. Therefore, the neutralizing domain(s), such as the receptor-binding domain, in the HA head should be kept and the non-neutralizing domain(s) in the HA stalk with the ability to potentially suppress the neutralizing immunogenicity of HA head should be removed from Fc-conjugated HA-based influenza vaccines to increase the neutralizing antibody response.

Expression of FcFT1, a FLOWERING LOCUS T-like gene, is regulated by light and associated with inflorescence differentiation in fig (Ficus carica L.).

PubMed

Ikegami, Hidetoshi; Nogata, Hitoshi; Inoue, Yoshiaki; Himeno, Shuichi; Yakushiji, Hiroshi; Hirata, Chiharu; Hirashima, Keita; Mori, Masashi; Awamura, Mitsuo; Nakahara, Takao

2013-12-16

Because the floral induction occurs in many plants when specific environmental conditions are satisfied, most plants bloom and bear fruit during the same season each year. In fig, by contrast, the time interval during which inflorescence (flower bud, fruit) differentiation occurs corresponds to the shoot elongation period. Fig trees thus differ from many species in their reproductive growth characteristics. To date, however, the molecular mechanisms underlying this unorthodox physiology of floral induction and fruit setting in fig trees have not been elucidated. We isolated a FLOWERING LOCUS T (FT)-like gene from fig and examined its function, characteristics, and expression patterns. The isolated gene, F. carica FT (FcFT1), is single copy in fig and shows the highest similarity at the amino acid level (93.1%) to apple MdFT2. We sequenced its upstream region (1,644 bp) and identified many light-responsive elements. FcFT1 was mainly expressed in leaves and induced early flowering in transgenic tobacco, suggesting that FcFT1 is a fig FT ortholog. Real-time reverse-transcription PCR analysis revealed that FcFT1 mRNA expression occurred only in leaves at the lower nodes, the early fruit setting positions. mRNA levels remained a constant for approximately 5 months from spring to autumn, corresponding almost exactly to the inflorescence differentiation season. Diurnal variation analysis revealed that FcFT1 mRNA expression increased under relative long-day and short-day conditions, but not under continuous darkness. These results suggest that FcFT1 activation is regulated by light conditions and may contribute to fig's unique fruit-setting characteristics.

Lymphocytes with Immunoglobulin E Fc Receptors in Patients with Atopic Disorders

PubMed Central

Spiegelberg, H. L.; O'Connor, R. D.; Simon, R. A.; Mathison, D. A.

1979-01-01

Lymphocytes from normal nonallergic donors and patients with atopic disorders were analyzed for subpopulations bearing Fc receptors for immunoglobulin (Ig)E (Fcε) and IgG (Fcγ), surface IgM (sIgM) and IgD (sIgD), and for T cells forming spontaneous rosettes with sheep erythrocytes (E). The patients were divided into three groups according to serum IgE concentrations and systemic corticosteroid treatment. Group I consisted of 12 atopic patients with either normal or moderately increased IgE levels up to 4,000 U/ml. Four patients of group II and three of group III had 10,500-31,000 U/ml and severe atopic dermatitis. Patients of group III, but not I and II, were receiving corticosteroids systemically. The percentage (mean ±SD) and total number of Fcε+ lymphocytes were 1.2±0.5%, 41±24/mm3 in 12 normals; 1.6±0.9%, 59±43/mm3 in patients of group I: 7.0±2.0%, 187±67/mm3 in group II; and 0.3±0.1%, 13±5/mm3 in patients of group III. The increase in group II and decrease in group III of Fcε+ cells were statistically significantly different from the normal persons and patients of group I. In contrast, the patients did not differ significantly from the donors in sIgM+, sIgD+, Fcγ+, and E+ cell populations. As shown by depletion of sIg+ cells in four patients with atopic disorders, the great majority of the Fcε+ lymphocytes were B cells. However, two patients with elevated Fcε+ cell numbers had small numbers of mixed E- and Fcε-rosetting cells, presumably T cells. Two patients of group II were examined during an acute herpes simplex infection. Both showed an ≅80% decrease of Fcε+ cells at that time. No apparent correlation between numbers of Fcε+ cells and IgE level existed in patients of group I. Injection of an IgE myeloma protein into two monkeys did not significantly change their percentages of Fcε+ lymphocytes. The data indicate that Fcε+ lymphocytes are increased in patients with markedly elevated serum IgE and severe atopic disease, suggesting that these cells may be involved in the regulation and(or) synthesis of IgE antibody formation. PMID:112109

Identification of compounds that decrease numbers of Mycobacteria in human macrophages in the presence of serum amyloid P.

PubMed

Xiang, Wang; Cox, Nehemiah; Gomer, Richard H

2017-09-01

Mϕs are a heterogeneous population of cells and include classically activated Mϕs (M1) and alternatively activated Mϕs (M2). Mϕs can change from M1 to M2 and vice versa in response to environmental stimuli. Serum amyloid P (SAP) is a constitutive plasma protein that polarizes Mϕs to an M2 phenotype, and part of this effect is mediated through FcγRI receptors. In an effort to find ways to alter Mϕs phenotypes, we screened for compounds that can block the SAP-FcγRI interaction. From a screen of 3000 compounds, we found 12 compounds that reduced the ability of fluorescently labeled human SAP to bind cells expressing human FcγRI. Based on cell surface marker expression, 8 of the compounds inhibited the effect of SAP on skewing human Mϕs to an M2 phenotype and in the presence of SAP polarized Mϕs to an M1 phenotype. In diseases, such as tuberculosis, M1s are more effective at killing bacteria than M2s. SAP potentiated the numbers of the mycobacterial strains Mycobacterium smegmatis and Mycobacterium tuberculosis in Mϕs. When added along with SAP, 2 of the compounds reduced intracellular Mycobacterium numbers. Together, these results indicate that the blocking of SAP effects on Mϕs can skew these cells toward an M1 phenotype, and this may be useful in treating diseases, such as tuberculosis. © Society for Leukocyte Biology.

Importance of neonatal FcR in regulating the serum half-life of therapeutic proteins containing the Fc domain of human IgG1: a comparative study of the affinity of monoclonal antibodies and Fc-fusion proteins to human neonatal FcR.

PubMed

Suzuki, Takuo; Ishii-Watabe, Akiko; Tada, Minoru; Kobayashi, Tetsu; Kanayasu-Toyoda, Toshie; Kawanishi, Toru; Yamaguchi, Teruhide

2010-02-15

The neonatal FcR (FcRn) binds to the Fc domain of IgG at acidic pH in the endosome and protects IgG from degradation, thereby contributing to the long serum half-life of IgG. To date, more than 20 mAb products and 5 Fc-fusion protein products have received marketing authorization approval in the United States, the European Union, or Japan. Many of these therapeutic proteins have the Fc domain of human IgG1; however, the serum half-lives differ in each protein. To elucidate the role of FcRn in the pharmacokinetics of Fc domain-containing therapeutic proteins, we evaluated the affinity of the clinically used human, humanized, chimeric, or mouse mAbs and Fc-fusion proteins to recombinant human FcRn by surface plasmon resonance analysis. The affinities of these therapeutic proteins to FcRn were found to be closely correlated with the serum half-lives reported from clinical studies, suggesting the important role of FcRn in regulating their serum half-lives. The relatively short serum half-life of Fc-fusion proteins was thought to arise from the low affinity to FcRn. The existence of some mAbs having high affinity to FcRn and a short serum half-life, however, suggested the involvement of other critical factor(s) in determining the serum half-life of such Abs. We further investigated the reason for the relatively low affinity of Fc-fusion proteins to FcRn and suggested the possibility that the receptor domain of Fc-fusion protein influences the structural environment of the FcRn binding region but not of the FcgammaRI binding region of the Fc domain.

Integrated cell and process engineering for improved transient production of a "difficult-to-express" fusion protein by CHO cells.

PubMed

Johari, Yusuf B; Estes, Scott D; Alves, Christina S; Sinacore, Marty S; James, David C

2015-12-01

Based on an optimized electroporation protocol, we designed a rapid, milliliter-scale diagnostic transient production assay to identify limitations in the ability of Chinese hamster ovary (CHO) cells to produce a model "difficult-to-express" homodimeric Fc-fusion protein, Sp35Fc, that exhibited very low volumetric titer and intracellular formation of disulfide-bonded oligomeric aggregates post-transfection. As expression of Sp35Fc induced an unfolded protein response in transfected host cells, we utilized the transient assay to compare, in parallel, multiple functionally diverse strategies to engineer intracellular processing of Sp35Fc in order to increase production and reduce aggregation as two discrete design objectives. Specifically, we compared the effect of (i) co-expression of ER-resident molecular chaperones (BiP, PDI, CypB) or active forms of UPR transactivators (ATF6c, XBP1s) at varying recombinant gene load, (ii) addition of small molecules known to act as chemical chaperones (PBA, DMSO, glycerol, betaine, TMAO) or modulate UPR signaling (PERK inhibitor GSK2606414) at varying concentration, (iii) a reduction in culture temperature to 32°C. Using this information, we designed a biphasic, Sp35Fc-specific transient manufacturing process mediated by lipofection that utilized CypB co-expression at an optimal Sp35Fc:CypB gene ratio of 5:1 to initially maximize transfected cell proliferation, followed by addition of a combination of PBA (0.5 mM) and glycerol (1% v/v) at the onset of stationary phase to maximize cell specific production and eliminate Sp35Fc aggregation. Using this optimal, engineered process transient Sp35Fc production was significantly increased sixfold over a 12 day production process with no evidence of disulfide-bonded aggregates. Finally, transient production in clonally derived sub-populations (derived from parental CHO host) screened for a heritably improved capability to produce Sp35Fc was also significantly improved by the optimized process, showing that protein-specific cell/process engineering can provide a solution that exceeds the limits of genetic/functional diversity within heterogeneous host cell populations. . © 2015 Wiley Periodicals, Inc.

Btk inhibition treats TLR7/IFN driven murine lupus.

PubMed

Bender, Andrew T; Pereira, Albertina; Fu, Kai; Samy, Eileen; Wu, Yin; Liu-Bujalski, Lesley; Caldwell, Richard; Chen, Yi-Ying; Tian, Hui; Morandi, Federica; Head, Jared; Koehler, Ursula; Genest, Melinda; Okitsu, Shinji L; Xu, Daigen; Grenningloh, Roland

2016-03-01

Bruton's tyrosine kinase (Btk) is expressed in a variety of immune cells and previous work has demonstrated that blocking Btk is a promising strategy for treating autoimmune diseases. Herein, we utilized a tool Btk inhibitor, M7583, to determine the therapeutic efficacy of Btk inhibition in two mouse lupus models driven by TLR7 activation and type I interferon. In BXSB-Yaa lupus mice, Btk inhibition reduced autoantibodies, nephritis, and mortality. In the pristane-induced DBA/1 lupus model, Btk inhibition suppressed arthritis, but autoantibodies and the IFN gene signature were not significantly affected; suggesting efficacy was mediated through inhibition of Fc receptors. In vitro studies using primary human macrophages revealed that Btk inhibition can block activation by immune complexes and TLR7 which contributes to tissue damage in SLE. Overall, our results provide translational insight into how Btk inhibition may provide benefit to a variety of SLE patients by affecting both BCR and FcR signaling. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Cytoskeleton in Mast Cell Signaling

PubMed Central

Dráber, Pavel; Sulimenko, Vadym; Dráberová, Eduarda

2012-01-01

Mast cell activation mediated by the high affinity receptor for IgE (FcεRI) is a key event in allergic response and inflammation. Other receptors on mast cells, as c-Kit for stem cell factor and G protein-coupled receptors (GPCRs) synergistically enhance the FcεRI-mediated release of inflammatory mediators. Activation of various signaling pathways in mast cells results in changes in cell morphology, adhesion to substrate, exocytosis, and migration. Reorganization of cytoskeleton is pivotal in all these processes. Cytoskeletal proteins also play an important role in initial stages of FcεRI and other surface receptors induced triggering. Highly dynamic microtubules formed by αβ-tubulin dimers as well as microfilaments build up from polymerized actin are affected in activated cells by kinases/phosphatases, Rho GTPases and changes in concentration of cytosolic Ca2+. Also important are nucleation proteins; the γ-tubulin complexes in case of microtubules or Arp 2/3 complex with its nucleation promoting factors and formins in case of microfilaments. The dynamic nature of microtubules and microfilaments in activated cells depends on many associated/regulatory proteins. Changes in rigidity of activated mast cells reflect changes in intermediate filaments build up from vimentin. This review offers a critical appraisal of current knowledge on the role of cytoskeleton in mast cells signaling. PMID:22654883

Targeted inhibition of osteosarcoma tumor growth by bone marrow-derived mesenchymal stem cells expressing cytosine deaminase/5-fluorocytosine in tumor-bearing mice.

PubMed

NguyenThai, Quynh-Anh; Sharma, Neelesh; Luong, Do Huynh; Sodhi, Simrinder Singh; Kim, Jeong-Hyun; Kim, Nameun; Oh, Sung-Jong; Jeong, Dong Kee

2015-01-01

Mesenchymal stem cells (MSCs) are considered as an attractive approach for gene or drug delivery in cancer therapy. In the present study, the ability of human bone marrow-derived MSCs expressing the cytosine deaminase/5-fluorocytosine prodrug (CD/5-FC MSCs) to target the human osteosarcoma cell line Cal72 was evaluated. The stable CD/5-FC MSC cell line was established by transfection of pEGFP containing the cytosine deaminase gene into MSCs with G418 selection. The anti-tumor effect was verified by a bystander effect assay in vitro and co-injection of Cal72 and CD/5-FC MSCs in cancer-bearing mice. The therapeutic CD/5-FC MSCs retained the characteristics of multipotent cells, such as differentiation into adipocytes/osteocytes and expression of mesenchymal markers (CD90 and CD44), and showed migration toward Cal72 cells to a greater extent than the native MSCs. The bystander effect assay showed that the CD/5-FC MSCs significantly augmented Cal72 cytotoxicity in direct co-culture and in the presence of 5-FC through the application of conditioned medium. In osteosarcoma-bearing mice, the CD/5-FC MSCs inhibited tumor growth compared to control mice subcutaneously injected with only Cal72 cells. Taken together, these findings suggest that CD/5-FC MSCs may be suitable for targeting human osteosarcoma. Copyright © 2015 John Wiley & Sons, Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsland, Paul A.; Farrugia, William; Bradford, Tessa M.

The interaction of Abs with their specific FcRs is of primary importance in host immune effector systems involved in infection and inflammation, and are the target for immune evasion by pathogens. Fc{gamma}RIIa is a unique and the most widespread activating FcR in humans that through avid binding of immune complexes potently triggers inflammation. Polymorphisms of Fc{gamma}RIIa (high responder/low responder [HR/LR]) are linked to susceptibility to infections, autoimmune diseases, and the efficacy of therapeutic Abs. In this article, we define the three-dimensional structure of the complex between the HR (arginine, R134) allele of Fc{gamma}RIIa (Fc{gamma}RIIa-HR) and the Fc region of amore » humanized IgG1 Ab, hu3S193. The structure suggests how the HR/LR polymorphism may influence Fc{gamma}RIIa interactions with different IgG subclasses and glycoforms. In addition, mutagenesis defined the basis of the epitopes detected by FcR blocking mAbs specific for Fc{gamma}RIIa (IV.3), Fc{gamma}RIIb (X63-21), and a pan Fc{gamma}RII Ab (8.7). The epitopes detected by these Abs are distinct, but all overlap with residues defined by crystallography to contact IgG. Finally, crystal structures of LR (histidine, H134) allele of Fc{gamma}RIIa and Fc{gamma}RIIa-HR reveal two distinct receptor dimers that may represent quaternary states on the cell surface. A model is presented whereby a dimer of Fc{gamma}RIIa-HR binds Ag-Ab complexes in an arrangement that possibly occurs on the cell membrane as part of a larger signaling assembly.« less

Independent Preharvest Applications of Methyl Jasmonate and Chitosan Elicit Differential Upregulation of Defense-Related Genes with Reduced Incidence of Gray Mold Decay during Postharvest Storage of Fragaria chiloensis Fruit

PubMed Central

Saavedra, Gabriela M.; Sanfuentes, Eugenio; Figueroa, Carlos R.

2017-01-01

The Chilean strawberry (Fragaria chiloensis) fruit has interesting organoleptic properties, but its postharvest life is affected by gray mold decay caused by Botrytis cinerea. The effect of preharvest applications of methyl jasmonate (MeJA) or chitosan on the molecular defense-related responses and protection against gray mold decay were investigated in Chilean strawberry fruit during postharvest storage. Specifically, we inoculated harvested fruit with B. cinerea spores and studied the expression of genes encoding for the pathogenesis-related (PR) proteins β-1,3-glucanases (FcBG2-1, FcBG2-2 and FcBG2-3) and chitinases (FcCHI2-2 and FcCHI3-1), and for polygalacturonase inhibiting proteins (FcPGIP1 and FcPGIP2) at 0, 2, 24, 48, and 72 h post inoculation (hpi). Remarkably, MeJA- and chitosan-treated fruit exhibited a lower incidence of B. cinerea infection than the control-treated at 48 and 72 hpi. At the molecular level, both are efficient elicitors for priming in F. chiloensis fruit since we observed an upregulation of the FcBG2-1, FcBG2-3, FcPGIP1, and FcPGIP2 at 0 hpi. Moreover, a chitosan-mediated upregulation of FcPGIPs at early times post inoculation (2–24 hpi) and MeJA upregulated FcBGs (24–72 hpi) and FcPGIP1 at later times could contribute to reduce B. cinerea incidence by differential upregulation of defense genes. We concluded that preharvest applications of MeJA or chitosan had a long-lasting effect on the reduction of B. cinerea incidence during postharvest as well as an enhancer effect on the induction of PR and PGIP gene expression. PMID:28671619

Independent Preharvest Applications of Methyl Jasmonate and Chitosan Elicit Differential Upregulation of Defense-Related Genes with Reduced Incidence of Gray Mold Decay during Postharvest Storage of Fragaria chiloensis Fruit.

PubMed

Saavedra, Gabriela M; Sanfuentes, Eugenio; Figueroa, Pablo M; Figueroa, Carlos R

2017-07-03

The Chilean strawberry ( Fragaria chiloensis ) fruit has interesting organoleptic properties, but its postharvest life is affected by gray mold decay caused by Botrytis cinerea . The effect of preharvest applications of methyl jasmonate (MeJA) or chitosan on the molecular defense-related responses and protection against gray mold decay were investigated in Chilean strawberry fruit during postharvest storage. Specifically, we inoculated harvested fruit with B. cinerea spores and studied the expression of genes encoding for the pathogenesis-related (PR) proteins β-1,3-glucanases ( FcBG2-1 , FcBG2-2 and FcBG2-3 ) and chitinases ( FcCHI2-2 and FcCHI3-1 ), and for polygalacturonase inhibiting proteins ( FcPGIP1 and FcPGIP2 ) at 0, 2, 24, 48, and 72 h post inoculation (hpi). Remarkably, MeJA- and chitosan-treated fruit exhibited a lower incidence of B. cinerea infection than the control-treated at 48 and 72 hpi. At the molecular level, both are efficient elicitors for priming in F. chiloensis fruit since we observed an upregulation of the FcBG2-1 , FcBG2-3 , FcPGIP1, and FcPGIP2 at 0 hpi. Moreover, a chitosan-mediated upregulation of FcPGIP s at early times post inoculation (2-24 hpi) and MeJA upregulated FcBG s (24-72 hpi) and FcPGIP1 at later times could contribute to reduce B. cinerea incidence by differential upregulation of defense genes. We concluded that preharvest applications of MeJA or chitosan had a long-lasting effect on the reduction of B. cinerea incidence during postharvest as well as an enhancer effect on the induction of PR and PGIP gene expression.

Characterization of the receptors for mycobacterial cord factor in Guinea pig.

PubMed

Toyonaga, Kenji; Miyake, Yasunobu; Yamasaki, Sho

2014-01-01

Guinea pig is a widely used animal for research and development of tuberculosis vaccines, since its pathological disease process is similar to that present in humans. We have previously reported that two C-type lectin receptors, Mincle (macrophage inducible C-type lectin, also called Clec4e) and MCL (macrophage C-type lectin, also called Clec4d), recognize the mycobacterial cord factor, trehalose-6,6'-dimycolate (TDM). Here, we characterized the function of the guinea pig homologue of Mincle (gpMincle) and MCL (gpMCL). gpMincle directly bound to TDM and transduced an activating signal through ITAM-bearing adaptor molecule, FcRγ. Whereas, gpMCL lacked C-terminus and failed to bind to TDM. mRNA expression of gpMincle was detected in the spleen, lymph nodes and peritoneal macrophages and it was strongly up-regulated upon stimulation of zymosan and TDM. The surface expression of gpMincle was detected on activated macrophages by a newly established monoclonal antibody that also possesses a blocking activity. This antibody potently suppressed TNF production in BCG-infected macrophages. Collectively, gpMincle is the TDM receptor in the guinea pig and TDM-Mincle axis is involved in host immune responses against mycobacteria.

Enduring abolishment of remote but not recent expression of conditioned fear by the blockade of calcium-permeable AMPA receptors before extinction training.

