PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Complement C4b”

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 73 records · Page 4Linked to original sources
PubMed1992

Expression of genes encoding receptors for IgG (FcRIII) and for C3b/C4b (Crry) in rat sciatic nerve during development and Wallerian degeneration.

Northern blots were used to examine the expression of genes encoding receptors for IgG (FcRIII) and for C3b/C4b (Crry) in rat sciatic nerve during development and Wallerian degeneration. Steady state levels of FcRIII (1.4 kb) and Crry (1.9 and 2.1 kb) mRNAs were higher in adult rat nerves than in 6 day and 21 day postnatal rat nerves, indicating that the expression of these receptors is developmentally regulated. The FcRIII and Crry cDNA probes also hybridized with total RNA from 3 day old rat Schwann cells and from adult rat peritoneal macrophages. The size of the FcRIII mRNA expressed by cultured Schwann cells (1.6 kb) differed from that expressed by peritoneal macrophages (1.4 kb); the two may be splice variants of one transcript or products of related genes. Peritoneal macrophages contained approximately 100 times higher FcRIII mRNA levels than Schwann cells. In contrast, steady state levels of both 1.9 and 2.1 kb Crry mRNAs were similar in cultured Schwann cells and macrophages. Nerve transection induced a generalized increase in the level of sciatic FcRIII mRNA (1.4 kb) 3 days post-surgery, whereas the level of Crry mRNA was increased only in the nerve segment immediately to the cut. The increase of FcRIII mRNA that occurred in Wallerian degeneration was most likely due to infiltration of macrophages, as FcRIII mRNA-positive macrophages were demonstrated in the degenerating nerves by in situ hybridization. FcRIII mRNA-positive macrophages were not found in normal nerve. The functions of FcRIII and Crry in peripheral nerves are uncertain, but they may be of significance in phagocytosis, antibody-dependent cellular cytotoxicity, and in local immune regulation.

Aging↗
PubMed1993

Alterations in C3, C4, factor B, and related metabolites in septic shock.

Forty subjects consisting of (i) patients with septic shock, (ii) patients with sepsis without shock, (iii) critically ill non-septic patients, and (iv) normal controls were studied for plasma C3, C4, factor B, iC3b, C4d, Bb, and SC5b-9 levels in an attempt to profile the pattern of complement activation in sepsis. Significant decreases in plasma C3 and C4 concentrations were observed in septic shock patients compared to normal as well as to critically ill subjects. When adjusted for illness severity, levels of C3 but not C4 showed significant differences between septic shock and critically ill patients. Concentrations of the complement metabolite Bb as well as the Bb to factor B ratio were significantly increased in septic shock patients. SC5b-9 levels were significantly higher in septic shock patients compared to normal as well as to critically ill subjects. No increases in C4d or iC3b were observed, but the iC3b to C3 ratio was higher in septic shock patients compared to that in normal subjects. In septic shock patients, there were significant correlations between SC5b-9 and Bb (P = 0.0213) concentrations and between C3 and Factor B concentrations (P = 0.0041). SC5b-9 levels also were correlated with lactate levels in septic shock patients (P = 0.0091). These findings demonstrate a metabolite pattern consistent with primarily alternative and terminal pathway activation in septic shock patients. Decreases in C4, a classical pathway component, may not be specific for septic shock and do not appear to be necessarily due to significant complement consumption/activation.

Adult↗
PubMed1995

Decreased levels of complement receptor 1 (CD35) on B lymphocytes in persons with HIV infection.

Previous studies have shown that complement receptor 1 (CR1) expression on erythrocytes is decreased under several conditions including HIV infection and autoimmune diseases. The goal of this study was to determine whether expression of CR1 on peripheral blood B cells, where this receptor plays a role during immune responses, is altered in persons with HIV infection. The B cells from rheumatoid arthritis (RA) patients were also assessed since this represents a group with known complement and B cell abnormalities. The CD19+ B cells from persons with either HIV infection or RA had significantly reduced levels of CR1 when compared with control donors (75 and 72% CR1+ versus 94% CR1+ for control donors). The reduction of B cell CR1 occurred in both the percentage of B cells positive for CR1 and the levels of CR1 found on positive cells. In contrast, CR1 on monocytes was not reduced. As shown in previous studies, CR2 was also found to be reduced on B cells from the HIV-infected persons and there was extensive overlap between the B cell subsets which lacked expression of CR1 and CR2. The complement receptor-negative B cells found in HIV-infected persons were not immature or activated as defined by their lack of expression of CD10 or B7, respectively. Elevated levels of C4d, a classical complement pathway-activation product, were detected in plasma from both HIV-infected and RA patients. These studies suggest that chronic complement activation occurring in persons with HIV infection or RA can affect the complement receptor phenotype of peripheral blood B cells. Since complement receptors are involved in activation of B cells, the subset that lacks CR1 may represent cells that have encountered immune complexes and may therefore be stimulated. Additionally, the downregulation of complement receptors may have significant effects on the ability of B cells to capture and present opsonized antigens.

