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PubMed1975

Complement activation by interaction of polyanions and polycations. I. Heparin-protamine induced consumption of complement.

Interactions of heparin and protamine in fresh human serum, in amounts far below those required for complement depletion by either agent alone, were found to induce virtually complete depletion of total hemolytic complement activity. This depletion was dependent on time, temperature, pH, divalent cations, and serum concentration. The predominant complement component hemolytic activity depleted was C1; under appropriate reaction conditions C4 and C2 were depleted as well. Equivalent amounts of heparin along induced lesser but substantial depletion of C3-9, whereas equivalent amounts of protamine had no effect upon complement component activities. We conclude that interaction of heparin with protamine, like interaction of antibody with antigen, markedly enhances its ability to interact with the first component of complement and activate the classical complement pathway. It is suggested that complement activation by interactions between certain polyanions and polycations, like interactions between antigens and antibodies, may have a role in the initiation of inflammatory reactions.

Adult↗

PubMed1978

Inhibition of human complement components by Loxosceles reclusa venom.

Venom from the brown recluse spider, Loxosceles reclusa, was capable of inactivation human C1-C7 in vitro. This inactivation occurred if venom was added to fresh adult human serum, human cord serum, or functionally pure specific human components. Optimal incubation conditions for the inactivation of each component were determined and were found generally to be in the range of 25 or 37 degrees C for 30-60 min. The alternative complement pathway did not appear to be involved, since C1, C4, and C2 were readily inactivated, and inactivation took place in sera depleted of factor B of the properdin system. Venom-induced inactivation appeared to require few, if any, serum cofactors, because, with the possible exception of C2, functionally pure components, as well as those in sera, were readily inactivated.

Animals↗

PubMedDate not supplied

Systemic lupus erythematosus in a patient with C4 deficiency.

A 40-year-old female with systemic lupus erythematosus was found to be totally deficient in the 4th component of complement and to be lacking in Chido and Rodgers blood group substances on red cells and in plasma. Family studies were suggestive of a linkage of the C4 deficiency with an HLA haplotype. C2 in the patient's serum was 50% of normal but other complement components and alternative pathway functions were normal. Chemotactic and opsonic activities in the patient's serum were diminished.

Adult↗

PubMed1983

Effects of penicillinase on bactericidal and complement activities in normal human serum.

During routine addition of penicillinase (beta-lactamase) to patients sera, we found that the capacity of some of these sera to kill serum-sensitive gram-negative organisms was significantly decreased. Further controlled studies showed that penicillinase decreased both the bactericidal activity of normal human sera and the total hemolytic activity (CH50) of complement in these sera. The decreased bactericidal activity correlated significantly (r = 0.57, P less than 0.05) with the reduction of CH50 in eight normal sera. These effects of penicillinase were time and temperature dependent. Measurement of individual complement component activities showed that penicillinase decreased the activity of C2, C4, and C3-C9, suggesting that the penicillinase preparation activated the classical pathway. These results cast doubts on the validity of bactericidal determinations when sera are pretreated with penicillinase.

Bacteria↗

PubMedDate not supplied

Serine proteases as mediators of radiographic contrast media toxicity.

Iodipamide, iodoxamine, iothalamate, diatrizoate, and ioxitalamate exhibit a dose-dependent prolongation of coagulation time of global and monospecific functional coagulation tests. This is due to an inhibition of fibrin polymerization induced by these contrast media. Furthermore, a dose-dependent generation of fibrinolytic split products by RCM was found. At low doses, biliary RCM cause hypercoagulation by binding to spontaneously existing fibrinolytic products. Biliary RCM cause a dose-dependent decrease of hemolytic complement activity and decrease of complement factors of C3, B, and, to a lesser extent, C4. Nephrotopic RCM do not show these effects. By crossed immunoelectrophoresis B and C3 split products were not detected after in vitro incubation of iodipamide in serum or EDTA-blood. In contrast, zymosan, inulin, and dextran sulfate incubation of sera readily resulted in Bb and C3b generation. The failure to demonstrate complement split products was not due to artifacts. As a working hypothesis unspecific binding of RCM to blood proteins followed by interference with antithrombin and antiplasmin inhibitor functions is proposed. Possibly other antiproteases might be involved too. This results in a lowering of the clinical manifestation threshold of coagulation and fibrinolysis. The mechanism of complement activation remains unclear, since it is not influenced by EDTA, aprotinin, steroids, or by specific sera depleted of prekallikrein, Hageman factor, C2, and gamma-globulins.

