Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Complement C8”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 145 records · Page 8Linked to original sources
PubMed1986

Synthesis of complement components C5, C6, C7, C8 and C9 in vitro by human monocytes and assembly of the terminal complement complex.

Monocytes cultured under serum-free conditions secreted protein which bound covalently and non-covalently to agarose beads, an activator of the alternative pathway of complement. There was a significantly binding of monoclonal anti-C3c antibodies, polyclonal anti-C5, anti-C6, anti-C7, anti-C8, and anti-C9 antibodies, and of a monoclonal antibody against a neoantigen of polymerized C9 to agarose beads incubated with the monocytes for 24, 48, 72 or 96 h. From these results, we conclude that monocytes produce C5, C6, C7, C8 and C9 that assemble as the terminal complement complex on the surface of the agarose beads. Activation by agarose of the alternative pathway with generation of particle bound C3 and C5 convertases is a prerequisite for the subsequent formation of the terminal complement complex. Whether SC5b-9 or the membrane attack of complement (C5b-9) is formed on the beads will be examined.

Antibodies, Monoclonal↗
PubMed1987

[Recurrent meningitis in familial deficiency of the 8th component of the complement system].

An 18-year-old man suffered from recurrent bacterial meningitis. Investigation of the complement system revealed deficiency of the 8th complement component (C8) in the patient and his sister. Genetic defects of the terminal complement components C5 to C8 predispose to Neisseria infections, probably due to a lack in bacteriolytic activity. It is to be noted that 1 year ago the patient had been hospitalized for a culture-proved pneumococcal meningitis.

Adolescent↗
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↗
PubMed1991

Human umbilical vein endothelial cells synthesize functional C3, C5, C6, C8 and C9 in vitro.

Human endothelial cells (EC), cultured serum-free, synthesize de novo protein which increasingly bind to agarose beads (an alternative pathway activator), until a plateau phase is reached after 24-48 h. EC synthesize functional C3, C5, C6, C8 and C9, which were detected on co-cultured agarose beads, using relevant polyclonal anti-complement antibodies. Two monoclonal anti-C9 neoepitope antibodies (aE11, poly C9-MA) bound to the co-cultured beads, showing that the terminal complement complex (TCC) (C5b-9) was assembled on the beads. This also suggests that C7 is synthesized. There seems to be a positive correlation between the amount of agarose-bound labelled protein and agarose-bound complement. The results indicate that EC produce and secrete the components for the functional alternative and terminal pathways of complement.

Antibodies, Monoclonal↗
PubMed1989

Deficiency of the eighth component of complement. Evidence for linkage of C8 alpha-gamma pattern with C8 beta deficiency in sera of twelve patients.

The C8 alpha-gamma subunit of the eighth component of complement was analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting in sera from 68 normal individuals, 12 C8 beta-deficient patients (from seven unrelated families), and 10 of the parents of the latter. Three different forms of the C8 alpha-gamma subunit were observed: 34/68 normal individuals were found to have a C8 alpha-gamma triple band (termed C8 alpha-gamma 1, C8 alpha-gamma 2, C8 alpha-gamma 3 variants), 23/68 the C8 alpha-gamma 2 and C8 alpha-gamma 3 variants, and 11/68 the C8 alpha-gamma 1 and C8 alpha-gamma 3 variants. In contrast, all C8 beta-deficient patients had detectable C8 alpha-gamma 2 and C8 alpha-gamma 3 variants but lacked the C8 alpha-gamma 1 variant in addition to the C8 beta subunit. Three out of ten parents of the C8 beta-deficient patients were found to have the C8 alpha-gamma triple band, whereas 7/10, like their children, had the C8 alpha-gamma 2 and C8 alpha-gamma 3 variants only. We conclude that there is a linkage between the C8 alpha-gamma pattern and C8 beta deficiency. These data may support earlier findings that in humans the genes encoding for C8 alpha-gamma and C8 beta are closely linked on chromosome 1.

Adult↗
PubMed1992

Complement component deficiencies and infection: C5, C8 and C3 deficiencies in three families.