PubMed

Zelena, Dóra; Mikics, Éva; Balázsfi, Diána; Varga, János; Klausz, Barbara; Urbán, Eszter; Sipos, Eszter; Biró, László; Miskolczi, Christina; Kovács, Krisztina; Ferenczi, Szilamér; Haller, József

2016-06-01

Calcium-permeable (GluA2 subunit-free) AMPA receptors (CP-AMPAR) play prominent roles in fear extinction; however, no blockers of these receptors were studied in tests relevant to extinction learning so far. The CP-AMPAR antagonist IEM-1460 was administered once before extinction trainings, which were started either 1 or 28 days after fear conditioning (FC). We used a mild extinction protocol that durably decreased but did not abolish conditioned fear. The messenger RNA (mRNA) expression of GluA1 and GluA2 subunits were investigated at both time points in the ventromedial prefrontal cortex (vmPFC) and amygdala. IEM-1460 transiently facilitated extinction 1 day after conditioning, but learned fear spontaneously recovered 4 weeks later. When the extinction protocol was applied 28 days after training, IEM-1460 enhanced extinction memory, moreover abolished conditioned fear for at least a month. The expression of GluA1 and GluA2 mRNAs was increased at both time points in the vmPFC. In the basolateral and central amygdala, the GluA1/GluA2 mRNA ratio increased, suggesting a shift towards the preponderance of GluA1 over GluA2 expression. AMPAR blockade lastingly enhanced the extinction of remote but not recent fear memories. Time-dependent changes in AMPA receptor subunit mRNA expression may explain the differential effects of CP-AMPAR blockade on recent and remote conditioned fear, further supporting the notion that the mechanisms maintaining learned fear change over time. Our findings suggest clinical implications for CP-AMPAR blockers, particularly for acquired anxieties (e.g., post-traumatic stress disorder) which have a slow onset and are durable.

syk kinase activation by a src kinase-initiated activation loop phosphorylation chain reaction

PubMed Central

El-Hillal, O.; Kurosaki, T.; Yamamura, H.; Kinet, J.-P.; Scharenberg, A. M.

1997-01-01

Activation of the syk tyrosine kinase occurs almost immediately following engagement of many types of antigen receptors, including Fc receptors, but the mechanism through which syk is activated is currently unclear. Here we demonstrate that Fc receptor-induced syk activation occurs as the result of phosphorylation of the syk activation loop by both src family kinases and other molecules of activated syk, suggesting that syk activation occurs as the result of a src kinase-initiated activation loop phosphorylation chain reaction. This type of activation mechanism predicts that syk activation would exhibit exponential kinetics, providing a potential explanation for its rapid and robust activation by even weak antigen receptor stimuli. We propose that a similar mechanism may be responsible for generating rapid activation of other cytoplasmic tyrosine kinases, such as those of the Bruton tyrosine kinase/tec family, as well. PMID:9050880

CD22 serves as a receptor for soluble IgM.

PubMed

Adachi, Takahiro; Harumiya, Satoru; Takematsu, Hiromu; Kozutsumi, Yasunori; Wabl, Matthias; Fujimoto, Manabu; Tedder, Thomas F

2012-01-01

CD22 (Siglec-2) is a B-cell membrane-bound lectin that recognizes glycan ligands containing α2,6-linked sialic acid (α2,6Sia) and negatively regulates signaling through the B-cell Ag receptor (BCR). Although CD22 has been investigated extensively, its precise function remains unclear due to acting multiple phases. Here, we demonstrate that CD22 is efficiently activated in trans by complexes of Ag and soluble IgM (sIgM) due to the presence of glycan ligands on sIgM. This result strongly suggests sIgM as a natural trans ligand for CD22. Also, CD22 appears to serve as a receptor for sIgM, which induces a negative feedback loop for B-cell activation similar to the Fc receptor for IgG (FcγRIIB). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analytical FcRn affinity chromatography for functional characterization of monoclonal antibodies

PubMed Central

Schlothauer, Tilman; Rueger, Petra; Stracke, Jan Olaf; Hertenberger, Hubert; Fingas, Felix; Kling, Lothar; Emrich, Thomas; Drabner, Georg; Seeber, Stefan; Auer, Johannes; Koch, Stefan; Papadimitriou, Apollon

2013-01-01

The neonatal Fc receptor (FcRn) is important for the metabolic fate of IgG antibodies in vivo. Analysis of the interaction between FcRn and IgG in vitro might provide insight into the structural and functional integrity of therapeutic IgG that may affect pharmacokinetics (PK) in vivo. We developed a standardized pH gradient FcRn affinity liquid chromatography method with conditions closely resembling the physiological mechanism of interaction between IgG and FcRn. This method allows the separation of molecular IgG isoforms, degradation products and engineered molecules based on their affinity to FcRn. Human FcRn was immobilized on the column and a linear pH gradient from pH 5.5 to 8.8 was applied. FcRn chromatography was used in comparison to surface plasmon resonance to characterize different monoclonal IgG preparations, e.g., oxidized or aggregated species. Wild-type and engineered IgGs were compared in vitro by FcRn chromatography and in vivo by PK studies in huFcRn transgenic mice. Analytical FcRn chromatography allows differentiation of IgG samples and variants by peak pattern and retention time profile. The method can distinguish: 1) IgGs with different Fabs, 2) oxidized from native IgG, 3) aggregates from monomer and 4) antibodies with mutations in the Fc part from wild-type IgGs. Changes in the FcRn chromatographic behavior of mutant IgGs relative to the wild-type IgG correlate to changes in the PK profile in the FcRn transgenic mice. These results demonstrate that FcRn affinity chromatography is a useful new method for the assessment of IgG integrity. PMID:23765230

Combined glyco- and protein-Fc engineering simultaneously enhance cytotoxicity and half-life of a therapeutic antibody.

PubMed

Monnet, Céline; Jorieux, Sylvie; Souyris, Nathalie; Zaki, Ouafa; Jacquet, Alexandra; Fournier, Nathalie; Crozet, Fabien; de Romeuf, Christophe; Bouayadi, Khalil; Urbain, Rémi; Behrens, Christian K; Mondon, Philippe; Fontayne, Alexandre

2014-01-01

While glyco-engineered monoclonal antibodies (mAbs) with improved antibody-dependent cell-mediated cytotoxicity (ADCC) are reaching the market, extensive efforts have also been made to improve their pharmacokinetic properties to generate biologically superior molecules. Most therapeutic mAbs are human or humanized IgG molecules whose half-life is dependent on the neonatal Fc receptor FcRn. FcRn reduces IgG catabolism by binding to the Fc domain of endocytosed IgG in acidic lysosomal compartments, allowing them to be recycled into the blood. Fc-engineered mAbs with increased FcRn affinity resulted in longer in vivo half-life in animal models, but also in healthy humans. These Fc-engineered mAbs were obtained by alanine scanning, directed mutagenesis or in silico approach of the FcRn binding site. In our approach, we applied a random mutagenesis technology (MutaGen™) to generate mutations evenly distributed over the whole Fc sequence of human IgG1. IgG variants with improved FcRn-binding were then isolated from these Fc-libraries using a pH-dependent phage display selection process. Two successive rounds of mutagenesis and selection were performed to identify several mutations that dramatically improve FcRn binding. Notably, many of these mutations were unpredictable by rational design as they were located distantly from the FcRn binding site, validating our random molecular approach. When produced on the EMABling(®) platform allowing effector function increase, our IgG variants retained both higher ADCC and higher FcRn binding. Moreover, these IgG variants exhibited longer half-life in human FcRn transgenic mice. These results clearly demonstrate that glyco-engineering to improve cytotoxicity and protein-engineering to increase half-life can be combined to further optimize therapeutic mAbs.

Structural Basis for FcγRIIa Recognition of Human IgG and Formation of Inflammatory Signaling Complexes

PubMed Central

Ramsland, Paul A.; Farrugia, William; Bradford, Tessa M.; Tan Sardjono, Caroline; Esparon, Sandra; Trist, Halina M.; Powell, Maree S.; Szee Tan, Peck; Cendron, Angela C.; Wines, Bruce D.; Scott, Andrew M.; Hogarth, P. Mark

2012-01-01

The interaction of Abs with their specific FcRs is of primary importance in host immune effector systems involved in infection and inflammation, and are the target for immune evasion by pathogens. FcγRIIa is a unique and the most widespread activating FcR in humans that through avid binding of immune complexes potently triggers inflammation. Polymorphisms of FcγRIIa (high responder/low responder [HR/LR]) are linked to susceptibility to infections, autoimmune diseases, and the efficacy of therapeutic Abs. In this article, we define the three-dimensional structure of the complex between the HR (arginine, R134) allele of FcγRIIa (FcγRIIa-HR) and the Fc region of a humanized IgG1 Ab, hu3S193. The structure suggests how the HR/LR polymorphism may influence FcγRIIa interactions with different IgG subclasses and glycoforms. In addition, mutagenesis defined the basis of the epitopes detected by FcR blocking mAbs specific for FcγRIIa (IV.3), FcγRIIb (X63-21), and a pan FcγRII Ab (8.7). The epitopes detected by these Abs are distinct, but all overlap with residues defined by crystallography to contact IgG. Finally, crystal structures of LR (histidine, H134) allele of FcγRIIa and FcγRIIa-HR reveal two distinct receptor dimers that may represent quaternary states on the cell surface. A model is presented whereby a dimer of FcγRIIa-HR binds Ag–Ab complexes in an arrangement that possibly occurs on the cell membrane as part of a larger signaling assembly. PMID:21856937

Engineered Fc variant antibodies with enhanced ability to recruit complement and mediate effector functions

PubMed Central

Moore, Gregory L; Chen, Hsing; Karki, Sher

2010-01-01

Engineering the antibody Fc region to enhance the cytotoxic activity of therapeutic antibodies is currently an active area of investigation. The contribution of complement to the mechanism of action of some antibodies that target cancers and pathogens makes a compelling case for its optimization. Here we describe the generation of a series of Fc variants with enhanced ability to recruit complement. Variants enhanced the cytotoxic potency of an anti-CD20 antibody up to 23-fold against tumor cells in CDC assays, and demonstrated a correlated increase in C1q binding affinity. Complementenhancing substitutions combined additively, and in one case synergistically, with substitutions previously engineered for improved binding to Fc gamma receptors. The engineered combinations provided a range of effector function activities, including simultaneously enhanced CDC, ADCC, and phagocytosis. Variants were also effective at boosting the effector function of antibodies targeting the antigens CD40 and CD19, in the former case enhancing CDC over 600-fold, and in the latter case imparting complement-mediated activity onto an IgG1 antibody that was otherwise incapable of it. This work expands the toolkit of modifications for generating monoclonal antibodies with improved therapeutic potential and enables the exploration of optimized synergy between Fc gamma receptors and complement pathways for the destruction of tumors and infectious pathogens. PMID:20150767

Extending Serum Half-life of Albumin by Engineering Neonatal Fc Receptor (FcRn) Binding*

PubMed Central

Andersen, Jan Terje; Dalhus, Bjørn; Viuff, Dorthe; Ravn, Birgitte Thue; Gunnarsen, Kristin Støen; Plumridge, Andrew; Bunting, Karen; Antunes, Filipa; Williamson, Rebecca; Athwal, Steven; Allan, Elizabeth; Evans, Leslie; Bjørås, Magnar; Kjærulff, Søren; Sleep, Darrell; Sandlie, Inger; Cameron, Jason

2014-01-01

A major challenge for the therapeutic use of many peptides and proteins is their short circulatory half-life. Albumin has an extended serum half-life of 3 weeks because of its size and FcRn-mediated recycling that prevents intracellular degradation, properties shared with IgG antibodies. Engineering the strictly pH-dependent IgG-FcRn interaction is known to extend IgG half-life. However, this principle has not been extensively explored for albumin. We have engineered human albumin by introducing single point mutations in the C-terminal end that generated a panel of variants with greatly improved affinities for FcRn. One variant (K573P) with 12-fold improved affinity showed extended serum half-life in normal mice, mice transgenic for human FcRn, and cynomolgus monkeys. Importantly, favorable binding to FcRn was maintained when a single-chain fragment variable antibody was genetically fused to either the N- or the C-terminal end. The engineered albumin variants may be attractive for improving the serum half-life of biopharmaceuticals. PMID:24652290

Demonstration of Functional Similarity of Proposed Biosimilar ABP 501 to Adalimumab.

PubMed

Velayudhan, Jyoti; Chen, Yuh-Feng; Rohrbach, Amanda; Pastula, Christina; Maher, Gwen; Thomas, Heather; Brown, Ryan; Born, Teresa L

2016-08-01

Due to the complex molecular structure and proprietary manufacturing processes of monoclonal antibodies (mAbs), differences in structure and function may be expected during development of biosimilar mAbs. Important regulatory requirements for approval of biosimilar products involve comprehensive assessments of any potential differences between proposed biosimilars and reference mAbs, including differences in all known mechanisms of action, using sensitive and relevant methods. Any identified structural differences should not result in differences in biofunctional or clinical activity. A comprehensive assessment comparing the Amgen biosimilar candidate ABP 501 with FDA-licensed adalimumab (adalimumab [US]) and EU-authorized adalimumab (adalimumab [EU]) was conducted to demonstrate similarity in biofunctional activity. The functional similarity assessment included testing of binding kinetics to soluble tumor necrosis factor α (TNFα) and relative binding to transmembrane TNFα. The neutralization of TNFα-induced caspase activation, TNFα- and lymphotoxin-α (LTα)-induced chemokine production, and cytotoxicity was also tested. Binding to Fc-gamma receptors FcγRIa, FcγRIIa (131H), FcγRIIIa (158V and 158F), and neonatal Fc receptor (FcRn) was compared with the reference mAbs, as was antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. The data demonstrate that ABP 501 is similar to both adalimumab (US) and adalimumab (EU) with respect to evaluated biofunctional activities. Similarity in biofunctional activity is a critical component of the totality of evidence required for demonstration of biosimilarity. The functional similarity demonstrated for ABP 501 comprehensively assesses the known mechanisms of action of adalimumab, supporting the conclusion that ABP 501, adalimumab (US), and adalimumab (EU) are likely to be clinically similar.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mezo, Adam R.; Sridhar, Vandana; Badger, John

The neonatal Fc receptor, FcRn, is responsible for the long half-life of IgG molecules in vivo and is a potential therapeutic target for the treatment of autoimmune diseases. A family of peptides comprising the consensus motif GHFGGXY, where X is preferably a hydrophobic amino acid, was shown previously to inhibit the human IgG:human FcRn protein-protein interaction (Mezo, A. R., McDonnell, K. A., Tan Hehir, C. A., Low, S. C., Palombella, V. J., Stattel, J. M., Kamphaus, G. D., Fraley, C., Zhang, Y., Dumont, J. A., and Bitonti, A. J. (2008) Proc. Natl. Acad. Sci. U.S.A., 105, 2337-2342). Herein, the x-raymore » crystal structure of a representative monomeric peptide in complex with human FcRn was solved to 2.6 {angstrom} resolution. The structure shows that the peptide binds to human FcRn at the same general binding site as does the Fc domain of IgG. The data correlate well with structure-activity relationship data relating to how the peptide family binds to human FcRn. In addition, the x-ray crystal structure of a representative dimeric peptide in complex with human FcRn shows how the bivalent ligand can bridge two FcRn molecules, which may be relevant to the mechanism by which the dimeric peptides inhibit FcRn and increase IgG catabolism in vivo. Modeling of the peptide:FcRn structure as compared with available structural data on Fc and FcRn suggest that the His-6 and Phe-7 (peptide) partially mimic the interaction of His-310 and Ile-253 (Fc) in binding to FcRn, but using a different backbone topology.« less

Correlation between CD16a binding and immuno effector functionality of an antigen specific immunoglobulin Fc fragment (Fcab).

PubMed

Kainer, Manuela; Antes, Bernhard; Wiederkum, Susanne; Wozniak-Knopp, Gordana; Bauer, Anton; Rüker, Florian; Woisetschläger, Max

2012-10-15

Antigen binding immunoglobulin Fc fragments (Fcab) are generated by engineering loop regions in the CH3 domain of human IgG1 Fc. Variants of an Fcab specific for Her-2 were designed to display either enhanced (S239D:A330L:I332E) or diminished (L234A:L235A) binding affinities to the Fc receptor CD16a based on mutations described previously. The two mutant Fcab proteins demonstrated the expected modulation of CD16a binding. Interaction with recombinant or cell surface expressed Her-2 was unaffected in both mutants compared to the parental Fcab. Binding affinities for CD16a correlated with the ADCC-potencies of the Fcab variants. Additional studies indicated that the L234A:L235A variant Fcab had equivalent structural features as the unmodified Fcab since their DSC profiles were similar and antigen binding after re-folding upon partial heat denaturation had not changed. Introduction of the S239D:A330L:I332E mutations resulted in a significant reduction of the CH2 domain melting temperature, a moderate decrease of the thermal transition of the CH3 domain and lower antigen binding after thermal stress compared to the parental Fcab. We conclude that the known correlation between CD16a binding affinity and ADCC potency is also valid in Fcab proteins and that antigen specific Fcab molecules can be further engineered for fine tuning of immuno effector functions. Copyright © 2012 Elsevier Inc. All rights reserved.

Potent Immune Modulation by MEDI6383, an Engineered Human OX40 Ligand IgG4P Fc Fusion Protein.

PubMed

Oberst, Michael D; Augé, Catherine; Morris, Chad; Kentner, Stacy; Mulgrew, Kathy; McGlinchey, Kelly; Hair, James; Hanabuchi, Shino; Du, Qun; Damschroder, Melissa; Feng, Hui; Eck, Steven; Buss, Nicholas; de Haan, Lolke; Pierce, Andrew J; Park, Haesun; Sylwester, Andrew; Axthelm, Michael K; Picker, Louis; Morris, Nicholas P; Weinberg, Andrew; Hammond, Scott A

2018-05-01

Ligation of OX40 (CD134, TNFRSF4) on activated T cells by its natural ligand (OX40L, CD252, TNFSF4) enhances cellular survival, proliferation, and effector functions such as cytokine release and cellular cytotoxicity. We engineered a recombinant human OX40L IgG4P Fc fusion protein termed MEDI6383 that assembles into a hexameric structure and exerts potent agonist activity following engagement of OX40. MEDI6383 displayed solution-phase agonist activity that was enhanced when the fusion protein was clustered by Fc gamma receptors (FcγRs) on the surface of adjacent cells. The resulting costimulation of OX40 on T cells induced NFκB promoter activity in OX40-expressing T cells and induced Th1-type cytokine production, proliferation, and resistance to regulatory T cell (Treg)-mediated suppression. MEDI6383 enhanced the cytolytic activity of tumor-reactive T cells and reduced tumor growth in the context of an alloreactive human T cell:tumor cell admix model in immunocompromised mice. Consistent with the role of OX40 costimulation in the expansion of memory T cells, MEDI6383 administered to healthy nonhuman primates elicited peripheral blood CD4 and CD8 central and effector memory T-cell proliferation as well as B-cell proliferation. Together, these results suggest that OX40 agonism has the potential to enhance antitumor immunity in human malignancies. Mol Cancer Ther; 17(5); 1024-38. ©2018 AACR . ©2018 American Association for Cancer Research.

IgG-Fc-mediated effector functions: molecular definition of interaction sites for effector ligands and the role of glycosylation.

PubMed

Jefferis, R; Lund, J; Pound, J D

1998-06-01

The Fc region of human IgG expresses interaction sites for many effector ligands. In this review the topographical distributions of ten of these sites are discussed in relation to functional requirement. It is apparent that interaction sites localised to the inter-CH2-CH3 domain region of the Fc allow for functional divalency, whereas sites localised to the hinge proximal region of the CH2 domain are functionally monovalent, with expression of the latter sites being particularly dependent on glycosylation. All x-ray crystal structures for Fc and Fc-ligand complexes report that the protein structure of the hinge proximal region of the CH2 domain is "disordered", suggesting "internal mobility". We propose a model in which such "internal mobility" results in the generation of a dynamic equilibrium between multiple conformers, certain of which express interaction sites specific to individual ligands. The emerging understanding of the influence of oligosaccharide/protein interactions on protein conformation and biological function of IgG antibodies suggests a potential to generate novel glycoforms of antibody molecules having unique profiles of effector functions.

Studies to Prevent Degradation of Recombinant Fc-Fusion Protein Expressed in Mammalian Cell Line and Protein Characterization

PubMed Central

Chakrabarti, Sanjukta; Barrow, Colin J.; Kanwar, Rupinder K.; Ramana, Venkata; Kanwar, Jagat R.

2016-01-01

Clipping of recombinant proteins is a major issue in animal cell cultures. A recombinant Fc-fusion protein, VEGFR1(D1–D3)-Fc expressed in CHOK1SV GS-KO cells was observed to be undergoing clippings in lab scale cultures. Partial cleaving of expressed protein initiated early on in cell culture and was observed to increase over time in culture and also on storage. In this study, a few parameters were explored in a bid to inhibit clipping in the fusion protein The effects of culture temperature, duration of culture, the addition of an anti-clumping agent, ferric citrate and use of protease inhibitor cocktail on inhibition of proteolysis of the Fc fusion were studied. Lowering of culture temperature from 37 to 30 °C alone appears to be the best solution for reducing protein degradation from the quality, cost and regulatory points of view. The obtained Fc protein was characterized and found to be in its stable folded state, exhibiting a high affinity for its ligand and also biological and functional activities. PMID:27294920

Diagnosis and management of primary autoimmune neutropenia in children: insights for clinicians

PubMed Central

Dufour, Carlo

2015-01-01

Autoimmune neutropenia of infancy (AIN), also called primary autoimmune neutropenia, is a disease in which antibodies recognize membrane antigens of neutrophils, mostly located on immunoglobulin G (IgG) Fc receptor type 3b (FcγIIIb receptor), causing their peripheral destruction. It is the most frequent type of neutropenia in children under 3–4 years of age and in most cases shows a benign, self-limited course. The diagnosis is based on evidence of indirect antineutrophil antibodies, whose detection frequently remains difficult. In this review we have analyzed the literature regarding AIN and present our personal experience in diagnosis and management. PMID:25642312

Expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 genes in eutopic endometrium of infertile women with endometriosis during the implantation window: a pilot study.

