Complement receptor type 1 (CR1) is a membrane receptor expressed on a wide range of cells. It is involved in immune complex clearance, phagocytosis, and complement regulation. Its ectodomain is composed of 30 complement control protein (CCP) modules, organized into four long homologous repeats (A-D). In addition to its main ligands C3b and C4b, CR1 was reported to interact with C1q and mannan-binding lectin (MBL) likely through its C-terminal region (CCP22-30). To decipher the interaction of human CR1 with the recognition proteins of the lectin complement pathway, a recombinant fragment encompassing CCP22-30 was expressed in eukaryotic cells, and its interaction with human MBL and ficolins was investigated using surface plasmon resonance spectroscopy. MBL and L-ficolin were shown to interact with immobilized soluble CR1 and CR1 CCP22-30 with apparent dissociation constants in the nanomolar range, indicative of high affinity. The binding site for CR1 was located at or near the MBL-associated serine protease (MASP) binding site in the collagen stalks of MBL and L-ficolin, as shown by competition experiments with MASP-3. Accordingly, the mutation of an MBL conserved lysine residue essential for MASP binding (K55) abolished binding to soluble CR1 and CCP22-30. The CR1 binding site for MBL/ficolins was mapped to CCP24-25 of long homologous repeat D using deletion mutants. In conclusion, we show that ficolins are new CR1 ligands and propose that MBL/L-ficolin binding involves major ionic interactions between conserved lysine residues of their collagen stalks and surface exposed acidic residues located in CR1 CCP24 and/or CCP25. PMID:23460739
Jacquet, Mickaël; Lacroix, Monique; Ancelet, Sarah; Gout, Evelyne; Gaboriaud, Christine; Thielens, Nicole M; Rossi, Véronique
In recent years, a `new' pathway for complement activation mediated by the mannose-binding lectin (MBL) has been described as a key mechanism for the mammalian acute phase response to infection. This complement activation pathway is initiated by a non-self recognition step: the binding of a humoral C-type lectin [mannose-binding lectin (MBL)] to microbial surfaces bearing `foreign' carbohydrate determinants. The recognition
Gerardo R. Vasta; Michael Quesenberry; Hafiz Ahmed; Nuala O'Leary
The complement system is a fundamental component of innate immunity that orchestrates complex immunological and inflammatory processes. Complement comprises over 30 proteins that eliminate invading microorganisms while maintaining host cell integrity. Protein-carbohydrate interactions play critical roles in both the activation and regulation of complement. Mannose-binding lectin (MBL) activates the lectin pathway of complement via the recognition of sugar arrays on pathogenic surfaces. To determine the solution structure of MBL, synchrotron x-ray scattering and analytical ultracentrifugation experiments showed that the carbohydrate-recognition domains in the MBL dimer, trimer, and tetramer are positioned close to each other in near-planar fan-like structures. These data were subjected to constrained modeling fits. A bent structure for the MBL monomer was identified starting from two crystal structures for its carbohydrate-recognition domain and its triple helical region. The MBL monomer structure was used to identify 10–12 near-planar solution structures for each of the MBL dimers, trimers, and tetramers starting from 900 to 6,859 randomized structures for each. These near-planar fan-like solution structures joined at an N-terminal hub clarified how the carbohydrate-recognition domain of MBL binds to pathogenic surfaces. They also provided insight on how MBL presents a structural template for the binding and auto-activation of the MBL-associated serine proteases to initiate the lectin pathway of complement activation.
Miller, Ami; Phillips, Anna; Gor, Jayesh; Wallis, Russell; Perkins, Stephen J.
Preeclampsia is a severe complication of pregnancy characterized by hypertension and proteinuria developing after midgestation. Previous studies have shown increased complement activation in normal and preeclamptic pregnancies. We aimed to investigate the role of the mannose-binding lectin pathway in the initiation of pathological complement activation observed in patients with preeclampsia. The study included 60 preeclamptic patients, 60 healthy pregnant women and 56 healthy non-pregnant women. Functional activity of the complex of mannose-binding lectin and mannose-binding lectin-associated serine protease 2 (MBL-MASP2 complex) was determined by ELISA. Circulating levels of complement components and C-reactive protein (CRP) were also measured. MBL-MASP2 activity was significantly higher in healthy pregnant than non-pregnant women. However, increased activity of the MBL-MASP2 complex in preeclamptic patients was not observed, compared to healthy pregnant women. MBL-MASP2 activity showed no relationship with either the levels of complement parameters, or with the clinical data and level of CRP in patients with preeclampsia. In conclusion, the complement system is activated with increased terminal complex formation in the third trimester of normal human pregnancy, and is further activated in preeclampsia as shown by the elevated amounts of activation markers. The activity of MBL-MASP2 is also increased in normal pregnancy, to the same level seen in preeclampsia. In our study, no relationship between MBL-MASP2 activity and extent of complement activation was observed in preeclampsia. We tentatively conclude, albeit without an evaluation of local placental concentrations, that the mannose-binding lectin pathway may play only a minor role in pathological complement activation during preeclampsia. PMID:20952075
Csuka, Dorottya; Molvarec, Attila; Derzsy, Zoltán; Varga, Lilian; Füst, George; Rigó, János; Prohászka, Zoltán
To initiate the lectin pathway of complement pattern recognition molecules bind to surface-linked carbohydrates or acetyl groups on pathogens or damaged self-tissue. This leads to activation of the serine proteases MASP-1 and MASP-2 resulting in deposition of C4 on the activator and assembly of the C3 convertase. In addition MASP-3 and the non-catalytic MAp19 and MAp44 presumably play regulatory functions, but the exact function of the MASP-3 protease remains to be established. Recent functional studies have significantly advanced our understanding of the molecular events occurring as activation progresses from pattern recognition to convertase assembly. Furthermore, atomic structures derived by crystallography or solution scattering of most proteins acting in the lectin pathway and two key complexes have become available. Here we integrate the current functional and structural knowledge concerning the lectin pathway proteins and derive overall models for their glycan bound complexes. These models are used to discuss cis- versus trans-activation of MASP proteases and the geometry of C4 deposition occurring on glycans in the lectin pathway. PMID:23911397
Kjaer, Troels R; Thiel, Steffen; Andersen, Gregers R
3MC syndrome has been proposed as a unifying term to integrate the overlapping Carnevale, Mingarelli, Malpuech and Michels syndromes. These rare autosomal recessive disorders of unknown cause comprise a spectrum of developmental features including characteristic facial dysmorphism, cleft lip and/or palate, craniosynostosis, learning disability, and genital, limb and vesicorenal anomalies. In a cohort of eleven 3MC families, we identified two mutated genes COLEC11 and MASP1 both of which encode proteins within the lectin complement pathway (CL-K1 and MASP-1 & ?3 respectively). CL-K1 is highly expressed in embryonic murine craniofacial cartilage, heart, bronchi, kidney, and vertebral bodies. Zebrafish morphants develop pigment defects and severe craniofacial abnormalities. Here, we show that CL-K1 serves as a key guidance cue for neural crest cell migration thus demonstrating for the first time, a role for complement pathway factors in fundamental developmental processes and the origin of 3MC syndrome.
Rooryck, Caroline; Diaz-Font, Anna; Osborn, Daniel P.S.; Chabchoub, Elyes; Hernandez-Hernandez, Victor; Shamseldin, Hanan; Kenny, Joanna; Waters, Aoife; Jenkins, Dagan; Kaissi, Ali Al; Leal, Gabriela F.; Dallapiccola, Bruno; Carnevale, Franco; Bitner-Glindzicz, Maria; Lees, Melissa; Hennekam, Raoul; Stanier, Philip; Burns, Alan J.; Peeters, Hilde; Alkuraya, Fowzan S; Beales, Philip L.
Aspergillus species are saprophytic molds causing life-threatening invasive fungal infections in the immunocompromised host. Innate immune recognition, in particular, the mechanisms of opsonization and complement activation, has been reported to be an integral part of the defense against fungi. We have shown that the complement component ficolin-A significantly binds to Aspergillus conidia and hyphae in a concentration-dependent manner and was inhibited by N-acetylglucosamine and N-acetylgalactosamine. Calcium-independent binding to Aspergillus fumigatus and A. terreus was observed, but binding to A. flavus and A. niger was calcium dependent. Ficolin-A binding to conidia was increased under low-pH conditions, and opsonization led to enhanced binding of conidia to A549 airway epithelial cells. In investigations of the lectin pathway of complement activation, ficolin-A-opsonized conidia did not lead to lectin pathway-specific C4 deposition. In contrast, the collectin mannose binding lectin C (MBL-C) but not MBL-A led to efficient lectin pathway activation on A. fumigatus in the absence of ficolin-A. In addition, ficolin-A opsonization led to a modulation of the proinflammatory cytokine interleukin-8. We conclude that ficolin-A may play an important role in the innate defense against Aspergillus by opsonizing conidia, immobilizing this fungus through enhanced adherence to epithelial cells and modulation of inflammation. However, it appears that other immune pattern recognition molecules, i.e., those of the collectin MBL-C, are involved in the Aspergillus-lectin complement pathway activation rather than ficolin-A. PMID:23478320
Bidula, Stefan; Kenawy, Hany; Ali, Youssif M; Sexton, Darren; Schwaeble, Wilhelm J; Schelenz, Silke
Lectin pathway activation of C3 is known to involve target recognition by mannan-binding lectin (MBL) or ficolins and generation of classical pathway C3 convertase via cleavage of C4 and C2 by MBL-associated serine protease 2 (MASP-2). We investigated C3 activation in C2-deficient human sera and in sera with other defined defects of complement to assess other mechanisms through which MBL might recruit complement. The capacity of serum to support C3 deposition was examined by ELISA using microtiter plates coated with O antigen–specific oligosaccharides derived from Salmonella typhimurium, S. thompson, and S. enteritidis corresponding to serogroups B, C, and D (BO, CO, and DO). MBL bound to CO, but not to BO and DO, and efficiently supported C3 deposition in the absence of C2, C4, or MASP-2. The existence of an MBL-dependent C2 bypass mechanism for alternative pathway–mediated C3 activation was clearly demonstrated using CO, solid-phase mannan, and E. coli LPS. MASP-1 might contribute, but was not required for C3 deposition in the model used. Independent of MBL, specific antibodies to CO supported C3 deposition through classical and alternative pathways. MBL-dependent C2 bypass activation could be particularly important in various inherited and acquired complement deficiency states.
Selander, Barbro; Martensson, Ulla; Weintraub, Andrej; Holmstrom, Eva; Matsushita, Misao; Thiel, Steffen; Jensenius, Jens C.; Truedsson, Lennart; Sjoholm, Anders G.
The salivary scavenger and agglutinin (SALSA), also known as gp340, salivary agglutinin and deleted in malignant brain tumor 1, is a 340-kDa glycoprotein expressed on mucosal surfaces and secreted into several body fluids. SALSA binds to a broad variety of microbes and endogenous ligands, such as complement factor C1q, surfactant proteins D and A, and IgA. Our search for novel ligands of SALSA by direct protein-interaction studies led to the identification of mannan-binding lectin (MBL) as a new binding partner. We observed that surface-associated SALSA activates complement via binding of MBL. On the other hand, soluble SALSA was found to inhibit Candida albicans-induced complement activation. Thus, SALSA has a dual complement activation modifying function. It activates the lectin pathway when bound to a surface and inhibits it when free in the fluid phase. These activities are mediated via a direct interaction with MBL. This suggests that SALSA could target the innate immune responses to certain microorganisms and simultaneously limit complement activation in the fluid phase.
Reichhardt, Martin P.; Loimaranta, Vuokko; Thiel, Steffen; Finne, Jukka; Meri, Seppo; Jarva, Hanna
Ficolins and one collectin, mannan-binding lectin (MBL), are the only factors known to activate the lectin pathway (LP) of complement. There is considerable circumstantial evidence that MBL insufficiency can increase susceptibility to various infections and influence the course of several non-infectious diseases complicated by infections. Much less information is available concerning l-ficolin. We report the results of a prospective study
Anna St. Swierzko; Anne P. M. Atkinson; Maciej Cedzynski; Shirley L. MacDonald; Agnieszka Szala; Iwona Domzalska-Popadiuk; Monika Borkowska-Klos; Aleksandra Jopek; Jerzy Szczapa; Misao Matsushita; Janusz Szemraj; Marc L. Turner; David C. Kilpatrick
Mannose-binding lectin-associated serine proteases-1/3 (MASP-1/3) are essential in activating the alternative pathway (AP) of complement through cleaving pro-factor D (pro-Df) into mature Df. MASP are believed to require binding to mannose binding lectins (MBL) or ficolins (FCN) to carry out their biological activities. Murine sera have been reported to contain MBL-A, MBL-C, and FCN-A, but not FCN-B that exists endogenously in monocytes and is thought not to bind MASP-1. We examined some possible mechanisms whereby MASP-1/3 might activate the AP. Collagen antibody-induced arthritis, a murine model of inflammatory arthritis dependent on the AP, was unchanged in mice lacking MBL-A, MBL-C, and FCN-A (MBL?/?/FCN A?/? mice) in comparison to wild-type mice. The in vitro induction of the AP by adherent mAb to collagen II was intact using sera from MBL?/?/FCN A?/? mice. Furthermore, sera from MBL?/?/FCN A?/? mice lacked pro-Df and possessed only mature Df. Gel filtration of sera from MBL?/?/FCN A?/? mice showed the presence of MASP-1 protein in fractions containing proteins smaller than the migration of MBL-A and MBL-C in sera from C4?/? mice, suggesting possible binding of MASP-1 to an unknown protein. Lastly, we show that FCN-B was present in the sera of MBL?/?/FCN A?/?mice and that it was bound to MASP-1. We conclude that MASP-1 does not require binding to MBL-A, MBL-C, or FCN-A to activate the AP. MASP-1 may cleave pro-Df into mature Df through binding to FCN-B or to an unknown protein, or may function as an unbound soluble protein.
Banda, Nirmal K.; Takahashi, Minoru; Takahashi, Kazue; Stahl, Gregory L.; Hyatt, Stephanie; Glogowska, Magdalena; Wiles, Timothy A.; Endo, Yuichi; Fujita, Teizo; Holers, V. Michael; Arend, William P.
Uncontrolled activation of the alternative complement pathway (AP) is thought to be associated with age-related macular degeneration. Previously, we have shown that in retinal pigmented epithelial (RPE) monolayers, oxidative stress reduced complement inhibition on the cell surface, resulting in sublytic complement activation and loss of transepithelial resistance (TER), but the potential ligand and pathway involved are unknown. ARPE-19 cells were grown as monolayers on transwell plates, and sublytic complement activation was induced with H2O2 and normal human serum. TER deteriorated rapidly in H2O2-exposed monolayers upon adding normal human serum. Although the effect required AP activation, AP was not sufficient, because elimination of MASP, but not C1q, prevented TER reduction. Reconstitution experiments to unravel essential components of the lectin pathway (LP) showed that both ficolin and mannan-binding lectin can activate the LP through natural IgM antibodies (IgM-C2) that recognize phospholipid cell surface modifications on oxidatively stressed RPE cells. The same epitopes were found on human primary embryonic RPE monolayers. Likewise, mouse laser-induced choroidal neovascularization, an injury that involves LP activation, could be increased in antibody-deficient rag1(-/-) mice using the phospholipid-specific IgM-C2. In summary, using a combination of depletion and reconstitution strategies, we have shown that the LP is required to initiate the complement cascade following natural antibody recognition of neoepitopes, which is then further amplified by the AP. LP activation is triggered by IgM bound to phospholipids. Taken together, we have defined novel mechanisms of complement activation in oxidatively stressed RPE, linking molecular events involved in age-related macular degeneration, including the presence of natural antibodies and neoepitopes. PMID:23493397
Joseph, Kusumam; Kulik, Liudmila; Coughlin, Beth; Kunchithapautham, Kannan; Bandyopadhyay, Mausumi; Thiel, Steffen; Thielens, Nicole M; Holers, V Michael; Rohrer, Bärbel
L-Ficolin/Mannose-Binding Lectin-Associated Serine Protease Complexes Bind to Group B Streptococci Primarily through N-Acetylneuraminic Acid of Capsular Polysaccharide and Activate the Complement Pathway?
Group B streptococci (GBS) are the most common cause of neonatal sepsis and meningitis. Most infants who are colonized with GBS at birth do not develop invasive disease, although many of these uninfected infants lack protective levels of capsular polysaccharide (CPS)-specific antibody. The lectin pathway of complement is a potential mechanism for initiating opsonization of GBS with CPS-specific antibody-deficient serum. In this study, we determined whether mannose-binding lectin (MBL)/MBL-associated serine protease (MASP) complexes and L-ficolin/MASP complexes bind to different strains of GBS to activate the lectin pathway, and we identified the molecules recognized by lectins on the GBS surface. We found that MBL did not bind to any GBS examined, whereas L-ficolin bound to GBS cells of many serotypes. L-ficolin binding to GBS cells correlated with the CPS content in serotypes Ib, III (restriction digestion pattern types III-2 and III-3), and V but not with the group B-specific polysaccharide (GBPS) content or with the lipoteichoic acid (LTA) content. L-ficolin bound to purified CPS and GBPS in a concentration-dependent manner but not to purified LTA. All strains to which L-ficolin/MASP complexes bound consumed C4. When N-acetylneuraminic acid (NeuNAc) was selectively removed from GBS cells by treatment with neuraminidase, the reduction in L-ficolin binding was correlated with the amount of NeuNAc removed. Additionally, L-ficolin was able to bind to wild-type strains but was able to bind only weakly to unencapsulated mutants and a mutant strain in which the CPS lacks NeuNAc. We concluded that L-ficolin/MASP complexes bind to GBS primarily through an interaction with NeuNAc of CPS.
Aoyagi, Youko; Adderson, Elisabeth E.; Rubens, Craig E.; Bohnsack, John F.; Min, Jin G.; Matsushita, Misao; Fujita, Teizo; Okuwaki, Yoshiyuki; Takahashi, Shinji
ABSTRACT Mannose-binding lectin (MBL) is a key soluble pathogen recognition protein of the innate immune system that binds specific mannose-containing glycans on the surfaces of microbial agents and initiates complement activation via the lectin pathway. Prior studies showed that MBL-dependent activation of the complement cascade neutralized insect cell-derived West Nile virus (WNV) in cell culture and restricted pathogenesis in mice. Here, we investigated the antiviral activity of MBL in infection by dengue virus (DENV), a related flavivirus. Using a panel of naïve sera from mouse strains deficient in different complement components, we showed that inhibition of infection by insect cell- and mammalian cell-derived DENV was primarily dependent on the lectin pathway. Human MBL also bound to DENV and neutralized infection of all four DENV serotypes through complement activation-dependent and -independent pathways. Experiments with human serum from naïve individuals with inherent variation in the levels of MBL in blood showed a direct correlation between the concentration of MBL and neutralization of DENV; samples with high levels of MBL in blood neutralized DENV more efficiently than those with lower levels. Our studies suggest that allelic variation of MBL in humans may impact complement-dependent control of DENV pathogenesis.
Avirutnan, Panisadee; Hauhart, Richard E.; Marovich, Mary A.; Garred, Peter; Atkinson, John P.; Diamond, Michael S.
Summary The Lyme disease agent, Borrelia burgdorferi, is primarily transmitted to vertebrates by Ixodes ticks. The classical and alternative complement pathways are important in Borrelia eradication by the vertebrate host. We recently identified a tick salivary protein, designated P8 that reduced complement-mediated killing of Borrelia. We now discover that P8 interferes with the human lectin complement cascade resulting in impaired neutrophil phagocytosis and chemotaxis, and diminished Borrelia lysis. Therefore, P8 was renamed the lectin complement pathway inhibitor (TSLPI). TSLPI-silenced ticks, or ticks exposed to TSLPI-immune mice, were hampered in Borrelia transmission. Moreover, Borrelia acquisition and persistence in tick midguts was impaired in ticks feeding on TSLPI-immunized B. burgdorferi-infected mice. Together, our findings suggest an essential role for the lectin complement cascade in Borrelia eradication and demonstrate how a vector-borne pathogen co-opts a vector protein to facilitate early mammalian infection and vector colonization.
Schuijt, Tim J.; Coumou, Jeroen; Narasimhan, Sukanya; Dai, Jianfeng; DePonte, Kathleen; Wouters, Diana; Brouwer, Mieke; Oei, Anneke; Roelofs, Joris J.T.H.; van Dam, Alje P.; van der Poll, Tom; van 't Veer, Cornelis; Hovius, Joppe W.; Fikrig, Erol
Mannose-binding lectin (MBL) is a C-type lectin involved in the first line of host defense against pathogens and it requires MBL-associated serine protease (MASP) for activation of the complement lectin pathway. To elucidate the origin and evolution of MBL, MBL-like lectin was isolated from the plasma of a urochordate, the solitary ascidian Halocynthia roretzi, using affinity chromatography on a yeast mannan-Sepharose. SDS-PAGE of the eluted proteins revealed a major band of approximately 36 kDa (p36). p36 cDNA was cloned from an ascidian hepatopancreas cDNA library. Sequence analysis revealed that the carboxy-terminal half of the ascidian lectin contains a carbohydrate recognition domain (CRD) that is homologous to C-type lectin, but it lacks a collagen-like domain that is present in mammalian MBLs. Purified p36 binds specifically to glucose but not to mannose or N-acetylglucosamine, and it was designated glucose-binding lectin (GBL). The two ascidian MASPs associated with GBL activate ascidian C3, which had been reported to act as an opsonin. The removal of GBL-MASPs complex from ascidian plasma using Ab against GBL inhibits C3-dependent phagocytosis. These observations strongly suggest that GBL acts as a recognition molecule and that the primitive complement system, consisting of the lectin-proteases complex and C3, played a major role in innate immunity before the evolution of an adaptive immune system in vertebrates. PMID:11591777
Sekine, H; Kenjo, A; Azumi, K; Ohi, G; Takahashi, M; Kasukawa, R; Ichikawa, N; Nakata, M; Mizuochi, T; Matsushita, M; Endo, Y; Fujita, T
Mannose-binding lectin (MBL) is a member of the collectin protein family that binds a broad range of microorganisms and activates\\u000a the lectin-complement pathway of innate immunity. MBL deficiency is associated with an increased risk for various infections\\u000a and arises from five polymorphisms in the promoter and first exon of the MBL gene in humans. In this study, three novel single-nucleotide
Jianbo Liu; Zhihua Ju; Qiuling Li; Jinming Huang; Rongling Li; Jiangbin Li; Lijuan Ma; Jifeng Zhong; Changfa Wang
Complement activation was assessed in 34 patients undergoing cardiopulmonary bypass. Arterial concentrations of complement fragments Ba and C3d rose in all patients, the increase in Ba preceding that of C3d. At the same time as complement fragments were being generated the arterial neutrophil count fell. These findings suggest (a) that complement activation is initiated by the alternative pathway during cardiopulmonary bypass and (b) that complement activation mediates loss of neutrophils during bypass. Complement mediated loss of neutrophils during the analogous setting of haemodialysis is the result of leucosequestration in the pulmonary vasculature. During cardiopulmonary bypass the lungs are out of circuit, so that activated leucocytes may sequester in other target organs. This may be an aetiological factor in the multi-organ failure occasionally seen after uneventful cardiopulmonary bypass.
Collett, B; Alhaq, A; Abdullah, N B; Korjtsas, L; Ware, R J; Dodd, N J; Alimo, E; Ponte, J; Vergani, D
Studies in rodent models suggested that complement may play a critical role in susceptibility to airway hyperresponsiveness (AHR) and as a mediator of bronchial obstruction and inflammation in asthma. Complement may participate in susceptibility to asthma because of an intrinsic abnormality in complement activation and generation of C3a, C5a, or other products that affect cellular responses, resulting in T(H)2 predominance and asthma susceptibility. Alternatively, an intrinsic abnormality in the cellular response to complement activation products could determine susceptibility to asthma. In this study, the authors investigated whether complement in patients with atopic asthma versus nonatopic controls possesses an increased propensity to become activated. Despite reports that total complement plasma levels in unchallenged asthmatics are normal, an abnormal sensitivity of complement to activation may exist if an isoform or a polymorphic variant of a complement protein was present and resulted in gain or loss of function without associated changes in total complement levels. Therefore, complement activation was induced in vitro in plasma of asthmatics and controls using activators of the classical, alternative, and lectin pathways and measured C3a, other C3 fragments, and C5a. For each pathway, similar amounts of generated fragments, as well as C3a/C3 and C5a/C5 ratios, were found in asthmatics and controls. Also, similar basal plasma levels of C3a and C5a were found in both groups; however, mannan-binding lectin (MBL) levels were moderately elevated in asthmatics. In conclusion, the results suggest that, in asthmatic patients, complement activation does not exhibit an abnormal sensitivity to activation by any of the known activation pathways. PMID:17002917
Wust, Sven K; Blumenthal, Malcolm N; Corazalla, Edward O; Benson, Barbara A; Dalmasso, Agustin P
Serum antibodies and mannose-binding lectin (MBL) are important host defense factors for host adaptive and innate immunity, respectively. Antibodies and MBL also initiate the classical and lectin complement pathways, respectively, leading to opsonophagocytosis. We have shown previously that Staphylococcus aureus wall teichoic acid (WTA), a cell wall glycopolymer consisting of ribitol phosphate substituted with ?- or ?-O-N-acetyl-d-glucosamine (GlcNAc) and d-alanine, is recognized by MBL and serum anti-WTA IgG. However, the exact antigenic determinants to which anti-WTA antibodies or MBL bind have not been determined. To answer this question, several S. aureus mutants, such as ?-GlcNAc glycosyltransferase-deficient S. aureus ?tarM, ?-GlcNAc glycosyltransferase-deficient ?tarS, and ?tarMS double mutant cells, were prepared from a laboratory and a community-associated methicillin-resistant S. aureus strain. Here, we describe the unexpected finding that ?-GlcNAc WTA-deficient ?tarS mutant cells (which have intact ?-GlcNAc) escape from anti-WTA antibody-mediated opsonophagocytosis, whereas ?-GlcNAc WTA-deficient ?tarM mutant cells (which have intact ?-GlcNAc) are efficiently engulfed by human leukocytes via anti-WTA IgG. Likewise, MBL binding in S. aureus cells was lost in the ?tarMS double mutant but not in either single mutant. When we determined the serum concentrations of the anti-?- or anti-?-GlcNAc-specific WTA IgGs, anti-?-GlcNAc WTA-IgG was dominant in pooled human IgG fractions and in the intact sera of healthy adults and infants. These data demonstrate the importance of the WTA sugar conformation for human innate and adaptive immunity against S. aureus infection. PMID:24045948
Kurokawa, Kenji; Jung, Dong-Jun; An, Jang-Hyun; Fuchs, Katharina; Jeon, Yu-Jin; Kim, Na-Hyang; Li, Xuehua; Tateishi, Koichiro; Park, Ji Ae; Xia, Guoqing; Matsushita, Misao; Takahashi, Kazue; Park, Hee-Ju; Peschel, Andreas; Lee, Bok Luel
Scabies is a parasitic infestation of the skin by the mite Sarcoptes scabiei that causes significant morbidity worldwide, in particular within socially disadvantaged populations. In order to identify mechanisms that enable the scabies mite to evade human immune defenses, we have studied molecules associated with proteolytic systems in the mite, including two novel scabies mite serine protease inhibitors (SMSs) of the serpin superfamily. Immunohistochemical studies revealed that within mite-infected human skin SMSB4 (54 kDa) and SMSB3 (47 kDa) were both localized in the mite gut and feces. Recombinant purified SMSB3 and SMSB4 did not inhibit mite serine and cysteine proteases, but did inhibit mammalian serine proteases, such as chymotrypsin, albeit inefficiently. Detailed functional analysis revealed that both serpins interfered with all three pathways of the human complement system at different stages of their activation. SMSB4 inhibited mostly the initial and progressing steps of the cascades, while SMSB3 showed the strongest effects at the C9 level in the terminal pathway. Additive effects of both serpins were shown at the C9 level in the lectin pathway. Both SMSs were able to interfere with complement factors without protease function. A range of binding assays showed direct binding between SMSB4 and seven complement proteins (C1, properdin, MBL, C4, C3, C6 and C8), while significant binding of SMSB3 occurred exclusively to complement factors without protease function (C4, C3, C8). Direct binding was observed between SMSB4 and the complement proteases C1s and C1r. However no complex formation was observed between either mite serpin and the complement serine proteases C1r, C1s, MASP-1, MASP-2 and MASP-3. No catalytic inhibition by either serpin was observed for any of these enzymes. In summary, the SMSs were acting at several levels mediating overall inhibition of the complement system and thus we propose that they may protect scabies mites from complement-mediated gut damage.
Mika, Angela; Reynolds, Simone L.; Mohlin, Frida C.; Willis, Charlene; Swe, Pearl M.; Pickering, Darren A.; Halilovic, Vanja; Wijeyewickrema, Lakshmi C.; Pike, Robert N.; Blom, Anna M.; Kemp, David J.; Fischer, Katja
Scabies is a parasitic infestation of the skin by the mite Sarcoptes scabiei that causes significant morbidity worldwide, in particular within socially disadvantaged populations. In order to identify mechanisms that enable the scabies mite to evade human immune defenses, we have studied molecules associated with proteolytic systems in the mite, including two novel scabies mite serine protease inhibitors (SMSs) of the serpin superfamily. Immunohistochemical studies revealed that within mite-infected human skin SMSB4 (54 kDa) and SMSB3 (47 kDa) were both localized in the mite gut and feces. Recombinant purified SMSB3 and SMSB4 did not inhibit mite serine and cysteine proteases, but did inhibit mammalian serine proteases, such as chymotrypsin, albeit inefficiently. Detailed functional analysis revealed that both serpins interfered with all three pathways of the human complement system at different stages of their activation. SMSB4 inhibited mostly the initial and progressing steps of the cascades, while SMSB3 showed the strongest effects at the C9 level in the terminal pathway. Additive effects of both serpins were shown at the C9 level in the lectin pathway. Both SMSs were able to interfere with complement factors without protease function. A range of binding assays showed direct binding between SMSB4 and seven complement proteins (C1, properdin, MBL, C4, C3, C6 and C8), while significant binding of SMSB3 occurred exclusively to complement factors without protease function (C4, C3, C8). Direct binding was observed between SMSB4 and the complement proteases C1s and C1r. However no complex formation was observed between either mite serpin and the complement serine proteases C1r, C1s, MASP-1, MASP-2 and MASP-3. No catalytic inhibition by either serpin was observed for any of these enzymes. In summary, the SMSs were acting at several levels mediating overall inhibition of the complement system and thus we propose that they may protect scabies mites from complement-mediated gut damage. PMID:22792350
Mika, Angela; Reynolds, Simone L; Mohlin, Frida C; Willis, Charlene; Swe, Pearl M; Pickering, Darren A; Halilovic, Vanja; Wijeyewickrema, Lakshmi C; Pike, Robert N; Blom, Anna M; Kemp, David J; Fischer, Katja
The nature of the fl inhibitor in guinea-pig serum and its mechanism of neutralization of influenza virus have been investigated. This inhibitor was shown to be a mannose- binding lectin serologically related to human serum mannose-binding protein. CaZ+-dependent binding of the guinea-pig lectin to influenza virus or to mannan could be detected with polyclonal or monoclonal antibodies against human mannose-binding
E. Margot Anders; Carol A. Hartley; Patrick C. Reading; R. A. B. Ezekowitz
Major basic protein, the primary constituent of eosinophil granules, regulates the alternative and classical pathways of complement. Major basic protein and other eosinophil granule cationic proteins, which are important in mediating tissue damage in allergic disease, regulate the alternative pathway by interfering with C3b interaction with factor B to assemble an alternative pathway C3 convertase. In the present study, eosinophil peroxidase, eosinophil cationic protein and eosinophil-derived neurotoxin, as well as major basic protein, were examined for capacity to regulate the classical pathway. Eosinophil peroxidase, eosinophil cationic protein and major basic protein inhibited formation of cell-bound classical pathway C3 convertase (EAC1,4b,2a), causing 50% inhibition of complement-mediated lysis at about 0.19, 0.75 and 0.5 micrograms/10(7) cellular intermediates, respectively. Eosinophil-derived neurotoxin had no activity on this pathway of complement. The eosinophil granule proteins were examined for activity on the formation of the membrane attack complex. Major basic protein and eosinophil cationic protein had no activity on terminal lysis. In contrast, eosinophil peroxidase inhibited lysis of EAC1,4b,2a,3b,5b, but had only minimal activity on later events in complement lysis. These polycations were then examined to determine the site(s) at which they regulated the early classical pathway. Eosinophil granule polycationic proteins: (1) reduced the Zmax at all time points but had only minimal effect on the Tmax during the formation of the classical pathway C3 convertase (EAC1,4b,2a); (2) inhibited formation of EAC1,4b,2a proportional to C4 but independent of C2 concentration; (3) inhibited fluid phase formation of C1,4b,2a, as reflected by a decrease in C1-induced consumption of C2 over time; and (4) inhibited C1 activity over time without a direct effect on either C4 or C2. These observations suggest that polycations regulate the early classical pathway by interfering with C1 and may exert this activity in vivo.
Weiler, J M; Edens, R E; Bell, C S; Gleich, G J
Mannose-binding lectin (MBL) is a member of the collectin protein family that binds a broad range of microorganisms and activates the lectin-complement pathway of innate immunity. MBL deficiency is associated with an increased risk for various infections and arises from five polymorphisms in the promoter and first exon of the MBL gene in humans. In this study, three novel single-nucleotide polymorphisms (SNPs) in the promoter region and two previously reported SNPs in exon 2 of the MBL1 gene were detected using PCR single-strand conformation polymorphism, restriction fragment length polymorphism, and DNA sequencing in 537 cattle from three Chinese breeds. Analysis of the genotypes and haplotypes was used to investigate the polymorphisms and their possible implications, especially their association with serum MBL-A levels, complement activity (CH50 and ACH50), and milk production traits was investigated. The g.2651G > A SNP in exon 2 affected the serum MBL-A concentrations and the serum CH50 values, whereas the g.-1330G > A SNP significantly affected CH50 and the somatic cell scores (SCSs). Statistical analysis revealed that cows with the ATGGC/ACAAC combined genotype and those with the AAGGT/ACGGT combined genotype exhibited the lowest and highest SCSs, respectively. Serum antibacterial activities were also conducted to verify the effect of the SNPs on resistance to mastitis pathogens. Results of real-time PCR showed that the liver of cows with clinical mastitis exhibited a higher MBL1 expression compared with healthy ones (P ? 0.05). Findings of this study indicate that the MBL1 gene possibly contributes to bacterial infection resistance and can be used as a molecular marker of milk production traits to control mastitis. PMID:21695551
Liu, Jianbo; Ju, Zhihua; Li, Qiuling; Huang, Jinming; Li, Rongling; Li, Jiangbin; Ma, Lijuan; Zhong, Jifeng; Wang, Changfa
Tannerella forsythia is a poorly studied pathogen despite being one of the main causes of periodontitis, which is an inflammatory disease of the supporting structures of the teeth. We found that despite being recognized by all complement pathways T. forsythia is resistant to killing by human complement, which is present at up to 70% of serum concentration in gingival crevicular fluid. Incubation of human serum with karilysin, a metalloproteinase of T. forsythia, resulted in a decrease in bactericidal activity of the serum. T. forsythia strains expressing karilysin at higher levels were more resistant than low expressing strain. Furthermore, the low expressing strain was significantly more opsonized with C3b and membrane attack complex from serum compared to the other strains. The high expressing strain was more resistant to killing in human blood. The protective effect of karilysin against serum bactericidal activity was attributable to its ability to inhibit complement at several stages. The classical and lectin complement pathways were inhibited due to the efficient degradation of mannose-binding lectin, ficolin-2, ficolin-3 and C4 by karilysin, while inhibition of the terminal pathway was caused by degradation of C5. Interestingly, karilysin was able to release biologically active C5a peptide in human plasma and induce migration of neutrophils. Importantly, we detected the karilysin gene in over 90% of gingival crevicular fluid samples containing T. forsythia obtained from patients with periodontitis. Taken together, the newly characterized karilysin appears to be an important virulence factor of T. forsythia and might have several important implications for immune evasion.
Jusko, Monika; Potempa, Jan; Karim, Abdulkarim Y.; Ksiazek, Miroslaw; Riesbeck, Kristian; Garred, Peter; Eick, Sigrun; Blom, Anna M.
Adult tissue plasticity, cell reprogramming, and organ regeneration are major challenges in the field of modern regenerative medicine. Devising strategies to increase the regenerative capacity of tissues holds great promise for dealing with donor organ shortages and low transplantation outcomes and also provides essential impetus to tissue bioengineering approaches for organ repair and replacement. The inherent ability of cells to reprogram their fate by switching into an embryonic-like, pluripotent progenitor state is an evolutionary vestige that in mammals has been retained mostly in fetal tissues and persists only in a few organs of the adult body. Tissue regeneration reflects the capacity of terminally differentiated cells to re-enter the cell cycle and proliferate in response to acute injury or environmental stress signals. In lower vertebrates, this regenerative capacity extends to several organs and remarkably culminates in precise tissue patterning, through cellular transdifferentiation and complex morphogenetic processes that can faithfully reconstruct entire body parts. Many lessons have been learned from robust regeneration models in amphibians such as the newt and axolotl. However, the dynamic interactions between the regenerating tissue, the surrounding stroma, and the host immune response, as it adapts to the actively proliferating tissue, remain ill-defined. The regenerating zone, through a sequence of distinct molecular events, adopts phenotypic plasticity and undergoes rigorous tissue remodeling that, in turn, evokes a significant inflammatory response. Complement is a primordial sentinel of the innate immune response that engages in multiple inflammatory cascades as it becomes activated during tissue injury and remodeling. In this respect, complement proteins have been implicated in tissue and organ regeneration in both urodeles and mammals. Distinct complement-triggered pathways have been shown to modulate critical responses that promote tissue reprogramming, pattern formation, and regeneration across phylogenesis. This article will discuss the mechanistic insights underlying the crosstalk of complement with cytokine and growth factor signaling pathways that drive tissue regeneration and will provide a unified conceptual framework for considering complement modulation as a novel target for regenerative therapeutics. PMID:23684626
Mastellos, Dimitrios C; Deangelis, Robert A; Lambris, John D
Melanins are complex biological pigments formed by the oxidative polymerization of phenolic and/or indolic compounds. These pigments have been implicated in the pathogenesis of some microbial infections, malignancies, degenerative disorders, and autoimmune diseases. Recent studies have demonstrated that melanins have antigenic and anti-inflammatory properties. These findings led us to further explore the interaction of melanins with the immune system. Melanin particles ("ghosts") were isolated from in vitro-melanized Cryptococcus neoformans cells and Aspergillus niger conidia and then incubated in normal human serum containing (125)I-labeled complement C3. The results demonstrated deposition of C3 fragments onto the melanin ghosts as early as 1 min after incubation, with maximum deposition occurring after 12 min for C. neoformans-derived melanin ghosts and after 25 min for A. niger-derived melanin ghosts. The blocking of classical pathway activation did not affect the kinetics or total deposition of C3 onto the melanin ghosts, indicating that melanins activate complement through the alternative pathway. Immunofluorescence analysis of lungs from BALB/c mice injected intratracheally with C. neoformans-derived melanin ghosts demonstrated deposition of C3 fragments onto the ghosts. Small granulomas were also observed surrounding the ghosts. However, melanization of the C. neoformans cell wall did not alter the kinetics or total deposition of C3 fragments onto the fungal cells. The finding that melanin surfaces can activate the complement system suggests a potential mechanism for the pathogenesis of some degenerative and/or autoimmune processes that involve melanized cells as well as another potential role for melanin in the virulence of melanin-producing microorganisms. PMID:11777844
Rosas, A L; MacGill, R S; Nosanchuk, J D; Kozel, T R; Casadevall, A
Immune complex-mediated complement activation through the classic pathway plays a key role in the pathogenesis of lupus nephritis (LN). C4d deposition in renal tissue reflects the prognosis of systemic lupus erythematosus (SLE). The aim of the current study is to investigate the pathogenesis and clinicopathologic significance of glomerular C4d deposition in LN. We retrospectively analyzed clinical and histopathological data of 20 SLE patients with renal biopsy-proven LN and 10 non-SLE renal biopsy samples as control. LN biopsies showed varying degrees of glomerular C4d staining associated with immune complex deposits, IgG (p = 0.015), C1q (p = 0.032) and C3 (p = 0.049). 7 LN biopsies had all of C4d, C1q and C3 deposits in their glomeruli, indicative of the activation of the classical pathway, whereas 2 LN biopsies had C4d and C3 deposits without accompanying C1q deposits, indicating the activation of the lectin pathway. Glomerular C4d deposition was correlated with the LN subtype (p < 0.001). In particular, a diffusely intense and coarsely granular pattern of C4d deposition in all glomeruli was detected in class V membranous LN. However, glomerular C4d deposition was correlated with neither disease activity of SLE nor histological activity and chronicity of LN. In conclusion, the activation of the lectin pathway as well as the classical pathway seems to play a crucial role in the pathogenesis of LN. Glomerular C4d staining could be helpful for diagnosing class V membranous LN, although glomerular C4d deposition does not reflect SLE disease activity and histological activity and chronicity.
Kim, Min-Kyung; Maeng, Young-In; Lee, Sun-Jae; Lee, In Hee; Bae, Jisuk; Kang, Yu-Na; Park, Byung-Tae; Park, Kwan-Kyu
Background Mannose binding lectin (MBL) is an important host defence protein against opportunistic fungal pathogens. This carbohydrate-binding protein, an opsonin and lectin pathway activator, binds through multiple lectin domains to the repeating sugar arrays displayed on the surface of a wide range of clinically relevant microbial species. We investigated the contribution of MBL to antifungal innate immunity towards C. parapsilosis in vitro. Results High avidity binding was observed between MBL and C. albicans and C. parapsilosis. Addition of MBL to MBL deficient serum increased the deposition of C4 and C3b and enhanced the uptake of C. albicans, C. parapsilosis and acapsular C. neoformans by polymorphonuclear cells (PMNs). Compared to other microorganisms, such as Escherichia coli, Staphylococcus aureus and Cryptococcus neoformans, C. parapsilosis and Candida albicans were potent activators of the lectin pathway. Conclusion Our results suggest that MBL plays a crucial role in the innate immunity against infections caused by yeast by increasing uptake by PMN.
van Asbeck, Eveline C; Hoepelman, Andy IM; Scharringa, Jelle; Herpers, Bjorn L; Verhoef, Jan
The cuticular surface of the infectious third-stage larvae of Nematospiroides dubius activates complement via the alternative pathway. Sensitisation of larvae with complement or with antibodies from the serum of immune mice (resistant to reinfection) promoted the adherence of mouse peritoneal exudate cells to the larval cuticle during incubation in vitro. The infectivity of larvae sensitised with antibody or complement was
SJ Prowse; PL Ey; CR Jenkin
Innate immunity is constructed around genetically encoded receptors that survey the intracellular and extracellular environments for signs of invading microorganisms. These receptors recognise the invader and through complex intracellular networks of molecular signaling, they destroy the threat whilst instructing effective adaptive immune responses. Many of these receptors, like the Toll-like receptors in particular, are well-known for their ability to mediate downstream responses upon recognition of exogenous or endogenous ligands; however, the emerging family known as the C-type lectin-like receptors contains many members that have a huge impact on immune and homeostatic regulation. Of particular interest here are the C-type lectin-like receptors that make up the Dectin-1 cluster and their intracellular signaling motifs that mediate their functions. In this review, we aim to draw together current knowledge of ligands, motifs and signaling pathways, present downstream of Dectin-1 cluster receptors, and discuss how these dictate their role within biological systems.
Plato, Anthony; Willment, Janet A.
Previous research on complement activation in the Alzheimer's disease (AD) brain has focused almost exclusively on the classical complement pathway. The alternative pathway represents another important arm for complement activation, converging with the classical cascade at the C5 cleavage step. Here, we show that mRNA for a critical alternative pathway component, factor B, is present in AD frontal cortex and that the factor D cleaved split products of factor B, Bb and Ba, are significantly increased, indicating alternative pathway activation. By contrast, the two major inhibitors of alternative pathway activation, factor H and factor I, are present at the level of mRNA and protein but are not significantly upregulated. Immunohistochemical analysis reveals significant positive staining in AD sections for all three components. Taken together with previous reports demonstrating alternative pathway activation by amyloid beta peptide, these findings suggest that conditions conducive to chronic alternative pathway activation may exist in the AD brain. PMID:11000474
Strohmeyer, R; Shen, Y; Rogers, J
A large proportion of the population is exposed to infectious agents and yet few succumb to disease for, as yet, undetermined reasons. Mannose binding lectin (MBL) plays a key role in the host response to infection through the activation of the lectin complement pathway and probably through acting as an opsin. Variations in the level of circulating MBL are observed,
Martin L. Hibberd; John A Summerfield; Michael Levin
The study demonstrates the ability of human autologous RBC stroma to activate the complement system via the recently described alternate pathway (C3-Activator System, Properdin System). Hemoglobin-free and hemoglobin-containing RBC stroma were prepared by...
B. J. Lunskis P. Fortwengler T. R. Poskitt
The strongest susceptibility genes for the development of systemic lupus erythematosus (SLE) in humans are null mutants of classical pathway complement proteins. There is a hierarchy of disease susceptibility and severity according to the position of the missing protein in the activation pathway, with the severest disease associated with C1q deficiency. Here we demonstrate, using novel in vivo models of apoptotic cell clearance during sterile peritonitis, a similar hierarchical role for classical pathway complement proteins in vivo in the clearance of apoptotic cells by macrophages. Our results constitute the first demonstration of an impairment in the phagocytosis of apoptotic cells by macrophages in vivo in a mammalian system. Apoptotic cells are thought to be a major source of the autoantigens of SLE, and impairment of their removal by complement may explain the link between hereditary complement deficiency and the development of SLE.
Taylor, Philip R.; Carugati, Anna; Fadok, Valerie A.; Cook, H. Terence; Andrews, Mark; Carroll, Michael C.; Savill, John S.; Henson, Peter M.; Botto, Marina; Walport, Mark J.
The strongest susceptibility genes for the development of systemic lupus erythematosus (SLE) in humans are null mutants of classical pathway complement proteins. There is a hierarchy of disease susceptibility and severity according to the position of the missing protein in the activation pathway, with the severest disease associated with C1q deficiency. Here we demonstrate, using novel in vivo models of apoptotic cell clearance during sterile peritonitis, a similar hierarchical role for classical pathway complement proteins in vivo in the clearance of apoptotic cells by macrophages. Our results constitute the first demonstration of an impairment in the phagocytosis of apoptotic cells by macrophages in vivo in a mammalian system. Apoptotic cells are thought to be a major source of the autoantigens of SLE, and impairment of their removal by complement may explain the link between hereditary complement deficiency and the development of SLE. PMID:10934224
Taylor, P R; Carugati, A; Fadok, V A; Cook, H T; Andrews, M; Carroll, M C; Savill, J S; Henson, P M; Botto, M; Walport, M J
Complement plays a dual role in the progression of systemic lupus erythematosus since it has important protective functions, such as the clearance of immune complexes and apoptotic cells, but is also a mediator of renal inflammation. To investigate this balance in a clinically relevant setting, we investigated how targeted inhibition of all complement pathways vs. targeted inhibition of only the alternative pathway impacts immune and therapeutic outcomes in NZB/W F(1) mice. Following onset of proteinuria, mice were injected twice weekly with CR2-fH (inhibits alternative pathway), CR2-Crry (inhibits all pathways at C3 activation step), sCR2 (C3d targeting vehicle) or saline. Sera were analyzed every 2 weeks for anti-dsDNA antibody levels, and urinary albumin excretion was determined. Kidneys were collected for histological evaluation at 32 weeks. Compared to the control group, all CR2-fH, CR2-Crry and sCR2 treated groups showed significantly reduced serum anti-dsDNA antibody levels and strong trends towards reduced glomerular IgG deposition levels. Glomerular C3 deposition levels were also significantly reduced in all three-treated groups. However, significant reductions of disease activity (albuminuria and glomerulonephritis) were only seen in the CR2-fH treated group. These data highlight the dual role played by complement in the pathogenesis of lupus, and demonstrate a benefit of selectively inhibiting the alternative complement pathway, presumably because of protective contributions from the classical and/or lectin pathways. The sCR2 targeting moiety appears to be contributing to therapeutic outcome via modulation of autoimmunity. Furthermore, these results are largely consistent with our previous data using the MRL/lpr lupus model, thus broadening the significance of these findings. PMID:22000720
Sekine, Hideharu; Ruiz, Phillip; Gilkeson, Gary S; Tomlinson, Stephen
Activation of the alternate complement pathway in human serum by several bacterial components was compared. Peptidoglycan from group A streptococcal cell walls was the most active material, on a weight basis, followed by cell walls, protoplast membranes, and whole cells. The group-specific carbohydrate was inactive. Treatment of peptidoglycan with low concentrations of lysozyme or short periods of sonic treatment enhanced complement activation. High concentrations of lysozyme or extended sonic treatment of peptidoglycan destroyed or greatly reduced the capacity to activate complement. Lysozyme treatment of group A streptococcal cell walls or lipopolysaccharide had no measurable effect. Activation of the alternate complement pathway by group D streptococcal cell walls was destroyed by lysozyme. Activity of peptidoglycan was not inhibited by N-acetyl glucosamine, N-acetyl muramic acid, or D-alanine-D-alanine. Conversion of C3 and factored B by peptidoglycan was shown to occur by immunoelectrophoresis and crossed immunoelectrophoresis. Images
Greenblatt, J; Boackle, R J; Schwab, J H
This study investigated the capacity of neurons and astrocytes to spontaneously activate the complement system and control activation by expressing complement regulators. Human fetal neurons spontaneously activated complement through the classical pathway in normal and immunoglobulin-deficient serum and C1q binding was noted on neurons but not on astrocytes. A strong staining for C4, C3b, iC3b neoepitope and C9 neoepitope was also found on neurons. More than 40% of human fetal neurons were lysed when exposed to normal human serum in the presence of a CD59-blocking antibody, whereas astrocytes were unaffected. Significant reduction in neuronal cell lysis was observed after the addition of soluble complement receptor 1 at 10 ?g/ml. Fetal neurons were stained for CD59 and CD46 and were negative for CD55 and CD35. In contrast, fetal astrocytes were strongly stained for CD59, CD46, CD55, and were negative for CD35. This study demonstrates that human fetal neurons activate spontaneously the classical pathway of complement in an antibody-independent manner to assemble the cytolytic membrane attack complex on their membranes, whereas astrocytes are unaffected. One reason for the susceptibility of neurons to complement-mediated damage in vivo may reside in their poor capacity to control complement activation.
Singhrao, Sim K.; Neal, James W.; Rushmere, Neil K.; Morgan, B. Paul; Gasque, Philippe
Background Complement proteins and activation products have been found associated with neuropathology in Alzheimer's disease (AD). Recently, a C5a receptor antagonist was shown to suppress neuropathology in two murine models of AD, Tg2576 and 3xTg. Previously, a genetic deficiency of C1q in the Tg2576 mouse model showed an accumulation of fibrillar plaques similar to the complement sufficient Tg2576, but reactive glia were significantly decreased and neuronal integrity was improved suggesting detrimental consequences for complement activation in AD. The goal of this study was to define the role of the classical complement activation pathway in the progression of pathology in the 3xTg mouse that develops tangles in addition to fibrillar plaques (more closely reflecting human AD pathology) and to assess the influence of complement in a model of AD with a higher level of complement hemolytic activity. Methods 3xTg mice deficient in C1q (3xTgQ-/-) were generated, and both 3xTg and 3xTgQ-/- were backcrossed to the BUB mouse strain which has higher in vitro hemolytic complement activity. Mice were aged and perfused, and brain sections stained for pathological markers or analyzed for proinflammatory marker expression. Results 3xTgQ-/- mice showed similar amounts of fibrillar amyloid, reactive glia and hyperphosphorylated tau as the C1q-sufficient 3xTg at the ages analyzed. However, 3xTg and 3xTgQ-/- on the BUB background developed pathology earlier than on the original 3xTg background, although the presence of C1q had no effect on neuropathological and pro-inflammatory markers. In contrast to that seen in other transgenic models of AD, C1q, C4 and C3 immunoreactivity was undetectable on the plaques of 3xTg in any background, although C3 was associated with reactive astrocytes surrounding the plaques. Importantly, properdin a component of the alternative complement pathway was associated with plaques in all models. Conclusions In contrast to previously investigated transgenic models of AD, development of neuropathology in 3xTg mice, which progresses much slower than other murine models, may not be influenced by fibrillar amyloid mediated activation of the classical complement pathway, suggesting that the alternative complement pathway activation or a C3-independent cleavage of C5 could account for the detrimental effects in these mice that are prevented by the C5a receptor antagonist. Furthermore, the paucity of complement activation may be a factor in the slower kinetics of progression of pathology in the 3xTg model of this disease.