Three families are described with complement component deficiencies. In one family, five children had C5 deficiency; in a second family, two children had C8 deficiency and one child in a third family had C3 deficiency. The index cases were identified during screening of patients with recurrent pyogenic infections, recurrent meningitis and meningococcaemia. Two of the five C5 deficient patients had recurrent meningitis and meningococcaemia, two had recurrent respiratory tract infections and otitis and one was healthy. One of the C8 deficient patients had meningitis, meningococcaemia and pneumonia, whereas his sibling with the same deficiency was healthy. The patient with C3 deficiency had four episodes of meningitis and recurrent otitis.

Child↗
PubMed1989

Secretion of the terminal complement proteins, C5-C9, by human platelets.

The terminal complement components, C8 and C9, and to a lesser extent C5, C6, and C7, but minimal amounts of C3, were shown to be associated with washed human platelets. In unactivated platelets, the complement components were detected in the platelet pellet by hemolytic assays after centrifugation and disruption of the platelets by freeze-thawing. However, after platelets had been activated by collagen, thrombin, or aggregated IgG to induce aggregation, the complement components were released into the supernatant. The rank order of hemolytic activity of C9, C8, C7, C6, and C5 detected in the supernatants of activated platelets was quite different from that found in serum from the same donors, in the same assays. In particular, the serum C7 hemolytic titer was more than twice the serum C9 hemolytic titer, whereas the activity of C9 detected from platelets was more than twice that of C7. This argues against a purely nonspecific uptake of these proteins by platelets from plasma. The functional role of terminal complement components released from platelets during activation is unknown, but it is tempting to speculate that these proteins may have a role in platelet-dependent immunological tissue injury. Because the C5b-9 membrane attack complex activates platelets, it is possible that release of terminal complement proteins serves to amplify platelet activation and may also play a role in diseases in which complement membrane attack complexes have been implicated.

Blood Platelets↗
PubMed1988

The C8-binding protein of human erythrocytes: interaction with the components of the complement-attack phase.

C8-binding protein is an intrinsic membrane protein of the human erythrocyte. It inhibits the complement (C5b-9)-mediated lysis in a species-restricting manner. In the present study we incorporated C8bp, isolated from human erythrocytes, into sheep erythrocytes (SRBC). SRBC, normally sensitive to lysis by human C5b-9, became insensitive to lysis. Furthermore, we found that C8bp is incorporated into the membrane-attack complex C5b-9, most probably by interacting with C8, since C8bp has an affinity for C8, particularly for the C8 alpha-gamma-subunit. Antibodies to C8bp react with the C8 alpha-subunits and with C9, pointing to the possibility of a partial homology between these proteins.

Animals↗
PubMed1987

Human alveolar macrophages synthesize active complement components C6, C7, and C8 in vitro.

We investigated whether serum-free human alveolar macrophage cultures synthesize active C6, C7, and C8. There was a significant binding of polyclonal anti-human C6 antibodies to agarose beads incubated with unstimulated macrophages for 24 or 48 h. Endotoxin stimulation of the macrophages was necessary for significant binding of polyclonal anti-C7 and anti-C8 antibodies to agarose beads co-cultured for 48 or 96 h. Two monoclonal antibodies (poly C9-MA and MCaE11) specific for a neoantigen of polymerized C9 in the terminal complement complex (TCC), bound to beads mainly incubated with endotoxin stimulated macrophages. The MCaE11 was more sensitive than the poly C9-MA in detecting the C9 neoantigen on beads incubated with the macrophages or human serum diluted 1:16. We thus conclude that human alveolar macrophages synthesize active C6, C7, and C9 that together with C5 and C9, assemble as the TCC on co-cultured agarose beads. Activation of the alternative pathway on the agarose with generation of fixed C3 and C5 convertases is a prerequisite for the subsequent generation of the TCC.

Adult↗
PubMedDate not supplied

C8 beta subunit deficiency in a patient with recurrent neisserial infections.

A 15-year-old woman with a history of recurrent episodes of meningococcal infections was admitted to our hospital with signs and symptoms indicating a meningeal inflammation. Since in the last few years some of the patients affected by recurrent meningococcal infections have been recognized to have selective complement deficiencies, the patient's serum was studied for determining the complement function. C8 was found to be present only in traces, with a pattern of partial identity as compared with that of the normal human serum. Moreover, total hemolytic complement was undetectable and could be completely restored with purified C8, but not with other complement components; thus, we concluded for the presence of a C8 deficiency state. Further reconstitution experiments carried out with sera having selective deficiencies of either C8 beta or C8 alpha-gamma subunits allowed us to recognize the presence of a dysfunctional C8 molecule lacking the beta chain, but possessing the alpha-gamma subunit. The clinical history of the patient, characterized by recurrent meningococcal infections, further supports the current concept of an increased susceptibility of the C8 beta-deficient patients to Neisseria meningitidis infections.

