The Experts below are selected from a list of 3732 Experts worldwide ranked by ideXlab platform
Uday Kishore - One of the best experts on this subject based on the ideXlab platform.
-
the non Classical functions of the Classical Complement Pathway recognition subcomponent c1q
Immunology Letters, 2010Co-Authors: Annapurna Nayak, Janez Ferluga, Anthony G Tsolaki, Uday KishoreAbstract:C1q, the ligand recognition subcomponent of the Classical Complement Pathway has steadily been gaining recognition as a bridge between innate and adaptive immunity. C1q has been shown to be involved in the modulation of various immune cells (such as dendritic cells, platelets, microglia cells and lymphocytes), clearance of apoptotic cells, a range of cell processes such as differentiation, chemotaxis, aggregation and adhesion, and pathogenesis of neurodegenerative diseases and systemic lupus erythematosus. Recent studies have highlighted the importance of C1q during pregnancy, coagulation process and embryonic development including neurological synapse function. It is intriguing to note that a prototypical defence molecule has so many diverse functions that probably have its origin in its versatility as a potent charge pattern recognition molecule, modularity within the ligand-recognising globular domain, and the redundancy of putative C1q receptors. The range of function that C1q has been shown to perform also provides clues for the undiscovered functions of a number of C1q family members.
-
biochemical and functional characterization of the interaction between pentraxin 3 and c1q
European Journal of Immunology, 2003Co-Authors: Alma J Nauta, Uday Kishore, Alberto Mantovani, Barbara Bottazzi, Giovanni Salvatori, Wilhelm J Schwaeble, Alexandre R Gingras, Sotiria Tzima, Fernando VivancoAbstract:Pentraxin 3 (PTX3) is a recently characterized member of the pentraxin family of acute-phase proteins produced during inflammation. Classical short pentraxins, C-reactive protein, and serum amyloid P component can bind to C1q and thereby activate the Classical Complement Pathway. Since PTX3 can also bind C1q, the present study was designed to define the interaction between PTX3 and C1q and to examine the functional consequences of this interaction. A dose-dependent binding of both C1q and the C1 complex to PTX3 was observed. Experiments with recombinant globular head domains of human C1q A, B, and C chains indicated that C1q interacts with PTX3 via its globular head region. Binding of C1q to immobilized PTX3 induced activation of the Classical Complement Pathway as assessed by C4 deposition. Furthermore, PTX3 enhanced C1q binding and Complement activation on apoptotic cells. However, in the fluid-phase, pre-incubation of PTX3 with C1q resulted in inhibition of Complement activation by blocking the interaction of C1q with immunoglobulins. These results indicate that PTX3 can both inhibit and activate the Classical Complement Pathway by binding C1q, depending on the way it is presented. PTX3 may therefore be involved in the regulation of the innate immune response.
-
a recombinant homotrimer composed of the α helical neck region of human surfactant protein d and c1q b chain globular domain is an inhibitor of the Classical Complement Pathway
Journal of Immunology, 2001Co-Authors: Uday Kishore, Peter Strong, Michael V Perdikoulis, Kenneth B M ReidAbstract:The first step in the activation of the Classical Complement Pathway by immune complexes involves the binding of the six globular heads of C1q to the Fc regions of IgG or IgM. The globular heads of C1q (gC1q domain) are located C-terminal to the six triple-helical stalks present in the molecule, each head being composed of the C-terminal halves of one A, one B, and one C chain. The gC1q modules are also found in a variety of nonComplement proteins, such as type VIII and X collagens, precerebellin, hibernation protein, multimerin, Acrp-30, and saccular collagen. In several of these proteins, the chains containing these gC1q modules appear to form a homotrimeric structure. Here, we report expression of an in-frame fusion of a trimerizing neck region of surfactant protein D with the globular head region of C1q B chain as a fusion to Escherichia coli maltose binding protein. Following cleavage by factor Xa and removal of the maltose binding protein, the neck and globular region, designated ghB 3 , formed a soluble, homotrimeric structure and could inhibit C1q-dependent hemolysis of IgG- and IgM-sensitized sheep erythrocytes. The functional properties of ghB 3 indicate that the globular regions of C1q may adopt a modular organization in which each globular head of C1q may be composed of three structurally and functionally independent domains, thus retaining multivalency in the form of a heterotrimer. The finding that ghB 3 is an inhibitor of C1q-mediated Complement activation opens up the possibility of blocking activation at the first step of the Classical Complement Pathway.
