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PubMed1978

Testing of hemolytic complement components in domestic animals.

Total complement (C) and its components were assayed in the serum of 8 species of domestic animals, using commercially prepared cellular intermediates of sheep erythrocytes and functionally pure guinea pig and human components of the C system. Testing was done according to methods recommended by the producer for testing human C components. The late-acting components (C6 throug C9) and C1 were detected in carnivorous (dog and cat) and omnivorous (swine) animals. Undetectable or low titers of C4, C2, C3, and C5 were present in large herbivorous animals (cattle, horse, sheep, and goat), indicating major differences in comparison with human or guinea pig components of C. Porcine serum contained an inhibiting substance which interfered with testing C2 and later-acting components at serum dilutions up to 1:100. All components except C2 were detected in chicken serum. The binding or activation (or both) of C4, C2, C3, and C5 is more species specific than is the binding or activation (or both) of other components. Requirements for species specificity between antibody and C1 were not detected. Presence of C1 inactivator was detected in bovine, caprine, equine, and ovine sera. The CH50 (50% hemolysis) titers of C components tested in pooled serum samples from the 8 species of clinically healthy domestic animals are presented.

Animals↗
PubMed1978

The structural events associated with the attachment of complement components to cell membranes in reactive lysis.

Electron microscopic study of the events occurring at the cell membrane during reactive lysis by complement, showed that a foliaceous particle was formed at the C5b-7 stage, that enlarged to a particle with a variable number of arms at the C5b-8 stage. Up to this point, no typical complement lesions were found. At the C5b-9 stages, the particles were completely converted to typical complement lesions, i.e. hollow cylinders projecting from the cell membrane and partly penetrating it. C5b-9 complexes assembled in the fluid phase did not show the typical structure of the lesions, but were amorphous masses of fibres.

Complement C5↗
PubMed1976

Deviated lysis: Transfer of complement lytic activity to unsensitized cells II. Generation of the activity by inulin and by antigen antibody complexes.

Deviated lysis (d.l.) activity, i.e. lysis of unsensitized cells by lytic C activity, was generated via the classical pathway of Cactivation (ag ab complexes) and via the alternative pathway (inulin). The activity was observed on the surface of the activating particles and in the fluid phase. The activity was relatively stable at 32 degrees C. Its generation involved the C components C6 through C9 and possibly also C5.

Animals↗
PubMed1977

Deviated lysis: transfer of complement lytic activity to unsensitized cells. IV. Parital isolation of the activity.

Deviated lysis (d.l.) was previously characterized as the lysis of non-sensitized erythrocytes by activated complement (C) in the presence of EDTA (1, 2, 3). The lytic activity was present in serum fractions of a m.w. in the proximity of 220,000. All the C factors C5 through C9 were found in these fractions and they were all needed for lysis. It is proposed that in d.l. small aggregates of the C components C5 through C9 coexist in the reaction mixture without further interaction. Only when appropriate receptors such as present on target cells surfaces are available, the factors react in a sequential order eventually to result in lysis of the target cell.

Animals↗
PubMed1977

Complement system in human colostrum: presence of nine complement components and factors of alternative pathway in human colostrum.

Evidence has been obtained for the presence in human colostrum of all nine components of complement (C), C1 through C9, and factors of the alternative pathway. Samples of colostrums collected from five women at 1-4 days after normal parturition were assayed for the haemolytic activities of individual components. As compared with normal human sera, the activities of each component ranged from 0.03 to 7% of those in sera. The activities of C4, C7 and C9 were relatively high, while that of C1 was extremely low. In most of the cases, the activities of individual components gradually increased following delivery, when expressed as the activity per unit weight (g) of protein in the colostrum. When the colostrums were treated with cobra venom factor, most of the colostrums showed 10-20% reduction in the C3 activity. This finding indicates the presence of factors such as B and D which are involved in the activation of C through the alternative pathway. The role as a defense factor of the C system in human colostrum and milk is discussed in connection with the ability of secretory IgA to react with C.