Adolescent↗
PubMed1986

Isolation of a human erythrocyte membrane protein capable of inhibiting expression of homologous complement transmembrane channels.

Erythrocytes are poorly lysed by homologous complement, whereas they are readily lysed by heterologous complement. This phenomenon had been attributed to an interference by the cell surface with the action of complement components C8 and C9. To isolate the responsible membrane constituent, detergent-solubilized human erythrocyte (EH) membranes were subjected to affinity chromatography by using human C9-Sepharose. The isolated protein had a mass of 38 kDa and, incorporated into liposomes, was highly effective in inhibiting complement-mediated channel expression, including the C5b-8, membrane attack complex, and tubular polymer of C9 channels. Antibody produced to the 38-kDa protein caused a 20-fold increase in reactive lysis of EH by isolated C5b6, C7, C8, and C9. The antibody did not enhance C5b-7 uptake, but it affected C9 binding to the target cell membrane. Antibody to human decay-accelerating factor, used as a control, had no effect on reactive lysis of EH. Anti-38-kDa protein did not enhance the action on EH of C8 and C9 from other species, indicating that the action of this regulatory protein is species specific. It was therefore termed homologous restriction factor (HRF). Blood cells other than erythrocytes, such as polymorphonuclear leukocytes, also exhibited cell-surface HRF activity. In immunoblots of freshly isolated EH membranes, anti-38-kDa HRF detected primarily a 65-kDa protein, suggesting that the 38-kDa protein constitutes an active fragment of membrane HRF. Because of the specific binding reaction observed between HRF and C8 or C9, HRF was tested with anti-human C8 and anti-human C9. A limited immunochemical relationship of HRF to C8 and C9 could be established and solid-phase anti-C9 proved an efficient tool for the isolation of HRF from solubilized EH membranes.

Blood Proteins↗
PubMed1991

Gene responsible for deficient activity of the beta subunit of C8, the eighth component of complement, is located on mouse chromosome 4.

Sera from 73 strains of mice were tested for hemolytic activity through the classical and the alternative pathways (CP and AP) in a single radial hemolysis assay. Sera from 16 out of 45 laboratory inbred strains had no lytic activity, and Ouchterlony analysis with anti-C5 serum showed them to be C5-deficient. Sera from 2 out of 28 strains derived from wild mice also had no lytic activity, but the C5 molecule was detectable in both. The hemolytic activity of sera from these strains can be restored by the addition of partially purified human C8 or human serum deficient in C8 alpha-gamma, leading us to conclude that strains M.MOL-MSM (MSM) and Mae are deficient in the beta subunit of C8. Typing of (DBA/2J X MSM)F1 hybrids and of progeny of a backcross to MSM showed that this C8 deficiency is controlled by a single recessive gene, designated C8b; the allele with hemolytic activity is C8b1; and the allele with no activity C8b0. Because of synteny homologies in mouse and human, we looked for and found close linkage between C8b and Pgm-2. Typing of recombinant mice for Mup-1 mapped the C8b locus 2.3 centimorgans (cM) telomeric to Pgm-2 on mouse chromosome 4.

Animals↗
PubMed1986

The C8A and C8B loci are closely linked on chromosome 1.

Close linkage was demonstrated between the loci governing the polymorphisms of complement component C8 alpha-gamma (C8A) and beta (C8B). Both C8 loci were linked to the chromosome 1 marker loci PGM1 and Rh. The distance between the two C8 loci and PGM1 appeared identical in males and females. A female/male ratio of 1.6 was observed between the two C8 loci and Rh. No evidence for linkage between the C8 loci and Fy was found. Preliminary results of this study were presented at the Eighth International Workshop on Human Gene Mapping, Helsinki, August 1985 (Rogde et al. 1985b).

