PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Complement C3b”

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 91 records · Page 5Linked to original sources
PubMed1992

Pattern of C3, iC3b, and C3d in patients hospitalized for acute asthma.

Twenty-three patients hospitalized for acute asthma were studied for a peripheral blood complement profile consisting of C3, C4, C3d, iC3b, C4d, and Bb concentrations. Compared with normals (n = 22) and patients (n = 10) with acute bacterial infections (ABI), asthmatic patients had significantly higher serum C3 concentrations (P less than .001). Plasma C3d levels and iC3b in asthmatic patients were both comparable to those observed in normal controls, whereas patients with ABI had significantly higher iC3b levels than both other groups. The ratio of iC3b to C3 concentrations were similar in asthmatic patients and controls, and iC3b levels were correlated with total serum C3 levels in asthmatic patients (r = .55, p less than .001) as well as in normal (r = .69, p less than .001). Both of these groups had significantly lower iC3b to C3 ratios compared with the ABI group (P less than .0001). Also observed in asthmatic patients were a significant correlation between serum C4 and C3 levels (r = .83, P less than .001) and a lower mean ratio of plasma C4d to C4 compared with normals (P less than .005). This profile of complement alterations is distinct from that observed in acute bacterial infection. These changes in asthmatic patients may relate to an acute phase reaction phenomenon affecting complement and/or complement regulatory proteins.

Acute Disease↗
PubMed1992

The absence of factor B activation products in scleroderma.

Previous investigators have reported the presence of complement activation products in scleroderma. Using an assay consisting of isoelectric focussing followed by immunofixation (IEF/IF) for alternative pathway activation product Ba, and an ELISA for C3d that we developed for evaluating lupus plasmas, we assayed 48 plasmas from patients with diffuse cutaneous scleroderma, 16 patients with the limited CREST variant, 2 patients with mixed connective tissue disease (MCTD) and 4 patients with Raynaud's disease. Ba was not detected in any patient's plasma. Only one plasma from a patient with CREST contained elevated levels of C3d. We cannot reconcile the absence of B activation products in our patients with scleroderma with the results of the previous report, and conclude that further studies are necessary.

Adult↗
PubMed1990

Structural requirements for C3d,g/Epstein-Barr virus receptor (CR2/CD21) ligand binding, internalization, and viral infection.

The structure of CR2, the human C3d,g/EBV receptor (CR2/CD21) consists of 15 or 16 60-70 amino acid repeats called short consensus repeats (SCRs) followed by a transmembrane and a 34-amino acid intracytoplasmic domain. Functions of CR2 include binding the human complement component C3d,g when it is covalently attached to targets or cross-linked in the fluid phase. In addition, CR2 binds the Epstein-Barr virus (EBV) and mediates internalization of EBV and subsequent infection of cells. In order to explore functional roles of the repetitive extracytoplasmic SCR structure and the intracytoplasmic domain of CR2, we have created truncated CR2 (rCR2) mutants bearing serial deletions of extracytoplasmic SCRs and also the intracytoplasmic tail. We then stably transfected these rCR2 mutants into two cell lines, murine fibroblast L cells and human erythroleukemic K562 cells. Phenotypic analysis of these expressed mutants revealed that 1) The C3d,g- and EBV-binding sites are found in the two amino-terminal SCRs of CR2, 2) expression of SCRs 3 and 4 is further required for high affinity binding to soluble cross-linked C3d,g, 3) the intracytoplasmic domain of CR2 is not required for binding C3d,g or EBV but is necessary for internalization of cross-linked C3d,g as well as for EBV infection of cells, 4) monoclonal anti-CR2 antibodies with similar activities react with single widely separated epitopes, and 5) no functional roles can yet be clearly assigned to SCRs 5-15, as rCR2 mutants not containing these SCRs show no major differences from wild-type rCR2 in binding or internalizing cross-linked C3d,g or mediating EBV binding and infection.

Animals↗
PubMed1991

Rat glomerular cells do not express podocytic markers when cultured in vitro.

