scholarly journals A Role for Complement in Feedback Enhancement of Antibody Responses by IgG3

2003 ◽  
Vol 197 (9) ◽  
pp. 1183-1190 ◽  
Author(s):  
Teresita Díaz de Ståhl ◽  
Jörgen Dahlström ◽  
Michael C. Carroll ◽  
Birgitta Heyman
Keyword(s):  
Feedback Regulation ◽  
Antibody Responses ◽  
Complement Factor ◽  
Complement Receptors ◽  
Wild Type ◽  
Gamma Chain ◽  
The Common ◽  
Feedback Enhancement ◽  
Complement Factor C3 ◽  
The Complement System

IgG1, IgG2a, and IgG2b, passively administered with soluble Ags, enhance specific Ab responses. The effect of IgG3 in this type of feedback regulation has not been studied previously. We immunized mice with trinitrophenyl (TNP)-coupled carrier proteins (bovine serum albumin [BSA] or ovalbumin [OVA]) alone or complexed to monoclonal TNP-specific IgG3. The carrier-specific Ab responses were enhanced by several hundred-fold by IgG3. Enhancement was significantly impaired in mice depleted of complement factor C3 and in mice lacking complement receptors 1 and 2 (Cr2−/−). In contrast, mice lacking the common Fc-receptor gamma chain (FcRγ−/−), resulting in reduced expression of FcγRI and lack of FcγRIII, and mice lacking FcγRIIB (FcγRIIB−/−), responded equally well to immunization with IgG3-complexed Ag as wild-type controls. These findings demonstrate that IgG3 can induce feedback enhancement and that IgG3, in analogy with IgM, uses the complement system for this function.

scholarly journals A novel approach to immunoapheresis of C3a/C3 and proteomic identification of associates

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e8218
Author(s):  
Wolfgang Winnicki ◽  
Peter Pichler ◽  
Karl Mechtler ◽  
Richard Imre ◽  
Ines Steinmacher ◽  
...  
Keyword(s):  
Complement System ◽  
Proteomic Analysis ◽  
Methodological Approach ◽  
Central Component ◽  
Complement Factor ◽  
Immunoaffinity Column ◽  
Novel Approach ◽  
Human Disorders ◽  
Complement Factor C3 ◽  
The Complement System

Background Complement factor C3 represents the central component of the complement cascade and its activation split product C3a plays an important role in inflammation and disease. Many human disorders are linked to dysregulation of the complement system and alteration in interaction molecules. Therefore, various therapeutic approaches to act on the complement system have been initiated. Methods and Results Aiming to develop a tool to eliminate C3a/C3 from the circulation, in a first step a high affine murine monoclonal antibody (mAb) (3F7E2-mAb) was generated against complement factor C3 and selected for binding to the C3a region to serve as immunoaffinity reagent. Functional testing of the 3F7E2-mAb revealed an inhibition of Zymosan-induced cleavage of C3a from C3. Subsequently, a C3a/C3 specific 3F7E2-immunoaffinity column was developed and apheresis of C3a/C3 and associates was performed. Finally, a proteomic analysis was carried out for identification of apheresis products. C3a/C3 was liberated from the 3F7E2-column together with 278 proteins. C3a/C3 interaction specificity was validated by using a haptoglobin immunoaffinity column as control and biostatistic analysis revealed 39 true C3a/C3 interactants. Conclusion A novel and functionally active mAb was developed against complement factor C3a/C3 and used in a specific immunoaffinity column that allows apheresis of C3a/C3 and associates and their identification by proteomic analysis. This methodological approach of developing specific antibodies that can be used as immunoaffinity reagents to design immunoaffinity columns for elimination and further identification of associated proteins could open new avenues for the development of tailored immunotherapy in various complement-mediated or autoimmune diseases.

scholarly journals Role of the Classical Pathway of Complement Activation in Experimentally Induced Polymicrobial Peritonitis

2001 ◽  
Vol 69 (12) ◽  
pp. 7304-7309 ◽  
Author(s):  
Ilhan Celik ◽  
Cordula Stover ◽  
Marina Botto ◽  
Steffen Thiel ◽  
Sotiria Tzima ◽  
...  
Keyword(s):  
Complement System ◽  
Complement Activation ◽  
Immune Defense ◽  
Classical Pathway ◽  
Complement Factor ◽  
Wild Type ◽  
Factor B ◽  
The Complement System ◽  
Deficient Mice