PubMed

Broi, Michele G Da; Rocha, Carlos V; Meola, Juliana; Martins, Wellington P; Carvalho, Filomena M; Ferriani, Rui A; Navarro, Paula A

2017-09-01

Alterations in endometrial receptivity may be involved in the etiopathogenesis of endometriosis-related infertility. The literature has suggested that patients with endometriosis present progestin resistance, which could affect embryo implantation. We question the presence of alterations in the expression of the progesterone receptor gene (PGR) and the genes related to endometrium-embryo interaction regulated by progesterone. This pilot study compared the expression of PGR, HBEGF, ITGAV, ITGB3, and SPP1 genes in eutopic endometrium during the implantation window (IW) in infertile women with endometriosis with that observed in the endometrium of fertile and infertile controls. In this prospective case-control study, endometrial biopsies were performed during the IW in patients aged between 18 and 45 years old, with regular cycles and without endocrine/systemic dysfunctions, divided into endometriosis (END), infertile control (IC) and fertile control (FC) groups. Total RNA extraction, cDNA synthesis, and gene expression analysis by Real-Time PCR were performed. We assessed the size of the difference that our series was powered to detect. From the 687 patients who underwent diagnostic videolaparoscopy or tubal ligation at the University Hospital, 130 were eligible. Of these, 32 had endometrial samples collected, with 17 confirmed in the IW. Fifteen samples (5 END, 5 IC and 5 FC) were analyzed. There was no significant difference in the expression of any studied gene. Our sample size allowed us to identify or discard large differences (two standard deviations) among the groups. Endometriosis doesn't cause large changes in the endometrial expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 during the IW.

Expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 genes in eutopic endometrium of infertile women with endometriosis during the implantation window: a pilot study

PubMed Central

Broi, Michele G Da; Rocha Junior, Carlos V; Meola, Juliana; Martins, Wellington P; Carvalho, Filomena M; Ferriani, Rui A; Navarro, Paula A

2017-01-01

Objective Alterations in endometrial receptivity may be involved in the etiopathogenesis of endometriosis-related infertility. The literature has suggested that patients with endometriosis present progestin resistance, which could affect embryo implantation. We question the presence of alterations in the expression of the progesterone receptor gene (PGR) and the genes related to endometrium-embryo interaction regulated by progesterone. This pilot study compared the expression of PGR, HBEGF, ITGAV, ITGB3, and SPP1 genes in eutopic endometrium during the implantation window (IW) in infertile women with endometriosis with that observed in the endometrium of fertile and infertile controls. Methods In this prospective case-control study, endometrial biopsies were performed during the IW in patients aged between 18 and 45 years old, with regular cycles and without endocrine/systemic dysfunctions, divided into endometriosis (END), infertile control (IC) and fertile control (FC) groups. Total RNA extraction, cDNA synthesis, and gene expression analysis by Real-Time PCR were performed. We assessed the size of the difference that our series was powered to detect. Results From the 687 patients who underwent diagnostic videolaparoscopy or tubal ligation at the University Hospital, 130 were eligible. Of these, 32 had endometrial samples collected, with 17 confirmed in the IW. Fifteen samples (5 END, 5 IC and 5 FC) were analyzed. There was no significant difference in the expression of any studied gene. Our sample size allowed us to identify or discard large differences (two standard deviations) among the groups. Conclusion Endometriosis doesn't cause large changes in the endometrial expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 during the IW. PMID:28837027

Fc receptor-targeting of immunogen as a strategy for enhanced antigen loading, vaccination, and protection using intranasally administered antigen-pulsed dendritic cells.

PubMed

Pham, Giang H; Iglesias, Bibiana V; Gosselin, Edmund J

2014-09-08

Dendritic cells (DCs) play a critical role in the generation of adaptive immunity via the efficient capture, processing, and presentation of antigen (Ag) to naïve T cells. Administration of Ag-pulsed DCs is also an effective strategy for enhancing immunity to tumors and infectious disease organisms. Studies have also demonstrated that targeting Ags to Fcγ receptors (FcγR) on Ag presenting cells can enhance humoral and cellular immunity in vitro and in vivo. Specifically, our studies using a Francisella tularensis (Ft) infectious disease vaccine model have demonstrated that targeting immunogens to FcγR via intranasal (i.n.) administration of monoclonal antibody (mAb)-inactivated Ft (iFt) immune complexes (ICs) enhances protection against Ft challenge. Ft is the causative agent of tularemia, a debilitating disease of humans and other mammals and a category A biothreat agent for which there is no approved vaccine. Therefore, using iFt Ag as a model immunogen, we sought to determine if ex vivo targeting of iFt to FcγR on DCs would enhance the potency of i.n. administered iFt-pulsed DCs. In this study, bone marrow-derived DCs (BMDCs) were pulsed ex vivo with iFt or mAb-iFt ICs. Intranasal administration of mAb-iFt-pulsed BMDCs enhanced humoral and cellular immune responses, as well as protection against Ft live vaccine strain (LVS) challenge. Increased protection correlated with increased iFt loading on the BMDC surface as a consequence of FcγR-targeting. However, the inhibitory FcγRIIB had no impact on this enhancement. In conclusion, targeting Ag ex vivo to FcγR on DCs provides a method for enhanced Ag loading of DCs ex vivo, thereby reducing the amount of Ag required, while also avoiding the inhibitory impact of FcγRIIB. Thus, this represents a simple and less invasive strategy for increasing the potency of ex vivo-pulsed DC vaccines against chronic infectious diseases and cancer. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fc Receptor-Targeting of Immunogen as a Strategy for Enhanced Antigen Loading, Vaccination, and Protection Using Intranasally-Administered Antigen-Pulsed Dendritic Cells

PubMed Central

Pham, Giang H.; Iglesias, Bibiana V.; Gosselin, Edmund J.

2014-01-01

Dendritic cells (DCs) play a critical role in the generation of adaptive immunity via the efficient capture, processing, and presentation of antigen (Ag) to naïve T cells. Administration of Ag-pulsed DCs is also an effective strategy for enhancing immunity to tumors and infectious disease organisms. Studies have also demonstrated that targeting Ags to Fcγ receptors (FcγR) on Ag presenting cells can enhance humoral and cellular immunity in vitro and in vivo. Specifically, our studies using an F. tularensis (Ft) infectious disease vaccine model have demonstrated that targeting immunogens to FcγR via intranasal (i.n.) administration of monoclonal antibody (mAb)-inactivated Ft (iFt) immune complexes (ICs) enhances protection against Ft challenge. Ft is the causative agent of tularemia, a debilitating disease of humans and other mammals and a category A biothreat agent for which there is no approved vaccine. Therefore, using iFt Ag as a model immunogen, we sought to determine if ex vivo targeting of iFt to FcγR on DCs would enhance the potency of i.n. administered iFt-pulsed DCs. In this study, bone marrow-derived DCs (BMDCs) were pulsed ex vivo with iFt or mAb-iFt ICs. Intranasal administration of mAb-iFt-pulsed BMDCs enhanced humoral and cellular immune responses, as well as protection against Ft live vaccine strain (LVS) challenge. Increased protection correlated with increased iFt loading on the BMDC surface as a consequence of FcγR targeting. However, the inhibitory FcγRIIB had no impact on this enhancement. In conclusion, targeting Ag ex vivo to FcγR on DCs provides a method for enhanced Ag loading of DCs ex vivo, thereby reducing the amount of Ag required, while also avoiding the inhibitory impact of FcγRIIB. Thus, this represents a simple and less invasive strategy for increasing the potency of ex vivo-pulsed DC vaccines against chronic infectious diseases and cancer. PMID:25068496

Selective expression of inhibitory Fcgamma receptor by metastatic melanoma impairs tumor susceptibility to IgG-dependent cellular response.

PubMed

Cassard, Lydie; Cohen-Solal, Joel F G; Fournier, Emilie M; Camilleri-Broët, Sophie; Spatz, Alain; Chouaïb, Salem; Badoual, Cécile; Varin, Audrey; Fisson, Sylvain; Duvillard, Pierre; Boix, Charlotte; Loncar, Shannon M; Sastre-Garau, Xavier; Houghton, Alan N; Avril, Marie-Françoise; Gresser, Ion; Fridman, Wolf H; Sautès-Fridman, Catherine

2008-12-15

During melanoma progression, patients develop anti-tumor immunity including the production of anti-tumor antibodies. Although the strategies developed by malignant cells to escape anti-tumor cellular immunity have been extensively investigated, little is known about tumor resistance to humoral immunity. The main effect of IgG antibodies is to activate the immune response by binding to host Fc gamma receptors (FcgammaR) expressed by immune cells. We previously reported in a limited study that some human metastatic melanoma cells ectopically express the FcgammaRIIB1, an inhibitory isoform of FcgammaR. By analyzing a large panel of different types of human primary and metastatic solid tumors, we report herein that expression of FcgammaRIIB is restricted to melanoma and is acquired during tumor progression. We show that FcgammaRIIB expression prevents the lysis of human metastatic melanoma cells by NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC) in vitro, independently of the intracytoplasmic region of FcgammaRIIB. Using experimental mouse models, we demonstrate that expression of FcgammaRIIB protects B16F0 melanoma tumors from the ADCC induced by monoclonal and polyclonal anti-tumor IgG in vivo. Thus, our results identify FcgammaRIIB as a marker of human metastatic melanoma that impairs the tumor susceptibility to FcgammaR-dependent innate effector responses. (c) 2008 Wiley-Liss, Inc.

Csf1r-mApple Transgene Expression and Ligand Binding In Vivo Reveal Dynamics of CSF1R Expression within the Mononuclear Phagocyte System.

PubMed

Hawley, Catherine A; Rojo, Rocio; Raper, Anna; Sauter, Kristin A; Lisowski, Zofia M; Grabert, Kathleen; Bain, Calum C; Davis, Gemma M; Louwe, Pieter A; Ostrowski, Michael C; Hume, David A; Pridans, Clare; Jenkins, Stephen J

2018-03-15

CSF1 is the primary growth factor controlling macrophage numbers, but whether expression of the CSF1 receptor differs between discrete populations of mononuclear phagocytes remains unclear. We have generated a Csf1r -mApple transgenic fluorescent reporter mouse that, in combination with lineage tracing, Alexa Fluor 647-labeled CSF1-Fc and CSF1, and a modified Δ Csf1- enhanced cyan fluorescent protein (ECFP) transgene that lacks a 150 bp segment of the distal promoter, we have used to dissect the differentiation and CSF1 responsiveness of mononuclear phagocyte populations in situ. Consistent with previous Csf1r- driven reporter lines, Csf1r -mApple was expressed in blood monocytes and at higher levels in tissue macrophages, and was readily detectable in whole mounts or with multiphoton microscopy. In the liver and peritoneal cavity, uptake of labeled CSF1 largely reflected transgene expression, with greater receptor activity in mature macrophages than monocytes and tissue-specific expression in conventional dendritic cells. However, CSF1 uptake also differed between subsets of monocytes and discrete populations of tissue macrophages, which in macrophages correlated with their level of dependence on CSF1 receptor signaling for survival rather than degree of transgene expression. A double Δ Csf1r -ECFP- Csf1r -mApple transgenic mouse distinguished subpopulations of microglia in the brain, and permitted imaging of interstitial macrophages distinct from alveolar macrophages, and pulmonary monocytes and conventional dendritic cells. The Csf1r- mApple mice and fluorescently labeled CSF1 will be valuable resources for the study of macrophage and CSF1 biology, which are compatible with existing EGFP-based reporter lines. Copyright © 2018 The Authors.

Targeting multiple types of tumors using NKG2D-coated iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Wu, Ming-Ru; Cook, W. James; Zhang, Tong; Sentman, Charles L.

2014-11-01

Iron oxide nanoparticles (IONPs) hold great potential for cancer therapy. Actively targeting IONPs to tumor cells can further increase therapeutic efficacy and decrease off-target side effects. To target tumor cells, a natural killer (NK) cell activating receptor, NKG2D, was utilized to develop pan-tumor targeting IONPs. NKG2D ligands are expressed on many tumor types and its ligands are not found on most normal tissues under steady state conditions. The data showed that mouse and human fragment crystallizable (Fc)-fusion NKG2D (Fc-NKG2D) coated IONPs (NKG2D/NPs) can target multiple NKG2D ligand positive tumor types in vitro in a dose dependent manner by magnetic cell sorting. Tumor targeting effect was robust even under a very low tumor cell to normal cell ratio and targeting efficiency correlated with NKG2D ligand expression level on tumor cells. Furthermore, the magnetic separation platform utilized to test NKG2D/NP specificity has the potential to be developed into high throughput screening strategies to identify ideal fusion proteins or antibodies for targeting IONPs. In conclusion, NKG2D/NPs can be used to target multiple tumor types and magnetic separation platform can facilitate the proof-of-concept phase of tumor targeting IONP development.

Innate transcriptional effects by adjuvants on the magnitude, quality, and durability of HIV envelope responses in NHPs.

PubMed

Francica, Joseph R; Zak, Daniel E; Linde, Caitlyn; Siena, Emilio; Johnson, Carrie; Juraska, Michal; Yates, Nicole L; Gunn, Bronwyn; De Gregorio, Ennio; Flynn, Barbara J; Valiante, Nicholas M; Malyala, Padma; Barnett, Susan W; Sarkar, Pampi; Singh, Manmohan; Jain, Siddhartha; Ackerman, Margaret; Alam, Munir; Ferrari, Guido; Tomaras, Georgia D; O'Hagan, Derek T; Aderem, Alan; Alter, Galit; Seder, Robert A

2017-11-28

Adjuvants have a critical role for improving vaccine efficacy against many pathogens, including HIV. Here, using transcriptional RNA profiling and systems serology, we assessed how distinct innate pathways altered HIV-specific antibody responses in nonhuman primates (NHPs) using 8 clinically based adjuvants. NHPs were immunized with a glycoprotein 140 HIV envelope protein (Env) and insoluble aluminum salts (alum), MF59, or adjuvant nanoemulsion (ANE) coformulated with or without Toll-like receptor 4 (TLR4) and 7 agonists. These were compared with Env administered with polyinosinic-polycytidylic acid:poly-L-lysine, carboxymethylcellulose (pIC:LC) or immune-stimulating complexes. Addition of the TLR4 agonist to alum enhanced upregulation of a set of inflammatory genes, whereas the TLR7 agonist suppressed expression of alum-responsive inflammatory genes and enhanced upregulation of antiviral and interferon (IFN) genes. Moreover, coformulation of the TLR4 or 7 agonists with alum boosted Env-binding titers approximately threefold to 10-fold compared with alum alone, but remarkably did not alter gene expression or enhance antibody titers when formulated with ANE. The hierarchy of adjuvant potency was established after the second of 4 immunizations. In terms of antibody durability, antibody titers decreased ∼10-fold after the final immunization and then remained stable after 65 weeks for all adjuvants. Last, Env-specific Fc-domain glycan structures and a series of antibody effector functions were assessed by systems serology. Antiviral/IFN gene signatures correlated with Fc-receptor binding across all adjuvant groups. This study defines the potency and durability of 8 different clinically based adjuvants in NHPs and shows how specific innate pathways can alter qualitative aspects of Env antibody function.

Identification of pivotal genes and pathways for spinal cord injury via bioinformatics analysis

PubMed Central

Zhu, Zonghao; Shen, Qiang; Zhu, Liang; Wei, Xiaokang

2017-01-01

The present study aimed to identify key genes and pathways associated with spinal cord injury (SCI) and subsequently investigate possible therapeutic targets for the condition. The array data of GSE20907 was downloaded from the Gene Expression Omnibus database and 24 gene chips, including 3-day, 4-day, 1-week, 2-week and 1-month post-SCI together with control propriospinal neurons, were used for the analysis. The raw data was normalized and then the differentially expressed genes (DEGs) in the (A) 2-week post-SCI group vs. control group, (B) 1-month post-SCI group vs. control group, (C) 1-month and 2-week post-SCI group vs. control group, and (D) all post-SCI groups vs. all control groups, were analyzed with a limma package. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses for DEGs were performed. Cluster analysis was performed using ClusterOne plugins. All the DEGs identified were associated with immune and inflammatory responses. Signal transducer and activator of transcription 3 (STAT3), erb-B2 receptor tyrosine kinase 4 (ERBB4) and cytochrome B-245, α polypeptide (CYBA) were in the network diagrams of (A), (C) and (D), respectively. The enrichment analysis of DEGs identified in all samples demonstrated that the DEGs were also enriched in the chemokine signaling pathway (enriched in STAT3) and the high-affinity immunoglobulin E receptor (FcεRI) signaling pathway [enriched in proto-oncogene, src family tyrosine kinase (LYN)]. Immune and inflammatory responses serve significant roles in SCI. STAT3, ERBB4 and CYBA may be key genes associated with SCI at certain stages. Furthermore, STAT3 and LYN may be involved in the development of SCI via the chemokine and FcεRI signaling pathways, respectively. PMID:28731189

Innate transcriptional effects by adjuvants on the magnitude, quality, and durability of HIV envelope responses in NHPs

PubMed Central

Francica, Joseph R.; Zak, Daniel E.; Linde, Caitlyn; Siena, Emilio; Johnson, Carrie; Juraska, Michal; Yates, Nicole L.; Gunn, Bronwyn; De Gregorio, Ennio; Flynn, Barbara J.; Valiante, Nicholas M.; Malyala, Padma; Barnett, Susan W.; Sarkar, Pampi; Singh, Manmohan; Jain, Siddhartha; Ackerman, Margaret; Alam, Munir; Ferrari, Guido; Tomaras, Georgia D.; O’Hagan, Derek T.; Aderem, Alan; Alter, Galit

2017-01-01

Adjuvants have a critical role for improving vaccine efficacy against many pathogens, including HIV. Here, using transcriptional RNA profiling and systems serology, we assessed how distinct innate pathways altered HIV-specific antibody responses in nonhuman primates (NHPs) using 8 clinically based adjuvants. NHPs were immunized with a glycoprotein 140 HIV envelope protein (Env) and insoluble aluminum salts (alum), MF59, or adjuvant nanoemulsion (ANE) coformulated with or without Toll-like receptor 4 (TLR4) and 7 agonists. These were compared with Env administered with polyinosinic-polycytidylic acid:poly-L-lysine, carboxymethylcellulose (pIC:LC) or immune-stimulating complexes. Addition of the TLR4 agonist to alum enhanced upregulation of a set of inflammatory genes, whereas the TLR7 agonist suppressed expression of alum-responsive inflammatory genes and enhanced upregulation of antiviral and interferon (IFN) genes. Moreover, coformulation of the TLR4 or 7 agonists with alum boosted Env-binding titers approximately threefold to 10-fold compared with alum alone, but remarkably did not alter gene expression or enhance antibody titers when formulated with ANE. The hierarchy of adjuvant potency was established after the second of 4 immunizations. In terms of antibody durability, antibody titers decreased ∼10-fold after the final immunization and then remained stable after 65 weeks for all adjuvants. Last, Env-specific Fc-domain glycan structures and a series of antibody effector functions were assessed by systems serology. Antiviral/IFN gene signatures correlated with Fc-receptor binding across all adjuvant groups. This study defines the potency and durability of 8 different clinically based adjuvants in NHPs and shows how specific innate pathways can alter qualitative aspects of Env antibody function. PMID:29296883

K-RAS GTPase- and B-RAF kinase-mediated T-cell tolerance defects in rheumatoid arthritis.

PubMed

Singh, Karnail; Deshpande, Pratima; Li, Guangjin; Yu, Mingcan; Pryshchep, Sergey; Cavanagh, Mary; Weyand, Cornelia M; Goronzy, Jörg J

2012-06-19

Autoantibodies to common autoantigens and neoantigens, such as IgG Fc and citrullinated peptides, are immunological hallmarks of rheumatoid arthritis (RA). We examined whether a failure in maintaining tolerance is mediated by defects in T-cell receptor activation threshold settings. RA T cells responded to stimulation with significantly higher ERK phosphorylation (P < 0.001). Gene expression arrays of ERK pathway members suggested a higher expression of KRAS and BRAF, which was confirmed by quantitative PCR (P = 0.003), Western blot, and flow cytometry (P < 0.01). Partial silencing of KRAS and BRAF lowered activation-induced phosphorylated ERK levels (P < 0.01). In individual cells, levels of these signaling molecules correlated with ERK phosphorylation, attesting that their concentrations are functionally important. In confocal studies, B-RAF/K-RAS clustering was increased in RA T cells 2 min after T-cell receptor stimulation (P < 0.001). Overexpression of B-RAF and K-RAS in normal CD4 T cells amplified polyclonal T-cell proliferation and facilitated responses to citrullinated peptides. We propose that increased expression of B-RAF and K-RAS lowers T-cell activation thresholds in RA T cells, enabling responses to autoantigens.

Combined treatment, based on lysomustine administration with mesenchymal stem cells expressing cytosine deaminase therapy, leads to pronounced murine Lewis lung carcinoma growth inhibition.

