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Complement System (complement + system)
Selected AbstractsC5a anaphylatoxin as a product of complement activation up-regulates the complement inhibitory factor H in rat Kupffer cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 11 2004Gerald Schlaf Abstract The 155-kDa complement regulator factor H (FH) is the predominant soluble regulatory protein of the complement system. It acts as a cofactor for the factor I-mediated conversion of the component C3b to iC3b, competes with factor B for a binding site on C3b and C3(H2O) and promotes the dissociation of the C3bBb complex. The primary site of synthesis is the liver, i.e. FH-specific mRNA and protein were identified in both hepatocytes (HC) and Kupffer cells (KC). Previous studies in rat primary HC and KC had shown that the proinflammatory cytokine IFN-, influences the balance between activation and inhibition of the complement system through up-regulation of the inhibitory FH. In this study we show that C5a, as a product of complement activation, stimulates the expression of FH-specific mRNA and protein in KC and thus induces a negative feedback. Quantitative-competitive RT-PCR showed an approximate threefold C5a-induced up-regulation of FH. ELISA analyses revealed a corresponding increase in FH protein in the supernatants of KC. The up-regulation of FH was completely inhibited by the C5a-blocking monoclonal antibody 6-9F. Furthermore, an involvement of LPS and IFN-, was excluded, which strongly indicates a direct effect of C5a on the expression of FH in KC. [source] Mechanisms of blister induction by autoantibodiesEXPERIMENTAL DERMATOLOGY, Issue 12 2005Cassian Sitaru Abstract:, Autoimmune diseases are characterized by defined self-antigens, organ specificity, autoreactive T cells and/or autoantibodies that can transfer disease. Autoimmune blistering diseases are organ-specific autoimmune diseases associated with an immune response directed to structural proteins mediating cell,cell and cell,matrix adhesion in the skin. While both autoreactive T and B cells have been detected and characterized in patients with autoimmune blistering diseases, current evidence generally supports a pathogenic role of autoantibodies for blister formation. The immunopathology associated with blisters induced by autoantibodies relies on several mechanisms of action. Autoantibodies from patients with pemphigus diseases can exert a direct effect just by binding to their target mediated by steric hindrance and/or by triggering the transduction of a signal to the cell. In most subepidermal autoimmune blistering conditions, in addition to the binding to their target antigen, autoantibodies need to interact with factors of the innate immune system, including the complement system and inflammatory cells, in order to induce blisters. Generally, decisive progress has been made in the characterization of the mechanisms of blister formation in autoimmune skin diseases. However, various aspects, including the exact contribution of steric hindrance and signal transduction for pemphigus IgG-induced acantholysis or the fine tuning of the inflammatory cascade triggered by autoantibodies in some subepidermal blistering diseases, still need to be addressed. Understanding the mechanisms by which autoantibodies induce blisters should facilitate the development of more specific therapeutic strategies of autoimmune blistering diseases. [source] Allergy-like reactions to iodinated contrast agents.FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2005A critical analysis Abstract Allergy-like reactions may occur following administration of iodinated contrast media (CM), mostly in at-risk patients (patients with history of previous reaction, history of allergy, co-treated with interleukin-2 or beta-blockers, etc.) but remain generally unpredictable. Severe and fatal reactions are very rare events. All categories of CM may induce such reactions, although first generation (high osmolar CM) have been found to induce a higher rate of adverse events than low osmolar CM. However, no differences were found between the two categories of CM with respect to mortality. Delayed reactions can also occur. There are no differences between the various categories of CM except for non-ionic dimers, which are more likely to induce such effect. Numerous clinical studies have evaluated the prophylactic value of drugs (mostly antihistamines and corticosteroids). Results are unclear and highly variable. Any prevention depends upon the mechanism involved. However, the mechanism of CM-induced allergy-like reaction remains disputed. Relatively recent data revived the hypothesis of a type-I hypersensitivity mechanism. Positive skin tests to CM have been reported. However, the affinity of IgE towards CM has been found to be very low in the only study which actually evaluated it. Other pathophysiological mechanisms (involving direct secretory effects on mast cells or basophils, or activation of the complement system associated or not with the plasma contact system) are also much debated. Anaphylaxis and anaphylactoid reactions are, in the end, clinically undistinguishable. [source] Complement and its implications in cardiac ischemia/reperfusion: strategies to inhibit complementFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 5 2001Tiphaine Monsinjon Although reperfusion of the ischemic myocardium is an absolute necessity to salvage tissue from eventual death, it is also associated with pathologic changes that represent either an acceleration of processes initiated during ischemia or new pathophysiological changes that were initiated after reperfusion. This so-called ,reperfusion injury' is accompanied by a marked inflammatory reaction, which contributes to tissue injury. In addition to the well known role of oxygen free radicals and white blood cells, activation of the complement system probably represents one of the major contributors of the inflammatory reaction upon reperfusion. The complement may be activated through three different pathways: the classical, the alternative, and the lectin pathway. During reperfusion, complement may be activated by exposure to intracellular components such as mitochondrial membranes or intermediate filaments. Two elements of the activated complement contribute directly or indirectly to damages: anaphylatoxins (C3a and C5a) and the membrane attack complex (MAC). C5a, the most potent chemotactic anaphylatoxin, may attract neutrophils to the site of inflammation, leading to superoxide production, while MAC is deposited over endothelial cells and smooth vessel cells, leading to cell injury. Experimental evidence suggests that tissue salvage may be achieved by inhibition of the complement pathway. As the complement is composed of a cascade of proteins, it provides numerous sites for pharmacological interventions during acute myocardial infarction. Although various strategies aimed at modulating the complement system have been tested, the ideal approach probably consists of maintaining the activity of C3 (a central protein of the complement cascade) and inhibiting the later events implicated in ischemia/reperfusion and also in targeting inhibition in a tissue-specific manner. [source] Activation of the complement system in human nonalcoholic fatty liver disease,HEPATOLOGY, Issue 6 2009Sander S. Rensen Activation of the innate immune system plays a major role in nonalcoholic fatty liver disease (NAFLD). The complement system is an important component of innate immunity that recognizes danger signals such as tissue injury. We aimed to determine whether activation of the complement system occurs in NAFLD, to identify initiating pathways, and to assess the relation between complement activation, NAFLD severity, apoptosis, and inflammatory parameters. Liver biopsies of 43 obese subjects with various degrees of NAFLD and of 10 healthy controls were analyzed for deposition of complement factors C1q, mannose-binding lectin (MBL), C4d, activated C3, and membrane attack complex (MAC)-associated C9. Furthermore, hepatic neutrophil infiltration, apoptosis, and pro-inflammatory cytokine expression were quantified. Whereas complement activation was undetectable in the liver of healthy subjects, 74% of the NAFLD patients showed hepatic deposition of activated C3 and C4d. C1q as well as MBL accumulation was found in most activated C3-positive patients. Strikingly, 50% of activated C3-positive patients also displayed MAC-associated C9 deposition. Deposition of complement factors was predominantly seen around hepatocytes with macrovesicular steatosis. Subjects showing accumulation of activated C3 displayed increased numbers of apoptotic cells. Importantly, hepatic neutrophil infiltration as well as interleukin (IL)-8 and IL-6 expression was significantly higher in patients showing activated C3 deposition, whereas patients with C9 deposition additionally had increased IL-1, expression. Moreover, nonalcoholic steatohepatitis (NASH) was more prevalent in patients showing hepatic C9 or activated C3 deposition. Conclusion: There is widespread activation of the complement system in NAFLD, which is associated with disease severity. This may have important implications for the pathogenesis and progression of NAFLD given the function of complement factors in clearance of apoptotic cells, hepatic fibrosis, and liver regeneration. (HEPATOLOGY 2009.) [source] The lectin-complement pathway , its role in innate immunity and evolutionIMMUNOLOGICAL REVIEWS, Issue 1 2004Teizo Fujita Summary:, Innate immunity was formerly thought to be a non-specific immune response characterized by phagocytosis. However, innate immunity has considerable specificity and is capable of discriminating between pathogens and self. Recognition of pathogens is mediated by a set of pattern recognition receptors, which recognize conserved pathogen-associated molecular patterns (PAMPs) shared by broad classes of microorganisms, thereby successfully defending invertebrates and vertebrates against infection. Lectins, carbohydrate-binding proteins, play an important role in innate immunity by recognizing a wide range of pathogens. Mannose-binding lectin (MBL) and ficolin are lectins composed of a lectin domain attached to collagenous region. However, they use a different lectin domain: a carbohydrate recognition domain (CRD) is responsible for MBL and a fibrinogen-like domain for ficolin. These two collagenous lectins are pattern recognition receptors, and upon recognition of the infectious agent, they trigger the activation of the lectin-complement pathway through attached serine proteases, MBL-associated serine proteases (MASPs). A similar lectin-based complement system, consisting of the lectin,protease complex and C3, is present in ascidians, our closest invertebrate relatives, and functions in an opsonic manner. We isolated several lectins homologous to MBLs and ficolins and several MASPs in invertebrates and lower vertebrates, and herein we discuss the molecular evolution of these molecules. Based on these findings, it seems likely that the complement system played a pivotal role in innate immunity before the evolution of an acquired immune system in jawed vertebrates. [source] Primitive complement system of invertebratesIMMUNOLOGICAL REVIEWS, Issue 1 2004Masaru Nonaka Summary:, Most components of the human complement system have unmistakable domain architectures, making evolutionary tracing feasible. In contrast to the major genes of the adaptive immune system, which are present only in jawed vertebrates, complement component genes with unique domain structures are present not only in jawed vertebrates but also in jawless fish and non-vertebrate deuterostomes. Recent progress in genome analysis in several eukaryotes, occupying the phylogenetically critical positions, showed that most individual domains found in the complement components are metazoa specific, being found both in deuterostomes and in protostomes but not in yeast or plant. However, unique domain architecture of complement components is not present in protostomes, suggesting that the complement system has been established in the deuterostome lineage not by invention of new domains but by innovation of unique combination of the pre-existing domains. The recently assembled Ciona intestinalis draft genome contained the most modular complement genes, except for factor I. However, some possible C. intestinalis complement components show critical structural divergence from the mammalian counterparts, casting doubt on their mutual interaction. Thus, another integrative step seems to have been required to establish the modern complement system of higher vertebrates. [source] The ancestral complement