ABSTRACT The complement system and the natural antibody repertoire provide a critical first-line defense against infection. The binding of natural antibodies to microbial surfaces opsonizes invading microorganisms and activates complement via the classical pathway. Both defense systems cooperate within the innate immune response. We studied the role of the complement system in the host defense against experimental polymicrobial peritonitis using mice lacking either C1q or factor B and C2. The C1q-deficient mice lacked the classical pathway of complement activation. The factor B- and C2-deficient mice were known to lack the classical and alternative pathways, and we demonstrate here that these mice also lacked the lectin pathway of complement activation. Using inoculum doses adjusted to cause 42% mortality in the wild-type strain, none of the mice deficient in the three activation routes of complement (factor B and C2 deficient) survived (mortality of 100%). Mortality in mice deficient only in the classical pathway of complement activation (C1q deficient) was 83%. Application of further dilutions of the polymicrobial inoculum showed a dose-dependent decrease of mortality in wild-type controls, whereas no changes in mortality were observed in the two gene-targeted strains. These results demonstrate that the classical activation pathway is required for an effective antimicrobial immune defense in polymicrobial peritonitis and that, in the infection model used, the remaining antibody-independent complement activation routes (alternative and lectin pathways) provide a supporting line of defense to gain residual protection in classical pathway deficiency.

scholarly journals Francisella tularensis Enters Macrophages via a Novel Process Involving Pseudopod Loops

2005 ◽  
Vol 73 (9) ◽  
pp. 5892-5902 ◽  
Author(s):  
Daniel L. Clemens ◽  
Bai-Yu Lee ◽  
Marcus A. Horwitz
Keyword(s):  
Francisella Tularensis ◽  
Host Cells ◽  
Live Vaccine Strain ◽  
Complement Factor ◽  
Complement Receptors ◽  
Human Macrophages ◽  
Life Threatening ◽  
Infectious Pathogen ◽  
Complement Factor C3 ◽  
Uptake Mechanisms

ABSTRACT Intracellular bacterial pathogens employ a variety of strategies to invade their eukaryotic host cells. From an ultrastructural standpoint, the processes that bacteria employ to invade their host cells include conventional phagocytosis, coiling phagocytosis, and ruffling/triggered macropinocytosis. In this paper, we describe a novel process by which Francisella tularensis, the agent of tularemia, enters host macrophages. F. tularensis is a remarkably infectious facultative intracellular bacterial parasite—as few as 10 bacteria can cause life-threatening disease in humans. However, the ultrastructure of its uptake and the receptor mechanisms that mediate its uptake have not been reported previously. We have used fluorescence microscopy and electron microscopy to examine the adherence and uptake of a virulent recent clinical isolate of F. tularensis, subspecies tularensis, and the live vaccine strain (LVS), subspecies holarctica, by human macrophages. We show here that both strains of F. tularensis enter human macrophages by a novel process of engulfment within asymmetric, spacious pseudopod loops, a process that differs ultrastructurally from all previously described uptake mechanisms. We demonstrate also that adherence and uptake of F. tularensis by macrophages is strongly dependent upon complement receptors and upon serum with intact complement factor C3 and that uptake requires actin microfilaments. These findings have significant implications for understanding the intracellular biology and virulence of this extremely infectious pathogen.

scholarly journals Phosphorylation of complement factor C3 in vivo

1989 ◽  
Vol 261 (3) ◽  
pp. 1051-1054 ◽  
Author(s):  
S C Martin
Keyword(s):  
Complement System ◽  
Whole Blood ◽  
Complement Factor ◽  
S Protein ◽  
Atp Concentration ◽  
Central Protein ◽  
Complement Factor C3 ◽  
The Complement System

Complement factor C3, the central protein of the complement system, was found to be phosphorylated both in EDTA- and heparin-anticoagulated whole blood and in coagulating blood. Complement S protein (vitronectin) was also found to be phosphorylated under these conditions. Further, purified C3 was found to be a phosphoprotein in vivo, containing 0.15 mol of alkali-labile phosphate/mol of protein. The ATP concentration in plasma was measured and found to be about 2 microM.

scholarly journals Complement Factor C7 Contributes to Lung Immunopathology Caused byMycobacterium tuberculosis

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Kerry J. Welsh ◽  
Cole T. Lewis ◽  
Sydney Boyd ◽  
Michael C. Braun ◽  
Jeffrey K. Actor
Keyword(s):  
Post Infection ◽  
Critical Role ◽  
Complement Factor ◽  
Wild Type ◽  
Knock Out ◽  
Host Protection ◽  
Colony Forming Units ◽  
Knock Out Mice ◽  
The Complement System