Antigen-Antibody Complex↗
PubMed1992

Possible association of the extended MHC haplotype B44-SC30-DR4 with autism.

We previously reported that the complement C4B null allele appears to be associated with infantile autism. Since the C4B null allele is known to be part of the extended or ancestral haplotype [B44-SC30-DR4], we investigated the incidence of [B44-SC30-DR4] in 21 autistic children and their parents. This extended haplotype was increased by almost six-fold in the autistic subjects as compared with healthy controls. Moreover, the total number of extended haplotypes expressed on chromosomes of autistic subjects was significantly increased as compared with those expressed on chromosomes of healthy subjects. We conclude that a gene related to, or included in, the extended major histocompatibility complex may be associated with autism.

Adolescent↗
PubMed1992

Increases in immunoglobulin and complement in patients with esophageal or gastric cancer.

Based on data providing evidence that the enhancement of serum IgG and IgA is associated with the occurrence of infectious complications following surgery in patients with esophageal cancer, we examined the possible factors contributing to alterations in the serum IgG, IgA, IgM, C3, C4, and CH50 levels. A multiple linear regression analysis was made on data obtained from 71 patients with esophageal cancer and 57 with gastric cancer. In the patients with esophageal cancer, age and protein-calorie malnutrition (PCM) were related to the elevation of IgG levels while the stage of cancer was linked to that of IgA. The sex and IgM levels were also seen to be related. Age and the stage of cancer were associated with reductions in C3, C4, and CH50 levels, although in the patients with gastric cancer, the stage of cancer and elevations of these complement levels were related. Thus, age, PCM, and tumor malignancy are all factors related to the enhancement of IgG or IgA in patients with esophageal cancer.

Adenocarcinoma↗
PubMed1990

Genetic polymorphism of MHC class III and GLO in Chinese Yao nationality.

Yao nationality is one of the minority nationalities living mainly in South China (Guangxi Province). The purpose of this study was to provide data of MHC class III and GLO in Chinese Yao nationality and the different genetic background of Yao and Han nationality, the latter representing the major nationality in China. The genetic polymorphism of MHC class III and GLO in Chinese Yao nationality was determined. Previously the Japanese were considered to have the lowest C2*C frequencies (0.9386), but now we ascertained that the Yao have the lowest C2*C frequencies (0.9336). The data concerning gene frequencies of Yao are presented. They were also compared with the available data of Han.

China↗
PubMed1994

Structure of mouse protein S as determined by PCR amplification and DNA sequencing of cDNA.

The cDNA sequence of mouse protein S was derived by conventional PCR amplification from liver mRNA, initially using primers derived from the human cDNA sequence, followed by direct DNA sequencing. Seven overlapping PCR fragments covering all of the mature protein, part of the propeptide, and the 3' noncoding region were generated and sequenced. In some cases primers based upon the human cDNA sequence were ineffective. Subsequent successful amplification with mouse-derived primers to the same regions and comparison of the mouse and human sequences in these regions suggest that the failure of the human primers was due to insufficient degree of heterospecies identity. The mouse protein S cDNA sequence of the coding region shares 82% identity to human. The 3' noncoding region of mouse protein S cDNA has several small deletions and insertions compared to human protein S cDNA. Mature mouse protein S consists of 634 amino acids in a single polypeptide chain and displays domain organization similar to that for other species. The amino acid sequence of mouse protein S is about 80% identical to that of other species. Eleven glutamic acid residues were found in the amino terminal region and are predicted to be sites of gamma-carboxylation. Amino acid residues #80-244 are defined as four cysteine-rich repeat sequences homologous to epidermal growth factor. The remainder of the molecule is homologous to plasma sex steroid binding protein. The mouse protein S contains two potential N-glycosylation sites at positions #458 and 468 and is lacking the putative glycosylation site at #490 found in human protein S.

Amino Acid Sequence↗
PubMed1990

Complement activation products in idiopathic pulmonary fibrosis: relevance of fragment Ba to disease severity.

