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PubMed1992

C7 M/N protein polymorphism typing applied to inherited deficiencies of human complement proteins C6 and C7.

C7 M/N typing, the determination of the complement component C7 M/N phenotypes, was successfully used in family studies to trace haplotypes bearing C7 deficiency genes. Furthermore, it was shown to be preferable to C7 allotyping based on isoelectric focusing (IEF) since it distinguishes two common alleles (C7*M and C7*N), whereas one common C7 IEF allele (C7*1) predominates in most populations. It is also the more sensitive method, as it enabled detection of very low amounts of abnormal C7 molecules in the third generation of a combined subtotal C6/C7-deficient subject and thus confirmed that this partial deficiency gene is not silent in heterozygotes. In this respect C7 M/N typing is even more informative than DNA restriction fragment length polymorphism typing which will assess the presence but not necessarily the functional status of a gene. C6 and C7 genes are tightly linked and therefore C7 M/N typing was also applied to tracing C6 deficiency genes in families. C6/C7 haplotype analysis of South African C6-deficient (C6Q0) subjects revealed a strong allelic association of C6*Q0 and C7*M.

Alleles↗
PubMed1991

Functionally active complement proteins C6 and C7 detected in C6- and C7-deficient individuals.

Two sensitive sandwich ELISAs based on monoclonal antibodies directed to native C6 and C7 allowed the detection and quantitation of these complement proteins in 20 out of 37 serum samples from individuals who had previously been classified as deficient in these proteins as assessed by immunochemical and/or functional assays. Furthermore, serum from four C6-deficient and one combined C6-/C7-deficient individual showed an increase in the terminal complement complex (TCC) and a decrease in native C6 and C7 after complement activation as assayed by specific ELISAs. Despite their (incomplete) deficiencies, these individuals therefore possess functionally active terminal complement proteins with respect to their ability to generate the TCC. As these individuals have no history of a susceptibility to neisserial infections, even low concentrations of functionally active C6 and C7 may provide sufficient protection against those micro-organisms whose destruction requires TCC formation.

Antibodies, Monoclonal↗
PubMed1992

Complement genetic markers in schizophrenia: C3, BF and C6 polymorphisms.

Polymorphic variants of C3, BF and C6 complement factors have been investigated in schizophrenic patients subdivided according to the existence or not of a family history of both schizophrenia and other psychiatric disorders. To analyze the contingency tables, besides the usual methods, log-linear models have been fitted. Significant associations have been found in the C3 system, with a decrease of C3*F in patients (contradicting previous findings), and in the BF system, with a decrease of FS phenotype among patients (confirming some previous results). No association has been found for the C6 polymorphism (in accordance to previous results). Therefore, the present findings only partially confirm previous results and do not clarify the relationship between complement genetic markers and schizophrenia, stressing some statistical difficulties.

Alleles↗
PubMed1979

Simultaneous occurrence of hereditary C6 and C2 deficiency in a French-Canadian family.

The sera of four sisters were found to lack the sixth component of complement (C6) and the serum of one was also partially deficient in the second component (C2). Two other blood relatives were found to be heterozygous for both deficiencies, while only one sibling had normal values. The father of these eight siblings was heterozygous for C2D and C6D and in the third generation, six children were heterozygous for C6 deficiency was treated for chronic active brucel-transmitted; the C6 deficiency was not linked to the HLA system, while the C2-deficiency segregated with the haplotype A10,B18. The proband, homozygous for C6 deficiency was treated for chronic active Brucellosis and in another sibling with C6 deficiency, toxoplasmosis was diagnosed. Neither bleeding disorders nor a tendency to collagen diseases have been observed and the opsonic activity was normal in the sera of all family members.

Adult↗
PubMed1979

Recurrent meningococcal meningitis with absence of the sixth component of complement: an evaluation of underlying immunologic mechanisms.

A 51/2-year-old black girl with recurrent meningococcal meningitis and absence of the sixth component of complement (C6) is reported. To explore the pathogenesis of recurrent neisserial infections in C6 deficiency, a detailed analysis of her immune competence was conducted. Her serum had normal chemotactic, opsonic, alternative complement pathway, and specific antibody activity, but lacked complement-mediated bacteriolytic activity. In addition, her C6-deficient serum was indistinguishable from normal serum in a complement-dependent assay of phagocyte bactericidal activity. Absent bacteriolysis remains the only consistent defect associated with recurrent neisserial infections and absence of one of the late-acting complement components.

Blood Bactericidal Activity↗
PubMed1990

Prophylaxis against Neisseria meningitidis infections and antibody responses in patients with deficiency of the sixth component of complement.

Forty South African patients with homozygous deficiency of the sixth component of complement (C6) have been identified in an area where group B meningococcal meningitis is endemic; 22 of the 24 proband cases presented with recurrent meningococcal meningitis. In a 2- to 4-year prospective study, patients with recurrent infections who received monthly prophylactic long-acting penicillin were significantly protected from subsequent neisserial infection compared with those who did not receive penicillin (P = .02, Fisher's exact test). Heterogeneous susceptibility to neisserial infection was confirmed by following C6-deficient patients who presented with one or no Neisseria meningitidis infections. These patients, on no prophylaxis, had significantly fewer infections (P = .004) than did patients who presented with recurrent disease. Functional C6 activity was restored by transfusion of fresh frozen plasma in a C6-deficient patient resistant to conventional antibiotic treatment. Antibody levels to the serotype 2 outer membrane proteins were significantly elevated in C6-deficient patients compared with control groups (P = .001).