Mycobacterium tuberculosis(MTB) remains a significant global health burden despite the availability of antimicrobial chemotherapy. Increasing evidence indicates a critical role of the complement system in the development of host protection against the bacillus, but few studies have specifically explored the function of the terminal complement factors. Mice deficient in complement C7 and wild-type C57BL/6 mice were aerosol challenged with MTB Erdman and assessed for bacterial burden, histopathology, and lung cytokine responses at days 30 and 60 post-infection. Macrophages isolated from C7 −/− and wild-type mice were evaluated for MTB proliferation and cytokine production. C7 −/− mice had significantly less liver colony forming units (CFUs) at day 30; no differences were noted in lung CFUs. The C7 deficient mice had markedly reduced lung occlusion with significantly increased total lymphocytes, decreased macrophages, and increased numbers of CD4+ cells 60 days post-infection. Expression of lung IFN-γand TNF-αwas increased at day 60 compared to wild-type mice. There were no differences in MTB-proliferation in macrophages isolated from wild-type and knock-out mice. These results indicate a role for complement C7 in the development of MTB induced immunopathology which warrants further investigation.

scholarly journals Complement factor H contributes to mortality in humans and mice with bacterial meningitis

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
E. Soemirien Kasanmoentalib ◽  
Mercedes Valls Serón ◽  
Joo Yeon Engelen-Lee ◽  
Michael W. Tanck ◽  
Richard B. Pouw ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Bacterial Meningitis ◽  
Mouse Model ◽  
Adjuvant Treatment ◽  
Complement System ◽  
Pneumococcal Meningitis ◽  
Factor H ◽  
Complement Factor ◽  
Wild Type ◽  
The Complement System

Abstract Background The complement system is a vital component of the inflammatory response occurring during bacterial meningitis. Blocking the complement system was shown to improve the outcome of experimental pneumococcal meningitis. Complement factor H (FH) is a complement regulatory protein inhibiting alternative pathway activation but is also exploited by the pneumococcus to prevent complement activation on its surface conferring serum resistance. Methods In a nationwide prospective cohort study of 1009 episodes with community-acquired bacterial meningitis, we analyzed whether genetic variations in CFH influenced FH cerebrospinal fluid levels and/or disease severity. Subsequently, we analyzed the role of FH in our pneumococcal meningitis mouse model using FH knock-out (Cfh−/−) mice and wild-type (wt) mice. Finally, we tested whether adjuvant treatment with human FH (hFH) improved outcome in a randomized investigator blinded trial in a pneumococcal meningitis mouse model. Results We found the major allele (G) of single nucleotide polymorphism in CFH (rs6677604) to be associated with low FH cerebrospinal fluid concentration and increased mortality. In patients and mice with bacterial meningitis, FH concentrations were elevated during disease and Cfh−/− mice with pneumococcal meningitis had increased mortality compared to wild-type mice due to C3 depletion. Adjuvant treatment of wild-type mice with purified human FH led to complement inhibition but also increased bacterial outgrowth which resulted in similar disease outcomes. Conclusion Low FH levels contribute to mortality in pneumococcal meningitis but adjuvant treatment with FH at a clinically relevant time point is not beneficial.

scholarly journals Impaired Immunogenicity of Meningococcal Neisserial Surface Protein A in Human Complement Factor H Transgenic Mice

2015 ◽  
Vol 84 (2) ◽  
pp. 452-458 ◽  
Author(s):  
Eduardo Lujan ◽  
Rolando Pajon ◽  
Dan M. Granoff
Keyword(s):  
Transgenic Mice ◽  
Outer Membrane ◽  
Protein A ◽  
Surface Protein ◽  
Factor H ◽  
Antibody Responses ◽  
Complement Factor ◽  
Wild Type ◽  
Protective Antibody ◽  
Bactericidal Antibody

Neisserial surface protein A (NspA) is a highly conserved outer membrane protein previously investigated as a meningococcal vaccine candidate. Despite eliciting serum bactericidal activity in mice, a recombinant NspA vaccine failed to elicit serum bactericidal antibodies in a phase 1 clinical trial in humans. The discordant results may be explained by the recent discovery that NspA is a human-specific ligand of the complement inhibitor factor H (FH). Therefore, in humans but not mice, NspA would be expected to form a complex with FH, which could impair human anti-NspA protective antibody responses. To investigate this question, we immunized human FH transgenic BALB/c mice with three doses of recombinant NspA expressed inEscherichia colimicrovesicles, with each dose being separated by 3 weeks. Three of 12 (25%) transgenic mice and 13 of 14 wild-type mice responded with bactericidal titers of ≥1:10 in postimmunization sera (P= 0.0008, Fisher's exact test). In contrast, human FH transgenic and wild-type mice immunized with a control meningococcal native outer membrane vesicle vaccine had similar serum bactericidal antibody responses directed at PorA, which is not known to bind human FH, and a mutant factor H binding protein (FHbp) antigen with a >50-fold lower level of FH binding than wild-type FHbp antigen binding.Thus, human FH can impair anti-NspA serum bactericidal antibody responses, which may explain the poor immunogenicity of the NspA vaccine previously tested in humans. A mutant NspA vaccine engineered to have decreased binding to human FH may increase protective antibody responses in humans.