Immune complexes have been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a chronic inflammatory disease of unknown etiology. Using newly developed techniques to measure complement fragments, we assessed whether complement activation occurs in IPF and its relationship to circulating immune complexes (CIC), disease severity, and prognosis. We measured the fragments C3d, C4d, and Ba of the common, classical, and alternative pathway, respectively, along with the components C3, C4, and Factor B and CIC, in 18 patients and 19 healthy subjects. The fragment to parent molecule ratios C3d/C3, C4d/C4, and Ba/Factor B were derived. Complement determinations were repeated in 14 of the patients on a second occasion separated by 8-33 months (median 17 months) from the first. All parameters were higher in patients than controls, and the difference between the two groups was significant for C3d, C4d/C4, C3, CIC (P less than 0.05) and for C4d and Ba (P less than 0.01). Fragment Ba was found to correlate with disease duration and indices of disease severity, i.e., positively with the dyspnoea score (Rs = 0.44, P less than 0.04), the physiological score (Rs = 0.50, P less than 0.02), the fibrosis score (Rs = 0.45, P less than 0.04), and a composite clinical, radiological, and physiological score (Rs = 0.48, P less than 0.03) and negatively with the forced vital capacity (Rs = -0.47, P less than 0.03). Ba was higher in those patients who deteriorated on follow-up analysis than those who improved or remained unchanged (P less than 0.04). These results show that conversion products of all complement pathways are increased in IPF and demonstrate classical pathway activation. They also show that the measurement of Ba might prove a useful laboratory test of disease severity in this condition.

Adult↗
PubMed1994

Classical pathway complement activation in Kawasaki syndrome.

In this study the complement breakdown products C3d, C4d, Bb and membrane attack complex were measured in plasma of patients with Kawasaki syndrome. The results suggested strong activation of the classical activation pathway. However, there was no significant decrease in hemolytic titer or in the concentrations of the intact proteins C3, C4, and B. The relationship between the serum concentrations of cytokines and complement components was examined; increased interleukin-6 concentration on the fifth day after the onset of fever was found to correlate well with the C3 and B concentrations in serum obtained 5 days later. We conclude that complement activation occurred in Kawasaki syndrome via the classical pathway but that the inflammatory reaction was accompanied by increased production of complement components. As a result, there was increased formation of activation products without changes in the serum complement levels.

Child, Preschool↗
PubMed1989

Activation of the classical complement pathway in brain tissue of Alzheimer patients.

Positive immunohistochemical staining of Alzheimer brain tissue was obtained with antibodies to proteins associated with classical, but not the alternative, complement pathway. Clq, C3d, C4d are fractions of complement proteins that bind to tissue when the classical complement pathway is activated. Antibodies to these fractions stained senile plaques, dystrophic neurites and some neurofibrillary tangles. C5b-9 is the membrane attack complex which promotes cell lysis when assembled on the plasma membrane. An antibody to a neoantigenic site on this complex stained dystrophic neurites and many neurofibrillary tangles, but not extracellular amyloid. Properdin and fraction Bb of factor B, two proteins that bind to tissue when the alternative complement pathway is activated, were not detected immunohistochemically.

Aged↗
PubMed1990

Complement activation before, during and after cardiopulmonary bypass.

Plasma levels of the complement parent molecules C3, C4, and factor B and their split products, C3d, C4d, and Ba were measured in 12 patients undergoing cardiopulmonary bypass for coronary artery surgery. Alternative and common complement pathway activation, demonstrated by statistically significant rising levels of Ba (P less than 0.05), and C3d (P less than 0.05) and by elevated Ba:B (P less than 0.05) and C3d:C3 (P less than 0.05) ratios were found before the institution of cardiopulmonary bypass but following heparin administration suggesting that heparin may itself initiate alternative pathway activation. In addition, significant depletion of parent complement components and elevation of split product concentrations was seen during bypass suggesting classical and alternate pathway activation (P less than 0.01). This study clarifies the pathways of complement activation during bypass and presents evidence that heparin administration may initially activate the complement cascade.

Cardiopulmonary Bypass↗
PubMed1990

Generation of the membrane attack complex during haemodialysis: impact of classical and alternative pathway components.

1. The generation of the plasma SC5b-9 complex (the soluble form of the membrane attack complex) during haemodialysis was studied in 29 patients together with markers of the classical (C4d fragment) and alternative (Bb fragment) pathways and the common iC3b fragment. 2. In the patients dialysed with Hemophan and Cuprophan membranes, a rapid increase in the plasma levels of SC5b-9 complex, Bb fragment and iC3b fragment occurred within 15 min of the initiation of the haemodialysis procedure. The SC5b-9 complex and the Bb fragment concentrations remained at a plateau until 120 min thereafter. The iC3b fragment level showed a continual decline. 3. The C4d fragment concentrations remained unchanged, indicating that generation of the membrane attack complex is most likely due only to activation of the alternative pathway. 4. The generation of the membrane attack complex occurred throughout the full haemodialysis period. In patients treated with Polysulfon membranes no statistically significant variation in these components was noted. 5. The study shows that the membrane attack complex may be generated during the full period of the haemodialysis session and is a stable index of biocompatibility. 6. Moreover, it seems be involved directly in haemodialysis-associated phenomena.

Complement Activation↗
PubMed1989

Analysis of mutations causing steroid 21-hydroxylase deficiency.

