PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Complement C6”

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 55 records · Page 3Linked to original sources
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↗
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↗
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↗
PubMed1992

Immunological evaluation of late complement component-deficient individuals.

The possible contribution of additional immunologic variables to the susceptibility of late complement component-deficient individuals to meningococcal disease has not been systematically examined in previous studies. Thus, we studied three groups of patients: (1) 24 healthy individuals, (2) 8 complement-sufficient individuals with a history of recurrent bacterial meningitis, and (3) 19 complement-deficient individuals with prior meningococcal infection. No statistical differences were noted among the three groups for the following parameters: the absolute number and the percentage of lymphocytes; CD3+, CD4+, CD8+, CD20+, and CD16+ cells; and the CD4+/CD8+ ratio. The concentration of C4 and circulating immune complexes was also similar among the groups. The concentrations of IgG, IgM, and IgA were slightly, but significantly, decreased in the complement-deficient individuals. Of interest, the coefficient of spontaneous and lipopolysaccharide-stimulated activation of neutrophils was significantly depressed in the deficient individuals. We hypothesize that the terminal complement components may participate in maximal neutrophil activation.

Adolescent↗
PubMed1977

Complement-induced decrease in membrane mobility: introducing a more sensitive index of spin-label motion.

We have used spin-labeling to investigate complement-induced changes in lipid organization of antibody-sensitized sheep erythrocyte membranes. The spectrum of methyl 5-doxylstearate incorporated into the lipid component of sheep erythrocyte membranes is typical of a membrane bilayer. The membranes from complement-lysed erythrocytes have a small, but statistically significant, reduction in fluidity when compared to membranes from osmotically-lysed erythrocytes, as indicated by a small increase in T'. In theory, measurements of the widths of the outer hyperfine extrema should be more sensitive to motion than the separation of the outer hyperfine extrema (2T'). Our results indicate that the half-width at half-height of the outer hyperfine extrema show a severalfold greater percentage change than T'. The sign and magnitude of these changes are in general agreement with previous predictions. Our results imply that motional corrections to the S formalism of Hubbell, Gaffney, and McConnell are necessary because spin-label motion appears to be explicitly represented in this type of electron spin resonance spectra.

Animals↗
PubMedDate not supplied

Evidence suggesting the occurrence of C3-independent intravascular immune hemolysis. Reactive hemolysis in vivo.

The authors present circumstantial evidence for the involvement of reactive hemolysis, i.e., C3-independent binding of the cytolytic C5b-9 complement complex to bystander red cells (RBC), in a case of intravascular immune hemolysis. Fresh serum obtained from a 6-year-old patient during the hemolytic episode, but not obtained thereafter, induced C5b-9-dependent hemolysis of human RBCs but the indirect C3 antiglobulin test remained negative. Particles (presumably RBC ghosts) isolated from the patient's plasma anticoagulated with EDTA at the peak of hemolysis were coated with C5b-9 complexes, whereas the direct antiglobulin test was strongly positive for IgA, only weakly positive for IgG, and negative for C3. Moreover, neither the autoantibodies isolated by elution (IgG plus IgA), nor free serum autoantibodies (IgA alone) activated complement in vitro. Additionally, serum samples collected later during the 12-month period of observation contained normal levels of C3, C4, C8, and C9, but markedly reduced levels of C7. These serums all produced strong reactive lysis in agarose plates, but not in test tubes. These results appear compatible with the working hypothesis that the intravascular hemolytic episode in this patient might have arisen through a local initiation of complement activation with subsequent C3-independent binding of C5b-9 to and hemolysis of bystander RBCs.

Anemia, Hemolytic, Autoimmune↗