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PubMed1977

Complement (C5-a)-induced granulocyte aggregation in vitro. A possible mechanism of complement-mediated leukostasis and leukopenia.

Activated plasma complement will induce biphasic aggregation of human granulocytes dectable by standard nephelometric techniques. The responsible active component was suggested to be C5a by molecular weight and heat-stability assays; moreover, aggragating activity was ablated by anti-C5 but not anti-C3 antibodies. C5a prepared by trypsinization of purified C5 reproduced the aggregating activity of whole activated plasma, whereas plasma from a C5-deficient donor did not support aggregation. Embolization of granulocyte aggregates might be a previously unsuspected cause of leukostasis and pulmonary damage in various clinical situations where intravascular complement activation occurs.

Cell Aggregation↗
PubMed1984

Effects of dextran sulphate (DXS) on lymphocyte localization in complement-deficient mice: evidence that the fifth component of complement is not implicated in the DXS activity.

The effects of subcutaneously or intraperitoneally administered dextran sulphate (DXS) (50 mg/Kg) on the subsequent 1 h localization of intravenously injected radiolabelled lymph node cells was investigated in complement deficient mice which lack C5. DXS proved to be equally as potent in depressing cell localization in deficient as compared to normal mice. These findings indicate that the terminal complement components are not essential for DXS activity.

Animals↗
PubMed1975

Complement inhibitor(s) released by leukocytes. I. Pretreatment of sheep erythrocytes with supernatants of mouse spleen and thymus cells inhibit whole complement activity and C2 utilization.

Sheep erythrocytes pretreated with supernatants of mouse spleen or thymus cells become resistant to lysis by guinea pig complement. The inhibitory activity (IA) reduces the utilization of C2 by EAC14. Because IA binds to the surface of sheep erythrocytes and does not inhibit C1 irreversibly, it is probably a hitherto undescribed inhibitor of complement.

Animals↗
PubMed2003

[The specificity of interaction between the complement and the lipopolysaccharide with a low activity of the complement (hypothesis)].

Interactions between the complement with a low activity and the lipopolysacharide (LPS) with an extensive concentration range were experimentally investigated in vitro. A model was suggested that provides an explanation to the concentration-related dependence. The complement and LPS were shown, under certain conditions, to form the membrane-attacking complexes, which are not bound with the bacterium membrane and which can lyse any cells. Damages made by the above complexes to endothelial cells of the vessels could result in the onset of the syndrome of disseminated intravascular coagulation (DIC). The results can be used to develop a method applicable to evaluating a concentration of endotoxin and to creating anti-tumor drugs.

Animals↗
PubMed1990

Independent association of serum amyloid P component, protein S, and complement C4b with complement C4b-binding protein and subsequent association of the complex with membranes.

C4b-binding protein (C4BP) is a large complex assembly of eight subunits that functions as an inhibitor of the complement cascade. A portion of the C4BP in serum exists as a complex with protein S. This study demonstrated that another protein, serum amyloid P component (SAP), also formed a calcium-dependent complex with C4BP. The C4BP.SAP complex was detected by several methods including light scattering intensity, gel filtration, and sucrose density gradient ultracentrifugation. This complex was of high affinity relative to serum levels of these proteins so that no dissociation was detected at 3% of serum protein concentrations. The C4BP.SAP complex was also detected in normal serum and the results suggested that there was virtually no free SAP or uncomplexed C4BP in normal serum. In addition to its complex with C4BP, SAP underwent other calcium-dependent associations such as binding to phospholipid vesicles and self-aggregation. Self-aggregation was highly cooperative with kinetics corresponding to a reaction that was 6th-order with respect to calcium and required about 1.5 mM calcium. In contrast, formation of the SAP.C4BP complex and interaction of SAP with membranes required only about 0.4 and 1.0 mM calcium, respectively. Thus, selection of the correct conditions allowed study of the SAP.C4BP interaction without interference from self-aggregation. All three of these interactions of SAP were mutually exclusive and the SAP. C4BP interaction appeared to be favored over self-aggregation or binding of SAP to phospholipids. It seems likely that the biologically dominant interaction for SAP is with C4BP. The SAP.C4BP complex interacted with protein S and these binding sites appeared to be entirely independent. Furthermore, SAP had little or no effect on the ability of C4BP to bind C4b. Finally, the entire complex of proteins (C4BP, SAP, protein S, and C4b) could associate with membranes in the presence of calcium. Membrane binding occurred through the protein S component. This rather complicated assemblage of proteins probably functions in a regulatory role for the complement cascade or other biological systems. It is possible that elevated levels of SAP or nonequivalent levels of SAP and C4BP could contribute to certain pathological conditions.