Steroid 21-hydroxylase deficiency is the most frequent cause of congenital adrenal hyperplasia, an inherited inability to synthesize cortisol. Mutations causing this disorder have been characterized by hybridization analysis of patient DNA samples using cDNA and oligonucleotide probes, and by cloning and sequencing of mutant 21-hydroxylase (CYP21B) genes. About 20% of mutant alleles carry a 30 kilobasepair deletion that includes the 3' end of the CYP21A pseudogene, the C4B complement gene, and the 5' end of CYP21B, leaving behind a single CYP21A-like gene that is not functional. Non-deletional mutations include a nonsense mutation at codon 318 that is associated with severe disease and missense mutations at codons 172 (isoleucine to asparagine) and 281 (valine to leucine) that are respectively associated with intermediate and mild deficiency states. All of these alleles have apparently resulted from gene conversion events that have transferred deleterious mutations from the CYP21A pseudogene to CYP21B. Thus, recombinations between CYP21A and CYP21B probably account for the majority of 21-hydroxylase deficiency alleles.

Adrenal Hyperplasia, Congenital↗
PubMed1985

Human genes for three complement components that regulate the activation of C3 are tightly linked.

A new cluster of complement component genes, including C4BP, C3bR, and FH, is described. Family segregation data indicate that FH is linked to the genes for C4-bp and C4bR, previously reported to be linked and to maintain linkage disequilibrium. This cluster is not linked to the major histocompatibility complex, which contains the genes for the complement components, C4, C2, and factor B, or to the C3 locus. These data further suggest that the organization of genes for functionally related proteins in clusters may be a rule for the complement system.

Carrier Proteins↗
PubMed1985

Connective tissue proteins and phagocytic cell function. Laminin enhances complement and Fc-mediated phagocytosis by cultured human macrophages.

Brief exposure of culture-derived human macrophages to laminin, a glycoprotein component of all mammalian basement membranes that has a molecular weight of 1,000,000, led to enhancement of subsequent macrophage phagocytosis of EAC4b, EAC3bi, and EAIgG (sheep erythrocytes sensitized with IgG anti-Forssman antibody). This effect on macrophage phagocytosis occurred with both substrate-adherent and fluid phase laminin. Preincubation of macrophages, but not of EAC4b, with laminin led to augmentation of phagocytosis, suggesting that interaction with the phagocytic cell, but not with the opsonized particle, was required for laminin's effect. Laminin-stimulated phagocytosis of EAC4b was blocked entirely by a monoclonal antibody to CR1. Direct comparison of the phagocytic ability of macrophages adherent to laminin- and fibronectin-coated glass slides showed that fibronectin had a somewhat greater enhancing effect on phagocytosis. Nonetheless, the phagocytosis-enhancing effect of laminin was not due to contamination of the purified laminin preparation by fibronectin, since the laminin preparation was free of fibronectin, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and enzyme-linked immunosorbent assay; in addition, laminin-enhanced phagocytosis was decreased in the presence of laminin-specific antibodies. Laminin inhibited macrophage adherence and spreading, but selection of a laminin-binding macrophage subpopulation could not account for the laminin-induced increases in phagocytosis. We hypothesize that interaction with extracellular matrix proteins may represent an important activation stimulus both to the macrophages normally present in the extravascular compartment and to the phagocytic cells that have emigrated from the blood-stream into areas of inflammation.

Adjuvants, Immunologic↗
PubMed1981

Rocket immunoelectrophoresis of C4 and C4d. A simple sensitive method for detecting complement activation in plasma.

Activation of complement component C4 has recently been measured by the quantitation of C4 and C4d (a cleavage fragment of C4) by electroimmunodiffusion in gels containing specific precipitating antibodies for C4 and C4d (Rocket immunoelectrophoresis, RIE). Quantitative measurements of the complement component C4 and its fragment C4d were determined in rocket immunoelectrophoresis (RIE) and compared with measurements of total hemolytic complement activity (CH50) or concentrations of C4 as determined by single radial immunodiffusion (RID). This newly developed RIE assay shows activation of the classical complement pathway and involves electroimmunodiffusion in gels containing specific precipitating antibodies for C4 and its cleavage fragment, C4d. In 37 plasma samples, excellent correlation was demonstrated between the C4 in RIE and CH50 (r = .70) and C4 by RID (r = .87). In vivo activation of C4 was determined by measuring the ratio of C4d to C4; 21 of the plasma samples assayed had ratios greater than 1.1 indicating activation of C4. In 13 of the plasma samples there were correspondingly low CH50 values, whereas 8 had normal CH50 levels. Therefore, activation can be detected in those instances when other measurements (CH50 and C4 quantitation) are normal. Thus the RIE assay for plasma C4 activation appears to be the most sensitive method available for assessing in vivo activation of the classical pathway of complement.

Animals↗