Animals↗

PubMed1981

Shunt nephritis. Role of the complement system in its pathogenesis and management.

Three cases of shunt nephritis in which serial complement levels were obtained during the course of treatment are presented to illustrate the value of monitoring complement levels in the management of this condition. In shunt nephritis, circulating immune complexes are formed which contain antigen from bacteria of low virulence. These complexes, which activate the classical complement pathway, are reflected in most cases by lowering of the serum levels of C1, C2, C4, and C3. These levels promptly return to normal after the initiation of effective therapy. Serial determinations of serum levels of complement protein provide a sensitive and reliable method for early determination of efficacy of therapy in shunt nephritis.

Anti-Bacterial Agents↗

PubMed1991

[Insulin-dependent complement activity in the serum of patients with diabetes mellitus].

Complement system was comparatively evaluated in 68 patients with diabetes mellitus and 104 healthy subjects. Hemolytic activity was examined for components C1, C2, C3, C4 and C5, and overall activity of the classic pathways was defined. The complement status appeared different for men and women. Females demonstrated hypofunction of the majority of the complement components, subcompensation in the absence of angiopathies, in decompensation complicated by angiopathies the activity was enhanced. In uneventful course of diabetes mellitus in males component C4 was activated remaining above normal though reduced in decompensation with angiopathies. High complement level in females could serve an aggravating factor, it depends on the dose of exogenic insulin.

Adolescent↗

PubMed1975

Immunological properties of glycolipids from membranes of Acholeplasma laidlawii.

Glycolipids, the predominant class of lipids in the membranes of Acholeplasma laidlawii, are the haptenic determinants that react with anti-A. Laidlawii serum to fix complement. The predominant complement-fixing activity of the membrane glycolipids was associated with the monoglucoysyl diglyceride, diglucosyl diglyceride, glycerlphosphoryl diglucosyl diglyceride (GPDD), and an unknown lipid B, which did not react with ninhydrin but release glucose and glycerol and traces of phosphorus upon hydrolysis. The glycolipids monoglucosyl diglyceride and diglucosyl diglyceride or GPDD and unknown lipid B were paired as a result of their cross-reactions with selective antisera prepared with the aid of reconstituted membrane complexes containing membrane lipids. Reconstituted membrane complexes assembled from [14C]monoglucosyl diglyceride and delipidated membrane proteins gave optimal complement fixation titers before saturation of the complexes with the ]14C]monoglucosyl diglyceride. The phosphoglycolipid of the membrane, GPDD, was anticomplementary as a pure lipid, a cholesterol liposome, and a reconstituted membrane complex. This anticomplementary activity, which was caused by 3 mug of pure GPDD, affected both human and guinea pig complement. Although human C1, C4, C3, and C5 were not inhibited by GPDD, C2 was inhibited 10-fold by reconstituted membrane complexes containing 150 mug of GPDD. A role for this phosphoglycolipid is discussed in the hypothetical mechanism of inhibition of C2 attachment to SAC1, 4 sites.

Acholeplasma laidlawii↗

PubMed1986

Interaction of purified lipoteichoic acid with the classical complement pathway.

Glycerophosphate-containing lipoteichoic acids (LTAs) interact with the first component of the classical complement pathway (C1). This resulted in the activation of the classical complement pathway in serum, shown by the consumption of C1, C2, and C4. The dose-dependent interaction of LTAs with purified C1 and C1q was dependent on the negative charges of the phosphate groups of LTA. It was reduced by charge compensation through D-alanine ester substituents and by sterical hindrance through di- and trihexosyl residues linked to position 2 of the glycerol moieties. The charge density of LTA may also play a role: poly(digalactosylglycerophosphate) LTAs, in which the phosphate groups are in a greater distance from each other, were less effective, and the loss of micellar organization by deacylation of LTA drastically reduced the complement activation capacity.

