Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Complement C7”

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 127 records · Page 7Linked to original sources
PubMed1991

In vitro demyelination by serum antibody from patients with Guillain-Barré syndrome requires terminal complement complexes.

Serum from 7 patients who had acute-phase Guillain-Barré syndrome with high anti-peripheral nerve myelin antibody activity (54 to 210 units/ml) was compared with serum from 3 patients in the recovery phase (0 to 17 units/ml) and serum from 7 disease control subjects (0 to 24 units/ml) and 7 normal control subjects (0 to 7 units/ml) for its ability to demyelinate rodent dorsal root ganglion cultures. The demyelinating capacity of each serum was quantitated by counting the percent of damaged internodal segments in each of four cultures. All sera from patients in the acute phase GBS caused 50 to 78% demyelination, in contrast with 6 to 19% by the sera from all 3 patients in the recovery phase and all other control subjects. The degree of demyelination correlated with anti-peripheral nerve myelin antibody activity of the sera and demyelination was complement-dependent. Further, cultures were treated with an immunoglobulin M (IgM) fraction of an acute-phase Guillain-Barré syndrome plasma plus normal human serum depleted of complement component C7. Only those cultures treated with IgM and C7-depleted human serum reconstituted with purified C7 resulted in 50.8% demyelination, which was significantly greater than the 14.2 to 16.2% demyelination observed in the presence of heat-inactivated, C7-depleted human serum plus purified C7 or in the absence of C7 or antibody. In summary, our work suggests that anti-peripheral nerve myelin antibody in Guillain-Barré syndrome mediated complement dependent-demyelination of rodent dorsal root ganglion cultures. Further, this in vitro demyelination required generation of activation complexes of the terminal complement cascade.

Acute Disease↗
PubMed1976

Increased ion permeability of planar lipid bilayer membranes after treatment with the C5b-9 cytolytic attack mechanism of complement.

The ion permeability of planar lipid bilayers, as measured electrically, was found to increase modestly upon treatment with purified complement complex C5b,6 and complement components C7 and C8. The subsequent addition C9 greatly amplified this change. No permeability changes occurred when components were added individually to the membrane, or when they were used in paired combinations, or when C5b, C7, C8, and C9 were admixed prior to addition. Thus, there is a significant parallel between the permeability changes induced in the model membrane and damage produced in biological membranes by the C5b-9 complement attack sequence. The efficiency of membrane action by C5b-9 was critically dependent on the order in whcih components were added to the membrane. There were also differences in the electrical properties of membranes treated with C5b-8 and C5b-9, though in both cases the enhanced bilayer permeability is best attributed to the formation of trans-membrane channels. Collectively, the data are consistent with the hypothesis that the mechanism of membrane action by complement involves the production of a stable channel across the lipid bilayer, resulting in cell death by colloid-osmotic lysis.

Cell Membrane Permeability↗
PubMed1989

A case of hereditary combined deficiency of complement components C6 and C7 in man.

Immunological investigation of a patient presenting with candidiasis and toxoplasmosis revealed a combined deficiency of C6 and C7. Deficiency of C6 was total, but small amounts (less than 1 microgram/ml) of apparently normal C7 were present in the serum. All family members (three sibs and both parents) were heterozygous for the combined deficiency. This is only the second reported case of combined homozygous deficiency of the closely linked and immunochemically similar proteins C6 and C7, and only the third kindred in which this defect has been demonstrated.

Adult↗
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↗
PubMed1989

[Clinical signification of localization of S protein and late components in the skin from lupus patients].

We studied frozen tissue of lesional skin and normal-appearing skin from SLE patients and DLE patients by immunofluorescence. S-protein and late components (C5, C7, C9) were localized at the dermal-epidermal junction of the lesional skin from SLE and DLE patients. All specimens of normal-appearing skin from patients with SLE were free of deposits of S-protein and late components. These results suggest that late components may play a role in the development of skin lesions of SLE and DLE.

Adult↗
PubMed1986

Enhanced reactive lysis of paroxysmal nocturnal hemoglobinuria erythrocytes. Studies on C9 binding and incorporation into high molecular weight complexes.