Colostrum↗
PubMed1988

The heparin binding domain of S-protein/vitronectin binds to complement components C7, C8, and C9 and perforin from cytolytic T-cells and inhibits their lytic activities.

S-Protein/vitronectin is a serum glycoprotein that inhibits the lytic activity of the membrane attack complex of complement, i.e., of the complex including the proteins C5b, C6, C7, C8, and C9n. We show that intact S-protein/vitronectin or its cyanogen bromide generated fragments also inhibit the hemolysis mediated by perforin from cytotoxic T-cells at 45 and 11 microM, respectively. The glycosaminoglycan binding site of S-protein/vitronectin is responsible for the inhibition, since a synthetic peptide corresponding to a part of this highly basic domain (amino acid residues 348-360) inhibits complement- as well as perforin-mediated cytolysis. In the case of C9, the synthetic peptide binds to the acidic residues occurring in its N-terminal cysteine-rich domain (residues 101-111). Antibodies raised against this particular segment react 25-fold better with the polymerized form of C9 as compared with its monomeric form, indicating that this site becomes exposed only upon the hydrophilic-amphiphilic transition of C9. Since the cysteine-rich domain of C9 has been shown to be highly conserved in C6, C7, and C8 as well as in perforin, the inhibition of the lytic activities of these molecules by S-protein/vitronectin or by peptides corresponding to its heparin binding site may be explained by a similar mechanism.

Animals↗
PubMed1990

Identification of the heterozygotes for deficiency of the beta-subunit of the eighth component of complement by reduced levels of C8 beta and increased amounts of free C8 alpha-gamma.

Sera from obligate heterozygotes for deficiency of the C8 beta subunit of the eighth component of human complement (C8) were analyzed for the molecular composition of C8. The C8 alpha-gamma and C8 beta subunits were separated by SDS-PAGE, visualized by immunoblotting, and the resulting bands were quantitated by laser densitometry. The laser densitometric absorption data were set to 100 arbitrary units (AU) for both subunits of pooled normal human sera. The AU values of individual normal sera ranged from 45 to 150 AU for C8 alpha-gamma (median 99 AU) and from 45 to 140 AU for C8 beta (median 101), whereas the C8 alpha-gamma/C8 beta-ratio varied from 0.7 to 1.4. Sera from C8 beta-deficient heterozygotes differed, as expected, from the normal sera for the markedly reduced levels of C8 beta (20 to 90 AU, median 55 AU) and for the higher C8 alpha-gamma/C8 beta-ratio (1.3 to 3.5). High voltage agarose gel electrophoresis was used to separate free and C8 beta-bound C8 alpha-gamma. The migration of free and C8 beta-bound C8 alpha-gamma subunit was checked by hemolytic overlay gels and by second dimension SDS-PAGE and immunoblotting. Immunochemical evaluation of C8 alpha-gamma using this system revealed about 5-14% free C8 alpha-gamma in sera with normal C8 and higher levels, from 33-71%, in the C8 beta D heterozygous sera. Functional analysis confirmed the substantial increase of free C8 alpha-gamma in the heterozygous group. We conclude that the C8 in C8 beta D heterozygous sera is characterized by increased amounts of free C8 alpha-gamma due to reduced concentrations of the C8 beta subunit. This finding may help to identify individuals heterozygous for C8 beta deficiency.

Complement C8↗
PubMed1992

Enhanced expression of the complement-regulatory factor C8 binding protein (C8bp) on U937 cells after stimulation with IL-1 beta, endotoxin, IFN-gamma, or phorbol ester.