Qiong Xue - One of the best experts on this subject based on the ideXlab platform.
-
activation of the Classical Complement Pathway by bacillus anthracis is the primary mechanism for spore phagocytosis and involves the spore surface protein bcla
Journal of Immunology, 2012Co-Authors: Sarah A Jenkins, Qiong XueAbstract:Interactions between spores of Bacillus anthracis and macrophages are critical for the development of anthrax infections, as spores are thought to use macrophages as vehicles to disseminate in the host. In this study, 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 Ca 2+ . 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 (Δ bclA ) was also significantly reduced compared with 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.
Jin Soo Joo - One of the best experts on this subject based on the ideXlab platform.
-
Dominant role of splenic marginal zone lipid rafts in the Classical Complement Pathway against S. pneumoniae.
Cell death discovery, 2019Co-Authors: Seung Woo Yang, Jin-yeon Park, Hyeong-jwa Choi, Tae Jin Yun, Woo-sung Choi, Min Kyung Kim, Yun Kyung Lee, Min Park, Yihwa Jin, Jin Soo JooAbstract:Lipid rafts (LRs) play crucial roles in complex physiological processes, modulating innate and acquired immune responses to pathogens. The transmembrane C-type lectins human dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and its mouse homolog SIGN-R1 are distributed in LRs and expressed on splenic marginal zone (MZ) macrophages. The DC-SIGN-C1q or SIGN-R1-C1q complex could mediate the immunoglobulin (Ig)-independent Classical Complement Pathway against Streptococcus pneumoniae. Precise roles of LRs during this Complement Pathway are unknown. Here we show that LRs are indispensable for accelerating the DC-SIGN- or SIGN-R1-mediated Classical Complement Pathway against S. pneumoniae, thus facilitating rapid clearance of the pathogen. The trimolecular complex of SIGN-R1-C1q-C4 was exclusively enriched in LRs of splenic MZ macrophages and their localization was essential for activating C3 catabolism and enhancing pneumococcal clearance, which were abolished in SIGN-R1-knockout mice. However, DC-SIGN replacement on splenic MZ macrophage's LRs of SIGN-R1-depleted mice reversed these defects. Disruption of LRs dramatically reduced pneumococcal uptake and decomposition. Additionally, DC- SIGN, C1q, C4, and C3 were obviously distributed in splenic LRs of cadavers. Therefore, LRs on splenic SIGN-R1+ or DC-SIGN+ macrophages could provide spatially confined and optimal bidirectional platforms, not only for usual intracellular events, for example recognition and phagocytosis of pathogens, but also an unusual extracellular event such as the Complement system. These findings improve our understanding of the orchestrated roles of the spleen, unraveling a new innate immune system initiated from splenic MZ LRs, and yielding answers to several long-standing problems, including the need to understand the profound role of LRs in innate immunity, the need to identify how such a small portion of splenic SIGN-R1+ macrophages (
-
dominant role of splenic marginal zone lipid rafts in the Classical Complement Pathway against s pneumoniae
Cell death discovery, 2019Co-Authors: Seung Woo Yang, Jin-yeon Park, Hyeong-jwa Choi, Tae Jin Yun, Woo-sung Choi, Min Kyung Kim, Yun Kyung Lee, Min Park, Yihwa Jin, Jin Soo JooAbstract:Lipid rafts (LRs) play crucial roles in complex physiological processes, modulating innate and acquired immune responses to pathogens. The transmembrane C-type lectins human dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and its mouse homolog SIGN-R1 are distributed in LRs and expressed on splenic marginal zone (MZ) macrophages. The DC-SIGN-C1q or SIGN-R1-C1q complex could mediate the immunoglobulin (Ig)-independent Classical Complement Pathway against Streptococcus pneumoniae. Precise roles of LRs during this Complement Pathway are unknown. Here we show that LRs are indispensable for accelerating the DC-SIGN- or SIGN-R1-mediated Classical Complement Pathway against S. pneumoniae, thus facilitating rapid clearance of the pathogen. The trimolecular complex of SIGN-R1-C1q-C4 was exclusively enriched in LRs of splenic MZ macrophages and their localization was essential for activating C3 catabolism and enhancing pneumococcal clearance, which were abolished in SIGN-R1-knockout mice. However, DC-SIGN replacement on splenic MZ macrophage's LRs of SIGN-R1-depleted mice reversed these defects. Disruption of LRs dramatically reduced pneumococcal uptake and decomposition. Additionally, DC- SIGN, C1q, C4, and C3 were obviously distributed in splenic LRs of cadavers. Therefore, LRs on splenic SIGN-R1+ or DC-SIGN+ macrophages could provide spatially confined and optimal bidirectional platforms, not only for usual intracellular events, for example recognition and phagocytosis of pathogens, but also an unusual extracellular event such as the Complement system. These findings improve our understanding of the orchestrated roles of the spleen, unraveling a new innate immune system initiated from splenic MZ LRs, and yielding answers to several long-standing problems, including the need to understand the profound role of LRs in innate immunity, the need to identify how such a small portion of splenic SIGN-R1+ macrophages (<0.05% of splenic macrophages) effectively resist S. pneumoniae, and the need to understand how LRs can promote the protective function of DC-SIGN against S. pneumoniae in the human spleen.