As part of a broader analysis of the mechanism(s) by which the most sensitive (type III) paroxysmal nocturnal hemoglobinuria (PNH) erythrocytes are excessively sensitive to reactive lysis by isolated C5b6, C7, C8, and C9, we have compared type III PNH (PNH-III) and normal human E in respect to both total specific binding of 125I-C9 and the proportion of cell-bound C9 appearing in high molecular weight (HMW) complexes. In a previous report, we found that after exposure to purified C5b6 and 125I-C7, specific C7 binding and, by implication, EC5b-7 formation were equal for PNH-III E and normal E. In the present study, C8-dependent binding of 125I-C9 to PNH-III EC5b-7 and normal EC5b-7 was also similar, although lysis of the PNH-III E was up to five times greater; that is, PNH-III E required fewer bound C9 molecules to produce an effective lytic site than did normal E. To quantify radioactivity in monomeric and HMW forms of membrane-bound C9, lysed and unlysed E were subjected to low ionic strength buffers to convert all E to ghosts. These ghosts were solubilized in 0.1 or 2% SDS (without reduction) and electrophoresed on 2.4-11% polyacrylamide gradient gels followed by autoradiography and densitometric scanning. With 0.1% SDS, broad, heterodisperse zones of HMW C9 were recovered from both PNH and normal ghosts; the amounts of C9 incorporated into the HMW complexes were similar for PNH-III E and normal E. In selected experiments, 125I-C7 could be shown in these same HMW bands. When membranes were solubilized in 2% SDS, the overall proportion of HMW C9 complexes compared with dimer and monomer C9 was reduced on both PNH and normal membranes. In many, but not all experiments, more of the highest mol wt C9 complexes were detected from PNH-III E membranes solubilized in 2% SDS than from normal or PNH-II E membranes similarly treated. When antibody-sensitized E were lysed by purified C1-C9, PNH-III EA bound far more C9 than did normal EA, and both lysis and C9 incorporation into HMW complexes were markedly and proportionately increased over normal; however, lytic efficiency of 125I-C9 bound to PNH EA was equal to or less than that bound to normal EA.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies↗
PubMed1987

Terminal complement components play a role in the expression of C5a.

This study examined the expression of C5a detected antigenically (RIA) and functionally (PMN-myeloperoxidase release) consequent to classical or alternative pathway convertase cleavage. Maximal C5a expression occurred when C5 was cleaved in the presence of the later-acting complement components, C6, C7, and C8. This effect was detected by using both purified components and normal human serum immunochemically depleted of C7 or C8 and reconstituted with the purified component. C6 alone was not sufficient to augment C5a expression. Subsequent incubation of C6 and C7 with C5 cleaved in the absence of the terminal components was not sufficient for C5a release. Repeated freezing and thawing of C5 cleaved in the absence of C6 and C7 produced C5a equivalent to that detected when convertase cleavage occurred in the presence of the terminal components. Mild detergent treatment of convertase-cleaved C5 was not sufficient for C5a release. We believe that these data indicate a role for the terminal complement components in the expression of both C5a antigen and function. The mechanism for this effect is not known, but it may involve conformational changes in the C5 molecule that occur during membrane attack complex formation.

Complement C5↗
PubMed2026

Proteomic profiling of cephalic vein reveals potential biomarkers for arteriovenous fistula neointimal hyperplasia in ESRD patients.

Arteriovenous fistula (AVF) is the preferred vascular access for patients with end-stage renal disease; however, its failure is primarily due to neointimal hyperplasia. Five patients who underwent initial AVF surgery served as the control group, and another five patients with failed AVF surgery served as the experimental group. Herein, we employed mass spectrometry (MS)-based quantitative proteomics coupled with tandem mass tag labeling to screen differentially expressed proteins (DEPs) in the anastomotic cephalic vein, followed by bioinformatics analyses and verification experiments. A total of 121 DEPs were identified in the failed AVF group. GO analysis was primarily enriched in protein binding, nucleic acid binding, enzyme binding, mRNA binding, cadherin binding, catalytic activity, and cell adhesion molecule binding. KEGG pathways were mainly enriched in cell aggregation and adhesion, actin cytoskeleton, extracellular matrix-receptor interaction, PI3K-Akt signaling pathway, complement and coagulation cascades, and cholesterol metabolism. Protein-protein interaction network consisted of 86 (71.07%) DEPs, including complement VII (C7), factor IX (F9), SERPINC1, microfibril-associated glycoprotein 4 (MFAP4), complement C1s subcomponent, complement C1q subcomponent subunit A, complement C1q subcomponent subunit B, tissue factor, and von Willebrand factor, which interacting with numerous other proteins. In the expanded validation for different patients, C7, F9, SERPINC1, and MFAP4, were verified by immunohistochemical staining and Western blotting, which were consistent with the proteomics results. Collectively, this study identifies a series of potential diagnostic biomarkers, and explores the underlying mechanisms associated with AVF dysfunction.

Humans↗
PubMed1976

Lack of linkage between gene(s) controlling the synthesis of the seventh component of complement and the HLA region on chromosome No. 6 in man.