Complement Activating Enzymes↗

PubMed1984

Effect of different penicillin derivatives on complement components in human serum.

The effect of different penicillin derivatives on the human complement system has been studied in vitro. Four penicillins tested (benzylpenicillin, oxacillin, methicillin, azlocillin) were found to inactivate total hemolytic complement dose dependently. This effect is caused by direct inactivation of C2, C5 and one or more of the components C6-9 as well as by activation of the alternative pathway. At relatively high concentrations, penicillins induce a conformational change in C3 and C4, leading to the C3b-like or C4b-like forms of these molecules, respectively. Prominent effects on the complement system occur at penicillin concentrations exceeding those achieved in plasma under regular therapeutic use. However, a synergism of penicillins with drugs acting similarly on the complement system, such as iodinated radiographic contrast media, may be expected.

Azlocillin↗

PubMedDate not supplied

Resin-capture and release strategy toward combinatorial libraries of 2,6,9-substituted purines.

A resin-capture and release strategy for making combinatorial 2,6,9-trisubstituted purine libraries is demonstrated by capturing N9-derivatized purines at the C6 position with a thio-modified polymer. The C2 fluoro group is subsequently substituted with primary and secondary amines followed by thioether oxidation and release by C6 substitution with amines and anilines. This approach complements a previously reported strategy where a 6-phenylsulfenylpurine scaffold was captured at the C2 position with a resin-bound amine.(3)

Combinatorial Chemistry Techniques↗

PubMed2000

[Complement activation in heparin--plasma inhibitory effect of anticoagulants on serum complement activation, 2nd report].

Our previous study of the inhibitory effect of EDTA and citrate in plasma on complement activation revealed that complement is activated in usual citrate plasma but not in usual EDTA plasma. The present study is a similar one using other anticoagulants containing heparin. CH50 and activities of C4 and C2 were assayed in serum or plasma containing various concentrations of anticoagulant after incubation with latex particles bearing immunoglobulin(Ig-Latex). It was found that complement activation is inhibited by heparin in a dose-dependent manner and that 10 U/ml of heparin does not inhibit CH50 reduction and C2 inactivation but inhibit C4 inactivation partially, indicating that complement activation proceeds in plasma containing usual concentration of heparin. Similar results were obtained in cases of low molecular weight heparin(LMWH) and nafamostat mesilate(Futhan). Complement activation was not inhibited by gabexate mesilate(FOY) in the tested range of concentrations. Thus, it was revealed that complement activation is not inhibited by usual concentrations of heparin, LMWH, Futhan and FOY.

Adult↗

PubMed1992

Expression of transcripts of complement components and their receptors during differentiation of embryonal carcinoma cell lines.

Based on our previous finding that TNF-alpha and TNF-beta can be expressed constitutively during early embryonal development [1], we extended our work to identify factors which are generally known to take part in inducing inflammation in adults. They can be regarded as candidate molecules involved in ontogenic inflammation during embryonal development. In this study, we chose the factors which are constituents of either a classical or an alternative pathway of a complement system and found that mRNAs corresponding to those of C2, C3, C4, C5 and to those of receptors CR1 and CR2 were expressed. Among them, mRNA expression of C3, C4, and CR1 was especially constitutive. Contrary to these observations, expression of two kinds of scavenger receptors (SR-I, SR-II) proved to be negative. In this report, the framework of ontogenic inflammation as a regulatory mechanism in embryonal development at the molecular level is discussed.

Animals↗

PubMed2004

Complement determinations in human disease.