Calcium↗
PubMed1987

Complement effects of the infectivity of Plasmodium gallinaceum to Aedes aegypti mosquitoes. II. Changes in sensitivity to complement-like factors during zygote development.

During transformation into ookinetes, the zygotes of Plasmodium gallinaceum are initially resistant to lysis by heat-labile and EDTA-sensitive factors in the serum of their natural host, the chicken. Between 6 and 8 hr postgametogenesis, zygotes cultured in vitro lose their resistance to these factors. Loss of resistance to these factors in vitro is reflected by loss of infectivity of the zygotes to Aedes aegypti mosquitoes in the presence of native chicken serum. These factors are probably components of the alternative pathway of complement (APC) of chicken serum. Gametocytes of P. gallinaceum in chicken blood are able to infect A. aegypti mosquitoes apparently due to inactivation of the APC in a blood meal within 3-4 hr after ingestion, i.e., several hours before the zygotes lose their resistance to chicken APC. In addition to the heat-labile factors (APC) in chicken serum, the zygotes are transiently sensitive to other factor(s) in the mosquito blood meal. These factor(s) are not destroyed by prior heating of the chicken serum given in a blood meal and therefore cannot be complement components. The antiparasitic effects of the factors are neutralized by addition of EDTA to the blood meal and could be due to an EDTA-sensitive metalloprotease present in the mosquito midgut.

Aedes↗
PubMed1979

Complement receptor analogous factors in human serum: I. Isolation of a molecule inhibitory for complement dependent rosette formation, its identification as alpha 1-antitrypsin and its functional characterization.

A glycoprotein was isolated from human plasma which partially inhibited C3 carrying erythrocytes from binding to complement receptor cells (CR+C). Based on its physicochemical characteristics and its antigenicity this glycoprotein was identified as alpha 1-antitrypsin (alpha 1-AT). The activity of alpha 1-AT towards C3 and its fragments was unaffected by heating but it was destroyed by periodic acid. The isolated carbohydrate moiety of alpha 1-AT showed the same effect as the intact molecule. Using F(ab)2 of IgG-anti-alpha 1-AT could be demonstrated on Raji cells and human erythrocytes. Treatment of these CR+C with IgG-anti-alpha 1-AT resulted in a blockade of their C3 receptor activity. The results suggest, that alpha 1-AT interacts through its carbohydrate portion with C3 and its fragments and functions as a complement receptor molecule.

B-Lymphocytes↗
PubMed1983

Hemolytic complement titers and complement C3 levels in endotoxin-induced mastitis.

Escherichia coli lipopolysaccharide B was instilled through the lactiferous duct of cows to induce acute mastitis. Hemolytic complement (C) activity and C3 concentrations were determined in blood serum and in renninprecipitated whey before, and at certain times after, mastitis was induced. Hemolytic complement activity was detected in the whey only during the first 36 hours after endotoxin was instilled, whereas activity was not seen before and 48 or more hours after the endotoxin was given. The maximum titer as measured with the guinea pig RBC/bovine natural antibody system was 1:64. The C3 concentrations in normal whey (before installation of endotoxin), measured by radial immunodiffusion, were between 1% and 4% of the base-line blood serum values (pool from healthy cows). The whey concentration of C3 increased (to 5% to 18%) during the first 8 hours of mastitis. However, at 72 hours, the whey values were back to preinstillation concentrations in all quarters.

Animals↗
PubMed1980

[Effects of intrapartum steroid prophylaxis on complement C3 and total complement activities (author's transl)].

One single high dose of dexamethasone (0.5 mg/kg body weight) was administered to a mother, before tests started into the effects of such approach upon the serum total complement (CH 50) and C-3 levels in the mother's umbilical cord blood. Neither CH 50 nor C-3 complement had declined with significance 48 hours from steroid administration. Significant reduction was observed only in cases in which six hours elapsed between steroid administration and childbirth.

Complement C3↗
PubMed1995

Mutation of residues in the C3dg region of human complement component C3 corresponding to a proposed binding site for complement receptor type 2 (CR2, CD21) does not abolish binding of iC3b or C3dg to CR2.