scholarly journals A meningococcal vaccine antigen engineered to increase thermal stability and stabilize protective epitopes

2015 ◽  
Vol 112 (48) ◽  
pp. 14823-14828 ◽  
Author(s):  
Monica Konar ◽  
Rolando Pajon ◽  
Peter T. Beernink
Keyword(s):  
Thermal Stability ◽  
Electrostatic Interactions ◽  
Double Mutant ◽  
Factor H ◽  
Antibody Responses ◽  
Vaccine Antigen ◽  
Complement Factor ◽  
Wild Type ◽  
Protective Antibody ◽  
Terminal Domain

Factor H binding protein (FHbp) is part of two vaccines recently licensed for prevention of sepsis and meningitis caused by serogroup B meningococci. FHbp is classified in three phylogenic variant groups that have limited antigenic cross-reactivity, and FHbp variants in one of the groups have low thermal stability. In the present study, we replaced two amino acid residues, R130 and D133, in a stable FHbp variant with their counterparts (L and G) from a less stable variant. The single and double mutants decreased thermal stability of the amino- (N-) terminal domain compared with the wild-type protein as measured by scanning calorimetry. We introduced the converse substitutions, L130R and G133D, in a less stable wild-type FHbp variant, which increased the transition midpoint (Tm) for the N-terminal domain by 8 and 12 °C; together the substitutions increased the Tm by 21 °C. We determined the crystal structure of the double mutant FHbp to 1.6 Å resolution, which showed that R130 and D133 mediated multiple electrostatic interactions. Monoclonal antibodies specific for FHbp epitopes in the N-terminal domain had higher binding affinity for the recombinant double mutant by surface plasmon resonance and to the mutant expressed on meningococci by flow cytometry. The double mutant also had decreased binding of human complement Factor H, which in previous studies increased the protective antibody responses. The stabilized mutant FHbp thus has the potential to stabilize protective epitopes and increase the protective antibody responses to recombinant FHbp vaccines or native outer membrane vesicle vaccines with overexpressed FHbp.

scholarly journals C3 Deficiency Leads to Increased Angiogenesis and Elevated Pro-Angiogenic Leukocyte Recruitment in Ischemic Muscle Tissue

2021 ◽  
Vol 22 (11) ◽  
pp. 5800
Author(s):  
Philipp Götz ◽  
Anna Braumandl ◽  
Matthias Kübler ◽  
Konda Kumaraswami ◽  
Hellen Ishikawa-Ankerhold ◽  
...  
Keyword(s):  
Muscle Tissue ◽  
Complement System ◽  
Neutrophil Extracellular Trap ◽  
Complement Factor ◽  
Artery Ligation ◽  
Complement Factor C3 ◽  
Gastrocnemius Muscles ◽  
The Impact ◽  
The Complement System ◽  
Ischemic Muscle

The complement system is a potent inflammatory trigger, activator, and chemoattractant for leukocytes, which play a crucial role in promoting angiogenesis. However, little information is available about the influence of the complement system on angiogenesis in ischemic muscle tissue. To address this topic and analyze the impact of the complement system on angiogenesis, we induced muscle ischemia in complement factor C3 deficient (C3−/−) and wildtype control mice by femoral artery ligation (FAL). At 24 h and 7 days after FAL, we isolated the ischemic gastrocnemius muscles and investigated them by means of (immuno-)histological analyses. C3−/− mice showed elevated ischemic damage 7 days after FAL, as evidenced by H&E staining. In addition, angiogenesis was increased in C3−/− mice, as demonstrated by increased capillary/muscle fiber ratio and increased proliferating endothelial cells (CD31+/BrdU+). Moreover, our results showed that the total number of leukocytes (CD45+) was increased in C3−/− mice, which was based on an increased number of neutrophils (MPO+), neutrophil extracellular trap formation (MPO+/CitH3+), and macrophages (CD68+) displaying a shift toward an anti-inflammatory and pro-angiogenic M2-like polarized phenotype (CD68+/MRC1+). In summary, we show that the deficiency of complement factor C3 increased neutrophil and M2-like polarized macrophage accumulation in ischemic muscle tissue, contributing to angiogenesis.

Sign in / Sign up

Export Citation Format

Share Document