Peter Garred - One of the best experts on this subject based on the ideXlab platform.
-
Evasion of Classical Complement Pathway Activation on Plasmodium falciparum-Infected Erythrocytes Opsonized by PfEMP1-Specific IgG
Frontiers in Immunology, 2019Co-Authors: Mads Delbo Larsen, Maria Del Pilar Quintana, Sisse B. Ditlev, Rafael Bayarri-olmos, Michael F. Ofori, Lars Hviid, Peter GarredAbstract:Members of the PfEMP1 protein family are expressed on the surface of P. falciparum-infected erythrocytes (IEs), where they contribute to the pathogenesis of malaria and are important targets of acquired immunity. Although the PfEMP1-specific antibody response is dominated by the opsonizing and Complement-fixing subclasses IgG1 and IgG3, activation of the Classical Complement Pathway by antibody-opsonized IEs does not appear to be a major immune effector mechanism. To study the molecular background for this, we used ELISA and flow cytometry to assess activation of the Classical component Pathway by recombinant and native PfEMP1 antigen opsonized by polyclonal and monoclonal PfEMP1-specific human IgG. Polyclonal IgG specific for VAR2CSA-type PfEMP1 purified from a pool of human immune plasma efficiently activated the Classical Complement Pathway when bound to recombinant PfEMP1 in ELISA. In contrast, no activation of Complement could be detected by flow cytometry when the same IgG preparation was used to opsonize IEs expressing the corresponding native PfEMP1 antigen. After engineering of a VAR2CSA-specific monoclonal antibody to facilitate its on-target hexamerization, Complement activation was detectable in an ELISA optimized for uniform orientation of the immobilized antigen. In contrast, the antibody remained unable to activate Complement when bound to native VAR2CSA on IEs. Our data suggest that the display of PfEMP1 proteins on IEs is optimized to prevent activation of the Classical Complement Pathway, and thus represents a hitherto unappreciated parasite strategy to evade acquired immunity to malaria.
-
Data_Sheet_1_Evasion of Classical Complement Pathway Activation on Plasmodium falciparum-Infected Erythrocytes Opsonized by PfEMP1-Specific IgG.PDF
2019Co-Authors: Mads Delbo Larsen, Maria Del Pilar Quintana, Sisse B. Ditlev, Rafael Bayarri-olmos, Michael F. Ofori, Lars Hviid, Peter GarredAbstract:Members of the PfEMP1 protein family are expressed on the surface of P. falciparum-infected erythrocytes (IEs), where they contribute to the pathogenesis of malaria and are important targets of acquired immunity. Although the PfEMP1-specific antibody response is dominated by the opsonizing and Complement-fixing subclasses IgG1 and IgG3, activation of the Classical Complement Pathway by antibody-opsonized IEs does not appear to be a major immune effector mechanism. To study the molecular background for this, we used ELISA and flow cytometry to assess activation of the Classical component Pathway by recombinant and native PfEMP1 antigen opsonized by polyclonal and monoclonal PfEMP1-specific human IgG. Polyclonal IgG specific for VAR2CSA-type PfEMP1 purified from a pool of human immune plasma efficiently activated the Classical Complement Pathway when bound to recombinant PfEMP1 in ELISA. In contrast, no activation of Complement could be detected by flow cytometry when the same IgG preparation was used to opsonize IEs expressing the corresponding native PfEMP1 antigen. After engineering of a VAR2CSA-specific monoclonal antibody to facilitate its on-target hexamerization, Complement activation was detectable in an ELISA optimized for uniform orientation of the immobilized antigen. In contrast, the antibody remained unable to activate Complement when bound to native VAR2CSA on IEs. Our data suggest that the display of PfEMP1 proteins on IEs is optimized to prevent activation of the Classical Complement Pathway, and thus represents a hitherto unappreciated parasite strategy to evade acquired immunity to malaria.