PubMed

Krassikova, Lyudmila S; Karshieva, Saida S; Cheglakov, Ivan B; Belyavsky, Alexander V

2016-09-01

The combination of stem cell-based gene therapy with chemotherapy comprises an advantageous strategy that results in a reduction of system toxicity effects and an improvement in the general efficacy of treatment. In the present study, we estimated the efficacy of adipose tissue-derived mesenchymal stem cells (AT-MSCs) expressing cytosine deaminase (CDA) combined with lysomustine chemotherapy in mice bearing late stage Lewis lung carcinoma (LLC). Adipose tissue-derived mesenchymal stem cells were transfected with non-insert plasmid construct transiently expressing fused cytosine deaminase-uracil phosphoribosyltransferase protein (CDA/UPRT) or the same construct fused with Herpes Simplex Virus Type1 tegument protein VP22 (CDA/UPRT/VP22). Systemic administration of 5-fluorocytosine (5FC) and lysomustine was implemented after a single intratumoral injection of transfected AT-MSCs. We demonstrated that direct intratumoral transplantation of AT-MSCs expressing CDA/UPRT or CDA/UPRT/VP22 followed by systemic administration of 5FC resulted in a significant tumor growth inhibition. There was a 56% reduction in tumor volume in mice treated by AT-MSCs-CDA/UPRT + 5FC or with AT-MSCs-CDA/UPRT/VP22 + 5FC compared to control animals grafted with lung carcinoma alone. Transplantation of AT-MSCs-CDA/UPRT + 5FC and AT-MSCs-CDA/UPRT/VP22 + 5FC prolonged the life span of mice bearing LLC by 27% and 31%, respectively. Co-administration of lysomustine and AT-MSCs-CDA/UPRT + 5FC led to tumor growth inhibition (by 86%) and life span extension (by 60%) compared to the control group. Our data indicate that a combination CDA/UPRT-expressing AT-MSCs with lysomustine has a superior antitumor effect in the murine lung carcinoma model compared to monotherapies with transfected AT-MSCs or lysomustine alone, possibly because of a synergistic effect of the combination therapy. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Targeting nanosystems to human DCs via Fc receptor as an effective strategy to deliver antigen for immunotherapy.

PubMed

Cruz, Luis J; Rueda, Felix; Cordobilla, Begoña; Simón, Lorena; Hosta, Leticia; Albericio, Fernando; Domingo, Joan Carles

2011-02-07

Dendritic cells (DCs) are increasingly being explored as cellular vaccines for tumor immunotherapy, since they provide an effective system of antigen presentation both in vitro and in vivo. An additional advantage of this cell type is that it is possible to target specific antigens through the activation of receptors, such as FcR (the receptor for the IgG Fc fragment) and TLR (toll-like Receptor). Thus, the uptake capacity of DCs can be improved, thereby increasing antigen presentation. This, in turn, would lead to an enhanced immune response, and, in some instances, the tolerance/anergy of immune effector cells present in cancer patients could be reverted. Here we studied various nanotargeting systems, including liposomes and gold nanoparticles of a peptide-based immunotherapeutic vaccine for the treatment of androgen-responsive prostate cancer. Building blocks of the immunogenic peptide consisted of the luteinizing hormone-releasing hormone (LHRH), also known as gonadotropin-releasing hormone (GnRH) peptide (B- and T-cell epitope), in tandem with a T-helper epitope corresponding to the 830-844 region of tetanus toxoid. Three new peptides with several modifications at the N-terminal (palmitoyl, acetyl, and FITC) were synthesized. These peptides also contained a Cys as C-terminal residue to facilitate grafting onto gold nanoparticles. To target different antigen formulations to human DCs, the Fc was activated with a cross-linking spacer to generate a free thiol group and thus facilitate conjugation onto gold nanoparticles, liposomes, and peptide. Our results show that gold nanoparticles and liposomes targeted to FcRs of human DCs are effective antigen delivery carriers and induce a strong immune response with respect to nontargeted LHRH-TT-nanoparticle conjugates and a superior response to that of naked antigens. In addition, dual labeling using gold and FITC-peptide allowed DC tracking by flow cytometry as well as transmission electron microscopy. Nanoparticles were observed to show a homogeneous distribution throughout the cytoplasm. These results open up a new approach to the development of a novel strategy for cancer vaccines.

IL-6 promotes an increase in human mast cell numbers and reactivity through suppression of suppressor of cytokine signaling 3.

PubMed

Desai, Avanti; Jung, Mi-Yeon; Olivera, Ana; Gilfillan, Alasdair M; Prussin, Calman; Kirshenbaum, Arnold S; Beaven, Michael A; Metcalfe, Dean D

2016-06-01

IL-6, levels of which are reported to be increased in association with mastocytosis, asthma, and urticaria, is used in conjunction with stem cell factor to generate CD34(+) cell-derived primary human mast cell (HuMC) cultures. Despite these associations, the effects on and mechanisms by which prolonged exposure to IL-6 alters HuMC numbers and function are not well understood. We sought to study the effect of IL-6 on HuMC function, the mechanisms by which IL-6 exerts its effects, and the relationship of these findings to mastocytosis. HuMCs were cultured in stem cell factor with or without IL-6. Responses to FcεRI aggregation and expression of proteases and receptors, including the soluble IL-6 receptor (sIL-6R), were then quantitated. Epigenetic changes in suppressor of cytokine signaling 3 (SOCS3) were determined by using methylation-specific PCR. Serum samples from healthy control subjects and patients with mastocytosis were assayed for IL-6, tryptase, and sIL-6R. IL-6 enhanced mast cell (MC) proliferation, maturation, and reactivity after FcεRI aggregation. IL-6 reduced expression of SOCS3, which correlated with methylation of the SOCS3 promoter and increased expression and activation of signal transducer and activator of transcription 3. IL-6 also suppressed constitutive production of sIL-6R, and serum levels of sIL-6R were similarly reduced in patients with mastocytosis. IL-6 increases MC proliferation and formation of a more reactive phenotype enabled by suppressing proteolytic cleavage of sIL-6R from IL-6R and downregulation of the SOCS3 autoinhibitory pathway. We suggest IL-6 blockade might ameliorate MC-related symptoms and pathology in patients with MC-related diseases associated with increased IL-6 levels, including mastocytosis. Published by Elsevier Inc.

CD200Fc reduces LPS-induced IL-1β activation in human cervical cancer cells by modulating TLR4-NF-κB and NLRP3 inflammasome pathway.

PubMed

He, Aiqin; Shao, Jia; Zhang, Yu; Lu, Hong; Wu, Zhijun; Xu, Yunzhao

2017-05-16

Chronic inflammation plays an important role in tumorigenesis of cervical cancer. CD200Fc, a CD200R1 agonist, has been found to have anti-inflammatory effects in autoimmune diseases and neuro-degeneration. However, the anti-inflammatory effect of CD200Fc on cervical cancer has not yet to be completely understood. This study investigated the anti-inflammatory effects and mechanisms of CD200Fc in LPS-induced human SiHa cells and Caski cells. SiHa cells and Caski cells were stimulated with 40 μg/ml LPS under different concentrations of CD200Fc for 90 min or 12 hours. The mRNA and protein levels of pro-IL-1β, cleaved-IL-1β and NLRP3, as well as the protein level of cleaved caspase-1, were significantly increased in LPS-induced SiHa cells and Caski cells. LPS stimulation did not change ASC and pro-caspase-1 expression. CD200Fc down-regulated protein expression of cleaved caspase-1 and mRNA and protein expression of pro-IL-1β, cleaved-IL-1β and NLRP3. In addition, the protein levels of TLR4, p-P65 and p-IκB, as well as the translocation of P65 to nucleus, were significantly increased in LPS-induced SiHa cells and Caski cells. LPS stimulation did not change t-P65 and t-IκB on protein levels, which were components of TLR-NF-κB pathway. CD200Fc down-regulated protein expression of TLR4, p-P65 and p-IκB and inhibited the translocation of P65 to nucleus in LPS-induced SiHa cells and Caski cells. These results indicated that CD200Fc appeared to suppress the inflammatory activity of TLR4-NF-κB and NLRP3 inflammasome pathway in LPS-induced SiHa cells and Caski cells. It provided novel mechanistic insights into the potential therapeutic uses of CD200Fc for cervical cancer.

Tonsil Epithelial Factors May Influence Oropharyngeal Human Immunodeficiency Virus Transmission

PubMed Central

Moutsopoulos, Niki M.; Nares, Salvador; Nikitakis, Nikolaos; Rangel, Zoila; Wen, Jie; Munson, Peter; Sauk, John; Wahl, Sharon M.

2007-01-01

Tonsil epithelium has been implicated in human immunodeficiency virus (HIV) pathogenesis, but its role in oral transmission remains controversial. To study characteristics of this tissue, which may influence susceptibility or resistance to HIV, we performed microarray analysis of the tonsil epithelium. Our data revealed that genes related to immune functions such as antibody production and antigen processing were increasingly expressed in tonsil compared with the epithelium of another oropharyngeal site, the gingival epithelium. Importantly, tonsil epithelium highly expressed genes associated with HIV entrapment and/or transmission, including the HIV co-receptor CXCR4 and the potential HIV-binding molecules FcRγIII, complement receptor 2, and various complement components. Immunohistochemical staining confirmed the increased presence of CXCR4 in the tonsil epithelium compared with multiple oral epithelial sites, particularly in basal and parabasal layers. This increased expression of molecules involved in viral recognition, binding, and entry may favor virus-epithelium interactions in an environment with reduced innate antiviral mechanisms. Specifically, secretory leukocyte protease inhibitor, an innate molecule with anti-HIV activity, was minimal in the tonsil epithelium, in contrast to oral mucosa. Collectively, our data suggest that increased expression of molecules associated with HIV binding and entry coupled with decreased innate antiviral factors may render the tonsil a potential site for oral transmission. PMID:17620369

Cloning, characterization, and expression analysis of the DEAD-box family genes, Fc-vasa and Fc-PL10a, in Chinese shrimp ( Fenneropenaeus chinensis)

NASA Astrophysics Data System (ADS)

Zhou, Qianru; Shao, Mingyu; Qin, Zhenkui; Kyoung, Ho Kang; Zhang, Zhifeng

2010-01-01

RNA helicases of the DEAD-box and related families are involved in various cellular processes including DNA replication, DNA repair, and RNA processing. However, the function of DEAD-box proteins in aquaculture species is poorly understood at molecular level. We obtained the full-length cDNA sequences of two genes encoding helicase-related proteins, Fc-vasa and Fc-PL10a, from the testes of Chinese shrimp, Fenneropenaeus chinensis. The two predicted amino acid sequences contain all the conserved motifs characterized by the DEAD-box family and several RGG repeats in the N-terminal regions. Homology and phylogenetic analyses indicate that they belong to the vasa and PL10 subfamilies. The three-dimensional structures of the two proteins were predicted with a homology modeling approach. Both core proteins consist of two tandem RecA-like domains similar to those of the DEAD-box RNA helicase. Using reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR we found that Fc-vasa was expressed specifically in the adult gonads. Transcription decreased in the ovary but increased in the testis during gonadal development. Fc-PL10a expression was widely distributed in the tissues we examined. Using in situ hybridization, we demonstrated that the Fc-vasa transcript is localized to the cytoplasm of the spermatogonia and oocytes. Thus, our results suggest that Fc-vasa plays an important role in germ-line development, and has utility as a germ cell lineage marker which will help to generate new insight into the origin and differentiation of germ cells as well as the regulation of reproduction in F. chinensis.

Use of Fc-Engineered Antibodies as Clearing Agents to Increase Contrast During PET

PubMed Central

Swiercz, Rafal; Chiguru, Srinivas; Tahmasbi, Amir; Ramezani, Saleh M.; Hao, Guiyang; Challa, Dilip K.; Lewis, Matthew A.; Kulkarni, Padmakar V.; Sun, Xiankai; Ober, Raimund J.; Mason, Ralph P.; Ward, E. Sally

2015-01-01

Despite promise for the use of antibodies as molecular imaging agents in PET, their long in vivo half-lives result in poor contrast and radiation damage to normal tissue. This study describes an approach to overcome these limitations. Methods Mice bearing human epidermal growth factor receptor type 2 (HER2)–overexpressing tumors were injected with radiolabeled (124I, 125I) HER2-specific antibody (pertuzumab). Pertuzumab injection was followed 8 h later by the delivery of an engineered, antibody-based inhibitor of the receptor, FcRn. Biodistribution analyses and PET were performed at 24 and 48 h after pertuzumab injection. Results The delivery of the engineered, antibody-based FcRn inhibitor (or Abdeg, for antibody that enhances IgG degradation) results in improved tumor-to-blood ratios, reduced systemic exposure to radiolabel, and increased contrast during PET. Conclusion Abdegs have considerable potential as agents to stringently regulate antibody dynamics in vivo, resulting in increased contrast during molecular imaging with PET. PMID:24868106

Antibodies to watch in 2014.

PubMed

Reichert, Janice M

2014-01-01

Since 2010, mAbs has documented the biopharmaceutical industry's progress in transitioning antibody therapeutics to first Phase 3 clinical studies and regulatory review, and its success at gaining first marketing approvals for antibody-based products. This installment of the "Antibodies to watch" series outlines events anticipated to occur between December 2013 and the end of 2014, including first regulatory actions on marketing applications for vedolizumab, siltuximab, and ramucirumab, as well as the Fc fusion proteins Factor IX-Fc and Factor VIII-Fc; and the submission of first marketing applications for up to five therapeutics (secukinumab, ch14.18, onartuzumab, necitumumab, gevokizumab). Antibody therapeutics in Phase 3 studies are described, with an emphasis on those with study completion dates in 2014, including antibodies targeting interleukin-17a or the interleukin-17a receptor (secukinumab, ixekizumab, brodalumab), proprotein convertase subtilisin/kexin type 9 (alirocumab, evolocumab, bococizumab), and programmed death 1 receptor (lambrolizumab, nivolumab). Five antibodies with US Food and Drug Administration's Breakthrough Therapy designation (obinutuzumab, ofatumumab, lambrolizumab, bimagrumab, daratumumab) are also discussed.

Antibodies to watch in 2014

PubMed Central

Reichert, Janice M

2014-01-01

Since 2010, mAbs has documented the biopharmaceutical industry’s progress in transitioning antibody therapeutics to first Phase 3 clinical studies and regulatory review, and its success at gaining first marketing approvals for antibody-based products. This installment of the “Antibodies to watch” series outlines events anticipated to occur between December 2013 and the end of 2014, including first regulatory actions on marketing applications for vedolizumab, siltuximab, and ramucirumab, as well as the Fc fusion proteins Factor IX-Fc and Factor VIII-Fc; and the submission of first marketing applications for up to five therapeutics (secukinumab, ch14.18, onartuzumab, necitumumab, gevokizumab). Antibody therapeutics in Phase 3 studies are described, with an emphasis on those with study completion dates in 2014, including antibodies targeting interleukin-17a or the interleukin-17a receptor (secukinumab, ixekizumab, brodalumab), proprotein convertase subtilisin/kexin type 9 (alirocumab, evolocumab, bococizumab), and programmed death 1 receptor (lambrolizumab, nivolumab). Five antibodies with US Food and Drug Administration’s Breakthrough Therapy designation (obinutuzumab, ofatumumab, lambrolizumab, bimagrumab, daratumumab) are also discussed. PMID:24284914

Teratogenicity induced by targeting a placental immunoglobulin transporter

PubMed Central

Kolonin, Mikhail G.; Pasqualini, Renata; Arap, Wadih

2002-01-01

Approximately 3% of children in developed countries are born with nongenetic birth defects. However, the nature and mechanisms of teratogenesis are poorly understood. We investigated mechanisms of teratogen-mediated blockade of maternofetal transport by screening a combinatorial library for peptides that bind nonendothelial placental vasculature in pregnant mice. Here, we identified a peptide motif, TPKTSVT, that homes to the yolk sac, induces placental necrosis, and disrupts embryo development. We show that TPKTSVT promotes transcytosis of phage into the embryo and blocks the transplacental transport of immunoglobulins. Based on these data, we propose a model in which TPKTSVT targets a placental Fc receptor. Absence of TPKTSVT placental homing in mice lacking β2-microglobulin (β2m) suggests FcRn/β2m as a target for the TPKTSVT, which is unexpected, given the normal development of FcRn/β2m-deficient progeny. High-throughput screening for embryotoxins that target placental receptors could be developed to systematically identify and avoid exposure to teratogenic drugs. PMID:12242328

Attenuation of HIV-associated human B cell exhaustion by siRNA downregulation of inhibitory receptors

PubMed Central

Kardava, Lela; Moir, Susan; Wang, Wei; Ho, Jason; Buckner, Clarisa M.; Posada, Jacqueline G.; O’Shea, Marie A.; Roby, Gregg; Chen, Jenny; Sohn, Hae Won; Chun, Tae-Wook; Pierce, Susan K.; Fauci, Anthony S.

2011-01-01

Chronic immune activation in HIV-infected individuals leads to accumulation of exhausted tissue-like memory B cells. Exhausted lymphocytes display increased expression of multiple inhibitory receptors, which may contribute to the inefficiency of HIV-specific antibody responses. Here, we show that downregulation of B cell inhibitory receptors in primary human B cells led to increased tissue-like memory B cell proliferation and responsiveness against HIV. In human B cells, siRNA knockdown of 9 known and putative B cell inhibitory receptors led to enhanced B cell receptor–mediated (BCR-mediated) proliferation of tissue-like memory but not other B cell subpopulations. The strongest effects were observed with the putative inhibitory receptors Fc receptor–like–4 (FCRL4) and sialic acid–binding Ig-like lectin 6 (Siglec-6). Inhibitory receptor downregulation also led to increased levels of HIV-specific antibody-secreting cells and B cell–associated chemokines and cytokines. The absence of known ligands for FCRL4 and Siglec-6 suggests these receptors may regulate BCR signaling through their own constitutive or tonic signaling. Furthermore, the extent of FCLR4 knockdown effects on BCR-mediated proliferation varied depending on the costimulatory ligand, suggesting that inhibitory receptors may engage specific pathways in inhibiting B cell proliferation. These findings on HIV-associated B cell exhaustion define potential targets for reversing the deleterious effect of inhibitory receptors on immune responses against persistent viral infections. PMID:21633172

Age-related differences in event-related potentials for early visual processing of emotional faces.

PubMed

Hilimire, Matthew R; Mienaltowski, Andrew; Blanchard-Fields, Fredda; Corballis, Paul M

2014-07-01

With advancing age, processing resources are shifted away from negative emotional stimuli and toward positive ones. Here, we explored this 'positivity effect' using event-related potentials (ERPs). Participants identified the presence or absence of a visual probe that appeared over photographs of emotional faces. The ERPs elicited by the onsets of angry, sad, happy and neutral faces were recorded. We examined the frontocentral emotional positivity (FcEP), which is defined as a positive deflection in the waveforms elicited by emotional expressions relative to neutral faces early on in the time course of the ERP. The FcEP is thought to reflect enhanced early processing of emotional expressions. The results show that within the first 130 ms young adults show an FcEP to negative emotional expressions, whereas older adults show an FcEP to positive emotional expressions. These findings provide additional evidence that the age-related positivity effect in emotion processing can be traced to automatic processes that are evident very early in the processing of emotional facial expressions. © The Author (2013). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

High prevalence of dengue antibodies and the arginine variant of the FcγRIIa polymorphism in asymptomatic individuals in a population of Minas Gerais State, Southeast Brazil.

PubMed

Pereira, Anna Carolina Toledo da Cunha; de Siqueira, Tatiane Ribeiro; de Oliveira Prado, Andressa Anunciação; da Silva, Camila Almeida Veiga; de Fátima Silva Moraes, Thaís; Aleixo, Alan Alex; de Magalhaes, José Carlos; de Souza, Gabriel Augusto Pires; Drumond, Betânia Paiva; Ferreira, Gustavo Portela; de Mello Silva, Breno; de Brito Magalhães, Cintia Lopes; Santos, Luciana Lara; Ferreira, Jaqueline Maria Siqueira; Malaquias, Luiz Cosme Cotta; Coelho, Luiz Felipe Leomil

2018-06-01

Dengue is the most prevalent arthropod-borne viral illness in humans worldwide. Single-nucleotide polymorphisms (SNPs) in genes involved in the immune response, such as dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN), IgG Fc receptor II-A (FcγRIIa), vitamin D receptor (VDR), and tumor necrosis factor alpha (TNF-α), were previously reported to be associated with susceptibility to dengue disease in different human populations. Therefore, due to the relevant association of host immune and genetic status with disease susceptibility/severity of dengue, this work aims to verify the frequency of anti-dengue virus antibodies and some dengue-associated risk SNPs in a population in Minas Gerais State, Southeast Brazil. A total of 1560 individuals were genotyped for polymorphisms in DC-SIGN (rs4804803), FcγRIIa (rs1801274), VDR (rs7975232), and TNF-α (rs1800629). The presence of anti-dengue antibodies (IgM and/or IgG) in these samples was also assayed. Anti-dengue antibodies were detected at an overall frequency of 16.86%, indicating a virus infection in asymptomatic individuals. The genotypic frequencies of all SNPs studied did not differ between the asymptomatic and control groups. Regarding the allelic frequencies of the four SNPs analyzed, a higher frequency was detected of the G allele of FcγRIIa/rs1801274 in the asymptomatic individuals when compared to that in the control group (p = 0.03). Therefore, the results showed a high prevalence of asymptomatic individuals in Minas Gerais State, with a potential association between the presence of the G allele of FcγRIIa/rs1801274 and protection against symptomatic disease.