A panel of cell-type specific monoclonal and polyclonal antibodies and lectins was used to examine the early, morphologically epithelial outgrowth of rat renal glomerular cells in culture. The cell type-specific reactivity of the monoclonal antibodies has been previously verified on tissue sections of rat kidneys at light and electron microscopic levels. Morphologically distinct epithelial cells grew out from the isolated glomeruli within 3 days in culture, followed by the growth of morphologically typical stellate mesangial-like cells. Endothelial and mesangial cells were positively identified from the early cultures (up to 10 days) with antibodies to a 350 kD protein, dipeptidyl peptidase IV, podocalyxin, factor VIII, OX-43 and with Bandeiraea simplicifolia (BS-I B4) lectin, and with antibodies to smooth muscle actin, desmin, Thy1.1 antigens and with Ricinus communis (RCA-1) lectin, respectively. The antibodies recognizing podocytes in vivo (antipodocalyxin, anti-O-acetyl GD3 ganglioside, anti-gp330, anti-C3b complement receptor, anti-vimentin and anti-CALLA) consistently failed to bind to the predominant epithelial cells in early cultures, although these antibodies readily bound to the cells of the intact glomeruli remaining in culture. The attempts to augment the expression of cell-type specific epitopes by culturing glomeruli on various matrices or by enriching the medium with various growth factors, failed to induce podocytic epitopes on the growing epithelial cells. Glomeruli from newborn rats cultured in vitro, but were also constantly negative for the markers of podocytes. In addition, we cultured glomerular-like bodies from in vitro were induced metanephric mesenchymes but failed to obtain evidence of growing podocytes. However, the epithelial cells reacted with antibodies to thrombospondin and cytokeratin that react with the parietal epithelium of glomeruli on tissue sections. The results show that early glomerular cultures consist of mesangial, endothelial and presumably parietal epithelial cells readily identifiable by immunocytochemical methods. No podocytes could be grown under the various growth conditions tested. This suggests that glomerular podocytes are effectively growth arrested and call for new approaches to obtain these cells in culture.

Animals↗
PubMedDate not supplied

Complement C3 cleavage product in synovial fluids detected by immunofixation.

54 synovial fluids (SFs), 46 of them derived from various inflammatory diseases (30 rheumatoid arthritis (RA) SFs, 8 undefined arthritis (UA) SFs, 8 psoriatic arthritis (PSA) SFs) and 8 SFs from degenerative joint diseases (OA) were tested for C3c split product, using the immunofixation method. There were significant differences in the C3c product between the four groups investigated. In the OA group in the mean the percentage of C3c was low in comparison to the native C3 (C3c = 2.95%). RA SFs and UA SFs showed considerably higher values (20.1% for RA and 23.2% for UA) which were statistically significant in comparison to the OA SFs. With the exception of one SF the PSA SFs exhibited a relatively low percentage of the cleavage product. Despite the one high value the average C3c content of the PSA SFs was not statistically different from the OA SFs. In contrast to this low percentage of the C3c split product the PSA SFs showed the highest C3 concentration of all groups (87.0 +/- 36.5 mg/100 ml). Immunofixation is a simple and effective tool to determine the C3c split product in SFs. It might also be helpful for establishing the differential diagnosis of PSA vs RA on the basis of the C3 level of the SF in those patients where an elevated level of C3 is present.

Arthritis, Psoriatic↗
PubMed1990

Expression of the C3d/EBV receptor and of other cell membrane surface markers is altered upon HIV-1 infection of myeloid, T, and B cells.

Human cell lines (the T-cell lines H9, Jurkat, and HUT102, the myeloid lines U937 and HL60, and the Raji B cell line) were infected with HIV-1. HIV-1 antigen could be detected by immunofluorescence analysis in more than 50% of T cells and myeloid cells 15 days after infection. Infection of Raji cells took more than 2-3 months. Studies of cell surface marker expression revealed remarkable changes after HIV-1 infection of Raji cells: expression of CR2 (C3d/EBV receptor, CD19, CD20, CD22, CD23, CD10, and surface IgM) were highly reduced, in the case of CR2 and membrane-IgM from 100 to 0%, whereas levels of CD37 and CD38 remained unaltered by HIV-1 infection. U937 cells showed a reduction of CD4 expression from 14 to 5% after HIV-1 infection; the CR3 expression slightly increased from 25 to 30%. In contrast, HLA-DR was only expressed (21%) after HIV-1 infection but not in uninfected U937 cells. Expression of HLA-DR could be detected also in HL60 cells (33%) after HIV-1 infection. In H9 cells, CD4 was reduced from 60 to 30% after HIV-1 infection, whereas HLA-DR and CD25/IL-2 receptor expression increased from 16 to 90% and from 0 to 50%, respectively. CD4 was reduced from 70 to 0% from Jurkat cells after HIV-1 infection, whereas expression of CR2 was only slightly diminished from 8 to 4%. Expression of CR1 and HLA-DR was slightly increased in these cells (1 to 3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Differentiation, B-Lymphocyte↗
PubMed1990

Immunobiology of chronic lymphocytic leukemia.