system in sea urchinsIMMUNOLOGICAL REVIEWS, Issue 1 2001L. Courtney Smith Summary: The origin of adaptive immunity in the vertebrates can be traced to the appearance of the ancestral RAG genes in the ancestral jawed vertebrate; however, the innate immune system is more ancient. A central subsystem within innate immunity is the complement system, which has been identified throughout and seems to be restricted to the deuterostomes. The evolutionary history of complement can be traced from the sea urchins (members of the echinoderm phylum), which have a simplified system homologous to the alternative pathway, through the agnathans (hagfish and lamprey) and the elasmobranchs (sharks and rays) to the teleosts (bony fish) and tetrapods, with increases in the numbers of complement components and duplications in complement pathways. Increasing complexity in the complement system parallels increasing complexity in the deuterostome animals. This review focuses on the simplest of the complement systems that is present in the sea urchin. Two components have been identified that show significant homology to vertebrate C3 and factor B (Bf), called SpC3 and SpBf, respectively. Sequence analysis from both molecules reveals their ancestral characteristics. Immune challenge of sea urchins indicates that SpC3 is inducible and is present in coelomic fluid (the body fluids) in relatively high concentrations, while SpBf expression is constitutive and is present in much lower concentrations. Opsonization of foreign cells and particles followed by augmented uptake by phagocytic coelomocytes appears to be a central function for this simpler complement system and important for host defense in the sea urchin. These activities are similar to some of the functions of the homologous proteins in the vertebrate complement system. The selective advantage for the ancestral deuterostome may have been the amplification feedback loop that is still of central importance in the alternative pathway of complement in higher vertebrates. Feedback loop functions would quickly coat pathogens with complement leading to phagocytosis and removal of foreign cells, a system that would be significantly more effective than an opsonin that binds upon contact as a result of simple diffusion. An understanding of the immune response of the sea urchin, an animal that is a good estimator of what the ancestral deuterostome immune system was like, will aid us in understanding how adaptive immunity might have been selected for during the early evolution of the vertebrates and how it might have been integrated into the pre-existing innate immune system that was already in place in those animals. The authors are grateful to Drs Sham Nair and Paul Gross for their critique of the manuscript and helpful suggestions. This work was supported by the National Science Foundation (MCB 9603086). [source] Structure and biology of complement protein C3, a connecting link between innate and acquired immunityIMMUNOLOGICAL REVIEWS, Issue 1 2001Arvind Sahu Summary: Complement protein C3 is a central molecule in the complement system whose activation is essential for all the important functions performed by this system. After four decades of research it is now well established that C3 functions like a double-edged sword: on the one hand it promotes phagocytosis, supports local inflammatory responses against pathogens, and instructs the adaptive immune response to select the appropriate antigens for a humoral response; on the other hand its unregulated activation leads to host cell damage. In addition, its interactions with the proteins of foreign pathogens may provide a mechanism by which these microorganisms evade complement attack. Therefore, a clear knowledge of the molecule and its interactions at the molecular level not only may allow the rational design of molecular adjuvants but may also lead to the development of complement inhibitors and new therapeutic agents against infectious diseases. A.S. is a Wellcome Trust Overseas Senior Research Fellow in Biomedical Science in India. This research was supported by National Institutes of Health grants AI 30040, GM 56698, HL28220, and AI 48487. [source] Receptor for the globular heads of C1q (gC1q-R, p33, hyaluronan-binding protein) is preferentially expressed by adenocarcinoma cellsINTERNATIONAL JOURNAL OF CANCER, Issue 5 2004Daniel B. Rubinstein Abstract Combinatorial Ig libraries with phage display allow in vitro generation of human Ig fragments without the need to maintain hybridomas in ongoing cell culture or to select circulating Ig from human serum. Identifying tumor-associated antigens on the surface of intact tumor cells, as opposed to purified proteins, presents a challenge due to the difficulty of preserving complex 3-D epitopic sites on the cell surface, the variable expression of antigens on different malignant cell types and the stereotactic interference of closely associated proteins on the intact membrane surface limiting accessibility to antigenic sites. A combinatorial Ig library of 1010 clones was generated from the cDNA of PBMCs derived from patients with breast adenocarcinoma. Following subtractive panning, the library was enriched for Ig (Fab fragment) binding to intact adenocarcinoma cells and the resultant Fabs were screened against a cDNA expression library, itself generated from breast cancer cells. Using this approach, we isolated clones from the cDNA library expressing gC1q-R, a glycoprotein comprising the major structure of C1, the first component of the complement system. gC1q-R is a 33 kDa glycoprotein expressed not only on the cell surface but also intracellularly, with motifs that target it to mitochondria and complete homology with HABP and human HeLa cell protein p32, which is copurified with pre-mRNA SF2. Sequencing of the gene encoding tumor-associated gC1q-R did not reveal any consistent tumor-specific mutations. However, histochemical staining with anti-gC1q-R MAb demonstrated marked differential expression of gC1q-R in thyroid, colon, pancreatic, gastric, esophageal and lung adenocarcinomas compared to their nonmalignant histologic counterparts. In contrast, differential expression was not seen in endometrial, renal and prostate carcinomas. Despite high expression in breast carcinoma, gC1q-R was also expressed in nonmalignant breast tissue. Although the precise relation