Background The neuronal microtubule-associated protein tau becomes hyperphosphorylated and forms aggregates in tauopathies but the processes leading to this pathological hallmark are not understood. Because tauopathies are accompanied by neuroinflammation and the complement cascade forms a key innate immune pathway, we asked whether the complement system has a role in the development of tau pathology. Findings We tested this hypothesis in two mouse models, which expressed either a central inhibitor of complement or lacked an inhibitor of the terminal complement pathway. Complement receptor-related gene/protein y is the natural inhibitor of the central complement component C3 in rodents. Expressing a soluble variant (sCrry) reduced the number of phospho-tau (AT8 epitope) positive neurons in the brain stem, cerebellum, cortex, and hippocampus of aged P301L mutant tau/sCrry double-transgenic mice compared with tau single-transgenic littermates (JNPL3 line). CD59a is the major inhibitor of formation of the membrane attack complex in mice. Intrahippocampal injection of adeno-associated virus encoding mutant human P301L tau into Cd59a?/? mice resulted in increased numbers of AT8-positive cells compared with wild-type controls. This was accompanied by neuronal and synaptic loss and reduced dendritic integrity. Conclusions Our data in two independent mouse models with genetic changes in key regulators of the complement system support the hypothesis that the terminal pathway has an active role in the development of tau pathology. We propose that inhibition of the terminal pathway may be beneficial in tauopathies.
We recently reported that the complement system plays a pivotal role in innate immune defense against Streptococcus pneumoniae during acute otitis media (OM) in mice. The current study was designed to determine which of the complement pathways are activated during acute pneumococcal OM and whether components of complement are expressed in the middle ear epithelium. Gene expression was determined by quantitative PCR, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining. We found that S. pneumoniae induced increased gene expression of factor B of the alternative complement pathway and C3 in mouse middle ear epithelium. Activation of factor B and C3 in the middle ear lavage fluids was significantly greater than in simultaneously obtained serum samples as determined by Western blotting. Using mice deficient in complement C1qa, factor B, and factor B/C2, we found that complement C3 activation and opsonophagocytosis of S. pneumoniae were greatly attenuated in factor B- and factor B/C2-deficient mice. These findings support the concept that local complement activation is an important host innate immune response and that activation of the alternative complement pathway represents one of the innate immune defense mechanisms against pneumococcal infection during the early stage of acute OM.
Li, Qian; Li, Yong Xing; Stahl, Gregory L.; Thurman, Joshua M.; He, Yujuan; Tong, Hua Hua
The membrane attack complex (MAC) of the complement system induces a necrotic-type cell death. Earlier findings suggested that Bcl-2 protects cells from MAC-induced necrosis. Here we examined the involvement of Bid, a proapoptotic protein, in MAC-induced cytotoxicity. Bid knockout (Bid-/-) mouse embryonic fibroblasts (MEF) and primary fibroblasts were damaged by complement but to a significantly lower extent than wild-type (WT) fibroblasts. Bid silencing with small interfering RNA duplexes led to elevated resistance of mouse fibroblasts, human K562, and Jurkat cells to lysis by complement. Bid-/- MEF were also resistant to toxic doses of streptolysin O, melittin, and A23187. Analysis of complement protein deposition on fibroblasts demonstrated that less complement C3 and C9 bound to Bid-/- than to WT cells, even though expression of the membrane complement inhibitors Crry and CD59 was relatively reduced on Bid-/- cells. Bid was rapidly cleaved in WT MEF subjected to lytic doses of MAC. Pretreatment of the cells with the pan-caspase inhibitor z-Val-Ala-Asp(OMe)-fluoromethylketone reduced Bid cleavage and cell lysis. These results indicate that complement MAC activates two cell death pathways, one involving caspases and Bid and one that is Bid-independent. PMID:19109183
Ziporen, Lea; Donin, Natalie; Shmushkovich, Taisia; Gross, Atan; Fishelson, Zvi
3MC syndrome has been proposed as a unifying term encompassing the overlapping Carnevale, Mingarelli, Malpuech and Michels syndromes. These rare autosomal recessive disorders exhibit a spectrum of developmental features, including characteristic facial dysmorphism, cleft lip and\\/or palate, craniosynostosis, learning disability and genital, limb and vesicorenal anomalies. Here we studied 11 families with 3MC syndrome and identified two mutated genes, COLEC11
Caroline Rooryck; Daniel P S Osborn; Elyes Chabchoub; Victor Hernandez-Hernandez; Hanan Shamseldin; Joanna Kenny; Aoife Waters; Dagan Jenkins; Ali Al Kaissi; Gabriela F Leal; Bruno Dallapiccola; Franco Carnevale; Maria Bitner-Glindzicz; Melissa Lees; Raoul Hennekam; Philip Stanier; Alan J Burns; Hilde Peeters; Fowzan S Alkuraya; Philip L Beales
Activation of C3 and factor B in normal human serum by P. ovale was demonstrated using a standard unidirectional immunoelectrophoresis technique. Activation of complement by the alternative (properdin) pathway is a possible mechanism by which P. ovale may mediate an inflammatory response.
Patricia W. Belew; E. W. Rosenberg; B. R. Jennings
To investigate the role of complement protein factor B (Bf) and alternative pathway activity in vivo, and to test the hypothesized potential genetic lethal effect of Bf deficiency, the murine Bf gene was interrupted by exchange of exon 3 through exon 7 (including the factor D cleaving site) with the neor gene. Mice heterozygous for the targeted Bf allele were
Mitsuru Matsumoto; Wataru Fukuda; Antonella Circolo; Joseph Goellner; Jena Strauss-Schoenberger; Xuefeng Wang; Shigeru Fujita; Tunde Hidvegi; David D. Chaplin; Harvey R. Colten
Recent studies have revealed profound developmental consequences of mutations in genes encoding proteins of the lectin pathway of complement activation, a central component of the innate immune system. Apart from impairment of immunity against microorganisms, it is known that hereditary deficiencies of this system predispose one to autoimmune conditions. Polymorphisms in complement genes are linked to, for example, atypical hemolytic uremia and age-dependent macular degeneration. The complement system comprises three convergent pathways of activation: the classical, the alternative, and the lectin pathway. The recently discovered lectin pathway is less studied, but polymorphisms in the plasma pattern-recognition molecule mannan-binding lectin (MBL) are known to impact its level, and polymorphisms in the MBL-associated serine protease-2 (MASP-2) result in defects of complement activation. Recent studies have described roles outside complement and immunity of another MBL-associated serine protease, MASP-3, in the etiology of 3MC syndrome, an autosomal-recessive disorder involving a spectrum of developmental features, including characteristic facial dysmorphism. Syndrome-causing mutations were identified in MASP1, encoding MASP-3 and two additional proteins, MASP-1 and MAp44. Furthermore, an association was discovered between 3MC syndrome and mutations in COLEC11, encoding CL-K1, another molecule of the lectin pathway. The findings were confirmed in zebrafish, indicating that MASP-3 and CL-K1 underlie an evolutionarily conserved pathway of embryonic development. Along with the discovery of a role of C1q in pruning synapses in mice, these recent advances point toward a broader role of complement in development. Here, we compare the functional immunologic consequences of “conventional” complement deficiencies with these newly described developmental roles.
Degn, S?ren E.; Jensenius, Jens C.; Thiel, Steffen
The dimorphic fungus Paracoccidioides brasiliensis is the etiological agent of paracoccidioidomycosis, a human granulomatous disease. Recently the first case of natural disease in dogs was reported. The complement system is an important effector component of humoral immunity against infectious agents. Therefore, the aim of this study was to evaluate the activation of the dog alternative complement pathway by P. brasiliensis. Initially, the ability of erythrocytes of guinea pig, rabbit, sheep, chicken and swine to activate the dog alternative pathway was evaluated. The guinea pig erythrocytes showed the greatest capacity to activate dog alternative pathway. The alternative (AH50) hemolytic activity was evaluated in 27 serum samples from healthy dogs and the mean values were 87.2 AH50/ml. No significant differences were observed in relation to sex and age. The alternative pathway activation by P. brasiliensis was higher in serum samples from adult dogs when compared to puppies and aged dogs (p ? 0.05). This is the first report of dog alternative complement pathway activation by P. brasiliensis and suggests that it may play a protective role in canine paracoccidioidomycosis.
Bianchini, A.A.C.; Petroni, T.F.; Fedatto, P.F.; Bianchini, R.R.; Venancio, E.J.; Itano, E.N.; Ono, M.A.
UV wavebands in sunlight are immunomodulatory. About half the amount of UVA within a minimum erythemal dose of sunlight is systemically immunosuppressive, whereas higher doses protect from UVB immunosuppression in mice. We have earlier shown that these responses to UVA are genetically restricted, as they occur in C57BL/6 but not in Balb/c mice. We used gene set enrichment analysis of microarray data and real-time reverse transcriptase (RT)-PCR confirmation to determine the molecular mechanisms associated with UVA immunomodulation. We found upregulation of mRNA for the alternative complement pathway. The core-enriched genes complement component 3, properdin, and complement factor B were all activated by the immunosuppressive dose of UVA only in UVA-responsive C57BL/6 but not in unresponsive BALB/c mice. This therefore matched the genetic restriction and dose responsiveness of UVA immunosuppression. The immune-protective higher UVA dose prevented UVB from downregulating chemokine receptor 7 and IL-12B, and decreased IL-10, supporting the earlier identification of IL-12 and IL-10 in high-dose UVA protection from UVB immunosuppression. Our study has identified activation of the alternative complement pathway as a trigger of UVA-induced systemic immunosuppression and suggests that this pathway is likely to be an important sensor of UVA-induced damage to the skin. PMID:19516263
Stapelberg, Michael P F; Williams, Rohan B H; Byrne, Scott N; Halliday, Gary M
BACKGROUND The Mannose 6-phosphate Receptor Homology (MRH) domain-containing family of proteins, which include recycling receptors (mannose 6-phosphate receptor, MPRs), resident endoplasmic reticulum (ER) proteins (glucosidase II ?-subunit, XTP3-B, OS-9), and a Golgi glycosyltransferase (GlcNAc-phosphotransferase ?-subunit), are characterized by the presence of one or more MRH domains. Many MRH domains act as lectins and bind specific phosphorylated (MPRs) or non-phosphorylated (glucosidase II ?-subunit, XTP3-B and OS-9) high mannose-type N-glycans. The MPRs are the only proteins known to bind mannose 6-phosphate (Man-6-P) residues via their MRH domains. SCOPE OF REVIEW Recent biochemical and structural studies that have provided valuable insight into the glycan specificity and mechanisms of carbohydrate recognition by this diverse group of MRH domain-containing proteins are highlighted. MAJOR CONCLUSIONS Currently, three-dimensional structures are known for ten MRH domains, revealing the conservation of a similar fold. OS-9 and the MPRs use the same four residues (Gln, Arg, Glu, and Tyr) to bind mannose. GENERAL SIGNIFICANCE The MRH domain-containing proteins play key roles in the secretory pathway: glucosidase II, XTP3-B, and OS-9 are involved in the recognition of nascent glycoproteins, whereas the MPRs play an essential role in lysosome biogenesis by targeting Man-6-P-containing lysosomal enzymes to the lysosome.
Castonguay, Alicia C.; Olson, Linda J.; Dahms, Nancy M.
Membranous nephropathy (MN) describes a histopathologic pattern of injury marked by glomerular subepithelial immune deposits and collectively represents one of the most common causes of adult nephrotic syndrome. Studies in Heymann nephritis, an experimental model of MN, have established a paradigm in which these deposits locally activate complement to cause podocyte injury, culminating in cytoskeletal reorganization, loss of slit diaphragms, and proteinuria. There is much circumstantial evidence for a prominent role of complement in human MN because C3 and C5b-9 are found consistently within immune deposits. Secondary MN often shows the additional presence of C1q, implicating the classic pathway of complement activation. Primary MN, however, is IgG4-predominant and IgG4 is considered incapable of binding C1q and activating the complement pathway. Recent studies have identified the M-type phospholipase A2 receptor (PLA2R) as the major target antigen in primary MN. Early evidence hints that IgG4 anti-PLA2R autoantibodies can bind mannan-binding lectin and activate the lectin complement pathway. The identification of anti-PLA2R antibodies as likely participants in the pathogenesis of disease will allow focused investigation into the role of complement in MN. Definitive therapy for MN is immunosuppression, although future therapeutic agents that specifically target complement activation may represent an effective temporizing measure to forestall further glomerular injury. PMID:24161038
Ma, Hong; Sandor, Dana G; Beck, Laurence H
Continuous-filament glass fibers coated with organic agents, candidate asbestos substitutes, were assessed for their ability to elicit from normal human serum complement-derived cleavage products which are able to stimulate the chemotaxis and the respiratory burst of polymorphonuclear leukocytes. Glass fibers generated chemoattracting and respiratory stimulating factors for polymorphonuclears from human serum. The effect was dose related for chemotaxis from the serum fiber concentration of 75 micrograms/ml to 1,250 micrograms/ml. The serum chemoattracting activity, as well the respiratory stimulation, were dramatically impaired when serum had been preliminarily absorbed with antiC5 antiserum. Since the impairment of chemotactic activity occurred also in the presence of EDTA, but not in the presence of EGTA, we assumed an activation of the alternative complement pathway. Glass fibers were studied in comparison to a UICC sample of Canadian chrysotile asbestos, which is able to activate in vitro the alternative complement pathway. Glass fibers exhibited less ability than asbestos fibers to generate complement cleavage products with chemotactic activity for polymorphonuclears; however, they produced an activity about equal to 80% of a chemotactic standard stimulus such as zymosan-activated plasma. PMID:2852993
Governa, M; Valentino, M; Visona, I; Marchiseppe, I; Lo Martire, N
By virtue of its amplifying property, the alternative complement pathway has been implicated in a number of inflammatory diseases and constitutes an attractive therapeutic target. An anti-factor D Fab fragment (AFD) was generated to inhibit the alternative complement pathway in advanced dry age-related macular degeneration. AFD potently prevented factor D (FD)-mediated proteolytic activation of its macromolecular substrate C3bB, but not proteolysis of a small synthetic substrate, indicating that AFD did not block access of the substrate to the catalytic site. The crystal structures of AFD in complex with human and cynomolgus FD (at 2.4 and 2.3 ?, respectively) revealed the molecular details of the inhibitory mechanism. The structures show that the AFD-binding site includes surface loops of FD that form part of the FD exosite. Thus, AFD inhibits FD proteolytic function by interfering with macromolecular substrate access rather than by inhibiting FD catalysis, providing the molecular basis of AFD-mediated inhibition of a rate-limiting step in the alternative complement pathway.
Katschke, Kenneth J.; Wu, Ping; Ganesan, Rajkumar; Kelley, Robert F.; Mathieu, Mary A.; Hass, Philip E.; Murray, Jeremy; Kirchhofer, Daniel; Wiesmann, Christian; van Lookeren Campagne, Menno
Post-infectious glomerulonephritis is a common disorder that develops following an infection. In the majority of cases, there is complete recovery of renal function within a few days to weeks following resolution of the infection. In a small percentage of patients, however, the glomerulonephritis takes longer to resolve resulting in persistent hematuria and proteinuria, or even progression to end-stage kidney disease. In some cases of persistent hematuria and proteinuria, kidney biopsies show findings of a post-infectious glomerulonephritis even in the absence of any evidence of a preceding infection. The cause of such ‘atypical’ post-infectious glomerulonephritis, with or without evidence of preceding infection, is unknown. Here, we show that most patients diagnosed with this ‘atypical’ post-infectious glomerulonephritis have an underlying defect in the regulation of the alternative pathway of complement. These defects include mutations in complement regulating proteins and antibodies to the C3 convertase known as C3 nephritic factors. As a result, the activated alternative pathway is not brought under control even after resolution of the infection. Hence, the sequela is continual glomerular deposition of complement factors with resultant inflammation and development of an ‘atypical’ post-infectious glomerulonephritis.
Sethi, Sanjeev; Fervenza, Fernando C.; Zhang, Yuzhou; Zand, Ladan; Meyer, Nicole C.; Borsa, Nicolo; Nasr, Samih H.; Smith, Richard J.H.
Allergy is a complex disease that is likely to involve dysregulated CD4+ T cell activation. Here we propose a novel methodology to gain insight into how coordinated behaviour emerges between disease-dysregulated pathways in response to pathophysiological stimuli. Using peripheral blood mononuclear cells of allergic rhinitis patients and controls cultured with and without pollen allergens, we integrate CD4+ T cell gene expression from microarray data and genetic markers of allergic sensitisation from GWAS data at the pathway level using enrichment analysis; implicating the complement system in both cellular and systemic response to pollen allergens. We delineate a novel disease network linking T cell activation to the complement system that is significantly enriched for genes exhibiting correlated gene expression and protein-protein interactions, suggesting a tight biological coordination that is dysregulated in the disease state in response to pollen allergen but not to diluent. This novel disease network has high predictive power for the gene and protein expression of the Th2 cytokine profile (IL-4, IL-5, IL-10, IL-13) and of the Th2 master regulator (GATA3), suggesting its involvement in the early stages of CD4+ T cell differentiation. Dissection of the complement system gene expression identifies 7 genes specifically associated with atopic response to pollen, including C1QR1, CFD, CFP, ITGB2, ITGAX and confirms the role of C3AR1 and C5AR1. Two of these genes (ITGB2 and C3AR1) are also implicated in the network linking complement system to T cell activation, which comprises 6 differentially expressed genes. C3AR1 is also significantly associated with allergic sensitisation in GWAS data.
Couto Alves, Alexessander; Bruhn, Soren; Ramasamy, Adaikalavan; Wang, Hui; Holloway, John W.; Hartikainen, Anna-Liisa; Jarvelin, Marjo-Riitta; Benson, Mikael; Balding, David J.; Coin, Lachlan J. M.
Allergy is a complex disease that is likely to involve dysregulated CD4+ T cell activation. Here we propose a novel methodology to gain insight into how coordinated behaviour emerges between disease-dysregulated pathways in response to pathophysiological stimuli. Using peripheral blood mononuclear cells of allergic rhinitis patients and controls cultured with and without pollen allergens, we integrate CD4+ T cell gene expression from microarray data and genetic markers of allergic sensitisation from GWAS data at the pathway level using enrichment analysis; implicating the complement system in both cellular and systemic response to pollen allergens. We delineate a novel disease network linking T cell activation to the complement system that is significantly enriched for genes exhibiting correlated gene expression and protein-protein interactions, suggesting a tight biological coordination that is dysregulated in the disease state in response to pollen allergen but not to diluent. This novel disease network has high predictive power for the gene and protein expression of the Th2 cytokine profile (IL-4, IL-5, IL-10, IL-13) and of the Th2 master regulator (GATA3), suggesting its involvement in the early stages of CD4+ T cell differentiation. Dissection of the complement system gene expression identifies 7 genes specifically associated with atopic response to pollen, including C1QR1, CFD, CFP, ITGB2, ITGAX and confirms the role of C3AR1 and C5AR1. Two of these genes (ITGB2 and C3AR1) are also implicated in the network linking complement system to T cell activation, which comprises 6 differentially expressed genes. C3AR1 is also significantly associated with allergic sensitisation in GWAS data. PMID:24116013
Couto Alves, Alexessander; Bruhn, Sören; Ramasamy, Adaikalavan; Wang, Hui; Holloway, John W; Hartikainen, Anna-Liisa; Jarvelin, Marjo-Riitta; Benson, Mikael; Balding, David J; Coin, Lachlan J M
A fragment of activated Hageman factor (HFf) has been demonstrated to activate the classical pathway of complement in a manner that is analogous to complement activation by antigen-antibody complexes or aggregated IgG. Thus C1, C4, C2, C3, and C5 were found to be depleted on addition of HFf to serum. The reduction of serum hemolytic activity was maximal upon addition of 5 micrograms HFf and an incubation time of 60 min at 37 degrees C. Consumption of the total complement activity and of the individual components proceeded in a dose-dependent fashion. No comparable activity was observed when equimolar concentrations of either the native Hageman factor (HF) or two-chain activated form of Hageman factor (HFa) were incubated with serum. Further, the ability of HFf to convert serum C3 and C4 was similar to that of aggregated IgG as assessed by immunoelectrophoresis. This function of HFf appeared to be independent of plasminogen (or plasmin) since plasminogen-free serum was indistinguishable from normal serum. Radial double immunodiffusion experiments using antiserum to C1q, C1r, and C1s on HFf-treated serum demonstrated the dissociation of the C1 trimolecular complex, with concomitant reduction of C1r antigenicity that is indicative of C1 activation. Thus, HFf appears to lead to C1 activation upon incubation with serum or when incubated with partially purified C1. This may represent a control link between activation of the intrinsic coagulation-kinin pathway and the initiation of the classical complement cascade.
Septic shock is a critical clinical condition with a high mortality rate. A better understanding of the underlying mechanisms is important to develop effective therapies. Basic and clinical studies suggest that activation of complements in the common cascade, for example, complement component 3 (C3) and C5, is involved in the development of septic shock. The involvement of three upstream complement pathways in septic shock is more complicated. Both the classical and alternative pathways appear to be activated in septic shock, but the alternative pathway may be activated earlier than the classical pathway. Activation of these two pathways is essential to clear endotoxin. Recent investigations have shed light on the role of lectin complement pathway in septic shock. Published reports suggest a protective role of mannose-binding lectin (MBL) against sepsis. Our preliminary study of MBL-associated serine protease-2 (MASP-2) in septic shock patients indicated that acute decrease of MASP-2 in the early phase of septic shock might correlate with in-hospital mortality. It is unknown whether excessive activation of these three upstream complement pathways may contribute to the detrimental effects in septic shock. This paper also discusses additional complement-related pathogenic mechanisms and intervention strategies for septic shock.
Charchaflieh, Jean; Wei, Jiandong; Labaze, Georges; Hou, Yunfang Joan; Babarsh, Benjamin; Stutz, Helen; Lee, Haekyung; Worah, Samrat; Zhang, Ming
Factor H, a regulatory protein of the alternative pathway of complement (APC), is present in amyloid-beta (Abeta) plaques in Alzheimer's disease (AD). Abeta plaques also contain significant amounts of heparan sulfate proteoglycans (HSPGs), such as agrin, as well as numerous activated microglia expressing increased levels complement receptor 3 (CR3). Here, we show the colocalization of each of these molecules in the AD brain and the functional capacity for these molecules to bind to one another in vitro. We propose that CR3 receptors expressed by microglia are used for ligand binding to factor H bound to HSPGs and Abeta in plaques in the AD brain. PMID:12458045
Strohmeyer, Ron; Ramirez, Mauricio; Cole, Gregory J; Mueller, Kyle; Rogers, Joseph
Dengue disease is a mosquito-borne infection caused by Dengue virus. Infection may be asymptomatic or variably manifest as mild Dengue fever (DF) to the most severe form, Dengue haemorrhagic fever (DHF). Mechanisms that influence disease severity are not understood. Complement, an integral component of the immune system, is activated during Dengue infection and the degree of activation increases with disease severity. Activation of the complement alternative pathway is influenced by polymorphisms within activation (factor B rs12614/rs641153, C3 rs2230199) and regulatory [complement factor H (CFH) rs800292] proteins, collectively termed a complotype. Here, we tested the hypothesis that the complotype influences disease severity during secondary Dengue infection. In addition to the complotype, we also assessed two other disease-associated CFH polymorphisms (rs1061170, rs3753394) and a structural polymorphism within the CFH protein family. We did not detect any significant association between the examined polymorphisms and Dengue infection severity in the Thai population. However, the minor allele frequencies of the factor B and C3 polymorphisms were less than 10%, so our study was not sufficiently powered to detect an association at these loci. We were also unable to detect a direct interaction between CFH and Dengue NS1 using both recombinant NS1 and DV2-infected culture supernatants. We conclude that the complotype does not influence secondary Dengue infection severity in the Thai population. PMID:23919682
Kraivong, R; Vasanawathana, S; Limpitikul, W; Malasit, P; Tangthawornchaikul, N; Botto, M; Screaton, G R; Mongkolsapaya, J; Pickering, M C
The severity of ischaemic heart disease is markedly enhanced in type 2 diabetes. We recently reported that complement activation exacerbates I/R injury in the type 2 diabetic heart. The purpose of this study was to isolate and examine MBL pathway activation following I/R injury in the diabetic heart. ZLC and ZDF rats underwent 30 minutes of left coronary artery occlusion followed by 120 minutes of reperfusion. Two different groups of ZDF rats were treated with either FUT-175, a broad complement inhibitor, or P2D5, a monoclonal antibody raised against rat MBL-A. ZDF rats treated with FUT175 and P2D5 had significantly decreased myocardial infarct size, C3 deposition and neutrophil accumulation compared with untreated ZDF controls. Taken together, these findings indicate that the MBL pathway plays a key role in the severity of complement-mediated I/R injury in the type 2 diabetic heart.
La Bonte, Laura R.; Dokken, Betsy; Davis-Gorman, Grace; Stahl, Gregory L.; McDonagh, Paul F.
The mannose-binding lectin (MBL), a circulating pattern recognition molecule, recognizes a wide range of infectious agents with resultant initiation of the complement cascade in an Ab-independent manner. MBL recognizes infectious non-self and altered self in the guise of apoptotic and necrotic cells. In this study, we demonstrate that mice lacking MBL, and hence are devoid of MBL-dependent lectin pathway activation
Mary C. Walsh; Todd Bourcier; Kazue Takahashi; Lei Shi; Marc N. Busche; Russell P. Rother; Scott D. Solomon; R. Alan; B. Ezekowitz; Gregory L. Stahl
Mannose-binding lectin (MBL) is a key molecule of innate immunity. Binding of MBL to carbohydrates present on pathogens activates the lectin pathway of complement activation, resulting into opsonization and anti-microbial protection. Three frequently occurring single nucleotide polymorphisms (SNPs) are described in the coding region of the MBL2 gene that are associated with abnormal polymerization of the MBL molecule, decreased serum
Anja Roos; Patrick Dieltjes; Rolf H. A. M. Vossen; Mohamed R. Daha; Peter de Knijff
Purpose. Retinal pigment epithelial (RPE) cell death occurs early in the pathogenesis of age-related macular degeneration (AMD) and Stargardt's disease. Emerging evidence suggests that all-trans-retinal (atRal) and alternative complement pathway (AP) activation contribute to RPE cell death in both of these retinal disorders. The aim of this study was to investigate the combined effect of atRal and AP activation on RPE cell viability. Methods. RPE cells were treated with atRal and then incubated with a complement-fixing antibody followed by stimulation with C1q-depleted serum to activate AP. Cell viability was assessed by tetrazolium salt and lactate dehydrogenase release assays. Changes in cell surface CD46 and CD59 expression were assessed by flow cytometry. Cells were pretreated with the antioxidant resveratrol, and C1q-depleted serum was incubated with an anti-C5 antibody prior to initiating AP attack to determine the protective effects of antioxidant therapy and complement inhibition, respectively. Results. Both atRal and AP activation independently caused RPE cell death. When AP attack was initiated following atRal treatment, a synergistic increase in cell death was observed. Following 24-hour atRal treatment, CD46 and CD59 expression decreased, corresponding temporally to increased susceptibility to AP attack. Resveratrol and the anti-C5 antibody both protected against AP-induced cell death following atRal exposure and were most effective when used in combination. Conclusions. atRal sensitizes RPE cells to AP attack, which may be mediated in part by atRal-induced downregulation of CD46 and CD59. Despite increased susceptibility to AP attack following exposure to atRal, resveratrol and anti-C5 antibody effectively prevent AP-mediated cell death.
Berchuck, Jacob E.; Yang, Ping; Toimil, Brett A.; Ma, Zhe; Baciu, Peter; Jaffe, Glenn J.
The twin-arginine translocation (Tat) pathway is well known for its ability to export fully folded substrate proteins out of the cytoplasm of gram-negative and gram-positive bacteria. Studies of this mechanism in Escherichia coli have identified numerous transient protein-protein interactions that guide export-competent proteins through the Tat pathway. To visualize these interactions, we have adapted bimolecular fluorescence complementation (BiFC) to detect protein-protein interactions along the Tat pathway of living cells. Fragments of the yellow fluorescent protein (YFP) were fused to soluble and transmembrane factors that participate in the translocation process including Tat substrates, Tat-specific proofreading chaperones and the integral membrane proteins TatABC that form the translocase. Fluorescence analysis of these YFP chimeras revealed a wide range of interactions such as the one between the Tat substrate dimethyl sulfoxide reductase (DmsA) and its dedicated proofreading chaperone DmsD. In addition, BiFC analysis illuminated homo- and hetero-oligomeric complexes of the TatA, TatB and TatC integral membrane proteins that were consistent with the current model of translocase assembly. In the case of TatBC assemblies, we provide the first evidence that these complexes are co-localized at the cell poles. Finally, we used this BiFC approach to capture interactions between the putative Tat receptor complex formed by TatBC and the DmsA substrate or its dedicated chaperone DmsD. Our results demonstrate that BiFC is a powerful approach for studying cytoplasmic and inner membrane interactions underlying bacterial secretory pathways. PMID:20169075
Kostecki, Jan S; Li, Haiming; Turner, Raymond J; DeLisa, Matthew P
The twin-arginine translocation (Tat) pathway is well known for its ability to export fully folded substrate proteins out of the cytoplasm of Gram-negative and Gram-positive bacteria. Studies of this mechanism in Escherichia coli have identified numerous transient protein-protein interactions that guide export-competent proteins through the Tat pathway. To visualize these interactions, we have adapted bimolecular fluorescence complementation (BiFC) to detect protein-protein interactions along the Tat pathway of living cells. Fragments of the yellow fluorescent protein (YFP) were fused to soluble and transmembrane factors that participate in the translocation process including Tat substrates, Tat-specific proofreading chaperones and the integral membrane proteins TatABC that form the translocase. Fluorescence analysis of these YFP chimeras revealed a wide range of interactions such as the one between the Tat substrate dimethyl sulfoxide reductase (DmsA) and its dedicated proofreading chaperone DmsD. In addition, BiFC analysis illuminated homo- and hetero-oligomeric complexes of the TatA, TatB and TatC integral membrane proteins that were consistent with the current model of translocase assembly. In the case of TatBC assemblies, we provide the first evidence that these complexes are co-localized at the cell poles. Finally, we used this BiFC approach to capture interactions between the putative Tat receptor complex formed by TatBC and the DmsA substrate or its dedicated chaperone DmsD. Our results demonstrate that BiFC is a powerful approach for studying cytoplasmic and inner membrane interactions underlying bacterial secretory pathways.
Kostecki, Jan S.; Li, Haiming; Turner, Raymond J.; DeLisa, Matthew P.
To investigate the effect of carbohydrate on activation of the alternative pathway of complement by IgA immune complexes, aglycosylated monoclonal IgA was made biosynthetically in the presence of tunicamycin. When immune complexes were incubated with normal human serum (NHS), the aglycosylated IgA immune complexes caused less depletion of the alternative pathway activity of the serum. They also bound less C3 and produced less terminal complement complexes. The binding of C3 to both immune complexes was mainly through hydroxylamine sensitive ester bonds. C3 did not bind to free IgA. Images Figure 1 Figure 5 Figure 6
Zhang, W; Lachmann, P J
To selectively modulate human complement alternative pathway (CAP) activity implicated in a wide range of acute and chronic inflammatory conditions and to provide local cell surface and tissue-based inhibition of complement-induced damage, we developed TT30, a novel therapeutic fusion protein linking the human complement receptor type 2 (CR2/CD21) C3 fragment (C3frag = iC3b, C3dg, C3d)-binding domain with the CAP inhibitory domain of human factor H (fH). TT30 efficiently blocks ex vivo CAP-dependent C3frag accumulation on activated surfaces, membrane attack complex (MAC) formation and hemolysis of RBCs in a CR2-dependent manner, and with a ? 150-fold potency gain over fH, without interference of C3 activation or MAC formation through the classic and lectin pathways. TT30 protects RBCs from hemolysis and remains bound and detectable for at least 24 hours. TT30 selectively inhibits CAP in cynomolgus monkeys and is bioavailable after subcutaneous injection. Using a unique combination of targeting and effector domains, TT30 controls cell surface CAP activation and has substantial potential utility for the treatment of human CAP-mediated diseases.
Storek, Michael; Mazsaroff, Istvan; Risitano, Antonio M.; Lundberg, Ante S.; Horvath, Christopher J.; Holers, V. Michael
The mechanism by which a fragment of activated Hageman factor (HFf) activates the classical pathway of complement in serum or platelet-poor plasma has been further delineated. When serum or platelet-poor plasma was incubated with various concentrations of HFf, the total complement hemolytic activity was reduced in a dose-dependent manner. This activation appears to be due to the direct interaction of HFf with macromolecular C1, since incubation of purified C1 with HFf resulted in dissociation of the subunits with concomitant reduction of C1r antigenicity that is indicative of C1 activation. HFf-dependent activation was prevented by prior treatment of HFf with the active site-directed inhibitor, H-D-proline-phenylalanine-arginine chloromethyl ketone or with a specific inhibitor of activated HF derived from corn. Incubation of HFf with highly purified C1r also resulted in activation of C1r as assessed directly using a synthetic substrate or indirectly by activation of C1s and consumption of C2. However, incubation of HFf with highly purified C1s resulted in formation of activated C1s (C1s-) but this was less efficient than HFf activation of C1r. We therefore conclude that activation of C1 in macromolecular C1 is the result of HFf conversion of C1r to C1r; activation of C1s then occurs primarily by C-1r and to a lesser degree by the direct action of HFf. Images
Ghebrehiwet, B; Randazzo, B P; Dunn, J T; Silverberg, M; Kaplan, A P
Studies in gene-targeted mice have demonstrated that factor B of the alternative complement pathway plays an important role in several disease models, but an exogenous inhibitor of factor B has not previously been available. We have developed an inhibitory monoclonal antibody directed against a critical epitope on mouse factor B and have tested it in a model of antiphospholipid (aPL)
Joshua M. Thurman; Damian M. Kraus; Guillermina Girardi; Dennis Hourcade; Hee J. Kang; Pamela A. Royer; Lynne M. Mitchell; Patricia C. Giclas; Jane Salmon; Gary Gilkeson; V. Michael Holers
Serum resistance in Haemophilus parasuis strain SC096 has been shown to be dependent on expression of the outer membrane protein P2 (OmpP2) and loss of the ompP2 gene results in significantly greater sensitivity to both porcine and rabbit sera. However, the mechanism of complement activation by the serum sensitive ?ompP2 strain is unknown. In this study, the classical complement pathway is demonstrated to be the main pathway for killing the H. parasuis ?ompP2 strain, and not the mannan-binding lectin (MBL) or alternative pathway. In addition, absorption of antibodies against ?ompP2 strain or depletion of IgGs from serum inhibited serum killing activity, which could be restored by addition of heat-inactivated serum or purified IgGs. Western blot analysis indicated that the OmpP2 mutant could bind significantly more IgGs than the wild type strain SC096 when incubated with serum. Finally, IgGs in normal rabbit serum targeted to the OMPs, but not lipooligosaccharide (LOS) in the OmpP2 mutant strain were found to be involved in bacterial killing indicating that the bactericidal epitope(s) is in the outer membrane proteins. PMID:23103218
Zhou, S M; Xu, C G; Zhang, B; Feng, S X; Zhang, L Y; Zou, Y; Liao, M
Background The complement system is vital for innate immunity and is implicated in the pathogenesis of inflammatory diseases and the mechanism of host defense. Complement deficiencies occasionally cause life-threatening diseases. In hemodialysis (HD) patients, profiles on complement functional activity and deficiency are still obscure. The objectives of the present study were to measure the functional complement activities of the classical pathway (CP), lectin pathway (LP) and alternative pathway (AP) using a novel method and consequently to elucidate the rates of deficiencies among HD patients. Methods In the present study, 244 HD patients at one dialysis center and 204 healthy controls were enrolled. Functional complement activities were measured simultaneously using the Wielisa®-kit. The combination of the results of these three pathway activities allows us to speculate which candidate complement is deficient; subsequently, the deficient complement was determined. Results All three functional complement activities were significantly higher in the HD patients than in the control group (P < 0.01 for all cases). After identifying candidates in both groups with complement deficiencies using the Wielisa®-kit, 16 sera (8.8%) with mannose-binding lectin (MBL) deficiency, 1 serum (0.4%) with C4 deficiency, 1 serum (0.4%) with C9 deficiency, and 1 serum (0.4%) with B deficiency were observed in the HD group, and 18 sera (8.8%) with MBL deficiency and 1 serum (0.5%) with B deficiency were observed in the control group. There were no significant differences in the 5-year mortality rate between each complement-deficient group and the complement-sufficient group among the HD patients. Conclusion This is the first report that profiles complement deficiencies by simultaneous measurement of functional activities of the three complement pathways in HD patients. Hemodialysis patients frequently suffer from infections or malignancies, but functional complement deficiencies do not confer additional risk of mortality.
AKI accelerates cystogenesis. Because cystogenic mutations induce strong transcriptional responses similar to those seen after AKI, these responses may accelerate the progression of cystic renal disease. Here, we modulated the severity of the AKI-like response in Cys1cpk/cpk mice, a model that mimics autosomal recessive polycystic kidney disease. Specifically, we induced or inhibited activity of the renoprotective enzyme heme oxygenase (HO) and determined the effects on renal cystogenesis. We found that induction of HO attenuated both renal injury and the rate of cystogenesis, whereas inhibition of HO promoted cystogenesis. HO activity mediated the response of NF?B, which is a hallmark transcriptional feature common to both cystogenesis and AKI. Among the HO-modulated effects we measured, expression of complement component 3 (C3) strongly correlated with cystogenesis, a functionally relevant association as suggested by Cys1cpk/cpk mice with genetically induced C3 deficiency. Because both C3 deficiency and HO induction reduce cyst number and cyst areas, these two factors define an injury-stimulated cystogenic pathway that may provide therapeutic targets to slow the formation of new renal cysts and the growth of existing cysts.
Zhou, Juling; Ouyang, Xiaosen; Schoeb, Trenton R.; Bolisetty, Subhashini; Cui, Xiangqin; Mrug, Sylvie; Yoder, Bradley K.; Johnson, Martin R.; Szalai, Alexander J.
Deoxygenation of erythrocytes from sickle cell anemia (SCA) patients alters membrane phospholipid distribution with increased exposure of phosphatidylethanolamine (PE) and phosphatidylserine (PS) on the outer leaflet. This study investigated whether altered membrane phospholipid exposure on sickle erythrocytes results in complement activation. In vitro deoxygenation of sickle but not normal erythrocytes resulted in complement activation measured by C3 binding. Additional evidence indicated that this activation was the result of the alterations in membrane phospholipids. First, complement was activated by normal erythrocytes after incubation with sodium tetrathionate, which produces similar phospholipid changes. Second, antibody was not required for complement activation by sickle or tetrathionate-treated erythrocytes. Third, the membrane regulatory proteins, decay-accelerating factor (CD55) and the C3b/C4b receptor (CD35), were normal on sickle and tetrathionate-treated erythrocytes. Finally, insertion of PE or PS into normal erythrocytes induced alternative pathway activation. SCA patients in crisis exhibited increased plasma factor Bb levels compared with baseline, and erythrocytes isolated from hospitalized SCA patients had increased levels of bound C3, indicating that alternative pathway activation occurs in vivo. Activation of complement may be a contributing factor in sickle crisis episodes, shortening the life span of erythrocytes and decreasing host defense against infections. Images
Wang, R H; Phillips, G; Medof, M E; Mold, C
Candida albicans activates the classical and alternative complement pathways, leading to deposition of opsonic complement fragments on the cell surface. Our previous studies found that antimannan immunoglob- ulin G (IgG) in normal human serum (NHS) allows C. albicans to initiate the classical pathway. The purpose of this study was to determine whether antimannan IgG also plays a role in initiation
MASON X. ZHANG; THOMAS R. KOZEL
ABSTRACT Fungal cell walls are predominantly composed of glucans, mannans, and chitin. Recognition of these glycans by the innate immune system is a critical component of host defenses against the mycoses. Complement, an important arm of innate immunity, plays a significant role in fungal pathogenesis, especially the alternative pathway (AP). Here we determine that the glycan monosaccharide composition and glycosidic linkages affect AP activation and C3 deposition. Furthermore, properdin, a positive regulator of the AP, contributes to these functions. AP activation by glycan particles that varied in composition and linkage was measured by C3a generation in serum treated with 10 mM EGTA and 10 mM Mg2+ (Mg-EGTA-treated serum) (AP specific; properdin functional) or Mg-EGTA-treated serum that lacked functional properdin. Particles that contained either ?1?3 or ?1?6 glucans or both generated large and similar amounts of C3a when the AP was intact. Blocking properdin function resulted in 5- to 10-fold-less C3a production by particulate ?1?3 glucans. However, particulate ?1?6 glucans generated C3a via the AP only in the presence of intact properdin. Interestingly, zymosan and glucan-mannan particles (GMP), which contain both ?-glucans and mannans, also required properdin to generate C3a. The ?1?4 glycans chitin and chitosan minimally activated C3 even when properdin was functional. Finally, properdin binding to glucan particles (GP) and zymosan in serum required active C3. Properdin colocalized with bound C3, suggesting that in the presence of serum, properdin bound indirectly to glycans through C3 convertases. These findings provide a better understanding of how properdin facilitates AP activation by fungi through interaction with the cell wall components.
Agarwal, Sarika; Specht, Charles A.; Huang, Haibin; Ostroff, Gary R.; Ram, Sanjay; Rice, Peter A.; Levitz, Stuart M.
During solubilization of immune complexes C3b becomes fixed to the immunoglobulin part and serves as a receptor for the alternative complement pathway control protein H. The H-C3b immune complex interaction can be made detectable using 4% polyethyleneglycol to separate free from bound /sup 125/I-H. Tetanus toxoid (Te)/anti-Te complexes kept soluble with fresh serum and containing 125 IU of specific antibody bound 18% of /sup 125/I-H; when fresh serum was chelated with 10 mM EDTA, /sup 125/I-H binding was only 5%. On sucrose density gradients, the H-binding material sedimented in the range of 12 to 30 S. In 36 serum samples from rheumatoid arthritis (RA) patients and in 12 serum samples from patients with systemic lupus erythematosus (SLE), /sup 125/I-H binding was significantly elevated to 9.5 +/- 4.7% (mean +/- 1 SD) and 13.3 +/- 5.6%, respectively, while /sup 125/I-H binding by 36 normal human sera was 4 +/- 2%. RA samples (17/36, 47%) and SLE samples (9/12, 75%) had H-binding values increased by more than 2 SD above the normal mean. The serum samples were also assessed for conglutinin- and C1q-binding activities; a significant correlation between H and C1q binding was observed (P less than 0.001); there was no correlation between H and conglutinin binding. Although binding to immune complexes through its interaction with C3b, H clearly detects a population of complexes other than conglutinin, thus expanding the possibilities of further characterizing pathological complexes.
Nydegger, U.E.; Corvetta, A.; Spaeth, P.J.; Spycher, M.
We have investigated the interaction between long circulating poly(ethylene glycol)-stabilized single-walled carbon nanotubes (SWNTs) and the complement system. Aminopoly(ethylene glycol)5000–distearoylphosphatidylethanolamine (aminoPEG5000–DSPE) and methoxyPEG5000–DSPE coated as-grown HIPco SWNTs activated complement in undiluted normal human serum as reflected in significant rises in C4d and SC5b-9 levels, but not the alternative pathway split-product Bb, thus indicating activation exclusively through C4 cleavage. Studies in C2-depleted serum confirmed that PEGylated nanotube-mediated elevation of SC5b-9 was C4b2a convertase-dependent. With the aid of monoclonal antibodies against C1s and human serum depleted from C1q, nanotube-mediated complement activation in C1q-depleted serum was also shown to be independent of classical pathway. Nanotube-mediated C4d elevation in C1q-depleted serum, however, was inhibited by N-acetylglucosamine, Futhan (a broad-spectrum serine protease inhibitor capable of preventing complement activation through all three pathways) and anti-MASP-2 antibodies; this strongly suggests a role for activation of MASP-2 in subsequent C4 cleavage and assembly of C4b2a covertases. Intravenous injection of PEGylated nanotubes in some rats was associated with a significant rise in plasma thromboxane B2 levels, indicative of in vivo nanotube-mediated complement activation. The clinical implications of these observations are discussed.
Hamad, Islam; Hunter, A. Christy; Rutt, Kenneth J.; Liu, Zhuang; Dai, Hongjie; Moghimi, S. Moein
Fulminant hepatic failure (FHF) is a clinically severe type of liver injury with an extremely high mortality rate. Although the pathological mechanisms of FHF are not well understood, evidence suggests that the complement system is involved in the pathogenesis of a variety of liver disorders. In the present study, to investigate the role of complement in FHF, we examined groups of mice following intraperitoneal injection of LPS/D-GalN: wild-type C57BL/6 mice, wild-type mice treated with a C3aR antagonist, C5aR monoclonal antibody (C5aRmAb) or CR2-Factor H (CR2-fH, an inhibitor of the alternative pathway), and C3 deficient mice (C3?/? mice). The animals were euthanized and samples analyzed at specific times after LPS/D-GalN injection. The results show that intraperitoneal administration of LPS/D-GalN activated the complement pathway, as evidenced by the hepatic deposition of C3 and C5b-9 and elevated serum levels of the complement activation product C3a, the level of which was associated with the severity of the liver damage. C3a receptor (C3aR) and C5a receptor (C5aR) expression was also upregulated. Compared with wild-type mice, C3?/? mice survived significantly longer and displayed reduced liver inflammation and attenuated pathological damage following LPS/D-GalN injection. Similar levels of protection were seen in mice treated with C3aR antagonist,C5aRmAb or CR2-fH. These data indicate an important role for the C3a and C5a generated by the alternative pathway in LPS/D-GalN-induced FHF. The data further suggest that complement inhibition may be an effective strategy for the adjunctive treatment of fulminant hepatic failure. PMID:22069473
Sun, Shihui; Guo, Yan; Zhao, Guangyu; Zhou, Xiaojun; Li, Junfeng; Hu, Jingya; Yu, Hong; Chen, Yu; Song, Hongbin; Qiao, Fei; Xu, Guilian; Yang, Fei; Wu, Yuzhang; Tomlinson, Stephen; Duan, Zhongping; Zhou, Yusen
Fulminant hepatic failure (FHF) is a clinically severe type of liver injury with an extremely high mortality rate. Although the pathological mechanisms of FHF are not well understood, evidence suggests that the complement system is involved in the pathogenesis of a variety of liver disorders. In the present study, to investigate the role of complement in FHF, we examined groups of mice following intraperitoneal injection of LPS/D-GalN: wild-type C57BL/6 mice, wild-type mice treated with a C3aR antagonist, C5aR monoclonal antibody (C5aRmAb) or CR2-Factor H (CR2-fH, an inhibitor of the alternative pathway), and C3 deficient mice (C3?/? mice). The animals were euthanized and samples analyzed at specific times after LPS/D-GalN injection. The results show that intraperitoneal administration of LPS/D-GalN activated the complement pathway, as evidenced by the hepatic deposition of C3 and C5b-9 and elevated serum levels of the complement activation product C3a, the level of which was associated with the severity of the liver damage. C3a receptor (C3aR) and C5a receptor (C5aR) expression was also upregulated. Compared with wild-type mice, C3?/? mice survived significantly longer and displayed reduced liver inflammation and attenuated pathological damage following LPS/D-GalN injection. Similar levels of protection were seen in mice treated with C3aR antagonist,C5aRmAb or CR2-fH. These data indicate an important role for the C3a and C5a generated by the alternative pathway in LPS/D-GalN-induced FHF. The data further suggest that complement inhibition may be an effective strategy for the adjunctive treatment of fulminant hepatic failure.
Zhao, Guangyu; Zhou, Xiaojun; Li, Junfeng; Hu, Jingya; Yu, Hong; Chen, Yu; Song, Hongbin; Qiao, Fei; Xu, Guilian; Yang, Fei; Wu, Yuzhang; Tomlinson, Stephen; Duan, Zhongping; Zhou, Yusen
Mannan binding protein (MBP) is a C-type lectin and has a high affinity to mannose and N-acetyl glucosamine. It is also known to activate C4 and C2 without C1 component, which is called ‘lectin pathway’. We now report the presence of MBP and MBP-mediated complement activation in renal glomeruli of IgA nephropathy patients using an immunohistochemical method. In 7 of
Mitsuhiro Matsuda; Kenichi Shikata; Jun Wada; Hikaru Sugimoto; Yasushi Shikata; Toshisuke Kawasaki; Hirofumi Makino
Brucella spp. are gram-negative intracellular pathogens that survive and multiply within phagocytic cells of their hosts. Smooth organisms present O polysaccharides (OPS) on their surface. These OPS help the bacteria avoid the bactericidal action of serum. The wboA gene, coding for the enzyme glycosyltransferase, is essential for the synthesis of O chain in Brucella. In this study, the sensitivity to
CARMEN M. FERNANDEZ-PRADA; MIKELJON NIKOLICH; RAMESH VEMULAPALLI; NAMMALWAR SRIRANGANATHAN; STEPHEN M. BOYLE; GERHARDT G. SCHURIG; TED L. HADFIELD; DAVID L. HOOVER
Hematopoietic stem cell transplant (HSCT)-associated thrombotic microangiopathy (TMA) is a complication that occurs in 25% to 35% of HSCT recipients and shares histomorphologic similarities with hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). The hallmark of all thrombotic microangiopathies is vascular endothelial cell injury of various origins, resulting in microangiopathic hemolytic anemia, platelet consumption, fibrin deposition in the microcirculation, and tissue damage. Although significant advances have been made in understanding the pathogenesis of other thrombotic microangiopathies, post-HSCT TMA remains poorly understood. We report an analysis of the complement alternative pathway, which has recently been linked to the pathogenesis of both the Shiga toxin mediated and the atypical forms of HUS, with a focus on genetic variations in the complement Factor H (CFH) gene cluster and CFH autoantibodies in six children with post-HSCT TMA. We identified a high prevalence of deletions in CFH-related genes 3 and 1 (delCFHR3-CFHR1) and CFH autoantibodies in these patients with HSCT-TMA. Conversely, CFH autoantibodies were not detected in 18 children undergoing HSCT who did not develop TMA. Our observations suggest that complement alternative pathway dysregulation may be involved in the pathogenesis of post-HSCT TMA. These findings shed light on a novel mechanism of endothelial injury in transplant-TMA and may therefore guide the development of targeted treatment interventions. PMID:23814021
Jodele, Sonata; Licht, Christoph; Goebel, Jens; Dixon, Bradley P; Zhang, Kejian; Sivakumaran, Theru A; Davies, Stella M; Pluthero, Fred G; Lu, Lily; Laskin, Benjamin L
Polygonatum cyrtonema lectin (PCL), a mannose/sialic acid-binding lectin, has been reported to display remarkable anti-proliferative and apoptosis-inducing activities toward a variety of cancer cells; however, the precise molecular mechanisms by which PCL induces cancer cell death are still elusive. In the current study, we found that PCL could induce apoptosis and autophagy in murine fibrosarcoma L929 cells. Subsequently, we demonstrated that inhibition of Ras could promote L929 cell death, suggesting that Ras-Raf signaling pathway plays the key negative regulator in PCL-induced apoptosis. And, we showed that Ras-Raf signaling pathway was also involved in PCL-induced autophagy as the negative regulator. In addition, we found that class I phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathway could play the negative regulator in PCL-induced apoptosis and autophagy. Taken together, these results demonstrate that PCL induces murine fibrosarcoma L929 cell apoptosis and autophagy via blocking Ras-Raf and PI3K-Akt signaling pathways. PMID:20713122
Liu, Bo; Wu, Jin-ming; Li, Jing; Liu, Jun-jie; Li, Wen-wen; Li, Chun-yang; Xu, Huai-long; Bao, Jin-ku
Incubation of different dilutions of alligator serum with sheep red blood cells (SRBCs) that had not been sensitized with antibodies resulted in concentration-dependent hemolytic activity. This hemolytic activity was not affected by the presence of ammonium hydroxide and methylamine, known inactivators of the classical complement cascade. However, the hemolytic activities were inhibited by EDTA and salicylaldoxime, indicating that the alternate
Mark E. Merchant; Cherie M. Roche; Damon Thibodeaux; Ruth M. Elsey
Purpose To investigate the influence of the Factor H (CFH) Tyr402His polymorphism on the plasma levels of the alternative pathway proteins CFH, C3, Factor B (FB), Factor D (FD), and Factor I (FI) and the inflammatory marker C-reactive protein (CRP) in 119 patients with age-related macular degeneration (AMD) and 152 unrelated control individuals. Methods Patients with AMD and the control group were separated according to CFH polymorphism, age, and gender. Plasma complement proteins and CRP concentrations were determined with enzyme-linked immunosorbent assay, immunodiffusion, or nephelometry. Results Significant differences in the concentrations of FD and FI were observed between the patients with AMD and the control individuals. We observed significantly reduced FD plasma levels in patients with AMD. We also identified a significant decrease in CFH plasma levels in female patients with AMD in relation to female controls. Plasma FI levels were significantly increased in patients with AMD compared to the control group. Regarding gender, a significant increase in FI plasma levels was observed in male patients. Finally, we found no significant correlation between the CFH Tyr402His polymorphism and the CFH, C3, FB, FD, FI, and CRP plasma levels. Conclusions Patients with AMD present altered levels of FD and FI in a manner independent of this CFH polymorphism, and gender apparently contributes to the plasma levels of these two proteins in patients with AMD and control individuals.