Chromosomes, Human, Pair 1↗
PubMed1986

Functional C8 associated with human platelets.

Haemolytic assay for C8 revealed its association in functionally active form with washed human platelets. Platelet-bound C8 haemolytic activity was inhibited by F(ab')2 anti-C8 and was undetectable in the platelet suspension obtained from three C8 deficient patients. Incubation of platelets from C8 deficient individuals in normal plasma did not restore C8 haemolytic activity, indicating that platelets do not absorb C8 from plasma in vitro during platelet preparation. Thrombin, a mediator of the platelet release reaction, did not induce the release of C8 from normal platelets. Conversely, lysis of EAC1-7.9 by platelet bound C8 was not accompanied by release of beta-thromboglobulin or serotonin from the platelets. C8 was detected in a homogenate prepared from platelets as well as in the supernatant collected after high speed centrifugation of the homogenate. The association of C8 with platelets as an individual component rather than as part of the C5b-9 membrane-attack complex was supported by the following evidence: platelet bound C8 eluted from a Sephacryl S-200 column at the same volume as C8 from normal human serum; F(ab')2 anti-C8, but not F(ab')2 anti-C5, inhibited platelet C8 activity; the platelet homogenate, which lysed EAC1-7.9, had no effect on EAC43 which are susceptible to the lytic activity of the C5b-9 complex.

Blood Platelets↗
PubMed1986

Homologous species restriction in lysis of human erythrocytes: a membrane-derived protein with C8-binding capacity functions as an inhibitor.

An intrinsic membrane protein with a m.w. of 65,000 that can bind human C8 has been identified after separation of human erythrocyte membrane proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrotransfer to nitrocellulose sheets. The protein, tentatively designated as the C8-binding protein (C8bp) could be isolated from papain-treated erythrocyte (E) membranes by phenol-water extraction and isoelectric focusing. In a functional assay, with chicken (ch) E as target cells, C8bp inhibited the lysis of ch E C5b67 intermediates by human C8 and C9, whereas the lysis by rabbit C8 and C9 was not affected. Because the decay accelerating factor (DAF) from human erythrocyte membranes also inhibits the activity of C3/C5 convertases in an homologous system, we tested whether or not a DAF activity was present in C8bp. C8bp, however, did not accelerate the decay of the classic C3 convertases. Thus, it appears that C8bp and DAF are two different factors of E membranes with a similar molecular size inhibiting different sites of the activation cascade of complement while they can function synergistically to minimize the self-inflicted damage by complement.

Blood Proteins↗
PubMed1985

Genetic deficiency of the alpha-gamma-subunit of the eighth complement component in the rabbit.

Genetic deficiency of the alpha-gamma-subunit of the eighth complement component (C8 alpha-gamma) was found in a strain of the New Zealand White rabbit. The serum of this deficient rabbit lacked the immunochemical and functional alpha-gamma-subunit of C8. Mating tests indicate that the C8 alpha-gamma deficiency is transmitted as a simple autosomal recessive trait with the following physiologic characteristics. The body weight at the first week of life, mature weight, and litter size of the deficient animals were smaller than those of heterozygous and normal ones. In addition, survival rates for the first 3 mo of life of the deficient animals tended to be lower than those of heterozygous and normal littermates.

Animals↗
PubMed1986

C3-independent immune haemolysis: mechanism of membrane attack complex formation.

The isolated active complex of C5 and C6, C56, was found to bind to EAC142 in the absence of C3 or C7, and to form a unique intermediate, EAC14256, which is susceptible to lysis by the addition of C7, C8 and C9. Further studies revealed that C56 alone could bind to EAC142 but not to E, EA, EAC1 or EAC4, nor to EAC14 in the absence of C7, that the C56 binding to EAC142 was highly dependent on temperature and on the ionic strength of the buffer, and that the degree of EAC14256 formation from EAC142 and C56 depended on the amount of C2 on EAC142 and on the amount of added C56. These findings suggest that C2 or C42 on EAC142 may be an acceptor for C56. In addition, C56 appears to bind to EAC142 much more efficiently than to unsensitized erythrocytes, even in the presence of C7. Thus, binding of C56 to EAC142 is likely to be an initial step of membrane attack complex formation in C3-independent immune haemolysis.

Animals↗