of gC1q-R to carcinogenesis remains unclear, our finding of tumor overexpression and the known multivalent binding of gC1q-R to not only C1q itself but also a variety of circulating plasma proteins as well as its involvement in cell-to-cell interactions suggest that gC1q-R may have a role in tumor metastases and potentially serve in molecule-specific targeting of malignant cells. © 2004 Wiley-Liss, Inc. [source] Induction of complement sensitivity in Escherichia coli by citric acid and low pHJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001C. Ocaña-Morgner Aims:,The lytic functions of the complement system play an important role in the control of Gram-negative infections. Complement-resistant Escherichia coli LP1395 (O18) grown under normal conditions can survive the bactericidal action of complement present in human serum. Towards elucidating the mechanisms of complement resistance, the resistance of E. coli LP1395 grown under conditions of low pH and in the presence of citric acid was tested. Methods and Results:,E. coli LP1395 becomes sensitive to complement after growth in the presence of citric acid at pH 5. Complement resistance could be restored when the cells were transferred to pH 7 media. However, this recovery was greatly impaired when the cells were transferred to pH 7 media with chloramphenicol. This implies that protein synthesis may be involved in complement resistance. The cells exposed to citric acid at pH 5 showed no indication of a generalized outer membrane (OM) permeability when compared with those grown under normal conditions in terms of sensitivity to lysozyme, uptake of lipophilic dye, or sensitivity to a number of antibiotics. Conclusions:,Complement-resistant LP1395 may acquire a sensitivity to complement due not to a generalized disruption of the OM barrier, but possibly to the alteration of the activity of one or more normal complement resistance factors. Significance and Impact of the Study:,The elucidation of the echanisms of complement resistance of Gram-negative pathogens would bring important information about bacterial infections. Complement resistance factors could also be potential targets in antimicrobial therapies. [source] Transient leukopenia and anaphylatoxin production during granulocyte apheresis as treatment for ulcerative colitisJOURNAL OF CLINICAL APHERESIS, Issue 3 2002Katsuhiko Yonemura Abstract It is well known that transient leukopenia due to activation of the alternative pathway of the complement system accompanies hemodialysis when cellulose acetate dialyzers are used. However, it has not been evaluated whether leukopenia also occurs during granulocyte apheresis (GCAP) as treatment for ulcerative colitis, in which an extracorporeal column is filled with cellulose acetate beads in order to remove circulating leukocytes. The aim of the present study was to evaluate whether transient leukopenia and activation of the alternative pathway of the complement system were observed during GCAP. In 8 patients undergoing GCAP weekly for 10 weeks, circulating leukocyte counts and plasma concentrations of C3a, a product of the activated alternative pathway of the complement system, were determined. GCAP elicited a rapid decline in the number of circulating leukocytes to 61.8 ± 13.8% of the baseline value after 15 minutes of GCAP (P < 0.02). Thereafter, the number of circulating leukocytes returned to approximately baseline after 60 minutes. The baseline plasma C3a concentration was 123 ± 61 ng/mL, and a significant increase to 425 ± 123 ng/mL was observed after 15 minutes of GCAP (P < 0.02). The plasma C3a concentration reached 417 ± 96 ng/mL after 60 minutes (P < 0.02). It thus follows that GCAP activates the alternative pathway of the complement system, resulting in anaphylatoxin production. J. Clin. Apheresis 17:107,110, 2002. © 2002 Wiley-Liss, Inc. [source] Atypical Aeromonas salmonicida infection in naturally and experimentally infected cod, Gadus morhua L.JOURNAL OF FISH DISEASES, Issue 10 2002B Magnadóttir Abstract Cod, Gadus morhua L., of wild origin, were reared at different temperatures for 12 months. During this period, moribund and newly dead fish were examined and samples collected for bacteriology and histopathology. Atypical Aeromonas salmonicida was isolated from 10 individuals reared at or above 7 °C. The isolates were homogeneous with respect to biochemical and antibiogram characters and similar to the ssp. achromogenes National Collection of Industrial and Marine Bacteria, UK, type strain 1110 and reference strains that have been isolated from salmonids and haddock in Iceland. Histopathological analysis of the naturally infected cod showed typical ulceration associated with atypical A. salmonicida infection and also widespread granulomatous formations. One-year-old cod of farmed origin, kept at 9 °C, received intraperitoneal or intramuscular injection with different doses of atypical A. salmonicida, isolated from the above wild cod. Mortalities were monitored for 28 days and the LD50 calculated. The route of bacterial injection influenced the mortality rate and LD50 value and affected, to some extent, the pathological changes observed and humoral immune parameters. Pathological changes, including haemorrhage, early stages of granuloma formation and necrotic changes, were seen in several organs. Infection appeared to induce non-specific antibody activity against trinitrophenyl (TNP)-haptenated protein and may have activated the complement system. Specific antibody response against atypical A. salmonicida was not detected. [source] Comparative study of eight well-known polyphenolic antioxidantsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2003P. Cos ABSTRACT Eight antioxidants from five different polyphenolic classes (cinnamic acids, benzoic acids, flavonoids, proanthocyanidins and stilbenes), and the water-soluble vitamin E derivative trolox were examined for their antioxidant activity in-vitro. In addition, the compounds were tested for their cytotoxicity on growing fibroblasts and their inhibition of the classical pathway of the complement system. Procyanidin C1 was shown to be a good scavenger of both DPPH* and HO*, and a strong inhibitor of lipid peroxidation and the classical pathway of the complement system. Consequently, procyanidin C1 was classified as the most promising antioxidant in-vitro of all