Antibody-dependent cellular cytotoxicity and cytokine/chemokine secretion by KHYG-1 cells stably expressing FcγRIIIA.

PubMed

Kobayashi, Eiji; Motoi, Sotaro; Sugiura, Masahito; Kajikawa, Masunori; Kojima, Shuji; Kohroki, Junya; Masuho, Yasuhiko

2014-09-01

Antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer (NK) cells is a major mechanism of tumor therapy with antibodies. NK cells not only manifest cytotoxicity but also secrete a variety of cytokines/chemokines that regulate immune responses. Using a retroviral vector, in this study we established a KHYG-1 cell line that stably expresses FcγRIIIA (CD16A). The KHYG-1/FcγRIIIA cells exerted potent antibody concentration-dependent ADCC, whereas parental KHYG-1 cells did not. In contrast, without antibody, the natural killer activity of KHYG-1/FcγRIIIA cells was less potent than that of parental KHYG-1 cells. During the course of ADCC, KHYG-1/FcγRIIIA cells secreted IFN-γ and MIP-1α dependent upon antibody concentration, but parental KHYG-1 cells did not. These results suggest that KHYG-1/FcγRIIIA cells would be useful in studies to elucidate the function of NK cells and the mechanism of ADCC. Copyright © 2014 Elsevier B.V. All rights reserved.

Visualization of protein interactions in living Drosophila embryos by the bimolecular fluorescence complementation assay.

PubMed

Hudry, Bruno; Viala, Séverine; Graba, Yacine; Merabet, Samir

2011-01-28

Protein interactions control the regulatory networks underlying developmental processes. The understanding of developmental complexity will, therefore, require the characterization of protein interactions within their proper environment. The bimolecular fluorescence complementation (BiFC) technology offers this possibility as it enables the direct visualization of protein interactions in living cells. However, its potential has rarely been applied in embryos of animal model organisms and was only performed under transient protein expression levels. Using a Hox protein partnership as a test case, we investigated the suitability of BiFC for the study of protein interactions in the living Drosophila embryo. Importantly, all BiFC parameters were established with constructs that were stably expressed under the control of endogenous promoters. Under these physiological conditions, we showed that BiFC is specific and sensitive enough to analyse dynamic protein interactions. We next used BiFC in a candidate interaction screen, which led to the identification of several Hox protein partners. Our results establish the general suitability of BiFC for revealing and studying protein interactions in their physiological context during the rapid course of Drosophila embryonic development.

Mas-related G protein coupled receptor-X2: A potential new target for modulating mast cell-mediated allergic and inflammatory diseases.

PubMed

Ali, Hydar

2016-12-01

Mast cells (MCs) are tissue resident immune cells that are best known for their roles in allergic and inflammatory diseases. In addition to the high affinity IgE receptor (FcεRI), MCs express numerous G protein coupled receptors (GPCRs), which are the most common targets of drug therapy. Neurokinin 1 receptor (NK-1R) is expressed on MCs and contributes to IgE and non-IgE-mediated responses in mice. Although NK-1R antagonists are highly effective in modulating experimental allergic and inflammatory responses in mice they lack efficacy in humans. This article reviews recent findings that demonstrate that while neuropeptides (NPs) activate murine MCs via NK-1R and Mas related G protein coupled receptor B2 (MrgprB2), they activate human MCs via Mas-related G protein coupled receptor X2 (MRGPRX2). Interestingly, conventional NK-1R antagonists have off-target activity against mouse MrgprB2 but not human MRGPRX2. These findings suggest that the failure to translate studies with NK-1R antagonists from in vivo mouse studies to the clinic likely reflects their lack of effect on human MRGPRX2. A unique feature of MRGPRX2 that distinguishes it from other GPCRs is that it is activated by a diverse group of ligands that include; neuropeptides, cysteine proteases, antimicrobial peptides and cationic proteins released from activated eosinophils. Thus, the development of small molecule MRGPRX2-specific antagonists or neutralizing antibodies may provide new targets for the treatment of MC-mediated allergic and inflammatory diseases.

NRG1-Fc improves metabolic health via dual hepatic and central action.

PubMed

Zhang, Peng; Kuang, Henry; He, Yanlin; Idiga, Sharon O; Li, Siming; Chen, Zhimin; Yang, Zhao; Cai, Xing; Zhang, Kezhong; Potthoff, Matthew J; Xu, Yong; Lin, Jiandie D

2018-03-08

Neuregulins (NRGs) are emerging as an important family of signaling ligands that regulate glucose and lipid homeostasis. NRG1 lowers blood glucose levels in obese mice, whereas the brown fat-enriched secreted factor NRG4 protects mice from high-fat diet-induced insulin resistance and hepatic steatosis. However, the therapeutic potential of NRGs remains elusive, given the poor plasma half-life of the native ligands. Here, we engineered a fusion protein using human NRG1 and the Fc domain of human IgG1 (NRG1-Fc) that exhibited extended half-life in circulation and improved potency in receptor signaling. We evaluated its efficacy in improving metabolic parameters and dissected the mechanisms of action. NRG1-Fc treatment triggered potent AKT activation in the liver, lowered blood glucose, improved insulin sensitivity, and suppressed food intake in obese mice. NRG1-Fc acted as a potent secretagogue for the metabolic hormone FGF21; however, the latter was largely dispensable for its metabolic effects. NRG1-Fc directly targeted the hypothalamic POMC neurons to promote membrane depolarization and increase firing rate. Together, NRG1-Fc exhibits improved pharmacokinetic properties and exerts metabolic benefits through dual inhibition of hepatic gluconeogenesis and caloric intake.

NRG1-Fc improves metabolic health via dual hepatic and central action

PubMed Central

Kuang, Henry; Idiga, Sharon O.; Li, Siming; Chen, Zhimin; Cai, Xing; Zhang, Kezhong; Potthoff, Matthew J.; Xu, Yong; Lin, Jiandie D.

2018-01-01

Neuregulins (NRGs) are emerging as an important family of signaling ligands that regulate glucose and lipid homeostasis. NRG1 lowers blood glucose levels in obese mice, whereas the brown fat–enriched secreted factor NRG4 protects mice from high-fat diet–induced insulin resistance and hepatic steatosis. However, the therapeutic potential of NRGs remains elusive, given the poor plasma half-life of the native ligands. Here, we engineered a fusion protein using human NRG1 and the Fc domain of human IgG1 (NRG1-Fc) that exhibited extended half-life in circulation and improved potency in receptor signaling. We evaluated its efficacy in improving metabolic parameters and dissected the mechanisms of action. NRG1-Fc treatment triggered potent AKT activation in the liver, lowered blood glucose, improved insulin sensitivity, and suppressed food intake in obese mice. NRG1-Fc acted as a potent secretagogue for the metabolic hormone FGF21; however, the latter was largely dispensable for its metabolic effects. NRG1-Fc directly targeted the hypothalamic POMC neurons to promote membrane depolarization and increase firing rate. Together, NRG1-Fc exhibits improved pharmacokinetic properties and exerts metabolic benefits through dual inhibition of hepatic gluconeogenesis and caloric intake. PMID:29515030

Prolonged activity of a recombinant factor VIII-Fc fusion protein in hemophilia A mice and dogs

PubMed Central

Dumont, Jennifer A.; Liu, Tongyao; Low, Susan C.; Zhang, Xin; Kamphaus, George; Sakorafas, Paul; Fraley, Cara; Drager, Douglas; Reidy, Thomas; McCue, Justin; Franck, Helen W. G.; Merricks, Elizabeth P.; Nichols, Timothy C.; Bitonti, Alan J.; Pierce, Glenn F.

2012-01-01

Despite proven benefits, prophylactic treatment for hemophilia A is hampered by the short half-life of factor VIII. A recombinant factor VIII-Fc fusion protein (rFVIIIFc) was constructed to determine the potential for reduced frequency of dosing. rFVIIIFc has an ∼ 2-fold longer half-life than rFVIII in hemophilia A (HemA) mice and dogs. The extension of rFVIIIFc half-life requires interaction of Fc with the neonatal Fc receptor (FcRn). In FcRn knockout mice, the extension of rFVIIIFc half-life is abrogated, and is restored in human FcRn transgenic mice. The Fc fusion has no impact on FVIII-specific activity. rFVIIIFc has comparable acute efficacy as rFVIII in treating tail clip injury in HemA mice, and fully corrects whole blood clotting time (WBCT) in HemA dogs immediately after dosing. Furthermore, consistent with prolonged half-life, rFVIIIFc shows 2-fold longer prophylactic efficacy in protecting HemA mice from tail vein transection bleeding induced 24-48 hours after dosing. In HemA dogs, rFVIIIFc also sustains partial correction of WBCT 1.5- to 2-fold longer than rFVIII. rFVIIIFc was well tolerated in both species. Thus, the rescue of FVIII by Fc fusion to provide prolonged protection presents a novel pathway for FVIII catabolism, and warrants further investigation. PMID:22246033

Scavenger receptor function of mouse Fcγ receptor III contributes to progression of atherosclerosis in apolipoprotein E hyperlipidemic mice.

PubMed

Zhu, Xinmei; Ng, Hang Pong; Lai, Yen-Chun; Craigo, Jodi K; Nagilla, Pruthvi S; Raghani, Pooja; Nagarajan, Shanmugam

2014-09-01

Recent studies showed loss of CD36 or scavenger receptor-AI/II (SR-A) does not ameliorate atherosclerosis in a hyperlipidemic mouse model, suggesting receptors other than CD36 and SR-A may also contribute to atherosclerosis. In this report, we show that apolipoprotein E (apoE)-CD16 double knockout (DKO; apoE-CD16 DKO) mice have reduced atherosclerotic lesions compared with apoE knockout mice. In vivo and in vitro foam cell analyses showed apoE-CD16 DKO macrophages accumulated less neutral lipids. Reduced foam cell formation in apoE-CD16 DKO mice is not due to change in expression of CD36, SR-A, and LOX-1. This led to a hypothesis that CD16 may have scavenger receptor activity. We presented evidence that a soluble form of recombinant mouse CD16 (sCD16) bound to malondialdehyde-modified low-density lipoprotein (MDALDL), and this binding is blocked by molar excess of MDA- modified BSA and anti-MDA mAbs, suggesting CD16 specifically recognizes MDA epitopes. Interestingly, sCD16 inhibited MDALDL binding to macrophage cell line, as well as soluble forms of recombinant mouse CD36, SR-A, and LOX-1, indicating CD16 can cross-block MDALDL binding to other scavenger receptors. Anti-CD16 mAb inhibited immune complex binding to sCD16, whereas it partially inhibited MDALDL binding to sCD16, suggesting MDALDL binding site may be in close proximity to the immune complex binding site in CD16. Loss of CD16 expression resulted in reduced levels of MDALDL-induced proinflammatory cytokine expression. Finally, CD16-deficient macrophages showed reduced MDALDL-induced Syk phosphorylation. Collectively, our findings suggest scavenger receptor activity of CD16 may, in part, contribute to the progression of atherosclerosis. Copyright © 2014 by The American Association of Immunologists, Inc.

Advances in Therapeutic Fc Engineering – Modulation of IgG-Associated Effector Functions and Serum Half-life

PubMed Central

Saxena, Abhishek; Wu, Donghui

2016-01-01

Today, monoclonal immunoglobulin gamma (IgG) antibodies have become a major option in cancer therapy especially for the patients with advanced or metastatic cancers. Efficacy of monoclonal antibodies (mAbs) is achieved through both its antigen-binding fragment (Fab) and crystallizable fragment (Fc). Fab can specifically recognize tumor-associated antigen (TAA) and thus modulate TAA-linked downstream signaling pathways that may lead to the inhibition of tumor growth, induction of tumor apoptosis, and differentiation. The Fc region can further improve mAbs’ efficacy by mediating effector functions such as antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent cell-mediated phagocytosis. Moreover, Fc is the region interacting with the neonatal Fc receptor in a pH-dependent manner that can slow down IgG’s degradation and extend its serum half-life. Loss of the antibody Fc region dramatically shortens its serum half-life and weakens its anticancer effects. Given the essential roles that the Fc region plays in the modulation of the efficacy of mAb in cancer treatment, Fc engineering has been extensively studied in the past years. This review focuses on the recent advances in therapeutic Fc engineering that modulates its related effector functions and serum half-life. We also discuss the progress made in aglycosylated mAb development that may substantially reduce the cost of manufacture but maintain similar efficacies as conventional glycosylated mAb. Finally, we highlight several Fc engineering-based mAbs under clinical trials. PMID:28018347

Arachidonic acid, but not its metabolites, is essential for FcγR-stimulated intracellular killing of Staphylococcus aureus by human monocytes

PubMed Central

Zheng, L; Zomerdijk, T P L; Van Den Barselaar, M T; Geertsma, M F; Van Furth, R; Nibbering, P H

1999-01-01

Since arachidonic acid (AA) production by phospholipase A2 (PLA2) is essential for the Fcγ receptor (FcγR)-mediated respiratory burst and phagocytosis of opsonized erythrocytes by monocytes and macrophages, we focused in this study on the role of AA and its metabolites in the FcγR-stimulated intracellular killing of Staphylococcus aureus by human monocytes. The results revealed that the PLA2 inhibitors, but not inhibitors of cyclo-oxygenase and lipoxygenase, markedly suppressed the FcγR-mediated killing process. The production of O−2 by monocytes upon FcγR cross-linking was inhibited by 4-bromophenacyl bromide in a dose-dependent fashion, indicating that inhibition of PLA2 activity impairs the oxygen-dependent bactericidal mechanisms of monocytes, which could be partially restored by addition of exogenous AA and docosahexaenoic acid, but not myristic acid. These polyunsaturated fatty acids, but not myristic acid, stimulated the intracellular killing of S. aureus by monocytes, although not as effectively as FcγR cross-linking. Furthermore, FcγR cross-linking stimulated the release of AA from monocytes. Studies with selective inhibitors revealed that the FcγR-mediated activation of PLA2 is dependent on Ca2+ and tyrosine kinase activity. Together these results indicate a key role for PLA2/AA, but not its major metabolites, in mediating the FcγR-stimulated intracellular killing of S. aureus by monocytes. PMID:10233682

Sudan ebolavirus long recovered survivors produce GP-specific Abs that are of the IgG1 subclass and preferentially bind FcγRI.

PubMed

Radinsky, Olga; Edri, Avishay; Brusilovsky, Michael; Fedida-Metula, Shlomit; Sobarzo, Ariel; Gershoni-Yahalom, Orly; Lutwama, Julius; Dye, John; Lobel, Leslie; Porgador, Angel

2017-07-20

Ebolavirus is a highly lethal pathogen, causing a severe hemorrhagic disease with a high fatality rate. To better understand immune correlates of protection by virus specific IgG, we investigated the evolution of the Fcγ receptors (FcγRs)-activating capabilities of antiviral IgG in serum samples of long recovered survivors. To this end, longitudinal serum samples from survivors of Sudan ebolavirus (SUDV) infection, studied over years, were examined for the presence of Ebola-GP specific IgG subclasses, and for their binding to FcγRs. We developed a cell-based reporter system to quantitate pathogen-specific antibody binding to FcγRIIIA, FcγRIIA, FcγRIIB and FcγRI. With this system, we demonstrate that anti-GP-specific stimulation of the FcγRI reporter by survivors' sera was substantially high one year after acute infection, with a slight reduction in activity over a decade post infection. We further demonstrate that GP-specific IgG1 is by far the seroprevalent subclass that retained and even enhanced its presence in the sera, over ten years post infection; the prevalence of other GP-specific IgG subclasses was considerably reduced over time. In accordance, GP-specific FcγRI reporter response and GP-specific total IgG1 subclass correlated in the studied group of Ebola survivors. These observations are important for further informing Ebola vaccine and therapeutic development.

Novel Confocal Microscopic and Flow Cytometric Based Assays to Visualize and Detect the (Beta)2-Adrenergic Receptor in Human Lymphocyte and Mononuclear Cell Populations

NASA Technical Reports Server (NTRS)

Salicru, A. N.; Crucian, B. E.; Nelman, M. A.; Sams, C. F.; Actor, J. K.; Marshall, G. D.

2006-01-01

The data show that immunophenotyping of leukocyte populations with (beta)2AR is possible with the commercially available Ab, although the FC assay is limited to the IST as a result of the Ab binding site to the intracellular C-terminus of the 2AR. The FC assay has applications for measuring alterations in total (beta)2AR in human leukocyte populations as changes in fluorescence. In addition, CM confirms that both surface and intracellular compartments stain positively for the (beta)2AR and can be used for qualitative assays that screen for changes in receptor compartmentalization and localization.

The interaction of ruminant IgG with receptor type II for IgG on human phagocytes.

PubMed Central

Jungi, T W; Peterhans, E; Pfister, H; Fey, H

1989-01-01

The interaction of ruminant IgG with human phagocytes was assessed using Fc receptor (FcR)-mediated ingestion and the triggering of a respiratory burst as effector functions indicative of receptor-specific interaction. In monomeric form, ruminant IgG was three to five orders of magnitude less potent than homologous IgG in inhibiting FcR-specific phagocytosis by monocytes. However, when attached to tanned sheep erythrocytes (Es-T), ruminant IgG was opsonic, as it promoted enhanced phagocytosis of Es-T, comparable to ingestion of rabbit IgG-coated Es. This phagocytosis was inhibitable by high concentrations of human IgG in the fluid phase. Moreover, Es-T precoated with ferritin could be opsonized to a similar degree by anti-ferritin IgG from rabbit and cow. However, only bovine IgG1, but not IgG2, was opsonic. Bovine and goat IgG of some, but not other, suppliers were inactive. Similar results were obtained by measuring the respiratory burst triggered by heat-aggregated IgG, using a luminol-enhanced chemiluminescence assay. Thus, human IgG and ruminant IgG stimulated monocytes and, to a lesser extent, polymorphonuclear leucocytes (PMN), to generate CL. Depending on the manufacturer, some preparations of bovine and goat IgG were inactive, and bovine IgG2 failed to induce CL. These findings prove that certain ruminant IgG preparations, including bovine IgG1 interacting weakly with homologous PMN and monocytes, do interact with human PMN, monocytes and macrophages in a FcR-specific manner when offered in complexed form. Inhibition studies suggest that bovine IgG1 interacts mainly with human FcR type II. In contrast, bovine IgG2, regarded as cytophilic for homologous PMN, fails to interact with human PMN, monocytes and macrophages. PMID:15493277

Anti-proliferative Effect of Engineered Neural Stem Cells Expressing Cytosine Deaminase and Interferon-β against Lymph Node–Derived Metastatic Colorectal Adenocarcinoma in Cellular and Xenograft Mouse Models

PubMed Central

Park, Geon-Tae; Kim, Seung U.; Choi, Kyung-Chul

2017-01-01

Purpose Genetically engineered stem cells may be advantageous for gene therapy against various human cancers due to their inherent tumor-tropic properties. In this study, genetically engineered human neural stem cells (HB1.F3) expressing Escherichia coli cytosine deaminase (CD) (HB1.F3.CD) and human interferon-β (IFN-β) (HB1.F3.CD.IFN-β) were employed against lymph node–derived metastatic colorectal adenocarcinoma. Materials and Methods CD can convert a prodrug, 5-fluorocytosine (5-FC), to active 5-fluorouracil, which inhibits tumor growth through the inhibition of DNA synthesis,while IFN-β also strongly inhibits tumor growth by inducing the apoptotic process. In reverse transcription polymerase chain reaction analysis, we confirmed that HB1.F3.CD cells expressed the CD gene and HB1.F3.CD.IFN-β cells expressed both CD and IFN-β genes. Results In results of a modified trans-well migration assay, HB1.F3.CD and HB1.F3.CD.IFN-β cells selectively migrated toward SW-620, human lymph node–derived metastatic colorectal adenocarcinoma cells. The viability of SW-620 cells was significantly reduced when co-cultured with HB1.F3.CD or HB1.F3.CD.IFN-β cells in the presence of 5-FC. In addition, it was found that the tumor-tropic properties of these engineered human neural stem cells (hNSCs) were attributed to chemoattractant molecules including stromal cell-derived factor 1, c-Kit, urokinase receptor, urokinase-type plasminogen activator, and C-C chemokine receptor type 2 secreted by SW-620 cells. In a xenograft mouse model, treatment with hNSC resulted in significantly inhibited growth of the tumor mass without virulent effects on the animals. Conclusion The current results indicate that engineered hNSCs and a prodrug treatment inhibited the growth of SW-620 cells. Therefore, hNSC therapy may be a clinically effective tool for the treatment of lymph node metastatic colorectal cancer. PMID:27188205

Desialylation is a mechanism of Fc-independent platelet clearance and a therapeutic target in immune thrombocytopenia

PubMed Central

Li, June; van der Wal, Dianne E.; Zhu, Guangheng; Xu, Miao; Yougbare, Issaka; Ma, Li; Vadasz, Brian; Carrim, Naadiya; Grozovsky, Renata; Ruan, Min; Zhu, Lingyan; Zeng, Qingshu; Tao, Lili; Zhai, Zhi-min; Peng, Jun; Hou, Ming; Leytin, Valery; Freedman, John; Hoffmeister, Karin M.; Ni, Heyu

2015-01-01

Immune thrombocytopenia (ITP) is a common bleeding disorder caused primarily by autoantibodies against platelet GPIIbIIIa and/or the GPIb complex. Current theory suggests that antibody-mediated platelet destruction occurs in the spleen, via macrophages through Fc–FcγR interactions. However, we and others have demonstrated that anti-GPIbα (but not GPIIbIIIa)-mediated ITP is often refractory to therapies targeting FcγR pathways. Here, we generate mouse anti-mouse monoclonal antibodies (mAbs) that recognize GPIbα and GPIIbIIIa of different species. Utilizing these unique mAbs and human ITP plasma, we find that anti-GPIbα, but not anti-GPIIbIIIa antibodies, induces Fc-independent platelet activation, sialidase neuraminidase-1 translocation and desialylation. This leads to platelet clearance in the liver via hepatocyte Ashwell–Morell receptors, which is fundamentally different from the classical Fc–FcγR-dependent macrophage phagocytosis. Importantly, sialidase inhibitors ameliorate anti-GPIbα-mediated thrombocytopenia in mice. These findings shed light on Fc-independent cytopenias, designating desialylation as a potential diagnostic biomarker and therapeutic target in the treatment of refractory ITP. PMID:26185093

Molecular Mechanisms and Treatment Strategies for Obesity-Associated Coronary Artery Disease, an Imminent Military Epidemic

DTIC Science & Technology

2008-12-01

statistically significant. T. Chol indicates total cholesterol ; HDL, high - density lipoprotein . B, Hematoxylin and eosin staining of proximal aortas from...low density lipoprotein receptor null Ldlr/ mice transplanted with Stat1/ bone marrow. Conclusions—STAT1 is critical for endoplasmic reticulum...intracellular accumulation of lipoprotein - derived free cholesterol (FC).11 FC enrichment of macro- phages, like many ER stressors, activates the UPR

Tissue factor is an angiogenic-specific receptor for factor VII-targeted immunotherapy and photodynamic therapy.

