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PubMedDate not supplied

[Complement].

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Blood Coagulation↗
PubMed1976

Cold activation of complement i. presence of coagulation-related activator.

Determination of the complement titer in the serum and plasm of 120 patients with chronic liver diseases showed that in eight (7%) patients with cirrhosis of the liver, chronic active or chronic inactive hepatitis complement in the serum was less than half in the plasma. The dissociation of complement serum and plasma was due to cold activation of the classical pathway of complement in vitro since serum drawn from these patients at 37 degrees C lost hemolytic activity in 4 hours when transferred to a cold environment. Neither HB antigen nor cryoglobulin participated in this phenomenon. The activation of complement in the cold could be prevented by increasing the ionic strength, or by adding vitamin E or, to a lesser extent its vehicle HCO-60, while heparin, Trasylol, soybean trypsin inhibitor, or hirudin had no effect. Trans-AMCHA prevented activation in one case. It is speculated that a factor appearing as a result of blood clotting is able to activate the classical pathway of complement in the cold; it is probably not related to Hageman factor (factor XII), factor VII, thrombin, kallikrein.

Antithrombins↗
PubMed1977

The activation of the C3b feedback cycle with human complement components. II. Using components of the alternative pathway.

The C3 convertase of the C3b feedback cycle was generated in the fluid phase from C3b and factors B and D. It was shown to be an effective decomplementing agent when reacted with human serum. Many of the effects observed were dependent on the operation of the feedback during the ongoing reaction. Oxidization of factor B with iodine did not significantly increase the potency or the stability of the enzyme. Treatment of C3b with antrypol inhibited the formation of the enzyme. In preliminary experiments in the rat, the convertase was successfully formed in vivo, accompanied by cleavage of C3, consumption of C5, C6 and C7, and a biphasic change in the circulating neutrophils.

Animals↗
PubMed1984

Evidence for restriction of the ability of complement to lyse homologous erythrocytes.

This research explored the possibility that a mechanism for the inhibition of C exists that is capable of restricting lysis of antibody-sensitized homologous E. The ability of C to lyse E from six species was compared by using a passive lysis system that employed E coated with B. abortus LPS and bovine antibodies specific for B. abortus. A system was developed that permitted comparisons of the hemolytic efficiencies of heterologous and homologous C target cell combinations. C from all of the species tested lysed heterologous E effectively, but homologous E were poorly lysed. Furthermore, a serum factor appeared to be involved with restriction of lysis of homologous E:LPS:Ab by heterologous C, and the restriction was specific for homologous E. Human E:LPS:Ab that were washed after incubation with CH were resistant to subsequent lysis by heterologous C. This restriction did not occur at 0 degrees C or in the absence of antibodies. Incubation of homologous C with EH:LPS:Ab resulted in consumption of C1, C2, C3, and C4, but not C5. The treated CH would lyse sheep EAC1423, but it would not lyse sheep EA, EACI, or EAC142. Late reacting C components (C5 through C9) were not detectable on EH:LPS:Ab after incubation with CH, but C4 and C3 were bound to the cells. Rat late-reacting C components (rat C-EDTA) were capable of detecting C3 convertase sites on EH:LPS:Ab that had been reacted with CH. However, homologous late-reacting components and guinea pig late-reacting components were unable to detect the C3 convertase sites.

Animals↗
PubMed1980

[The complement system and its biological activities].

The complement system is a non specific humoral defence mechanism which can be triggered by various effectors : immune-complexes, extrinsic proteases, bacterial cell-wall polysaccharides, viral membranes. Different peptides or multimolecular complexes are formed by a cascade of proteolytic cleavages; they take an active part in the inflammatory response and may contribute to different pathological manifestations.

Adhesiveness↗
PubMed1983

New synthetic inhibitor to the alternative complement pathway.

The inhibitory effects of 6-amidino-2-naphthyl 4-guanidinobenzoate (FUT-175) on the activities of factor B, factor D and cobra venom factor (CVF) X Bb were examined. FUT-175 bound specifically to the Bb fragment of factor B or CVF X Bb. FUT-175 was a non-competitive inhibitor of the esterolysis of L-leucyl-L-alanyl-L-arginine naphthylester by factor B and CVF X Bb. FUT-175 also inhibited the haemolytic activity of factor B, the C3 convertase activity of CVF X Bb and the factor B-cleaving activity of factor D. The concentration of FUT-175 causing 50% inhibition of these activities was 10(-5) - 10(-4)M.

Animals↗
PubMedDate not supplied

[Substances contained in the coelomic fluid of Lumbricus terristris having functions in common with those of some human complement components].

In the present work, it was demonstrated for the first time that the coelomic fluid of Lumbricus terrestris contained a substance recognized by human classical convertase. This substance permitted an immune, complement-dependent agglutination response of sheep erythrocytes carrying C3-convertase (EAC142). In addition, substances secreted by coelomic leukocytes possessed an inhibitory activity against human complement: the component C3 was cleaved into a C3b fragment. This result suggests the presence of a system the function of which is C3-convertase-like. We have thus shown that some complement functions, with their natural inhibitors, appear early in evolution. Certain of these functions and structures might be preserved throughout evolution.

Animals↗
PubMed1984

Characterization of alternative pathway inhibition by a serum derived, low molecular weight complement inhibitor.

Normal human serum contains an inhibitor of complement which is distinguished by its small size of 500 daltons, the low molecular weight inhibitor (LMWI). When LMWI was present during incubation of zymosan or cobra venom factor with serum, formation of complement reactive complexes was blocked as measured by failure of these mixtures to lyse susceptible erythrocytes from patients with paroxysmal nocturnal haemoglobinuria (PNH). Addition of LMWI to pre-formed complexes had no effect on their subsequent haemolytic activity. When dialysis was used to remove LMWI from reaction mixtures, it was shown that LMWI had not irreversibly altered any of the complement components. Purified components were used to demonstrate that LMWI prevented factor D activation of cobra venom factor-factor B complexes. LMWI also strongly inhibited binding of 125I-factor B to human erythrocytes bearing C3b and had little or nor effect on binding of 125I-factor H to the C3b bearing cells. Factor B binding to C3b was equally inhibited on normal and PNH erythrocytes. Thus, a dialysable fraction from normal human serum prevents activation of human complement by blocking formation, but not the activity of the C3/C5 convertase. These low molecular weight inhibitors result in inhibition of factor B binding to C3b and inhibition of factor D activation of C3bB complexes.

Cells, Cultured↗
PubMed1978

Levels of total haemolytic complement activity in paired dairy cow-newborn calf sera.

Total haemolytic complement (CH50) activities of sera obtained from newborn dairy calves and their corresponding dams were compared. The differences between the mean maternal and neonatal CH50 concentrations were significant (P less than or equal 0.001). The concentration of CH50 units/ml in sera from 16 calves was 52.0 +/- 21.4, whereas, for the cows it was 195.8 +/- 24.0. The ratio of cow: calf serum CH50 values averaged 4.24 with a range from 1.77 to 8.00. A positive rank correlation of 0.479 (P less than 0.05) was found between the CH50 titres in calves and their dams. Anticomplementary substances were not detected in calf sera. The possible relationships betweeen deficient CH50 levels in newborn calves and their susceptibility to infectious agents is discussed.

Age Factors↗