Antibodies, Bacterial↗
PubMed1992

[Genetic polymorphism of complement component six (C6) in five Han subpopulations].

By using polyacrylamide gel isoelectric focusing followed by immunoassay, the polymorphism of Complement Component Six (C6) was investigated in five Han subpopulations in China. The following gene frequencies were obtained Zhengzhou Han: C6*A 0.4521, C6*B 0.5228, C 6*B2 0.0183, C6*R 0.0068; Lanzhou Han: C6*A 0.4612, C6*B 0.5218, C6*B2 0.0170; Huhhot Han: C6*A 0.4452, C6*B 0.5286, C6*B2 0.0214, C6*R 0.0048; Xi'an Han: C6*A 0.4899, C6*B 0.4874, C6*B2 0.0126, C6*R 0.0101; Hakka of Meizhou, Guangdong Province: C6*A 0.4569, C6*B 0.5152, C6*B 0.0279 (C6*R is the frequency of rare alleles).

China↗
PubMed1991

Functional and structural domains of the sixth component (C6) of human complement.

The effects of serine protease inhibitors, diisopropyl fluorophosphate (DFP) and phenylmethanesulfonyl fluoride (PMSF), on hemolytic activity of C6 were reinvestigated. C6 was inactivated in a range of 1-10 mM by both of the inhibitors as previously reported. Limited proteolytic digestion was also studied to elucidate the functional and structural domains of C6. The major fragments produced by trypsin, plasmin, or lysyl endopeptidase could not be separated unless disulfide bonds were disrupted, but Staphylococcus aureus V8 protease yielded several fragments, each of which was not linked by disulfide bond. When C6 labeled with [3H]DFP was subjected to limited digestion with V8 protease, a fragment with a molecular weight of 38 kilodaltons (kDa) was mainly labeled and other fragments of 53 kDa and 26.4 kDa were also faintly labeled, while fragment 35 kDa wasn't labeled, indicating specific domains reactive with DFP. On the other hand, when C6 with or without DFP treatment was digested with V8 protease and those fragments were incubated with C5 and subjected to sucrose density ultracentrifugation, fragments 53, 38, 35 and 27.5 kDa interacted with C5 in both cases. These results suggest that C6 modified by DFP can interact with C5, and the amino-terminal sequences of fragment 38 and 35 kDa suggest the binding domain of C6 with C5 takes place within the two short consensus repeats.

Complement C6↗
PubMed1991

Polymorphisms of serum proteins in Japanese patients with vascular diseases. I. Factor XIIIB, plasminogen and complement types in primary varicose veins.

The polymorphisms of the B subunit of coagulation factor XIII (F13B), plasminogen (PLG), complement C6, C7, factor B (BF) and factor I (IF) were studied among 21 unrelated Japanese patients with primary varicose veins (PVV) by isoelectric focusing followed by immunoblotting. The allele frequencies for F13B*2 and IF*A in PVV patients were significantly higher (F13B*2, p = 0.0047; IF*A, p = 0.0006) than those in healthy controls (n = 60). Significant associations of F13B 2 allotype [p = 0.0220, relative risk (RR) = 13.9] and IF A allotype (p = 0.0006, RR = 10.0) with PVV were observed; however, no significant association of PLG, C6, C7 or BF allotype with the disease was found.

Adult↗
PubMed1977

[Relations between complement and blood coagulation (author's transl)].

The complement system as well as the blood coagulation system are involved in several disease processes so that it seems to be of interest to search for direct or indirect functional relations. Both systems can be activated in vitro as well as in vivo by the same substances, as e.g. endotoxin or antigen antibody complexes. In spite of these common characteristics a direct functional relationship between complement and plasmatic blood coagulation could not be established. Complement and blood coagulation do not interact with each other. Activated complement components, however, can induce platelet aggregation and release reaction both of which may accelerate but not trigger intravascular coagulation. Therefore, indirect relations between complement and blood coagulation can be found in patients or in animal experiments, especially after activation of intravascular coagulation. These interactions depend on further mediator sugstances of both systems.

Animals↗
PubMed1979

Quantitation of the membrane attack complex of complement in an air-driven ultracentrifuge.

A sensitive assay of complement (C) activation via either the classical or alternative pathway was developed by evaluating assembly of the terminal complexes (C5b-9)2 or SC5b-9. Activation of serum containing [125I]C7 resulted in the formation of a stable, radiolabeled complex which was separable from its precursors by sedimentation in an air-driven ultracentrifuge. The radioactivity in the sediment was directly proportional to the amount of complex formed and assembly of the complex could be detected after C activation by aggregated IgG in concentrations as low as 10 micrograms/ml. Mild detergents such as Triton X-100 could be included in the reaction mixture, because they affected neither the assembly nor the integrity of the complexes. The assay, which detects both assembly of the membrane attack complex (MAC or (C5b-9)2) on target membranes and formation of SC5b-9 in fluid phase, measures the potential of certain substances to trigger the cytolytic phase of C regardless of whether the classical or alternative pathway was activated. However, by using serum depleted of either factor B or C1q, activation of either pathway can be assessed individually.

Cell Membrane↗