compounds tested. In contrast, genistein exhibited a very low antioxidant activity in both the lipid peroxidation and the DPPH* scavenging assay, a high cytotoxicity and a low complement-inhibiting activity. [source] The membrane attack complex (C5b-9) in liver cold ischemia and reperfusion injuryLIVER TRANSPLANTATION, Issue 8 2008Constantino Fondevila Activation of the complement cascade represents an important event during ischemia/reperfusion injury (IRI). This work was designed to investigate the role of the membrane attack complex (MAC; C5b-9) in the pathogenesis of hepatic IRI. Livers from B&W/Stahl/rC6(+) and C6(,) rats were harvested, stored for 24 hours at 4°C, and then transplanted [orthotopic liver transplantation (OLT)] to syngeneic recipients. There were 4 experimental groups: (1) C6(+),C6(+), (2) C6(+),C6(,), (3) C6(,),C6(+), and (4) C6(,),C6(,). At day +1, C6(,) OLTs showed decreased vascular congestion/necrosis, contrasting with extensive necrosis in C6(+) livers, that was independent of the recipient C6 status (Suzuki score: 7.2 ± 0.9, 7.3 ± 1.3, 4.5 ± 0.6, and 4.8 ± 0.4 for groups 1-4, respectively, P < 0.05). The liver function improved in recipients of C6(,) grafts (serum glutamic oxaloacetic transaminase: 2573 ± 488, 1808 ± 302, 1170 ± 111, and 1188 ± 184 in groups 1-4, respectively, P < 0.05). Intragraft macrophage infiltration (ED-1 immunostaining) and neutrophil infiltration (myeloperoxidase activity) were reduced in C6(,) grafts versus C6(+) grafts (P = 0.001); these data were confirmed by esterase staining (naphthol). The expression of proinflammatory interferon-,, interleukin-1,, and tumor necrosis factor messenger RNA/protein was also reduced in C6(,) OLTs in comparison with C6(+) OLTs. Western blot,assisted expression of proapoptotic caspase-3 was decreased in C6(,) OLTs versus C6(+) OLTs (P = 0.006), whereas antiapoptotic Bcl-2/Bag-1 was enhanced in C6(,) OLTs compared with C6(+) OLTs (P = 0.001). Terminal deoxynucleotidyl transferase,mediated dUTP nick end-labeling staining of apoptotic cells was enhanced (P < 0.05) in C6(+) OLTs compared with C6(,) OLTs. Thus, the terminal products of the complement system are essential in the mechanism of hepatic IRI. This is the first report using a clinically relevant liver cold ischemia model to show that local MAC inhibition attenuates IRI cascade in OLT recipients. Liver Transpl 14:1133,1141, 2008. © 2008 AASLD. [source] Release and characterization of single side chains of white cabbage pectin and their complement-fixing activityMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 6 2009Bjorge Westereng Abstract A mixture of single side chains from white cabbage pectin were obtained by anion exchange chromatography after applying mild chemical conditions promoting ,-elimination. These pectin fragments were characterized by their molecular weight distribution, sugar composition, 13C-NMR, and MALDI-TOF-MS analysis. These analyses revealed that the large oligosaccharides released by ,-eliminative treatment were composed of ,-1,5 linked arabinosyl residues with 2- and 3-linked ,-arabinosyl side chains, and, or ,-1,4 linked galactosyl side chains. Fractions were tested for complement-fixing activity in order to determine their interaction with the complement system. These results strongly indicated that there was a minimal unit size responsible for the complement-fixing activity. Neutral pectin fragments (,8 kDa) obtained from ,-elimination were inactive in the complement system, although they contained a sugar composition previously shown to be highly active. Larger pectin fragments (,17 kDa) retained some activity, but much lower than polymers containing rhamnogalacturonan type 1 (RGI) structures isolated from the same source. This implied that structural elements containing multiple side chains is necessary for efficient complement-fixing activity. [source] Complement and fungal pathogens: an updateMYCOSES, Issue 6 2008Cornelia Speth Summary Fungal infections are a serious complication in immunocompromised patients such as human immunodeficiency virus-infected individuals, patients with organ transplantations or with haematological neoplasia. The lethality of opportunistic fungal infection is high despite a growing arsenal of antimycotic drugs, implying the urgent need for supportive immunological therapies to strengthen the current inefficient antimicrobial defences of the immunocompromised host. Therefore, increasing effort has been directed to investigating the interplay between fungi and the host immunity and thus to find starting points for additional therapeutic approaches. In this article, we review the actual state of the art concerning the role of complement in the pathogenesis of fungal infections. Important aspects include the activation of the complement system by the fungal pathogen, the efficiency of the complement-associated antimicrobial functions and the arsenal of immune evasion strategies applied by the fungi. The twin functions of complement as an interactive player of the innate immunity and at the same time as a modulator of the adaptive immunity make this defence weapon a particularly interesting therapeutic candidate to mobilise a more effective immune response and to strengthen in one fell swoop a broad spectrum of different immune reactions. However, we also mention the ,Yin-Yang' nature of the complement system in fungal infections, as growing evidence assigns to complement a contributory part in the pathogenesis of fungus-induced allergic manifestations. [source] Analysis of block matrix preconditioners for elliptic optimal control problemsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 4 2007T. P. Mathew Abstract In this paper, we describe and analyse several block matrix iterative algorithms for solving a saddle point linear system arising from the discretization of a linear-quadratic elliptic control problem with Neumann boundary conditions. To ensure that the problem is well posed, a regularization term with a parameter , is included. The first algorithm reduces the saddle point system to a symmetric positive definite Schur complement system for the control variable and employs conjugate gradient (CG) acceleration, however, double iteration is required (except in special cases). A preconditioner yielding a rate of convergence independent of the mesh size h is described for , , R2 