The majority of CLLs are of B lineage derivation with about 5 per cent of cases of T lineage. Although morphologically resembling the small peripheral blood B cell, by virtue of the expression of B cell restricted and associated cell surface antigens, B-CLLs are not the neoplastic counterparts of normal resting B cells. Similar to the peripheral blood B cell, B-CLLs express CD19, CD20, CD21, CD24, CD40, CD44, CD45R, and sIgM/D. However, unlike peripheral blood B cells, B-CLLs generally do not express C3b complement receptor, LFA-1, or CD22. In addition, B-CLLs express the T cell associated antigen CD5, and a number of antigens induced on normal B cells following in vitro activation (B5, Blast-1, CD23). These findings support the hypothesis that B-CLLs are the neoplastic counterparts of one or more unique subpopulations of normal B cells. Normal CD5+ B cells, which phenotypically resemble B-CLL, are present in fetal lymphoid tissues and in small numbers in adults. Moreover, normal CD5+ B cells are present in increased numbers in patients with autoimmune diseases and a subset of normal in vitro activated B cells phenotypically resemble B-CLL. Similar studies into the state of differentiation of T-CLL cells suggest that although most cases resemble normal activated T helper cells, a significant number are the neoplastic counterparts of natural killer cells. Recent studies have examined the function of B and T cells in B-CLL. Although controversial, these studies suggest that the in vitro response to mitogens and cytokines of B-CLL cells is abnormal. T cell proliferation in B-CLL is depressed due to an inability to produce sufficient T cell growth factor (IL-2) as well as a poor response to exogenous IL-2 possibly from ineffective IL-2 receptor expression. Purified populations of T helper and T suppressor cells demonstrate insufficient support of Ig production by normal B cells as well as excess suppression, respectively. These studies have further supported the previous hypothesis that the depressed cellular and humoral immunity in CLL is multifactorial with both abnormal B and T cell function.

Antigens, Differentiation↗
PubMed1990

[Quantitation of intact form of complement protein B and its fragment Ba in human serum by radioimmunoassay].

A sensitive solid-phase radioimmunoassay for intact complement protein B and its smaller fragment Ba is described which quantitates human B and Ba to 30 ng/ml. The assay was proved to be useful to evaluate the activation of the alternative pathway of the complement system by measuring intact B and Ba in normal human sera activated with zymosan. In sera from patients with systemic lupus erythematosus (SLE), the level of intact B was decreased and that of Ba was increased in the active phase, and the level of Ba was increased though intact B which was within normal limits in the inactive phase. The present result suggests that the activation of the alternative pathway is occurring both in the active and inactive phase in SLE, and the measurement of intact B and Ba concentration in pathological sera would be useful to evaluate the activation of the alternative complement pathway.

Adult↗
PubMed1979

A comparison of immunologic profiles and their influence on bacteremia in surgical patients with a high risk of infection.

Prospective sequential studies of the antibacterial function of neutrophils, lymphocyte responsiveness, opsonic capacity of serum and serum levels of C3(B), properdin, factor B, IgG, and albumin were made in 32 patients with severe burn injury (greater than or equal to 45%), 21 patients with severe multisystem traumatic injury, 20 high-risk, infected patients, and 22 renal transplant patients. Fifty-five episodes of bacteremia occurred in 37 of the 95 patients. Abnormal neutrophil function was clearly associated as a predisposing factor to these episodes, whereas there was no association between bacteremia and low serum levels of C3, IgG, factor B, or properdin. C3, factor B, and IgG usually rose following bacteremia as acute phase proteins, but there was evidence of a consumptive opsoninopathy in 11% of episodes. Defective opsonization was associated with a high risk of bacteremia only when there was a coexisting abnormality of neutrophil function (88% of such patients became bacteremic). None of 27 nonburned patients tested with delayed hypersensitivity antigens responded normally, and there was regularly depression of lymphocyte responsiveness to phytohemagglutinin-A and concanavalin-A in a whole blood assay related to serum immunosuppressive factors, but poor responsiveness was not associated with bacteremia.

Adolescent↗
PubMedDate not supplied

The biological role of the complement system and the clinical importance of complement measurements.

Properties of serum proteins belonging to the complement system, two pathways of the complement activation (classical and alternative pathway) as well as the physiological role of the complement system are discussed. Complement has essential importance in some physiological processes: In the induction of the humoral immune response, in the elimination of immune complexes and in the protection against bacterial and viral infections. After a short discussion of the genetics of the complement system, the principle and possibilities of clinical applications of the complement measurements are described. Finally, different approaches to the therapeutic manipulation of the complement system are discussed.

Angioedema↗