Robert J. Boackle - One of the best experts on this subject based on the ideXlab platform.
-
Specific inhibition of the Classical Complement Pathway with an engineered single-chain Fv to C1q globular heads decreases Complement activation by apoptotic cells.
Immunobiology, 2009Co-Authors: Marcus R. Duvall, Hee Young Hwang, Robert J. BoackleAbstract:Abstract Apoptotic cells are potent Complement activators; and proposed mechanisms include IgM-mediated Classical Pathway activation, C-reactive protein (CRP)-mediated Classical Pathway activation, and IgM-mediated lectin Pathway activation. While Complement activation is beneficial in clearing apoptotic cells, the resulting Complement-mediated inflammation may extend damage to the surrounding cells and tissues, as observed in ischemia/reperfusion injury. We previously engineered and characterized a single-chain Fv against C1q globular heads (scFv QuVHVL ) that blocked C1q binding to immobilized IgG and to IgG-sensitized cells, and thereby inhibited IgG-mediated Classical Pathway activation [Hwang H.Y., Duvall M.R., Tomlinson S., Boackle R.J., 2008. Highly specific inhibition of C1q globular-head binding to human IgG: a novel approach to control and regulate the Classical Complement Pathway using an engineered single-chain antibody variable fragment. Molecular Immunology 45, 2570–2580]. In the present study, this scFv QuVHVL was examined for its ability to restrict Complement deposition on apoptotic cells in the presence of fresh normal human serum (NHS). Interestingly, the addition of scFv QuVHVL to NHS decreased C1-mediated C4b deposition on apoptotic cells by 60% as compared to appropriate buffer-treated control serum. By inhibiting initiation of the early Complement components, the subsequent C3b and membrane attack complex depositions were inhibited by 70%. Apoptotic cells may acquire serum CRP, a known Classical Complement Pathway activator. It was observed that scFv QuVHVL blocked C1 binding to CRP and blocked CRP-mediated Classical Pathway activation using an ELISA format. However, under the experimental conditions used, the addition of exogenous CRP to apoptotic cells did not further increase the levels of C4b, C3b, or MAC deposition significantly, suggesting predominance by other activation mechanisms, such as antibody-C1-mediated Complement activation. In summary, the results indicated that C1-mediated Classical Pathway activation was a highly significant mechanism for Complement activation by apoptotic cells. In the future, specific inhibition of Classical Complement Pathway activation by a humanized form of scFv QuVHVL may be useful in reducing inadvertent damage to healthy bystander tissue in a variety of acute, Complement-mediated inflammatory conditions, including ischemia/reperfusion injury.
-
Highly Specific Inhibition of C1q Globular-Head Binding to Human IgG: A Novel Approach to Control and Regulate the Classical Complement Pathway Using an Engineered Single Chain Antibody Variable Fragment
Molecular immunology, 2008Co-Authors: Hee Young Hwang, Marcus R. Duvall, Stephen Tomlinson, Robert J. BoackleAbstract:We sought to specifically regulate the binding of human C1q, and thus the activation of the first Complement component, via the construction of a single chain antibody variable binding region fragment (scFv) targeting the C1q globular heads. Here we describe details of the construction, expression and evaluation of this scFv, which was derived from a high-affinity hybridoma (Qu) specific for the C1q globular heads. The scFv was comprised of the Qu variable heavy chain domain (VH) linked to the Qu variable light chain domain (VL) and was termed scFv-QuVHVL. When mixed with either purified C1q or with human serum as a source of C1, scFv-QuVHVL bound to C1q and competitively restricted the interaction of C1q or C1 with immobilized IgG or with IgG1 antibody-coated cells, and prevented the activation of native C1 in human serum as determined by analyses of C1-mediated C4 deposition and fluid-phase C4 conversion. However scFv-QuVHVL could be manipulated to become a C1 activator when it was irreversibly immobilized onto microtiter ELISA plates, prior to contact with human serum Complement. This functional dichotomy can be a useful tool in selectively elucidating, differentiating, inducing or inhibiting specific roles of human C1q and the Classical Complement Pathway in Complement-mediated physiological processes. We project that once fully humanized, fluid-phase scFv-QuVHVL could become a useful therapeutic in limiting inadvertent host tissue damage elicited by the Classical Complement Pathway.