or R3, and a preconditioner independent of h and , when , , R2. Next, two algorithms avoiding double iteration are described using an augmented Lagrangian formulation. One of these algorithms solves the augmented saddle point system employing MINRES acceleration, while the other solves a symmetric positive definite reformulation of the augmented saddle point system employing CG acceleration. For both algorithms, a symmetric positive definite preconditioner is described yielding a rate of convergence independent of h. In addition to the above algorithms, two heuristic algorithms are described, one a projected CG algorithm, and the other an indefinite block matrix preconditioner employing GMRES acceleration. Rigorous convergence results, however, are not known for the heuristic algorithms. Copyright © 2007 John Wiley & Sons, Ltd. [source] Role of Complement Anaphylatoxin C3a in Photodynamic Therapy-elicited Engagement of Host Neutrophils and Other Immune CellsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2006Ivana Cecic ABSTRACT Tumor treatment by photodynamic therapy (PDT) provokes a host-protective inflammatory and acute-phase response and an immune reaction. Neutrophilia manifested in this context is driven by multiple mediators of neutrophil chemotaxis orchestrated by an activated complement system. Mouse FsaR fibrosarcoma was used in this study to further investigate neutrophilia induced by Photofrin-based PDT. The complement anaphylatoxin C3a was identified as a major chemo-attractant in the advanced phase of PDT-induced neutrophilia, because injecting mice with antibodies blocking its receptor C3aR significantly inhibited the increase in neutrophil levels 8 h after PDT. At the same time point, an increased C3aR expression was detected in neutrophils, monocytes and B lymphocytes in the blood of host mice. Peritoneal macro-phages and mast cells harvested from treatment-naive mice exhibited elevated C3aR expression after coincubation in vitro for 8 h with PDT-treated FsaR cells. Thus, C3a emerges as one of the key effector molecules engaged in PDT-induced host response. [source] Characterisation of new oligoglycosidic compounds in two Chinese medicinal herbsPHYTOCHEMICAL ANALYSIS, Issue 4 2002Sandra Apers Abstract A series of caffeic acid derivatives (3,5-dicaffeoyl-quinic acid, 3,4-dicaffeoyl-quinic acid, and 4,5-dicaffeoyl-quinic acid), and the new compound ,,3,4-trihydroxyphenethyl- O -[,-apiofuranosyl-(1,4)-,-rhamnopyranosyl-(1,3)]-(4- O -caffeoyl)-,-glucopyranoside (wedelosin), as well as three known flavonoid glycosides (quercetin 3- O -,-glucoside, kaempferol 3- O -,-apiosyl-(1-2)-,-glucoside, and astragalin or kaempferol 3- O -,-glucoside) were isolated from the Chinese medicinal herb Wedelia chinensis. Wedelosin showed an inhibitory activity on both the classical and the alternative activation pathway of the complement system. Another Chinese medicinal herb, Kyllinga brevifolia, yielded two known flavonoid glycosides [kaempferol 3- O -,-apiosyl-(1-2)-,-glucoside and isorhamnetin 3- O -,-apiosyl-(1-2)-,-glucoside], and a new quercetin triglycoside [quercetin 3- O -,-apiofuranosyl-(1,2)-,-glucopyranoside 7- O -,-rhamnopyranoside]. The latter compound showed a moderate anti-viral activity. Copyright © 2002 John Wiley & Sons, Ltd. [source] Flavonoids from the leaves of Litsea japonica and their anti-complement activityPHYTOTHERAPY RESEARCH, Issue 4 2005Sun-Young Lee Abstract Four flavonoids, epicatechin (1), afzelin (2), quercitrin (3), and tiliroside (4), were isolated from the leaves of Litsea japonica (Thunb.) Jussieu (Lauraceae). The structures of compounds were identified by comparing their chemical and spectral data with those previously reported. The flavonoids (1,4) were tested for their anti-complement activity against classical pathway of complement system. Compounds 2,4 showed inhibitory activity against complement system with IC50 values of 258, 440, and 101 µm, respectively, whereas 1 was inactive. For the evaluation of the structure-activity relationship of 5,7-dihydroxyflavones, myricitrin (5) from Juglans mandshurica also tested for it's anti-complement activity and is inactive in this assay system. Furthermore, compounds 2, 3, and 5 were hydrolyzed with naringinase to give kaempferol (2a), quercetin (3a), and myricetin (5a), and these were also tested for their activity. Of the three aglycones, 2a exhibited anti-complement activity with an IC50 value of 730 µM, while 3a and 5a were inactive. The inhibitory potencies of 2, 2a, 3, 3a, 5, and 5a against complement activity increased in inverse proportion to number of free hydroxyls on B-ring of 5,7-dihydroxyflavone. Of the compounds tested, 4 showed the most potent inhibitory activity against the complement system. Copyright © 2005 John Wiley & Sons, Ltd. [source] Proteomic analysis of high-density lipoproteinPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2006Farhad Rezaee Dr. Abstract Plasma lipoproteins, such as high-density lipoprotein (HDL), can serve as carriers for a wide range of proteins that are involved in processes such as lipid metabolism, thrombosis, inflammation and atherosclerosis. The identification of HDL-associated proteins is essential with regards to understanding these processes at the molecular level. In this study, a combination of proteomic approaches including 1-DE and 2-DE MALDI-TOF, isotope-coded affinity tag and Western blot analysis were employed to identify proteins associated with human HDL. To minimize potential losses of HDL-associated proteins during isolation, a one-step ultracentrifugation technique was applied and the quality of purified HDL was confirmed by nephelometry, high-performance gel chromatography, and Western blot analysis. MS analysis revealed the presence of 56 HDL-associated proteins including all known apolipoproteins and lipid transport proteins. Furthermore, proteins involved in hemostasis and thrombosis, the immune and complement system were found. In addition, growth factors, receptors, hormone-associated proteins and many other proteins were found to be associated with HDL. Our approach thus resulted in the identification of a large number of proteins associated with HDL. The combination of proteomic technologies proved to be a powerful and comprehensive tool for the identification of proteins on HDL. [source] MS characterization of apheresis samples from rheumatoid arthritis patients for the improvement of immunoadsorption therapy , a pilot studyPROTEOMICS - CLINICAL APPLICATIONS, Issue 7 2009Mike Kienbaum Abstract Identification of proteins from apheresis samples was performed by both SDS-PAGE and 2-D gel separation of eluted proteins from staphylococcal protein A-based immunoadsorption columns (Prosorba®) followed by MS peptide mass fingerprinting and MS/MS peptide sequencing on a MALDI QIT TOF mass spectrometer. MS/MS peptide sequencing was performed in conjunction with a micro reversed phase HPLC configured with an online MALDI plate-spotting device. Apheresis treatment had been performed in three patients with longstanding therapy refractory rheumatoid arthritis. 