Silva, Aldacilene Souza; Teixeira, Anderson Gustavo; Bavia, Lorena; Lin, Fabio; Velletri, Roberta; Belfort, Rubens
Properdin, the only positive regulatory protein of the complement system, acts as both a stabilizer of the alternative pathway (AP) convertases and as a selective pattern recognition molecule of certain microorganisms and host cells (i.e., apoptotic/necrotic cells) by serving as a platform for de novo C3b,Bb assembly. Properdin, a highly positively charged protein, normally exists as cyclic dimers (P(2)), trimers (P(3)), and tetramers (P(4)) of head-to-tail associations of monomeric 53 kDa subunits. While most complement proteins are produced mainly in the liver, properdin is synthesized primarily by various cell types, including neutrophils, monocytes, primary T cells, and shear-stressed endothelial cells resulting in properdin serum levels of 4-25 ?g/ml. Multiple inflammatory agonists stimulate the release of properdin from stimulated leukocytes into the cellular microenvironment. Concentrated, focused increases in properdin levels may lead to stabilization and initiation of AP convertases, thus greatly amplifying the complement response to a local stimulus. This review highlights current knowledge related to these properties and discusses the implications of properdin production in a pro-inflammatory microenvironment. PMID:23335922
Cortes, Claudio; Ohtola, Jennifer A; Saggu, Gurpanna; Ferreira, Viviana P
Wollastonite fibers were tested in vitro for their ability to produce reactive oxygen species (ROS) with two different systems: a cell-free reactive mixture containing deoxyribose and a polymorphonuclear leukocyte suspension. After adding the fibers, we measured the thiobarbituric acid-reactive substances produced by deoxyribose degradation and luminol-enhanced chemiluminescence, respectively. Compared with asbestos, wollastonite fibers produced higher ROS levels both in the PMN suspensions and in the cell-free reactive mixtures. A large amount of these ROS were not hydroxyl radicals. Indeed we obtained remarkable differences in ROS generation between unground and ground wollastonite fibers and negative results with fibers modified with ferric chloride and dithionite. In addition, ROS generation was partially inhibited (by 46-54%) in the reactions performed in the presence of 1,3-dimethyl-2-thiourea (DMTU), a strong hydroxyl radical scavenger. Wollastonite fibers were also analyzed for their ability to lyse erythrocytes and activate complement. Hemolytic potency was about twice that of chrysotile and half that of crocidolite. The levels of complement activation (via the alternate pathway) were about four-fifths of those measured in zymosan-activated plasma (a typical stimulus used to activate the alternate pathway), equal to those obtained with crocidolite, and two-thirds of those found with chrysotile. The addition of DMTU markedly reduced both these activities. Since asbestos fiber toxicity is mainly due to hydroxyl radical generation, our results indicate that wollastonite fibers are probably less toxic than asbestos fibers. PMID:9720138
Governa, M; Camilucci, L; Amati, M; Visonà, I; Valentino, M; Botta, G C; Campopiano, A; Fanizza, C
The lectin from Canavalia ensiformis (Concanavalin-A, ConA), one of the most abundant lectins known, enables one to mimic biological lectin/carbohydrate interactions that regulate extracellular matrix protein recognition. As such, ConA is known to induce membrane type-1 matrix metalloproteinase (MT1-MMP) which expression is increased in brain cancer. Given that MT1-MMP correlated to high expression of cyclooxygenase (COX)-2 in gliomas with increasing histological grade, we specifically assessed the early proinflammatory cellular signaling processes triggered by ConA in the regulation of COX-2. We found that treatment with ConA or direct overexpression of a recombinant MT1-MMP resulted in the induction of COX-2 expression. This increase in COX-2 was correlated with a concomitant decrease in phosphorylated AKT suggestive of cell death induction, and was independent of MT1-MMP's catalytic function. ConA- and MT1-MMP-mediated intracellular signaling of COX-2 was also confirmed in wild-type and in Nuclear Factor-kappaB (NF-kappaB) p65(-/-) mutant mouse embryonic fibroblasts (MEF), but was abrogated in NF-kappaB1 (p50)(-/-) and in I kappaB kinase (IKK) gamma(-/-) mutant MEF cells. Collectively, our results highlight an IKK/NF-kappaB-dependent pathway linking MT1-MMP-mediated intracellular signaling to the induction of COX-2. That signaling pathway could account for the inflammatory balance responsible for the therapy resistance phenotype of glioblastoma cells, and prompts for the design of new therapeutic strategies that target cell surface carbohydrate structures and MT1-MMP-mediated signaling. Concise summary Concanavalin-A (ConA) mimics biological lectin/carbohydrate interactions that regulate the proinflammatory phenotype of cancer cells through yet undefined signaling. Here we highlight an IKK/NF-kappaB-dependent pathway linking MT1-MMP-mediated intracellular signaling to the induction of cyclooxygenase-2, and that could be responsible for the therapy resistance phenotype of glioblastoma cells. PMID:20195390
Sina, Asmaa; Proulx-Bonneau, Sébastien; Roy, Alain; Poliquin, Laurent; Cao, Jian; Annabi, Borhane
The extract of European mistletoe (Viscum album, L) has been used in adjuvant chemotherapy of cancer and mistletoe lectins are considered to be major active components. The present work was performed to investigate the effects of Korean mistletoe lectin (Viscum album L. coloratum agglutinin, VCA) on proliferation and apoptosis of human hepatoma cells as well as the underlying mechamisms for these effects. We showed that VCA induced apoptosis in both SK-Hep-1 (p53-positive) and Hep 3B (p53-negative) cells through p53- and p21-independent pathways. VCA induced apoptosis by down-regulation of Bcl-2 and by up-regulation of Bax functioning upstream of caspase-3 in both cell lines. In addition, we observed down-regulation of telomerase activity in both VCA-treated cells. Our results provide direct evidence of the anti-tumor potential of this biological response which comes from inhibition of telomerase and consequent inducing apoptosis. VCA-induced apoptosis is regulated by mitochondrial controlled pathway independently of p53. These findings are important for the therapy with preparation of mistletoe because they show that telomerase-dependent mechanism can be targeted by VCA in human hepatocarcinoma. Taken together, our results suggest that the VCA, considered as a telomerase-inhibitor, can be envisaged as a candidate for enhancing sensitivity of conventional anticancer drugs. PMID:11885700
Lyu, Su Yun; Choi, Sang Ho; Park, Won Bong
Problem Plasma concentrations of fragment Bb (FBb) are a marker for activation of the alternative pathway of the complement system. High concentrations of FBb in maternal blood, as early as the first trimester, are associated with subsequent spontaneous preterm delivery <34 weeks of gestation. The study aim was to determine whether spontaneous preterm labor with intact membranes (PTL), intra-amniotic infection/inflammation (IAI) or labor at term are associated with alterations in circulating maternal FBb concentrations. Method of Study This cross-sectional study included women in the following groups: 1) non-pregnant (n=40); 2) normal pregnancy (gestational age range 20-36 6/7 weeks, n=63); 2) women at term not in labor (n=70); 3) women at term in spontaneous labor (n=59); 4) patients with an episode of PTL who delivered at term (n=62); 5) PTL without IAI who delivered preterm (n=30); and 6) PTL with IAI who delivered preterm (n=67). Maternal plasma FBb concentrations were determined by ELISA. Results 1) Among patients with PTL, those who had a preterm delivery either with IAI (1.21 ?g/ml, IQR 0.77-2.16) or without IAI (1.13 ?g/ml, IQR 0.92-2.08;) had a higher median maternal plasma FBb concentration than those who delivered at term (0.86 ?g/ml, IQR 0.64-1.57; p=0.007 and p=0.026, respectively); 2) there was no difference in the median plasma FBb concentration between patients with and without IAI who delivered preterm (p=0.9); 3) in contrast, spontaneous labor at term was not associated with a significant change in the maternal plasma FBb concentration (p=0.8); 4) maternal plasma concentration of FBb did not differ significantly between normal pregnant women and the non-pregnant controls (p=0.8) and were not correlated with advancing gestational age (r ?0.28, p=0.8). Conclusions 1) Preterm parturition is associated with activation of the alternative complement pathway in maternal circulation; 2) such activation is not detectable in spontaneous labor at term; 3) intra-amniotic infection/inflammation does not explain the activation of the alternative pathway of complement in preterm labor. Collectively, these observations suggest that preterm and term labor have fundamental differences in the regulation of innate immunity.
Vaisbuch, Edi; Romero, Roberto; Erez, Offer; Mazaki-Tovi, Shali; Kusanovic, Juan Pedro; Soto, Eleazar; Dong, Zhong; Chaiworapongsa, Tinnakorn; Kim, Sun Kwon; Ogge, Giovanna; Pacora, Percy; Yeo, Lami; Hassan, Sonia S.
Misregulation of the innate immune response and other immune-related processes have been suggested to play a critical role in the pathogenesis of a number of different neurodegenerative diseases, including age related macular degeneration. In an animal model for photoreceptor degeneration, several genes of the innate and acquired immune system were found to be differentially regulated in the retina during the degenerative process. In addition to this differential regulation of individual genes, we found that in the rd1 retina a significantly higher number of genes involved in immune-related responses were expressed at any given time during the degenerative period. The peak of immune-related gene expression was at postnatal day 14, coinciding with the peak of photoreceptor apoptosis in the rd1 mouse. We directly tested the potential involvement of acquired and innate immune responses in initiation and progression of photoreceptor degeneration by analyzing double mutant animals. Retinal morphology and photoreceptor apoptosis of rd1 mice on a SCID genetic background (no mature T- and B-cells) or in combination with a RAG-1 (no functional B- and T-cells) or a C1q? (no functional classical complement activation pathway) knockout was followed during the degenerative process using light microscopy or TUNEL staining, respectively. Although complement factor C1q? was highly up-regulated in the rd1 retina concomitantly with the degenerative process, lack of this protein did not protect the rd1 retina. Similarly, retinal degeneration and photoreceptor apoptosis appeared to proceed normally in the rd1 mouse lacking functional B- and T-cells. Our results suggest that both, the classical complement system of innate immunity and a functional acquired immune response are not essential for the degenerative process in the rd1 mouse retina.
Rohrer, Barbel; Demos, Christina; Frigg, Rico; Grimm, Christian
The transmembrane gloycoprotein gp41 of HIV-1 contains a C1q binding domain (HIVenv 583–610) and activates the human complement system through the classical pathway. Based on structural and functional similarities between human defensins (human neutrophil peptide, HNP 1–3) and synthetic peptides representing the env 583–610 region of HIV-1, we found it interesting to investigate the C1q binding and complement activating ability
Zolta´n Proha´szka; Katalin Ne´met; Pe´ter Csermely; Ferenc Hudecz
The potential bactericidal activity of the alternative complement pathway of mammalian and reptilian sera to Borrelia burgdorferi sensu stricto (s.s.) was evaluated in vitro. Complement-mediated killing was observed when cultured spirochetes were inoculated into sera from the western fence lizard (Sceloporus occidentalis) and from the southern alligator lizard (Elgaria multicarinata), but not when they were inoculated into serum from either the deer mouse (Peromyscus maniculatus) or from humans. Spirochetes were still alive after 4 hr in lizard serum that had been preheated at 56 C for 30 min to inactivate complement. Furthermore, when lizard serum was chelated with 10 mM ethylenediaminetetraacetic acid to block all complement activation, borreliacidal activity was arrested. When lizard serum was chelated with 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus 4 mM MgCl2 to block only classical complement pathway activation, >85% of spirochetes were immobilized within 1 hr. Differences in B. burgdorferi s.s. mortality were not observed when chelators with or without MgCl2 were added to serum from either deer mice or humans. Proteins comprising the alternative complement pathway are responsible for the borreliacidal activity observed in the blood of S. occidentalis and E. multicarinata. PMID:11191895
Kuo, M M; Lane, R S; Giclas, P C
The excitotoxicity induced by excessive activation of the glutamatergic neurotransmission pathway is involved in several neuropathologies. In this sense, molecules that prevent the release of glutamate or the excessive activation of its receptors can be useful in preventing the neuronal cell death observed in these diseases. Lectins are proteins capable of reversible binding to the carbohydrates in glycoconjugates, and some have been used in the study and purification of glutamate receptors. ConBr is a mannose/glucose-binding lectin purified from Canavalia brasiliensis seeds. In the present study, we aimed to evaluate the neuroprotective activity of ConBr against glutamate-induced excitotoxicity. Hippocampal slices were isolated from adult male mice and incubated for 6h in Krebs saline/DMEM buffer alone (control), in the presence of glutamate or glutamate plus ConBr. The phosphorylation of Akt and mitogen activated protein kinases (MAPKs) such as ERK1/2, p38(MAPK) and JNK1/2/3 was evaluated with western blotting. The results indicate that glutamate provoked a reduction in the hippocampal slice viability (-25%), diminished the phosphorylation of Akt and augmented p38(MAPK) and ERK1 phosphorylation. No changes were observed in the phosphorylation of JNK1/2/3 or ERK2. Notably, ConBr, through a mechanism dependent on carbohydrate interaction, prevented the reduction of cell viability and Akt phosphorylation induced by glutamate. Furthermore, in the presence of the PI3K inhibitor LY294002, ConBr was unable to reverse glutamate neurotoxicity. Taken together, our data suggest that the neuroprotective effect of ConBr against glutamate neurotoxicity requires oligosaccharide interaction and is dependent on the PI3K/Akt pathway. PMID:23454192
Jacques, Amanda V; Rieger, Débora K; Maestri, Mariana; Lopes, Mark W; Peres, Tanara V; Gonçalves, Filipe M; Pedro, Daniela Z; Tasca, Carla I; López, Manuela G; Egea, Javier; Nascimento, Kyria S; Cavada, Benildo S; Leal, Rodrigo B
Mannose-binding lectin (MBL), a plasma C-type lectin, plays an important role in innate immunity. However, the interaction, and the consequences of it, between MBL and the immune system remain ill defined. We have investigated the contributing mechanisms and effects of MBL on the proliferation of human monocytes. At lower concentrations (?4 ?g/ml) MBL was shown to partially enhance monocyte proliferation. By contrast, at higher concentrations (8-20 ?g/ml) of MBL, cell proliferation was markedly attenuated. MBL-induced growth inhibition was associated with G0/G1 arrest, down-regulation of cyclin D1/D3, cyclin-dependent kinase (Cdk) 2/Cdk4 and up-regulation of the Cdk inhibitory protein Cip1/p21. Additionally, MBL induced apoptosis, and did so through caspase-3 activation and poly ADP-ribose polymerase (PARP) cleavage. Moreover, transforming growth factor (TGF)-?1 levels increased in the supernatants of MBL-stimulated monocyte cultures. We also found that MBL-dependent inhibition of monocyte proliferation could be reversed by the TGF-? receptor antagonist SB-431542, or by anti-TGF-?1 antibody, or by the mitogen-activated protein kinase (MAPK) inhibitors specific for p38 (SB203580), but not ERK (U0126) or JNK (SP600125). Thus, at high concentrations, MBL can affect the immune system by inhibiting monocyte proliferation, which suggests that MBL may exhibit anti-inflammatory effects. PMID:24039775
Wang, Yan; Chen, A-De; Lei, Yan-Mei; Shan, Gui-Qiu; Zhang, Li-Yun; Lu, Xiao; Chen, Zheng-Liang
Candida albicans activates the classical and alternative complement pathways, leading to deposition of opsonic complement fragments on the cell surface. Our previous studies found that antimannan immunoglobulin G (IgG) in normal human serum (NHS) allows C. albicans to initiate the classical pathway. The purpose of this study was to determine whether antimannan IgG also plays a role in initiation of the alternative pathway. Pooled NHS was rendered free of classical pathway activity by chelation of serum Ca2+ with EGTA alone or in combination with immunoaffinity removal of antimannan antibodies. Kinetic analysis revealed a 6-min lag in detection of C3 binding to C. albicans incubated in EGTA-chelated NHS, compared to a 12-min lag in NHS that was both EGTA chelated and mannan absorbed. The 12-min lag was shortened to 6 min by addition of affinity-purified antimannan IgG. The accelerating effect of antimannan IgG on alternative pathway initiation was dose dependent and was reproduced in a complement binding reaction consisting of six purified proteins of the alternative pathway. Both Fab and F(ab?)2 fragments of antimannan IgG facilitated alternative pathway initiation in a manner similar to that observed with intact antibody. Immunofluorescence analysis showed that addition of antimannan IgG to EGTA-chelated and mannan-absorbed serum promoted an early deposition of C3 molecules on the yeast cells but had little or no effect on distribution of the cellular sites for C3 activation. Thus, antimannan IgG antibodies play an important regulatory role in interactions between the host complement system and C. albicans.
Zhang, Mason X.; Kozel, Thomas R.
Chlamydia is an obligate intracellular bacterium that grows and replicates inside a cytoplasmic inclusion. We report that a host protein, CD59, which regulates complement function at the surfaces of uninfected cells, can be detected at the membrane of the chlamydial inclusion. This localization to the inclusion membrane was specific for CD59 and not a general feature of other glycosylphosphatidylinositol (GPI)-anchored proteins or representative cell surface proteins. Using differential permeabilization studies, we showed that CD59 is localized to the luminal but not the cytoplasmic face of the inclusion membrane, consistent with membrane association via its GPI anchor. Furthermore, CD59 was present at the inclusion even when we prevented it from associating with membrane microdomains via the GPI anchor or when we inhibited general protein transport to the cell surface, indicating that a conventional Golgi apparatus-dependent trafficking mechanism was not involved. Based on these findings, we propose that selected host proteins are trafficked to the inclusion by a Golgi apparatus-independent pathway during a Chlamydia infection.
Hasegawa, Ayako; Sogo, L. Farah; Tan, Ming; Sutterlin, Christine
Chlamydia is an obligate intracellular bacterium that grows and replicates inside a cytoplasmic inclusion. We report that a host protein, CD59, which regulates complement function at the surfaces of uninfected cells, can be detected at the membrane of the chlamydial inclusion. This localization to the inclusion membrane was specific for CD59 and not a general feature of other glycosylphosphatidylinositol (GPI)-anchored proteins or representative cell surface proteins. Using differential permeabilization studies, we showed that CD59 is localized to the luminal but not the cytoplasmic face of the inclusion membrane, consistent with membrane association via its GPI anchor. Furthermore, CD59 was present at the inclusion even when we prevented it from associating with membrane microdomains via the GPI anchor or when we inhibited general protein transport to the cell surface, indicating that a conventional Golgi apparatus-dependent trafficking mechanism was not involved. Based on these findings, we propose that selected host proteins are trafficked to the inclusion by a Golgi apparatus-independent pathway during a Chlamydia infection. PMID:19168743
Hasegawa, Ayako; Sogo, L Farah; Tan, Ming; Sütterlin, Christine
Background The genus Micrurus, coral snakes (Serpentes, Elapidae), comprises more than 120 species and subspecies distributed from the south United States to the south of South America. Micrurus snake bites can cause death by muscle paralysis and further respiratory arrest within a few hours after envenomation. Clinical observations show mainly neurotoxic symptoms, although other biological activities have also been experimentally observed, including cardiotoxicity, hemolysis, edema and myotoxicity. Results In the present study we have investigated the action of venoms from seven species of snakes from the genus Micrurus on the complement system in in vitro studies. Several of the Micrurus species could consume the classical and/or the lectin pathways, but not the alternative pathway, and C3a, C4a and C5a were generated in sera treated with the venoms as result of this complement activation. Micrurus venoms were also able to directly cleave the ? chain of the component C3, but not of the C4, which was inhibited by 1,10 Phenanthroline, suggesting the presence of a C3? chain specific metalloprotease in Micrurus spp venoms. Furthermore, complement activation was in part associated with the cleavage of C1-Inhibitor by protease(s) present in the venoms, which disrupts complement activation control. Conclusion Micrurus venoms can activate the complement system, generating a significant amount of anaphylatoxins, which may assist due to their vasodilatory effects, to enhance the spreading of other venom components during the envenomation process.
Activation of the complement system is tightly regulated by plasma and cell-associated complement regulatory proteins (CRPs), such as factor H (fH), decay-accelerating factor, and membrane cofactor protein. Animal models of disease have provided considerable insights into the important roles for CRPs in the kidney. Mice deficient in fH have excessive fluid phase C3 activation and inactivation, leading to deposition of inactivated C3b in glomerular capillary walls (GCW), comparable with dense deposit disease. In contrast, when fH lacks C-terminal surface targeting regions, local activation on the GCW leads to a disease reminiscent of thrombotic microangiopathy. The uniquely rodent protein, CR1-related y (Crry), has features analogous to human membrane cofactor protein. Defective Crry leads to unrestricted alternative pathway activation in the tubulointerstitium, resulting in pathologic features ranging from thrombotic microangiopathy (TMA), acute kidney injury, and tubulointerstitium nephritis. In the presence of initiators of the classic or lectin pathways, commonly in the form of immune complexes in human glomerular diseases, complement regulation is stressed, with the potential for recruitment of the spontaneously active alternative pathway. The threshold for this activation is set by CRPs; pathology is more likely when complement regulation is defective. Within the endocapillary region of the GCW, fH is key, while decay-accelerating factor and Crry are protective on mesangial cells and podocytes. Arguably, acquired alterations in these CRPs is a more common event, extending from pathologic states of cellular injury or production of inhibitory antibodies, to physiological fine tuning of the adaptive immune response. PMID:24161042
Naik, Abhijit; Sharma, Shweta; Quigg, Richard J
Spirochetes belonging to the Borrelia (B.) burgdorferi sensu lato complex differ in their resistance to complement-mediated killing, particularly in regard to human serum. In the present study, we elucidate the serum and complement susceptibility of B. valaisiana, a genospecies with the potential to cause Lyme disease in Europe as well as in Asia. Among the investigated isolates, growth of ZWU3 Ny3 was not affected while growth of VS116 and Bv9 was strongly inhibited in the presence of 50% human serum. Analyzing complement activation, complement components C3, C4 and C6 were deposited on the surface of isolates VS116 and Bv9, and similarly the membrane attack complex was formed on their surface. In contrast, no surface-deposited components and no aberrations in cell morphology were detected for serum-resistant ZWU3 Ny3. While further investigating the protective role of bound complement regulators in mediating complement resistance, we discovered that none of the B. valaisiana isolates analyzed bound complement regulators Factor H, Factor H-like protein 1, C4b binding protein or C1 esterase inhibitor. In addition, B. valaisiana also lacked intrinsic proteolytic activity to degrade complement components C3, C3b, C4, C4b, and C5. Taken together, these findings suggest that certain B. valaisiana isolates differ in their capability to resist complement-mediating killing by human serum. The molecular mechanism utilized by B. valaisiana to inhibit bacteriolysis appears not to involve binding of the key host complement regulators of the alternative, classical, and lectin pathways as already known for serum-resistant Lyme disease or relapsing fever borreliae. PMID:23320099
Schwab, Jasmin; Hammerschmidt, Claudia; Richter, Dania; Skerka, Christine; Matuschka, Franz-Rainer; Wallich, Reinhard; Zipfel, Peter F; Kraiczy, Peter
The complement system is key to innate immunity and its activation is necessary for the clearance of bacteria and apoptotic cells. However, insufficient or excessive complement activation will lead to immune-related diseases. It is so far unknown how the complement activity is up- or down- regulated and what the associated pathophysiological mechanisms are. To quantitatively understand the modulatory mechanisms of the complement system, we built a computational model involving the enhancement and suppression mechanisms that regulate complement activity. Our model consists of a large system of Ordinary Differential Equations (ODEs) accompanied by a dynamic Bayesian network as a probabilistic approximation of the ODE dynamics. Applying Bayesian inference techniques, this approximation was used to perform parameter estimation and sensitivity analysis. Our combined computational and experimental study showed that the antimicrobial response is sensitive to changes in pH and calcium levels, which determines the strength of the crosstalk between CRP and L-ficolin. Our study also revealed differential regulatory effects of C4BP. While C4BP delays but does not decrease the classical complement activation, it attenuates but does not significantly delay the lectin pathway activation. We also found that the major inhibitory role of C4BP is to facilitate the decay of C3 convertase. In summary, the present work elucidates the regulatory mechanisms of the complement system and demonstrates how the bio-pathway machinery maintains the balance between activation and inhibition. The insights we have gained could contribute to the development of therapies targeting the complement system.
Tan, Pei Yi; Hsu, David; Blom, Anna M.; Leong, Benjamin; Sethi, Sunil; Ho, Bow; Ding, Jeak Ling; Thiagarajan, P. S.
Summary: The complement system comprises several fluid-phase and membrane-associated proteins. Under physiological conditions, activation of the fluid-phase components of complement is maintained under tight control and complement activation occurs primarily on surfaces recognized as “nonself” in an attempt to minimize damage to bystander host cells. Membrane complement components act to limit complement activation on host cells or to facilitate uptake of antigens or microbes “tagged” with complement fragments. While this review focuses on the role of complement in infectious diseases, work over the past couple of decades has defined several important functions of complement distinct from that of combating infections. Activation of complement in the fluid phase can occur through the classical, lectin, or alternative pathway. Deficiencies of components of the classical pathway lead to the development of autoimmune disorders and predispose individuals to recurrent respiratory infections and infections caused by encapsulated organisms, including Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. While no individual with complete mannan-binding lectin (MBL) deficiency has been identified, low MBL levels have been linked to predisposition to, or severity of, several diseases. It appears that MBL may play an important role in children, who have a relatively immature adaptive immune response. C3 is the point at which all complement pathways converge, and complete deficiency of C3 invariably leads to severe infections, including those caused by meningococci and pneumococci. Deficiencies of the alternative and terminal complement pathways result in an almost exclusive predisposition to invasive meningococcal disease. The spleen plays an important role in antigen processing and the production of antibodies. Splenic macrophages are critical in clearing opsonized encapsulated bacteria (such as pneumococci, meningococci, and Escherichia coli) and intraerythrocytic parasites such as those causing malaria and babesiosis, which explains the fulminant nature of these infections in persons with anatomic or functional asplenia. Paramount to the management of patients with complement deficiencies and asplenia is educating patients about their predisposition to infection and the importance of preventive immunizations and seeking prompt medical attention.
Ram, Sanjay; Lewis, Lisa A.; Rice, Peter A.
Mosquito-borne alphaviruses such as chikungunya virus and Ross River virus (RRV) are emerging pathogens capable of causing large-scale epidemics of virus-induced arthritis and myositis. The pathology of RRV-induced disease in both humans and mice is associated with induction of the host inflammatory response within the muscle and joints, and prior studies have demonstrated that the host complement system contributes to development of disease. In this study, we have used a mouse model of RRV-induced disease to identify and characterize which complement activation pathways mediate disease progression after infection, and we have identified the mannose binding lectin (MBL) pathway, but not the classical or alternative complement activation pathways, as essential for development of RRV-induced disease. MBL deposition was enhanced in RRV infected muscle tissue from wild type mice and RRV infected MBL deficient mice exhibited reduced disease, tissue damage, and complement deposition compared to wild-type mice. In contrast, mice deficient for key components of the classical or alternative complement activation pathways still developed severe RRV-induced disease. Further characterization of MBL deficient mice demonstrated that similar to C3?/? mice, viral replication and inflammatory cell recruitment were equivalent to wild type animals, suggesting that RRV-mediated induction of complement dependent immune pathology is largely MBL dependent. Consistent with these findings, human patients diagnosed with RRV disease had elevated serum MBL levels compared to healthy controls, and MBL levels in the serum and synovial fluid correlated with severity of disease. These findings demonstrate a role for MBL in promoting RRV-induced disease in both mice and humans and suggest that the MBL pathway of complement activation may be an effective target for therapeutic intervention for humans suffering from RRV-induced arthritis and myositis.
Whitmore, Alan C.; Blevins, Lance K.; Hueston, Linda; Fraser, Robert J.; Herrero, Lara J.; Ramirez, Ruben; Smith, Paul N.; Mahalingam, Suresh; Heise, Mark T.
Mannose-binding lectin (MBL), a pattern recognition innate immune molecule, selectively binds distinct chemical patterns, including carbohydrates expressed on Group B streptococcus (GBS). MBL interacts with IgM, resulting in the activation of MBL-associated serine proteases (MASPs), thus is initiating a lectin complement pathway. Complement proteins and IgM modulate production of antigen specific antibody. In this study, we investigated the relative effect of MBL in antibody response against tetanus toxoid-conjugated GBS polysaccharide vaccines (GBS PS-TT) by comparing wild type and null mice for MBL, complement 3 (C3), IgM, MBL/C3, and MBL/IgM. We found that GBS PS specific IgG response was upregulated in MBL deficient mice following immunization with GBS PS-TT but not GBS PS. B1 cells were expanded in peritonium but not in spleen of MBL null mice. The mechanisms of heightened IgG response in MBL null mice were related to C3, and share the same pathway with IgM.
Guttormsen, Hilde-Kari; Stuart, Lynda; Shi, Lei; Carroll, Mike C.; Chen, Jianzhu; Kasper, Dennis L.; Ezekowitz, R. Alan B.
The complement system functions as an immune surveillance system that rapidly responds to infection. Activation of the complement system by specific recognition pathways triggers a protease cascade, generating cleavage products that function to eliminate pathogens, regulate inflammatory responses, and shape adaptive immune responses. However, when dysregulated, these powerful functions can become destructive and the complement system has been implicated as a pathogenic effector in numerous diseases, including infectious diseases. This review highlights recent discoveries that have identified critical roles for the complement system in the pathogenesis of viral infection.
Stoermer, Kristina A.; Morrison, Thomas E.
Polygonatum cyrtonema lectin (PCL), a mannose\\/sialic acid-binding lectin, has been reported to display remarkable anti-proliferative and apoptosis-inducing activities toward a variety of cancer cells; however, the precise molecular mechanisms by which PCL induces cancer cell death are still elusive. In the current study, we found that PCL could induce apoptosis and autophagy in murine fibrosarcoma L929 cells. Subsequently, we demonstrated that
Bo Liu; Jin-ming Wu; Jing Li; Jun-jie Liu; Wen-wen Li; Chun-yang Li; Huai-long Xu; Jin-ku Bao
Chlamydia is an obligate intracellular bacterium that grows and replicates inside a cytoplasmic inclusion. We report that a host protein, CD59, which regulates complement function at the surfaces of uninfected cells, can be detected at the membrane of the chlamydial inclusion. This localization to the inclusion membrane was specific for CD59 and not a general feature of other glycosylphosphatidylinositol (GPI)-anchored
Ayako Hasegawa; L. Farah Sogo; Ming Tan; Christine Sutterlin
Meningococcal vaccines containing factor H binding protein (fHbp) are in clinical development. fHbp binds human fH, which enables the meningococcus to resist complement-mediated bacteriolysis. Previously, we found that chimeric human IgG1 mouse anti-fHbp monoclonal antibodies (MAbs) had human complement-mediated bactericidal activity only if the MAb inhibited fH binding. Since IgG subclasses differ in their ability to activate complement, we investigated the role of human IgG subclasses on antibody functional activity. We constructed chimeric MAbs in which three different murine fHbp-specific binding domains were each paired with human IgG1, IgG2, or IgG3. Against a wild-type group B isolate, all three IgG3 MAbs, irrespective of their ability to inhibit fH binding, had bactericidal activity that was >5-fold higher than the respective IgG1 MAbs, while the IgG2 MAbs had the least activity. Against a mutant with increased fHbp expression, the anti-fHbp MAbs elicited greater C4b deposition (classical pathway) and greater bactericidal activity than against the wild-type strain, and the IgG1 MAbs had similar or greater activity than the respective IgG3 MAbs. The bactericidal activity against both wild-type and mutant strains also was dependent, in part, on activation of the alternative complement pathway. Thus, at lower epitope density in the wild-type strain, the IgG3 anti-fHbp MAbs had the greatest bactericidal activity. At a higher epitope density in the mutant, the IgG1 MAbs had similar or greater bactericidal activity than the IgG3 MAbs, and the activity was less dependent on the inhibition of fH binding than at a lower epitope density. PMID:22064712
Giuntini, Serena; Reason, Donald C; Granoff, Dan M
Meningococcal vaccines containing factor H binding protein (fHbp) are in clinical development. fHbp binds human fH, which enables the meningococcus to resist complement-mediated bacteriolysis. Previously, we found that chimeric human IgG1 mouse anti-fHbp monoclonal antibodies (MAbs) had human complement-mediated bactericidal activity only if the MAb inhibited fH binding. Since IgG subclasses differ in their ability to activate complement, we investigated the role of human IgG subclasses on antibody functional activity. We constructed chimeric MAbs in which three different murine fHbp-specific binding domains were each paired with human IgG1, IgG2, or IgG3. Against a wild-type group B isolate, all three IgG3 MAbs, irrespective of their ability to inhibit fH binding, had bactericidal activity that was >5-fold higher than the respective IgG1 MAbs, while the IgG2 MAbs had the least activity. Against a mutant with increased fHbp expression, the anti-fHbp MAbs elicited greater C4b deposition (classical pathway) and greater bactericidal activity than against the wild-type strain, and the IgG1 MAbs had similar or greater activity than the respective IgG3 MAbs. The bactericidal activity against both wild-type and mutant strains also was dependent, in part, on activation of the alternative complement pathway. Thus, at lower epitope density in the wild-type strain, the IgG3 anti-fHbp MAbs had the greatest bactericidal activity. At a higher epitope density in the mutant, the IgG1 MAbs had similar or greater bactericidal activity than the IgG3 MAbs, and the activity was less dependent on the inhibition of fH binding than at a lower epitope density.
Giuntini, Serena; Reason, Donald C.
Drosophila melanogaster bearing the Passover mutation fail to jump in response to a light-off stimulus. Pas also disrupts some of the synapses between the neurons of the giant fiber system which mediate this escape behavior. We have mapped Pas to the 19E subdivision of the polytene X chromosome. Our genetic analyses reveal that deletions of either of two nonoverlapping regions fail to fully complement Pas. Heterozygotes of Pas with chromosomal deletions in the vicinity of polytene band 19E3 exhibit the full set of neuronal defects shown by Pas homozygotes. Alleles of the R-9-29 complementation group, which maps to band 19E3, exhibit a complex pattern of complementation with Pas. Heterozygotes combining the lethal R-9-29 alleles with Pas are all viable, some complement the neuronal defects of Pas, but most exhibit these defects. The viable shaking-B(2) mutation also fails to complement Pas, the R-9-29 alleles or the 19E3 deficiencies. The R-9-29 locus may contain two functional domains, one required for viability the other for normal neuronal phenotype. trans-Heterozygotes bearing mutant alleles or a deficiency of the first region (19E3) together with deficiencies of the second region (19E5-6) also exhibit some of the neuronal defects shown by the Passover mutant. Deficiencies which delete the entire 19E3 to 19E6 interval do not produce this phenotype when heterozygous with a normal X chromosome. Thus normal function requires a cis-interaction between the two regions. These findings raise the possibility that the gene mutated by Pas is split or separated from a cis-activator by at least one other gene.
Baird, D. H.; Schalet, A. P.; Wyman, R. J.
The presence of circulating immune complexes (CICs) is a characteristic feature of human lymphatic filariasis. However, the role of CICs in modulating granulocyte function and complement functional activity in filarial infection is unknown. The levels of CICs in association with complement activation in clinically asymptomatic, filarial-infected patients (INF); filarial-infected patients with overt lymphatic pathologic changes (CPDT); and uninfected controls (EN) were examined. Significantly increased levels of CICs and enhanced functional efficiency of the classical and mannose-binding lectin pathways of the complement system was observed in INF compared with CPDT and EN. Polyethylene glycol–precipitated CICs from INF and CPDT induced significantly increased granulocyte activation compared with those from EN, determined by the increased production of neutrophil granular proteins and a variety of pro-inflammatory cytokines. Thus, CIC-mediated enhanced granulocyte activation and modulation of complement function are important features of filarial infection and disease.
Senbagavalli, Prakash; Anuradha, Rajamanickam; Ramanathan, Vadakkuppattu D.; Kumaraswami, Vasanthapuram; Nutman, Thomas B.; Babu, Subash
The purpose of this study was to explore the role of the complement system in normal human pregnancy and preeclampsia in a comprehensive manner, measuring circulating levels of complement proteins, their activation fragments and regulatory factors, as well as those of C-reactive protein (CRP). Sixty preeclamptic patients, 60 healthy pregnant women and 59 healthy non-pregnant women were involved in this case-control study. Circulating levels of complement components and CRP were determined with ELISA, radial immunodiffusion and particle enhanced immunoturbidimetric assay. Levels of CRP, C4d, C3a, SC5b9, C3, C9 and factor H antigen were significantly higher, while those of C1-inhibitor were significantly lower in healthy pregnant than non-pregnant women. In addition, preeclamptic patients had significantly higher CRP, C4d, C3a, SC5b9 levels and significantly lower C3 concentrations as compared to healthy pregnant women. Their CRP, C4d, C3a, SC5b9, C4, C3, C9 and factor H antigen levels were significantly higher, while C1-inhibitor concentrations were significantly lower compared with healthy non-pregnant women. However, no significant difference was found in Bb and C4b-binding protein levels among the three study groups. Preeclamptic patients with fetal growth restriction had significantly higher plasma SC5b9 levels than those without IUGR. There was a relative deficiency of C1-inhibitor and C4b-binding protein, and a relative abundance of factor H both in normal pregnancy and preeclampsia. Activation of the classical or lectin pathway (C4d) showed significant positive correlation to C3 activation (C3a) both in healthy pregnant women and preeclamptic patients. However, the correlation between C3 and terminal pathway activation was dominating only in patients with preeclampsia, but not in healthy pregnant women. In conclusion, the complement system is activated through the classical and/or lectin pathways with increased terminal complex formation in the third trimester of normal human pregnancy, and further in preeclampsia, as shown by the elevated amounts of activation markers in the systemic circulation. Excessive activation of the terminal pathway is associated with fetal growth restriction in preeclamptic women. However, additional studies are required to determine the cause and consequence of systemic complement activation in this pregnancy-specific disorder. PMID:20181396
Derzsy, Zoltán; Prohászka, Zoltán; Rigó, János; Füst, George; Molvarec, Attila
In recent years, research into the role of complement in the immunopathogenesis of renal disease has broadened our understanding of the fragile balance between the protective and harmful functions of the complement system. Interventions into the complement system in various models of immune-mediated renal disease have resulted in both favourable and unfavourable effects and will allow us to precisely define the level of the complement cascade at which a therapeutic intervention will result in an optimal effect. The discovery of mutations of complement regulatory molecules has established a role of complement in the haemolytic uremic syndrome and membranoproliferative glomerulonephritis, and genotyping for mutations of the complement system are already leaving the research laboratory and have entered clinical practice. These clinical discoveries have resulted in the creation of relevant animal models which may provide crucial information for the development of highly specific therapeutic agents. Research into the role of complement in proteinuria has helped to understand pathways of inflammation which ultimately lead to renal failure irrespective of the underlying renal disease and is of major importance for the majority of renal patients. Complement science is a highly exciting area of translational research and hopefully will result in meaningful therapeutic advances in the near future. PMID:17901956
Berger, Stefan P; Daha, Mohamed R
In recent years, research into the role of complement in the immunopathogenesis of renal disease has broadened our understanding of the fragile balance between the protective and harmful functions of the complement system. Interventions into the complement system in various models of immune-mediated renal disease have resulted in both favourable and unfavourable effects and will allow us to precisely define the level of the complement cascade at which a therapeutic intervention will result in an optimal effect. The discovery of mutations of complement regulatory molecules has established a role of complement in the haemolytic uremic syndrome and membranoproliferative glomerulonephritis, and genotyping for mutations of the complement system are already leaving the research laboratory and have entered clinical practice. These clinical discoveries have resulted in the creation of relevant animal models which may provide crucial information for the development of highly specific therapeutic agents. Research into the role of complement in proteinuria has helped to understand pathways of inflammation which ultimately lead to renal failure irrespective of the underlying renal disease and is of major importance for the majority of renal patients. Complement science is a highly exciting area of translational research and hopefully will result in meaningful therapeutic advances in the near future.
Daha, Mohamed R.
Objectives This study assessed the extent and mechanism of complement activation in community-acquired sepsis at presentation to the emergency department (ED) and following 24 hours of quantitative resuscitation. Methods A prospective pilot study of patients with severe sepsis and healthy controls was conducted among individuals presenting to a tertiary care ED. Resuscitation, including antibiotics and therapies to normalize central venous and mean arterial pressure (MAP) and central venous oxygenation, was performed on all patients. Serum levels of Factor Bb (alternative pathway), C4d (classical and mannose-binding lectin [MBL] pathway), C3, C3a, and C5a were determined at presentation and 24 hours later among patients. Results Twenty patients and 10 healthy volunteer controls were enrolled. Compared to volunteers, all proteins measured were abnormally higher among septic patients (C4d 3.5-fold; Factor Bb 6.1-fold; C3 0.8-fold; C3a 11.6-fold; C5a 1.8-fold). Elevations in C5a were most strongly correlated with alternative pathway activation. Surprisingly, a slight but significant inverse relationship between illness severity (by sequential organ failure assessment [SOFA] score) and C5a levels at presentation was noted. Twenty-four hours of structured resuscitation did not, on average, affect any of the mediators studied. Conclusions Patients with community-acquired sepsis have extensive complement activation, particularly of the alternative pathway, at the time of presentation that was not significantly reversed by 24 hours of aggressive resuscitation.
Younger, John G.; Bracho, David O.; Chung-Esaki, Hangyul M.; Lee, Moonseok; Rana, Gurpreet K.; Sen, Ananda; Jones, Alan E.
The mammalian intestine harbors complex societies of beneficial bacteria that are maintained in the lumen with minimal penetration of mucosal surfaces. Microbial colonization of germ-free mice triggers epithelial expression of RegIIIgamma, a secreted C-type lectin. RegIIIgamma binds intestinal bacteria but lacks the complement recruitment domains present in other microbe-binding mammalian C-type lectins. We show that RegIIIgamma and its human counterpart,
Heather L. Cash; Cecilia V. Whitham; Cassie L. Behrendt; Lora V. Hooper
Neisseria meningitidis inhibits the alternative pathway (AP) of complement utilizing diverse mechanisms, including expression of capsule (select serogroups), Neisserial surface protein A (NspA), factor H binding protein (fHbp) and lipooligosaccharide (LOS) sialylation. The contribution of the latter three molecules in AP regulation in encapsulated meningococci was studied using isogenic mutants. When LOS was unsialylated, deleting NspA alone from group A strain A2594 (low fHbp/high NspA) significantly increased AP-mediated C3 deposition. C3 deposition further increased ~2-fold in a ?fHbp?NspA double mutant, indicating cooperative fHbp function. LOS sialylation of A2594 ?fHbp?NspA decreased the rate of C3 deposition, revealing AP inhibition by LOS sialic acid. Maximal C3 deposition on group B strain H44/76 (high fHbp/low NspA) occurred when all three molecules were absent; again, LOS sialylation attenuated the AP in the absence of both fHbp and NspA. When H44/76 LOS was unsialylated, both fHbp and NspA independently inhibited the AP. LOS sialylation enhanced binding of fH C-terminal domains 18–20 to C3 fragments deposited on bacteria. Interaction of meningococci with non-human complement is relevant for animal models and vaccine evaluation studies that employ non-human complement. Consistent with their human-specific fH binding, neither fHbp nor NspA regulated the rat AP. However, LOS sialylation inhibited the rat AP and, as with human serum, enhanced binding of rat fH to surface-bound C3. These data highlight the cooperative roles of meningococcal NspA and fHbp in regulating the human AP and broaden the molecular basis for LOS sialylation in AP regulation on meningococci in more than one animal species.
Lewis, Lisa A.; Carter, Matthew; Ram, Sanjay
Previous investigations characterizing the mechanism(s) of complement resistance in Yersinia pseudotuberculosis showed that the outer membrane protein Ail can functionally recruit the regulator of the classical and lectin pathways of complement, C4b-binding protein. In this study, we extend these observations and show that Ail can also recruit the regulator of the alternative pathway (AP), factor H (fH). Binding to fH was dependent on Ail expression and observed in the context of full-length LPS. Inactivation of ail resulted in loss of fH binding. Ail expression conferred resistance to AP-mediated killing. Bound fH was functional as a cofactor for factor I-mediated cleavage and inactivation of C3b. Ail alone is sufficient to mediate fH binding and resistance to AP-mediated killing, because Ail expression in a laboratory Escherichia coli strain conferred both of these phenotypes. Binding was specific and inhibited by increasing heparin and NaCl concentrations. Using a panel of fH recombinant fragments, we observed that both short consensus repeats 5-7 and 19-20 regions are responsible for mediating the interaction with Ail. Collectively, these results suggest that fH recruitment is an additional mechanism of complement resistance of Ail. Recruitment of both fH and C4BP by Ail may confer Y. pseudotuberculosis with the ability to resist all pathways of complement activation. PMID:22956584
Ho, Derek K; Riva, Rauna; Skurnik, Mikael; Meri, Seppo
The complement cascade and cell-surface proteins related to the complement system are critically important to host defense, immune complex catabolism, and possibly immunoregulation. Genetically determined deficiency states have been described for many complement proteins as well as for fluid phase and cell-borne inhibitors of the complement cascade and cellular complement receptors. Autoimmune diseases and enhanced susceptibility to infection are the dominant clinical manifestation of these deficiencies. Classical pathway deficiencies and low numeric expression of erythrocyte C3b receptors (CR1) are typically associated with autoimmune disorders, while alternative pathway, terminal component, and leukocyte iC3b receptor (CR3) defects predispose to pyogenic bacterial disease. This distinction is not absolute, however, and both classes of disease may appear in most of the reported deficiency states. Specific pharmacologic therapy exists for C1-inhibitor deficiency (hereditary angioedema). Management of other complement deficiencies currently involves sustained diagnostic suspicion and meticulous management of complicating diseases. PMID:2941192
Fries, L F; O'Shea, J J; Frank, M M
Complement split products have emerged as useful markers of antibody mediated rejection in solid organ transplants. One split product, C4d, is now widely accepted as a marker for antibody mediated rejection in renal and cardiac allografts. This review summarizes the rationale for the use of C4d as a marker of antibody mediated rejection, along with the clinical evidence supporting its use in the clinical diagnosis of antibody mediated rejection. Antibody-independent mechanisms by which C4d can be activated by the classical and lectin pathways of complement activation are also identified. Finally, mechanisms by which complement activation stimulates effector cells (neutrophils, monocytes, macrophages, platelets, and B and T lymphocytes) as well as target cells (endothelial cells) are discussed in relation to antibody mediated allograft rejection.
Murata, Kazunori; Baldwin, William M
A study of the complement system in cardiosurgical patients with moderate (40 patients) and marked (18 patients) hemolysis after coronary artery bypass grafting in conditions of cardiopulmonary bypass was carried out. Before and after operation the content of D35+-, D55+-erythrocytes and reticulocytes in blood, free hemoglobin in blood plasma, indicators of the functional state of classical, lectin and alternative pathways of complement activation as well as concentration of its terminal complex in blood serum were analyzed. It was established that development of marked hemolysis was associated with higher (compared with moderate hemolysis) content of terminal complement complex and reticulocytes in blood before operation as well as deficiency of D55+- erythrocytes and low activity of alternative pathway. PMID:23548384
Chumakova, S P; Urazova, O I; Novitski?, V V; Shipulin, V M; Khokhlov, O A; Emel'ianova, T V; Mikha?lova, M A
Mannose-binding lectin (MBL) targets diverse microorganisms for phagocytosis and complement-mediated lysis by binding specific surface glycans. Although recombinant human MBL (rhMBL) trials have focused on reconstitution therapy, safety studies have ident...
C. Lear C. Scully C. B. Longley I. C. Michelow L. I. Prugar
Although the expression pattern and biological functions of ataxia-telangiectasia group D complementing gene (ATDC) had been implicated in several types of cancer, the roles and potential mechanisms of ATDC in lung cancer cell invasion are still ambiguous. In this study, we used gain- and loss-of-function analyses to explore the roles and potential mechanisms of ATDC in lung cancer cell invasion. siRNA knockdown of ATDC impaired cell invasion in A549 and H1299 cell lines, and its overexpression promoted cell invasion in HBE cell line. ATDC may contribute to the invasive ability of lung cancer cells by promoting the expression of invasion-related matrix metalloproteinase 9 (MMP-9). In addition, ATDC increased activating protein 1 (AP-1) reporter luciferase activity and the protein and mRNA levels of c-Jun and c-Fos. We further demonstrated that the roles of ATDC on cell invasion, MMP-9 upregulation, and AP-1 activation were dependent on extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) pathway activation, and ERK inhibitor U0126 or JNK inhibitor SP600125 blocked these effects of ATDC. These results suggested that ATDC upregulates MMP-9 to promote lung cancer cell invasion by activating ERK and JNK pathways. PMID:23681803
Tang, Zhong-Ping; Cui, Quan-Zhe; Dong, Qian-Ze; Xu, Ke; Wang, En-Hua
Neuromyelitis optica (NMO) is an autoimmune disorder with inflammatory demyelinating lesions in the central nervous system, particularly in the spinal cord and optic nerve. NMO pathogenesis is thought to involve binding of anti-aquaporin-4 (AQP4) autoantibodies to astrocytes, which causes complement-dependent cytotoxicity (CDC) and downstream inflammation leading to oligodendrocyte and neuronal injury. Vasculocentric deposition of activated complement is a prominent feature of NMO pathology. Here, we show that a neutralizing monoclonal antibody against the C1q protein in the classical complement pathway prevents AQP4 autoantibody-dependent CDC in cell cultures and NMO lesions in ex vivo spinal cord slice cultures and in mice. A monoclonal antibody against human C1q with 11 nM binding affinity prevented CDC caused by NMO patient serum in AQP4-transfected cells and primary astrocyte cultures, and prevented complement-dependent cell-mediated cytotoxicity (CDCC) produced by natural killer cells. The anti-C1q antibody prevented astrocyte damage and demyelination in mouse spinal cord slice cultures exposed to AQP4 autoantibody and human complement. In a mouse model of NMO produced by intracerebral injection of AQP4 autoantibody and human complement, the inflammatory demyelinating lesions were greatly reduced by intracerebral administration of the anti-C1q antibody. These results provide proof-of-concept for C1q-targeted monoclonal antibody therapy in NMO. Targeting of C1q inhibits the classical complement pathway directly and causes secondary inhibition of CDCC and the alternative complement pathway. As C1q-targeted therapy leaves the lectin complement activation pathway largely intact, its side-effect profile is predicted to differ from that of therapies targeting downstream complement proteins. PMID:23677375
Phuan, Puay-Wah; Zhang, Hua; Asavapanumas, Nithi; Leviten, Michael; Rosenthal, Arnon; Tradtrantip, Lukmanee; Verkman, A S
Microglia, the immune cell of the brain, are implicated in cascades leading to neuronal loss and cognitive decline in Alzheimer's disease (AD). Recent genome-wide association studies have indicated a number of risk factors for the development of late-onset AD. Two of these risk factors are an altered immune response and polymorphisms in complement receptor 1. In view of these findings, we discuss how complement signalling in the AD brain and microglial responses in AD intersect. Dysregulation of the complement cascade, either by changes in receptor expression, enhanced activation of different complement pathways or imbalances between complement factor production and complement cascade inhibitors may all contribute to the involvement of complement in AD. Altered complement signalling may reduce the ability of microglia to phagocytose apoptotic cells and clear amyloid beta peptides, modulate the expression by microglia of complement components and receptors, promote complement factor production by plaque-associated cytokines derived from activated microglia and astrocytes, and disrupt complement inhibitor production. The evidence presented here indicates that microglia in AD are influenced by complement factors to adopt protective or harmful phenotypes and the challenge ahead lies in understanding how this can be manipulated to therapeutic advantage to treat late onset AD.