OBJECTIVE: To define techniques used for complement measurements and examine the clinical relevance of alterations of complement determinations in disease. DATA SOURCES: Data have been assembled from the authors' research, original articles, and reviews, as well as chapters and complete books on complement. STUDY SELECTION: Studies were chosen for inclusion by the opinions of the authors, relevant complement reviews, publications, and books. RESULTS: Complement has been shown to possess approximately 31 proteins, some of which are enzymes (C1r, C1s, C2, factor B, factor D), some cofactors, some inhibitors or inactivators, and others composed of membrane-integrated proteins. All of the complement proteins have been purified, and many of the respective genes have been identified. The complement cascade is a dual-edged sword, causing protection against bacterial and viral invasion by promoting phagocytosis and inflammation. Pathologically, complement can cause substantial damage to blood vessels (vasculitis), kidney basement membrane and attached endothelial and epithelial cells (nephritis), joint synovium (arthritis), and erythrocytes (hemolysis) if it is not adequately controlled. CONCLUSIONS: Definitive evidence is available that complement-mediated tissue destruction occurs after immune complex injury in the kidney and lung and may be important in lupus erythematosus and adult respiratory distress syndrome. Future studies on complement receptor structure and function may provide clues to treat effectively lupus, hemolytic anemias, and nephritis. In addition, gene therapy and antibody therapy need further refinement to treat immunodeficiency diseases.

Complement System Proteins↗

PubMed1986

Discrete catalytic sites for quinone in the ubiquinol-cytochrome c2 oxidoreductase of Rhodopseudomonas capsulata. Evidence from a mutant defective in ubiquinol oxidation.

A non-photosynthetic mutant (Ps-) of Rhodopseudomonas capsulata, designated R126, was analyzed for a defect in the cyclic electron transfer system. Compared to a Ps+ strain MR126, the mutant was shown to have a full complement of electron transfer components (reaction centers, ubiquinone-10, cytochromes b, c1, and c2, the Rieske 2-iron, 2-sulfur (Rieske FeS) center, and the antimycin-sensitive semiquinone). Functionally, mutant R126 failed to catalyze complete cytochrome c1 + c2 re-reduction or cytochrome b reduction following a short (10 microseconds) flash of actinic light. Evidence (from flash-induced carotenoid band shift) was characteristic of inhibition of electron transfer proximal to cytochrome c1 of the ubiquinol-cytochrome c2 oxidoreductase. Three lines of evidence indicate that the lesion of R126 disrupts electron transfer from quinol to Rieske FeS: 1) the degree of cytochrome c1 + c2 re-reduction following a flash is indicative of electron transfer from Rieske FeS to cytochrome c1 + c2 without redox equilibration with an additional electron from a quinol; 2) inhibitors that act at the Qz site and raise the Rieske FeS midpoint redox potential (Em), namely 5-undecyl-6-hydroxy-4,7-dioxobenzothiazole or 3-alkyl-2-hydroxy-1,4-napthoquinone, have no effect on cytochrome c1 + c2 oxidation in R126; 3) the Rieske FeS center, although it exhibits normal redox behavior, is unable to report the redox state of the quinone pool, as metered by its EPR line shape properties. Flash-induced proton binding in R126 is indicative of normal functional primary (QA) and secondary (QB) electron acceptor activity of the photosynthetic reaction center. The Qc functional site of cytochrome bc1 is intact in R126 as measured by the existence of antimycin-sensitive, flash-induced cytochrome b reduction.

Antimycin A↗

PubMed1978

Dichotomy between opsonization and serum complement activation by encapsulated staphylococci.

Previous studies have demonstrated that encapsulated Staphylococcus aureus strains are not effectively opsonized by the serum complement system. Encapsulated staphylococci thereby "resist phagocytosis." To test whether this phenomenon might be explained by an inability of encapsulated strains to activate complement, the relationship between staphylococcal opsonization and serum complement activation was studied. Although encapsulation was found to interfere with opsonization by pooled human serum (human polymorphonuclear leukocytes phagocytized significantly fewer encapsulated bacteria than unencapsulated bacteria after incubation in this opsonic source), encapsulated (S. aureus M and Smith diffuse) and unencapsulated (S. aureus M variant and Smith compact) strains had similar capacities for complement activation as measured by C3-C9 consumption. When C2-deficient and immunoglobulin-deficient sera were studied, again C3-C9 consumption was not influenced by the presence or absence of a capsule. In addition, C3 was detected on the surface of both S. aureus M and M variant strains after incubation in pooled serum and staining with fluorescein-conjugated anti-C3 antibody. Thus, encapsulated staphylococci are not effectively opsonized even though complement is activated and C3 is present on the bacterial surface. The exact mechanism by which the capsule interferes with opsonization is still not known; however, inhibition of complement activation appears not to be the explanation of this phenomenon.