C8 binding protein (C8bp) is a 65-kDa membrane glycoprotein that inhibits complement-mediated lysis by homologous C5b-9. C8bp was first identified on human erythrocytes, but could also be detected on peripheral blood cells, platelets, glomerular cells and synovial fibroblasts. Lack of C8bp as seen in patients with paroxysmal nocturnal hemoglobinuria type III results in enhanced susceptibility of the cells toward C5b-9. We studied C8bp expression on the promonocytic cell line U937. In addition to the membrane-bound C8bp, a cytoplasmic form of C8bp could also be identified by immunofluorescence, blotting, and precipitation. Stimulation of the cells with IL-1 beta, endotoxin, IFN-gamma, or phorbol ester increased C8bp surface expression. Because cycloheximide did not inhibit enhanced surface expression, it was most probably mobilized from cytoplasmic reservoirs. Thus, resistance of nuclear cells to complement attack seems to be based on two events: 1) the removal of the C5b-9 complex from the membrane; and 2) expression of regulatory surface proteins such as C8bp, which inhibit C5b-9-mediated lysis. We propose that the C8bp mobilization by cytokines might provide an additional protection against complement attack by its known interference with the C5b-9 assembly.

Blood Proteins↗
PubMed1992

Genetic polymorphism of complement component C6, C7 and C8(1) in Chinese Han population in northeast China.

Distributions of complement phenotypes, C6, C7, and C8(1) were studied using thin agarose gel isoelectric focusing (AGIEF) or ultra-thin polyacrylamide gel isoelectric focusing (PAGIEF) and subsequent immunoblotting techniques in 203 Chinese Han population in Liaoning Province of northeast China. The gene frequencies were as follows: C6*A 0.4704, C6*B 0.5049, C6*B2 0.0148, C6*B3 0.0049, and C6*M 0.0049; C7*1 0.8251, C7*2 0.1108, C7*3 0.0320, and C7*4 0.0320; C8(1)*A 0.5567 and C8(1)B 0.4433, respectively. All the observed numbers of the phenotypes were in agreement with the expected numbers under the Hardy-Weinberg equilibrium. The gene frequencies among Chinese subpopulations and other various populations were compared.

Asian People↗
PubMed1989

Inhibition of immune haemolysis by a serum factor found in C3-deficient subjects.

A serum factor, which inhibits haemolysis of the buffer control used in a C3 haemolytic assay, was found in a C3-deficient subject (C3D). Since the buffer control consisted of EAC142, C5 and C6-9 reagent (C6-9R, prepared by treatment of guinea-pig serum with KSCN and hydrazine hydrate), the factor seems to be an inhibitor of C3-independent immune haemolysis. Gel filtration and CM cellulose column chromatography of C3D serum suggested that the inhibitor may be C8. The inhibition was not observed in C8-depleted C3D serum. Furthermore, isolated C8 was found to inhibit haemolysis of EAC142 by C5 and C6-9R in a dose-dependent fashion. Thus, C8 was found to be an inhibitor of C3-independent immune haemolysis in the assay. Further studies revealed that C8 also inhibits haemolysis of EAC142 by C3, C5 and C6-9R (C3 assay system) or that of EAC1423 by C5 and C6-9R (C5 assay system), indicating that C3 or C5 haemolytic activity can be underestimated by the presence of C8 in a sample. C8 did not inhibit haemolysis in the assay system when isolated C6-C9 of human origin were used, but did inhibit haemolysis when isolated C6-C9 of guinea-pig origin was used instead of C6-9R. Thus, it was suggested that the incompatibility of human C8 with guinea-pig C6-C9 might be responsible for this phenomenon. Additional experiments for the mechanism clearly showed that human C8 inhibits the haemolysis of EAC1-7 (EA bearing human C1-C5 and guinea-pig C6 and C7) by guinea-pig C8 and C9 by binding to EAC1-7 prior to guinea-pig C8.

Animals↗
PubMed1990

Purification of C8 and C9 from rat serum.

A procedure based on modifications of published methods for human proteins for the isolation of rat C8 and C9 from one batch of serum is described. The procedure allows the rapid, large-scale isolation of pure and haemolytically active proteins. Rat C9 had a slightly higher molecular weight than human C9 on SDS-PAGE and similar isoelectric point. Rat C8 differed from human C8 in the molecular weight of the gamma chain (23,000 and 21,000 kD respectively), and on isoelectric focusing (pI rat C8: 6.5-6.9; pI human C8: 7.4-7.9).

Animals↗