Crehan, Helen; Hardy, John; Pocock, Jennifer
Interactions between spores of Bacillus anthracis and macrophages are critical for the development of anthrax infections, as spores are thought to utilize macrophages as vehicles to disseminate in the host. Here we report a novel mechanism for phagocytosis of B. anthracis spores. Murine macrophage-like cell line RAW264.7, bone marrow derived macrophages and primary peritoneal macrophages from mice were used. The results indicated that activation of the classical complement pathway (CCP) was a primary mechanism for spore phagocytosis. Phagocytosis was significantly reduced in the absence of C1q or C3. C3 fragments were found deposited on the spore surface and the deposition was dependent on C1q and Ca2+. C1q recruitment to the spore surface was mediated by the spore surface protein BclA, as recombinant BclA bound directly and specifically to C1q and inhibited C1q binding to spores in a dose-dependent manner. C1q binding to spores lacking BclA (?bclA) was also significantly reduced compared to wild type spores. In addition, deposition of both C3 and C4 as well as phagocytosis of spores were significantly reduced when BclA was absent but were not reduced in the absence of IgG, suggesting that BclA but not IgG is important in these processes. Taken together, these results support a model in which spores actively engage CCP primarily through BclA interaction with C1q, leading to CCP activation and opsonophagocytosis of spores in an IgG-independent manner. These findings are likely to have significant implications on B. anthracis pathogenesis and microbial manipulation of complement.
Gu, Chunfang; Jenkins, Sarah A.; Xue, Qiong; Xu, Yi
AN AUTOSOMAL DOMINANT GENE REGULATES THE EXTENT OF 9-O-ACETYLATION OF MURINE ERYTHROCYTE SIALIC ACIDS A Probable Explanation for the Variation in Capacity to Activate the Human Alternate Complement Pathway
Erythrocytes of some animal species are lysed by human serum as a result of activation of the alternate pathway of complement. This process may be modulated by the sialic acid content of the erythrocytes in the low levels of sialic acid favor lysis, whereas high levels of this sugar impede lysis (1-3). The sialic acid residues appear to function by
AJIT VARKI; STUART KORNFELD
Complement activation resulting in significant increases of C4a split product may be a marker of postexertional malaise in individuals with chronic fatigue syndrome (CFS). This study focused on identification of the transcriptional control that may contribute to the increased C4a in CFS subjects after exercise. We used quantitative reverse-transcription polymerase chain reaction to evaluate differential expression of genes in the classical and lectin pathways in peripheral blood mononuclear cells (PBMCs). Calibrated expression values were normalized to the internal reference gene peptidylpropyl isomerase B (PPIB), the external reference gene ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL), or the geometric mean (GM) of the genes ribosomal protein, large, P0 (RPLP0) and phosphoglycerate kinase 1 (PGK1). All nine genes tested, except mannose-binding lectin 2 (MBL2), were expressed in PBMCs. At 1 hour postexercise, C4, mannan-binding lectin serine protease 2 (MASP2) and ficolin 1 (FCN1) transcripts were detected at higher levels (? 2-fold) in at least 50% (4 of 8) of CFS subjects and were detected in 88% (7 of 8) CFS subjects when subjects with overexpression of either C4 or MASP2 were combined. Only an increase in the MASP2 transcript was statistically significant (PPIB, P = 0.001; GM, P = 0.047; rbcL, P = 0.045). This result may be due to the significant but transient downregulation of MASP2 in control subjects (PPIB, P = 0.023; rbcL, P = 0.027). By 6 hours postexercise, MASP2 expression was similar in both groups. In conclusion, lectin pathway responded to exercise differentially in CFS than in control subjects. MASP2 down-regulation may act as an antiinflammatory acute-phase response in healthy subjects, whereas its elevated level may account for increased C4a and inflammation-mediated postexertional malaise in CFS subjects.
Sorensen, Bristol; Jones, James F; Vernon, Suzanne D; Rajeevan, Mangalathu S
Herpesvirus saimiri is known to encode a homolog of human complement regulators named complement control protein homolog (CCPH). We have previously reported that this virally encoded inhibitor effectively inactivates complement by supporting factor I-mediated inactivation of complement proteins C3b and C4b (termed cofactor activity), as well as by accelerating the irreversible decay of the classical/lectin and alternative pathway C3 convertases (termed decay-accelerating activity). To fine map its functional sites, in the present study, we have generated a homology model of CCPH and performed substitution mutagenesis of its conserved residues. Functional analyses of 24 substitution mutants of CCPH indicated that (i) amino acids R118 and F144 play a critical role in imparting C3b and C4b cofactor activities, (ii) amino acids R35, K142, and K191 are required for efficient decay of the C3 convertases, (iii) positively charged amino acids of the linker regions, which are dubbed to be critical for functioning in other complement regulators, are not crucial for its function, and (iv) S100K and G110D mutations substantially enhance its decay-accelerating activities without affecting the cofactor activities. Overall, our data point out that ionic interactions form a major component of the binding interface between CCPH and its interacting partners.
Reza, Malik Johid; Kamble, Ashish; Ahmad, Muzammil; Krishnasastry, Musti V.
Mannose-binding lectin (MBL) is an innate immune system pattern recognition protein that kills a wide range of pathogenic microbes through complement activation. A substantial proportion of all human populations studied to date have MBL deficiency due to MBL2 polymorphisms, which potentially increases susceptibility to infectious disease. MBL binds numerous respiratory pathogens but the capsule of Streptococcus pneumoniae abrogates its efficient
Damon P. Eisen
Mannan-binding lectin (MBL) constitutes an important part of the innate immune defence by effecting the deposition of complement on microbial surfaces. MBL deficiency is among the most common primary immunodeficiencies and is associated with recurrent infections and symptoms of poor immune complex clearance. Plasma-derived MBL has been used in reconstitution therapy but concerns over viral contamination and production capacity point
Thomas Vorup-Jensen; Esben S. Sørensen; Uffe B. Jensen; Wilhelm Schwaeble; Toshisuke Kawasaki; Yong Ma; Kazuhide Uemura; Nobutaka Wakamiya; Yasuhiko Suzuki; Thomas G. Jensen; Kazue Takahashi; R. Alan B. Ezekowitz; Steffen Thiel; Jens Chr. Jensenius
Generation of the alternative pathway C3-convertase, the central amplification enzyme of the complement cascade, initiates by the binding of factor B (fB) to C3b to form the proconvertase, C3bB. C3bB is subsequently cleaved by factor D (fD) at a single site in fB, producing Ba and Bb fragments. Ba dissociates from the complex, while Bb remains bound to C3b, forming the active alternative pathway convertase, C3bBb. Using single-particle electron microscopy we have determined the 3-dimensional structures of the C3bB and the C3bBb complexes at ?27? resolution. The C3bB structure shows that fB undergoes a dramatic conformational change upon binding to C3b. However, the C3b-bound fB structure was easily interpreted after independently fitting the atomic structures of the isolated Bb and Ba fragments. Interestingly, the divalent cation-binding site in the von Willebrand type A domain in Bb faces the C345C domain of C3b, whereas the serine-protease domain of Bb points outwards. The structure also shows that the Ba fragment interacts with C3b separately from Bb at the level of the ??NT and CUB domains. Within this conformation, the long and flexible linker between Bb and Ba is likely exposed and accessible for cleavage by fD to form the active convertase, C3bBb. The architecture of the C3bB and C3bBb complexes reveals that C3b could promote cleavage and activation of fB by actively displacing the Ba domain from the von Willebrand type A domain in free fB. These structures provide a structural basis to understand fundamental aspects of the activation and regulation of the alternative pathway C3-convertase.
Torreira, Eva; Tortajada, Agustin; Montes, Tamara; de Cordoba, Santiago Rodriguez; Llorca, Oscar
Studies on ß-galactosidase a-complementation are reviewed. The isolation and structure of two ß-galactosidase fragments that form an enzymically active complex are described. One of these is a cyanogen bromide peptide from whole ß-galactosidase; the other is a dimeric-protein from a lacZ deletion mutant of Escherichia coli. The mechanism most likely involves an initial binding of two cyanogen bromide peptides to
Lectins are proteins that bind to sugars with varying specificities and several have been identified that show differential binding to structurally variable glycans attached to glycoproteins. Consequently, lectin affinity chromatography represents a valuable tool for glycoproteome studies, allowing enrichment of glycoproteins in samples prior to their identification by mass spectrometry (MS). From the perspective of plant scientists, lectin enrichment has proven useful for studies of the proteomes of the secretory pathways and cell wall, due to the high proportion of constituent proteins that are glycosylated. This chapter outlines a strategy to generate samples enriched with glycoproteins from bulk plant tissues prior to further characterization by MS, or other techniques. PMID:24136552
Ruiz-May, Eliel; Catalá, Carmen; Rose, Jocelyn K C
In the current study we investigate the activation of blood complement on medical device silicone rubber and present a plasma polymerized vinyl pyrrolidone (ppVP) coating which strongly decreases surface-activation of the blood complement system. We show that uncoated silicone and polystyrene are both potent activators of the complement system, measured both as activated, deposited C3b and quantifying fluid-phase release of the cleavage fragment C3c. The ppVP coated silicone exhibits approximately 90% reduced complement activation compared to untreated silicone. Quartz crystal microbalance with dissipation (QCM-D) measurements show relatively strong adsorption of blood proteins including native C3 to the ppVP surface, indicating that reduction of complement activation on ppVP is neither a result of low protein adsorption nor lower direct C3-binding, and is therefore possibly a consequence of differences in the adsorbed protein layer composition. The alternative and classical complement pathways are barely detectable on ppVP while the lectin pathway through MBL/ficolin-2 deposition remains active on ppVP suggesting this pathway is responsible for the remaining subtle activation on the ppVP coated surface. The ppVP surface is furthermore characterized physically and chemically using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR), which indicates preservation of chemical functionality by the applied plasma process. Overall, the ppVP coating shows a potential for increasing complement-compatibility of blood-contacting devices. PMID:21453967
Andersen, Thomas E; Palarasah, Yaseelan; Skjødt, Mikkel-Ole; Ogaki, Ryosuke; Benter, Maike; Alei, Mojagan; Kolmos, Hans J; Koch, Claus; Kingshott, Peter
Objective Fragment Bb is an activator of the alternative pathway of the complement system. Recently, increased first trimester maternal plasma concentrations of this fragment were reported in patients destined to have a spontaneous preterm delivery before 34 weeks of gestation. The aim of this study was to determine whether the amniotic fluid (AF) concentrations of fragment Bb change with gestational age, spontaneous labor (term and preterm), and in the presence of intra-amniotic infection/ inflammation (IAI). Study design This cross-sectional study included patients in the following groups: 1) midtrimester (n=64); 2) term in spontaneous labor (n=70); 3) term not in labor (n=43); 4) spontaneous preterm labor (PTL) who delivered at term (n=76); 5) PTL without IAI who delivered preterm (n=73); 6) PTL with IAI (n=76); 7) prelabor rupture of the membranes (preterm PROM) without IAI (n=71); and 8) preterm PROM with IAI (n=71). Fragment Bb concentration in amniotic fluid was determined by an enzyme-linked immunoassay. Non-parametric statistics were used for analyses. Results 1) Fragment Bb was detected in all AF samples (n=544); 2) The median AF concentration of fragment Bb in patients at term not in labor was significantly higher than that of those in the mid-trimester [2.42 ?g/mL, interquartile range (IQR) 1.78-3.22 vs. 1.64 ?g/mL, IQR 1.06-3.49; p<0.001]; 3) Among patients with PTL, those with IAI had a higher median AF fragment Bb concentration than that of woman without IAI who delivered preterm (4.82 ?g/mL, IQR 3.32-6.08 vs. 3.67 ?g/mL, IQR 2.35-4.57; p<0.001) and than that of women with an episode of PTL who delivered at term (3.21 ?g/mL, IQR 2.39-4.16; p<0.001); 4) Similarly, among patients with preterm PROM, the median AF fragment Bb concentration was higher in individuals with IAI than in those without IAI (4.24 ?g/mL, IQR 2.58-5.79 vs. 2.79 ?g/mL, IQR 2.09-3.89; p<0.001). 5) Among patients at term, the median AF fragment Bb concentration did not differ between women with spontaneous labor and those without labor (term in labor: 2.47 ?g/mL, IQR 1.86-3.22; p=0.97). Conclusions 1) Fragment Bb, an activator of the alternative complement pathway, is a physiologic constituent of the amniotic fluid, and its concentration increases with advancing gestational age; 2) Amniotic fluid concentrations of fragment Bb are higher in pregnancies complicated with IAI; and 3) Labor at term is not associated with changes in the amniotic fluid concentrations of fragment Bb. These findings suggest a role for fragment Bb in the host immune response against IAI.
Vaisbuch, Edi; Romero, Roberto; Erez, Offer; Tovi, Shali Mazaki; Pedro, Kusanovic Juan; Soto, Eleazar; Gotsch, Francesca; Dong, Zhong; Chaiworapongsa, Tinnakorn; Kim, Sun Kwon; Mittal, Pooja; Pacora, Percy; Yeo, Lami; Hassan, Sonia S.
Based on the fact that oligosaccharides encode biological information, the biorecognition between lectinised drug delivery systems and glycosylated structures in the intestine can be exploited for improved peroral therapy. Basic research revealed that some lectins can mediate mucoadhesion, cytoadhesion, and cytoinvasion of drugs. Entering the vesicular pathway by receptor mediated endocytosis, part of the conjugated drug is accumulated within the
Franz Gabor; Elisabeth Bogner; Andrea Weissenboeck; Michael Wirth
Two lectins, Leaf Lectin I and Leaf Lectin II (LLI and LLII) were purified from the leaves of Sophora japonica. Like the Sophora seed lectin, LLI and LLII are tetrameric glycoproteins containing a single subunit with respect to size. The subunits of LLI (32 kilodaltons) and LLII (34 kilodaltons) are slightly larger than those of the seed lectin (29.5 kilodaltons). The three Sophora lectins display indistinguishable specificities, amino acid compositions, specific hemagglutinin activities, and extinction coefficients. Although very closely related to the seed lectin, the leaf and seed lectins are not immunologically identical and they differ in subunit molecular weights, carbohydrate content, and in the pH sensitivity of their hemagglutinin activities. N-terminal amino acid sequence analysis shows that although they are homologous proteins, the three Sophora lectins are products of distinct genes. Images Fig. 1 Fig. 2 Fig. 3
Hankins, Charles N.; Kindinger, Juanita; Shannon, Leland M.
Mannose-binding lectin (MBL) is a key soluble effector of the innate immune system that recognizes pathogen-specific surface glycans. Surprisingly, low-producing MBL genetic variants that may predispose children and immunocompromised individuals to infectious diseases are more common than would be expected in human populations. Since certain immune defense molecules, such as immunoglobulins, can be exploited by invasive pathogens, we hypothesized that MBL might also enhance infections in some circumstances. Consequently, the low and intermediate MBL levels commonly found in human populations might be the result of balancing selection. Using model infection systems with pseudotyped and authentic glycosylated viruses, we demonstrated that MBL indeed enhances infection of Ebola, Hendra, Nipah and West Nile viruses in low complement conditions. Mechanistic studies with Ebola virus (EBOV) glycoprotein pseudotyped lentiviruses confirmed that MBL binds to N-linked glycan epitopes on viral surfaces in a specific manner via the MBL carbohydrate recognition domain, which is necessary for enhanced infection. MBL mediates lipid-raft-dependent macropinocytosis of EBOV via a pathway that appears to require less actin or early endosomal processing compared with the filovirus canonical endocytic pathway. Using a validated RNA interference screen, we identified C1QBP (gC1qR) as a candidate surface receptor that mediates MBL-dependent enhancement of EBOV infection. We also identified dectin-2 (CLEC6A) as a potentially novel candidate attachment factor for EBOV. Our findings support the concept of an innate immune haplotype that represents critical interactions between MBL and complement component C4 genes and that may modify susceptibility or resistance to certain glycosylated pathogens. Therefore, higher levels of native or exogenous MBL could be deleterious in the setting of relative hypocomplementemia which can occur genetically or because of immunodepletion during active infections. Our findings confirm our hypothesis that the pressure of infectious diseases may have contributed in part to evolutionary selection of MBL mutant haplotypes.
Lear, Calli; Chen, Li; Yantosca, L. Michael; Scully, Corinne; Sarraju, Ashish; Sokolovska, Anna; Zariffard, M. Reza; Eisen, Damon P.; Mungall, Bruce A.; Kotton, Darrell N.; Omari, Amel; Huang, I-Chueh; Farzan, Michael; Takahashi, Kazue; Stuart, Lynda; Stahl, Gregory L.; Ezekowitz, Alan B.; Spear, Gregory T.; Olinger, Gene G.; Schmidt, Emmett V.; Michelow, Ian C.
Background The involvement of complement system in brain injury has been scarcely investigated. Here we document the pivotal role of mannose binding lectin (MBL), one of the recognition molecules of the lectin complement pathway, in brain ischemic injury. Methods and Results Focal cerebral ischemia was induced in mice (by permanent or transient middle cerebral artery occlusion) and rats (by 3-vessels occlusion). We first observed that MBL is deposited on ischemic vessels up to 48h after injury and that functional MBL/MASP2 complexes are increased. Next we demonstrated that: 1) MBL?/? mice are protected from both transient and permanent ischemic injury; 2) Polyman2, the newly synthesized mannosylated molecule selected for its binding to MBL, improves neurological deficits and infarct volume when given up to 24h after ischemia in mice; 3) anti-MBL-A antibody improves neurological deficits and infarct volume when given up to 18h after ischemia, as assessed following 28d in rats. Conclusions Our data show an important role for MBL in the pathogenesis of brain ischemic injury and provide a strong support to the concept that MBL inhibition may be a relevant therapeutic target in humans, one with a wide therapeutic window of application.
Orsini, Franca; Villa, Pia; Parrella, Sara; Zangari, Rosalia; Zanier, Elisa R.; Gesuete, Raffaella; Stravalaci, Matteo; Fumagalli, Stefano; Ottria, Roberta; Reina, Jose J.; Paladini, Alessandra; Micotti, Edoardo; Ribeiro-Viana, Renato; Rojo, Javier; Pavlov, Vasile I.; Stahl, Gregory L.; Bernardi, Anna; Gobbi, Marco; De Simoni, Maria-Grazia
Interactions of human immunodeficiency virus type 1 (HIV-1) with immature dendritic cells (DC) are believed to be multifactorial and involve binding to the CD4 antigen, DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), mannose binding C-type lectin receptors (MCLR), and heparan sulfate proteoglycans (HSPG). In this study we assessed the relative contributions of these previously defined virus attachment factors to HIV binding and accumulation in DC and the subsequent transfer of the bound virus particle to CD4+ T cells. Using competitive inhibitors of HIV-1 attachment to DC, we have identified the existence of DC-SIGN-, MCLR-, and HSPG-independent mechanism(s) of HIV attachment and internalization. Furthermore, virus particles bound by DC independently of CD4, DC-SIGN, MCLR, and HSPG are efficiently transmitted to T cells. Treatment of virus particles with the protease subtilisin or treatment of immature DC with trypsin significantly reduced virus binding, thus demonstrating the role of HIV envelope glycoprotein interactions with unidentified DC-surface factor(s). Finally, this DC-mediated virus binding and internalization are dependent on lipid rafts. We propose that pathways to HIV-1 attachment and uptake in DC exhibit functional redundancy; that is, they are made up of multiple independent activities that can, at least in part, compensate for one another.
Gummuluru, Suryaram; Rogel, Mark; Stamatatos, Leonidas; Emerman, Michael
The complement system plays a pivotal protective role in the innate immune response to many pathogens including Flaviviruses. Flavivirus NS1 is a secreted non-structural glycoprotein that accumulates in plasma to high levels and is displayed on the surface of infected cells but is absent from viral particles. Previous work has defined an immune evasion role of Flavivirus NS1 in limiting complement activation by forming a complex with C1s and C4 to promote cleavage of C4 to C4b. Here, we demonstrate a second mechanism, also involving C4 and its active fragment C4b, by which NS1 antagonizes complement activation. Dengue, West Nile or yellow fever virus NS1 directly associated with C4b binding protein (C4BP), a complement regulatory plasma protein that attenuates the classical and lectin pathways. Soluble NS1 recruited C4BP to inactivate C4b in solution and on the plasma membrane. Mapping studies revealed that the interaction sites of NS1 on C4BP partially overlap with the C4b binding sites. Together, these studies further define the immune evasion potential of NS1 in reducing the functional capacity of C4 in complement activation and control of Flavivirus infection.
Avirutnan, Panisadee; Hauhart, Richard E.; Somnuke, Pawit; Blom, Anna M.; Diamond, Michael S.; Atkinson, John P.
The innate immune system is evolutionarily ancient and biologically primitive. Historically, it was first identified as an element of the immune system that provides the first-line response to pathogens, and increasingly it is recognized for its central housekeeping role and its essential functions in tissue homeostasis, including coagulation and inflammation, among others. A pivotal link between the innate immune system and other functions is mannose-binding lectin (MBL), a pattern recognition molecule. Multiple studies have demonstrated that MBL deficiency increases susceptibility to infection, and the mechanisms associated with this susceptibility to infection include reduced opsonophagocytic killing and reduced activation of the lectin complement pathway. Results from our laboratory have demonstrated that MBL and MBL-associated serine protease (MASP)-1/3 together mediate coagulation factor-like activities, including thrombin-like activity. MBL and/or MASP-1/3-deficient hosts demonstrate in vivo evidence that MBL and MASP-1/3 are involved with hemostasis following injury. Staphylococcus aureus-infected MBL null mice developed disseminated intravascular coagulation, which was associated with elevated blood IL-6 levels (but not TNF-?) and systemic inflammatory responses. Infected MBL null mice also develop liver injury. These findings suggest that MBL deficiency may manifest as disseminated intravascular coagulation and organ failure with infection. Beginning from these observations, this review focuses on the interaction of innate immunity and other homeostatic systems, the derangement of which may lead to complications in infection and other inflammatory states.
It has been suggested that genetic variants in mannose binding lectin (MBL2) influence susceptibility and outcome of invasive pneumococcal disease. We assessed the influence of genetic variation in MBL2 on susceptibility, outcome and causative serotype of pneumococcal meningitis in a prospective nationwide cohort study including 299 white patients and 216 controls. We assessed functionality of the genetic polymorphisms by measuring levels of MBL, C3a, iC3b, C5a and sC5b-9 in cerebrospinal fluid. We also performed a meta-analysis of studies on MBL2 polymorphisms and susceptibility to invasive pneumococcal disease. The risk of contracting pneumococcal meningitis was substantially increased for white individuals homozygous with the defective MBL2 0/0 genotype (odds ratio [OR] 8.21, 95% confidence interval [CI] 1.05–64.1; p?=?0.017). CSF MBL levels were significantly lower in patients with the A/0 and 0/0 genotype compared to homozygotes for the wild-type alleles (A/A; p<0.001). CSF MBL levels were positively correlated with C3a and iC3b levels, indicating complement activation by the lectin pathway. The effect of MBL2 genetic variants on susceptibility remained robust in a meta-analysis including 5 studies with 287 patients (OR 2.33, 99% CI 1.39–3.90). We conclude that MBL2 polymorphisms influence CSF MBL levels and substantially increase the risk of pneumococcal meningitis.
Brouwer, Matthijs C.; Baas, Frank; van der Ende, Arie; van de Beek, Diederik
It has been suggested that genetic variants in mannose binding lectin (MBL2) influence susceptibility and outcome of invasive pneumococcal disease. We assessed the influence of genetic variation in MBL2 on susceptibility, outcome and causative serotype of pneumococcal meningitis in a prospective nationwide cohort study including 299 white patients and 216 controls. We assessed functionality of the genetic polymorphisms by measuring levels of MBL, C3a, iC3b, C5a and sC5b-9 in cerebrospinal fluid. We also performed a meta-analysis of studies on MBL2 polymorphisms and susceptibility to invasive pneumococcal disease. The risk of contracting pneumococcal meningitis was substantially increased for white individuals homozygous with the defective MBL2 0/0 genotype (odds ratio [OR] 8.21, 95% confidence interval [CI] 1.05-64.1; p?=?0.017). CSF MBL levels were significantly lower in patients with the A/0 and 0/0 genotype compared to homozygotes for the wild-type alleles (A/A; p<0.001). CSF MBL levels were positively correlated with C3a and iC3b levels, indicating complement activation by the lectin pathway. The effect of MBL2 genetic variants on susceptibility remained robust in a meta-analysis including 5 studies with 287 patients (OR 2.33, 99% CI 1.39-3.90). We conclude that MBL2 polymorphisms influence CSF MBL levels and substantially increase the risk of pneumococcal meningitis. PMID:23741476
Brouwer, Matthijs C; Baas, Frank; van der Ende, Arie; van de Beek, Diederik
Bauhinia purpurea lectin (BPA) is one of the beta-galactose-binding leguminous lectins. Leguminous lectins contain a long metal-binding loop, part of which determines their carbohydrate-binding specificities. Random mutations were introduced into a portion of the cDNA coding BPA that corresponds to the carbohydrate-binding loop of the lectin. An library of the mutant lectin expressed on the surface of lambda foo phages was screened by the panning method. Several phage clones with an affinity for mannose or N-acetylglucosamine were isolated. These results indicate the possibility of making artificial lectins (so-called "cyborg lectins") with distinct and desired carbohydrate-binding specificities. PMID:10731676
Yamamoto, K; Maruyama, I N; Osawa, T
Binding of mannose-binding lectin (MBL), a C-type lectin, and its associated serine proteases, MASP-1 and MASP-2, to cell surface carbohydrates activates the lectin complement pathway. As MBL plays an important role in innate immunity, it has been cloned and characterized in several species. While the pig may be used as a source of organs/tissues for xenotransplantation, little is known about its MBL, thus, we report the isolation of three monomeric forms of MBL from porcine serum. Sodium dodecyl sulphate–polyacrylamide gel electrophoresis and Coomassie staining of reduced porcine MBL revealed the presence of three monomeric forms with approximate molecular masses of 30 000, 32 000 and 34 000. Protein sequencing identified these monomeric forms as one single protein, suggesting post-translational modification. Western blot analysis demonstrated the cross-reactivity of anti-human MBL polyclonal antibody with porcine MBL. A full-length porcine liver MBL cDNA was isolated and the predicted amino acid sequence exhibited 64·9% identity with human MBL and 50·2% and 56·7% identity with rat A and C MBL, respectively. Furthermore, Northern blot analysis demonstrated the presence of a single (?1·4–1·6 kilobase pair) transcript in porcine liver. Addition of purified porcine MBL to MBL-deficient human sera augmented N-acetylglucosamine inhibitable C3 deposition to mannan-coated plates in a dose-dependent manner. Taken together, these data demonstrate that porcine and human MBL are highly conserved, sharing structural and functional characteristics.
Agah, A; Montalto, M C; Young, K; Stahl, G L
We have previously shown that pathogenic leptospiral strains are able to bind C4b binding protein (C4BP). Surface-bound C4BP retains its cofactor activity, indicating that acquisition of this complement regulator may contribute to leptospiral serum resistance. In the present study, the abilities of seven recombinant putative leptospiral outer membrane proteins to interact with C4BP were evaluated. The protein encoded by LIC11947 interacted with this human complement regulator in a dose-dependent manner. The cofactor activity of C4BP bound to immobilized recombinant LIC11947 (rLIC11947) was confirmed by detecting factor I-mediated cleavage of C4b. rLIC11947 was therefore named LcpA (for leptospiral complement regulator-acquiring protein A). LcpA was shown to be an outer membrane protein by using immunoelectron microscopy, cell surface proteolysis, and Triton X-114 fractionation. The gene coding for LcpA is conserved among pathogenic leptospiral strains. This is the first characterization of a Leptospira surface protein that binds to the human complement regulator C4BP in a manner that allows this important regulator to control complement system activation mediated either by the classical pathway or by the lectin pathway. This newly identified protein may play a role in immune evasion by Leptospira spp. and may therefore represent a target for the development of a human vaccine against leptospirosis.
Barbosa, Angela S.; Monaris, Denize; Silva, Ludmila B.; Morais, Zenaide M.; Vasconcellos, Silvio A.; Cianciarullo, Aurora M.; Isaac, Lourdes; Abreu, Patricia A. E.
Five N-acetyl-galactosamine-specific lectins were isolated from the bark of the legume tree Sophora japonica. These lectins are immunologically and structurally very similar, but not identical, to the Sophora seed and leaf lectins. The carbohydrate specificities and hemagglutinin activities of these lectins are indistinguishable at pH 8.5 but their activities differ markedly at pH values below 8. All five lectins are tetrameric glycoproteins made up of different combinations of subunits of about 30,000, 30,100, 33,000 Mr containing 3% to 5% covalently attached sugar. These lectins are the overwhelmingly dominant proteins in bark, but they do not appear to be present in other tissues. Amino terminal sequence analysis indicates that at least two distinct lectin genes are expressed in bark. Images Fig. 1 Fig. 3
Hankins, Charles N.; Kindinger, J. I.; Shannon, L. M.
Isolates of Campylobacter jejuni, C coli, C fetus and C laridis were tested for agglutination reactions with a panel of five lectins: Arachis hypogaea, Bauhinia purpurea, Solanum tuberosum, Triticum vulgaris and Wisteria floribunda. Twenty three patterns of agglutination (lectin types) were recorded among 376 isolates. Patterns were consistent and reproducible. Only 4.5% of isolates were untypable because of autoagglutination. Some lectin types were found exclusively or predominantly in a species, but others were shared between species. Forty two per cent of C jejuni and 35% of C coli isolates belonged to lectin type 4. There was no apparent correlation between lectin type and serotype; different lectin types were found among strains of single Penner and Lior serotypes. Lectin typing is a simple and economical procedure suitable for use in non-specialist laboratories, either as an adjunct to serogrouping or, after further development, as a sole typing scheme.
O'Sullivan, N; Benjamin, J; Skirrow, M B
Plant lectins, a group of highly diverse carbohydrate-binding proteins of non-immune origin, are ubiquitously distributed through a variety of plant species, and have recently drawn rising attention due to their remarkable ability to kill tumour cells using mechanisms implicated in autophagy. In this review, we provide a brief outline of structures of some representative plant lectins such as concanavalin A, Polygonatum cyrtonema lectin and mistletoe lectins. These can target autophagy by modulating BNIP-3, ROS-p38-p53, Ras-Raf and PI3KCI-Akt pathways, as well as Beclin-1, in many types of cancer cells. In addition, we further discuss how plant lectins are able to kill cancer cells by modulating autophagic death, for therapeutic purposes. Together, these findings provide a comprehensive perspective concerning plant lectins as promising new anti-tumour drugs, with respect to autophagic cell death in future cancer therapeutics. PMID:24033443
Liu, Z; Luo, Y; Zhou, T-T; Zhang, W-Z
The capacity for fixation and activation of hemolytic complement by polyclonal IgM rheumatoid factors (RF) isolated from sera of patients with rheumatoid arthritis and monoclonal IgM-RF isolated from the cryoprecipitates of patients with IgM-IgG mixed cryoglobulinemia was examined. RF mixed with aggregated, reduced, and alkylated human IgG (Agg-R/A-IgG) in the fluid phase failed to significantly reduce the level of total hemolytic complement, CH50, or of individual complement components, C1, C2, C3, and C5. However, sheep erythrocytes (SRC) coated with Agg-R/A-IgG or with reduced and alkylated rabbit IgG anti-SRC antibody were hemolyzed by complement in the presence of polyclonal IgM-RF. Human and guinea pig complement worked equally well. The degree of hemolysis was in direct proportion to the hemagglutination titer of the RF against the same coated cells. Monoclonal IgM-RF, normal human IgM, and purified Waldenström macroglobulins without antiglobulin activity were all inert. Hemolysis of coated SRC by RF and complement was inhibited by prior treatment of the complement source with chelating agents, hydrazine, cobra venom factor, specific antisera to C1q, CR, C5, C6, or C8, or by heating at 56 degrees C for 30 min. Purified radiolabeled C4, C3, and C8 included in the complement source were bound to hemolysed SRC in direct proportion to the degree of hemolysis. These data indicate that polyclonal IgM-RF fix and activate complement via the classic pathway. The system described for assessing complement fixation by isolated RF is readily adaptable to use with whole human serum.
Tanimoto, K; Cooper, N R; Johnson, J S; Vaughan, J H
Complement receptors (CR), along with Fc receptors, play a primary role in the removal of bacterial pathogens in poultry. The binding of serum-opsonized bacteria to CR results in the secretion of both toxic oxygen metabolites and anti-bacterial granules. We have previously shown that the stimulati...
In-depth analysis of the salivary proteome is fundamental to understanding the functions of salivary proteins in the oral cavity and to reveal disease biomarkers involved in different pathophysiological conditions, with the ultimate goal of improving patient diagnosis and prognosis. Submandibular and sublingual glands contribute saliva rich in glycoproteins to the total saliva output, making them valuable sources for glycoproteomic analysis. Lectin-affinity chromatography coupled to mass spectrometry-based shotgun proteomics was used to explore the submandibular/sublingual (SM/SL) saliva glycoproteome. A total of 262 N- and O-linked glycoproteins were identified by multidimensional protein identification technology (MudPIT). Only 38 were previously described in SM and SL salivas from the human salivary N-linked glycoproteome, while 224 were unique. Further comparison analysis with SM/SL saliva of the human saliva proteome, revealed 125 glycoproteins not formerly reported in this secretion. KEGG pathway analyses demonstrated that many of these glycoproteins are involved in processes such as complement and coagulation cascades, cell communication, glycosphingolipid biosynthesis neo-lactoseries, O-glycan biosynthesis, glycan structures-biosynthesis 2, starch and sucrose metabolism, peptidoglycan biosynthesis or others pathways. In summary, lectin-affinity chromatography coupled to MudPIT mass spectrometry identified many novel glycoproteins in SM/SL saliva. These new additions to the salivary proteome may prove to be a critical step for providing reliable biomarkers in the diagnosis of a myriad of oral and systemic diseases.
Gonzalez-Begne, Mireya; Lu, Bingwen; Liao, Lujian; Xu, Tao; Bedi, Gurrinder; Melvin, James E.; Yates, John R.
C-type lectin receptors (CLRs) expressed by dendritic cells are crucial for tailoring immune responses to pathogens. Following pathogen binding, CLRs trigger distinct signalling pathways that induce the expression of specific cytokines which determine T cell polarization fates. Some CLRs can induce signalling pathways that directly activate nuclear factor-?B, whereas other CLRs affect signalling by Toll-like receptors. Dissecting these signalling pathways
Sonja I. Gringhuis; Teunis B. H. Geijtenbeek
Complement receptors (CRs), along with Fc receptors, play a primary role in the removal of bacterial pathogens in poultry. The binding of serum-opsonized bacteria to CR results in the secretion of both toxic oxygen metabolites and antibacterial granules. We have previously shown that the stimulation of chicken heterophils with serum-opsonized Salmonella enteritidis induced tyrosine kinase-dependent phosphorylation regulated degranulation. In the
Michael H. Kogut; Virginia K. Lowry; Morgan Farnell
The concept of elicitation of reactions of anaphylactic type by non-tissue-fixing antibody, through activation of complement and release of anaphylatoxins by antigen-antibody complexes in vivo, is not clearly defined by published evidence. Experimental data are presented to demonstrate that guinea pig immunoglobulin G2 (noncytotropic) complexed with antigen in vitro elicits dermal reactions in guinea pigs, and that pretreatment of animals with complement-inactivating cobra venom factor diminishes such reactions. The various pathways through which immediate hypersensitive reactions may occur are discussed.
Tom, B. H.; Raffel, S.
Plasminogen is a 92-kDa single chain glycoprotein that circulates in plasma as a zymogen and when converted to proteolytically active plasmin dissolves preformed fibrin clots and extracellular matrix components. Here, we characterize the role of plasmin(ogen) in the complement cascade. Plasminogen binds the central complement protein C3, the C3 cleavage products C3b and C3d, and C5. Plasminogen binds to C3, C3b, C3d, and C5 via lysine residues, and the interaction is ionic strength-dependent. Plasminogen and Factor H bind C3b; however, the two proteins bind to different sites and do not compete for binding. Plasminogen affects complement action in multiple ways. Plasminogen enhanced Factor I-mediated C3b degradation in the presence of the cofactor Factor H. Plasminogen when activated to plasmin inhibited complement as demonstrated by hemolytic assays using either rabbit or sheep erythrocytes. Similarly, plasmin either in the fluid phase or attached to surfaces inhibited complement that was activated via the alternative and classical pathways and cleaved C3b to fragments of 68, 40, 30, and 17 kDa. The C3b fragments generated by plasmin differ in size from those generated by the complement protease Factor I, suggesting that plasmin-mediated C3b cleavage fragments lack effector function. Plasmin also cleaved C5 to products of 65, 50, 30, and 25 kDa. Thus, plasmin(ogen) regulates both complement and coagulation, the two central cascade systems of a vertebrate organism. This complement-inhibitory activity of plasmin provides a new explanation why pathogenic microbes utilize plasmin(ogen) for immune evasion and tissue penetration.
Barthel, Diana; Schindler, Susann; Zipfel, Peter F.
Understanding innate immunity is key to improving the safety of adenovirus (Ad) vectors for systemic gene therapy. Ad has been shown to activate complement in vitro, but activation of complement after Ad injection in vivo has not been directly measured. Using complement protein C3a as a marker of complement activation, we show that types 2 and 5 human Ads cause rapid complement activation after intravenous injection in mice. Unexpectedly, the mechanisms in vivo were different than those in vitro. Antibodies were critical for the activation of complement by Ad in vitro, but antibodies were not required in vivo. The classical pathway was required in vitro, whereas complement activation in vivo involved both classical and nonclassical pathways as well as the reticuloendothelial system. Remarkably, the entry-deficient Ad mutant ts1 was completely unable to activate complement in vivo even though it was fully able to activate complement in vitro. This result demonstrates that the complement system senses intravenously injected Ad primarily by detecting the effects of Ad on cells rather than through direct interaction of complement with virions. Encouragingly, shielding Ad with polyethylene glycol was effective at reducing complement activation both in vitro and in vivo. In summary, intravenously injected Ad rapidly activates complement through multiple pathways, but these pathways are different than those identified by in vitro studies. In vitro studies are poorly predictive of in vivo mechanisms because Ad virions activate complement through indirect mechanisms in vivo. PMID:19321608
Tian, Jie; Xu, Zhili; Smith, Jeffrey S; Hofherr, Sean E; Barry, Michael A; Byrnes, Andrew P
Colorectal cancer (CRC) remains a major worldwide cause of cancer-related morbidity and mortality largely due to the insidious onset of the disease. The current clinical procedures utilized for disease diagnosis are invasive, unpleasant, and inconvenient; hence, the need for simple blood tests that could be used for the early detection of CRC. In this work, we have developed methods for glycoproteomics analysis to identify plasma markers with utility to assist in the detection of colorectal cancer (CRC). Following immunodepletion of the most abundant plasma proteins, the plasma N-linked glycoproteins were enriched using lectin affinity chromatography and subsequently further separated by nonporous silica reverse-phase (NPS-RP)-HPLC. Individual RP-HPLC fractions were printed on nitrocellulose coated slides which were then probed with lectins to determine glycan patterns in plasma samples from 9 normal, 5 adenoma, and 6 colorectal cancer patients. Statistical tools, including principal components analysis, hierarchical clustering, and Z-statistic analysis, were employed to identify distinctive glycosylation patterns. Patients diagnosed with colorectal cancer or adenomas were shown to have dramatically higher levels of sialylation and fucosylation as compared to normal controls. Plasma glycoproteins with aberrant glycosylation were identified by nano-LC–MS/MS, while a lectin blotting methodology was used to validate proteins with significantly altered glycosylation as a function of cancer progression. The potential markers identified in this study for diagnosis to distinguish colorectal cancer from adenoma and normal include elevated sialylation and fucosylation in complement C3, histidine-rich glycoprotein, and kininogen-1. These potential markers of colorectal cancer were subsequently validated by lectin blotting in an independent set of plasma samples obtained from 10 CRC patients, 10 patients with adenomas, and 10 normal subjects. These results demonstrate the utility of this strategy for the identification of N-linked glycan patterns as potential markers of CRC in human plasma, and may have the utility to distinguish different disease states.
Qiu, Yinghua; Patwa, Tasneem H.; Xu, Li; Shedden, Kerby; Misek, David E.; Tuck, Missy; Jin, Gracie; Ruffin, Mack T.; Turgeon, Danielle K.; Synal, Sapna; Bresalier, Robert; Marcon, Norman; Brenner, Dean E.; Lubman, David M.
Molecular recognition can be mediated by protein (lectin)-carbohydrate interaction, explaining the interest in this topic. Plant lectins and, more recently, chemically glycosylated neoglycoproteins principally allow to map the occurrence of components of this putative recognition system. Labelled endogenous lectins and the lectin-binding ligands can add to the panel of glycohistochemical tools. They may be helpful to derive physicologically valid conclusions
H.-J. Gabius; B. Wosgien; M. Hendrys; A. Bardosi
Isolates of Campylobacter jejuni, C coli, C fetus and C laridis were tested for agglutination reactions with a panel of five lectins: Arachis hypogaea, Bauhinia purpurea, Solanum tuberosum, Triticum vulgaris and Wisteria floribunda. Twenty three patterns of agglutination (lectin types) were recorded among 376 isolates. Patterns were consistent and reproducible. Only 4.5% of isolates were untypable because of autoagglutination. Some
N OSullivan; J Benjamin; M B Skirrow
The complement system consists of both plasma and membrane proteins. The former influence the inflammatory response, immune modulation, and host defense. The latter are complement receptors, which mediate the cellular effects of complement activation, and regulatory proteins, which protect host cells from complement-mediated injury. Complement activation occurs via either the classical or the alternative pathway, which converge at the level of C3 and share a sequence of terminal components. Four aspects of the complement cascade are critical to its function and regulation: (i) activation of the classical pathway, (ii) activation of the alternative pathway, (iii) C3 convertase formation and C3 deposition, and (iv) membrane attack complex assembly and insertion. In general, mechanisms evolved by pathogenic microbes to resist the effects of complement are targeted to these four steps. Because individual complement proteins subserve unique functional activities and are activated in a sequential manner, complement deficiency states are associated with predictable defects in complement-dependent functions. These deficiency states can be grouped by which of the above four mechanisms they disrupt. They are distinguished by unique epidemiologic, clinical, and microbiologic features and are most prevalent in patients with certain rheumatologic and infectious diseases. Ethnic background and the incidence of infection are important cofactors determining this prevalence. Although complement undoubtedly plays a role in host defense against many microbial pathogens, it appears most important in protection against encapsulated bacteria, especially Neisseria meningitidis but also Streptococcus pneumoniae, Haemophilus influenzae, and, to a lesser extent, Neisseria gonorrhoeae. The availability of effective polysaccharide vaccines and antibiotics provides an immunologic and chemotherapeutic rationale for preventing and treating infection in patients with these deficiencies.
Figueroa, J E; Densen, P
Summary The interactions between dietary kidney bean (Phaseolus vulgaris) lectins and the epithelial cells of the rat small intestine were investigated by immunogold electron microscopy. The results demonstrated that the lectins bind to the glycocalyx of duodenal and jejunal microvilli and that some of these dietary constituents are endocytosed into lysosomal pathways within both absorptive and secretory gut cells. It is
T. P. King; A. Pusztai; G. Grant; D. Slater
Fungal infections are an emerging threat for human health. A coordinated host immune response is fundamental for successful elimination of an invading fungal microbe. A panel of C-type lectin receptors expressed on antigen-presenting dendritic cells enable innate recognition of fungal cell wall carbohydrates and tailors adaptive responses via the instruction of CD4? T helper cell fates. Well-balanced T helper cell type 1 and IL-17-producing T helper cell responses are crucial in antifungal immunity and facilitate phagocytic clearance of fungal encounters. Strikingly, different classes of fungi trigger distinct sets of C-type lectin receptors to evoke a pathogen-specific T helper response. In this review, we outline the key roles of several C-type lectin receptors during the generation of protective antifungal immunity, with particular emphasis on the distinct signaling pathways and transcriptional programs triggered by these receptors, which collaborate to orchestrate polarization of the T helper response. PMID:23841632
Wevers, Brigitte A; Geijtenbeek, Teunis B H; Gringhuis, Sonja I
The sea lamprey (Petromyzon marinus) is a parasitic cartilaginous fish of the North American Great Lakes and a predator of many bony fish species of commercial importance to the fishing industry. Mannose-binding C-type lectin (MBL) was isolated by mannan-agarose affinity chromatography from sea lamprey plasma. Mannose-binding lectin has not before been identified and quantitated in the plasma of this sea lamprey species. The affinity-purified and 2-ME reduced lamprey MBL showed two bands of 35kDa and 65kDa by SDS-PAGE and Western blotting using guinea pig anti-MBL IgG as the primary antibody. Amino acid composition analysis (mol%) of the purified lamprey MBL found high amounts of histidine, threonine, tyrosine and phenylalanine present when compared with three other vertebrate MBLs. N-terminal amino acid sequencing by Edman degradation for the first 10 residues gave XXXTKGCPDA. Lamprey plasma contained 261mug of MBL/ml of plasma. Plasma protein concentration was 40.1mg/ml. Lamprey MBL was present then in plasma at 6.5mug MBL/mg total protein. The sea lamprey MBL also specifically binds to mannose on the surface of the pathogen Aeromonas salmonicida. The presence of MBL in high concentration in lamprey plasma could be important in their innate immunity and resistance to infection. This study describes the presence of MBL in sea lamprey plasma and evidence for a C-type lectin complement pathway of innate immunity. PMID:18937980
Ourth, Donald D; Rose, Wendy M; Siefkes, Michael J
Two glucose-negative Escherichia coli mutants (ZSC113 and DF214) were unable to grow on glucose as the sole carbon source unless supplemented with pyrroloquinoline quinone (PQQ). PQQ is the cofactor for the periplasmic enzyme glucose dehydrogenase, which converts glucose to gluconate. Aerobically, E. coli ZSC113 grew on glucose plus PQQ with a generation time of 65 min, a generation time about the same as that for wild-type E. coli in a defined glucose-salts medium. Thus, for E. coli ZSC113 the Enter-Doudoroff pathway was fully able to replace the Embden-Meyerhof-Parnas pathway. In the presence of 5% sodium dodecyl sulfate, PQQ no longer acted as a growth factor. Sodium dodecyl sulfate inhibited the formation of gluconate from glucose but not gluconate metabolism. Adaptation to PQQ-dependent growth exhibited long lag periods, except under low-phosphate conditions, in which the PhoE porin would be expressed. We suggest that E. coli has maintained the apoenzyme for glucose dehydrogenase and the Entner-Doudoroff pathway as adaptations to an aerobic, low-phosphate, and low-detergent aquatic environment. PMID:1654044
Adamowicz, M; Conway, T; Nickerson, K W
Two glucose-negative Escherichia coli mutants (ZSC113 and DF214) were unable to grow on glucose as the sole carbon source unless supplemented with pyrroloquinoline quinone (PQQ). PQQ is the cofactor for the periplasmic enzyme glucose dehydrogenase, which converts glucose to gluconate. Aerobically, E. Coli ZSC113 grew on glucose plus PQQ with a generation time of 65 min, a generation time about the same as that for wild-type E. coli in a defined glucose-salts medium. Thus, for E. coli ZSC113 the Entner-Doudoroff pathway was fully able to replace the Embden-Meyerhof-Parnas pathway. In the presence of 5% sodium dodecyl sulfate, PQQ no longer acted as a growth factor. Sodium dodecyl sulfate inhibited the formation of gluconate from glucose but not gluconate metabolism. Adaptation to PQQ-dependent growth exhibited long lag periods, except under low-phosphate conditions, in which the PhoE porin would be expressed. The authors suggest that E. coli has maintained the apoenzyme for glucose dehydrogenase and the Entner-Doudoroff pathway as adaptations to an aerobic, low-phosphate, and low-detergent aquatic environment.
Adamowicz, M.; Conway, T.; Nickerson, K.W. (Univ. of Nebraska, Lincoln (USA))
The role of complement activation in mediating cell adhesion at polymer blood contact surfaces was investigated, focusing on (a) determination of the extent and time dependence of complement activation by polymers in contact with whole canine serum, and (...
G. A. Herzlinger R. D. Cumming
Pathogen recognition by dendritic cells (DCs) is central to the induction of adaptive immunity. Pattern recognition receptors (PRRs) on DCs interact with pathogens, leading to signaling events that dictate adaptive immune responses. It is becoming clear that C-type lectins are important PRRs that recognize carbohydrate structures. Most pathogens express carbohydrate structures on their surface and these function as a so-called sugar fingerprint that are recognized by specific C-type lectins. Triggering of C-type lectin induces signaling cascades that initiate or modulate specific cytokine responses and therefore tailor T cell polarization to the pathogens. Here we will discuss our current understanding of the innate signaling pathways induced by C-type lectins DC-SIGN and dectin-1 in humans and how these pathways shape adaptive immunity. PMID:19808055
den Dunnen, Jeroen; Gringhuis, Sonja I; Geijtenbeek, Teunis B H
Age-related macular degeneration (AMD) is a common degenerative disease resulting in injury to the retina, retinal pigment epithelium and choriocapillaris. Recent data from histopathology, animal models and genetic studies have implicated altered regulation of the complement system as a major factor in the incidence and progression of this disease. A variant in the gene SERPING1, which encodes C1INH, an inhibitor of the classical and lectin pathways of complement activation, was recently shown to be associated with AMD. In this study we sought to determine the localization of C1INH in human donor eyes. Immunofluorescence studies using a monoclonal antibody directed against C1INH revealed localization to photoreceptor cells, inner nuclear layer neurons, choriocapillaris, and choroidal extracellular matrix. Drusen did not exhibit labeling. Genotype at rs2511989 did not appear to affect C1INH abundance or localization, nor was it associated with significant molecular weight differences when evaluated by Western blot. In a small number of eyes (n=7 AMD and n=7 control) AMD affection status was correlated with increased abundance of choroidal C1INH. These results indicate that C1INH protein is present in the retina and choroid, where it may regulate complement activation.
Mullins, Robert F.; Faidley, Elizabeth A.; Daggett, Heather T.; Jomary, Catherine; Lotery, Andrew J.; Stone, Edwin M.
To determine whether complement is activated in uveitis we have measured plasma levels of C3d, a sensitive indicator of complement activation. Increased levels of C3d were found in 11 of 15 patients with idiopathic uveitis, 13 of whom had circulating immune complexes containing complement components. Since during complement activation potent mediators of inflammation are generated, it is suggested that the activation of complement, possibly triggered by uveal deposition of immune complexes, has an important role in the pathogenesis of uveitis.
Vergani, S.; Di Mauro, E.; Davies, E. T.; Spinelli, D.; Mieli-Vergani, G.; Vergani, D.