PubMed

Hu, Zhiwei; Cheng, Jijun; Xu, Jie; Ruf, Wolfram; Lockwood, Charles J

2017-02-01

Identification of target molecules specific for angiogenic vascular endothelial cells (VEC), the inner layer of pathological neovasculature, is critical for discovery and development of neovascular-targeting therapy for angiogenesis-dependent human diseases, notably cancer, macular degeneration and endometriosis, in which vascular endothelial growth factor (VEGF) plays a central pathophysiological role. Using VEGF-stimulated vascular endothelial cells (VECs) isolated from microvessels, venous and arterial blood vessels as in vitro angiogenic models and unstimulated VECs as a quiescent VEC model, we examined the expression of tissue factor (TF), a membrane-bound receptor on the angiogenic VEC models compared with quiescent VEC controls. We found that TF is specifically expressed on angiogenic VECs in a time-dependent manner in microvessels, venous and arterial vessels. TF-targeted therapeutic agents, including factor VII (fVII)-IgG1 Fc and fVII-conjugated photosensitizer, can selectively bind angiogenic VECs, but not the quiescent VECs. Moreover, fVII-targeted photodynamic therapy can selectively and completely eradicate angiogenic VECs. We conclude that TF is an angiogenic-specific receptor and the target molecule for fVII-targeted therapeutics. This study supports clinical trials of TF-targeted therapeutics for the treatment of angiogenesis-dependent diseases such as cancer, macular degeneration and endometriosis.

Improving efficacy of cancer immunotherapy by genetic modification of natural killer cells.

PubMed

Burga, Rachel A; Nguyen, Tuongvan; Zulovich, Jane; Madonna, Sarah; Ylisastigui, Loyda; Fernandes, Rohan; Yvon, Eric

2016-11-01

Natural killer (NK) cells are members of the innate immune system that recognize target cells via activating and inhibitory signals received through cell receptors. Derived from the lymphoid lineage, NK cells are able to produce cytokines and exert a cytotoxic effect on viral infected and malignant cells. It is their unique ability to lyse target cells rapidly and without prior education that renders NK cells a promising effector cell for adoptive cell therapy. However, both viruses and tumors employ evasion strategies to avoid attack by NK cells, which represent biological challenges that need to be harnessed to fully exploit the cytolytic potential of NK cells. Using genetic modification, the function of NK cells can be enhanced to improve their homing, cytolytic activity, in vivo persistence and safety. Examples include gene modification to express chemokine, high-affinity Fc receptor and chimeric antigen receptors, suicide genes and the forced expression of cytokines such as interleukin (IL)-2 and IL-15. Preclinical studies have clearly demonstrated that such approaches are effective in improving NK-cell function, homing and safety. In this review, we summarize the recent advances in the genetic manipulations of NK cells and their application for cellular immunotherapeutic strategies. Copyright © 2016 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

Immunoglobulin Fc gamma receptor promotes immunoglobulin uptake, immunoglobulin-mediated calcium increase, and neurotransmitter release in motor neurons

NASA Technical Reports Server (NTRS)

Mohamed, Habib A.; Mosier, Dennis R.; Zou, Ling L.; Siklos, Laszlo; Alexianu, Maria E.; Engelhardt, Jozsef I.; Beers, David R.; Le, Wei-dong; Appel, Stanley H.

2002-01-01

Receptors for the Fc portion of immunoglobulin G (IgG; FcgammaRs) facilitate IgG uptake by effector cells as well as cellular responses initiated by IgG binding. In earlier studies, we demonstrated that amyotrophic lateral sclerosis (ALS) patient IgG can be taken up by motor neuron terminals and transported retrogradely to the cell body and can alter the function of neuromuscular synapses, such as increasing intracellular calcium and spontaneous transmitter release from motor axon terminals after passive transfer. In the present study, we examined whether FcgammaR-mediated processes can contribute to these effects of ALS patient immunoglobulins. F(ab')(2) fragments (which lack the Fc portion) of ALS patient IgG were not taken up by motor axon terminals and were not retrogradely transported. Furthermore, in a genetically modified mouse lacking the gamma subunit of the FcR, the uptake of whole ALS IgG and its ability to enhance intracellular calcium and acetylcholine release were markedly attenuated. These data suggest that FcgammaRs appear to participate in IgG uptake into motor neurons as well as IgG-mediated increases in intracellular calcium and acetylcholine release from motor axon terminals. Copyright 2002 Wiley-Liss, Inc.

Bispecific antibodies and trispecific immunocytokines for targeting the immune system against cancer: preparing for the future.

PubMed

Fournier, Philippe; Schirrmacher, Volker

2013-02-01

Monoclonal anti-tumor antibodies (mAbs) that are clinically effective usually recruit, via their constant fragment (Fc) domain, Fc receptor (FcR)-positive accessory cells of the immune system and engage these additionally against the tumor. Since T cells are FcR negative, these important cells are not getting involved. In contrast to mAbs, bispecific antibodies (bsAbs) can be designed in such a way that they involve T cells. bsAbs are artificially designed molecules that bind simultaneously to two different antigens, one on the tumor cell, the other one on an immune effector cell such as CD3 on T cells. Such dual antibody constructs can cross-link tumor cells and T cells. Many such bsAb molecules at the surface of tumor cells can thus build a bridge to T cells and aggregate their CD3 molecules, thereby activating them for cytotoxic activity. BsAbs can also contain a third binding site, for instance a Fc domain or a cytokine that would bind to its respective cytokine receptor. The present review discusses the pros and cons for the use of the Fc fragment during the development of bsAbs using either cell-fusion or recombinant DNA technologies. The recombinant antibody technology allows the generation of very efficient bsAbs containing no Fc domain such as the bi-specific T-cell engager (BiTE). The strong antitumor activity of these molecules makes them very interesting new cancer therapeutics. Over the last decade, we have developed another concept, namely to combine bsAbs and multivalent immunocytokines with a tumor cell vaccine. The latter are patient-derived tumor cells modified by infection with a virus. The virus-Newcastle Disease Virus (NDV)-introduces, at the surface of the tumor cells, viral molecules that can serve as general anchors for the bsAbs. Our strategy aims at redirecting, in an Fc-independent fashion, activities of T cells and accessory cells against autologous tumor antigens. It creates very promising perspectives for a new generation of efficient and safe cancer therapeutics that should confer long-lasting anti-tumor immunity.

Genetically defined fear-induced aggression: Focus on BDNF and its receptors.

PubMed

Ilchibaeva, Tatiana V; Tsybko, Anton S; Kozhemyakina, Rimma V; Kondaurova, Elena M; Popova, Nina K; Naumenko, Vladimir S

2018-05-02

Brain-derived neurotrophic factor (BDNF), its precursor proBDNF, BDNF pro-peptide, BDNF mRNA levels, as well as TrkB and p75 NTR receptors mRNA and protein levels, were studied in the brain of rats, selectively bred for more than 85 generations for either the high level or the lack of fear-induced aggressive behavior. Furthermore, we have found that rats of aggressive strain demonstrated both high level of aggression toward humans and increased amplitude of acoustic startle response compared to rats selectively bred for the lack of fear-induced aggression. Significant increase in the BDNF mRNA, mature BDNF and proBDNF protein levels in the raphe nuclei (RN), hippocampus (Hc), nucleus accumbens (NAcc), amygdala, striatum and hypothalamus (Ht) of aggressive rats was revealed. The BDNF/proBDNF ratio was significantly reduced in the Hc and NAcc of highly aggressive rats suggesting prevalence of the proBDNF in these structures. In the Hc and frontal cortex (FC) of aggressive rats, the level of the full-length TrkB (TrkB-FL) receptor form was decreased, whereas the truncated TrkB (TrkB-T) protein level was increased in the RN, FC, substantia nigra and Ht. The TrkB-FL/TrkB-T ratio was significantly decreased in highly aggressive rats suggesting TrkB-T is predominant in highly aggressive rats. The p75 NTR expression was slightly changed in majority of studied brain structures of aggressive rats. The data indicate the BDNF system in the brain of aggressive and nonaggressive animals is extremely different at all levels, from transcription to reception, suggesting significant role of BDNF system in the development of highly aggressive phenotype. Copyright © 2018 Elsevier B.V. All rights reserved.

Isolation of a human anti-epidermal growth factor receptor Fab antibody, EG-19-11, with subnanomolar affinity from naïve immunoglobulin repertoires using a hierarchical antibody library system.

PubMed

Hur, Byung-ung; Yoon, Jae-bong; Liu, Li-Kun; Cha, Sang-hoon

2010-11-30

Specific antibodies that possess a subnanomolar affinity are very difficult to obtain from human naïve immunoglobulin repertoires without the use of lengthy affinity optimization procedures. Here, we designed a hierarchical phage-displayed antibody library system to generate an enormous diversity of combinatorial Fab fragments (6×10(17)) and attempted to isolate high-affinity Fabs against the human epidermal growth factor receptor (EGFR). A primary antibody library, designated HuDVFab-8L, comprising 4.5×10(9) human naïve heavy chains and eight unspecified human naïve light chains was selected against the EGFR-Fc protein by biopanning, and four anti-EGFR Fab clones were isolated. Because one of the Fab clones, denoted EG-L2-11, recognized a native EGFR expressed on A431 cells, the heavy chain of the Fab was shuffled with a human naïve light chain repertoire with a diversity of 1.4×10(8) and selected a second time against the EGFR-Fc protein again. One EG-L2-11 variant, denoted EG-19-11, recognized an EGFR epitope that was almost the same as that bound by cetuximab and had a K(D) of approximately 540 pM for soluble EGFR, which is about 7-fold higher than that of the FabC225 derived from cetuximab. This variant was also internalized by A431 cells, likely via receptor-mediated endocytosis, and it efficiently inhibited EGF-mediated tyrosine phosphorylation of the EGFR. These results demonstrate that the use of our hierarchical antibody library system is advantageous in generating fully human antibodies especially with a therapeutic purpose. Copyright © 2010 Elsevier B.V. All rights reserved.

A platform to screen for C-type lectin receptor-binding carbohydrates and their potential for cell-specific targeting and immune modulation.

PubMed

Maglinao, Maha; Eriksson, Magdalena; Schlegel, Mark K; Zimmermann, Stephanie; Johannssen, Timo; Götze, Sebastian; Seeberger, Peter H; Lepenies, Bernd

2014-02-10

Myeloid C-type lectin receptors (CLRs) in innate immunity represent a superfamily of pattern recognition receptors that recognize carbohydrate structures on pathogens and self-antigens. The primary interaction of an antigen-presenting cell and a pathogen shapes the following immune response. Therefore, the identification of CLR ligands that can either enhance or modulate the immune response is of interest. We have developed a screening platform based on glycan arrays to identify immune modulatory carbohydrate ligands of CLRs. A comprehensive library of CLRs was expressed by fusing the extracellular part of each respective CLR, the part containing the carbohydrate-recognition domain (CRD), to the Fc fragment of human IgG1 molecules. CLR-Fc fusion proteins display the CRD in a dimeric form, are properly glycosylated, and can be detected by a secondary antibody with a conjugated fluorophore. Thus, they are valuable tools for high-throughput screening. We were able to identify novel carbohydrate binders of CLRs using the glycan array technology. These CLR-binding carbohydrates were then covalently attached to the model antigen ovalbumin. The ovalbumin neoglycoconjugates were used in a dendritic cell/T cell co-culture assay to stimulate transgenic T cells in vitro. In addition, mice were immunized with these conjugates to analyze the immune modulatory properties of the CLR ligands in vivo. The CLR ligands induced an increased Th1 cytokine production in vitro and modulated the humoral response in vivo. The platform described here allows for the identification of CLR ligands, as well as the evaluation of each ligand's cell-specific targeting and immune modulatory properties. Copyright © 2013 Elsevier B.V. All rights reserved.

Paracrine-Mediated Neuroprotection and Neuritogenesis of Axotomised Retinal Ganglion Cells by Human Dental Pulp Stem Cells: Comparison with Human Bone Marrow and Adipose-Derived Mesenchymal Stem Cells

PubMed Central

Mead, Ben; Logan, Ann; Berry, Martin

2014-01-01

We have investigated and compared the neurotrophic activity of human dental pulp stem cells (hDPSC), human bone marrow-derived mesenchymal stem cells (hBMSC) and human adipose-derived stem cells (hAMSC) on axotomised adult rat retinal ganglion cells (RGC) in vitro in order to evaluate their therapeutic potential for neurodegenerative conditions of RGC. Using the transwell system, RGC survival and length/number of neurites were quantified in coculture with stem cells in the presence or absence of specific Fc-receptor inhibitors to determine the role of NGF, BDNF, NT-3, VEGF, GDNF, PDGF-AA and PDGF-AB/BB in stem cell-mediated RGC neuroprotection and neuritogenesis. Conditioned media, collected from cultured hDPSC/hBMSC/hAMSC, were assayed for the secreted growth factors detailed above using ELISA. PCR array determined the hDPSC, hBMSC and hAMSC expression of genes encoding 84 growth factors and receptors. The results demonstrated that hDPSC promoted significantly more neuroprotection and neuritogenesis of axotomised RGC than either hBMSC or hAMSC, an effect that was neutralized after the addition of specific Fc-receptor inhibitors. hDPSC secreted greater levels of various growth factors including NGF, BDNF and VEGF compared with hBMSC/hAMSC. The PCR array confirmed these findings and identified VGF as a novel potentially therapeutic hDPSC-derived neurotrophic factor (NTF) with significant RGC neuroprotective properties after coculture with axotomised RGC. In conclusion, hDPSC promoted significant multi-factorial paracrine-mediated RGC survival and neurite outgrowth and may be considered a potent and advantageous cell therapy for retinal nerve repair. PMID:25290916

DOE Office of Scientific and Technical Information (OSTI.GOV)

He Yuxian; Li Jingjing; Jiang Shibo

The spike (S) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) has two major functions: interacting with the receptor to mediate virus entry and inducing protective immunity. Coincidently, the receptor-binding domain (RBD, residues 318-510) of SAR-CoV S protein is a major antigenic site to induce neutralizing antibodies. Here, we used RBD-Fc, a fusion protein containing the RBD and human IgG1 Fc, as a model in the studies and found that a single amino acid substitution in the RBD (R441A) could abolish the immunogenicity of RBD to induce neutralizing antibodies in immunized mice and rabbits. With a panel of anti-RBD mAbsmore » as probes, we observed that R441A substitution was able to disrupt the majority of neutralizing epitopes in the RBD, suggesting that this residue is critical for the antigenic structure responsible for inducing protective immune responses. We also demonstrated that the RBD-Fc bearing R441A mutation could not bind to soluble and cell-associated angiotensin-converting enzyme 2 (ACE2), the functional receptor for SARS-CoV and failed to block S protein-mediated pseudovirus entry, indicating that this point mutation also disrupted the receptor-binding motif (RBM) in the RBD. Taken together, these data provide direct evidence to show that a single amino acid residue at key position in the RBD can determine the major function of SARS-CoV S protein and imply for designing SARS vaccines and therapeutics.« less

B cell expression of the inhibitory Fc gamma receptor is unchanged in early MS.

PubMed

Comabella, Manuel; Montalban, Xavier; Kakalacheva, Kristina; Osman, Deeqa; Nimmerjahn, Falk; Tintoré, Mar; Lünemann, Jan D

2010-06-01

Expression of the inhibitory Fcgamma receptor IIB (FcgammaRIIB) has emerged as a late checkpoint during peripheral B cell development which prevents autoreactive memory B lymphocytes from becoming long-lived plasma cells. Decreased expression of FcgammaRIIB or non-functional FcgammaRIIB variants are associated with the development of autoimmune tissue inflammation. We determined the expression profile of FcgammaRIIB in peripheral blood cells in treatment-naïve patients with early MS. Twenty-five patients with clinically isolated syndrome (CIS) who converted to clinically definite MS (CDMS) and 25 demographically matched healthy donors were included in the study. Frequencies of peripheral blood monocytes and B cell subsets as well as FcgammaRIIB expression profile was determined by flow cytometry. FcgammaRIIB expression levels were higher in B cells compared to monocytes (p<0.0001) and higher in memory B cells compared to their naïve counterparts (p<0.0001). However, FcgammaRIIB expression in naïve and memory B cells as well as monocytes was unchanged in patients with early MS at onset of symptoms as well as after conversion to CDMS compared to controls. No significant correlations were found between FcgammaRIIB expression levels and brain MRI-derived metrics or EDSS progression during follow-up. These data indicate that FcgammaRIIB expression, a critical late B cell differentiation checkpoint preventing the occurrence of autoreactive long-lived plasma cells, is not impaired in treatment-naïve patients with MS, at least in the early phases of the disease. Copyright 2010 Elsevier B.V. All rights reserved.

Comparative analysis of biological activities of Der p I-derived peptides on Fc epsilon receptor-bearing cells from Dermatophagoides pteronyssinus-sensitive patients.

PubMed Central

Jeannin, P; Pestel, J; Bossus, M; Lassalle, P; Tartar, A; Tonnel, A B

1993-01-01

The ability of four uncoupled synthetic peptides (p52-71, p117-133, p176-187, p188-199) derived from Der p I, a major allergen from the house dust mite Dermatophagoides pteronyssinus (Dpt) to stimulate Fc epsilon R+ cells from Dpt-sensitive patients was comparatively analysed. Each free peptide may specifically stimulate basophils (Fc epsilon RI+ cells) and platelets (Fc epsilon RII+ cells) from patients with significant levels of anti-Der p I IgE antibodies; p52-71 and p117-133 appear the best cell stimulation inducers. Both concentration-dependent biological activities of Der p I-peptide on Fc epsilon R+ cells are enhanced by coupling peptide to a carrier (as human serum albumin). Interestingly each Der p I-sensitive patient tested presents an individual pattern of response to peptide. Thus, from our results it appears that different Der p I sequences could be involved in the immune response to Der p I. PMID:7682161

Comparative analysis of biological activities of Der p I-derived peptides on Fc epsilon receptor-bearing cells from Dermatophagoides pteronyssinus-sensitive patients.

PubMed

Jeannin, P; Pestel, J; Bossus, M; Lassalle, P; Tartar, A; Tonnel, A B

1993-04-01

The ability of four uncoupled synthetic peptides (p52-71, p117-133, p176-187, p188-199) derived from Der p I, a major allergen from the house dust mite Dermatophagoides pteronyssinus (Dpt) to stimulate Fc epsilon R+ cells from Dpt-sensitive patients was comparatively analysed. Each free peptide may specifically stimulate basophils (Fc epsilon RI+ cells) and platelets (Fc epsilon RII+ cells) from patients with significant levels of anti-Der p I IgE antibodies; p52-71 and p117-133 appear the best cell stimulation inducers. Both concentration-dependent biological activities of Der p I-peptide on Fc epsilon R+ cells are enhanced by coupling peptide to a carrier (as human serum albumin). Interestingly each Der p I-sensitive patient tested presents an individual pattern of response to peptide. Thus, from our results it appears that different Der p I sequences could be involved in the immune response to Der p I.

Fcγ1 fragment of IgG1 as a powerful affinity tag in recombinant Fc-fusion proteins: immunological, biochemical and therapeutic properties.

