PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Complement Inactivator Proteins”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1975

Cyanate as an inactivator of complement proteins.

Sodium cyanate added to normal human serum or serum from patients with sickle-cell disease resulted in the functional inactivation of C3, C5, C6, C7, and the C3b inactivator, but not C8 and C9. Final concentrations as low as 0.5 mM in serum caused inactivation of 12 to 64% of the C3 after 8 hr at 37 degrees C. The activity of the inactivated C3, C5, and C3b inactivator was not restored by dialysis. Most of the functional activity of C3 in cyanate-treated sera was destroyed by very small quantities of 14C-labeled cyanate that was bound to the protein. C3 inactivation by cyanate occurred in heated sera (50 degrees C, 30 min) and sera treated with EDTA, probably indicating that one mechanism for inactivation was by a direct carbamylation reaction. Both C3 and C5 showed two anodal-migrating forms in two dimensional antigen-antibody crossed electrophoresis in some sera treated with low concentrations of cyanate. Measurements of circular dichroism of highly purified carbamylated C3 showed no detectable changes in structure even though most of the functional activity was destroyed. Purified, inactive C3 that was carbamylated with 14C-labeled cyanate was capable of binding to EAC142, but the resulting EAC1423 was weakly positive for immune adherence and negative for agglutination with anti-C3 antiserum. Unlabeled, cell-bound C3b on EAC142 was not susceptible to cyanate action as shown by no loss in immune adherence and positive agglutination with anti-C3 antiserum. The C3b inactivator was more susceptible to cyanate than C3 in a short time period, whereas both were inactivated after 8 hr. Since cyanate is currently being evaluated as a treatment for sickle-cell disease, the inactivation of C3 by the drug is an important consideration for such patients who are already deficient in C3 dependent heat-labile opsonins that aid in host defense.

Anemia, Sickle Cell↗
PubMed1975

[Acquired C1-esterase inhibitor deficiencies during lymphoid syndromes].

Very marked abnormalities of the complement system were discovered in two patients suffering from a lymphoid syndrome and an IgM 7S dysglobulinaemia. The abnormalities in the complement system were related to a deficiency in C1-estérase (C1 INH). Several findings suggest that such a deficiency is acquired, in particular the absence of any family history of angio-neurotic oedema and, above all, the detection of a marked fall in levels of the C1 fraction which does not exist in the congenital form of deficiency of the inhibitor. The IgM 7S immunoglobulins found in the serum of both patients are probably responsible for the abnormalities in the complement system observed. Such acquired deficiencies in C1 INH are extremely rare since only a few cases have been reported in the literaute, in particular two cases in patients with lymphosarcoma with a serum IgM 7S.

Aged↗
PubMed1989

Protein S binding in relation to the subunit composition of human C4b-binding protein.

The human regulatory complement component C4b-binding protein (C4BP) circulates in plasma either as a free protein or in a bimolecular complex with the vitamin K-dependent protein S. The major form of C4BP is composed of 7 identical, disulfide-linked 70 kDa subunits (alpha-chains), the arrangement of which gives the C4BP molecule a spider-like appearance. Recently, we identified a unique 45 kDa subunit (beta-chain) in C4BP. We have now isolated a subpopulation of C4BP, which does not bind protein S. This C4BP species, which had a molecular weight slightly lower than that of the predominant form, was found to lack the beta-chain. Another lower molecular weight form of C4BP was also purified. It contained the beta-chain and was efficient in binding protein S. Its subunit composition was judged to comprise six alpha-chains and one beta-chain. These results indicate C4BP in plasma to be heterogeneous at a molecular level vis-a-vis subunit composition and/or protein S binding ability and provide support for the concept that the beta-chain of C4BP contains the single protein S binding site.

Blotting, Western↗
PubMed1990

C4b-binding protein, a regulatory component of the classical pathway of complement, is an acute-phase protein and is elevated in systemic lupus erythematosus.