Response gene to complement 32 (RGC32) is a novel cellular protein that has been reported to be expressed aberrantly in multiple types of human tumors. However, the role of RGC32 in cancer is still controversial, and the molecular mechanisms by which RGC32 contributes to the development of cancer remain largely unknown. In the present study, we constructed a recombinant expression vector pCDNA3.1-RGC32 and transfected it into human lung cancer A549 cells. Stable transformanted cells were identified by real-time PCR and Western blot analysis. Functional analysis showed that forced overexpression of RGC32 increased invasive and migration capacities of lung cancer cells in vitro, and induced the acquisition of epithelial-mesenchymal transition (EMT) phenotype, as demonstrated by the spindle-like morphology, downregulation of E-cadherin, and upregulation of Vimentin, Fibronectin, Snail and Slug. Also, overexpression of RGC32 increased expression and activities of matrix metalloproteinase (MMP)-2 and MMP-9 in A549 cells. Furthermore, the downregulation of E-cadherin induced by RGC32 was remarkably attenuated by nuclear factor-?B (NF-?B) inhibitor BAY 11-7028 and small interfering RNA targeting NF-?B p65, suggesting a role of the NF-?B signaling pathway in RGC32-induced EMT. Taken together, our data suggest that RGC32 promotes cell migration and invasion and induces EMT in lung cancer cells via the NF-?B signaling pathway. PMID:23715780
Sun, Qinying; Yao, Xiaopeng; Ning, Yunye; Zhang, Wei; Zhou, Guowu; Dong, Yuchao
Effective immune responses depend on the recognition of pathogens by dendritic cells (DCs) through pattern recognition receptors\\u000a (PRRs). These receptors induce specific signaling pathways that lead to the induction of immune responses against the pathogens.\\u000a It is becoming evident that C-type lectins are also important PRRs. In particular, the C-type lectin DC-SIGN has emerged as\\u000a a key player in the
Jeroen den Dunnen; Sonja I. Gringhuis; Teunis B. H. Geijtenbeek
The complement system is a component of the innate immune system. Its main function was initially believed to be limited to the recognition and elimination of pathogens through direct killing or stimulation of phagocytosis. However, in recent years, the immunoregulatory functions of the complement system were demonstrated and it was determined that the complement proteins play an important role in modulating adaptive immunity and in bridging innate and adaptive responses. When the delicate mechanisms that regulate this sophisticated enzymatic system are unbalanced, the complement system may cause damage, mediating tissue inflammation. Dysregulation of the complement system has been involved in the pathogenesis and clinical manifestations of several autoimmune diseases, such as systemic lupus erythematosus, vasculitides, Sjögren's syndrome, antiphospholipid syndrome, systemic sclerosis, dermatomyositis, and rheumatoid arthritis. Complement deficiencies have been associated with an increased risk to develop autoimmune disorders. Because of its functions, the complement system is an attractive therapeutic target for a wide range of diseases. Up to date, several compounds interfering with the complement cascade have been studied in experimental models for autoimmune diseases. The main therapeutic strategies are inhibition of complement activation components, inhibition of complement receptors, and inhibition of membrane attack complex. At present, none of the available agents was proven to be both safe and effective for treatment of autoimmune diseases in humans. Nonetheless, data from preclinical studies and initial clinical trials suggest that the modulation of the complement system could constitute a viable strategy for the treatment of autoimmune conditions in the decades to come. PMID:23615835
Ballanti, Eleonora; Perricone, Carlo; Greco, Elisabetta; Ballanti, Marta; Di Muzio, Gioia; Chimenti, Maria Sole; Perricone, Roberto
The reaction of [14C]methylamine with native human C3 led to the stoichiometric incorporation of methylamine, loss of hemolytic activity, and the concomitant exposure of a sulfhydryl group that could be labeled with [14C]iodoacetamide. Both labeled sites were located in the C3d portion of the alpha-chain, which is known to contain the metastable binding of C3b. The methylamine-modified C3 [C3(CH3NH2)] was shown to exhibit many of the functional properties of C3b, although the C3a portion of the molecule remained covalently attached. C3(CH3NH2) bound Factor B and beta 1H, and could be cleaved by C3b inactivator in the presence of beta 1H. C3(CH3NH2) added to human serum caused activation of the alternative pathway and consumption of C3. In presence of Factors B and D and Mg++, C3(CH2NH2) formed a C3 convertase. The convertase-forming material could be removed from solution by anti-C3a Sepharose and the preformed convertase was completely inhibited by purified antibody to C3a. This antibody did not affect the function of the C3 convertase that contained C3b. Similar functional properties were exhibited by C3 exposed for short periods of time to relatively low concentrations of chaotropic reagents, such as KSCN or guanidine. These results suggest that the initial C3 convertase of the alternative pathway may be formed from native C3, without proteolysis, by the attack of a variety of nucleophiles including water. The C3 convertase formed from this altered C3 then generates by proteolytic cleavage the initial metastable C3b that is capable of attaching to receptive surfaces. Conversion of C3 to C3b exposes one sulfhydryl residue as does modification of C3 with methylamine. When the C3d portion of C3b bound to zymosan particles via the metastable binding site was treated with radiolabeled methylamine, the fragment was released from the particles in radiolabeled form. These findings are consistent with the concept that native C3 contains an active carbonyl group, probably in the form of a thioester, which can either react with water to form functionally C3b-l;ike C3 or, upon enzymatic conversion of C3 to C3b, allows C3b to form an ester bond with hydroxyl groups on the target surface.
Ail is a 17-kDa chromosomally encoded outer membrane protein that mediates serum resistance (complement resistance) in the pathogenic Yersiniae (Yersinia pestis, Y. enterocolitica, and Y. pseudotuberculosis). In this article, we demonstrate that Y. pseudotuberculosis Ail from strains PB1, 2812/79, and YPIII/pIB1 (serotypes O:1a, O:1b, and O:3, respectively) can bind the inhibitor of the classical and lectin pathways of complement, C4b-binding protein (C4BP). Binding was observed irrespective of serotype tested and independently of YadA, which is the primary C4BP receptor of Y. enterocolitica. Disruption of the ail gene in Y. pseudotuberculosis resulted in loss of C4BP binding. Cofactor assays revealed that bound C4BP is functional, because bound C4BP in the presence of factor I cleaved C4b. In the absence of YadA, Ail conferred serum resistance to strains PB1 and YPIII, whereas serum resistance was observed in strain 2812/79 in the absence of both YadA and Ail, suggesting additional serum resistance factors. Ail from strain YPIII/pIB1 alone can mediate serum resistance and C4BP binding, because its expression in a serum-sensitive laboratory strain of Escherichia coli conferred both of these phenotypes. Using a panel of C4BP mutants, each deficient in a single complement control protein domain, we observed that complement control protein domains 6-8 are important for binding to Ail. Binding of C4BP was unaffected by increasing heparin or salt concentrations, suggesting primarily nonionic interactions. These results indicate that Y. pseudotuberculosis Ail recruits C4BP in a functional manner, facilitating resistance to attack from complement. PMID:22467648
Ho, Derek K; Riva, Rauna; Kirjavainen, Vesa; Jarva, Hanna; Ginström, Erica; Blom, Anna M; Skurnik, Mikael; Meri, Seppo
The recent identification of two mannose-binding lectin-associated serine protease clones from Halocynthia roretzi, an ascidian, suggested the presence of a complement system in urochordates. To elucidate the structure and function of this possibly primitive complement system, we have isolated cDNA clones for ascidian C3 (AsC3) and purified AsC3 protein from body fluid. The deduced primary structure of AsC3 shows overall
Masaru Nonaka; Kaoru Azumi; Xin Ji; Chisato Namikawa-Yamada; Makoto Sasaki; Hidetosi Saiga; Alister W. Dodds; Hideharu Sekine; Miwako K. Homma; Misao Matsushita; Yuichi Endo; Teizo Fujita
Poxviruses subvert the host immune response by producing immunomodulatory proteins, including a complement regulatory protein. Ectromelia virus provides a mouse model for smallpox where the virus and the host's immune response have co-evolved. Using this model, our study investigated the role of the complement system during a poxvirus infection. By multiple inoculation routes, ectromelia virus caused increased mortality by 7 to 10 days post-infection in C57BL/6 mice that lack C3, the central component of the complement cascade. In C3?/? mice, ectromelia virus disseminated earlier to target organs and generated higher peak titers compared to the congenic controls. Also, increased hepatic inflammation and necrosis correlated with these higher tissue titers and likely contributed to the morbidity in the C3?/? mice. In vitro, the complement system in naïve C57BL/6 mouse sera neutralized ectromelia virus, primarily through the recognition of the virion by natural antibody and activation of the classical and alternative pathways. Sera deficient in classical or alternative pathway components or antibody had reduced ability to neutralize viral particles, which likely contributed to increased viral dissemination and disease severity in vivo. The increased mortality of C4?/? or Factor B?/? mice also indicates that these two pathways of complement activation are required for survival. In summary, the complement system acts in the first few minutes, hours, and days to control this poxviral infection until the adaptive immune response can react, and loss of this system results in lethal infection.
Moulton, Elizabeth A.; Atkinson, John P.; Buller, R. Mark L
Lectins have been proven to be invaluable reagents for the histochemical detection of glycans in cells and tissues by light and electron microscopy. This technical review deals with the conditions of tissue fixation and embedding for lectin labeling, as well as various markers and related labeling techniques. Furthermore, protocols for lectin labeling of sections from paraffin and resin-embedded tissues are detailed together with various controls to demonstrate the specificity of the labeling by lectins. PMID:21805335
Two lectin-resistant mutants derived from Madin Darby canine kidney cells, with constitutive alterations in the asparagine-linked carbohydrate moieties, retained the characteristic structural and functional epithelial polarity of the parental cells. A ricin-resistant cell line was unable to incorporate galactose-sialic acid into glycoproteins and, from the pattern of cross-resistance to other lectins, appears to be different from previously described lines resistant to this lectin: the mutation in a concanavalin A-resistant line results, probably, in the production of defective carbohydrate cores of glycoproteins. In spite of glycosylation defects which result in an increased electrophoretic mobility of many cellular glycoproteins, both mutants retained the typical asymmetric structure of the plasma membrane (microvilli on the apical surface, junctional elements on the basolateral surface), functional tight junctions, and unidirectional active transport of electrolytes and water. These results suggest that glycoproteins with terminal galactose-sialic acid moieties are not critically involved in the development and maintenance of polarity in epithelial cells. The mutant cells, particularly the ricin-resistant line, exhibited, however, morphological and electrophysiological changes which suggest a quantitative effect of the mutations on intracellular traffic of membranes and tight junction formation. The cell lines described in this paper, the first lectin-resistant mutants of epithelial lineage, should prove useful tools for studying the peculiarities of glycosylating pathways in polarized cells. PMID:7177111
Meiss, H K; Green, R F; Rodriguez-Boulan, E J
Growing insights into the many roles of glycoconjugates in biorecognition as ligands for lectins indicates a need to compare plant and animal lectins. Furthermore, the popularity of plant lectins as laboratory tools for glycan detection and characterization is an incentive to start this review with a brief introduction to landmarks in the history of lectinology. Based on carbohydrate recognition by
Harold Rüdiger; Hans-J. Gabius
Poxviruses produce complement regulatory proteins to subvert the host's immune response. Similar to the human pathogen variola virus, ectromelia virus has a limited host range and provides a mouse model where the virus and the host's immune response have coevolved. We previously demonstrated that multiple components (C3, C4, and factor B) of the classical and alternative pathways are required to survive ectromelia virus infection. Complement's role in the innate and adaptive immune responses likely drove the evolution of a virus-encoded virulence factor that regulates complement activation. In this study, we characterized the ectromelia virus inhibitor of complement enzymes (EMICE). Recombinant EMICE regulated complement activation on the surface of CHO cells, and it protected complement-sensitive intracellular mature virions (IMV) from neutralization in vitro. It accomplished this by serving as a cofactor for the inactivation of C3b and C4b and by dissociating the catalytic domain of the classical pathway C3 convertase. Infected murine cells initiated synthesis of EMICE within 4 to 6 h postinoculation. The levels were sufficient in the supernatant to protect the IMV, upon release, from complement-mediated neutralization. EMICE on the surface of infected murine cells also reduced complement activation by the alternative pathway. In contrast, classical pathway activation by high-titer antibody overwhelmed EMICE's regulatory capacity. These results suggest that EMICE's role is early during infection when it counteracts the innate immune response. In summary, ectromelia virus produced EMICE within a few hours of an infection, and EMICE in turn decreased complement activation on IMV and infected cells.
Moulton, Elizabeth A.; Bertram, Paula; Chen, Nanhai; Buller, R. Mark L.; Atkinson, John P.
Mannan binding lectin (MBL)-associated serine protease type 1 (MASP-1) has a central role in the lectin pathway of complement activation and is required for the formation of C3 convertase. The activity of MASP-1 in the peripheral blood has been identified previously as a highly significant predictor of the severity of liver fibrosis in hepatitis C virus (HCV) infection, but not in liver disease of other aetiologies. In this study we tested the hypotheses that expression of MASP-1 may promote disease progression in HCV disease by direct activation of hepatic stellate cells (HSCs) and may additionally be up-regulated by HCV. In order to do so, we utilized a model for the maintenance of primary human HSC in the quiescent state by culture on basement membrane substrate prior to stimulation. In comparison to controls, recombinant MASP-1 stimulated quiescent human HSCs to differentiate to the activated state as assessed by both morphology and up-regulation of HSC activation markers ?-smooth muscle actin and tissue inhibitor of metalloproteinase 1. Further, the expression of MASP-1 was up-regulated significantly by HCV infection in hepatocyte cell lines. These observations suggest a new role for MASP-1 and provide a possible mechanistic link between high levels of MASP-1 and the severity of disease in HCV infection. Taken together with previous clinical observations, our new findings suggest that the balance of MASP-1 activity may be proinflammatory and act to accelerate fibrosis progression in HCV liver disease. PMID:23841802
Saeed, A; Baloch, K; Brown, R J P; Wallis, R; Chen, L; Dexter, L; McClure, C P; Shakesheff, K; Thomson, B J
This invention provides methods for: the control of mucosal cell proliferation; the reduction and/or treatment of damage caused by a cell-damaging agent; and for the reduction and/or treatment of a metabolic disorder. The methods comprise administering to an individual in need of control or reduction and/or treatment on effective amount of a lectin. The invention takes advantageous of the protective and repair capabilities of lectins. It is particularly useful in the prevention and treatment of animals undergoing radiotherapy and/or chemotherapy for cancer.
Pusztai; Arpad Janos (Scotland, GB); Bardocz; Zsuzsanna Magdolna (Scotland, GB); Palmer; Richard Michael John (England, GB); Fish; Neil William (England, GB); Koteles; Gyorgy J. (Budapest, HU)
Background—Mannose-binding lectin (MBL) is a circulating immune factor responsible for opsonization of pathogens and directly activating complement. Common variations in the MBL gene are responsible for an opsonic deficiency that affects 5% to 7% of whites and are associated with increased susceptibility to infections. After a preliminary report associating these variations with coronary artery disease (CAD), we determined MBL genotypes
Lyle G. Best; Michael Davidson; Kari E. North; Jean W. MacCluer; Ying Zhang; Elisa T. Lee; Barbara V. Howard; Susan DeCroo; Robert E. Ferrell
PurposeAge-related macular degeneration (AMD) is the leading cause of blindness in the developed world. There are increasing evidences to suggest the complement system may play a significant role on the pathogenesis of AMD. In this review, we summarise the current research in this area.MethodsReview of literature.ResultsThe complement system is a complex system with several activation pathways. Complement factor H (CFH)
S Sivaprasad; N V Chong
Inherited and acquired dysregulation of the complement alternative pathway plays an important role in multiple renal diseases. In recent years, the identification of disease-causing mutations and genetic variants in complement regulatory proteins has contributed significantly to our knowledge of the pathogenesis of complement associated glomerulopathies. In these diseases defective complement control leading to the deposition of activated complement products plays a key role. Consequently, complement-related glomerulopathies characterized by glomerular complement component 3 (C3) deposition in the absence of local immunoglobulin deposits are now collectively described by the term “C3 glomerulopathies.” Therapeutic strategies for reestablishing complement regulation by either complement blockade with the anti-C5 monoclonal antibody eculizumab or plasma substitution have been successful in several cases of C3 glomerulopathies. However, further elucidation of the underlying defects in the alternative complement pathway is awaited to develop pathogenesis-specific therapies.
Heeringa, Saskia F.; Cohen, Clemens D.
Lectins hold great promise not only as reagents for diagnostics and drug discovery but also as a novel class of biopharmaceutical products. In fact, new research directions in the last years have led to major developments in the uses of plant lectins as therapeutic agents against numerous diseases in an ageing society. It is even expected that lectins may occupy an important place in the biopharmaceutical industry next to monoclonal antibodies. All these new trends are placing a tremendous emphasis on the development of new approaches for faster lectins development, selection, and optimization, including alternatives methods of purification. This article reviews the isolation and purification methods used for lectins purification. Origins and applications of lectins are described, highlighting the special features of this class of proteins, such as the carbohydrated-binding domains and their importance in the development of affinity methodologies to increase and facilitate lectins purification. Published strategies for the purification of lectins from different sources are analyzed in relation to the purification methods used, their sequence, and the number of times they are used in a purification procedure. The purity of lectins is analyzed in relation to the average overall yield and purification factors obtained for each purification scheme for these proteins and the purification steps necessary. New directions are described for improving lectins separation and purification. PMID:23108612
Nascimento, Kelany S; Cunha, Ana I; Nascimento, Kyria S; Cavada, Benildo S; Azevedo, Ana M; Aires-Barros, Maria Raquel
Tetracapsuloides bryosalmonae is the myxozoan parasite that causes the commercially important proliferative kidney disease (PKD) in salmonid aquaculture. Previous studies on the binding of lectins to T. bryosalmonae identified Griffonia simplificola agglutinin I (GS I) as useful for parasite identification. This lectin was also implicated as recognizing antigenic structures on the parasite. Here, we examine the histochemical staining and ultrastructural localization of a panel of 21 lectins on the extrasporogonic stage of T. bryosalmonae. The histochemical staining studies indicated that the majority of lectins bound to the renal stages of T. bryosalmonae, however not all of these lectins could be successfully localized using immunogold electron microscopy. Of the lectins that were localized many, including GS I, bound to membranes associated with the lysosomal pathway within the extrasporogonic primary cell of the parasite, indicating that these organelles are rich in glycoconjugates. The histochemical staining of Erythrina cristagalli ECL was unique and highlighted a different distribution of glycoconjugates in the periphery of some extrasporogonic parasites within the renal sinuses when compared with stages in the interstitium, suggesting the presence of distinct blood forms of T. bryosalmonae. PMID:14986938
Morris, D J; Adams, A
As a first step to validate the use of carbon nanotubes as novel vaccine or drug delivery devices, their interaction with a part of the human immune system, complement, has been explored. Haemolytic assays were conducted to investigate the activation of the human serum complement system via the classical and alternative pathways. Western blot and sodium dodecyl sulphate-polyacrylamide gel electrophoresis
Carolina Salvador-Morales; Emmanuel Flahaut; Edith Sim; Jeremy Sloan; Malcolm L. H. Green; Robert B. Sim
The effects of 16 lectins isolated from foodstuff on the transport system across human intestinal Caco-2 cell monolayers were investigated by using four fluorescent markers: lucifer yellow (LY) for the paracellular pathway, fluorescein (FL) for the monocarboxylic acid transporter-mediated pathway, rhodamine 123 for the P-glycoprotein-mediated efflux pathway, and calcein for the multidrug resistance associated protein-related efflux pathway. The transepithelial electrical resistance (TER) values for the monolayers were also measured. WGA from wheat germ, ABA from white mushroom, AOL from Aspergillus oryzae, and CSL3 from chum salmon eggs (each at 100 µg/mL) decreased the TER value by 20-40% which resulted in increased LY transport. These lectins, as well as such other lectins as SBA from soybean, RBA from rice bran, and Con A from jack bean, affected other transport pathways too. These results indicate that the lectins modulated the transepithelial transport system in different ways, probably because of their specific binding characteristics toward Caco-2 cell monolayers. PMID:24018688
Yamamoto, Shintaro; Tomiyama, Mai; Nemoto, Ryo; Naganuma, Takako; Ogawa, Tomohisa; Muramoto, Koji
Complement proteins are generated both by the liver (systemic compartment) and by peripheral tissue-resident cells and migratory immune cells (local compartment). The immune cell-derived, alternative pathway complement components activate spontaneously, yielding local, but not systemic, production of C3a and C5a. These anaphylatoxins bind to their respective G-protein-coupled receptors, the C3a receptor and the C5a receptor, expressed on T cells and antigen-presenting cells, leading to their reciprocal activation and driving T-cell differentiation, expansion, and survival. Complement deficiency or blockade attenuates T-cell-mediated autoimmunity and delays allograft rejection in mice. Increasing complement activation, achieved by genetic removal of the complement regulatory protein decay accelerating factor, enhances murine T-cell immunity and accelerates allograft rejection. Signaling through the C3a receptor and the C5a receptor reduces suppressive activity of natural regulatory T cells and the generation and stability of induced regulatory T cells. The concepts, initially generated in mice, recently were confirmed in human immune cells, supporting the need for testing of complement targeting therapies in organ transplants patients. PMID:24161041
Cravedi, Paolo; van der Touw, William; Heeger, Peter S
In this study, we investigated the pharmacological reactions induced by ibudilast to the complement system with the aim of clarifying the functional relation of the complement system to allergic reactions and pathology in patients with bronchial asthma. Complement hemolytic activities (CH50 and ACH50), complement profile, anaphylatoxins (C3a and C5a) and complement fragments (Bb, iC3b and C4d) were measured in 20 patients with bronchial asthma. One of antiasthmatic activities induced by ibudilast was concluded to be brought about though inactivation of the alternative complement pathway working on type III allergic reaction. Ibudilast increased the complement fragment Bb in the patients' plasma with the fairly controlled bronchial asthma. This increase in circulating Bb was suspected to be a result of inactivation of intermediate complement complexes, for example C3b.Bb.P, because the amounts in plasma of C3 and C5 showed no changes, while those of factor, B, P, H and I were decreased by ibudilast administration in patients with fairly controlled bronchial asthma. This antiasthmatic ability of ibudilast was restrained in those patients whose peripheral leukocytopenia was advanced before ibudilast administration, and in those whom ibudilast did not provoke an increase in the plasma level of iC3b, or did not prevent the serum level of C5 from increasing. In those unfairly controlled cases, enough anaphylatoxins, especially C5a might be produced to make the margination of peripheral neutrophils to the lung and increase CR3 on neutrophils binding with iC3b. PMID:1772350
Onodera, H; Okamoto, M; Takemura, S; Doi, T; Kasamatsu, Y; Yanagida, K; Fukuda, W; Tanaka, M; Deguchi, M; Ueda, M
In the present study, we have shown the vast importance of biomaterial nanotexture when evaluating inflammatory response. For the first time in an in vitro whole blood system, we have proven that a small increase in nanoporesize, specifically 180 nm (from 20 to 200 nm), has a huge effect on the complement system. The study was done using nanoporous aluminiumoxide, a material that previously has been evaluated for potential implant use, showing good biocompatibility. This material can easily be manufactured with different pore sizes making it an excellent candidate to govern specific protein and cellular events at the tissue-material interface. We performed whole blood studies, looking at complement activation after blood contact with two pore size alumina membranes (pore diameters, 20 and 200 nm). The fluid phase was analyzed for complement soluble components, C3a and sC5b-9. In addition, surface adsorbed proteins were eluted and dot blots were performed to detect IgG, IgM, C1q, and C3. All results point to the fact that 200 nm pore size membranes are more complement activating. Significantly, higher values of complement soluble components were found after whole blood contact with 200 nm alumina and all studied proteins adsorbed more readily to this membrane than to the 20 nm pore size membrane. We hypothesize that the difference in complement activation between our two test materials is caused by the type and the amount of adsorbed proteins, as well as their conformation and orientation. The different protein patterns created on the two alumina membranes are most likely a consequence of the material topography. PMID:18186072
Ferraz, Natalia; Nilsson, Bo; Hong, Jaan; Karlsson Ott, Marjam
Galanthus nivalis agglutinin (GNA)-related lectin family, a superfamily of strictly mannose-binding specific lectins widespread among monocotyledonous plants, is well-known to possess a broad range of biological functions such as anti-tumor, anti-viral and anti-fungal activities. Herein, we mainly focused on exploring the precise molecular mechanisms by which GNA-related lectins induce cancer cell apoptotic and autophagic death targeting mitochondria-mediated ROS-p38-p53 apoptotic or autophagic pathway, Ras-Raf and PI3K-Akt anti-apoptotic or anti-autophagic pathways. In addition, we further discussed the molecular mechanisms of GNA-related lectins exerting anti-viral activities by blocking the entry of the virus into its target cells, preventing transmission of the virus as well as forcing virus to delete glycan in its envelope protein and triggering neutralizing antibody. In conclusion, these findings may provide a new perspective of GNA-related lectins as potential drugs for cancer and virus therapeutics in the future. PMID:22893111
Wu, Lei; Bao, Jin-Ku
Lectins are generally associated with plant or animal components, selectively bind carbohydrates, and interact with procaryotic and eucaryotic cells. Lectins have various specificities that are associated with their ability to interact with acetylaminocarbohydrates, aminocarbohydrates, sialic acids, hexoses, pentoses, and as other carbohydrates. Microbial surfaces generally contain many of the sugar residues that react with lectins. Lectins are presently used in the clinical laboratory to type blood cells and are used in a wide spectrum of applications, including, in part, as carriers of chemotherapeutic agents, as mitogens, for fractionation of animal cells, and for investigations of cellular surfaces. Numerous studies have shown that lectins can be used to identify rapidly certain microorganisms isolated from a clinical specimen or directly in a clinical specimen. Lectins have been demonstrated to be important diagnostic reagents in the major realms of clinical microbiology. Thus, they have been applied in bacteriology, mycology, mycobacteriology, and virology for the identification and/or differentiation of various microorganisms. Lectins have been used successfully as epidemiologic as well as taxonomic markers of specific microorganisms. Lectins provide the clinical microbiologist with cost-effective and potential diagnostic reagents. This review describes the applications of lectins in clinical microbiology. Images
Slifkin, M; Doyle, R J
Lectins are a widespread class of proteins implicated in many essential cellular and molecular recognition processes. They recognize carbohydrates in a non-catalytic, specific and reversible manner. Fungi, which include mushrooms, microfungi and yeasts, have attracted wide interest in recent years. They are indeed a promising source for novel lectins with unique specificity and potential for biomedical and biotechnological applications. Information on fungal lectins, particularly structural insight, is scarce compared to that on their plant and animal counterparts. This review therefore focuses on the structure, function, and exploitable properties of fungal lectins. PMID:23920351
Varrot, Annabelle; Basheer, Soorej M; Imberty, Anne
Bordetella pertussis causes whooping cough in humans, a highly contagious disease of the upper respiratory tract. An increase in cases of whooping cough in adolescents and adults in many countries has been reported, despite high immunization rates in children. To efficiently colonize the host the bacteria have to resist complement, the first defence line of innate immunity. B. pertussis has previously been shown to bind the classical pathway inhibitors C4b-binding protein and C1-inhibitor being thereby able to escape the classical pathway of complement. In this study recent clinical isolates of B. pertussis and B. parapertussis were found to survive alternative pathway attack in fresh non-immune serum better than the reference B. pertussis strain, Tohama I. By using adsorption assays, flow cytometry and a radioligand binding assay we observed that both B. pertussis and B. parapertussis bound the alternative pathway inhibitor factor H (FH) from normal human serum. The surface attached FH maintained its complement regulatory activity and promoted factor I-mediated cleavage of C3b. The main binding region was located to the C-terminal part of FH, into short consensus repeat domains 19-20. In contrast, the avian pathogen B. avium did not bind FH and was sensitive to the alternative pathway of human complement. In conclusion, the human pathogens B. pertussis and B. parapertussis are able to evade the alternative complement pathway by surface acquisition of the host complement regulator FH. PMID:21167605
Amdahl, Hanne; Jarva, Hanna; Haanperä, Marjo; Mertsola, Jussi; He, Qiushui; Jokiranta, T Sakari; Meri, Seppo
The complement system plays a key role in host defense and in the development of autoimmunity. Three types of animal models of complement-mediated disease have traditionally been used: they involve normal animals, animals with spontaneously arising genetic deficiency, and animals treated with complement-inactivating agents. All of these approaches have had partial success in our attempts to understand complement mechanisms. Most
Michael M. Frank
Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a group of autoimmune disorders. It was previously assumed that the complement system is not involved in the development of ANCA-associated vasculitis due to its "pauci-immune" feature in renal histology. However, increasing evidence indicates that activation of the complement system, especially via the alternative complement pathway, plays a crucial role in the pathogenesis of ANCA-associated vasculitis. In this brief review, we discuss the evidence, including in vivo, in vitro, and clinical studies, for complement system activation in ANCA-associated vasculitis. PMID:23180036
Yuan, Jun; Chen, Min; Zhao, Ming-Hui
Soluble beta-glucan polysaccharide binding to the lectin site of neutrophil or natural killer cell complement receptor type 3 (CD11b/CD18) generates a primed state of the receptor capable of mediating cytotoxicity of iC3b-opsonized target cells.
When phagocyte CR3 binds to iC3b on bacteria or yeast, phagocytosis and degranulation are triggered because of simultaneous recognition of iC3b via a CD11b I-domain binding site and specific microbial polysaccharides via a lectin site located COOH-terminal to the I-domain. By contrast, when phagocyte or natural killer (NK) cell CR3 adheres to iC3b on erythrocytes or tumor cells that lack CR3-binding membrane polysaccharides, neither lysis nor cytotoxicity are stimulated. This investigation showed that soluble CR3-specific polysaccharides such as beta-glucan induced a primed state of CR3 that could trigger killing of iC3b-target cells that were otherwise resistant to cytotoxicity. Anti-CR3 added before sugars prevented priming, whereas anti-CR3 added after sugars blocked primed CR3 attachment to iC3b-targets. Polysaccharide priming required tyrosine kinase(s) and a magnesium-dependent conformational change of the I-domain that exposed the CBRM1/5 activation epitope. Unlike LPS or cytokines, polysaccharides did not up-regulate neutrophil CR3 expression nor expose the mAb 24 reporter epitope representing the high affinity ICAM-1-binding state. The current data apparently explain the mechanism of tumoricidal beta-glucans used for immunotherapy. These polysaccharides function through binding to phagocyte or NK cell CR3, priming the receptor for cytotoxicity of neoplastic tissues that are frequently targeted with iC3b and sparing normal tissues that lack iC3b.
Vetvicka, V; Thornton, B P; Ross, G D
The presence of complement activation products has been studied in morphologically normal human lymphatic tissue from tonsil, spleen and lymph node. Newly established monoclonal antibodies (mAbs) with reactivity against the C4 cleavage fragments C4a, C4b, C4c and C4d were applied on cyrostat sections in the indirect immunoperoxidase staining technique. Irrespective of organ type, C4d activation product could be detected in germinal centres of all secondary lymphoid follicles. To substantiate this finding, the complete sequence of complement activation products was investigated by a series of mono- and polyclonal antibodies to the complement proteins C1, C2, C3, factor B, C5, C9 to C5b-9 neoantigens and to the regulatory complement proteins C4 binding protein (C4bp), factor I, factor H and properdin. Similar to C4d, all secondary follicles exhibited a strong staining reaction for C3d antigens restricted to germinal centres. At the same site, albeit with distinctly weaker intensity, components of the membrane attack complex (MAC) C5b-9 were found. The simultaneous deposition of C1, C4b and C4bp in certain germinal centres indicates that complement activation is induced via the classical pathway. Concomitant deposition of IgM suggests IgM-antigen complexes that have been trapped on follicular dendritic cells (FDC) during normal immune response as the most likely candidates for activators of the classical pathway. Our data demonstrate that human lymphoid germinal centres as important sites of immune regulation closely interrelate with the complete cascade of complement-activation products, including the membrane attack complex (MAC). Images Figure 1 Figure 2 Figure 3 Figure 4
Zwirner, J; Felber, E; Schmidt, P; Riethmuller, G; Feucht, H E
Calnexin is a membrane-bound lectin chaperone in the endoplasmic reticulum (ER) that is part of a quality control system that promotes the accurate folding of glycoproteins entering the secretory pathway. We have previously shown that ER homeostasis is important for virulence of the human fungal pathogen Aspergillus fumigatus, but the contribution of calnexin has not been explored. Here, we determined the extent to which A. fumigatus relies on calnexin for growth under conditions of environmental stress and for virulence. The calnexin gene, clxA, was deleted from A. fumigatus and complemented by reconstitution with the wild type gene. Loss of clxA altered the proteolytic secretome of the fungus, but had no impact on growth rates in either minimal or complex media at 37°C. However, the ?clxA mutant was growth impaired at temperatures above 42°C and was hypersensitive to acute ER stress caused by the reducing agent dithiothreitol. In contrast to wild type A. fumigatus, ?clxA hyphae were unable to grow when transferred to starvation medium. In addition, depleting the medium of cations by chelation prevented ?clxA from sustaining polarized hyphal growth, resulting in blunted hyphae with irregular morphology. Despite these abnormal stress responses, the ?clxA mutant remained virulent in two immunologically distinct models of invasive aspergillosis. These findings demonstrate that calnexin functions are needed for growth under conditions of thermal, ER and nutrient stress, but are dispensable for surviving the stresses encountered in the host environment.
Powers-Fletcher, Margaret V.; Jambunathan, Kalyani; Brewer, Jordan L.; Krishnan, Karthik; Feng, Xizhi; Galande, Amit K.; Askew, David S.
Calnexin is a membrane-bound lectin chaperone in the endoplasmic reticulum (ER) that is part of a quality control system that promotes the accurate folding of glycoproteins entering the secretory pathway. We have previously shown that ER homeostasis is important for virulence of the human fungal pathogen Aspergillus fumigatus, but the contribution of calnexin has not been explored. Here, we determined the extent to which A. fumigatus relies on calnexin for growth under conditions of environmental stress and for virulence. The calnexin gene, clxA, was deleted from A. fumigatus and complemented by reconstitution with the wild type gene. Loss of clxA altered the proteolytic secretome of the fungus, but had no impact on growth rates in either minimal or complex media at 37°C. However, the ?clxA mutant was growth impaired at temperatures above 42°C and was hypersensitive to acute ER stress caused by the reducing agent dithiothreitol. In contrast to wild type A. fumigatus, ?clxA hyphae were unable to grow when transferred to starvation medium. In addition, depleting the medium of cations by chelation prevented ?clxA from sustaining polarized hyphal growth, resulting in blunted hyphae with irregular morphology. Despite these abnormal stress responses, the ?clxA mutant remained virulent in two immunologically distinct models of invasive aspergillosis. These findings demonstrate that calnexin functions are needed for growth under conditions of thermal, ER and nutrient stress, but are dispensable for surviving the stresses encountered in the host environment. PMID:22163332
Powers-Fletcher, Margaret V; Jambunathan, Kalyani; Brewer, Jordan L; Krishnan, Karthik; Feng, Xizhi; Galande, Amit K; Askew, David S
The International X-ray Observatory (IXO) has recently been created as a mission concept by a joint team of NASA, ESA and JAXA scientists, based on the previous Constellation-X and XEUS concepts. Definition of the IXO instruments is still under evolution, but the core instrument complement will include a Wide Field X-ray Imager, an X-ray Calorimeter / Narrow Field X-ray Imager, and an X-ray Grating Spectrometer. Other, modest additional instruments (such as a hard X-ray capability, a polarimeter, and a high time resolution detector) will also be considered. We present the current status of the IXO instrument complement and offer the opportunity for discussion of ideas relevant to the IXO mission concept process.
Nousek, John A.; IWG, IXO
The caudices of 10 Adenia species contain galactose-binding lectins that were purified by affinity chromatography. All lectins but three agglutinate human erythrocytes. Six lectins consist of two unequal chains, which can be separated by reduction, and inhibit protein synthesis both by a rabbit reticulocyte lysate and by HeLa and Raji cells. The lectins from A. goetzii, A. lanceolata and A.
Emanuele Pelosi; Chiara Lubelli; Letizia Polito; Luigi Barbieri; Andrea Bolognesi; Fiorenzo Stirpe
Dilated cardiomyopathy is a syndrome characterized by cardiac enlargement and impaired systolic function of the heart. Tumor necrosis factor (TNF)-?, a pleiotropic cytokine, seems to play a central role in the progression of dilated cardiomyopathy. Recent data suggest that ongoing inflammation in the myocardium may, in many cases, contribute to the development of disease. Chronic generation of autoantibodies to myocardial antigens or, in some cases, viral infection are pathobiologically involved. Although both antibodies and some viruses activate the complement system, the role of innate immunity in dilated cardiomyopathy has as yet not been investigated systematically. In this study we demonstrate by analysis of myocardial biopsies from 28 patients that C5b-9, the terminal membrane attack complex of complement, accumulates in human myocardium in dilated cardiomyopathy. C5b-9 significantly correlates with immunoglobulin deposition and myocardial expression of TNF-?. In vitro, C5b-9 attack on cardiac myocytes induces nuclear factor (NF)-?B activation as well as transcription, synthesis, and secretion of TNF-?. We conclude that chronic immunoglobulin-mediated complement activation in the myocardium may contribute in part to the progression of dilated cardiomyopathy via C5b-9-induced TNF-? expression in cardiac myocytes.
Zwaka, Thomas P.; Manolov, Dimitar; Ozdemir, Cuneyt; Marx, Nikolaus; Kaya, Ziya; Kochs, Matthias; Hoher, Martin; Hombach, Vinzenz; Torzewski, Jan
Age-related macular degeneration (AMD) is an inflammatory disease, which causes visual impairment and blindness in older people. The proteins of the complement system are central to the development of this disease. Local and systemic inflammation in AMD are mediated by the deregulated action of the alternative pathway of the complement system. Variants in complement system genes alter an individual's risk
D T Bradley; P F Zipfel; A E Hughes
Based on sequence homologies with leguminous lectins, the intermediate compartment marker ERGIC-53 was proposed to be a member of a putative new class of animal lectins associated with the secretory pathway. Independent, a promyelocytic protein, MR60, was purified by mannose-column chromatography, and a cDNA was isolated that matched MR60 peptide sequences. This cDNA was identical to that of ERGIC-53 and homologies with the animal lectin family of the galectins were noticed. Not all peptide sequences of MR60, however, were found in ERGIC-53, raising the possibility that another protein associated with ERGIC-53 may possess the lectin activity. Here, we provide the first direct evidence for a lectin function of ERGIC-53. Overexpressed ERGIC-53 binds to a mannose column in a calcium-dependent manner and also co-stains with mannosylated neoglycoprotein in a morphological binding assay. By using a sequential elution protocol we show that ERGIC-53 has selectivity for mannose and low affinity for glucose and GlcNAc, but no affinity for galactose. To experimentally address the putative homology of ERGIC-53 to leguminous lectins, a highly conserved protein family with an invariant asparagine essential for carbohydrate binding, we substituted the corresponding asparagine in ERGIC-53. This mutation, as well as a mutation affecting a second site in the putative carbohydrate recognition domain, abolished mannose-column binding and co-staining with mannosylated neoglycoprotein. These findings establish ERGIC-53 as a lectin and provide functional evidence for its relationship to leguminous lectins. Based on its monosaccharide specificity, domain organization, and recycling properties, we propose ERGIC-53 to function as a sorting receptor for glyco-proteins in the early secretory pathway. Images
Itin, C; Roche, A C; Monsigny, M; Hauri, H P
Host-pathogen interactions have coevolved for many years. On the one hand, the human immune system consists of innate and adaptive immune cells that function to defeat pathogens, and on the other hand, pathogens have coevolved to use the system for their own propagation. C-type lectins are conserved receptors recognizing carbohydrate structures on viruses, bacteria, parasites, and fungi. C-type lectins such as DC-SIGN, langerin, and dectin-1 are expressed by dendritic cell subsets and macrophages. Pathogen recognition by C-type lectins triggers signaling pathways that lead to the expression of specific cytokines which subsequently instruct adaptive T helper immune responses. T helper cell differentiation is crucial for initiating proper adaptive immune responses; some pathogens, however, use pattern recognition receptors like C-type lectins to subvert immune responses for survival. This review provides an update on the role of C-type lectins in HIV-1, mycobacterial, and Candida infections, and the coevolution of hosts and pathogens. PMID:22288724
van den Berg, Linda M; Gringhuis, Sonja I; Geijtenbeek, Teunis B H
Poxviruses encode a repertoire of immunomodulatory proteins to thwart the host immune system. One among this array is a homolog of the host complement regulatory proteins that is conserved in various poxviruses including vaccinia (VACV) and variola. The vaccinia virus complement control protein (VCP), which inhibits complement by decaying the classical pathway C3-convertase (decay-accelerating activity), and by supporting inactivation of C3b and C4b by serine protease factor I (cofactor activity), was shown to play a role in viral pathogenesis. However, the role its individual complement regulatory activities impart in pathogenesis, have not yet been elucidated. Here, we have generated monoclonal antibodies (mAbs) that block the VCP functions and utilized them to evaluate the relative contribution of complement regulatory activities of VCP in viral pathogenesis by employing a rabbit intradermal model for VACV infection. Targeting VCP by mAbs that inhibited the decay-accelerating activity as well as cofactor activity of VCP or primarily the cofactor activity of VCP, by injecting them at the site of infection, significantly reduced VACV lesion size. This reduction however was not pronounced when VCP was targeted by a mAb that inhibited only the decay-accelerating activity. Further, the reduction in lesion size by mAbs was reversed when host complement was depleted by injecting cobra venom factor. Thus, our results suggest that targeting VCP by antibodies reduces VACV pathogenicity and that principally the cofactor activity of VCP appears to contribute to the virulence.
Bernet, John; Ahmad, Muzammil; Mullick, Jayati; Panse, Yogesh; Singh, Akhilesh K.; Parab, Pradeep B.; Sahu, Arvind
Studies of signal transduction are often focused on dissecting the cellular response to a single stimulus that activates a single receptor. These types of studies laid the foundation for our current understanding of signaling, as well as the generation of countless arrow-containing models in today’s textbooks. Implicit in most models is the suggestion that the arrows emanating from an activated receptor represent the core signaling pathways that are always activated by a given receptor, thus leading to a core cellular response. In nature, however, it is likely that no signaling pathway is activated in isolation. Rather, cells often respond to multiple stimuli simultaneously, and the cellular response may be the result of several signaling pathways. A new study attempts to model such conditions in vitro and reveals that when macrophages encounter bacteria, two signal transduction pathways interact in a way that profoundly alters the cellular response to infection.
Jonathan C. Kagan (Children's Hospital Boston;Division of Gastroenterology and Harvard Medical School REV)
Neuroinflammatory and neuroimmune mechanisms, as exemplified by infiltrating immune cells and activation of resident endothelial\\/glial cells, respectively, are known to be involved in the establishment and maintenance of chronic pain. An immune system pathway that may be involved in the activation of both immune and glial cells is complement. The complement pathway is made up of a large number of
Margaret E. Levin; Jason G. Jin; Rui-Ru Ji; Jeifei Tong; James D. Pomonis; Daniel J. Lavery; Scott W. Miller; Lillian W. Chiang
Objective: Human ?-defensin (HBD) and the complement system are two important innate immune mechanisms active against a broad range of burn and wound pathogens. However, excessive or uncontrolled complement activation, following thermal injury, contributes to tissue damage. Previous studies from our laboratory suggested a decreased expression of HBD-2 in burn wounds and its absence in burn blister fluid. Prior studies have demonstrated that human neutrophil peptide can bind to the C1q component of the complement system and prevent complement activation. The objective of this study was to determine whether HBD-1 and HBD-2 can also bind to the C1q component and modulate complement activity. Methods: The binding efficiency of HBD-1 and HBD-2 to the C1q component was determined by utilizing dot blot hybridization. The effect of HBD-2 on the activation of the complement system by the classical and alternative pathways was determined by CH50 and AP50 assays. In addition, the ability of HBD-1 and HBD-2 to inhibit C1q activity was predicted by a comparison with known C1q inhibitor peptide 2J in a DNAStar computer modeling study. Results: C1q binding to HBD-2 was strong, whereas C1q binding to HBD-1 was weak. HBD-2 inhibits the classical pathway significantly without affecting the alternative pathway. In addition, a computer modeling study also revealed structural homology of HBD-2 with known C1q inhibitory sequences of HBD-2. Conclusion: HBD-2 inhibits the classical pathway. The replacement of missing defensin, a natural inhibitor of the complement system, may have a dual protective role not only as an antimicrobial agent but also in providing protection against uncontrolled activation of the complement system.
Bhat, Satyanarayan; Song, Yau-Hau; Lawyer, Carl; Milner, Stephen M.
Aspergillus fumigatus is a major fungal pathogen that may be fatal to immunocompromised individuals and causes airway hyperreactivity and re- modeling in sensitized individuals. Herein, we exam- ined the role of mannose-binding lectin (MBL), a complement-activating plasma protein, during pul- monary innate and allergic immune responses di- rected against A. fumigatus spores or conidia. Nei- ther group of nonsensitized MBL-A-sufficient
Cory M. Hogaboam; Kazue Takahashi; R. Alan; B. Ezekowitz; Steven L. Kunkel; Jane M. Schuh
The bacterium Francisella tularensis (Ft) is a potential weapon of bioterrorism when aerosolized. Macrophage infection is necessary for disease progression and efficient phagocytosis by human macrophages requires serum opsonization by complement. Microbial complement activation leads to surface deposition of a highly regulated protein complex resulting in opsonization or membrane lysis. The nature of complement component C3 deposition, i.e., C3b (opsonization and lysis) or C3bi (opsonization only) fragment deposition, is central to the outcome of activation. In this study, we examine the mechanisms of Ft resistance to complement-mediated lysis, C3 component deposition on the Ft surface, and complement activation. Upon incubation in fresh nonimmune human serum, Schu S4 (Ft subsp. tularensis), Fn (Ft subsp. novicida), and LVS (Ft subsp. holarctica live vaccine strain) were resistant to complement-mediated lysis, but LVSG and LVSR (LVS strains altered in surface carbohydrate structures) were susceptible. C3 deposition, however, occurred on all strains. Complement-susceptible strains had markedly increased C3 fragment deposition, including the persistent presence of C3b compared with C3bi, which indicates that C3b inactivation results in survival of complement-resistant strains. C1q, an essential component of the classical activation pathway, was necessary for lysis of complement-susceptible strains and optimal C3 deposition on all strains. Finally, use of Francisella LPS mutants confirmed O Ag as a major regulator of complement resistance. These data provide evidence that pathogenic Francisella activate complement, but are resistant to complement-mediated lysis in part due to limited C3 deposition, rapid conversion of surface-bound C3b to C3bi, and the presence of LPS O Ag. PMID:18832715
Clay, Corey D; Soni, Shilpa; Gunn, John S; Schlesinger, Larry S
Lectin activity of three ferns species (Dryopteris bushiana Fom., D. laeta (Kom.) C. Chr, D. pseudomas (Wollaston) Holub et Pouzar) has been studied. We used hemagglutination reaction albumin and globulin fractions of fronds and rhizomes extracts with rat erythrocytes. The frond extract of D. pseudomas have shown higher activity as compared with other extracts. The lectin activity of D. laeta leaves was absent. The rhizomes of all three fern species could be characterized as high activity. Based on lectin activity the species were placed as follows order: D. buschiana > D. pseudomas > D. laeta. The dependence with lectin activity and elements (Mn, Fe, Cu, Ni, Zn, Pb, Rb, Sr) content were not found. PMID:10609312
Basheka, O V; Stetsenko, N M; Pogorila, N F
Mannose binding lectin (MBL) activates complement pathway that leads to pathogen opsonization and phagocytosis. MBL deficiency is linked to HIV transmission and disease progression. We sought to determine the role of MBL in HIV encephalitis (HIVE) by evaluating its presence and distribution in the HIV-1-infected brain and by assessing its association with monocyte chemoattractant protein-1 (MCP-1) expression. This retrospective study utilized archived post-mortem brain tissues obtained from 35 individuals enrolled in a longitudinal study as part of the California NeuroAIDS Tissue Network. MBL, MCP-1 and brain cell markers in post-mortem brain tissues with or without HIVE were evaluated using immunocytochemistry, immunofluorescence, confocal microscopy, and western blots. MBL was expressed in neurons, astrocytes, microglia, and oligodendrocytes of the frontal cortex of the HIV-1-infected brain. Overall, there were 30% to 40% more MBL-positive brain cells in HIVE vs non-HIVE cases (P = 0.01, paired t-test). Specifically, there was an increased MBL expression in the neuronal axons of HIVE cases. Also, western blots showed 3- to 4-fold higher levels of 78 kD MBL trimers in HIVE vs non-HIVE cases. This MBL-HIVE link was further confirmed by MBL associated higher MCP-1 expression in HIVE vs non-HIVE cases. HIV negative healthy individuals and normal or the gp120 transgenic mice did not show any differential MBL expression. Increased MBL expression in the major brain cell types, specifically in the neuronal axons of HIVE brain, and MBL associated higher MCP-1 expression in HIVE suggest that MBL could cause neuroinflammation and neuronal injury through MBL complement activation pathway.
Singh, Kumud K; Nathamu, Satyanarayana; Adame, Anthony; Alire, Tara U; Dumaop, Wilmar; Gouaux, Ben; Moore, David J; Masliah, Eliezer
Objective: To investigate the effect of mannose-binding lectin (MBL) gene polymorphism on the immune system and the significance of vaginal MBL concentration in the pathogenesis of vulvovaginal candidiasis (VVC) and recurrent VVC (rVVC). Patients and methods: Mannose-binding lectin concentrations in CVL samples from 111 women were collected between August 2004 and November 2004, 51 with VVC, 6 with rVVC patients,
Fei Liu; Qinping Liao; Zhaohui Liu
Sixty-four sequences containing lectin domains with homologs of known three-dimensional structure were identified through a search of mycobacterial genomes. They appear to belong to the ?-prism II, the C-type, the Microcystis virdis (MV), and the ?-trefoil lectin folds. The first three always occur in conjunction with the LysM, the PI-PLC, and the ?-grasp domains, respectively while mycobacterial ?-trefoil lectins are unaccompanied by any other domain. Thirty heparin binding hemagglutinins (HBHA), already annotated, have also been included in the study although they have no homologs of known three-dimensional structure. The biological role of HBHA has been well characterized. A comparison between the sequences of the lectin from pathogenic and nonpathogenic mycobacteria provides insights into the carbohydrate binding region of the molecule, but the structure of the molecule is yet to be determined. A reasonable picture of the structural features of other mycobacterial proteins containing one or the other of the four lectin domains can be gleaned through the examination of homologs proteins, although the structure of none of them is available. Their biological role is also yet to be elucidated. The work presented here is among the first steps towards exploring the almost unexplored area of the structural biology of mycobacterial lectins. PMID:23180653
Abhinav, K V; Sharma, Alok; Vijayan, M
Plant lectins or phytohemagglutinins possess potent in vivo biological activities. Some, primarily of the family Leguminosae, have been shown to have deleterious nutritional effects. Little information exists, however, regarding the prevalencelectins or the specific foods that contain lectins in the United States diet. In the present study the edible parts of 29 of 88 foods tested, including common salad ingredients,
Martin S. Nachbar; Joel D. Oppenheim
Complement is an ancient danger sensing system playing critical roles in host defense, immune surveillance and homeostasis1. C5a and its G-Protein-coupled receptor mediate many of the pro-inflammatory properties of complement2. Despite its critical role in allergic asthma3, autoimmune arthritis4, sepsis5 and cancer6, our knowledge about C5a regulation is limited. Here we demonstrate an unexpected link through which IgG1 immune complexes (IC), the inhibitory IgG receptor Fc?RIIB and the C-type lectin-like receptor Dectin-1 suppress C5a receptor (C5aR) functions. Specifically, we found that IgG1 IC associate Fc?RIIB with Dectin-1, resulting in phosphorylation of spleen tyrosine kinase (Syk) downstream of Dectin-1 and Src homology 2 domain containing inositol phosphatase (SHIP) downstream of Fc?RIIB. This pathway blocks C5a receptor-mediated ERK1/2 phosphorylation and C5a effector functions in vitro and C5a-dependent inflammatory responses in vivo including the development of skin blisters in experimental epidermolysis bullosa acquisita (EBA), an autoimmune skin disorder. Notably, high galactosylation of IgG N-glycan is critical for this inhibitory property of IgG1 IC as it promotes the association between Fc?RIIB and Dectin-1. Thus, galactosylated IgG1 and Fc?RIIB exert immunoregulatory properties beyond their impact on activating Fc?Rs that may control allergy, autoimmunity and cancer.
Karsten, Christian M.; Pandey, Manoj K.; Figge, Julia; Kilchenstein, Regina; Taylor, Philip R.; Rosas, Marcela; McDonald, Jacqueline U.; Orr, Selinda J.; Berger, Markus; Petzold, Dominique; Blanchard, Veronique; Winkler, Andre; Hess, Constanze; Reid, Delyth M.; Majoul, Irina V.; Strait, Richard T.; Harris, Nathaniel L.; Kohl, Gabriele; Wex, Eva; Ludwig, Ralf; Zillikens, Detlef; Nimmerjahn, Falk; Finkelman, Fred D.; Brown, Gordon D.; Ehlers, Marc; Kohl, Jorg
Since the original proposal by Fearon that the Complement System linked innate and adaptive immunity (1), there has been a rapid expansion of studies on this topic. With the advance of intravital imaging, a number of recent papers have revealed an additional novel pathway in which complement C3 and its receptors enhance humoral immunity through delivery of antigen to the B cell compartment. In this review, we will discuss this pathway and highlight several novel exceptions recently found with a model influenza vaccine such as: (a) MBL opsonization of influenza and uptake by macrophages; (b) and capture of virus by dendritic cells residing in the medullary compartment of peripheral lymph nodes.
Gonzalez, Santiago F.; Lukacs-Kornek, Veronika; Kuligowski, Michael P.; Pitcher, Lisa A.; Degn, S?ren E.; Turley, Shannon J.; Carroll, Michael C.