PubMed

Soleimanpour, Saman; Hassannia, Tahereh; Motiee, Mahdieh; Amini, Abbas Ali; Rezaee, S A R

2017-05-01

Affinity tags are vital tools for the production of high-throughput recombinant proteins. Several affinity tags, such as the hexahistidine tag, maltose-binding protein, streptavidin-binding peptide tag, calmodulin-binding peptide, c-Myc tag, glutathione S-transferase and FLAG tag, have been introduced for recombinant protein production. The fragment crystallizable (Fc) domain of the IgG1 antibody is one of the useful affinity tags that can facilitate detection, purification and localization of proteins and can improve the immunogenicity, modulatory effects, physicochemical and pharmaceutical properties of proteins. Fcγ recombinant forms a group of recombinant proteins called Fc-fusion proteins (FFPs). FFPs are widely used in drug discovery, drug delivery, vaccine design and experimental research on receptor-ligand interactions. These fusion proteins have become successful alternatives to monoclonal antibodies for drug developments. In this review, the physicochemical, biochemical, immunological, pharmaceutical and therapeutic properties of recombinant FFPs were discussed as a new generation of bioengineering strategies.

Internalization of rituximab and the efficiency of B Cell depletion in rheumatoid arthritis and systemic lupus erythematosus.

PubMed

Reddy, Venkat; Cambridge, Geraldine; Isenberg, David A; Glennie, Martin J; Cragg, Mark S; Leandro, Maria

2015-05-01

Rituximab, a type I anti-CD20 monoclonal antibody (mAb), induces incomplete B cell depletion in some patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), thus contributing to a poor clinical response. The mechanisms of this resistance remain elusive. The purpose of this study was to determine whether type II mAb are more efficient than type I mAb at depleting B cells from RA and SLE patients, whether internalization influences the efficiency of depletion, and whether Fcγ receptor type IIb (FcγRIIb) and the B cell receptor regulate this internalization process. We used an in vitro whole blood B cell-depletion assay to assess the efficiency of depletion, flow cytometry to study cell surface protein expression, and surface fluorescence-quenching assays to assess rituximab internalization, in samples from patients with RA and patients with SLE. Paired t-test or Mann-Whitney U test was used to compare groups, and Spearman's rank correlation test was used to assess correlation. We found that type II mAb internalized significantly less rituximab than type I mAb and depleted B cells from patients with RA and SLE at least 2-fold more efficiently than type I mAb. Internalization of rituximab was highly variable between patients, was regulated by FcγRIIb, and inversely correlated with cytotoxicity in whole blood B cell-depletion assays. The lowest levels of internalization were seen in IgD- B cells, including postswitched (IgD-CD27+) memory cells. Internalization of type I anti-CD20 mAb was also partially inhibited by anti-IgM stimulation. Variability in internalization of rituximab was observed and was correlated with impaired B cell depletion. Therefore, slower-internalizing type II mAb should be considered as alternative B cell-depleting agents for the treatment of RA and SLE. © 2015 The Authors. Arthritis & Rheumatology is published by Wiley Periodicals, Inc. on behalf of the American College of Rheumatology.

Internalization of Rituximab and the Efficiency of B Cell Depletion in Rheumatoid Arthritis and Systemic Lupus Erythematosus

PubMed Central

Cambridge, Geraldine; Isenberg, David A.; Glennie, Martin J.; Cragg, Mark S.; Leandro, Maria

2015-01-01

Objective Rituximab, a type I anti‐CD20 monoclonal antibody (mAb), induces incomplete B cell depletion in some patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), thus contributing to a poor clinical response. The mechanisms of this resistance remain elusive. The purpose of this study was to determine whether type II mAb are more efficient than type I mAb at depleting B cells from RA and SLE patients, whether internalization influences the efficiency of depletion, and whether Fcγ receptor type IIb (FcγRIIb) and the B cell receptor regulate this internalization process. Methods We used an in vitro whole blood B cell–depletion assay to assess the efficiency of depletion, flow cytometry to study cell surface protein expression, and surface fluorescence–quenching assays to assess rituximab internalization, in samples from patients with RA and patients with SLE. Paired t‐test or Mann‐Whitney U test was used to compare groups, and Spearman's rank correlation test was used to assess correlation. Results We found that type II mAb internalized significantly less rituximab than type I mAb and depleted B cells from patients with RA and SLE at least 2‐fold more efficiently than type I mAb. Internalization of rituximab was highly variable between patients, was regulated by FcγRIIb, and inversely correlated with cytotoxicity in whole blood B cell–depletion assays. The lowest levels of internalization were seen in IgD– B cells, including postswitched (IgD–CD27+) memory cells. Internalization of type I anti‐CD20 mAb was also partially inhibited by anti‐IgM stimulation. Conclusion Variability in internalization of rituximab was observed and was correlated with impaired B cell depletion. Therefore, slower‐internalizing type II mAb should be considered as alternative B cell–depleting agents for the treatment of RA and SLE. PMID:25916583

Rapid and preferential distribution of blood-borne αCD3εAb to the liver is followed by local stimulation of T cells and natural killer T cells

PubMed Central

Wingender, Gerhard; Schumak, Beatrix; Schurich, Anna; Gessner, J Engelbert; Endl, Elmar; Limmer, Andreas; Knolle, Percy A

2006-01-01

Dissemination of soluble molecules or antigens via the blood stream is considered to lead to a uniform distribution in the various organs of the body, but organ-specific microarchitecture and vascularization may influence this. Following intravenous injection of αCD3ε antibody (αCD3εAb) we observed clear differences in antibody binding to Fcγ receptor (FcγR)+ antigen-presenting cells (APCs) or T lymphocytes in different organs. Significant binding of blood-borne αCD3εAb was only detected in the spleen and liver and not in the thymus or lymph node. In the spleen, only 10% of dendritic cells/macrophages and 40% of T-cell receptor (TCR)-β+ cells were positive for αCD3εAb, and, dependent on FcγR-mediated cross-linking of αCD3εAb, a similar percentage of splenic TCR-β+ cells were stimulated and became CD69+. Stimulation of TCR-β+ cells in the liver was at least as efficient as in the spleen, but almost all T cells and all scavenger liver sinusoidal endothelial cells bound αCD3εAb. In contrast to CD69 up-regulation, only CD4+ natural killer T (NKT) cells and CD11ahigh CD8+ T cells were activated by αCD3εAb and expressed interferon (IFN)-γ. Again, IFN-γ release from NKT/T cells was at least as efficient in the liver as in the spleen. Taken together, our results support the notion that the combination of extensive hepatic vascularization and very high scavenger activity allows the liver to fulfill its metabolic tasks and to promote stimulation of the large but widely distributed hepatic population of NKT/T cells. PMID:16423047

Enhancing Antibody Fc Heterodimer Formation through Electrostatic Steering Effects

PubMed Central

Gunasekaran, Kannan; Pentony, Martin; Shen, Min; Garrett, Logan; Forte, Carla; Woodward, Anne; Ng, Soo Bin; Born, Teresa; Retter, Marc; Manchulenko, Kathy; Sweet, Heather; Foltz, Ian N.; Wittekind, Michael; Yan, Wei

2010-01-01

Naturally occurring IgG antibodies are bivalent and monospecific. Bispecific antibodies having binding specificities for two different antigens can be produced using recombinant technologies and are projected to have broad clinical applications. However, co-expression of multiple light and heavy chains often leads to contaminants and pose purification challenges. In this work, we have modified the CH3 domain interface of the antibody Fc region with selected mutations so that the engineered Fc proteins preferentially form heterodimers. These novel mutations create altered charge polarity across the Fc dimer interface such that coexpression of electrostatically matched Fc chains support favorable attractive interactions thereby promoting desired Fc heterodimer formation, whereas unfavorable repulsive charge interactions suppress unwanted Fc homodimer formation. This new Fc heterodimer format was used to produce bispecific single chain antibody fusions and monovalent IgGs with minimal homodimer contaminants. The strategy proposed here demonstrates the feasibility of robust production of novel Fc-based heterodimeric molecules and hence broadens the scope of bispecific molecules for therapeutic applications. PMID:20400508

Alendronate (ALN) combined with Osteoprotegerin (OPG) significantly improves mechanical properties of long bone than the single use of ALN or OPG in the ovariectomized rats

PubMed Central

2011-01-01

Background Alendronate (ALN) is the most common form of bisphosphonates used for the treatment of osteoporosis. Osteoprotegerin (OPG) has also been shown to reduce osteoporotic changes in both humans and experimental animals after systemic administration. The aim of this current study was to test if the anti-resorption effects of ALN may be enhanced when used in combination with OPG. Objectives To investigate the effects of ALN, OPG or combined on bone mass and bone mechanical properties in ovariectomized (OVX) rats. Methods OVX rats were treated with ALN, OPG-Fc, or OPG-Fc and ALN. Biochemical markers, trabecular bone mass, biomechanics, histomorphometry and RANKL expression in the bone tissues were examined following the treatments. Results The treatment of ALN, OPG-Fc and ALN+OPG-Fc all prevented bone loss in the OVX-rats, there was no statistical difference among the three treatment groups in terms of vertebrae BMD, mineralizing surfaces, mineral apposition rate, BFR/BS. The ALN+OPG-Fc treatment group had significantly increased the mechanical strength of lumber vertebral bodies and femoral shafts when compared to the ALN and OPG-Fc treatment groups. The RANKL protein expression in the vertebral bones was significantly decreased in the ALN and ALN+OPG-Fc treatment groups, suggesting the combined use of OPG-Fc and ALN might have amplified inhibition of bone resorption through inhibiting RANKL-dependent osteoclastogenesis. Conclusion The combined use of OPG-Fc and ALN may be a new treatment strategy for reversing bone loss and restoring bone quality in osteoprotic disorders. PMID:21752290

T cell chronic lymphocytic leukaemia with suppressor phenotype.

PubMed Central

Hofman, F M; Smith, D; Hocking, W

1982-01-01

The peripheral blood cells from a patient with T cell chronic lymphocytic leukaemia were examined for surface marker and functional characteristics. Eighty-91% of the peripheral blood cells formed SRBC rosettes and 22-49% possessed Fc receptors; 73% of the peripheral blood cells were reactive with the OKT8 antiserum and 61% expressed DR antigens. Response to PHA stimulation was markedly reduced, whereas allogeneic responsiveness in mixed leucocyte culture was intact. The ability of Con A-stimulated peripheral blood cells to generate suppressor activity in a mixed leucocyte reaction was deficient, whereas suppression of in vitro immunoglobulin synthesis was greater than normal. The leukaemic peripheral blood cell population expressed a T suppressor phenotype. Functional studies suggest that these cells were derived from the subset of T lymphocytes with regulatory activity for immunoglobulin synthesis as opposed to mitogenic responsiveness. PMID:6215199

Genetically Engineered Humanized Mouse Models for Preclinical Antibody Studies

PubMed Central

Proetzel, Gabriele; Wiles, Michael V.; Roopenian, Derry C.

2015-01-01

The use of genetic engineering has vastly improved our capabilities to create animal models relevant in preclinical research. With the recent advances in gene-editing technologies, it is now possible to very rapidly create highly tunable mouse models as needs arise. Here, we provide an overview of genetic engineering methods, as well as the development of humanized neonatal Fc receptor (FcRn) models and their use for monoclonal antibody in vivo studies. PMID:24150980

Transfer of IgG in the female genital tract by MHC class I-related neonatal Fc receptor (FcRn) confers protective immunity to vaginal infection

USDA-ARS?s Scientific Manuscript database

IgG is a major immunoglobulin subclass in mucosal secretions of human female genital tract, where it predominates over the IgA isotype. Despite the abundance of IgG, surprisingly little is known about whether and how IgG enters the lumen of the genital tract and the exact role of local IgG may play ...

Visualization of protein interactions in living Drosophila embryos by the bimolecular fluorescence complementation assay

PubMed Central

2011-01-01

Background Protein interactions control the regulatory networks underlying developmental processes. The understanding of developmental complexity will, therefore, require the characterization of protein interactions within their proper environment. The bimolecular fluorescence complementation (BiFC) technology offers this possibility as it enables the direct visualization of protein interactions in living cells. However, its potential has rarely been applied in embryos of animal model organisms and was only performed under transient protein expression levels. Results Using a Hox protein partnership as a test case, we investigated the suitability of BiFC for the study of protein interactions in the living Drosophila embryo. Importantly, all BiFC parameters were established with constructs that were stably expressed under the control of endogenous promoters. Under these physiological conditions, we showed that BiFC is specific and sensitive enough to analyse dynamic protein interactions. We next used BiFC in a candidate interaction screen, which led to the identification of several Hox protein partners. Conclusion Our results establish the general suitability of BiFC for revealing and studying protein interactions in their physiological context during the rapid course of Drosophila embryonic development. PMID:21276241

Improving Antibody-Based Cancer Therapeutics Through Glycan Engineering.

PubMed

Yu, Xiaojie; Marshall, Michael J E; Cragg, Mark S; Crispin, Max

2017-06-01

Antibody-based therapeutics has emerged as a major tool in cancer treatment. Guided by the superb specificity of the antibody variable domain, it allows the precise targeting of tumour markers. Recently, eliciting cellular effector functions, mediated by the Fc domain, has gained traction as a means by which to generate more potent antibody therapeutics. Extensive mutagenesis studies of the Fc protein backbone has enabled the generation of Fc variants that more optimally engage the Fcγ receptors known to mediate cellular effector functions such as antibody-dependent cellular cytotoxicity (ADCC) and cellular phagocytosis. In addition to the protein backbone, the homodimeric Fc domain contains two opposing N-linked glycans, which represent a further point of potential immunomodulation, independent of the Fc protein backbone. For example, a lack of core fucose usually attached to the IgG Fc glycan leads to enhanced ADCC activity, whereas a high level of terminal sialylation is associated with reduced inflammation. Significant growth in knowledge of Fc glycosylation over the last decade, combined with advancement in genetic engineering, has empowered glyco-engineering to fine-tune antibody therapeutics. This has culminated in the approval of two glyco-engineered antibodies for cancer therapy: the anti-CCR4 mogamulizumab approved in 2012 and the anti-CD20 obinutuzumab in 2013. We discuss here the technological platforms for antibody glyco-engineering and review the current clinical landscape of glyco-engineered antibodies.

Anti-influenza Hyperimmune Immunoglobulin Enhances Fc-functional Antibody Immunity during Human Influenza Infection.

PubMed

Vanderven, Hillary A; Wragg, Kathleen; Ana-Sosa-Batiz, Fernanda; Kristensen, Anne B; Jegaskanda, Sinthujan; Wheatley, Adam K; Wentworth, Deborah; Wines, Bruce D; Hogarth, P Mark; Rockman, Steve; Kent, Stephen J

2018-05-31

New treatments for severe influenza are needed. Passive transfer of influenza-specific hyperimmune pooled immunoglobulin (Flu-IVIG) boosts neutralising antibody responses to past strains in influenza-infected subjects. The effect of Flu-IVIG on antibodies with Fc-mediated functions, which may target diverse influenza strains, is unclear. We studied the capacity of Flu-IVIG, relative to standard IVIG, to bind to Fc receptors and mediate antibody-dependent cellular cytotoxicity in vitro. The effect of Flu-IVIG infusion, compared to placebo infusion, was examined in serial plasma samples from 24 subjects with confirmed influenza infection in the INSIGHT FLU005 pilot study. Flu-IVIG contains higher concentrations of Fc-functional antibodies than IVIG against a diverse range of influenza hemagglutinins. Following infusion of Flu-IVIG into influenza-infected subjects, a transient increase in Fc-functional antibodies was present for 1-3 days against infecting and non-infecting strains of influenza. Flu-IVIG contains antibodies with Fc-mediated functions against influenza virus and passive transfer of Flu-IVIG increases anti-influenza Fc-functional antibodies in the plasma of influenza-infected subjects. Enhancement of Fc-functional antibodies to a diverse range of influenza strains suggests that Flu-IVIG infusion could prove useful in the context of novel influenza virus infections, when there may be minimal or no neutralising antibodies in the Flu-IVIG preparation.

Hepatic FcRn regulates albumin homeostasis and susceptibility to liver injury

PubMed Central

Pyzik, Michal; Rath, Timo; Kuo, Timothy T.; Win, Sanda; Baker, Kristi; Hubbard, Jonathan J.; Grenha, Rosa; Gandhi, Amit; Krämer, Thomas D.; Mezo, Adam R.; McDonnell, Kevin; Nienaber, Vicki; Andersen, Jan Terje; Mizoguchi, Atsushi; Blumberg, Laurence; Purohit, Shalaka; Jones, Susan D.; Christianson, Greg; Lencer, Wayne I.; Sandlie, Inger; Kaplowitz, Neil; Roopenian, Derry C.; Blumberg, Richard S.

2017-01-01

The neonatal crystallizable fragment receptor (FcRn) is responsible for maintaining the long half-life and high levels of the two most abundant circulating proteins, albumin and IgG. In the latter case, the protective mechanism derives from FcRn binding to IgG in the weakly acidic environment contained within endosomes of hematopoietic and parenchymal cells, whereupon IgG is diverted from degradation in lysosomes and is recycled. The cellular location and mechanism by which FcRn protects albumin are partially understood. Here we demonstrate that mice with global or liver-specific FcRn deletion exhibit hypoalbuminemia, albumin loss into the bile, and increased albumin levels in the hepatocyte. In vitro models with polarized cells illustrate that FcRn mediates basal recycling and bidirectional transcytosis of albumin and uniquely determines the physiologic release of newly synthesized albumin into the basal milieu. These properties allow hepatic FcRn to mediate albumin delivery and maintenance in the circulation, but they also enhance sensitivity to the albumin-bound hepatotoxin, acetaminophen (APAP). As such, global or liver-specific deletion of FcRn results in resistance to APAP-induced liver injury through increased albumin loss into the bile and increased intracellular albumin scavenging of reactive oxygen species. Further, protection from injury is achieved by pharmacologic blockade of FcRn–albumin interactions with monoclonal antibodies or peptide mimetics, which cause hypoalbuminemia, biliary loss of albumin, and increased intracellular accumulation of albumin in the hepatocyte. Together, these studies demonstrate that the main function of hepatic FcRn is to direct albumin into the circulation, thereby also increasing hepatocyte sensitivity to toxicity. PMID:28330995

Gene expression changes in uterine myomas in response to ulipristal acetate treatment.

PubMed

Courtoy, Guillaume E; Donnez, Jacques; Ambroise, Jérôme; Arriagada, Pablo; Luyckx, Mathieu; Marbaix, Etienne; Dolmans, Marie-Madeleine

2018-05-07

Does ulipristal acetate (UPA) modify the expression of genes related to apoptosis or the extracellular matrix in uterine myomas and are any modifications associated with a clinical response? Targeted analysis of 176 apoptosis- or extracellular-matrix-related genes was conducted using polymerase chain reaction (PCR) arrays. Relevant results were validated by quantitative PCR. Four groups were established: responsive short-term (one course, n = 9), responsive long-term (two to four courses, n = 9), non-responsive (n = 9), and the control group who was not given any hormone therapy (n = 9). The clinical response was monitored by medical imagery and considered significant when volume reduction was greater than 25%. Compared with untreated myomas, significant changes in expression of four genes were found in UPA-treated myomas. Gene expression of integrin subunit beta 4 was repressed by UPA treatment (fold change [FC] = -12.50, P < 0.001, q < 0.001), tenascin-C expression was downregulated in UPA-responsive patients (FC = -2.50, P = 0.010, q = 0.090), survivin was repressed in short-term UPA-responsive tumours (FC = -7.69, P < 0.001, q = 0.010), and catenin delta 2 gene expression was upregulated in non-responsive myomas (FC = +7.36, P < 0.001, q = 0.010). This characterization provides the first molecular distinction between myomas responsive or non-responsive to UPA treatment. Copyright © 2018 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

Antibody Prophylaxis Against Dengue Virus 2 Infection in Non-Human Primates.

PubMed

Simmons, Monika; Putnak, Robert; Sun, Peifang; Burgess, Timothy; Marasco, Wayne A

2016-11-02

Passive immunization with anti-dengue virus (DENV) immune serum globulin (ISG) or monoclonal antibodies (Mabs) may serve to supplement or replace vaccination for short-term dengue immune prophylaxis. In the present study, we sought to establish proof-of-concept by evaluating several DENV-neutralizing antibodies for their ability to protect rhesus macaques against viremia following live virus challenge, including human anti-dengue ISG, and a human Mab (Mab11/wt) and its genetically engineered variant (Mab11/mutFc) that is unable to bind to cells with Fc gamma receptors (FcγR) and potentiate antibody-dependent enhancement (ADE). In the first experiment, groups of animals received ISG or Mab11/wt at low doses (3-10 mg/kg) or a saline control followed by challenge with DENV-2 at day 10 or 30. After passive immunization, only low-titered circulating virus-neutralizing antibody titers were measured in both groups, which were undetectable by day 30. After challenge at day 10, a reduction in viremia duration compared with the control was seen only in the ISG group (75%). However, after a day 30 challenge, no reduction in viremia was observed in both immunized groups. In a second experiment to test the effect of higher antibody doses on short-term protection, groups received either ISG, Mab11/wt, Mab11/mutFc (each at 25 mg/kg) or saline followed by challenge with DENV-2 on day 10. Increased virus-neutralizing antibody titers were detected in all groups at day 5 postinjection, with geometric mean titers (GMTs) of 464 (ISG), 313 (Mab11/wt), and 309 (Mab11/mutFc). After challenge, there was complete protection against viremia in the group that received ISG, and a reduction in viremia duration of 89% and 83% in groups that received Mab11/wt and Mab11/mutFc, respectively. An in vitro ADE assay in Fcγ receptor-bearing K562 cells with sera collected immediately before challenge showed increased DENV-2 infection levels in the presence of both ISG and Mab11/wt, which peaked at a serum dilution of 1:90, but not in Mab11/mutFc containing sera. The results suggest that antibody prophylaxis for dengue might be beneficial in eliminating or reducing viral loads thereby minimizing disease progression. Our results also suggest that blocking FcγR interactions through Mab11 Fc engineering may further prevent ADE. © The American Society of Tropical Medicine and Hygiene.