A radioimmunoassay using monoclonal and polyclonal antihuman C4b-binding protein (C4BP) antibody was developed to quantitate C4BP in serum. Using the assay, the levels of C4BP in healthy individuals, in patients with systemic lupus erythematosus (SLE), and in acute-phase individuals were determined. The levels of C4BP are significantly elevated in individuals with SLE (186%; p = 0.0001) and are even higher in individuals during the acute phase (286%; p = 0.0001). To confirm whether or not individuals were in the acute-phase response, serum C-reactive protein (CRP) levels were assessed. In the acute-phase response, CRP levels were 100-fold elevated over normals, but did not correlate with increases in C4BP (r = -0.031; p = 0.899). In SLE patients, the CRP levels were significantly, but moderately, elevated (5-fold; p = 0.028). The data indicate that C4BP is an acute-phase reactant and is differentially regulated from CRP during the acute-phase response.

Acute-Phase Proteins↗
PubMed1976

C1 and human platelets. III. Role of C1 subcomponents in platelet aggregation induced by aggregated IgG.

Studies have been performed with platelets using C1 haemolytic assays and platelet aggregation induced by anti-C1q, anti-C1s and aggregated IgG in the presence of C1 subcomponents C1q, C1r and C1s. C1q was removed by EDTA or modified by collagenase from human platelets while after the same treatment C1s remained bound to the platelets. EDTA treated platelets were no longer aggregated by aggregated IgG. The addition of C1q restored the reactivity of the platelets to aggregated IgG while the addition of C1r or C1s was without effect. Furthermore, the addition of C1r or C1s to C1q inhibited the action of C1q in platelet aggregation induced by IgG.The possible association between the different C1 subcomponents and human platelets is discussed.

Complement C1↗
PubMed1987

Ixodes dammini: salivary anti-complement activity.

Saliva of the tick Ixodes dammini prevents hemolysis of rabbit erythrocytes by the human alternative pathway of complement. Deposition of C3b to activating surfaces and concomitant C3a release are inhibited. C3b deposition to activating surfaces is inhibited regardless the origin (humans, rat, mouse, guinea pig, and hamster) of the serum. The inhibitor elutes as a single peak upon gel filtration, with an apparent molecular weight of 49,000. Salivary anti-complement may contribute to successful feeding of I. dammini in their natural hosts.

Animals↗
PubMed1976

C1 inactivator.

Explore the source record for details and available documents.

Amino Acids↗
PubMed1986

Lipopolysaccharides as complement inhibitors by complex formation with the purified third complement component (C3).

Lipopolysaccharides (LPS) from different bacteria in smooth or rough form (Y. enterocolitica, Y. pseudotuberculosis, E. coli, S. typhimurium, S. marcescens) strongly inhibited hemolytic C3 in incubation mixtures with purified C3. LPS from a core deficient mutant was still reactive, whereas lipid A no longer affected C3 activity. The physical state of LPS was critical for its effect on C3. Strand-like LPS structures formed by Ca++-induced aggregation of solubilized LPS, as shown by electron microscopy, demonstrated the highest reactivity with C3. Inhibition of hemolytic C3 was found to be due to complex formation between LPS and C3 by a hydrophobic reaction. The binding capacity of 1 microgram LPS-R and LPS-S was as high as 125 ng C3 and 56 ng C3, respectively. The C3b fragment required different reaction conditions for maximal binding. The strong binding capacity of LPS for the complement component C3 raises the possibility that LPS act as inhibitors of complement by interruption of the reaction cascade at local infectious sites with gram-negative bacteria.

Centrifugation, Density Gradient↗
PubMed1976

Irreversible enzyme inhibitors. Inhibitors of guinea pig complement derived by quaternization of substituted pyridines with benzyl halides.

A series of 83 compounds derived from hydrocarbon-substituted pyridines by quaternization with PhCH2Br usually containing a 2-SO2F or 6-Cl-2-SO2F group was synthesized and evaluated as inhibitors of guinea pig complement and in most cases its C1 component. The most active compounds were 3-(4-phenylphenylbutyl)-N-(6-choro-2-fluorosulfonylbenzyl) pyridinium bromide (43) and 3-(4-phenylphenylbutyl)-N-(2-fluorosulfonylbenzyl) pyridinium bromide (44), each showing 50% inhibition at 7.8 muM. The most effective irreversible inhibitor of the C1 component was N-(6-chloro-2-fluorosulfonylbenzyl)-5,6-benzoquinolinium bromide (87), which showed 50% inhibition at 4 muM.

Animals↗