2-D gels displayed ca. 500 spots representing proteins that were eluted from the Prosorba® columns. From 54 gels, a total of 1256 protein spots had been picked and yielded in the identification of 56 non-redundant proteins without counting isoforms. Proteins from the eluates belong to five major groups comprising (i) immunoglobulins (IgG, IgA, IgM heavy and light chains; about 40% of the spots), (ii) proteins involved in coagulation, (iii) HDL/LDL-associated proteins, (iv) proteins from the complement system, and (v) acute phase proteins. MS analysis showed that the full-length C3 complement protein had been cleaved upon complement activation, presumably on the column, such that the anaphylatoxin C3a was produced and released during therapy. Our results are consistent with clinical observations on both patient responses to therapy and reported adverse events. For the first time, direct molecular information has become available to support mechanistic reasoning for the principle of function of staphylococcal protein A-based immunoadsorption therapy and for the explanation of adverse events. According to our results, removal and/or modulation of immune complexes together with complement activation can be regarded as the major events that are taking place during Prosorba® therapy. In order to avoid complement activation and induction of an inflammatory cascade, we suggest the prevention of C3a anaphylatoxin-related reactions during immunoadsorption therapy. [source] ORIGINAL ARTICLE: Activation of the Alternative Pathway of Complement is a Feature of Pre-Term Parturition but not of Spontaneous Labor at TermAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 4 2010Edi Vaisbuch Citation Vaisbuch E, Romero R, Erez O, Mazaki-Tovi S, Kusanovic JP, Soto E, Dong Z, Chaiworapongsa T, Kim SK, Ogge G, Pacora P, Yeo L, Hassan SS. Activation of the alternative pathway of complement is a feature of pre-term parturition but not of spontaneous labor at term. Am J Reprod Immunol 2010; 63: 318,330 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 pre-term delivery <34 weeks of gestation. The aim of this study was to determine whether spontaneous pre-term labor (PTL) with intact membranes, 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: (i) non-pregnant (n = 40); (ii) normal pregnancy (gestational age range 20,36, 6/7 weeks, n = 63); (iii) women at term not in labor (n = 70); (iv) women at term in spontaneous labor (n = 59); (v) patients with an episode of PTL who delivered at term (n = 62); (vi) PTL without IAI who delivered pre-term (n = 30); and (vii) PTL with IAI who delivered pre-term (n = 67). Maternal plasma FBb concentrations were determined by ELISA. Results, (i) Among patients with PTL, those who had a pre-term 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); (ii) there was no difference in the median plasma FBb concentration between patients with and without IAI who delivered pre-term (P = 0.9); (iii) in contrast, spontaneous labor at term was not associated with a significant change in the maternal plasma FBb concentration (P = 0.8); (iv) 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). Conclusion, (i) Pre-term parturition is associated with activation of the alternative complement pathway in maternal circulation; (ii) such activation is not detectable in spontaneous labor at term; (iii) IAI does not explain the activation of the alternative pathway of complement in PTL. Collectively, these observations suggest that pre-term and term labors have fundamental differences in the regulation of innate immunity. [source] The contact/kinin and complement systems in vasculitisAPMIS, Issue 2009DIANA KARPMAN Vasculitides are a group of conditions with marked inflammation in and around vessel walls and vascular leakage. These conditions may involve the presence of auto-antibodies such as ANCA or may be mediated by other autoimmune or pathogenic mechanisms. Regardless of the primary trigger, vasculitides entail activation of the complement system as well as the contact/kinin system. In vivo and in vitro data support the involvement of these systems showing activation of the alternative, classical and lectin complement pathways as well as release of bradykinin at sites of vascular inflammation. This short review will summarize some of the data regarding the participation of these systems and the interplay between the complement and kinin systems as well as their interaction with the endothelium and neutrophils. Although these systems do not play a primary role in induction of vasculitis, the peptides released contribute to inflammation and vascular leakage and may thus be identified as potential therapeutic targets. [source] Deletion of either CD55 or CD97 ameliorates arthritis in mouse modelsARTHRITIS & RHEUMATISM, Issue 4 2010Robert M. Hoek Objective CD55 (decay-accelerating factor) is best known for its role in the negative regulation of the complement system. Indeed, lack of this molecule leads to disease aggravation in many autoimmune disease models. However, CD55 is abundantly present on fibroblast-like synoviocytes and is also a ligand of the adhesion-class heptahelical receptor CD97, which is expressed by infiltrating macrophages. Treatment with antibodies to CD97 ameliorates the collagen-induced model of rheumatoid arthritis (RA) in DBA/1 mice, but the net contribution of CD55 is unknown. This study was undertaken to investigate the role of CD55 in experimental RA. Methods Arthritis was induced in wild-type, CD55,/,, and CD97,/, mice using collagen-induced and K/BxN serum,transfer models. Incidence of arthritis was monitored over time, and