Most evidence points toward there being a shared binding site in complement receptor type 2 (CR2, CD21) for the complement ligand C3dg and the EBV surface envelope glycoprotein gp350/220. Indeed, synthetic peptide studies have suggested that the CR2-binding sites in human C3dg and EBV gp350/220 share a similar sequence motif. The proposed CR2-binding sequence in C3dg is EDPGKQLYNVEA (residues 1199-1210 of mature C3), whereas that in EBV gp350/220 is EDPGFFNVEI (residues identical to C3dg are underlined). To further examine the role of amino acids 1199-1210 in the binding of the C3 fragments iC3b and C3dg to CR2, the following alanine-substitution variants of human C3 were tested in two independent CR2-binding assays: ED1199,1200AA; KQ1203,1204AA; L1205A; Y1206A; NV1207,1208AA; E1209A; and ED-KQ-NV1199,1200-1203,1204-1207,1208AA-AA-AA. Also engineered and tested was a chimeric C3 molecule in which the 1199-1210 sequence (PVPGGYQLTLEA) from the non-CR2-binding trout C3 molecule was grafted onto a human C3 background. Recombinant C3 proteins were expressed transiently in COS-1 cells, deposited as C3b on C3 convertase-bearing sheep erythrocytes and finally converted to cell-bound iC3b or C3dg using factors H and I. Binding of EAC423bi and EAC423dg to CR2 on Raji cells or EAC423dg to soluble CR2 was assessed. In most cases, the substitutions had little effect on CR2-binding activity and even in the case of the most highly substituted variants, the decrease in CR2-binding activity was less than twofold. Thus, contrary to the results anticipated from synthetic peptide studies, the single and multiple substitutions to the C3 sequence tested failed to corroborate a role for the 1199-1210 sequence in the C3dg-CR2 interaction.

Amino Acid Sequence↗
PubMed1993

Expression of the complement classical pathway by human glioma in culture. A model for complement expression by nerve cells.

In this paper we demonstrate the synthesis of the components of the classical complement pathway, namely C1q, C1r, C1s, C1-Inh, C2, C4, and C5, by human glioma cell lines (U118MG, T193, and T98G). All these components were structurally, antigenically, and functionally similar to their serum counterparts as determined by biosynthetic labeling experiments, Western blot analysis, and hemolytic assays. Northern blot analysis of mRNA demonstrated that, for each of these components, their specific mRNA had the same size as the equivalent mRNA from hepatic tissue. We could not detect the synthesis of C4bp by these cell lines, and the secretion of C1q was only detected after stimulation by interferon-gamma. All these syntheses were up-regulated by interferon-gamma and tumor necrosis factor. Interleukin-1 beta only increased C2 expression and reproducibly down-regulated C5 secretion when used at high doses. Glioma cell lines appear to be an efficient and convenient model for the analysis of complement expression in human astrocytic cells.

Astrocytes↗
PubMed1983

Studies of the mechanism of bacterial resistance to complement-mediated killing. V. IgG and F(ab')2 mediate killing of E. coli 0111B4 by the alternative complement pathway without increasing C5b-9 deposition.

The mechanism of antibody-dependent complement-(C) mediated killing of Escherichia coli 0111B4, strain 12015 (12015), was examined. 12015 was resistant to serum killing when incubated in hypogammaglobulinemic serum (H gamma S) or pooled normal human serum (NHS) that had been previously adsorbed to remove specific antibody (Abs NHS). Presensitization with immune rabbit serum or purified immune rabbit IgG resulted in 1 to 3 log killing when 5 X 10(8) colony forming units (CFU)/ml were incubated in 10 to 40% Abs NHS. Binding of 125I-C3 and 131I-C9 to the bacterial surface of the presensitized and the nonpresensitized strain was quantitated when these organisms were incubated in 10, 20, and 40% Abs NHS. Stable binding of up to 3.0 X 10(5) molecules of C3 and 8.0 X 10(4) molecules of C9 to presensitized and nonpresensitized isolates occurred in the highest concentration of serum, but there was no killing without presensitization. Similar results were found when Abs NHS was chelated with ethylene bis glycoltetraacetic acid containing 2 mM MgCl2 (Mg EGTA) to block classical pathway activation, indicating that antibody mediated the bactericidal reaction through the alternative pathway. Deposition of C3 and C9 and killing of 120 15 in 10% Abs NHS or 10% H gamma S was measured after presensitization with increasing amounts of IgG, F(ab')2, or Fab'. There was a dose-dependent increase in C3 deposition and killing, but only minimal change in C9 binding when 1.0 X 10(3) to 3.2 X 10(4) IgG or F(ab')2/CFU were bound to the bacterial surface. In contrast, there was no increase in C3 or C9 binding and no bacterial killing when 1 X 10(3) to 3.4 X 10(4) molecules Fab'/CFU were bound to the bacterial surface. These experiments show that immune IgG and F(ab')2 can mediate killing of E. Coli 0111B4 by the alternative pathway without changing the extent of terminal C component attachment to the bacterial surface.

Animals↗
PubMed1977

Role of complement in thrombogenesis. I. Complement-dependent coagulation in a model system.

Chondroitin sulphate was used to isolate from plasma a system that clotted with Russell's viper venom, brain extract and activated contact factors. Clotting appeared to depend on concomitant change in C4, C3 and C1s in the system. Brain extract additionally reacted with C9. Reconstitution of specifically defective plasmas suggested a specific role for each of these complement components in clotting.