A total of 101 isolates of penicillinase-producing and non-penicillinase-producing Neisseria gonorrhoeae with known nutritional requirements, plasmid content, and serovars, were examined for lectin agglutination patterns. These isolates were from outbreaks in Georgia, California, Hawaii, and Pennsylvania. Cell suspensions made from 16- to 18-h cultures were mixed with 14 different lectins, and the resultant agglutination patterns were classified as agglutination groups. Among the 101 isolates tested, 24 different agglutination groups were demonstrated. Of the organisms tested, 55% were located in 3 of the 24 groups, and 86% of the isolates reacted with the lectins Trichosanthes kinlowii, Griffonia simplicifolia I, peanut agglutinin, soybean agglutinin, potato agglutinin, and wheat germ agglutinin. One isolate did not react with peanut or potato agglutinin, five isolates lacked reactivity with potato agglutinin, and six isolates did not react with wheat germ agglutinin. Of the wheat germ-negative isolates, four were from Pennsylvania and were identical with regard to auxotype, plasmid content, serovar, and lectin group. The other two wheat germ-negative isolates were from California and were unrelated by the same criteria to the four Pennsylvania isolates and to each other. Among the isolates tested, there were no differences in lectin groups with regard to the sex of the patient. In the Georgia collection, agglutination with one lectin group was confined to isolates of serogroup IA. This association was not observed for the other geographic areas. Some isolates showing identical auxotype, plasmid content, and serovars could be differentiated based on lectin agglutination patterns, whereas other isolates were identical by all testing criteria.
Schalla, W O; Whittington, W L; Rice, R J; Larsen, S A
C-type lectin receptors (CLRs) represent a large receptor family including collectins, selectins, lymphocyte lectins, and proteoglycans. CLRs share a structurally homologous carbohydrate-recognition domain (CRD) and often bind carbohydrates in a Ca(2+)-dependent manner. In innate immunity, CLRs serve as pattern recognition receptors (PRRs) and bind to the glycan structures of pathogens and also to self-antigens. In nature, the low affinity of CLR/carbohydrate interactions is overcome by multivalent ligand presentation at the surface of cells or pathogens. Thus, multivalency is a promising strategy for targeting CLR-expressing cells and, indeed, carbohydrate-based targeting approaches have been employed for a number of CLRs, including asialoglycoprotein receptor (ASGPR) in the liver, or DC-SIGN expressed by dendritic cells. Since CLR engagement not only mediates endocytosis but also influences intracellular signaling pathways, CLR targeting may allow for cell-specific drug delivery and also the modulation of cellular functions. Glyconanoparticles, glycodendrimers, and glycoliposomes were successfully used as tools for CLR-specific targeting. This review will discuss different approaches for multivalent CLR ligand presentation and aims to highlight how CLR targeting has been employed for cell specific drug delivery. Major emphasis is directed towards targeting of CLRs expressed by antigen-presenting cells to modulate immune responses. PMID:23727341
Lepenies, Bernd; Lee, Junghoon; Sonkaria, Sanjiv
In a strategy to specifically target complement inhibitors to sites of complement activation and disease, recombinant fusion proteins consisting of a complement inhibitor linked to a C3 binding region of complement receptor (CR) 2 were prepared and characterized. Natural ligands for CR2 are C3 breakdown products deposited at sites of complement activation. Fusion proteins were prepared consisting of a human CR2 fragment linked to either the N terminus or C terminus of soluble forms of the membrane complement inhibitors decay accelerating factor (DAF) or CD59. The targeted complement inhibitors bound to C3-opsonized cells, and all were significantly more effective (up to 20-fold) than corresponding untargeted inhibitors at protecting target cells from complement. CR2 fusion proteins also inhibited CR3-dependent adhesion of U937 cells to C3 opsonized erythrocytes, indicating a second potential anti-inflammatory mechanism of CR2 fusion proteins, since CR3 is involved in endothelial adhesion and diapedesis of leukocytes at inflammatory sites. Finally, the in vivo validity of the targeting strategy was confirmed by the demonstration that CR2-DAF, but not soluble DAF, targets to the kidney in mouse models of lupus nephritis that are associated with renal complement deposition.
Song, Hongbin; He, Chun; Knaak, Christian; Guthridge, Joel M.; Holers, V. Michael; Tomlinson, Stephen
Background and objectives: Atypical hemolytic uremic syndrome (aHUS) is associated with a congenital or acquired dysregulation of the complement alternative pathway that leads to continuous complement activation on host cells causing inflammation and damage. Eculizumab, a humanized mAb against complement protein C5, inhibits activation of the terminal complement pathway. Design, setting, participants, & measurements: We report an adolescent with relapsing unclassified aHUS. On admission, a high plasma creatinine level indicated a poor prognosis, and hemodialysis had to be started. Plasma exchanges were initially effective against the microangiopathic hemolytic activity and allowed a temporary improvement of renal function with termination of hemodialysis after 7 wk. Subsequently, plasma exchanges (three times per week) failed to prevent ongoing aHUS activity and progressive renal failure. After 12 wk, aHUS treatment was switched to eculizumab. Results: Eculizumab was effective in terminating the microangiopathic hemolytic process in two aHUS relapses; however, after normalization of complement activity, aHUS recurred and ultimately led to anuric end-stage renal failure. Conclusions: In this patient, complement inhibition by eculizumab temporarily terminated the microangiopathic hemolytic activity. Nevertheless, renal damage as a result of preceding and subsequent aHUS activity resulted in end-stage renal failure; therefore, therapeutic success may depend on early administration of eculizumab. The optimal duration of treatment may be variable and remains to be determined.
Acham-Roschitz, Birgit; Fremeaux-Bacchi, Veronique; Kirschfink, Michael; Zipfel, Peter F.; Roedl, Siegfried; Vester, Udo; Ring, Ekkehard
A lectin (GLL-M) was isolated from mycelia of Ganoderma lucidum using affinity chromatography on BSM-Toyopearl. GLL-M is a monomer in its native form with a Mr of 18 000. Another lectin was also purified from fruiting bodies of the same fungus. The two lectins were partially compared with each other.
Hirokazu Kawagishi; Shin-Ichiro Mitsunaga; Masamichi Yamawaki; Mitoko Ido; Atsushi Shimada; Tetsuya Kinoshita; Takeomi Murata; Taichi Usui; Atsuo Kimura; Seiya Chiba
A Xenopus laevis egg cortical granule, calcium-dependent, galactosyl-specific lectin participates in forming the fertilization layer of the egg envelope and functions in establishing a block to polyspermy. We report the cDNA cloning of the lectin, expression of the cortical granule lectin gene during oogenesis and early development, and identification of a new family of lectins. The translated cDNA for the
Betty Y. Chang; Thomas R. Peavy; Nathan J. Wardrip; Jerry L. Hedrick
Nearly a century after the significance of the human complement system was recognized we have come to realize that its versatile functions extend far beyond the elimination of microbes. Indeed, complement acts as a rapid and efficient immune surveillance system that has distinct effects on healthy and altered host cells and foreign intruders. By eliminating cellular debris and infectious microbes, orchestrating immune responses, and sending `danger' signals, complement contributes substantially to homeostasis, but it may also take action against healthy cells if not properly controlled. This review describes our updated view of the function, structure, and dynamics of the complement network, highlights its interconnection with immunity at large and with other endogenous pathways, and illustrates its dual role in homeostasis and disease.
Ricklin, Daniel; Hajishengallis, George; Yang, Kun; Lambris, John D.
The acute lung injury (ALI) that occurs after the highly pathogenic avian influenza H5N1 virus infection is associated with an abnormal host innate immune response. Because the complement system plays a central role in innate immunity and because aberrant complement activation is associated with a variety of autoimmune and inflammatory diseases, we investigated the complement involvement in the pathogenesis of ALI induced by H5N1 virus infection. We showed that ALI in H5N1-infected mice was caused by excessive complement activation, as demonstrated by deposition of C3, C5b-9, and mannose-binding lectin (MBL)-C in lung tissue, and by up-regulation of MBL-associated serine protease-2 and the complement receptors C3aR and C5aR. Treatment of H5N1-infected mice with a C3aR antagonist led to significantly reduced inflammation in lungs, alleviating ALI. Furthermore, complement inhibition with an anti-C5a antibody or complement depletion with cobra venom factor after H5N1 challenge resulted in a similar level of protection to that seen in C3aR antagonist-treated mice. These results indicate that excessive complement activation plays an important role in mediating H5N1-induced ALI and that inhibition of complement may be an effective clinical intervention and adjunctive treatment for H5N1-induced ALI. PMID:23526211
Sun, Shihui; Zhao, Guangyu; Liu, Chenfeng; Wu, Xiaohong; Guo, Yan; Yu, Hong; Song, Hongbin; Du, Lanying; Jiang, Shibo; Guo, Renfeng; Tomlinson, Stephen; Zhou, Yusen
The complement system is a powerful part of the host innate immune defense and is aimed to damage and eliminate microbes and modified self-cells. To protect host cells and biological surfaces from damage mediated by complement activation products a tight control of the complement system is necessary. Imbalances in complement regulation contribute to tissue injury and can result in autoimmune diseases such as hemolytic uremic syndrome (HUS), membranoproliferative glomerulonephritis (MPGN) or age related macular degeneration (AMD). Disease associated mutations have been identified in several complement regulators or components, such as members of the factor H protein family. This group includes the major alternative pathway regulator, complement factor H (CFH) and five complement factor H related proteins (CFHR). Homozygous chromosomal deletion of a genomic 84 kb, chromosomal fragment which includes the genes CFHR1/CFHR3 is a risk factor for hemolytic uremic syndrome (HUS) at young age and is predominantly associated with the generation of autoantibodies to CFH, leading to a specific type of HUS, called DEAP (deficiency of CFHR and autoantibody positive)-HUS. The same deletion however is protective to the development of age related macular degeneration (AMD) in elderly people. Thus CFHR1 and CFHR3 proteins, and likely also the other members of this gene family are linked to human diseases. We here summarize the current knowledge about the role or association of CFHR1 and CFHR3 in the human diseases HUS and AMD. PMID:19388158
Skerka, Christine; Zipfel, Peter F
Equine recurrent uveitis serves as a spontaneous model for human autoimmune uveitis. Unpredictable relapses and ongoing inflammation in the eyes of diseased horses as well as in humans lead to destruction of the retina and finally result in blindness. However, the molecular mechanisms leading to inflammation and retinal degeneration are not well understood. An initial screening for differentially regulated proteins in sera of uveitic cases compared to healthy controls revealed an increase of the alternative pathway complement component factor B in ERU cases. To determine the activation status of the complement system, sera were subsequently examined for complement split products. We could demonstrate a significant higher concentration of the activation products B/Ba, B/Bb, Bb neoantigen, iC3b and C3d in uveitic condition compared to healthy controls, whereas for C5b-9 no differences were detected. Additionally, we investigated complement activation directly in the retina by immunohistochemistry, since it is the main target organ of this autoimmune disease. Interestingly, infiltrating cells co-expressed activated factor Bb neoantigen, complement split product C3d as well as CD68, a macrophage marker. In this study, we could demonstrate activation of the complement system both systemically as well as in the eye, the target organ of spontaneous recurrent uveitis. Based on these novel findings, we postulate a novel role for macrophages in connection with complement synthesis at the site of inflammation. PMID:20334949
Zipplies, Johanna K; Kirschfink, Michael; Amann, Barbara; Hauck, Stefanie M; Stangassinger, Manfred; Deeg, Cornelia A
C4 fulfills a vital role in the propagation of the classical and lectin pathways of the complement system. Although there are no reports to date of a C4 functional activity that is mediated solely by the C4d region, evidence clearly points to it having a vital role in a number of the properties of native C4 and its major activation fragment, C4b. Contained within the C4d region are the thioester-forming residues, the four isotype-specific residues controlling the C4A/C4B transacylation preferences, a binding site for nascent C3b important in assembling the classical pathway C5 convertase and determinants for the Chido/Rodgers (Ch/Rg) blood group antigens. In view of its functional importance, we undertook to determine the three-dimensional structure of C4d by X-ray crystallography. Here we report the 2.3A resolution structure of C4Ad, the C4d fragment derived from the human C4A isotype. Although the approximately 30% sequence identity between C4Ad and the corresponding fragment of C3 might be expected to establish a general fold similarity between the two molecules, C4Ad in fact displays a fold that is essentially superimposable on the structure of C3d. By contrast, the electrostatic characteristics of the various faces of the C4Ad molecule show marked differences from the corresponding faces of C3d, likely reflecting the differences in function between C3 and C4. Residues previously predicted to form the major Ch/Rg epitopes were proximately located and accessible on the concave surface of C4Ad. In addition to providing further insights on the current models for the covalent binding reaction, the C4Ad structure allows one to rationalize why C4d is not a ligand for complement receptor 2. Finally the structure allows for the visualization of the face of the molecule containing the binding site for C3b utilized in the assembly of classical pathway C5 convertase. PMID:12367531
van den Elsen, Jean M H; Martin, Alberto; Wong, Veronica; Clemenza, Liliana; Rose, David R; Isenman, David E
Genome-wide association studies (GWAS) promise a significant impact on the understanding of late-onset Alzheimer's disease (LOAD) as the genetic components have been estimated to account for 60-80% of the disease. The recent publication of results from large GWAS suggests that LOAD is now one of the best-understood complex disorders. Four recent large LOAD GWAS have resulted in the identification of nine novel loci. These genes are CLU--clusterin, PICALM--phosphatidylinositol-binding clathrin assembly protein, CR1--complement receptor 1, BIN1--bridging integrator 1, ABCA7--ATP-binding cassette transporter, MS4A cluster--membrane-spanning 4-domains subfamily A, CD2AP--CD2-associated protein, CD33--sialic acid-binding immunoglobulin-like lectin and EPHA1--ephrin receptor A1. Collectively, these genes now explain around 50% of LOAD genetics and map on to three new pathways linked to immune system function, cholesterol metabolism and synaptic cell membrane processes. These three new pathways are not strongly linked to the amyloid hypothesis that has driven so much recent thinking and open up avenues for intensive research with regard to the potential for therapeutic intervention. PMID:21486313
Lectins array is a powerfull and complementary method of glycans analysis allowing fast identification of specific motifs on molecules or cells. This technology is of increased interest for the development of therapeutic recombinant glycoproteins and particularly relevant for a first study of lot-to-lot comparison, or detection of unwanted glycans. In this chapter, we describe a lectin array-type method specifically designed for the study of recombinant therapeutic interleukin-7 (rhIL-7). This specific method allows the analysis of the glycans motifs, the distribution of the glycoforms population, and the detection of potential immunogen glycans in rhIL-7 purified CHO-produced batches. PMID:23475723
Landemarre, Ludovic; Duverger, Eric
Lectins play important roles in many biological processes, including protein trafficking, cell signaling, pathogen recognition, as effector molecules, and so on, because of their capacity to bind carbohydrates. Presently, seven groups of lectins have been identified in shrimp: C-type, L-type, P-type, M-type, fibrinogen-like domain lectins, galectins, and calnexin/calreticulin. These lectins have different structures, diverse expression patterns, and multiple functions in the shrimp immune response. This review summarizes the research progress and analyzes the diversity of shrimp lectins, focusing mainly on the C-type lectin family. Shrimp C-type lectins show considerable diversity in their domain architectures, sugar substrates, tissue distributions, expression patterns responding to pathogen challenge and functions in shrimp immunity. PMID:22561073
Wang, Xian-Wei; Wang, Jin-Xing
Loa loa is a filarial nematode that infects humans. The adults live in subcutaneous tissues and produce microfilariae that live for several weeks in the blood circulation in order to be transmitted to another person via blood meals of a dipterian vector. As microfilariae live in continuous contact with plasma, it is obvious that they evade the complement system. We studied markers of complement activation and signs of complement regulation on Loa loa microfilariae in vivo. The microfilariae were isolated from anticoagulated blood samples of a Loa loa-infected Caucasian patient. C1q and some mannose-binding lectin but only a limited amount of C3b or C4b fragments and practically no C5 or C5b-9 were present on the microfilariae. The covalently microfilaria-bound C3 and C4 depositions were mainly inactive iC3b, C3c, and iC4b fragments indicating that microfilariae had regulated complement activation in vivo. Also, in vitro deposition of C3b onto the microfilariae upon serum exposure was limited. The patient-isolated microfilariae were found to carry the host complement regulators factor H and C4b-binding protein on the outermost layer, so called sheath. The microfilaria-bound factor H was functionally active. Binding of the complement regulators to the microfilariae was confirmed in vitro using (125)I-labeled factor H and C4b-binding protein. In conclusion, our study shows that Loa loa microfilariae block complement activation and acquire the host complement regulators factor H and C4b-binding protein in blood circulation. This is the first time that binding of complement regulators onto nonviral pathogens has been demonstrated to occur in humans in vivo. PMID:19528206
Haapasalo, Karita; Meri, Taru; Jokiranta, T Sakari
Loa loa is a filarial nematode that infects humans. The adults live in subcutaneous tissues and produce microfilariae that live for several weeks in the blood circulation in order to be transmitted to another person via blood meals of a dipterian vector. As microfilariae live in continuous contact with plasma, it is obvious that they evade the complement system. We studied markers of complement activation and signs of complement regulation on Loa loa microfilariae in vivo. The microfilariae were isolated from anticoagulated blood samples of a Loa loa-infected Caucasian patient. C1q and some mannose-binding lectin but only a limited amount of C3b or C4b fragments and practically no C5 or C5b-9 were present on the microfilariae. The covalently microfilaria-bound C3 and C4 depositions were mainly inactive iC3b, C3c, and iC4b fragments indicating that microfilariae had regulated complement activation in vivo. Also, in vitro deposition of C3b onto the microfilariae upon serum exposure was limited. The patient-isolated microfilariae were found to carry the host complement regulators factor H and C4b-binding protein on the outermost layer, so called sheath. The microfilaria-bound factor H was functionally active. Binding of the complement regulators to the microfilariae was confirmed in vitro using 125I-labeled factor H and C4b-binding protein. In conclusion, our study shows that Loa loa microfilariae block complement activation and acquire the host complement regulators factor H and C4b-binding protein in blood circulation. This is the first time that binding of complement regulators onto nonviral pathogens has been demonstrated to occur in humans in vivo.
Haapasalo, Karita; Meri, Taru; Jokiranta, T. Sakari
Background Exposure to secondhand smoke during adulthood has detrimental health effects, including increased lung cancer risk. Compared with adults, children may be more susceptible to secondhand smoke. This susceptibility may be exacerbated by alterations in inherited genetic variants of innate immunity genes. We hypothesized a positive association between childhood secondhand smoke exposure and lung cancer risk that would be modified by genetic polymorphisms in the mannose binding lectin-2 (MBL2) gene resulting in well-known functional changes in innate immunity. Methods Childhood secondhand smoke exposure and lung cancer risk was assessed among men and women in the ongoing National Cancer Institute-Maryland Lung Cancer (NCI-MD) study, which included 624 cases and 348 controls. Secondhand smoke history was collected via in-person interviews. DNA was used for genotyping the MBL2 gene. To replicate, we used an independent case-control study from Mayo Clinic consisting of 461 never smokers, made up of 172 cases and 289 controls. All statistical tests were two-sided. Results In the NCI-MD study, secondhand smoke exposure during childhood was associated with increased lung cancer risk among never smokers [odds ratio (OR), 2.25; 95% confidence interval (95% CI), 1.04-4.90]. This was confirmed in the Mayo study (OR, 1.47; 95% CI, 1.00-2.15). A functional MBL2 haplotype associated with high circulating levels of MBL and increased MBL2 activity was associated with increased lung cancer risk among those exposed to childhood secondhand smoke in both the NCI-MD and Mayo studies (OR, 2.52; 95% CI, 1.13-5.60, and OR, 2.78; 95% CI, 1.18-3.85, respectively). Conclusions Secondhand smoke exposure during childhood is associated with increased lung cancer risk among never smokers, particularly among those possessing a haplotype corresponding to a known overactive complement pathway of the innate immune system.
Olivo-Marston, Susan E.; Yang, Ping; Mechanic, Leah E.; Bowman, Elise D.; Pine, Sharon R.; Loffredo, Christopher A.; Alberg, Anthony J.; Caporaso, Neil; Shields, Peter G.; Chanock, Stephen; Wu, Yanhong; Jiang, Ruoxiang; Cunningham, Julie; Jen, Jin; Harris, Curtis C.
Complement forms a key arm of innate immune defenses against gonococcal infection. Sialylation of gonococcal lipo-oligosaccharide, or expression of porin 1A (Por1A) protein, enables Neisseria gonorrhoeae to bind the alternative pathway complement inhibitor, factor H (fH), and evade killing by human complement. Using recombinant fH fragment-murine Fc fusion proteins, we localized two N. gonorrhoeae Por1A-binding regions in fH: one in
Jutamas Ngampasutadol; Sanjay Ram; Sunita Gulati; Sarika Agarwal; Chongqing Li; Alberto Visintin; Brian G. Monks; Guillermo E. Madico; Peter A. Rice
Factor D of the alternative pathway of human complement. Purification, alignment and N-terminal amino acid sequences of the major cyanogen bromide fragments, and localization of the serine residue at the active site.
The serine esterase factor D of the complement system was purified from outdated human plasma with a yield of 20% of the initial haemolytic activity found in serum. This represented an approx. 60 000-fold purification. The final product was homogeneous as judged by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis (with an apparent mol.wt. of 24 000), its migration as a single component in a variety of fractionation procedures based on size and charge, and its N-terminal amino-acid-sequence analysis. The N-terminal amino acid sequence of the first 36 residues of the intact molecule was found to be homologous with the N-terminal amino acid sequences of the catalytic chains of other serine esterases. Factor D showed an especially strong homology (greater than 60% identity) with rat 'group-specific protease' [Woodbury, Katunuma, Kobayashi, Titani, & Neurath (1978) Biochemistry 17, 811-819] over the first 16 amino acid residues. This similarity is of interest since it is considered that both enzymes may be synthesized in their active, rather than zymogen, forms. The three major CNBr fragments of factor D, which had apparent mol.wts. of 15 800, 6600 and 1700, were purified and then aligned by N-terminal amino acid sequence analysis and amino acid analysis. By using factor D labelled with di-[1,3-14C]isopropylphosphofluoridate it was shown that the CNBr fragment of apparent mol.wt. 6600, which is located in the C-terminal region of factor D, contained the active serine residue. The amino acid sequence around this residue was determined. Images Fig. 1. Fig. 2.
Johnson, D M; Gagnon, J; Reid, K B
The weak and variable binding affinities exhibited by lectin-carbohydrate interactions have often compromised the practical utility of lectin in capturing glycoproteins for glycoproteomic applications. We report here the development and applications of a new type of hybrid biomaterial, namely a boronic acid-decorated lectin (BAD-lectin), for efficient bifunctional glycoprotein labeling and enrichment. Our binding studies showed an enhanced affinity by BAD-lectin, likely to be mediated via the formation of boronate ester linkages between the lectin and glycan subsequent to the initial recognition process and thus preserving its glycan-specificity. Moreover, when attached to magnetic nanoparticles (BAD-lectin@MNPs), 2 to 60-fold improvement on detection sensitivity and enrichment efficiency for specific glycoproteins was observed over the independent use of either lectin or BA. Tested at the level of whole cell lysates for glycoproteomic applications, three different types of BAD-lectin@MNPs exhibited excellent specificities with only 6% overlapping among the 295 N-linked glycopeptides identified. As many as 236 N-linked glycopeptides (80%) were uniquely identified by one of the BAD-lectin@MNPs. These results indicated that the enhanced glycan-selective recognition and binding affinity of BAD-lectin@MNPs will facilitate a complementary identification of the under-explored glycoproteome. PMID:23895469
Lu, Ying-Wei; Chien, Chih-Wei; Lin, Po-Chiao; Huang, Li-De; Chen, Chang-Yang; Wu, Sz-Wei; Han, Chia-Li; Khoo, Kay-Hooi; Lin, Chun-Cheng; Chen, Yu-Ju
Protein-carbohydrate interaction is exploited in cell adhesion mechanisms besides the recognition of peptide motifs. The sugar code thus significantly contributes to the intriguing specificity of cellular selection of binding partners. Focusing on two classes of lectins (selectins and galectins), it is evident that their functionality for mediation of adhesive contacts is becoming increasingly appreciated, as is the integration of this
H. Kaltner; B. Stierstorfer
Mycelial- or spherule-phase derivatives of Coccidioides immitis caused a decrease in vitro of total hemolytic complement in serum from a nonsensitized person. Activation involved both classic and alternative pathways as shown by deprssion of hemolytic C4 and by generation of products of activation of components C3, C4, and factor B. In addition, functional complement activity or immunoreactive levels of complement components or both were measured in 23 patients with self-limited or disseminated coccidioidomycosis. Low total hemolytic complement was found in nine, usually during the early phase of primary illness, and was transient. Hemolytic C4 was low, and the effect of inulin to decrease complement levels was blunted, suggested both classic and alternative pathways may be deficient. However, associated depression of immunoreactive levels of components assayed (C3, C4, C5, factor B, and properdin) was not consistently found. This disparity raises the possibility of enhanced in vitro inactivation analogous to activation by immune complexes. Images Fig. 2
Galgiani, J N; Yam, P; Petz, L D; Williams, P L; Stevens, D A
Red blood cells (RBC) modified with biotin and streptavidin (SA) present an interesting potential drug delivery system. Biotinylation and SA attachment, however, alter the biocompatibility of RBC. We have reported that polyvalent SA attachment induces lysis of biotinylated RBC (b-RBC) by homologous complement via the alternative pathway. Lysis occurs due to inactivation of the membrane regulators of complement, DAF and
Vladimir R. Muzykantov; Juan C. Murciano; Ronald P. Taylor; Elena N. Atochina; Angel Herraez
|The protein complement pathway comprises an important part of the innate immunity. The use of serum to demonstrate complement-mediated destruction across a series of bacterial dilutions allows an instructor to introduce a number of important biological concepts such as bacterial growth, activation cascades, and adaptive versus innate immunity.|
Fuller, Kevin G.
Cyanovirin-N (CVN) is a cyanobacterial lectin with potent antiviral activity and has been the focus of extensive preclinical investigation as a potential prophylactic for the prevention of the sexual transmission of the human immunodeficiency virus (HIV). Here we present a detailed analysis of carbohydrate recognition by this important protein, using a combination of computational methods, including extensive molecular dynamics simulations and molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) energetic analysis. The simulation results strongly suggest that the observed tendency of wild-type CVN to form domain-swapped dimers is the result of a previously unidentified cis-peptide bond present in the monomeric state. The energetic analysis additionally indicates that the highest-affinity ligand for CVN characterized to date (?-Man-(1,2)-?-Man-(1,2)-?-Man) is recognized asymmetrically by the two binding sites. Finally, we are able to provide a detailed map of the role of all binding site functional groups (both backbone and side chain) to various aspects of molecular recognition: general affinity for cognate ligands, specificity for distinct oligosaccharide targets, and the asymmetric recognition of ?-Man-(1,2)-?-Man-(1,2)-?-Man. Taken as a whole, these results complement past experimental characterization (both structural and thermodynamic) to provide the most complete understanding of carbohydrate recognition by CVN to date. The results also provide strong support for the application of similar approaches to the understanding of other protein-carbohydrate complexes. PMID:23057413
Fujimoto, Yukiji K; Green, David F
Otitis media with effusion (OME) is a chronic inflammation persisting in the middle ear cavity of at least 8 weeks duration. Middle ear effusion (MEE; n = 38), samples from children suffering from OME were investigated for their direct cytolytic activity or an ability to enhance complement lysis of unsensitized bystander cells. Thirteen of the 38 MEEs had direct endogenous haemolytic activity and 27 samples had an ability to enhance serum-initiated lysis. Using an enzyme immunoassay, high levels of terminal complement complexes (TCC) were detected in the MEE samples (mean 34·1 µg/ml, range 5–89 µg/ml). This indicated strong local complement activation that had progressed to the terminal stage. As one potential factor promoting complement activation we identified both monomeric and trimeric properdin in MEE by Western blotting. By stabilizing C3 and C5 convertases properdin accelerates the alternative and terminal pathways of complement. On the other hand, the membrane attack complex (MAC) inhibitor CD59, which was found to be extensively shed into the MEE in a functionally active form, may control excessive cytotoxicity of the MEE. In conclusion, intense complement activation, up to the terminal level, maintains ongoing inflammation in the middle ear cavity and can pose a threat to the local epithelium.
Narkio-Makela, M; Meri, S
We investigated the importance of the host complement system in the pathogenesis of disease mediated by the intramacrophage pathogen Mycobacterium avium. Mycobacteria opsonized with complement are efficiently ingested by macrophages through various complement receptors. Furthermore, unlike other bacteria, mycobacteria can activate both the alternative and classical complement pathways in the absence of specific antibodies. Therefore, to examine the role of complement in the mycobacterial infection process in vivo, mice deficient in complement component C3 were infected with M. avium. Surprisingly, C3-deficient mice infected intravenously with M. avium displayed no difference in bacterial burden or granulomatous response compared to wild-type control mice. C3-sufficient mice and C3-deficient mice were equally susceptible to infection by M. avium regardless of the genotype at the bcg locus, a locus known to confer susceptibility to infection with intracellular pathogens. In vitro studies using mouse bone marrow-derived macrophages resulted in significant M. avium invasion of macrophages in the absence of C3; however, the kinetics of infection were delayed compared to complement-mediated invasion. The data indicate that complement does not play an essential role in mediating M. avium infections in the mouse and suggest either that other invasion mechanisms can compensate for the absence of complement-mediated entry or that complement is not a major mycobacterial opsonin in vivo.
Bohlson, Suzanne S.; Strasser, Jennifer A.; Bower, Jacquelyn J.; Schorey, Jeffrey S.
Although they lack a cell wall, mycoplasmas do possess a glycocalyx. The interactions between the glycocalyx, mycoplasmal surface proteins and host complement were explored using the murine pathogen Mycoplasma pulmonis as a model. It was previously shown that the length of the tandem repeat region of the surface lipoprotein Vsa is associated with susceptibility to complement-mediated killing. Cells producing a long Vsa containing about 40 repeats are resistant to complement, whereas strains that produce a short Vsa of five or fewer repeats are susceptible. We show here that the length of the Vsa protein modulates the affinity of the M. pulmonis EPS-I polysaccharide for the mycoplasma cell surface, with more EPS-I being associated with mycoplasmas producing a short Vsa protein. An examination of mutants that lack EPS-I revealed that planktonic mycoplasmas were highly susceptible to complement killing even when the Vsa protein was long, demonstrating that both EPS-I and Vsa length contribute to resistance. In contrast, the mycoplasmas were resistant to complement even in the absence of EPS-I when the cells were encased in a biofilm. PMID:22504437
Bolland, Jeffrey R; Simmons, Warren L; Daubenspeck, James M; Dybvig, Kevin
Bacillus anthracis was agglutinated by several lectins, including those from Griffonia simplicifolia, Glycine max, Abrus precatorius, and Ricinus communis. Some strains of Bacillus cereus var. mycoides (B. mycoides) were strongly reactive with the lectin from Helix pomatia and weakly reactive with the G. max lectin. The differential interactions between Bacillus species and lectins afforded a means of distinguishing B. anthracis from other bacilli. B. cereus strains exhibited heterogeneity with respect to agglutination patterns by lectins but could readily be differentiated from B. anthracis and the related B. mycoides. Spores of B. anthracis and B. mycoides retained lectin receptors, although the heating of spores or vegetative cells at 100 degrees C resulted in a decrease in their ability to be specifically agglutinated. Fluorescein-conjugated lectin of G. max stained vegetative cells of B. anthracis uniformly, suggesting that the distribution of lectin receptors was continuous over the entire cellular surface. B. anthracis cells grown under conditions to promote the production of capsular poly(D-glutamyl peptide) were also readily agglutinated by the lectins, suggesting that the lectin reactive sites penetrate the polypeptide layer. Trypsin, subtilisin, lysozyme, and mutanolysin did not modify the reactivity of B. anthracis with the G. max agglutinin, although the same enzymes markedly diminished the interaction between the lectin and B. mycoides. Because the lectins which interact with B. anthracis are specific for alpha-D-galactose or 2-acetamido-2-deoxy-alpha-D-galactose residues, it is likely that the bacteria possess cell surface polymers which contain these sugars. Lectins may prove useful in the laboratory identification of B. anthracis and possibly other pathogenic Bacillus species, such as B. cereus. Images
Cole, H B; Ezzell, J W; Keller, K F; Doyle, R J
Neisseria gonorrhoeae is an exclusive human pathogen that causes the sexually transmitted disease, gonorrhea. The gonococcus has developed an exquisite repertoire of mechanisms by which it is able to evade host innate and adaptive immune responses. Our previous data indicate that the predominately asymptomatic nature ofgonococcal cervicitis may, in part, be attributed to the ability of these bacteria to subvert the normal function of complement to promote cervical disease. Herein we describe the interaction of N. gonorrhoeae with the complement alternative pathway with a particular focus on the importance of this interaction in promoting gonococcal cervicitis. PMID:19388166
Edwards, Jennifer L
The complement system contains a great deal of biological "energy". This is demonstrated by the atypical hemolytic uremic syndrome (aHUS), which is a thrombotic microangiopathy (TMA) characterized by endothelial and blood cell damage and thrombotic vascular occlusions. Kidneys and often also other organs (brain, lungs and gastrointestinal tract) are affected. A principal pathophysiological feature in aHUS is a complement attack against endothelial cells and blood cells. This leads to platelet activation and aggregation, hemolysis, prothrombotic and inflammatory changes. The attacks can be triggered by infections, pregnancy, drugs or trauma. Complement-mediated aHUS is distinct from bacterial shiga-toxin (produced e.g. by E. coli O:157 or O:104 serotypes) induced "typical" HUS, thrombotic thrombocytopenic purpura (TTP) associated with ADAMTS13 (an adamalysin enzyme) dysfunction and from a recently described disease related to mutations in intracellular diacylglycerol kinase ? (DGKE). Mutations in proteins that regulate complement (factor H, factor I, MCP/CD46, thrombomodulin) or promote (C3, factor B) amplification of its alternative pathway or anti-factor H antibodies predispose to aHUS. The fundamental defect in aHUS is an excessive complement attack against cellular surfaces. This can be due to 1) an inability to regulate complement on self cell surfaces, 2) hyperactive C3 convertases or 3) complement activation and coagulation promoting changes on cell surfaces. The most common genetic cause is in factor H, where aHUS mutations disrupt its ability to recognize protective polyanions on surfaces where C3b has become attached. Most TMAs are thus characterized by misdirected complement activation affecting endothelial cell and platelet integrity. PMID:23743117
Complement is an innate immune response system that most animal viruses encounter during natural infections. We have tested the role of human complement in the neutralization of virus particles harboring the Nipah virus (NiV) glycoproteins. A luciferase-expressing vesicular stomatitis virus (VSV) pseudotype that contained the NiV fusion (F) and attachment (G) glycoproteins (NiVpp) showed dose- and time-dependent activation of human complement through the alternative pathway. In contrast to our findings with other paramyxoviruses, normal human serum (NHS) alone did not neutralize NiVpp infectivity in vitro, and electron microscopy demonstrated no significant deposition of complement component C3 on particles. This lack of NiVpp neutralization by NHS was not due to a global inhibition of complement pathways, since complement was found to significantly enhance neutralization by antibodies specific for the NiV F and G glycoproteins. Complement components C4 and C1q were necessary but not sufficient by themselves for the enhancement of antibody neutralization. Human complement also enhanced NiVpp neutralization by a soluble version of the NiV receptor EphrinB2, and this depended on components in the classical pathway. The ability of complement to enhance neutralization fell into one of two profiles: (i) anti-F monoclonal antibodies showed enhancement only at high and not low antibody concentrations, and (ii) anti-G monoclonal antibodies and EphrinB2 showed enhancement at both high and very low levels of antibody (e.g., 3.1 ng) or EphrinB2 (e.g., 2.5 ng). Together, these data establish the importance of human complement in the neutralization of particles containing the NiV glycoproteins and will help guide the design of more effective therapeutics that harness the potency of complement pathways.
Johnson, John B.; Aguilar, Hector C.; Lee, Benhur; Parks, Griffith D.
The release of immunoregulatory and inflammatory molecules following platelet activation has been invariably associated with the expression of tissue injury in several clinical conditions including trauma, organ transplantation, inflammatory bowel diseases and autoimmune diseases. We present a thorough review of the available information on the role of platelets and their interaction with complement cascade on the expression of tissue inflammation and organ damage. We propose that in autoimmune diseases and conditions associated with ischemia/reperfusion, platelets are decorated with complement, become activated and lodge tissues inappropriately to spread the inflammatory process. Interventions such as limiting complement decoration and suppression of signaling processes leading to platelet activation should be met with clinical benefit. PMID:22928713
Ioannou, Antonis; Kannan, Lakshmi; Tsokos, George C
Decay accelerating factor (DAF), membrane cofactor protein (MCP), complement receptor 1 and mouse Crry are cell surface-bound complement regulatory proteins capable of inhibiting C3 convertase activity on cell membranes, and therefore provide a substantial protection from attack by homologous complement activated either by the classical or by the alternative pathway. Decrease in complement regulatory activity might lead to spontaneous complement deposition and subsequent cell injury. MoAb 5I2 can inhibit the complement regulatory activity of molecules on rat cells, resulting in deposition of homologous complement. The antigen recognized by 5I2 MoAb in rats is homologous to mouse Crry. Fifteen to 20 h after infection with vaccinia virus, in vitro cultured KDH-8 rat hepatoma cells show a strong decrease in expression of Crry-like antigen, and proved to be sensitive to complement deposition when 1:5 diluted normal rat serum was added to the culture medium as a source of complement. Addition of complement to the cultured KDH-8 cells infected with a very low dose of vaccinia virus (1 plaque-forming unit (PFU)/1000 cells) substantially reduced spreading of virus infection in the cell culture, while inactivation of complement by heat or zymosan treatment abrogated the protective effect.
Baranyi, L; Okada, N; Baranji, K; Takizawa, H; Okada, H
Aims\\/hypothesis Diabetic nephropathy has been associated with low-grade inflammation and activation of the complement system in cross-sectional\\u000a studies. Data from prospective studies are sparse. We investigated the associations of the complement activator mannose-binding\\u000a lectin (MBL) and the inflammatory marker high-sensitivity C-reactive protein (hsCRP) with the development of nephropathy in\\u000a a large prospective study of patients with type 1 diabetes from the
T. K. Hansen; C. Forsblom; M. Saraheimo; L. Thorn; J. Wadén; P. Høyem; J. Østergaard; A. Flyvbjerg; P.-H. Groop
A mannose-binding lectin was isolated from rhizomes of the medicinal plantCurcuma zedoaria. We used extraction with 20 mM phosphate buffer, ammonium sulfate precipitation, ion exchange chromatography on Q-Sepharose,\\u000a gel filtration chromatography on Superdex 75, and reverse-phase HPLC. The purified lectin yielded a single band on SDS-PAGE\\u000a that corresponded to a molecular mass of 13 kDa. This lectin exhibited hemagglutinating activity
Ponpimol Tipthara; Polkit Sangvanich; Marcus Macth; Amorn Petsom
Transgenic plants containing cDNA encoding Gramineae lectin are described. The plants preferably contain cDNA coding for barley lectin and store the lectin in the leaves. The transgenic plants, particularly the leaves exhibit insecticidal and fungicidal properties. GOVERNMENT RIGHTS This application was funded under Department of Energy Contract DE-AC02-76ER01338. The U.S. Government has certain rights under this application and any patent issuing thereon. .
Brain inflammation is widely documented to occur in Alzheimer's disease (AD), but its sources are still incompletely understood. Here, we present in vitro and in situ evidence that, like amyloid beta peptide (Abeta), tau, the major protein constituent of the neurofibrillary tangle, is a potent, antibody-independent activator of the classical complement pathway. Complement activation, in turn, is known to drive numerous inflammatory responses, including scavenger cell activation and cytokine production. Because Abeta deposits and extracellular tangles are present from early preclinical to terminal stages of AD, their ability to activate complement provides a ready mechanism for initiating and sustaining chronic, low-level inflammatory responses that may cumulate over the disease course. PMID:11403931
Shen, Y; Lue, L; Yang, L; Roher, A; Kuo, Y; Strohmeyer, R; Goux, W J; Lee, V; Johnson, G V; Webster, S D; Cooper, N R; Bradt, B; Rogers, J
Amongst all leukemias, Bcr-Abl positive chronic myelogenous leukemia (CML) confers resistance to native drug due to multi drug resistance and also resistance to p53 and fas ligand pathways. In the present study, we have investigated the efficacy of microtubule stabilizing paclitaxel loaded magnetic nanoparticles (pac-MNPs) to ascertain its cytotoxic effect on Bcr-Abl positive K562 cells. For active targeted therapy, pac-MNPs were functionalized with lectin glycoprotein which resulted in higher cellular uptake and lower IC50 value suggesting the efficacy of targeted delivery of paclitaxel. Both pac-MNPs and lectin conjugated pac-MNPs have a prolonged circulation time in serum suggesting increased bioavailability and therapeutics index of paclitaxel in vivo. Further, the molecular mechanism pertaining to pac-induced cytotoxicity was analyzed by studying the involvement of different apoptotic pathway proteins by immunoblotting and quantitative PCR. Our study revealed simultaneous activation of JNK pathway leading to Bcr-Abl instability and the extrinsic apoptotic pathway after pac-MNPs treatment in two Bcr-Abl positive cell lines. In addition, the MRI data suggested the potential application of MNPs as imaging agent. Thus our in vitro and in vivo results strongly suggested the pac-MNPs as a future prospective theranostic tool for leukemia therapy.
Singh, Abhalaxmi; Dilnawaz, Fahima; Sahoo, Sanjeeb Kumar
A solubility-insolubility transition assay was used to screen the bark and stems of seven leguminous trees and plants for self-aggregatable lectins. Novel lectins were found in two trees, Robinia pseudoacacia and Wisteria floribunda, but not in the leguminous plants. The Robinia lectin was isolated from coexisting lectin by combined affinity chromatographies on various sugar adsorbents. The purified lectins proved to be differently glycosylated glycoproteins. One lectin exhibited the remarkable characteristics of self-aggregatable lectins: localization in the bark of legume trees, self-aggregation dissociated by N-acetylglucosamine/mannose, and coexistence with N-acetylgalactosamine/galactose-specific lectins, which are potential endogenous receptors. Self-aggregatable lectins are a functional lectin group that can link enhanced photosynthesis to dissociation of glycoproteins. PMID:16216416
Ina, Chieko; Sano, Kotone; Yamamoto-Takahashi, Makiko; Matsushita-Oikawa, Hiroko; Takekawa, Hiroko; Takehara, Yayoi; Ueda, Haruko; Ogawa, Haruko
Galanthus nivalis agglutinin-related lectins, a superfamily of strictly mannose-binding-specific lectins widespread amongst monotyledonous plants, have drawn a rising attention for their remarkable anti-proliferative and apoptosis-inducing activities toward various types of cancer cells; however, the precise molecular mechanisms by which they induce tumor cell apoptosis are still only rudimentarily understood. Herein, we found that the three conserved motifs "QXDXNXVXY," the mannose-specific binding sites, could mutate at one or more amino acid sites, which might be a driving force for the sequential evolution and thus ultimately leading to the complete disappearance of the three conserved motifs. In addition, we found that the motif evolution could result in the diversification of sugar-binding types that G. nivalis agglutinin-related lectins could bind from specific mannose receptors to more types of sugar-containing receptors in cancer cells. Subsequently, we indicated that some sugar-containing receptors such as TNFR1, EGFR, Hsp90, and Hsp70 could block downstream anti-apoptotic or survival signaling pathways, which, in turn, resulted in tumor cell apoptosis. Taken together, our hypothesis that carbohydrate-binding motif evolution may impact the G. nivalis agglutinin-related lectin-induced survival or anti-apoptotic pathways would provide a new perspective for further elucidating the intricate relationships between the carbohydrate-binding specificities and complex molecular mechanisms by which G. nivalis agglutinin-related lectins induce cancer cell death. PMID:21748493
Yu, Qi-Jia; Li, Zi-Yue; Yao, Shun; Ming, Miao; Wang, Shu-Ya; Liu, Bo; Bao, Jin-Ku
A deglycosylated derivative of tomato (Lycopersicon esculentum) lectin was prepared with the use of trifluoromethanesulphonic acid. Its properties were generally similar to those of the native lectin, but differences were evident in terms of relative agglutinating activity towards sheep, (untreated) human and trypsin-treated human erythrocytes. The two forms of tomato lectin were used in conjunction with a battery of specific antisera to investigate structural relatedness among solanaceous lectins. Immunological cross-reactivity between tomato, potato and Datura lectins depends on the integrity of the glycosylated region of those lectins; that between Datura lectin and other seed lectins, however, has a separate structural basis. Images Fig. 1.
Kilpatrick, D C; Graham, C; Urbaniak, S J; Jeffree, C E; Allen, A K
Infection with HIV represents a significant global health problem, with high infection rates and high mortality worldwide. Treatment with antiretroviral therapy is inaccessible to many patients and efficacy is limited by development of resistance and side effects. The interactions of HIV with the human immune system, both innate and humoral, are complex and complicated by the profound ability of the virus to disable the host immune response. Mannose-binding lectin, a component of the innate immune system, has been demonstrated to play a role in host-virus interactions. This protein may have a key role in determining host susceptibility to infection, pathogenesis and progression of disease, and may contribute to the extensive variability of host response to infection. Further understanding and manipulation of the mannose-binding lectin response may represent a target for immunomodulation in HIV infection, which may, in conjunction with highly active antiretroviral therapy, allow development of a novel therapeutic approach to HIV infection.
Eisen, Sarah; Dzwonek, Agnieszka; Klein, Nigel J
New research directions in the last decade have led to major developments in the uses of plant lectins in bioscience and biomedicine. Major advances have been made in our understanding how lectins in the diet can act on the gastrointestinal tract and the physiological consequences of their actions, and how they can modulate body- and organ metabolism, the immune system and the gut microflora. Particularly striking progress has been made in unravelling the effects, often beneficial, of both orally- and parenterally administered lectins, including lectins of Viscum album-, Phaseolus vulgaris-, Robinia pseudoacacia, Agaricus bisporus, etc on tumours and in cancer therapy. Results have also made it possible to devise and try out other beneficial applications of plant lectins as gut-, metabolic- and hormonal regulators, immune reagents, probiotic/prebiotic oral supplements and to develop methods based on the oral application of lectins to protect the intestines against the often lethally harmful effects of chemo- and radiotherapy. With the development of genetically modified (GM) plants by transferring the genes of some of the natural insecticidal lectins such as the various Bacillus thuringiensis lectin-Cry toxins or some insecticidal plant lectins to major crop plants, a possible new avenue in plant protection may have opened up. PMID:17981618
Pusztai, Arpad; Bardocz, Susan; Ewen, Stanley W B
Cell surface carbohydrates of Trypanosoma cruzi, Trypanosoma rangeli, and Trypanosoma conorhini were analyzed by a micro-agglutination assay employing 27 highly purified lectins and by binding assays using various /sup 125/I-labeled lectins. The following seven lectins discriminated between the trypanosomes: 1) tomato lectin (an N-acetyl-D-glucosamine-binding protein), both in purified form and as crude tomato juice; 2) Bauhinea purpurea and Sophora japonica lectins (both N-acetyl-D-galactosamine-binding proteins), which selectively agglutinated T. cruzi; 3) Vicia villosa (an N-acetyl-D-galactosamine-binding protein) which was specific for T. rangeli; 4) peanut lectin (a D-galactose-binding protein) both in purified form and as crude saline extract; and 5) Ulex europaeus and Lotus tetragonolobus (both L-fucose-binding proteins) lectins which reacted only with T. conorhini. Binding studies with 125I-labeled lectins were performed to find whether unagglutinated cells of the three different species of trypanosomes might have receptors for these lectins, in which case absence of agglutination could be due to a peculiar arrangement of the receptors. These assays essentially confirmed the agglutination experiments.
de Miranda Santos, I.K.; Pereira, M.E.
This study investigated and compared vascular actions of leguminous lectins obtained from the Canavalia genus (Canavalia brasiliensis, Canavalia gladiata, and Canavalia maritima) in the rat models of paw edema and isolated aorta. Paw edema was induced by subcutaneous injection of lectins (0.01-1 mg/kg) in animals pre-treated or not with indomethacin or L-NAME. In isolated aorta, cumulative concentration curves of C. gladiata or C. brasiliensis (1-100 microg/ml) were performed at the contraction plateau induced by phenylephrine or at tissue basal tonus. The mechanism of the lectin relaxant action was investigated by previous addition of L-NAME, indomethacin, or tetraethylammonium. In both models, the lectin domain involvement was evaluated by incubation of lectins with their ligand and non-ligand sugars. The lectins induced paw edema paralleled by protein leakage. The edematogenic activity elicited by C. gladiata and C. brasiliensis involves prostaglandins and nitric oxide (NO), while that of C. maritima occurs without NO interference. C. gladiata and C. brasiliensis elicited aorta relaxation involving NO and prostacyclin, while that of C. gladiata included EDHF. All lectin effects were prevented by their binding sugars. The present study demonstrated important vasodilator effects of different degrees and mechanisms in vivo and in vitro of Canavalia lectins. In vivo, the edematogenic activity was paralleled by plasma exudation, and in vitro, aorta relaxation was strictly dependent on intact endothelium. All effects occurred via interaction with lectin domains and participation of NO and/or prostanoids. PMID:19855960
Assreuy, Ana Maria Sampaio; Fontenele, Sabrina Rodrigues; Pires, Alana de Freitas; Fernandes, Débora Costa; Rodrigues, Natália Velloso Fontenelle C; Bezerra, Eduardo Henrique Salviano; Moura, Tales Rocha; do Nascimento, Kyria Santiago; Cavada, Benildo Sousa
The mucosal immunogenicity of a number of plant lectins with different sugar specificities was investigated in mice. Following intranasal (i.n.) or oral administration, the systemic and mucosal antibody responses elicited were compared with those induced by a potent mucosal immunogen (cholera toxin; CT) and a poorly immunogenic protein (ovalbumin; OVA). After three oral or i.n. doses of CT, high levels of specific serum antibodies were measured and specific IgA was detected in the serum, saliva, vaginal wash, nasal wash and gut wash of mice. Immunization with OVA elicited low titres of serum IgG but specific IgA was not detected in mucosal secretions. Both oral and i.n. delivery of all five plant lectins investigated [Viscum album (mistletoe lectin 1; ML?1), Lycospersicum esculentum (tomato lectin; LEA), Phaseolus vulgaris (PHA), Triticum vulgaris (wheat germ agglutinin (WGA), Ulex europaeus I (UEA?1)] stimulated the production of specific serum IgG and IgA antibody after three i.n. or oral doses. Immunization with ML?1 induced high titres of serum IgG and IgA in addition to specific IgA in mucosal secretions. The response to orally delivered ML?1 was comparable to that induced by CT, although a 10?fold higher dose was administered. Immunization with LEA also induced high titres of serum IgG, particularly after i.n. delivery. Low specific IgA titres were also detected to LEA in mucosal secretions. Responses to PHA, WGA and UEA?1 were measured at a relatively low level in the serum, and little or no specific mucosal IgA was detected.
Lavelle, E C; Grant, G; Pusztai, A; Pfuller, U; O'Hagan, D T
Most fish embryos that develop externally are exposed to an environment full of microbes. How they survive microbial attacks are not understood to date. Here we demonstrated that the egg cytosol prepared from the newly fertilized eggs of zebrafish Danio rerio is capable of killing the Gram-negative bacterium Escherichia coli, via in vitro assay system of the complement activity established. All findings indicate that it is the complement system operating via the alternative pathway that is attributable to the bacteriolytic activity. This is the first report providing the evidence for the functional role of the maternal complement components in fish eggs, paving the way for study of maternal immunity in other organisms whose eggs are fertilized in vitro.
Wang, Zhiping; Zhang, Shicui; Wang, Guangfeng; An, Yan
The development and use of topical microbicides potentially offers an additional strategy to reduce the spread of the Human Immunodeficiency Virus (HIV). Carbohydrate-binding agents (CBAs) that show specificity for high mannose carbohydrates on the surface of the heavily glycosylated envelope of HIV are endowed with potent anti-HIV activity. In fact, a number of algal lectins such as cyanovirin-N, microvirin, microcystis viridis lectin, scytovirin, Oscillatoria agardhii agglutinin and griffithsin are considered as potential microbicide candidates to prevent the sexual transmission of HIV through topical applications. They not only inhibit infection of cells by cell-free virus but they can also efficiently prevent virus transmission from virus-infected cells to uninfected CD4(+) target T-lymphocytes and DC-SIGN-directed capture of HIV-1 and transmission to CD4(+) T lymphocytes. This review focuses on the structural properties and carbohydrate specificity of these algal lectins, their antiviral activity against HIV and several other enveloped viruses, their safety profile and viral resistance patterns. PMID:22851920
Huskens, Dana; Schols, Dominique
The development and use of topical microbicides potentially offers an additional strategy to reduce the spread of the Human Immunodeficiency Virus (HIV). Carbohydrate-binding agents (CBAs) that show specificity for high mannose carbohydrates on the surface of the heavily glycosylated envelope of HIV are endowed with potent anti-HIV activity. In fact, a number of algal lectins such as cyanovirin-N, microvirin, microcystis viridis lectin, scytovirin, Oscillatoria agardhii agglutinin and griffithsin are considered as potential microbicide candidates to prevent the sexual transmission of HIV through topical applications. They not only inhibit infection of cells by cell-free virus but they can also efficiently prevent virus transmission from virus-infected cells to uninfected CD4+ target T-lymphocytes and DC-SIGN-directed capture of HIV-1 and transmission to CD4+ T lymphocytes. This review focuses on the structural properties and carbohydrate specificity of these algal lectins, their antiviral activity against HIV and several other enveloped viruses, their safety profile and viral resistance patterns.