Cell-Based Screen Identifies Human Interferon-Stimulated Regulators of Listeria monocytogenes Infection

PubMed Central

Eitson, Jennifer L.; Chen, Didi; Jimenez, Alyssa; Mettlen, Marcel; Schoggins, John W.; Alto, Neal M.

2016-01-01

The type I interferon (IFN) activated transcriptional response is a critical antiviral defense mechanism, yet its role in bacterial pathogenesis remains less well characterized. Using an intracellular pathogen Listeria monocytogenes (Lm) as a model bacterial pathogen, we sought to identify the roles of individual interferon-stimulated genes (ISGs) in context of bacterial infection. Previously, IFN has been implicated in both restricting and promoting Lm growth and immune stimulatory functions in vivo. Here we adapted a gain-of-function flow cytometry based approach to screen a library of more than 350 human ISGs for inhibitors and enhancers of Lm infection. We identify 6 genes, including UNC93B1, MYD88, AQP9, and TRIM14 that potently inhibit Lm infection. These inhibitors act through both transcription-mediated (MYD88) and non-transcriptional mechanisms (TRIM14). Further, we identify and characterize the human high affinity immunoglobulin receptor FcγRIa as an enhancer of Lm internalization. Our results reveal that FcγRIa promotes Lm uptake in the absence of known host Lm internalization receptors (E-cadherin and c-Met) as well as bacterial surface internalins (InlA and InlB). Additionally, FcγRIa-mediated uptake occurs independently of Lm opsonization or canonical FcγRIa signaling. Finally, we established the contribution of FcγRIa to Lm infection in phagocytic cells, thus potentially linking the IFN response to a novel bacterial uptake pathway. Together, these studies provide an experimental and conceptual basis for deciphering the role of IFN in bacterial defense and virulence at single-gene resolution. PMID:28002492

Targeting the Epidermal Growth Factor Receptor Can Counteract the Inhibition of Natural Killer Cell Function Exerted by Colorectal Tumor-Associated Fibroblasts

PubMed Central

Costa, Delfina; Venè, Roberta; Benelli, Roberto; Romairone, Emanuele; Scabini, Stefano; Catellani, Silvia; Rebesco, Barbara; Mastracci, Luca; Grillo, Federica; Minghelli, Simona; Loiacono, Fabrizio; Zocchi, Maria Raffaella; Poggi, Alessandro

2018-01-01

Mesenchymal stromal cells (MSC) present in the tumor microenvironment [usually named tumor-associated fibroblasts (TAF)] can exert immunosuppressive effects on T and natural killer (NK) lymphocytes, favoring tumor immune escape. We have analyzed this mechanism in colorectal carcinoma (CRC) and found that co-culture of NK cells with TAF can prevent the IL-2-mediated NKG2D upregulation. This leads to the impairment of NKG2D-mediated recognition of CRC cells, sparing the NK cell activation through DNAM1 or FcγRIIIA (CD16). In situ, TAF express detectable levels of epidermal growth factor receptor (EGFR); thus, the therapeutic anti-EGFR humanized antibody cetuximab can trigger the antibody-dependent cellular cytotoxicity of TAF, through the engagement of FcγRIIIA on NK cells. Importantly, in the tumor, we found a lymphoid infiltrate containing NKp46+CD3− NK cells, enriched in CD16+ cells. This population, sorted and cultured with IL-2, could be triggered via CD16 and via NKG2D. Of note, ex vivo NKp46+CD3− cells were able to kill autologous TAF; in vivo, this might represent a control mechanism to reduce TAF-mediated regulatory effect on NK cell function. Altogether, these findings suggest that MSC from the neoplastic mucosa (TAF) of CRC patients can downregulate the immune cell recognition of CRC tumor cells. This immunosuppression can be relieved by the anti-EGFR antibody used in CRC immunotherapy. PMID:29910806

C-reactive protein specifically binds to Fcgamma receptor type I on a macrophage-like cell line.

PubMed

Tron, Kyrylo; Manolov, Dimitar E; Röcker, Carlheinz; Kächele, Martin; Torzewski, Jan; Nienhaus, G Ulrich

2008-05-01

C-reactive protein (CRP) is a prototype acute-phase protein that may be intimately involved in human disease. Its cellular receptors are still under debate; the main candidates are FcR for immunoglobulin G, as CRP was shown to bind specifically to FcgammaRI and FcgammaRIIa. Using ultrasensitive confocal live-cell imaging, we have studied CRP binding to FcgammaR naturally expressed in the plasma membranes of cells from a human leukemia cell line (Mono Mac 6). These macrophage-like cells express high levels of FcgammaRI and FcgammaRII. They were shown to bind fluorescently labeled CRP with micromolar affinity, KD = (6.6 +/- 1.5) microM. CRP binding could be inhibited by pre-incubation with human but not mouse IgG and was thus FcgammaR-specific. Blocking of FcgammaRI by an FcgammaRI-specific antibody abolished CRP binding essentially completely, whereas application of antibodies against FcgammaRII did not have a noticeable effect. In fluorescence images of Mono Mac 6 cells, the intensity patterns of bound CRP were correlated with those of FcgammaRI, but not FcgammaRII. These results provide clear evidence of specific interactions between CRP and FcgammaR (predominantly FcgammaRI) naturally expressed on macrophage-like cells.

Evaluation of bone marrow specimens with acute myelogenous leukemia for CD34, CD15, CD117, and myeloperoxidase.

PubMed

Dunphy, C H; Polski, J M; Evans, H L; Gardner, L J

2001-08-01

Immunophenotyping of bone marrow (BM) specimens with acute myelogenous leukemia (AML) may be performed by flow cytometric (FC) or immunohistochemical (IH) techniques. Some markers (CD34, CD15, and CD117) are available for both techniques. Myeloperoxidase (MPO) analysis may be performed by enzyme cytochemical (EC) or IH techniques. To determine the reliability of these markers and MPO by these techniques, we designed a study to compare the results of analyses of these markers and MPO by FC (CD34, CD15, and CD117), EC (MPO), and IH (CD34, CD15, CD117, and MPO) techniques. Twenty-nine AMLs formed the basis of the study. These AMLs all had been immunophenotyped previously by FC analysis; 27 also had had EC analysis performed. Of the AMLs, 29 had BM core biopsies and 26 had BM clots that could be evaluated. The paraffin blocks of the 29 BM core biopsies and 26 BM clots were stained for CD34, CD117, MPO, and CD15. These results were compared with results by FC analysis (CD34, CD15, and CD117) and EC analysis (MPO). Immunodetection of CD34 expression in AML had a similar sensitivity by FC and IH techniques. Immunodetection of CD15 and CD117 had a higher sensitivity by FC analysis than by IH analysis. Detection of MPO by IH analysis was more sensitive than by EC analysis. There was no correlation of French-American-British (FAB) subtype of AML with CD34 or CD117 expression. Expression of CD15 was associated with AMLs with a monocytic component. Myeloperoxidase reactivity by IH analysis was observed in AMLs originally FAB subtyped as M0. CD34 can be equally detected by FC and IH techniques. CD15 and CD117 are better detected by FC analysis and MPO is better detected by IH analysis.

Roles of Mas-related G protein-coupled receptor X2 on mast cell-mediated host defense, pseudoallergic drug reactions, and chronic inflammatory diseases.

PubMed

Subramanian, Hariharan; Gupta, Kshitij; Ali, Hydar

2016-09-01

Mast cells (MCs), which are granulated tissue-resident cells of hematopoietic lineage, contribute to vascular homeostasis, innate/adaptive immunity, and wound healing. However, MCs are best known for their roles in allergic and inflammatory diseases, such as anaphylaxis, food allergy, rhinitis, itch, urticaria, atopic dermatitis, and asthma. In addition to the high-affinity IgE receptor (FcεRI), MCs express numerous G protein-coupled receptors (GPCRs), which are the largest group of membrane receptor proteins and the most common targets of drug therapy. Antimicrobial host defense peptides, neuropeptides, major basic protein, eosinophil peroxidase, and many US Food and Drug Administration-approved peptidergic drugs activate human MCs through a novel GPCR known as Mas-related G protein-coupled receptor X2 (MRGPRX2; formerly known as MrgX2). Unique features of MRGPRX2 that distinguish it from other GPCRs include their presence both on the plasma membrane and intracellular sites and their selective expression in MCs. In this article we review the possible roles of MRGPRX2 on host defense, drug-induced anaphylactoid reactions, neurogenic inflammation, pain, itch, and chronic inflammatory diseases, such as urticaria and asthma. We propose that host defense peptides that kill microbes directly and activate MCs through MRGPRX2 could serve as novel GPCR targets to modulate host defense against microbial infection. Furthermore, mAbs or small-molecule inhibitors of MRGPRX2 could be developed for the treatment of MC-dependent allergic and inflammatory disorders. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

TIGIT expressing CD4+T cells represent a tumor-supportive T cell subset in chronic lymphocytic leukemia

PubMed Central

Catakovic, Kemal; Gassner, Franz Josef; Ratswohl, Christoph; Zaborsky, Nadja; Rebhandl, Stefan; Schubert, Maria; Steiner, Markus; Gutjahr, Julia Christine; Pleyer, Lisa; Egle, Alexander; Hartmann, Tanja Nicole; Greil, Richard; Geisberger, Roland

2018-01-01

ABSTRACT While research on T cell exhaustion in context of cancer particularly focuses on CD8+ cytotoxic T cells, the role of inhibitory receptors on CD4+ T-helper cells have remained largely unexplored. TIGIT is a recently identified inhibitory receptor on T cells and natural killer (NK) cells. In this study, we examined TIGIT expression on T cell subsets from CLL patients. While we did not observe any differences in TIGIT expression in CD8+ T cells of healthy controls and CLL cells, we found an enrichment of TIGIT+ T cells in the CD4+ T cell compartment in CLL. Intriguingly, CLL patients with an advanced disease stage displayed elevated numbers of CD4+ TIGIT+ T cells compared to low risk patients. Autologous CLL-T cell co-culture assays revealed that depleting CD4+ TIGIT+ expressing T cells from co-cultures significantly decreased CLL viability. Accordingly, a supportive effect of TIGIT+CD4+ T cells on CLL cells in vitro could be recapitulated by blocking the interaction of TIGIT with its ligands using TIGIT-Fc molecules, which also impeded the T cell specific production of CLL-prosurvival cytokines. Our data reveal that TIGIT+CD4+T cells provide a supportive microenvironment for CLL cells, representing a potential therapeutic target for CLL treatment. PMID:29296521

A benzenediamine derivative fc-99 attenuates lupus-like syndrome in MRL/lpr mice related to suppression of pDC activation.

PubMed

Ji, Jianjian; Fan, Hongye; Li, Fanlin; Li, Xiaojing; Dong, Guanjun; Gong, Wei; Song, Yuxian; Liu, Fei; Hua, Chunyan; Tan, Renxiang; Dou, Huan; Hou, Yayi

2015-12-01

Systemic lupus erythematosus (SLE) is an autoimmune disease with prominent chronic inflammatory aspects. Plasmacytoid dendritic cells (pDCs), which are the principal interferon-α (IFN-α)-producing cells, have known to be critically involved in SLE pathogenesis. Our previous research demonstrated that a benzenediamine derivative FC-99 possessed anti-inflammatory activities. However, the effects of FC-99 on SLE have not been investigated to date. In this study, we found that FC-99 attenuated lupus-like pathological symptoms and lupus nephritis as well as the expression of pro-inflammatory cytokines in kidneys of MRL/lpr mice. FC-99 also decreased both the total IgM, total IgG and anti-dsDNA IgG levels in sera and the activation of B cells in the PBMCs and spleens of MRL/lpr mice. Moreover, FC-99 inhibited the abnormal activation and number of pDCs from PBMCs and spleens and levels of IFN-α in MRL/lpr mice. Notably, FC-99 significantly suppressed the expression of IFN-inducible genes in peripheral blood mononuclear cells (PBMCs) and spleens from MRL/lpr mice. As expected, in vitro experiments demonstrated that FC-99 decreased both the activation and IFN-α production of pDCs and inhibited IRAK4 phosphorylation in pDCs upon TLR7 and TLR9 stimulation. We further confirm that the inhibition of FC-99 on B cell activation depended on level of pDCs-secreting IFN-α. These data indicate that FC-99 attenuated lupus-like syndrome in MRL/lpr mice related to suppression of pDC activation, especially pDCs-secreting IFN-α. This study suggests that FC-99 may be a potential therapeutic candidate for the treatment of SLE. Copyright © 2015 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

FC-99 ameliorates sepsis-induced liver dysfunction by modulating monocyte/macrophage differentiation via Let-7a related monocytes apoptosis.

PubMed

Zhao, Yarong; Zhu, Haiyan; Wang, Haining; Ding, Liang; Xu, Lizhi; Chen, Dai; Shen, Sunan; Hou, Yayi; Dou, Huan

2018-03-13

The liver is a vital target for sepsis-related injury, leading to inflammatory pathogenesis, multiple organ dysfunction and high mortality rates. Monocyte-derived macrophage transformations are key events in hepatic inflammation. N 1 -[(4-methoxy)methyl]-4-methyl-1,2-benzenediamine (FC-99) previously displayed therapeutic potential on experimental sepsis. However, the underlying mechanism of this protective effect is still not clear. FC-99 treatment attenuated the liver dysfunction in septic mice that was accompanied with reduced numbers of pro-inflammatory Ly6C hi monocytes in the peripheral blood and CD11b + F4/80 lo monocyte-derived macrophages in the liver. These effects were attributed to the FC-99-induced apoptosis of CD11b + cells. In PMA-differentiated THP-1 cells, FC-99 repressed the expression of CD11b, CD14 and caspase3 and resulted in a high proportion of Annexin V + cells. Moreover, let-7a-5p expression was abrogated upon CLP stimulation in vivo , whereas it was restored by FC-99 treatment. TargetScan analysis and luciferase assays indicated that the anti-apoptotic protein BCL-XL was targeted by let-7a-5p. BCL-XL was inhibited by FC-99 in order to induce monocyte apoptosis, leading to the impaired monocyte-to-macrophage differentiation. Murine acute liver failure was generated by caecal ligation puncture surgery after FC-99 administration; Blood samples and liver tissues were collected to determine the monocyte/macrophage subsets and the induction of apoptosis. Human acute monocytic leukemia cell line (THP-1) cells were pretreated with FC-99 followed by phorbol-12-myristate-13-acetate (PMA) stimulation, in order to induce monocyte-to-macrophage differentiation. The target of FC-99 and the mechanistic analyses were conducted by microarrays, qRT-PCR validation, TargetScan algorithms and a luciferase report assay. FC-99 exhibits potential therapeutic effects on CLP-induced liver dysfunction by restoring let-7a-5p levels.

The anti-tumor efficacy of 3C23K, a glyco-engineered humanized anti-MISRII antibody, in an ovarian cancer model is mainly mediated by engagement of immune effector cells

PubMed Central

Estupina, Pauline; Fontayne, Alexandre; Barret, Jean-Marc; Kersual, Nathalie; Dubreuil, Olivier; Le Blay, Marion; Pichard, Alexandre; Jarlier, Marta; Pugnière, Martine; Chauvin, Maëva; Chardès, Thierry; Pouget, Jean-Pierre; Deshayes, Emmanuel; Rossignol, Alexis; Abache, Toufik; de Romeuf, Christophe; Terrier, Aurélie; Verhaeghe, Lucie; Gaucher, Christine; Prost, Jean-François

2017-01-01

Ovarian cancer is the leading cause of death in women with gynecological cancers and despite recent advances, new and more efficient therapies are crucially needed. Müllerian Inhibiting Substance type II Receptor (MISRII, also named AMHRII) is expressed in most ovarian cancer subtypes and is a novel potential target for ovarian cancer immunotherapy. We previously developed and tested 12G4, the first murine monoclonal antibody (MAb) against human MISRII. Here, we report the humanization, affinity maturation and glyco-engineering steps of 12G4 to generate the Fc-optimized 3C23K MAb, and the evaluation of its in vivo anti-tumor activity. The epitopes of 3C23K and 12G4 were strictly identical and 3C23K affinity for MISRII was enhanced by a factor of about 14 (KD = 5.5 × 10−11 M vs 7.9 × 10−10 M), while the use of the EMABling® platform allowed the production of a low-fucosylated 3C23K antibody with a 30-fold KD improvement of its affinity to FcγRIIIa. In COV434-MISRII tumor-bearing mice, 3C23K reduced tumor growth more efficiently than 12G4 and its combination with carboplatin was more efficient than each monotherapy with a mean tumor size of 500, 1100 and 100 mm3 at the end of treatment with 3C23K (10 mg/kg, Q3-4D12), carboplatin (60 mg/kg, Q7D4) and 3C23K+carboplatin, respectively. Conversely, 3C23K-FcKO, a 3C23K form without affinity for the FcγRIIIa receptor, did not display any anti-tumor effect in vivo. These results strongly suggested that 3C23K mechanisms of action are mainly Fc-related. In vitro, antibody-dependent cytotoxicity (ADCC) and antibody-dependent cell phagocytosis (ADCP) were induced by 3C23K, as demonstrated with human effector cells. Using human NK cells, 50% of the maximal lysis was obtained with a 46-fold lower concentration of low-fucosylated 3C23K (2.9 ng/ml) than of 3C23K expressed in CHO cells (133.35 ng/ml). As 3C23K induced strong ADCC with human PBMC but almost none with murine PBMC, antibody-dependent cell phagocytosis (ADCP) was then investigated. 3C23K-dependent (100 ng/ml) ADCP was more active with murine than human macrophages (only 10% of living target cells vs. about 25%). These in vitro results suggest that the reduced ADCC with murine effectors could be partially balanced by ADCP activity in in vivo experiments. Taken together, these preclinical data indicate that 3C23K is a new promising therapeutic candidate for ovarian cancer immunotherapy and justify its recent introduction in a phase I clinical trial. PMID:28427157

Regulation of Monoclonal Antibody Immunotherapy by FcγRIIB.

PubMed

Stopforth, Richard J; Cleary, Kirstie L S; Cragg, Mark S

2016-05-01

Monoclonal antibodies (mAb) are revolutionising the treatment of many different diseases. Given their differing mode of action compared to most conventional chemotherapeutics and small molecule inhibitors, they possess the potential to be independent of common modes of treatment resistance and can typically be combined readily with existing treatments without dose-limiting toxicity. However, treatments with mAb rarely result in cure and so a full understanding of how these reagents work and can be optimised is key for their subsequent improvement. Here we review how an understanding of the biology of the inhibitory Fc receptor, FcγRIIB (CD32B), is leading to the development of improved mAb treatments.

Cleavage of the interchain disulfide bonds in rituximab increases its affinity for FcγRIIIA.

PubMed

Suzuki, Mami; Yamanoi, Ayaka; Machino, Yusuke; Kobayashi, Eiji; Fukuchi, Kaori; Tsukimoto, Mitsutoshi; Kojima, Shuji; Kohroki, Junya; Akimoto, Kazunori; Masuho, Yasuhiko

2013-07-05

The Fc region of human IgG1 mediates effector function via binding to Fcγ receptors and complement activation. The H and L chains of IgG1 antibodies are joined by four interchain disulfide bonds. In this study, these bonds within the therapeutic IgG1 rituximab (RTX) were cleaved either by mild reduction followed by alkylation or by mild S-sulfonation; consequently, two modified RTXs - A-RTX (alkylated) and S-RTX (S-sulfonated) - were formed, and both were almost as potent as unmodified RTX when binding CD20 antigen. Unexpectedly, each modified RTX had a higher binding affinity for FcγRIIIA (CD16A) than did unmodified RTX. However, S-RTX and A-RTX were each less potent than RTX in an assay of antibody-dependent cellular cytotoxicity (ADCC). In this ADCC assay, each modified RTX showed decreased secretion of granzyme B, but no change in perforin secretion, from effector cells. These results provide significant information on the structures within IgG1 that are involved in binding FcγRIIIA, and they may be useful in the development of therapeutic antagonists for FcγRIIIA. Copyright © 2013 Elsevier Inc. All rights reserved.

Anti-FcεR1 antibody injections activate basophils and mast cells and delay Type I diabetes onset in NOD mice

PubMed Central

Larson, David; Torrero, Marina N.; Mueller, Ellen; Shi, Yinghui; Killoran, Kristin

2012-01-01

Mounting evidence suggests that helminth infections protect against autoimmune diseases. As helminths cause chronic IgE-mediated activation of basophils and mast cells we hypothesized that continuous activation of these cells could prevents diabetes onset in nonobese diabetic (NOD) mice in the absence of infection. Anti-FcεR1 activated basophils and mast cells and resulted in the release of IL-4 and histamine into the bloodstream. Anti-FcεR1-treated NOD mice showed a type 2 shift in insulin-specific antibody production and exhibited significant delays in diabetes onset. IL-4 responses played a partial role as the protective effect of anti-FcεR1 therapy was diminished in IL-4-deficient NOD mice. In contrast, histamine signaling was not required as anti-FcεR1-mediated protection was not reduced in mice treated with histamine receptor blockers. These results demonstrate that anti-FcεR1 therapy delays diabetes onset in NOD mice and suggest that chronic basophil and mast cell activation may represent a new avenue of therapy for Th1-associated autoimmune diseases. PMID:21920822