Antibodies↗

PubMed2026

Complement expression profiles in human glomerular mesangial cells, endothelial cells, podocytes and proximal tubular epithelial cells.

BACKGROUND: Local expression of complement components in the kidney has been reported sporadically in both diseased and normal kidneys. This study aimed to comprehensively characterize the expression of complement components in human glomerular mesangial cells (GMCs), glomerular endothelial cells (GECs), podocytes, and proximal tubular epithelial cells (PTECs) in non-diseased renal tissue. METHODS: Complement expression in cultured human renal intrinsic cells was initially evaluated using reverse transcription polymerase chain reaction and immunofluorescence staining. These findings were further examined using publicly available single-cell RNA-sequencing datasets and 10×Genomics single-cell RNA sequencing of non-diseased human kidney tissue. The analyses focused on complement components involved in the initiation of the classical, lectin, and alternative pathways, as well as components shared among these activation pathways, terminal pathway components, complement regulators, and complement receptors. RESULTS: Complement components unique to the initial phase for classical pathway (C1S, C1R, C2, C4), lectin pathway (MBL2, FCN1, MASP1), alternative pathway (CFB, CFD), and the C3 component shared by the three activation pathways were detected in these cells. The components shared by the terminal pathways including C5, C6, C7, C8 and C9 exhibited lower expression, while complement regulators (CFH, CFI, CD55/DAF, CD46/MCP, CD59, C4BPB, PROS1/Protein S) or receptors (CD93/C1QR1, CR1), particularly membrane-bound proteins, such as DAF, MCP and CD59, which inhibit complement activation and the formation of the membrane attack complex, showed relatively high expression. CONCLUSION: These results showed that all four types of intrinsic renal cells expressed multiple complement components associated with the classical, lectin, and alternative pathways. In non-diseased kidney tissue, complement regulatory molecules involved in the control of complement activation showed relatively higher expression, whereas components of the terminal complement pathway were expressed at relatively lower levels, suggesting that renal intrinsic cells maintain a locally poised but tightly regulated complement system.

Humans↗

PubMed1977

Hemodialysis leukopenia. Pulmonary vascular leukostasis resulting from complement activation by dialyzer cellophane membranes.

Acute leukopenia occurs in all patients during the first hour of hemodialysis with cellophanemembrane equipment. This transient cytopenia specifically involves granulocytes and monocytes, cells which share plasma membrane reactivity towards activated complement components. The present studies document that complement is activated during exposure of plasma to dialyzer cellophane, and that upon reinfusion of this plasma into the venous circulation, granulocyte and monocyte entrapment in the pulmonary vasculature is induced. During early dialysis, conversion of both C3 and factor B can be demonstrated in plasma as it leaves the dialyzer. Moreover, simple incubation of human plasma with dialyzer cellophane causes conversion of C3 and factor B, accompanied by depletion of total hemolytic complement and C3 but sparing of hemolytic C1. Reinfusion of autologous, cellophane-incubated plasma into rabbits produces selective granulocytopenia and monocytopenia identical to that seen in dialyzed patients. Lungs from such animals reveal striking pulmonary vessel engorgement with granulocytes. The activated complement component(s) responsible for leukostasis has an approximate molecular weight of 7,000-20,000 daltons. Since it is generated in C2-deficient plasma and is associated with factor B conversion, it is suggested that activation of complement by dialysis is predominantly through the altermative pathway.

Adult↗