disease activity was assessed by clinical and immunohistochemical evaluation. Results In contrast to observations in many inflammatory disease models, lack of CD55 resulted in decreased arthritis in experimental models of RA. Consistent with the previously reported effects of anti-CD97 antibody treatment, CD97,/, mice had reduced arthritis activity compared with wild-type controls. Conclusion Our findings indicate that the lack of CD55 or CD97 in 2 different models of arthritis increases resistance to the disease. These findings provide insight into a role for CD55 interaction with CD97 in the pathogenesis of RA and suggest that therapeutic strategies that disrupt CD55/CD97 may be clinically beneficial. [source] Anti,cyclic citrullinated peptide antibodies from rheumatoid arthritis patients activate complement via both the classical and alternative pathwaysARTHRITIS & RHEUMATISM, Issue 7 2009L. A. Trouw Objective It has been suggested that anti,citrullinated protein antibodies (ACPAs) play an important role in the pathogenesis of rheumatoid arthritis (RA). To exert their pathologic effects, ACPAs must recruit immune effector mechanisms such as activation of the complement system. Mouse models of RA have shown that, surprisingly, arthritogenic antibodies activate the alternative pathway of complement rather than the expected classical pathway. This study was undertaken to investigate whether human anti,cyclic citrullinated peptide (anti-CCP) antibodies activate the complement system in vitro and, if so, which pathways of complement activation are used. Methods We set up novel assays to analyze complement activation by anti-CCP antibodies, using cyclic citrullinated peptide,coated plates, specific buffers, and normal and complement-deficient sera as a source of complement. Results Anti-CCP antibodies activated complement in a dose-dependent manner via the classical pathway of complement, and, surprisingly, via the alternative pathway of complement. The lectin pathway was not activated by anti-CCP antibodies. Complement activation proceeded in vitro up to the formation of the membrane attack complex, indicating that all activation steps, including the release of C5a, took place. Conclusion Our findings indicate that anti-CCP antibodies activate the complement system in vitro via the classical and alternative pathways but not via the lectin pathway. These findings are relevant for the design of interventions aimed at inhibition of complement-mediated damage in RA. [source] In Vitro Biocompatibility Evaluation of the Dynamic Bubble TrapARTIFICIAL ORGANS, Issue 8 2003Uwe Taborski Abstract:, The goal of this study was to evaluate the biocompatibility of the dynamic bubble trap (DBT) prior to the clinical trial. It was set up as an in vitro model, which simulates physiological conditions. Twenty runs were performed (ten with the DBT, ten without the DBT) at a blood flow of 3 L/min, each lasting 180 min. Fifteen blood parameters (hemogram, hemostasis, complement system, and cytokines) were measured at five time intervals. None of the tested parameters showed a statistically significant difference between the DBT and control group. The data assessed in this in vitro model show that the DBT has no adverse influence on hemocompatibility. It may be concluded that the DBT is a safe tool to be used in vivo. [source] Ex Vivo Biocompatibility of Avidin-Agarose: A New Device for Direct Adsorption of Biotinylated Antibodies from Human Whole BloodARTIFICIAL ORGANS, Issue 9 2000T. Bosch Abstract: Radioimmunotherapy using radiolabeled antitumor antibodies (RAA) is limited by the toxicity of unbound antibodies in the circulation. Removal of excessive antibodies by affinity-adsorption could therefore allow the administration of increased dosages of RAA while decreasing their adverse effects. Recently, avidin-agarose (AA) minicolumns were used in animal experiments for the removal of biotinylated antibodies from whole blood exploiting the high affinity binding of biotin to avidin (pK 1015 M,1). This study was performed to evaluate the ex vivo biocompatibility of AA minicolumns with human blood. Ten ml AA minicolumns were perfused online ex vivo in the single pass mode with fresh blood from 8 healthy donors at a flow rate of 6.25 ml/min. The anticoagulation consisted of 0.5 IU heparin plus 0.0,2.1 mg citrate per ml of blood. In Part 1 of the study (40 min perfusion, n = 4), the optimal anticoagulation was found to be 0.5 IU heparin plus about 1 mg citrate per ml of blood. In Part 2 of the study, four 80 min test-runs were performed. No signs of hemolysis were found, and the thrombogenicity of the AA gel was negligible. Cell counts and column inlet pressures remained constant; toward the end of the 80 min test-runs, some activation of blood cells (elastase, ,-thromboglobulin), the complement system (C3a, C5a) and the plasmatic coagulation (thrombin-antithrombin complex) was detectable. A moderate initial bradykinin release rapidly subsided to very low levels. In summary, AA minicolumns showed good biocompatibility upon contact with human whole blood and merit further investigation in a closed-loop system for a potential application of direct tumor antibody removal by hemoperfusion. [source] Importance of Uniform Heparin Coating on BiopolymersARTIFICIAL ORGANS, Issue 3 2000Patrícia Da Luz Moreira Abstract: Cardiopulmonary surgeries need connectors for extracorporeal circulation. The patient's blood in contact with the tube surfaces modifies its plasmatic proteins, promotes platelet aggregation, and activates the complement system, unleashing thrombus formation. Thus, it becomes necessary for an anticoagulant to keep the circuit free from these events. Heparin is the anticoagulant used even after reports about its disadvantages. Platelet adherence seems to be very dependent on the quality from the surfaces that can promote cellular proliferation, aggregation, and thrombosis. In this study, we compare the quality of the heparin-coated and uncoated surfaces. We used a blood cell culture and scanning electron microscopy (SEM) to visualize the platelet aggregation. It was concluded that there are groove areas that permit platelet adherence, and if they are not coated totally by the heparin, aggregation still occurs although in lower scale than on the uncoated tubes. [source] | |||||||||||||||||||||||||||||||||||||