The family of an individual was studied who lacks the seventh component of complement in his serum (C7 homozygous deficiency). Both parents are C7 heterozygous-deficient. In this investigation, the following parameters were determined: complement components in functional and immunochemical tests; HLA-A,B antigens, HLA-D (MLC) determinants; the Bf system; glyoxalase I and B cell antigens. No evidence for linkage between the immunogenetic linkage group on chromosome 6 and gene(s) controlling the synthesis of the seventh component of complement was obtained. This is in according with the assumption that only genes controlling components of the initiating rather than the membrane attack unit of complement are linked to the HLA region.

Child↗
PubMed1975

On the mechanism of cytolysis by complement: evidence on insertion of C5b and C7 subunits of the C5b,6,7 complex into phospholipid bilayers of erythrocyte membranes.

The doughnut hypothesis of cytolysis by complement [Mayer, M. M. (1972) Proc. Nat. Acad. Sci. USA 69, 2954-2958] describes an annular structure made up of C5b-9 (complement factors C5b, C6, C7, C8, and C9) which becomes inserted in the lipid bilayer of the cell membrane, thus creating a hole. We now present initial explorations of this hypothesis. EAC1-6 and EAC1-7 (sheep erythrocytes carrying rabbit antibody and complement factors C1 through C6 or C1 through C7, respectively), prepared with either 125I-C3 or 125I-C5 were incubated with trypsin and the release of bound 125I was measured. In the case of 125I-C3, all of the radioactivity was released by trypsin from both intermediates. With 125I-C5, trypsin released all of the 125I from EAC1-6, but only 40-55% from EAC1-7. Possible reasons for resistance of the C5b subunit in EAC1-7 to tryptic digestion are discussed; in terms of the doughnut hypothesis it would be due to shielding by lipid molecules as a consequence of insertion into the lipid bilayer. In accord with this interpretation we have also found that C5b in EAC1-7, but not in EAC1-6, resists elution by 0.3 M NaC1. Similarly, we have found that 125I-C7 in EAC1-7 resists stripping by trypsin. Hence, we now propose the hypothesis that hydrophobic polypeptide chains from the C5b and the C7 subunits of C5b,6,7 complex become inserted in the phospholipid bilayer and that subsequent reactions with C8 and C9 open a channel across the membrane.

Animals↗
PubMed1989

C7 polymorphism in Japanese: new allele C7*8.

The polymorphism of C7 was investigated in neuraminidase-treated sera from 513 unrelated Japanese individuals using isoelectric focusing followed by an electroimmunoblotting technique. Besides the common phenotypes 5 rare variants including 2 types of new variants were detected. The family analysis suggested the hereditary occurrence of a new allele C7*8. The allele frequencies were: C7*1 = 0.8314, C7*2 = 0.0926, C7*3 = 0.0380, C7*4 = 0.0331, C7*6 = 0.0010, and C7*8 = 0.0039.

Alleles↗
PubMed1992

Combined total deficiency of C7 and C4B with systemic lupus erythematosus (SLE).

The first inherited combined total deficiency of C7 and C4B complement components associated with SLE is described in a young female. Functional C7 assays showed a homozygous C7 deficiency in the propositus and her sister, and an heterozygous one in their parents. C4 molecular analyses showed that both the propositus and her mother had two HLA haplotypes carrying only C4A-specific DNA sequences and a normal C4 gene number. Thus, only C4A proteins could be expressed, with resultant normal C4 serum levels. The coexistence of a combined complete C7 and C4B deficiency may therefore abrogate essential functions of the complement cascade presumably related to immune complex handling and solubilization despite an excess of circulating C4A. These findings challenge the putative pathophysiological roles of C4A and C4B and stress the need to perform both functional assays and C4 allotyping in patients with autoimmune pathology and low haemolytic activity without low serum levels of a classical pathway complement component.

Adult↗
PubMed1990

C7*9, a new frequent C7 allele detected by an allotype-specific monoclonal antibody.

Two sandwich ELISA for the quantitation of C7 in human plasma--one based on a monoclonal (MAb), the other performed with a polyclonal anti-C7 IgG--were established. Results from ELISA as well as from isoelectric focussing and immunoblotting with both antibodies revealed that the MAb is directed to an allotypic epitope on C7. About 6.7% of the plasma samples did not react with this MAb. Since these findings cannot be explained by the known alleles, the existence of a new C7 allele, C7*9, was suggested, whose product C7-9 is not detected by the MAb. A gene frequency of 0.21 C7*9 was assumed. When using conventional techniques C7*9 is included in the frequency of C7*1.

Alleles↗