Antigen-Antibody Reactions↗
PubMed1988

The significance of complement activation in the pathogenesis of hypersensitivity pneumonitis: sequential changes of complement components and chemotactic activities in bronchoalveolar lavage fluids.

Hypersensitivity pneumonitis (HP) is believed to be induced by immunological mechanisms, the details of which remain to be clarified. While a role for cellular immunity is accepted in the pathogenesis of HP, several clinical observations also suggest a role for immune-complex-mediated lung injury. We have previously demonstrated the presence of chemotactic factors for polymorphonuclear cells (PMNs) in bronchoalveolar lavage (BAL) fluids of acutely ill patients with the summer type of HP found in Japan. The present study correlated chemotactic factors for PMNs with the level of C5a des Arg in BAL fluids obtained from patients with summer type HP. Furthermore, this study demonstrated that PMNs were increased in BAL fluids obtained after 2 days of avoidance of exposure to the presumptive causative agent. The percentage of PMNs in the BAL increased in proportion to the activity of the chemotactic factors. Finally, leukotriene B4 was not detected in concentrated BAL or supernatant fluids of cultured macrophages. These results suggest that complement activation in the respiratory tract may occur as the early event in the pathogenesis of HP.

Alveolitis, Extrinsic Allergic↗
PubMed1985

Regulatory proteins for the activated third and fourth components of complement (C3b and C4b) in mice. II. Identification and properties of complement receptor type 1 (CR1).

We identified on the membrane of mouse spleen cells a polypeptide of Mr 190,000 (S190), with binding affinity for the mouse third component of the complement system (C3). S190, purified by affinity chromatography on C3-Sepharose, has properties resembling those of the human C3 receptor type 1 (CR1). Thus, S190, like CR1, served as a cofactor for the C3b inactivator (I)-mediated cleavage of fluid-phase C3b into iC3b, and had cofactor activity comparable to that of serum factor H (H). S190 also acted as a cofactor for the cleavages of membrane-bound C3b or membrane-bound iC3b into C3c (Mr 140,000) and C3dg (Mr 40,000) by serum factor I. As is the case with CR1, the specific activity of S190 for the cleavages leading to C3c-C3dg formation was approximately 100-fold greater than that of H. We therefore conclude that S190 and CR1 are analogous proteins.

Animals↗
PubMed1980

The effect of aging on complement activity (CH50) and complement protein levels.

Total complement activity (CH50), and the protein levels of C1q, C4, C3, C5, C9, factor B and C1 inactivator were measured in the 1,130 sera obtained from healthy subjects aged between 20 and 79 years old. Increase in the levels of CH50, C1q, C4, C3, C5 and C9 and decrease of factor B were found in the older age group. The level of C1 inactivator showed little variation with aging.

Adult↗
PubMed1986

Complement C3b receptors on erythrocytes, circulating immune complexes, and complement C3 split products in patients with primary Sjögren's syndrome.

Twenty-one patients with primary Sjögren's syndrome (SS) and 22 age- and sex-matched healthy controls were examined for levels of C3b receptors (CR1) on erythrocytes (by an enzyme-linked immunosorbent assay), levels of circulating immune complexes (IC) (by a polyethylene glycol precipitation complement consumption method), and C3 split products, C3d and C3c (by intermediate gel rocket immunoelectrophoresis). CR1 varied within a wide range (20-124%), and a preponderance of low numbers was found among patients with primary SS (P less than 0.05). The levels of circulating IC and C3d were elevated in primary SS patients (P less than 0.01) and were mutually correlated (P less than 0.01; tau = 0.5), but levels of circulating IC and C3d did not correlate with CR1 values. C3c concentrations were the same in patients and controls. It is possible that the CR1 level serves as a predictor for the development of IC-induced manifestations, and the C3d concentration serves as an objective parameter for disease activity in primary SS.

Adult↗
PubMed1980

Analysis of the different types of leukocyte membrane complement receptors and their interaction with the complement system.

The specificity, distribution, and structure of 8 different types of leukocytes membrane complement (C) receptors (CR1, CR2, CR3, and receptors for C1q, beta 1H, C3e, C3a, and C5a) are discussed. Recent data are reviewed on the synthesis of C components by macrophages and B lymphocytes, and how these components may function in the activation of these two cell type by the C system. Commonly used C receptor assay procedures are evaluated in terms of both specificity and sensitivity. Specific assay procedures are recommended for measuring CR1 (C4b-C3b receptor), CR2 (C3d receptor), CR3 (C3bi receptor), and the beta 1H receptor. Assays include both rosette and fluorescence procedures for detection of C receptors on either mouse or human leukocytes. Primary systems have been selected for optimal sensitivity and specificity, and where possible, acceptable alternative systems that are less sensitive or specific are suggested for laboratories lacking facilities for C purification.

Animals↗