Huskens, Dana; Schols, Dominique
Plasma levels of selected proteins of coagulation, fibrinolysis and complement from patients with septic shock have been investigated. All values were corrected on the basis of a plasma protein content of 5.5%. Considerable decreases were found in the plasma levels of the contact factors activity. The antigen content in the case of HMW-kininogen remained in the normal range, whereas in the case of prekallikrein it dropped to about 30% of norm. Considering the proteins of the unspecific defense and the complement system, primarily HRG, alpha 2-macroglobulin and C4 showed remarkable decreases. From the changes of the plasma levels of the considered proteins one can conclude that in septic shock primarily the contact phase of coagulation and the alternative pathway of complement are involved. The consumption of F XIII points to a thrombin generation during shock. The marked reduction of the C4-component could be due to an isolated proteolysis of this component, since the classical pathway of complement activation seems not to be involved in the shock events. Serial controls of the plasma levels of the proteins under investigation showed in some patients considerable individual deviations from the general trend. A considerable increase of the F XIII A level appears to be a prognostically favorable result, whereas constantly low values of F XIII and fibronectin without a tendency to normalization or a constant decrease of these proteins often is connected with a fatal outcome. PMID:3718404
Karges, H E; Egbring, R; Merte, D
The complement system is an important defense system of innate immunity. The recent identification of structurally and functionally related complement regulatory proteins in the teleost, barred sand bass (Paralabrax nebulifer), and humans, two species which are separated in evolution by 100 million years, indicates a high level of conservation and the early presence of this defense system in evolution. The complement regulatory protein of barred sand bass, SBP1, is related to both the human alternative pathway regulator factor H, and to the classical pathway regulator C4bp, and displays regulatory activities in both human pathways. In addition, molecules with homology to the recently identified human factor-H-related proteins are also present in the sand bass genome. Here, we summarize the structural and functional aspects of these homologies and discuss the consequences for the evolution of the complement system. PMID:10810221
Kemper, C; Gigli, I; Zipfel, P F
We describe here a simple, general procedure for the purification of a variety of lectins, and for the preparation of lectin-ferritin conjugates of defined molar composition and binding properties to be used as probes for cell surface saccharides. The technique uses a "universal" affinity column for lectins and their conjugates, which consists of hog sulfated gastric mucin glycopeptides covalently coupled to agarose. The procedure involes: (a) purification of lectins by chromatography of aqueous extracts of seeds or other lectin-containing fluids over the affinity column, followed by desorption of the desired lectin with its hapten suge; (b) iodination of the lectin to serve as a marker during subsequent steps; (c) conjugation of lectin to ferritin with glutaraldehyde; (d) collection of active lectin-ferritin conjugates by affinity chromatography; and (e) separation of monomeric lectin-ferritin conjugates from larger aggregates and unconjugated lectin by gel chromatography. Based on radioactivity and absorbancy at 310 nm for lectin and ferritin, respectively, the conjugates consist of one to two molecules of lectin per ferrritin molecule. Binding studies of native lectins and their ferritin conjugates to dispersed pancreatic acinar cells showed that the conjugation procedure does not significantly alter either the affinity constant of the lectin for its receptor on the cell surface or the number of sites detected. PMID:422653
Maylié-Pfenninger, M F; Jamieson, J D
Studies over the past three decades have clearly established a central role for complement in the promotion of a humoral immune response. The primary function of complement, in this regard, is to opsonize antigen or immune complexes for uptake by complement receptor type 2 (CR2, CD21) expressed on B cells, follicular dendritic cells (FDC) and some T cells. A variety of mechanisms appear to be involved in complement-mediated promotion of the humoral response. These include: enhancement of antigen (Ag) uptake and processing by both Ag-specific and non-specific B cells for presentation to specific T cells; the activation of a CD21/CD19 complex-mediated signalling pathway in B cells, which provides a stimulus synergistic to that induced by antigen interaction with the B-cell receptor (BCR); and promotion of the interaction between B cells and FDC, where C3d-bearing immune complexes participate in intercellular bridging. Finally, current studies suggest that CR2 may also play a role in the determination of B-cell tolerance towards self-antigens and thereby hold the key to the previously observed correlation between deficiencies of the early complement components and autoimmune disease.
Nielsen, C H; Fischer, E M; Leslie, R G Q
Complement inflammation is a major inflammatory mechanism whose function is to promote the removal of microorganisms and the processing of immune complexes. Numerous studies have provided evidence for an increase in this process in areas of pathology in the Alzheimer's disease (AD) brain. Because complement activation proteins have been demonstrated in vitro to exert both neuroprotective and neurotoxic effects, the significance of this process in the development and progression of AD is unclear. Studies in animal models of AD, in which brain complement activation can be experimentally altered, should be of value for clarifying this issue. However, surprisingly little is known about complement activation in the transgenic animal models that are popular for studying this disorder. An optimal animal model for studying the significance of complement activation on Alzheimer's – related neuropathology should have complete complement activation associated with senile plaques, neurofibrillary tangles (if present), and dystrophic neurites. Other desirable features include both classical and alternative pathway activation, increased neuronal synthesis of native complement proteins, and evidence for an increase in complement activation prior to the development of extensive pathology. In order to determine the suitability of different animal models for studying the role of complement activation in AD, the extent of complement activation and its association with neuropathology in these models must be understood.
Loeffler, David A
Objectives In vitro, microparticles can activate complement via the classical pathway. If demonstrable ex vivo, this mechanism may contribute to the pathogenesis of rheumatoid arthritis (RA). We therefore investigated the presence of activated complement components and complement activator molecules on the surface of cell?derived microparticles of RA patients and healthy individuals. Methods Microparticles from synovial fluid (n?=?8) and plasma (n?=?9) of 10 RA patients and plasma of sex? and age?matched healthy individuals (n?=?10) were analysed by flow cytometry for bound complement components (C1q, C4, C3) and complement activator molecules (C?reactive protein (CRP), serum amyloid P component (SAP), immunoglobulin (Ig) M, IgG). Results Microparticles with bound C1q, C4, and/or C3 were abundant in RA synovial fluid, while in RA and control plasma much lower levels were present. Microparticles with bound C1q correlated with those with bound C3 in synovial fluid (r?=?0.961, p?=?0.0001), and with those with bound C4 in plasma (RA: r?=?0.908, p?=?0.0007; control: r?=?0.632, p?=?0.0498), indicating classical pathway activation. In synovial fluid, microparticles with IgM and IgG correlated with those with C1q (r?=?0.728, p?=?0.0408; r?=?0.952, p?=?0.0003, respectively), and in plasma, microparticles with CRP correlated with those with C1q (RA: r?=?0.903, p?=?0.0021; control: r?=?0.683, p?=?0.0296), implicating IgG and IgM in the classical pathway activation in RA synovial fluid, and CRP in the low level classical pathway activation in plasma. Conclusions This study demonstrates the presence of bound complement components and activator molecules on microparticles ex vivo, and supports their role in low grade complement activation in plasma and increased complement activation in RA synovial fluid.
Biro, Eva; Nieuwland, Rienk; Tak, Paul P; Pronk, Loes M; Schaap, Marianne C L; Sturk, Augueste; Hack, C Erik
The alternative pathway of the complement cascade plays a role in the pathogenesis of dense deposit disease (DDD). Deficiency of complement factor H and mutations in CFH associate with the development of DDD, but it is unknown whether allelic variants in other complement genes also associate with this disease. We studied patients with DDD and identified previously unreported sequence alterations in several genes in addition to allelic variants and haplotypes common to patients with DDD. We found that the likelihood of developing DDD increases with the presence of two or more risk alleles in CFH and C3. To determine the functional consequence of this finding, we measured the activity of the alternative pathway in serum samples from phenotypically normal controls genotyped for variants in CFH and C3. Alternative pathway activity was higher in the presence of variants associated with DDD. Taken together, these data confirm that DDD is a complex genetic disease and may provide targets for the development of disease-specific therapies.
Abrera-Abeleda, Maria Asuncion; Nishimura, Carla; Frees, Kathy; Jones, Michael; Maga, Tara; Katz, Louis M.; Zhang, Yuzhou
Plant lectins, a unique group of proteins and glycoproteins with potent biological activity, occur in foods like wheat, corn, tomato, peanut, kidney bean, banana, pea, lentil, soybean, mushroom, rice, and potato. Thus, dietary intakes by humans can be significant. Many lectins resist digestion, survive gut passage, and bind to gastrointestinal cells and\\/or enter the circulation intact, maintaining full biological activity.
Elvira González De Mejía; Valentin I. Prisecaru
A limited number of carotenoid pathway genes from microbial sources have been studied for analyzing the pathway complementation in the heterologous host Escherichia coli. In order to systematically investigate the functionality of carotenoid pathway enzymes in E. coli, the pathway genes of carotenogenic microorganisms (Brevibacterium linens, Corynebacterium glutamicum, Rhodobacter sphaeroides, Rhodobacter capsulatus, Rhodopirellula baltica, and Pantoea ananatis) were modified to form synthetic expression modules and then were complemented with Pantoea agglomerans pathway enzymes (CrtE, CrtB, CrtI, CrtY, and CrtZ). The carotenogenic pathway enzymes in the synthetic modules showed unusual activities when complemented with E. coli. For example, the expression of heterologous CrtEs of B. linens, C. glutamicum, and R. baltica influenced P. agglomerans CrtI to convert its substrate phytoene into a rare product-3,4,3',4'-tetradehydrolycopene-along with lycopene, which was an expected product, indicating that CrtE, the first enzyme in the carotenoid biosynthesis pathway, can influence carotenoid profiles. In addition, CrtIs of R. sphaeroides and R. capsulatus converted phytoene into an unusual lycopene as well as into neurosporene. Thus, this study shows that the functional complementation of pathway enzymes from different sources is a useful methodology for diversifying biosynthesis as nature does. PMID:23144136
Song, Gyu Hyeon; Kim, Se Hyeuk; Choi, Bo Hyun; Han, Se Jong; Lee, Pyung Cheon
Alzheimer's disease (AD) and age-related macular degeneration (AMD) are both neurodegenerative disorders which share common pathological and biochemical features of the complement pathway. The aim of this study was to investigate whether there is an association between well replicated AMD genetic risk factors and AD. A large cohort of AD (n = 3898) patients and controls were genotyped for single nucleotide polymorphisms (SNPs) in the complement factor H (CFH), the Age-related maculopathy susceptibility protein 2 (ARMS2) the complement component 2 (C2), the complement factor B (CFB), and the complement component 3 (C3) genes. While significant but modest associations were identified between the complement factor H, the age-related maculopathy susceptibility protein 2, and the complement component 3 single nucleotide polymorphisms and AD, these were different in direction or genetic model to that observed in AMD. In addition the multilocus genetic model that predicts around a half of the sibling risk for AMD does not predict risk for AD. Our study provides further support to the hypothesis that while activation of the alternative complement pathway is central to AMD pathogenesis, it is less involved in AD. PMID:22300950
Proitsi, Petroula; Lupton, Michelle K; Dudbridge, Frank; Tsolaki, Magda; Hamilton, Gillian; Daniilidou, Makrina; Pritchard, Megan; Lord, Kathryn; Martin, Belinda M; Johnson, Janet; Craig, David; Todd, Stephen; McGuinness, Bernadette; Hollingworth, Paul; Harold, Denise; Kloszewska, Iwona; Soininen, Hilkka; Mecocci, Patrizia; Velas, Bruno; Gill, Michael; Lawlor, Brian; Rubinsztein, David C; Brayne, Carol; Passmore, Peter A; Williams, Julie; Lovestone, Simon; Powell, John F
Marine bioresources produce a great variety of specific and potent bioactive molecules including natural organic compounds such as fatty acids, polysaccharides, polyether, peptides, proteins, and enzymes. Lectins are also one of the promising candidates for useful therapeutic agents because they can recognize the specific carbohydrate structures such as proteoglycans, glycoproteins, and glycolipids, resulting in the regulation of various cells via glycoconjugates and their physiological and pathological phenomenon through the host-pathogen interactions and cell-cell communications. Here, we review the multiple lectins from marine resources including fishes and sea invertebrate in terms of their structure-activity relationships and molecular evolution. Especially, we focus on the unique structural properties and molecular evolution of C-type lectins, galectin, F-type lectin, and rhamnose-binding lectin families.
Ogawa, Tomohisa; Watanabe, Mizuki; Naganuma, Takako; Muramoto, Koji
Entamoeba histolytica is an intestinal parasite that causes dysentery and liver abscess. Parasite cell surface receptors, such as the Gal/GalNAc lectin, facilitate attachment to host cells and extracellular matrix. The Gal/GalNAc lectin binds to galactose or N-acetylgalactosamine residues on host components and is composed of heavy (Hgl), intermediate (Igl), and light (Lgl) subunits. Although Igl is constitutively localized to lipid rafts (cholesterol-rich membrane domains), Hgl and Lgl transiently associate with this compartment in a cholesterol-dependent fashion. In this study, trophozoites were exposed to biologically relevant ligands to determine if ligand binding influences the submembrane distribution of the subunits. Exposure to human red blood cells (hRBCs) or collagen, which are bona fide Gal/GalNAc lectin ligands, was correlated with enrichment of Hgl and Lgl in rafts. This enrichment was abrogated in the presence of galactose, suggesting that direct lectin-ligand interactions are necessary to influence subunit location. Using a cell line that is able to attach to, but not phagocytose, hRBCs, it was shown that physical attachment to ligands was not sufficient to induce the enrichment of lectin subunits in rafts. Additionally, the mutant had lower levels of phosphatidylinositol (4,5)-bisphosphate (PIP2); PIP2 loading restored the ability of this mutant to respond to ligands with enrichment of subunits in rafts. Finally, intracellular calcium levels increased upon attachment to collagen; this increase was essential for the enrichment of lectin subunits in rafts. Together, these data provide evidence that ligand-induced enrichment of lectin subunits in rafts may be the first step in a signaling pathway that involves both PIP2 and calcium signaling.
Goldston, Amanda M.; Powell, Rhonda R.; Koushik, Amrita B.
The behaviour of the complement system during human reproduction is now the focus of much scientific attention. The presence\\u000a of antisperm antibodies in the reproductive tracts of some infertile individuals, and of complement in cervical and ovarian\\u000a follicular fluid, suggests that complement-mediated damage of spermatozoa is involved in some cases of infertility. Further,\\u000a deposition of maternal IgG and of complement
Isabelle A. Rooney; Teresa J. Oglesby; John P. Atkinson
Mannose-binding lectin (MBL) targets diverse microorganisms for phagocytosis and complement-mediated lysis by binding specific surface glycans. Although recombinant human MBL (rhMBL) trials have focused on reconstitution therapy, safety studies have identified no barriers to its use at higher levels. Ebola viruses cause fatal hemorrhagic fevers for which no treatment exists and that are feared as potential biothreat agents. We found that mice whose rhMBL serum concentrations were increased ?7-fold above average human levels survived otherwise fatal Ebola virus infections and became immune to virus rechallenge. Because Ebola glycoproteins potentially model other glycosylated viruses, rhMBL may offer a novel broad-spectrum antiviral approach.
Michelow, Ian C.; Lear, Calli; Scully, Corinne; Prugar, Laura I.; Longley, Clifford B.; Yantosca, L. Michael; Ji, Xin; Karpel, Marshall; Brudner, Matthew; Takahashi, Kazue; Spear, Gregory T.; Ezekowitz, R. Alan B.; Olinger, Gene G.
Ficolins and mannan-binding lectins (MBLs) are the first components of the lectin branch of the complement system. They comprise N-terminal collagen-like domains and C-terminal pathogen-recognition domains (fibrinogen-like domains in ficolins and C-type carbohydrate-recognition domains in MBLs), which target surface-exposed N-acetyl groups or mannose-like sugars on microbial cell walls. Binding leads to activation of MBL-associated-serine protease-2 (MASP-2) to initiate complement activation and pathogen neutralisation. Recent studies have shown that MASP-2 binds to a short segment of the collagen-like domain of MBL. However, the interaction between ficolins and MASP-2 is relatively poorly understood. In this study, we show that the MASP-2 binding site on rat ficolin-A is also located within the collagen-like domain and encompasses a conserved motif that is present in both MBLs and ficolins. Characterisation of this motif using site-directed mutagenesis reveals that a lysine residue in the X position of the Gly-X-Y collagen repeat, (Lys56 in ficolin-A) which is present in all ficolins and MBLs known to activate complement, is essential for MASP-2 binding. Adjacent residues also make important contributions to binding as well as to MASP activation probably by stabilizing the local collagen helix. Equivalent binding sites and comparable activation kinetics of MASP-2 suggest that complement activation by ficolins and MBLs proceeds by analogous mechanisms.
Girija, Umakhanth Venkatraman; Dodds, Alister W.; Roscher, Silke; Reid, Kenneth B. M.; Wallis, Russell
A mannose (Man)-binding lectin has been isolated and characterized from the thallus of the liverwort Marchantia polymorpha. N-terminal sequencing indicated that the M. polymorpha agglutinin (Marpola) shares sequence similarity with the superfamily of monocot Man-binding lectins. Searches in the databases yielded expressed sequence tags encoding Marpola. Sequence analysis, molecular modeling, and docking experiments revealed striking structural similarities between Marpola and the monocot Man-binding lectins. Activity and specificity studies further indicated that Marpola is a much stronger agglutinin than the Galanthus nivalis agglutinin and exhibits a preference for methylated Man and glucose, which is unprecedented within the family of monocot Man-binding lectins. The discovery of Marpola allows us, for the first time, to corroborate the evolutionary relationship between a lectin from a lower plant and a well-established lectin family from flowering plants. In addition, the identification of Marpola sheds a new light on the molecular evolution of the superfamily of monocot Man-binding lectins. Beside evolutionary considerations, the occurrence of a G. nivalis agglutinin homolog in a lower plant necessitates the rethinking of the physiological role of the whole family of monocot Man-binding lectins.
Peumans, Willy J.; Barre, Annick; Bras, Julien; Rouge, Pierre; Proost, Paul; Van Damme, Els J.M.
Lectin-related polypeptides are a class of defence proteins found in seeds of Phaseolus species. In Lima bean (P. lunatus), these proteins and their genes have been well characterized in the Andean morphotype, which represents one of the two gene pools of this species. To study the molecular evolution of the lectin family in Lima bean we characterized the polypeptides belonging to
Francesca Sparvoli; Cecilia Lanave; Annalisa Santucci; Roberto Bollini; Lucia Lioi
The complement system is important for host resistance to hematogenously disseminated candidiasis. However, modulation of complement activation by cell wall components of Candida albicans has not been characterized. Although intact yeast display mannan on the surface, glucan, typically located in the interior, becomes exposed during C. albicans infection. We show here the distinct effects of mannan and glucan on complement activation and opsonophagocytosis. Previous studies showed that intact cells are resistant to initiation of complement activation through the alternative pathway, and antimannan antibody reverses this resistance via an Fc-independent mechanism. The present study shows that this mannan-dependent resistance can be overcome by periodate-borohydride conversion of mannose polysaccharides to polyalcohols; cells treated with periodate-borohydride initiate the alternative pathway without the need for antibody. These observations identify an inhibitory role for intact mannan in complement activation. Next, removal of the surface-displayed mannan by acid treatment of periodate-borohydride cells exposes glucan. Glucan-displaying cells or purified ?-glucan initiate the alternative pathway when incubated with the purified proteins of the alternative pathway alone, suggesting that C. albicans glucan is a natural activator of the alternative pathway. Finally, ingestion of mannan-displaying cells by human neutrophils requires anti-mannan antibody, whereas ingestion of glucan-displaying cells requires complement. These results demonstrate a contrasting requirement of natural antibody and complement for opsonophagocytosis of C. albicans cells displaying mannan or glucan. Thus, differential surface expression of mannan and glucan may influence recognition of C. albicans by the complement system.
Boxx, Gayle M.; Kozel, Thomas R.; Nishiya, Casey T.; Zhang, Mason X.
Oral exposure to lectins or the presence or absence of bacteria in the rat small intestine were shown by histological methods using anti-lectin antibodies or digoxigenin-labelled lectins to have major effects on the state of glycosylation of lumenal membranes and cytoplasmic glycoconjugates of epithelial cells. Taken together with the dramatic effects of exposure to lectins on gut function, metabolism and
Arpad Pusztai; Stanley W. B. Ewen; George Grant; Willy J. Peumans; ELS J. M. VAN DAMME; Marie E. Coates; Susan Bardocz
The complement system has been implicated as both a pathogenic mechanism and a means of protection in periodontal diseases. It is well known that bacteria activate complement; such activation can initiate a number of events, including bacterial opsonization and killing, release of inflammatory agents, and modulation of other immune reactions. Cleavage of complement proteins has been observed in gingival fluids
Harvey A. Schenkein
Introduction There is a growing body of evidence implicating aberrant dendritic cell function as a crucial component in the immunopathogenesis of systemic lupus erythematosus. The purpose of the present study was to characterize the phagocytic capacity and expression of receptors involved in pathogen recognition and self-nonself discrimination on myeloid dendritic cells from patients with lupus. Methods Unstimulated or stimulated monocyte-derived dendritic cells were obtained from lupus patients and healthy control individuals, and expression of C-type lectin receptors (mannose receptor and dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin), complement-receptor 3 and Fc? receptors was determined by flow cytometry. Dextran uptake by lupus and control dendritic cells was also assessed by flow cytometry. Serum IFN? was quantified by ELISA, and uptake of microbial products was measured using fluorescently labeled zymosan. Results When compared with dendritic cells from healthy control individuals, unstimulated and stimulated lupus dendritic cells displayed significantly decreased dextran uptake and mannose receptor and dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin expression. Decreased expression of the mannose receptor was associated with high serum IFN? levels, but not with maturation status or medications. Diminished dextran uptake and mannose receptor expression correlated with lupus disease activity. There were no differences between control and lupus dendritic cells in the expression of other pattern recognition receptors or in the capacity to uptake zymosan particles Conclusions Lupus dendritic cells have diminished endocytic capacity, which correlates with decreased mannose receptor expression. While this phenomenon appears primarily intrinsic to dendritic cells, modulation by serum factors such as IFN? could play a role. These abnormalities may be relevant to the aberrant immune homeostasis and the increased susceptibility to infections described in lupus.
Monrad, Seetha U; Rea, Kristine; Thacker, Seth; Kaplan, Mariana J
Fluorescein labeled carbohydrate (Glyc) probes were synthesized as analytical tools for the study of cellular lectins, i.e. SiaLe x-PAA-flu, Sia 2-PAA-flu, GlcNAc 2-PAA-flu, LacNAc-PAA-flu and a number of similar ones, with PAA a soluble polyacrylamide carrier. The binding of SiaLe x-PAA-flu was assessed using CHO cells transfected with E-selectin, and the binding of Sia 2-PAA-flu was assessed by COS cells transfected with siglec-9. In flow cytometry assays, the fluorescein probes demonstrated a specific binding to the lectin-transfected cells that was inhibited by unlabeled carbohydrate ligands. The intense binding of SiaLe x-PAA- 3H to the E-selectin transfected cells and the lack of binding to both native and permeabilized control cells lead to the conclusion that the polyacrylamide carrier itself and the spacer arm connecting the carbohydrate moiety with PAA did not contribute anymore to the binding. Tumors were obtained from nude mice by injection of CHO E-selectin or mock transfected cells. The fluorescent SiaLe x-PAA-flu probe could bind to the tumor sections from E-selectin positive CHO cells, but not from the control ones. Thus, these probes can be used to reveal specifically the carbohydrate binding sites on cells in culture as well as cells in tissue sections. The use of the confocal spectral imaging technique with Glyc-PAA-flu probes offered the unique possibility to detect lectins in different cells, even when the level of lectin expression was rather low. The confocal mode of spectrum recording provided an analysis of the probe localization with 3D submicron resolution. The spectral analysis (as a constituent part of the confocal spectral imaging technique) enabled interfering signals of the probe and intrinsic cellular fluorescence to be accurately separated, the distribution of the probe to be revealed and its local concentration to be measured.
Galanina, Oxana; Feofanov, Alexei; Tuzikov, Alexander B.; Rapoport, Evgenia; Crocker, Paul R.; Grichine, Alexei; Egret-Charlier, Marguerite; Vigny, Paul; Le Pendu, Jacques; Bovin, Nicolai V.
Amniotic fluid embolism, a rare, sudden and often fatal illness of pregnancy may not be a true embolic event resulting from the physical obstruction of the pulmonary vasculature. The high degree of variability in symptoms, the lack of characteristic findings on radiological exam, the absence of a dose-response effect on symptoms, and the occasional occurrence of coagulopathies are not entirely consistent with a physical block to the circulation as the main mechanism of disease. Alternatively, it might be the result of complement activation initiated by fetal antigen leaking into the maternal circulation. This rare immune response may be initiated by a rare pathological antigen, or by common antigens presented uncommonly--in amount, timing, or frequency of entry into the maternal circulation. Some very early evidence in AFE patients supports this hypothesis but is not conclusive. Complement levels remain well within the normal range during uncomplicated parturition. A prior theory that AFE might be a result of maternal anaphylaxis to fetal antigen has much less evidence to support it. The disseminated intravascular coagulation often seen in this and other serious obstetrical illnesses may be a secondary result of complement activation rather than the direct introduction of pro-coagulants into the maternal circulation although the link between the complement and coagulation pathways, if any, remains poorly defined. Through currently available laboratory testing, both the complement hypothesis and the anaphylaxis mechanism are able to be assessed. Direct measurement of serum complement as well as serum tryptase and urinary histamine are readily obtained tests in community hospitals as well as tertiary care hospitals. If the hypothesis proves true, this investigation may be of profound importance to understanding immune tolerance. Rather, than asking why one pregnant woman in 20,000 develops a violent immune reaction to the fetus, a better question is why do not all pregnant women reject the fetus which is a large collection of foreign antigens? PMID:17112682
Benson, Michael D
BACKGROUND: The complement system has been suggested to affect injury or disease of the central nervous system (CNS) by regulating numerous physiological events and pathways. The activation of complement following traumatic CNS injury can also result in the formation and deposition of C5b-9 membrane attack complex (C5b-9\\/MAC), causing cell lysis or sublytic effects on vital CNS cells. Although complement proteins
Hal X Nguyen; Manuel D Galvan; Aileen J Anderson
Erythema nodosum leprosum (ENL) is an inflammatory reaction that may occur in multibacillary leprosy patients, and thalidomide is the treatment of choice. Its cause and the mechanism by which thalidomide suppresses ENL are not known. In the skin lesions, im- mune complexes and split products of complement are found. The activation of complement could precipitate ENL, and thalidomide could suppress the inflammation by inhibiting the activation of complement. To determine if thalidomide could suppress the activation of complement, we first incubated normal serum with thalidomide and with M. leprae or zymosan. The amount of residual functional complement was then assessed by determining the dilution of serum required to lyses sheep erythrocytes sensitized by rabbit antibodies (CH50 Assay). M. leprae and zymosan activated complement. The residual complement activity in the serum incubated with M. leprae or with zymosan was equivalent to that incubated with M. leprae or zymosan in the presence of thalidomide, hydrolyzed thalidomide and metabolites of thalidomide. Thalidomide did not inhibit the activation of complement by zymosan, a known initiator of complement activation by the alternative pathway, or by M. leprae. PMID:21369644
Shannon, Edward J; Sandoval, Felipe G; Morales, Melvyn J
Factor H is a regulator of the alternative pathway of complement. Genetic studies have revealed that patients with factor H mutations are at increased risk for several types of renal disease. Pathogenic activation of the alternative pathway in acquired diseases, such as ischemic acute kidney injury, also suggests that non-mutated factor H also has a limited ability to control the alternative pathway in the kidney. In the current study we examined the ability of circulating factor H to control alternative pathway activation on renal tubular epithelial cells. We found that an absolute deficiency of factor H prevented complement activation on the cells after ischemia/reperfusion, likely because of consumption of alternative pathway proteins in the fluid phase. In contrast, when the fluid phase regulation by factor H was retained but the interaction of factor H with cell surfaces was blocked, complement activation after renal ischemia/reperfusion increased. Finally, a recombinant form of factor H that is specifically targeted to sites of C3 deposition was found to reduce complement activation in the tubulointerstitium after I/R. These studies demonstrate that native factor H provides critical regulation of the alternative pathway in the renal tubulointerstitium after injury, but that this protection is incomplete. An inhibitor that targeted recombinant factor H to the tissue surface prevented alternative pathway activation and attenuated renal injury after I/R.
Renner, Brandon; Ferreira, Viviana P.; Cortes, Claudio; Goldberg, Ryan; Ljubanovic, Danica; Pangburn, Michael K.; Pickering, Matthew C.; Tomlinson, Stephen; Holland-Neidermyer, Amanda; Strassheim, Derek; Holers, V. Michael; Thurman, Joshua M.
Cancer represents a set of more than 100 diseases, including malignant tumors from different locations. Strategies inducing differentiation have had limited success in the treatment of established cancers. Marine sponges are a biological reservoir of bioactive molecules, especially lectins. Several animal and plant lectins were purified with antitumor activity, mitogenic, anti-inflammatory and antiviral, but there are few reports in the literature describing the mechanism of action of lectins purified from marine sponges to induce apoptosis in human tumor cells. In this work, a lectin purified from the marine sponge Cinachyrella apion (CaL) was evaluated with respect to its hemolytic, cytotoxic and antiproliferative properties, besides the ability to induce cell death in tumor cells. The antiproliferative activity of CaL was tested against HeLa, PC3 and 3T3 cell lines, with highest growth inhibition for HeLa, reducing cell growth at a dose dependent manner (0.5–10 µg/mL). Hemolytic activity and toxicity against peripheral blood cells were tested using the concentration of IC50 (10 µg/mL) for both trials and twice the IC50 for analysis in flow cytometry, indicating that CaL is not toxic to these cells. To assess the mechanism of cell death caused by CaL in HeLa cells, we performed flow cytometry and western blotting. Results showed that lectin probably induces cell death by apoptosis activation by pro-apoptotic protein Bax, promoting mitochondrial membrane permeabilization, cell cycle arrest in S phase and acting as both dependent and/or independent of caspases pathway. These results indicate the potential of CaL in studies of medicine for treating cancer.
Rabelo, Luciana; Monteiro, Norberto; Serquiz, Raphael; Santos, Paula; Oliveira, Ruth; Oliveira, Adeliana; Rocha, Hugo; Morais, Ana Heloneida; Uchoa, Adriana; Santos, Elizeu
Phosphorothioate oligodeoxynucleotides can activate complement, and experimental murine studies have revealed differential effects upon simultaneous TLR stimulation and complement activation compared with either event alone. We set out to investigate the immune stimulatory effects of CpG 2006 in fresh non-anticoagulated human blood with or without presence of active complement. We also sought to elucidate the mechanism behind complement activation upon stimulation with phosphorothioate CpG 2006. In a human blood loop system, both backbone and sequence-specific effects by CpG were counteracted by selective inhibition of C3. Furthermore, DNA backbone-mediated CD40 and CD83 expression on monocytes and sequence-specific IL-6 and TNF production were reduced by complement inhibition. CpG-induced complement activation occurred via either the classical or the alternative pathway and deposits of both IgM and properdin, two activators of complement, were detected on CpG after incubation with EDTA plasma. Quartz crystal microbalance with dissipation monitoring demonstrated alternative pathway convertase build-up onto CpG as a likely pathway to initiate and sustain complement activation. Specific inhibition of C3 suppressed CpG 2006 uptake into monocytes indicating that C3 fragments are involved in CpG internalization. The interplay between complement and TLR9 signaling demonstrated herein warrants further investigation.
Mangsbo, Sara M.; Sanchez, Javier; Anger, Kerstin; Lambris, John D.; Ekdahl, Kristina Nilsson; Loskog, Angelica S.; Nilsson, Bo; Totterman, Thomas H.
Complement is an important component of the innate immune system that is crucial for defense from microbial infections and for clearance of immune complexes and injured cells. In normal conditions complement is tightly controlled by a number of fluid-phase and cell surface proteins to avoid injury to autologous tissues. When complement is hyperactivated, as occurs in autoimmune diseases or in subjects with dysfunctional regulatory proteins, it drives a severe inflammatory response in numerous organs. The kidney appears to be particularly vulnerable to complement-mediated inflammatory injury. Injury may derive from deposition of circulating active complement fragments in glomeruli, but complement locally produced and activated in the kidney also may have a role. Many kidney disorders have been linked to abnormal complement activation, including immune-complex-mediated glomerulonephritis and rare genetic kidney diseases, but also tubulointerstitial injury associated with progressive proteinuric diseases or ischemia-reperfusion. PMID:24161035
Noris, Marina; Remuzzi, Giuseppe
Genetically engineered tumor-selective vaccinia virus (VV) has been demonstrated to be a highly effective oncolytic agent, but immune clearance may limit its therapeutic potential. As previously demonstrated, immunosuppression can lead to significant enhancement of viral recovery and therapeutic effect, but the magnitude of complement-mediated viral inactivation has not been fully elucidated and warrants further investigation. Using fluorescent microscopy and quantitative plaque assays, we have determined complement's key role in viral clearance and its multi-faceted means to pathogen destruction. Complement can lead to direct viral destruction and inhibition of viral uptake into cells, even in the absence of anti-vaccinia antibodies. Our data demonstrate C5 to be integral to the clearance pathway, and its inhibition by Staphylococcal superantigen-like protein leads to a 90-fold and 150-fold enhancement of VV infectivity in both the presence and absence of anti-VV antibodies, respectively. This study suggests that complement inhibition may reduce vaccinia viral neutralization and may be critical to future in vivo work. PMID:23661042
Magge, D; Guo, Z S; O'Malley, M E; Francis, L; Ravindranathan, R; Bartlett, D L
Vaccinia virus complement control protein (VCP) possesses the ability to inhibit both classical and alternative pathways of complement activation, as well as bind to heparin or heparan sulfate proteoglycans, making it a unique multifunctional protein with therapeutic potential. Recently, the structure of the complete molecule of VCP was determined by X-ray crystallography. Two or three VCP molecules were packed within
Scott A Smith; Gunasekaran Krishnasamy; Krishna H. M Murthy; Alan Cooper; Krystyna Bromek; Paul N Barlow; Girish J Kotwal
Matrix ligands are intended for upstream use with dilute crudes on a large scale, splitting out sought-for proteins by coprecipitating them as dense, protected aggregates. Matrix ligand coprecipitation is rapidly, quantitatively reversible, by pH shifting and trapping matrix ligands on ion exchange resin, releasing the sought-for protein. Four lectins, wheat germ agglutinin, peanut lectin, concanavalin A, and Phaseolus vulgaris (red kidney bean) lectins, were coprecipitated from crude extracts, 0.05 to 0.4% crude protein, in a single step using Little Rock Orange matrix ligand. All were compared in specific activities (erythrocyte agglutination) and in SDS-PAGE analysis with the four corresponding commercial lectins purified by affinity chromatography. All four matrix-coprecipitated ligands were specifically active within range of the corresponding vendor (Sigma Co.) affinity chromatography-purified lectins. The matrix ligand coprecipitative technique requires optimization of ligand-protein (crude) ratios, denoted y, and determination of suitable pH ranges for coprecipitation relative to lectin isoelectric pH. These parameters control electrostatic ion pair association: ligand head anion binding to cationic target proteins. The coprecipitative and protective powers of new ligands like Little Rock Orange, their ability to scavenge sought-for lectins from dilute crudes, depend on ligand organic tail-tail association. After the strong anion heads of ligands bind to cationic proteins, their organic tails stack and draw the ligand-protein complexes together as aggregated coprecipitates. PMID:9512769
Wu, C W; Lovrien, R; Matulis, D
Assuming that lectins evolved to recognise relatively complex and branched oligosaccharides or parts of them, rather than simple sugars, a procedure based on lectin affinity binding to isolated erythrocyte (or any other cell type) membranes is proposed. This methodology was validated using six pure commercial lectins, as well as lectins from total protein extracts of Arbutus unedo leaves. All commercial lectins, as well as five polypeptides from A. unedo leaves bound to the glycosylated membrane receptors and were eluted by the corresponding sugars. When compared to the standard affinity chromatography procedure involving an individual sugar bound to a solid matrix, the new method provides a single-step, effective detection method for lectins and allows the rapid screening of their profile present in any unknown protein solution, indicates their biological carbohydrate affinities as well as their sugar specificities (if any), enables the simultaneous analysis of a large number of samples, does not require any pre-purification steps, permits detection of additional lectins and provides data which are more relevant from the physiological point of view. PMID:22381939
Ribeiro, Ana; Catarino, Sofia; Ferreira, Ricardo Boavida
The role of oxygen-derived free radicals (ODFR) in lectin-dependent cellular cytotoxicity (LDCC) in humans was investigated. The hydroxyl radical traps thiourea, methanol, ethanol and phenol were effective in inhibiting LDCC, as was DABCO, a singlet oxygen quencher. The proposed pathway of hydroxyl radical production in living cells is either an iron catalysed Haber-Weiss reaction or a Fenton reaction. The effect of inhibitors of these pathways was investigated. The superoxide anion scavengers superoxide dismutase, ferricytochrome c and Tiron were without effect. It was shown that Tiron inhibits the lucigenin-amplified chemiluminescence produced by the action of xanthine oxidase, and also the lucigenin-amplified chemiluminescence produced by activated PMN, suggesting that this agent (Tiron) scavenges intracellular superoxide anion. Catalase gave slight inhibition of LDCC only. The ferric iron chelator desferrioxamine gave no protection of the target cells, while the ferrous chelator, 1,10-phenanthroline, inhibited LDCC and partially prevented the detection of hydroxyl radicals generated by the Fe2+-H2O2 system. Cibacron blue, an agent that inhibits NAD(P)H linked enzymes, also inhibited LDCC. The cyclo-oxygenase inhibitors indomethacin and salicylate were without effect, while the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) inhibited cytolysis. None of the LDCC inhibitors was cytotoxic to the effector cells or to the target cells, neither did they inhibit lymphocyte-target binding. The findings would suggest that hydroxyl radicals have a role to play in human T-cell mediated cytolysis, either as the active lytic agent or as an epiphenomenon.
Melinn, M; McLaughlin, H
The role of oxygen-derived free radicals (ODFR) in lectin-dependent cellular cytotoxicity (LDCC) in humans was investigated. The hydroxyl radical traps thiourea, methanol, ethanol and phenol were effective in inhibiting LDCC, as was DABCO, a singlet oxygen quencher. The proposed pathway of hydroxyl radical production in living cells is either an iron catalysed Haber-Weiss reaction or a Fenton reaction. The effect of inhibitors of these pathways was investigated. The superoxide anion scavengers superoxide dismutase, ferricytochrome c and Tiron were without effect. It was shown that Tiron inhibits the lucigenin-amplified chemiluminescence produced by the action of xanthine oxidase, and also the lucigenin-amplified chemiluminescence produced by activated PMN, suggesting that this agent (Tiron) scavenges intracellular superoxide anion. Catalase gave slight inhibition of LDCC only. The ferric iron chelator desferrioxamine gave no protection of the target cells, while the ferrous chelator, 1,10-phenanthroline, inhibited LDCC and partially prevented the detection of hydroxyl radicals generated by the Fe2+-H2O2 system. Cibacron blue, an agent that inhibits NAD(P)H linked enzymes, also inhibited LDCC. The cyclo-oxygenase inhibitors indomethacin and salicylate were without effect, while the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) inhibited cytolysis. None of the LDCC inhibitors was cytotoxic to the effector cells or to the target cells, neither did they inhibit lymphocyte-target binding. The findings would suggest that hydroxyl radicals have a role to play in human T-cell mediated cytolysis, either as the active lytic agent or as an epiphenomenon. PMID:3011654
Melinn, M; McLaughlin, H
In normal human serum (NHS), axenic promastigotes of Crithidia, Phytomonas, and Leishmania trigger complement activation, and from 1.2 to 1.8 × 105 C3 molecules are deposited per promastigote within 2.5 min. In Leishmania, promastigote C3 binding capacity remains constant during in vitro metacyclogenesis. C3 deposition on promastigotes activated through the classical complement pathway reaches a 50% maximum after ?50 s, and represents >85% of total C3 bound. In C1q- and C2-deficient human sera, promastigotes cannot activate the classical pathway (CP) unless purified C1q or C2 factors, respectively, are supplemented, demonstrating a requirement for CP factor in promastigote C3 opsonization. NHS depleted of natural anti-Leishmania antibodies cannot trigger promastigote CP activation, but IgM addition restores C3 binding. Furthermore, Leishmania binds natural antibodies in ethylenediaminetetracetic acid (EDTA)-treated NHS; after EDTA removal, promastigote-bound IgM triggers C3 deposition in natural antibody-depleted NHS. Serum collectins and pentraxins thus do not participate significantly in NHS promastigote C3 opsonization. Real-time kinetic analysis of promastigote CP-mediated lysis indicates that between 85–95% of parasites are killed within 2.5 min of serum contact. These data indicate that successful Leishmania infection in man must immediately follow promastigote transmission, and that Leishmania evasion strategies are shaped by the selective pressure exerted by complement.
Dominguez, Mercedes; Moreno, Inmaculada; Lopez-Trascasa, Margarita; Torano, Alfredo
In normal human serum (NHS), axenic promastigotes of Crithidia, Phytomonas, and Leishmania trigger complement activation, and from 1.2 to 1.8 x 10(5) C3 molecules are deposited per promastigote within 2.5 min. In Leishmania, promastigote C3 binding capacity remains constant during in vitro metacyclogenesis. C3 deposition on promastigotes activated through the classical complement pathway reaches a 50% maximum after similar50 s, and represents >85% of total C3 bound. In C1q- and C2-deficient human sera, promastigotes cannot activate the classical pathway (CP) unless purified C1q or C2 factors, respectively, are supplemented, demonstrating a requirement for CP factor in promastigote C3 opsonization. NHS depleted of natural anti-Leishmania antibodies cannot trigger promastigote CP activation, but IgM addition restores C3 binding. Furthermore, Leishmania binds natural antibodies in ethylenediaminetetracetic acid (EDTA)-treated NHS; after EDTA removal, promastigote-bound IgM triggers C3 deposition in natural antibody-depleted NHS. Serum collectins and pentraxins thus do not participate significantly in NHS promastigote C3 opsonization. Real-time kinetic analysis of promastigote CP-mediated lysis indicates that between 85--95% of parasites are killed within 2.5 min of serum contact. These data indicate that successful Leishmania infection in man must immediately follow promastigote transmission, and that Leishmania evasion strategies are shaped by the selective pressure exerted by complement. PMID:11854358
Domínguez, Mercedes; Moreno, Inmaculada; López-Trascasa, Margarita; Toraño, Alfredo
Many plants contain carbohydrate-binding proteins that are commonly designated as lectins, agglutinins, or hemagglutinins. Due to the obvious differences in molecular structure, biochemical properties, and carbohydrate-binding specificity, plant lectins are usually considered a complex and heterogeneous group of proteins. Recent advances in the structural analysis of lectins and molecular cloning of lectin genes enable subdividision of plant lectins in a
Els J. M. Van Damme; Willy J. Peumans; Annick Barre; Pierre Rougé
Injection of tumour necrosis factor (TNF) in animals causes severe liver cell toxicity, especially when D-(+)-galactosamine (GalN) is co-administered. After challenge with TNF\\/GalN, serum complement activity (CH50 and APCH50) decreased dramatically, suggesting strong activation of both the classical and the alternative pathways. TNF or GalN alone had no such effect. A cleavage product of complement protein C3 [C3(b)] was deposited
Claude Libert; Ben Wielockx; Bernardo Grijalba; Wim Van Molle; Elisabeth Kremmer; Harvey R Colten; Walter Fiers; Peter Brouckaert
Complement activation during cardiopulmonary bypass is well known and may influence postoperative morbidity. As nylon can particularly induce complement activation, its influence was assessed by measuring total haemolytic complement and B, C3 and C4 factors, during cardiopulmonary bypass with bubble oxygenators for coronary surgery, comparing "nylon" circuits (20 patients, Bentley BOS 10) versus "polyester" circuits (19 patients, Shiley S 100 A). Complement activation began with induction of anaesthesia and surgical procedures, B, C3 and C4 levels falling significantly (respectively 15, 17 and 20% from baseline values). The alternative pathway was activated before the classical pathway. Complement activation continued during cardiopulmonary bypass, with no more consumption of complement factors (slight variations of about 0 to 3% of the levels found after anaesthetic induction and surgical procedures). No statistically significant difference appeared between the two groups. This suggested that nylon did not significantly increase complement activation during cardiopulmonary bypass. The bubble oxygenator material cannot therefore be considered as a criterion for choosing the type of equipment. PMID:3498413
Colson, P; Cosso, B; Delpech, S; Grolleau, D; Alien, M; Barlet, H; Cuchet, D; Saussine, M
Complement factor H (CFH) is one of the most important negative regulators of the alternative pathway of the complement system. It is a glycoprotein belonging to the protein H family, which is synthesized mainly in the liver and is composed into a globular protein consisting of 60 amino acid domains in the serum. It shows specificity for C3b molecule of the complement system present in the serum or bound to the cell surface. It inhibits the steady formation of C3 convertase enzymes and the binding of C2 to C4b and factor B to C3b. It accelerates the decomposition of C2a into C4b and the displacement of Bb from C3b. The present paper discusses the composition, properties and functions of the complement factor and the family it belongs to. The paper focuses in particular on its role in the pathogenesis of an infection caused by the spirochetes of the Borrelia genus. Through binding CFH and other related proteins, bacteria of the Borrelia species inhibit the key effect of the alternative pathway of the complement system - the lysis of spirochete cells dependent on the complement's activation. The mechanism enables pathogens to spread in the host organism and facilitates the evolution of the disease. Discovering the immune mechanisms of the infection caused by the spirochetes of the Borrelia genus may allow for implementing a therapy blocking the binding of complement factor H early enough, apart from the standard treatment of the disease. PMID:22922150
G?ca, Aleksandra; Mazurek, Urszula; Muc-Wierzgo?, Ma?gorzata; Nowakowska-Zajdel, Ewa; Niedworok, El?bieta; Zió?ko, Ewa; Kokot, Teresa
The last decade has produced pivotal change in our understanding of the molecular mechanisms underlying age-related macular degeneration (AMD), a leading cause of global blindness. In this time, the complement system has featured as a unifying theme for several elements of new evidence: initially, the discovery of complement proteins within drusen and subsequently, the association between AMD and mutations in various complement pathway genes, most notably complement factor H. Increasingly, a wealth of data are pointing towards a role for chronic local inflammation and complement activation in the patho-aetiology of AMD. These findings have paved the way for the exploration of a new paradigm of therapy in AMD management; targeting of specific molecular constituents in the complement pathway thus producing dampening or inhibition of the inflammatory response. Such an approach has the potential to intervene earlier in the disease process and ideally before vision is compromised. In this review we discuss the role of the complement system in AMD, novel therapies in preclinical evaluation and clinical trial, and whether these have a part to play in reducing the burden of disease. PMID:22304025
Troutbeck, Robyn; Al-Qureshi, Salmaan; Guymer, Robyn H
Spherical Torus (ST) as an example of confinement concept innovation to enable a potentially attractive pathway to fusion power is discussed. Given the anticipated high performance in small size, the ST plasma could be used to stimulate innovation also in engineering, technology, and material combinations to provide a smarter, cheaper, faster pathway. This pathway could complement the mainline program based
Complement activation is a crucial early event in Wallerian degeneration. In this study we show that treatment of rats with soluble complement receptor 1 (sCR1), an inhibitor of all complement pathways, blocked both systemic and local complement activation after crush injury of the sciatic nerve. Deposition of membrane attack complex (MAC) in the nerve was inhibited, the nerve was protected from axonal and myelin breakdown at 3 days after injury, and macrophage infiltration and activation was strongly reduced. We show that both classical and alternative complement pathways are activated after acute nerve trauma. Inhibition of the classical pathway by C1 inhibitor (Cetor) diminished, but did not completely block, MAC deposition in the injured nerve, blocked myelin breakdown, inhibited macrophage infiltration, and prevented macrophage activation at 3 days after injury. However, in contrast to sCR1 treatment, early signs of axonal degradation were visible in the nerve, linking MAC deposition to axonal damage. We conclude that sCR1 protects the nerve from early axon loss after injury and propose complement inhibition as a potential therapy for the treatment of diseases in which axon loss is the main cause of disabilities.
Ramaglia, Valeria; Wolterman, Ruud; de Kok, Maryla; Vigar, Miriam Ann; Wagenaar-Bos, Ineke; King, Rosalind Helen Mary; Morgan, Brian Paul; Baas, Frank
Complement C3 plays an essential role in the opsonization of pathogens in the mammalian complement system, whereas the molecular mechanism underlying C3 activation in invertebrates remains unknown. To understand the molecular mechanism of C3b deposition on microbes, we characterized two types of C2/factor B homologs (designated TtC2/Bf-1 and TtC2/Bf-2) identified from the horseshoe crab Tachypleus tridentatus. Although the domain architectures of TtC2/Bf-1 and TtC2/Bf-2 were identical to those of mammalian homologs, they contained five-repeated and seven-repeated complement control protein domains at their N-terminal regions, respectively. TtC2/Bf-1 and TtC2/Bf-2 were synthesized and glycosylated in hemocytes and secreted to hemolymph plasma, which existed in a complex with C3 (TtC3), and their activation by microbes was absolutely Mg2+-dependent. Flow cytometric analysis revealed that TtC3b deposition was Mg2+-dependent on Gram-positive bacteria or fungi, but not on Gram-negative bacteria. Moreover, this analysis demonstrated that Ca2+-dependent lectins (C-reactive protein-1 and tachylectin-5A) were required for TtC3b deposition on Gram-positive bacteria, and that a Ca2+-independent lectin (Tachypleus plasma lectin-1) was definitely indispensable for TtC3b deposition on fungi. In contrast, a horseshoe crab lipopolysaccharide-sensitive protease factor C was necessary and sufficient to deposit TtC3b on Gram-negative bacteria. We conclude that plasma lectins and factor C play key roles in microbe-specific TtC3b deposition in a C2/factor B-dependent or -independent manner.
Tagawa, Keisuke; Yoshihara, Toyoki; Shibata, Toshio; Kitazaki, Kazuki; Endo, Yuichi; Fujita, Teizo; Koshiba, Takumi; Kawabata, Shun-ichiro
In order to take advantage of the biorecognition between lectins and specific carbohydrates for targeted drug delivery, fluorescein-labelled lectins of different carbohydrate specificities were screened for binding to human colorectal carcinoma cell lines by flow cytometry and confocal microscopy. The lectin-binding rate increased as follows: Dolichos biflorus agglutinin, DBA Franz Gabor; Martina Stangl; Michael Wirth 1998-01-01
Franz Gabor; Martina Stangl; Michael Wirth
The legume species of Cymbosema roseum of Diocleinae subtribe produce at least two different seed lectins. The present study demonstrates that C. roseum lectin I (CRL I) binds with high affinity to the "core" trimannoside of N-linked oligosaccharides. Cymbosema roseum lectin II (CRL II), on the other hand, binds with high affinity to the blood group H trisaccharide (Fuc?1,2Gal?1-4GlcNAc-). Thermodynamic and hemagglutination inhibition studies reveal the fine binding specificities of the two lectins. Data obtained with a complete set of monodeoxy analogs of the core trimannoside indicate that CRL I recognizes the 3-, 4- and 6-hydroxyl groups of the ?(1,6) Man residue, the 3- and 4-hydroxyl group of the ?(1,3) Man residue and the 2- and 4-hydroxyl groups of the central Man residue of the trimannoside. CRL I possesses enhanced affinities for the Man5 oligomannose glycan and a biantennary complex glycan as well as glycoproteins containing high-mannose glycans. On the other hand, CRL II distinguishes the blood group H type II epitope from the Lewis(x), Lewis(y), Lewis(a) and Lewis(b) epitopes. CRL II also distinguishes between blood group H type II and type I trisaccharides. CRL I and CRL II, respectively, possess differences in fine specificities when compared with other reported mannose and fucose recognizing lectins. This is the first report of a mannose-specific lectin (CRL I) and a blood group H type II-specific lectin (CRL II) from seeds of a member of the Diocleinae subtribe. PMID:21406562
Dam, Tarun K; Cavada, Benildo S; Nagano, Celso S; Rocha, Bruno Am; Benevides, Raquel G; Nascimento, Kyria S; de Sousa, Luiz Ag; Oscarson, Stefan; Brewer, C Fred
Lectins from the horseshoe crab (Limulus polyphemus) and the garden snail (Helix pomatia) were tested for insulinomimetic activities in isolated rat epididymal adipocytes. The sialic acid binding horseshoe crab lectin suppressed epinephrine-induced lipolysis and augmented lipogenesis from D-[3-3H]-glucose while the N-acetylgalactosamine binding snail lectin was inactive. The results suggest that the insulin receptor on rat adipocytes contains sialic acid in its carbohydrate moiety but does not possess non-reducing alpha-D-galactopyranosyl or 2-acetamido-2-deoxy-alpha-D-galactopyranosyl end groups. PMID:3893876
Ng, T B; Wong, C M; Li, W W; Yeung, H W
A radioimmunoassay, capable of detecting the Dolichos biflorus lectin at concentrations as low as 400 ng/ml, was developed and used to follow the distribution of this lectin in the plant during its life cycle. The lectin was first detected in the seeds of the plant 27 days after flowering and rapidly attained the high level of lectin present in the mature seed. The lectin content of the plant is highest in the seeds and cotyledons and decreases as the storage materials of the cotyledons decrease. A low but measurable amount of material that reacts with antibodies to the seed lectin was detected in the leaves, stems, and pods of the plant. This material gives a precipitin band of only partial identity to the seed lectin when tested in immunodiffusion against antiserum to the seed lectin. No lectin was detected by the radioimmunoassay in the roots of the plant at any stage of development. ImagesFIG. 4
Talbot, Craig F.; Etzler, Marilynn E.
Haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TTP) are diseases characterized by microvascular thrombosis, with consequent thrombocytopaenia, haemolytic anaemia and dysfunction of affected organs. Advances in our understanding of the molecular pathology led to the recognition of three different diseases: typical HUS caused by Shiga toxin-producing Escherichia coli (STEC-HUS); atypical HUS (aHUS), associated with genetic or acquired disorders of regulatory components of the complement system; and TTP that results from a deficiency of ADAMTS13, a plasma metalloprotease that cleaves von Willebrand factor. In this Review, we discuss data indicating that complement hyperactivation is a common pathogenetic effector that leads to endothelial damage and microvascular thrombosis in all three diseases. In STEC-HUS, the toxin triggers endothelial complement deposition through the upregulation of P-selectin and possibly interferes with the activity of complement regulatory molecules. In aHUS, mutations in the genes coding for complement components predispose to hyperactivation of the alternative pathway of complement. In TTP, severe ADAMTS13 deficiency leads to generation of massive platelet thrombi, which might contribute to complement activation. More importantly, evidence is emerging that pharmacological targeting of complement with the anti-C5 monoclonal antibody eculizumab can effectively treat not only aHUS for which it is indicated, but also STEC-HUS and TTP in some circumstances. PMID:22986360
Noris, Marina; Mescia, Federica; Remuzzi, Giuseppe
Complement is an essential part of the innate immune response. It interacts with diverse endogenous pathways and contributes to the maintenance of homeostasis, the modulation of adaptive immune responses, and the development of various pathologies. The potential usefulness, in both research and clinical settings, of compounds that detect or modulate complement activity has resulted in thousands of publications on complement-related innovations in fields such as drug discovery, disease diagnosis and treatment, and immunoassays, among others. This study highlights the distribution and publication trends of patents related to the complement system that were granted by the United States Patent and Trademark Office from 1976 to the present day. A comparison to complement-related documents published by the World Intellectual Property Organization is also included. Statistical analyses revealed increasing diversity in complement-related research interests over time. More than half of the patents were found to focus on the discovery of inhibitors; interest in various inhibitor classes exhibited a remarkable transformation from chemical compounds early on to proteins and antibodies in more recent years. Among clinical applications, complement proteins and their modulators have been extensively patented for the diagnosis and treatment of eye diseases (especially age-related macular degeneration), graft rejection, cancer, sepsis, and a variety of other inflammatory and immune diseases. All of the patents discussed in this chapter, as well as those from other databases, are available from our newly constructed complement patent database: www.innateimmunity.us/patent . PMID:22990712
Yang, Kun; DeAngelis, Robert A; Reed, Janet E; Ricklin, Daniel; Lambris, John D
Complement is an essential part of the innate immune response. It interacts with diverse endogenous pathways and contributes to the maintenance of homeostasis, the modulation of adaptive immune responses, and the development of various pathologies. The potential usefulness, in both research and clinical settings, of compounds that detect or modulate complement activity has resulted in thousands of publications on complement-related innovations in fields such as drug discovery, disease diagnosis and treatment, and immunoassays, among others. This study highlights the distribution and publication trends of patents related to the complement system that were granted by the United States Patent and Trademark Office from 1976 to the present day. A comparison to complement-related documents published by the World Intellectual Property Organization is also included. Statistical analyses revealed increasing diversity in complement-related research interests over time. More than half of the patents were found to focus on the discovery of inhibitors; interest in various inhibitor classes exhibited a remarkable transformation from chemical compounds early on to proteins and antibodies in more recent years. Among clinical applications, complement proteins and their modulators have been extensively patented for the diagnosis and treatment of eye diseases (especially age-related macular degeneration), graft rejection, cancer, sepsis, and a variety of other inflammatory and immune diseases. All of the patents discussed in this chapter, as well as those from other databases, are available from our newly constructed complement patent database: www.innateimmunity.us/patent. PMID:23402036
Yang, Kun; DeAngelis, Robert A; Reed, Janet E; Ricklin, Daniel; Lambris, John D
Complement component C5 is crucial for experimental animal inflammatory tissue damage; however, its involvement in human inflammation is incompletely understood. The responses to gram-negative bacteria were here studied taking advantage of human genetic complement-deficiencies--nature's own knockouts--including a previously undescribed C5 defect. Such deficiencies provide a unique tool for investigating the biological role of proteins. The experimental conditions allowed cross-talk between the different inflammatory pathways using a whole blood model based on the anticoagulant lepirudin, which does not interfere with the complement system. Expression of tissue factor, cell adhesion molecules, and oxidative burst depended highly on C5, mediated through the activation product C5a, whereas granulocyte enzyme release relied mainly on C3 and was C5a-independent. Release of cytokines and chemokines was mediated to varying degrees by complement and CD14; for example, interleukin (IL)-1beta and IL-8 were more dependent on complement than IFN-gamma and IL-6, which were highly dependent on CD14. IL-1 receptor antagonist (IL-1ra) and IFN-gamma inducible protein 10 (IP-10) were fully dependent on CD14 and inversely regulated by complement, that is, complement deficiency and complement inhibition enhanced their release. Granulocyte responses were mainly complement-dependent, whereas monocyte responses were more dependent on CD14. Notably, all responses were abolished by combined neutralization of complement and CD14. The present study provides important insight into the comprehensive role of complement in human inflammatory responses to gram-negative bacteria. PMID:19717455
Lappegård, Knut Tore; Christiansen, Dorte; Pharo, Anne; Thorgersen, Ebbe Billmann; Hellerud, Bernt Christian; Lindstad, Julie; Nielsen, Erik Waage; Bergseth, Grethe; Fadnes, Dag; Abrahamsen, Tore G; Høiby, E Arne; Schejbel, Lone; Garred, Peter; Lambris, John D; Harboe, Morten; Mollnes, Tom Eirik
Cancer is one of the leading causes of death worldwide, generally exceeded only by cardiovascular disease in the developed world. The number of people diagnosed with cancer within the next few decades is expected to double. There will therefore be increased demand for novel diagnostic and medical therapies that use new non-traditional sources. Soybeans contain a variety of anticarcinogenic phytochemicals. Recently, there has been increased interest in the potential health benefits of bioactive polypeptides and proteins from soybeans, including lunasin and lectins. Lunasin is a polypeptide that arrests cell division and induces apoptosis in malignant cells. Lectins are glycoproteins that selectively bind carbohydrates; lectins are used in medicine in a variety of new applications. Additional research, including clinical trials, should continue to examine and elucidate the therapeutic effects, nutritional benefits, and toxic consequences of commonly ingested soybean lectins and lunasin. PMID:12918876
de Mejia, Elvira Gonzalez; Bradford, Traliece; Hasler, Clare
Lectins form a class of proteins that have evolved a specialized carbohydrate-binding function. Based on amino acid sequence analysis, several lectin families have been described and a lectin domain, the (QxW)3 domain, was discussed recently based on 11 family members. In this paper, the (QxW)3 domain family is extended to 45 sequences, several of which have very low sequence identity with the previously known members of the family. A hidden Markov model was used to identify the most divergent members of the family. The expanded set of sequences gives us a more complete appreciation of the conserved features, and the lack thereof, in this lectin family. This, in turn, provides new insights in the structural and functional properties of the individual family members.
Using lectins, proteins which combine specifically with carbohydrate molecules or groups, this activity will introduce the students to the many important roles that the cell membrane serves in biological processes.
Ingrith Deyrup-Olsen (University of Washington;)
New template-based self-propelled gold/nickel/polyaniline/platinum (Au/Ni/PANI/Pt) microtubular engines, functionalized with the Concanavalin A (ConA) lectin bioreceptor, are shown to be extremely useful for the rapid, real-time isolation of Escherichia coli (E. coli) bacteria from fuel-enhanced environmental, food and clinical samples. These multifunctional microtube engines combine the selective capture of E. coli with the uptake of polymeric drug-carrier particles to provide an attractive motion-based theranostics strategy. Triggered release of the captured bacteria is demonstrated by movement through a low-pH glycine-based dissociation solution. The smaller size of the new polymer-metal microengines offers convenient, direct and label-free optical visualization of the captured bacteria and discrimination against non-target cells.
Campuzano, Susana; Orozco, Jahir; Kagan, Daniel; Guix, Maria; Gao, Wei; Sattayasamitsathit, Sirilak; Claussen, Jonathan C.; Merkoci, Arben; Wang, Joseph
Extract of the seeds ofAnona reticulata, Camellia sinensis, Bauhinia acuminata, Cassia tomentosa, Malus sylvestris, Trigonella foenumgraecum, Cephalandra\\u000a indica, Lawsonia inermis, Anacardium occidentale, Mangifera indica, Nephelium litchi, Citrus lemoni, Aegle marmelos, Quassia\\u000a amara, Mimusops elengi, Achras sapota, Datura stramonium, Thevetia nerifolia, Persea americana andCycas circinalis, were screened for lectin activity by haemagglutination and haemagglutination inhibition assays. Lectin-like activity was\\u000a detected only
V. M. Haseena BeeVI; P. Remani; R. Ankathil; K. K. Vijayan; T. Vijayakumar
Biotinyl derivatives of several lectins and avidin-horseradish peroxidase were used to study the localization of glycoconjugates in amyloid plaques and in neuritic tangles in brains of patients with Alzheimer's disease (AD), Downs syndrome (DS) and Gerstmann-Sträussler syndrome (GSS). The lectins tested recognize the following residues: ß-d-galactosyl [Ricinus communis agglutinin 120, (RCA-1) and peanut agglutinin, (PNA)]; a-d-galactosyl [Griffonia simplicifolia agglutinin (GSA)];
G. Szumanska; A. W. Vorbrodt; T. I. Mandybur; H. M. Wisniewski
Snake venoms contain saccharide-binding lectins. In this work, we examined the biological activities of a lectin (BjcuL) purified from Bothrops jararacussu snake venom by chromatography on non-derivatized Sepharose 4B and Sephacryl S-200 HR. The protein, a homodimer with subunits of 14.5kDa, gave a single immunoprecipitin line in immunoelectrophoresis and cross-reacted in ELISA with antivenoms raised against Bothrops spp. (lanceheads), Micrurus
Patrícia C. Panunto; Maura A. da Silva; Alessandra Linardi; Marta P. Buzin; Silvia E. S. F. C. Melo; Sueli M. Mello; Julia Prado-Franceschi; Stephen Hyslop
Asialofetuin-linked amino activated silica was used for the affinity purification of lectins from Amaranthus hypochondriacus Linn (AHL) and A. tricolor Linn (ATL). Like a few other Amaranthus lectins, these lectins were also inhibited by N-acetyl-D-galactosamine, fetuin and asialofetuin; they agglutinated human and different animal erythrocytes. The purified lectins yielded a single band on PAGE pH 8.3, pH 4.5 and SDS-PAGE, pH 8.3. These also gave a single peak in gel exclusion on Biogel P-200, HPLC 300 SW and cation exchange columns. However, both lectins gave multiple peaks in anion exchange column and multiple bands in isoelectric focusing. AHL and ATL are dimeric proteins in which the subunits having M(r) 29,000 and 39,000, respectively, are not held together by disulphide linkages. The pure lectins are glycoproteins and do not require Ca2+, Mn2+ and Mg2+ for their agglutination activity. PMID:7698887
Singh, J; Kamboj, K K; Kamboj, S S; Shangary, S; Sandhu, R S
Lectins are carbohydrate-binding proteins of non-imune origin. This group of proteins is distributed widely in nature and they have been found in viruses, microorganisms, plants and animals. Lectins of plants have been isolated and characterized according to their chemical, physical-chemical, structural and biological properties. Among their biological activities, we can stress its fungicidal action. It has been previously described the effect of the lectins Dviol, DRL, ConBr and LSL obtained from the seeds of leguminous plants on the growth of yeasts isolated from vaginal secretions. In the present work the experiments were carried out in microtiter plates and the results interpreted by both methods: visual observations and a microplate reader at 530nm. The lectin concentrations varied from 0.5 to 256?g/mL, and the inoculum was established between 65-70% of trammitance. All yeast samples isolated from vaginal secretion were evaluated taxonomically, where were observed macroscopic and microscopic characteristics to each species. The LSL lectin did not demonstrate any antifungal activity to any isolate studied. The other lectins DRL, ConBr and DvioL, showed antifungal potential against yeast isolated from vaginal secretion. These findings offering offer a promising field of investigation to develop new therapeutic strategies against vaginal yeast infections, collaborating to improve women's health.
Gomes, Bruno Severo; Siqueira, Ana Beatriz Sotero; de Cassia Carvalho Maia, Rita; Giampaoli, Viviana; Teixeira, Edson Holanda; Arruda, Francisco Vassiliepe Sousa; do Nascimento, Kyria Santiago; de Lima, Adriana Nunes; Souza-Motta, Cristina Maria; Cavada, Benildo Sousa; Porto, Ana Lucia Figueiredo
Phagocytosis of Borrelia burgdorferi, the causative agent of Lyme disease, is mediated partly by the interaction of the spirochete with Complement Receptor (CR) 3. CR3 requires the GPI-anchored protein, CD14, in order to efficiently internalize CR3-B. burgdorferi complexes. GPI-anchored proteins reside in cholesterol-rich membrane microdomains, and through its interaction with partner proteins, help initiate signaling cascades. Here, we investigated the role of CD14 on the internalization of B. burgdorferi mediated by CR3. We show that CR3 partly colocalizes with CD14 in lipid rafts. The use of the cholesterol-sequestering compound methyl-?-cyclodextran completely prevents the internalization of the spirochete in CHO cells that co-express CD14 and CR3, while no effect was observed in CD11b-deficient macrophages. These results show that lipid rafts are required for CR3-dependent, but not independent, phagocytosis of B. burgdorferi. Our results also suggest that CD14 interacts with the C-lectin domain of CR3, favoring the formation of multi-complexes that allow their internalization, and the use of ?-glucan, a known ligand for the C-lectin domain of CR3, can compensate for the lack of CD14 in CHO cells that express CR3. These results provide evidence to understand the mechanisms that govern the interaction between CR3 and CD14 during the phagocytosis of B. burgdorferi.
Hawley, Kelly L.; Martin-Ruiz, Itziar; Iglesias-Pedraz, Juan M.; Berwin, Brent; Anguita, Juan
Studies on the possible involvement of complement component C3 in the initiation of acid hydrolase secretion by macrophages. I. Correlation between enzyme-releasing and complement-activating capacities of several secretagogues.
A possible relationship between activation of the alternative pathway of complement and acid hydrolase secretion by macrophages has been investigated in vitro by examining the dose--response characteristics of several immunological and non-immunological stimuli of these two processes. Zymosan particles, insoluble immune complexes, methylamine and several other primary aliphatic monoamines were all found to elicit the selective release of lysosomal enzymes from macrophages by a process that correlated well with the ability of these agents to bring about consumption of haemolytically-active components of the alternative complement pathway. By contrast, substances which failed to activate the alternative complement pathway, i.e. soluble aggregated immunoglobulin and several primary aliphatic diamines, were found to be likewise incapable of inducing the selective release of lysosomal glycosidases from macrophages. These observations are interpreted as further evidence for imputing a role for complement C3 in the initiation of lysosomal enzyme release from macrophages. Images Figure 8 Figure 9
Riches, D W; Stanworth, D R
Background Although activation of the complement system in myocardial infarction and cardiopulmonary bypass has been shown to contribute to myocardial injury, its role in congestive heart failure (CHF) is unknown. The purpose of this study was to determine the presence of terminal complement activation and its relation to clinical outcomes in patients with CHF. Methods We measured serum levels of
David J. Clark; Michael W. Cleman; Steven E. Pfau; Scott A. Rollins; Tarik M. Ramahi; Craig Mayer; Teresa Caulin-Glaser; Edouard Daher; Mikhail Kosiborod; Leonard Bell; John F. Setaro
Complement may be important for immunity to infection with parasitic helminths, by promoting the recruitment of leukocytes to infected tissues and by modulating the function of cytotoxic effector leukocytes. However, the importance of complement in vivo during helminth infection is poorly understood. In this study, mice lacking classical (C1q-deficient), alternative (factor B-deficient) or all pathways of complement activation (C3-deficient) were used to assess the role of complement in immunity to the nematode Nippostrongylus brasiliensis. Double-mutant complement-deficient/IL-5 transgenic (Tg) mice were used to determine if complement is required for the strong eosinophil-dependent resistance to this parasite. Complement activation on larvae (C3 deposition), extracellular eosinophil peroxidase activity, larval aggregation and eosinophil recruitment to the skin 30 min post-injection (p.i.) of larvae were reduced in factor B-deficient mice. Inhibition of the C5a receptor with the antagonist PMX53 impaired eosinophil and neutrophil recruitment to the skin. C3 deposition on larvae was minimal by 150 min p.i. and at this time cell adherence, larval aggregation, eosinophil recruitment and degranulation were complement-independent. Factor B and C3 deficiency were associated with higher lung larval burdens in primary infections. Complement-deficient/IL-5 Tg mice were highly resistant to N. brasiliensis, suggesting that eosinophils can limit infection in a complement-independent manner. Potent secondary immunity was similarly complement-independent. In conclusion, although the alternative pathway is important for parasite recognition and leukocyte recruitment early in N. brasiliensis infections, the parasite soon becomes resistant to complement and other factors can compensate to promote eosinophil-dependent immunity. PMID:17675237
Giacomin, Paul R; Gordon, David L; Botto, Marina; Daha, Mohamed R; Sanderson, Sam D; Taylor, Stephen M; Dent, Lindsay A
Ebola viruses constitute a newly emerging public threat because they cause rapidly fatal hemorrhagic fevers for which no treatment exists, and they can be manipulated as bioweapons. We targeted conserved N-glycosylated carbohydrate ligands on viral envelope surfaces using novel immune therapies. Mannose-binding lectin (MBL) and L-ficolin (L-FCN) were selected because they function as opsonins and activate complement. Given that MBL has a complex quaternary structure unsuitable for large scale cost-effective production, we sought to develop a less complex chimeric fusion protein with similar ligand recognition and enhanced effector functions. We tested recombinant human MBL and three L-FCN/MBL variants that contained the MBL carbohydrate recognition domain and varying lengths of the L-FCN collagenous domain. Non-reduced chimeric proteins formed predominantly nona- and dodecameric oligomers, whereas recombinant human MBL formed octadecameric and larger oligomers. Surface plasmon resonance revealed that L-FCN/MBL76 had the highest binding affinities for N-acetylglucosamine-bovine serum albumin and mannan. The same chimeric protein displayed superior complement C4 cleavage and binding to calreticulin (cC1qR), a putative receptor for MBL. L-FCN/MBL76 reduced infection by wild type Ebola virus Zaire significantly greater than the other molecules. Tapping mode atomic force microscopy revealed that L-FCN/MBL76 was significantly less tall than the other molecules despite similar polypeptide lengths. We propose that alterations in the quaternary structure of L-FCN/MBL76 resulted in greater flexibility in the collagenous or neck region. Similarly, a more pliable molecule might enhance cooperativity between the carbohydrate recognition domains and their cognate ligands, complement activation, and calreticulin binding dynamics. L-FCN/MBL chimeric proteins should be considered as potential novel therapeutics.
Michelow, Ian C.; Dong, Mingdong; Mungall, Bruce A.; Yantosca, L. Michael; Lear, Calli; Ji, Xin; Karpel, Marshall; Rootes, Christina L.; Brudner, Matthew; Houen, Gunnar; Eisen, Damon P.; Kinane, T. Bernard; Takahashi, Kazue; Stahl, Gregory L.; Olinger, Gene G.; Spear, Gregory T.; Ezekowitz, R. Alan B.; Schmidt, Emmett V.
Background Long-term lung allograft survival is limited by bronchiolitis obliterans syndrome (BOS). Mannose binding lectin (MBL) belongs to the innate immune system, participates in complement activation, and may predispose to graft rejection. We investigated mannose binding (MBL) during cold ischemia and in tissue samples from explanted lungs with BOS, and assessed MBL and complement proteins in plasma post-lung transplantation relative to BOS staging. Methods MBL was detected by immunohistochemistry lung tissue at the time of cold ischemia and in samples with BOS. MBL was assayed in the peripheral blood of 66 lung transplant patients transplanted between 1990–2007. Results MBL localized to vasculature and basement membrane during cold ischemia and BOS. Patients further out post-lung transplant?>?5?years (n?=?33), had significantly lower levels of MBL in the blood compared to lung transplant patients?5?years with BOS Op-3 (n?=?17), 1738?±?250?ng/ml vs 3198?±?370?ng/ml, p?=?0.027, and similar levels to lung transplant patients?5?years with BOS 0 (n?=?16), 1738?±?250?ng/ml vs 1808?±?345?ng/ml. MBL levels in all BOS 0 (n?=?30) vs. all BOS Op-3 (n?=?36) were 1378?±?275?ng/ml vs. 2578?±?390?ng/ml, p?=?0.001, respectively. C3 plasma levels in BOS 0 (n?=?30) vs. BOS Op-3 (n?=?36) were 101?±?19.8?mg/ml vs. 114?±?25.2?mg/ml, p?=?0.024, respectively. Conclusions MBL localizes within the lung during graft ischemia and BOS, higher levels of plasma MBL are associated with BOS Op-3 and?5?years post-transplant, and higher level of plasma complement protein C3 was associated with BOS Op-3 clinical status. MBL may serve as a biomarker for poorer outcome post-lung transplantation.
Introduction Previous studies have provided inconsistent results on whether variants in the MBL2 gene, coding for the complement-activating mannan-binding lectin (MBL) protein, associate with rheumatoid arthritis (RA).\\u000a We re-evaluated this in context of the main environmental and genetic risk factors (smoking, HLA-DRB1 'shared epitope' (SE),\\u000a PTPN22*620W), which predispose to rheumatoid factor (RF) and\\/or anti-citrullinated-protein antibody (ACPA)-positive RA.\\u000a \\u000a \\u000a \\u000a \\u000a Methods In this population-based EIRA
Saedis Saevarsdottir; Bo Ding; Kristjan Steinsson; Gerdur Grondal; Helgi Valdimarsson; Lars Alfredsson; Lars Klareskog; Leonid Padyukov
The sponge Axinella polypoides contains several D-galactose binding lectins. One of the main components, lectin I was sequenced earlier, the complete sequence of the other major constituent of saline extracts, lectin II has been determined by amino acid sequencing and mass spectrometry. Both lectins have a homology of 65% to each other and both possess a disulfide loop between positions 4 and 46. As long as this loop is closed in both lectins, they can be boiled in the presence of SDS or treated with 6 mol guanidine hydrochloride without losing their hemagglutinating activity. Incubation with beta-mercaptoethanol alone does not effect the carbohydrate binding capacity either. However, reduction of the disulfide bond under chaotropic conditions destroys the activity irreversibly. This disulfide loop is also an immunologically dominant epitope in both lectins, as was revealed with monospecific polyclonal antisera. Thus, sponge lectins seem to be of different origins, since three completely different structures were described: the structure of Geodia cydonium, related to the mammalian S-type lectins with one SH-group, the Axinella lectins with one disulfide loop and the Aaptos lectins I and II with 11 cysteine residues/subunit. PMID:9972291
Buck, F; Schulze, C; Breloer, M; Strupat, K; Bretting, H
An alternative adaptive-immune system is present in the most basal vertebrates--lampreys and hagfish--the only surviving jawless vertebrates. These eel-like fish use leucine-rich repeat-based receptors for Ag recognition instead of the Ig-based receptors used in jawed vertebrates. We report that in Japanese lamprey (Lampetra japonica), variable lymphocyte receptor (VLR)B interacts with C1q and C3 proteins to mediate complement-dependent cytotoxicity for bacteria and tumor cells. The immune-based lysis involves deposition of VLRB and C1q-like protein complex on the surface of target cells, activation of C3, and ultimate disruption of cell wall integrity. The demonstration of functional interaction between VLRB and complement components in lamprey provides evidence for the emergence of cooperative innate and adaptive-immune responses at a pivotal point in vertebrate evolution, before or in parallel with the evolution of Ig-based Abs and the classical complement-activation pathway. PMID:23293356
Wu, Fenfang; Chen, Liyong; Liu, Xin; Wang, Huaying; Su, Peng; Han, Yinglun; Feng, Bo; Qiao, Xu; Zhao, Jing; Ma, Ning; Liu, Huijie; Zheng, Zhen; Li, Qingwei
Many cyanobacteria alter their phycobilisome composition in response to changes in light wavelength in a process termed complementary chromatic adaptation. Mutant strains FdR1 and FdR2 of the filamentous cyanobacterium Fremyella diplosiphon are characterized by aberrant chromatic adaptation. Instead of adjusting to different wavelengths of light, FdR1 and FdR2 behave as if they are always in green light; they do not respond to red light. We have previously reported complementation of FdR1 by conjugal transfer of a wild-type genomic library. The complementing DNA has now been localized by genetic analysis to a region on the rescued genomic subclone that contains a gene designated rcaC. This region of DNA is also able to complement FdR2. Southern blot analysis of genomic DNA from FdR1 and FdR2 indicates that these strains harbor DNA insertions within the rcaC sequence that may have resulted from the activity of transposable genetic elements. The predicted amino acid sequence of RcaC shares strong identity to response regulators of bacterial two-component regulatory systems. This relationship is discussed in the context of the signal-transduction pathway mediating regulation of genes encoding phycobilisome polypeptides during chromatic adaptation. Images
Chiang, G G; Schaefer, M R; Grossman, A R
Aspergillus fumigatus has previously been shown to produce a soluble extracellular inhibitor of the alternative complement pathway, called Aspergillus complement inhibitor, or CI. We now report an efficient method for production of CI which relies on the fact that poorly conidiating cultures yielded CI activity with approximately sevenfold-higher potency than CI produced by conidiating cultures. CI from poorly conidiating cultures provided 50% inhibition of alternative pathway-mediated binding of 125I-labeled complement component C3 to cryptococcal blastoconidia at a mean concentration of 60 micrograms/ml. The ability of crude CI to inhibit the alternative complement pathway seemed to be independent of intact protein or polysaccharide structure, as evidenced by resistance of inhibitory activity to digestion by proteases, including subtilisin, alpha-chymotrypsin, papain, and pepsin as well as endoglycosidases F and H. Separation of the active inhibitory component of CI from contaminating materials contained in crude CI preparations was achieved by using Phenylsuperose hydrophobic interaction chromatography in a fast protein liquid chromatography system. The active material proved to be extremely hydrophobic, desorbing from the column only during elution with ethanol; it contained only 15% protein and 5% polysaccharide. Furthermore, results from preparative thin-layer chromatography indicated that lipids which comigrated with phosphatidylserine/phosphatidylinositol and phosphatidylethanolamine possessed significant complement-inhibitory activity. Taken together, these data suggested that phospholipids from A. fumigatus contributed to the functional activity of CI. Images
Washburn, R G; DeHart, D J; Agwu, D E; Bryant-Varela, B J; Julian, N C
The lytic effect of complement on human erythrocytes has been reported by others to increase when Na+ is substituted for K+ in the external medium. In this paper we have investigated the hypothesis that net loss of K+ through a K+ transport pathway protects erythrocytes from complement-induced colloidosmotic swelling and lysis. Antibody-sensitized human erythrocytes containing different intracellular cation concentrations (nystatin treatment) were exposed to low concentrations of guinea pig serum in media of different cation composition; complement lysis was assessed by the release of hemoglobin and the volume of the surviving cells estimated by their density distribution profiles. Complement-dependent swelling and lysis of erythrocytes (a) were limited by the presence of an outwardly directed K+ electrochemical gradient and (b) were enhanced by carbocyanine, a specific inhibitor of the Ca2+-activated K+ transport pathway, and by absence of Ca2+ in the external medium. We propose that during complement activation a rising cytosolic calcium triggers the Ca2+-activated K+ permeability pathway, the Gardos effect, produces a net K+, Cl- and water loss, and thus limits the colloidosmotic swelling and lysis of erythrocytes.
Halperin, J A; Brugnara, C; Nicholson-Weller, A
Hemolytic-uremic syndrome (HUS) is a rare life-threatening disorder characterized by microangiopathic hemolytic anemia, thrombocytopenia, and impaired renal function. A thrombotic microangiopathy underlies the clinical features of HUS. In the majority of cases, HUS follows an infection with toxin-producing bacteria such as verotoxin-producing Escherichia coli. In some cases, HUS is not preceded by a clinically apparent infection, and therefore, is named atypical HUS. The prognosis of atypical HUS is poor. While mortality approaches 25% during the acute phase, end-stage renal disease develops in nearly half of patients within a year. Evidence is accumulating that complement activation through the alternative pathway is at the heart of the pathophysiology leading to atypical HUS. Genetic abnormalities involving complement regulatory proteins and complement components form the molecular basis for complement activation. Since microvascular thrombosis is a quintessential feature of atypical HUS, complements and the coagulation system must work in tandem to give rise to the pathologic alterations observed in this condition. Here, a brief discussion of clinical and morphologic features of atypical HUS is followed by a concise presentation of the complement and coagulation systems. The interplay between complements and the coagulation system is graphically highlighted. Last but not least, conventional and emerging therapies for atypical HUS are outlined. PMID:24072143
Nayer, Ali; Asif, Arif
The serum bactericidal assay is the correlate of protection for meningococcal disease but the use and comparison of functional immunological assays for the assessment of meningococcal vaccines is complicated by the sourcing of human complement. This is due to high levels of immunity in the population acquired through natural meningococcal carriage and means that many individuals must be screened to find donors with suitably low bactericidal titres against the target strain. The use of different donors for each meningococcal strain means that comparisons of assay responses between strains and between laboratories is difficult. We have developed a method for IgG-depletion of 300 ml batches of pooled human lepirudin-derived plasma using Protein G sepharose affinity chromatography that retains complement activity. However, IgG-depletion also removed C1q. This was also eluted from the affinity matrix, concentrated and added to the complement source. The final complement source retained mean alternative pathway activity of 96.8% and total haemolytic activity of 84.2% in four batches. Complement components C3, C5, properdin and factor H were retained following the process and the IgG-depleted complement was shown to be suitable for use in antibody-mediated complement deposition and serum bactericidal activity assays against serogroup B meningococci. The generation of large IgG-depleted batches of pooled human plasma allows for the comparison of immunological responses to diverse meningococcal strain panels in large clinical trials. PMID:23485926
Brookes, Charlotte; Kuisma, Eeva; Alexander, Frances; Allen, Lauren; Tipton, Thomas; Ram, Sanjay; Gorringe, Andrew; Taylor, Stephen
C-reactive protein (CRP) and complement are hypothesized to be major mediators of inflammation in atherosclerotic plaques. We used the reverse transcriptase-polymerase chain reaction technique to detect the mRNAs for CRP and the classical complement components C1 to C9 in both normal arterial and plaque tissue, establishing that they can be endogenously generated by arteries. When the CRP mRNA levels of plaque tissue, normal artery, and liver were compared in the same cases, plaque levels were 10.2-fold higher than normal artery and 7.2-fold higher than liver. By Western blotting, we showed that the protein levels of CRP and complement proteins were also up-regulated in plaque tissue and that there was full activation of the classical complement pathway. By in situ hybridization, we detected intense signals for CRP and C4 mRNAs in smooth muscle-like cells and macrophages in the thickened intima of plaques. By immunohistochemistry we showed co-localization of CRP and the membrane attack complex of complement. We also detected up-regulation in plaque tissue of the mRNAs for the macrophage markers CD11b and HLA-DR, as well as their protein products. We showed by immunohistochemistry macrophage infiltration of plaque tissue. Because CRP is a complement activator, and activated complement attacks cells in plaque tissue, these data provide evidence of a self-sustaining autotoxic mechanism operating within the plaques as a precursor to thrombotic events.
Yasojima, Koji; Schwab, Claudia; McGeer, Edith G.; McGeer, Patrick L.
Dendritic cells are equipped with lectin receptors to sense the extracellular environment and modulate cellular responses. Human plasmacytoid dendritic cells (pDCs) uniquely express blood dendritic cell antigen 2 (BDCA2) protein, a C-type lectin lacking an identifiable signaling motif. We demonstrate here that BDCA2 forms a complex with the transmembrane adapter Fc?RI?. Through pathway analysis, we identified a comprehensive signaling machinery
Wei Cao; Li Zhang; David B Rosen; Laura Bover; Gokuran Watanabe; Musheng Bao; Lewis L Lanier; Yong-Jun Liu
The Xenopus laevis embryonic epidermal lectin (XEEL) is a novel member of a group of lectins including mammalian intelectins, frog oocyte cortical granule lectins, and plasma lectins in lower vertebrates and ascidians. We isolated the XEEL protein from the extract of tailbud embryos by affin- ity chromatography on a galactose-Sepharose column. The XEEL protein is a homohexamer of 43-kDa N-glycosylated
The protein predicted to be defective in individuals with Fanconi anemia complementation group J (FA-J), FANCJ, is a missing component in the Fanconi anemia pathway of genome maintenance. Here we identify pathogenic mutations in eight individuals with FA-J in the gene encoding the DEAH-box DNA helicase BRIP1, also called FANCJ. This finding is compelling evidence that the Fanconi anemia pathway
Marieke Levitus; Quinten Waisfisz; Barbara C Godthelp; Yne de Vries; Shobbir Hussain; Wouter W Wiegant; Elhaam Elghalbzouri-Maghrani; Jûrgen Steltenpool; Martin A Rooimans; Gerard Pals; Fré Arwert; Christopher G Mathew; Ma?gorzata Z Zdzienicka; Kevin Hiom; Johan P De Winter; Hans Joenje
Tocopherols are nonpolar compounds synthesized and localized in plastids but whose genetic elimination specifically impacts fatty acid desaturation in the endoplasmic reticulum (ER), suggesting a direct interaction with ER-resident enzymes. To functionally probe for such interactions, we developed transorganellar complementation, where mutated pathway activities in one organelle are experimentally tested for substrate accessibility and complementation by active enzymes retargeted to a companion organelle. Mutations disrupting three plastid-resident activities in tocopherol and carotenoid synthesis were complemented from the ER in this fashion, demonstrating transorganellar access to at least seven nonpolar, plastid envelope-localized substrates from the lumen of the ER, likely through plastid:ER membrane interaction domains. The ability of enzymes in either organelle to access shared, nonpolar plastid metabolite pools redefines our understanding of the biochemical continuity of the ER and chloroplast with profound implications for the integration and regulation of organelle-spanning pathways that synthesize nonpolar metabolites in plants. PMID:23818635
Mehrshahi, Payam; Stefano, Giovanni; Andaloro, Joshua Michael; Brandizzi, Federica; Froehlich, John E; DellaPenna, Dean
Complement forms a key arm of innate immune defenses against gonococcal infection. Sialylation of gonococcal lipo-oligosaccharide, or expression of porin 1A (Por1A) protein, enables Neisseria gonorrhoeae to bind the alternative pathway complement inhibitor, factor H (fH), and evade killing by human complement. Using recombinant fH fragment-murine Fc fusion proteins, we localized two N. gonorrhoeae Por1A-binding regions in fH: one in complement control protein domain 6, the other in complement control proteins 18-20. The latter is similar to that reported previously for sialylated Por1B gonococci. Upon incubation with human serum, Por1A and sialylated Por1B strains bound full-length human fH (HufH) and fH-related protein 1. In addition, Por1A strains bound fH-like protein 1 weakly. Only HufH, but not fH from other primates, bound directly to gonococci. Consistent with direct HufH binding, unsialylated Por1A gonococci resisted killing only by human complement, but not complement from other primates, rodents or lagomorphs; adding HufH to these heterologous sera restored serum resistance. Lipo-oligosaccharide sialylation of N. gonorrhoeae resulted in classical pathway regulation as evidenced by decreased C4 binding in human, chimpanzee, and rhesus serum but was accompanied by serum resistance only in human and chimpanzee serum. Direct-binding specificity of HufH only to gonococci that prevents serum killing is restricted to humans and may in part explain species-specific restriction of natural gonococcal infection. Our findings may help to improve animal models for gonorrhea while also having implications in the choice of complement sources to evaluate neisserial vaccine candidates. PMID:18292569
Ngampasutadol, Jutamas; Ram, Sanjay; Gulati, Sunita; Agarwal, Sarika; Li, Chongqing; Visintin, Alberto; Monks, Brian; Madico, Guillermo; Rice, Peter A
Using a combination of protein isolation/characterization and molecular cloning, we have demonstrated that the bark of the black mulberry tree (Morus nigra) accumulates large quantities of a galactose-specific (MornigaG) and a mannose (Man)-specific (MornigaM) jacalin-related lectin. MornigaG resembles jacalin with respect to its molecular structure, specificity, and co- and posttranslational processing indicating that it follows the secretory pathway and eventually accumulates in the vacuolar compartment. In contrast, MornigaM represents a novel type of highly active Man-specific jacalin-related lectin that is synthesized without signal peptide or other vacuolar targeting sequences, and accordingly, accumulates in the cytoplasm. The isolation and cloning, and immunocytochemical localization of MornigaG and MornigaM not only demonstrates that jacalin-related lectins act as vegetative storage proteins in bark, but also allows a detailed comparison of a vacuolar galactose-specific and a cytoplasmic Man-specific jacalin-related lectin from a single species. Moreover, the identification of MornigaM provides the first evidence, to our knowledge, that bark cells accumulate large quantities of a cytoplasmic storage protein. In addition, due to its high activity, abundance, and ease of preparation, MornigaM is of great potential value for practical applications as a tool and bioactive protein in biological and biomedical research.
Van Damme, Els J.M.; Hause, Bettina; Hu, Jialiang; Barre, Annick; Rouge, Pierre; Proost, Paul; Peumans, Willy J.
The antiphospholipid syndrome is characterized clinically by fetal loss and thrombosis and serologically by the presence of autoantibodies to lipid-binding proteins. In a model of this procoagulant condition in which these antibodies are injected into pregnant mice, fetal loss was prevented by blocking of complement activation. Specifically, interaction of complement component 5a (C5a) with its receptor is necessary for thrombosis of placental vasculature (see the related article beginning on page 1644). Inhibition of complement activation may have a therapeutic role in this disease.
Atkinson, John P.
An extract from the seeds of Persea americana possessed an erythro-agglutinating activity. The agglutinin was devoid of specificity for carbohydrates, but interacted readily with basic proteins or basic polyamino acids. The interaction between the agglutinin and egg-white lysozyme was not inhibited by chaotropic salts, but was sensitive to relatively low concentrations of urea. An affinity chromatographic procedure was developed in an effort to purify the agglutinin. Products from the chromatographic procedure were found not to contain higher specific agglutinating activities than the crude extract. Amino acid acid analyses of the extract showed the presence of relatively high proportions of glutamic and aspartic acids. In addition, the extract contained phosphorus and a visible chromophore. The agglutinin was resistant to detergents and denaturants, and proteases, nucleases, and other enzymes. The results suggest that, as opposed to other plant agglutinins, the active component from Persea is not a protein. Similarly, in contrast to many lectins, the agglutinin from Persea was not mitogenic for mouse lymphocytes. The agglutinin partially inhibited the mitogenesis of lymphocytes when the cells were treated with concanavalin A, or with bacterial lipopolysaccharide. PMID:7353211
Meade, N A; Staat, R H; Langley, S D; Doyle, R J
Taste buds (TB) in the foliate, circumvallate and fungiform papillae of the rabbit tongue were examined with lectin histochemistry by means of light (LM) and electron (EM) microscopy. Biotin- and gold-labeled lectins were used for the detection of carbohydrate residues in TB cells and subcutaneous salivary glands. At the LM level, the lectins of soybean (SBA) and peanut (PNA) react
M. Witt; I. J. Miller
Soybean lectin labeled with fluorescein isothiocyanate combined specifically with all but 3 of 25 strains of the soybean-nodulating bacterium Rhizobium japonicum. The lectin did not bind to any of 23 other strains representative of rhizobia that do not nodulate soybeans. The evidence suggests that an interaction between legume lectins and Rhizobium cells may account for the specificity expressed between rhizobia
B. B. Bohlool; E. L. Schmidt
A recently described immunoenzymatic method for the quantitative determination of biologically active lectins in unknown samples has been adapted to measure the concentration of active soybean lectin (SBA) in foodstuffs. The method was developed by using purified SBA to build up reference standard curves and to determine the specificity and the sensitivity of the assay. Detectable amounts of soybean lectin
Corrado Rizzi; Luisa Galeoto; Gianni Zoccatelli; Simone Vincenzi; Roberto Chignola; Angelo D. B Peruffo
Characterization of the lectins from onion (Allium cepa), shallot (A. ascalonicum) and leek (A. porrum) has shown that these lectins differ from previously isolated Alliaceae lectins not only in their molecular structure but also in their ability to inhibit retrovirus infection of target cells.
Els J. M. Damme; Koen Smeets; Iris Engelborghs; Helen Aelbers; Jan Balzarini; Arpad Pusztai; Fred Leuven; Irwin J. Goldstein; Willy J. Peumans
With an ever-increasing wealth of information made available to researchers from expanding genomic sequence and protein structure databases, traditional experimentation and research are being drastically revisited. The unidirectional study of single molecules and pathways is being replaced by a combinatorial and cross-disciplinary platform that investigates interactive biological systems and dynamic networks. The complement system constitutes an ideal paradigm of how
D. Mastellos; D. Morikis; C. Strey; M. C. Holland; J. D. Lambris
Sialic-acid binding lectin (SBL) isolated from bullfrog (Rana catesbeiana) oocytes is a multifunctional protein which has lectin activity, ribonuclease activity and cancer-selective antitumor activity. It has been reported that SBL induces apoptosis accompanied by rigid mitochondrial perturbation, which indicates mediation of the intrinsic pathway. However, the mechanism of the antitumor effect of SBL has not been fully elucidated. We report, here, that ER stress is evoked in SBL-treated cells. We show that caspase-4, an initiator caspase of ER stress-mediated apoptosis was activated, and inhibition of caspase-4 resulted in significant attenuation of apoptosis induced by SBL. We analyzed the precise mechanism of activation of the caspase cascade induced by SBL, and found that caspase-9 and -4 are activated upstream of activation of caspase-8. Further study revealed that SBL induces the mitochondrial and ER stress-mediated pathways independently. It is noteworthy that SBL can induce cancer-selective apoptosis by multiple apoptotic signaling pathways, and it can serve as a candidate molecule for anticancer drugs in a novel field. PMID:24100413
Tatsuta, Takeo; Hosono, Masahiro; Miura, Yuki; Sugawara, Shigeki; Kariya, Yukiko; Hakomori, Senitiroh; Nitta, Kazuo
Lectins play an important role in immune recognition and host defense. In the present study, a full-length cDNA encoding a novel sialic acid binding lectin was cloned from Crassostrea hongkongensis (designated Ch-salectin) by rapid amplification of cDNA ends (RACE). It is 531 bp in length, containing a 21 bp 5' UTR, a 39 bp 3' UTR and a 468 bp ORF coding for 156 amino acids. The Ch-salectin protein contains a signal peptide and a conserved complement component C1q domain. The purified recombinant MBP-tagged Ch-salectin protein can bind to a sialic acid containing protein fetuin and significantly inhibit the growth of both Gram-negative and Gram-positive bacteria. Furthermore, the transcription of Ch-salectin was inducible and significantly up-regulated during Vibrio alginolyticus infection. Thus, these results highlight the essential roles of Ch-salectin in immune recognition and host defense against bacterial infection in C. hongkongensis. PMID:21906682
He, Xiaocui; Zhang, Yang; Yu, Feng; Yu, Ziniu
Herein, we identify and confirm differentially expressed sialoglycoproteins in the serum of patients with ovarian cancer. On the basis of Sambucus nigra (SNA) lectin enrichment and on an isobaric chemical labeling quantitative strategy, clusterin (CLUS), leucine-rich alpha-2-glycoprotein (LRG1), hemopexin (HEMO), vitamin D-binding protein (VDB), and complement factor H (CFH) were found to be differentially expressed in the serum of patients with ovarian cancer compared to benign diseases. The abnormal sialylation levels of CLUS, CFH, and HEMO in serum of ovarian cancer patients were verified by a lectin-based ELISA assay. ELISA assays were further applied to measure total protein level changes of these glycoproteins. Protein levels of CLUS were found to be down-regulated in the serum of ovarian cancer patients, while protein levels of LRG1 were increased. The combination of CLUS and LRG1 (AUC = 0.837) showed improved performance for distinguishing stage III ovarian cancer from benign diseases compared to CA125 alone (AUC = 0.811). In differentiating early stage ovarian cancer from benign diseases or healthy controls, LRG1 showed comparable performance to CA125. An independent sample set was further used to confirm the ability of these candidate markers to detect patients with ovarian cancer. Our study provides a comprehensive strategy for the identification of candidate biomarkers that show the potential for diagnosis of ovarian cancer. Further studies using a large number of samples are necessary to validate the utility of this panel of proteins. PMID:23731285
Wu, Jing; Xie, Xiaolei; Nie, Song; Buckanovich, Ronald J; Lubman, David M
Cellulose sulphate 50-600 ?g/ml reduces complement titres in human serum. This effect is, in contrast to the clot-promoting and plasma kinin forming action of cellulose sulphate, not mediated by clotting factor XII.
Eisen, V.; Loveday, C.
... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents Â§ 866.4100 Complement reagent. (a)...
The complement system of innate immunity is important in regulating humoral immunity largely through the complement receptor CR2, which forms a coreceptor on B cells during antigen-induced activation. However, CR2 also retains antigens on follicular dendritic cells (FDCs). Display of antigen on FDCs is critical for clonal selection and affinity maturation of activated B cells. This review will discuss the role of complement in adaptive immunity in general with a focus on the interplay between CR2-associated antigen on B cells with CR2 expressed on FDCs. This latter interaction provides an opportunity for memory B cells to sample antigen over prolonged periods. The cocrystal structure of CR2 with its ligand C3d provides insight into how the complement system regulates access of antigen by B cells with implications for therapeutic manipulations to modulate aberrant B cell responses in the case of autoimmunity. PMID:22921118
Carroll, Michael C; Isenman, David E
Previously we have investigated the interaction of human complement as well as one polyclonal and three human monoclonal antibody preparations with the human immunodeficiency virus type-1 (HIV-1) transmembrane recombinant glycoprotein (rgp41). A strong competition was found between the antibodies and deposited complement proteins for the same binding sites located within the immunodominant region of rgp41. The aim of the present experiments was to see if the same type of antibody-complement-HIV-1 interactions could be observed with the outer envelope glycoprotein (rgp120) of HIV-1. Three different glycosylated rgp120 preparations, as well as a synthetic peptide corresponding to the V3 loop of the MN strain, were adsorbed to enzyme-linked immunosorbent assay (ELISA) plates and incubated with mixtures of anti-rgp120 antibodies and normal human serum (NHS) as a complement source. Fixed complement proteins and antibodies were detected with specific, peroxidase-labelled antibodies against different complement proteins (C1q, C4b, C3b) and the gamma-chain of antibodies. In the absence of anti-rgp120, high amounts of C3 were deposited to each rgp120 preparation tested (including the V3 peptide) but significant differences in the amounts of bound C1q and C4b were observed. Using sera deficient in different complement proteins, we found that both the classical and the alternative pathways contributed to the C3 binding to rgp120. Addition of specific antibodies did not increase complement activation by rgp120 and only in the case of a monoclonal antibody to the V3-loop could we see complement-dependent inhibition of antibody binding.
Prohaszka, Z; Hidvegi, T; Ujhelyi, E; Stoiber, H; Dierich, M P; Susal, C; Fust, G
Lectins from Diocleinae subtribe belong to the family of legume lectins and are characterized by high identity between their amino acids sequences. It has been shown that punctual differences in amino acid sequences, such as one single amino acid or an alternative conformation, represent changes in biological activities caused by these lectins. Therefore, a more detailed understanding of three-dimensional structures of these proteins is essential for accurate analyzing the relationship between structure and function. In this study lectins purified from the seeds of Dioclea violacea (DVL) and Dioclea rostrata (DRL) were compared with regard to crystal structure and vasorelaxant properties. Differences in structure of lectins were found to be reflected in differences in vasorelaxant effects based on their high specificity and selectivity for cell glycans. Binding activity was related to the position of specific residues in the carbohydrate recognition domain (CRD). DVL complexed structure was solved by X-ray crystallography and was compared to native DVL and DRL. Therefore, DVL was co-crystallized with X-Man, and a molecular modeling with X-Man complexed with DVL was done to compare the complexed and native forms adjusted fit. The relatively narrow and deep CRD in DVL promotes little interaction with carbohydrates; in contrast, the wider and shallower CRD in DRL favors interaction. This seems to explain differences in the level of relaxation induced by DVL (43%) and DRL (96%) in rat aortic rings. PMID:23353644
Bezerra, Maria Júlia Barbosa; Rodrigues, Natália Velloso Fontenelle Camelo; Pires, Alana de Freitas; Bezerra, Gustavo Arruda; Nobre, Camila Bezerra; Alencar, Kássia Lys de Lima; Soares, Pedro Marcos Gomes; do Nascimento, Kyria Santiago; Nagano, Celso Shiniti; Martins, Jorge Luiz; Gruber, Karl; Sampaio, Alexandre Holanda; Delatorre, Plinio; Rocha, Bruno Anderson Matias; Assreuy, Ana Maria Sampaio; Cavada, Benildo Sousa
A novel, digital, single-operation analytical method to study glycodendrimer-lectin interactions is described. Robust, highly fluorescent derivatives of tris(bipyridine)ruthenieum(II) ([Ru(bipy)(3)](2+)) bearing 2, 4, 6, or 18 mannose or galactose units were designed to perform molecular logic operations. Inputs for these systems were pH, N,N'-4,4'-bis(benzyl-2-boronic acid)bipyridinium dibromide, and different lectins (concanavalin A, Galantus nivalis agglutinin, and asialoglycoprotein). The relative change in fluorescence quantum yield of the Ru(II)-glycodendrimers served as output. Together, the fluorescent emission readout, the logic analysis of the photoinduced electron transfer, and the optical behavior provide a single-step method to quickly screen a glycodendrimer library and select the best dendrimer model for studying carbohydrate-lectin interactions. PMID:20662498
Kikkeri, Raghavendra; Grünstein, Dan; Seeberger, Peter H
Some physicochemical properties of the L-fucose-binding lectin from the serum of the European eel (Anguilla anguilla) were determined. The lectin is a dimer composed of identical subunits of Mr approx. 40000. In agreement with previous results [Horejsí & Kocourek (1978) Biochim. Biophys. Acta 538, 299-315], the subunit was shown to comprise two non-glycosylated polypeptides of Mr approx. 20000 and linked by disulphide bonds. N-Terminal sequence analysis, carboxypeptidase digestion and peptide mapping indicated identity of the polypeptides. There were two L-fucose-binding sites per subunit with KD 1.6 X 10(-3) M for the lectin-fucose complex, as determined by equilibrium dialysis. Images Fig. 1.
This report describes a case of chronic fatigue syndrome (CFS) that followed a well-documented episode of acute Epstein–Barr virus (EBV) mononucleosis. All aetiological tests for chronic fatigue were found to be negative or normal, as were immunological tests. After 2 years of chronic fatigue following the acute illness, measurements of complement s