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PubMed1987

Quantification of the complement receptor function on polymorphonuclear leukocytes: its significance in patients with systemic lupus erythematosus.

The function of complement receptors (CR1) on polymorphonuclear leukocytes (PMN) was assessed by C3b mediated binding of immune complexes (IC) to PMN. The binding of IC to CR1 on PMN depends on the activation of the classical complement pathway and was inhibited by the antibody to CR1 or C3b. CR1 function of PMN from patients with systemic lupus erythematosus was reduced compared with those from normal controls or patients with rheumatoid arthritis.

Antibodies, Monoclonal↗
PubMed1987

Complement activation following multiple injuries.

Complement activation was evaluated by assay of plasma C3dg and the terminal complement complex (TCC) in 19 patients with multiple injuries. In the nine patients with thoracic involvement, statistically significant increase of plasma TCC was found at first sampling (average 90 min post-trauma), and of C3dg after 24 hours. Such increase was not found in the ten patients without thoracic involvement. Heightened granulocyte elastase activity was found in bronchial lavage fluid 90 min after the trauma in three patients with thoracic injury. Pulmonary insufficiency (pO2/FiO2 less than 16 kPa on intermittent positive-pressure ventilation) arose in four patients. All four had raised plasma levels of TCC or C3dg on arrival at the hospital. Six patients with complement activation did not show pulmonary insufficiency. Although the series was relatively small, the results indicate that thoracic injury is particularly associated with complement activation, and that complement activation alone does not suffice to produce post-traumatic pulmonary insufficiency.

Adolescent↗
PubMed1985

Complement activation in primary biliary cirrhosis: an in vitro model.

Increased concentrations of C3dg were demonstrated in plasma from patients with primary biliary cirrhosis (PBC), indicating in vivo activation of C3. Rapid spontaneous C3 cleavage by the classical pathway was observed in vitro in serum and in EDTA plasma reconstituted with Ca++ and Mg++, suggesting the presence of complement-activating substances. On incubation with fresh normal serum, purified polyclonal IgM from patients with PBC induced C1 activation, C4 cleavage, and C3dg formation. No C3 cleavage was observed when PBC-IgM was incubated with a C2-deficient serum. We suggest that the complement activation in vivo in PBC, which occurs predominantly by the classical pathway and is characterized by increased concentrations of C1 activation complexes, decreased C4 concentrations, and hypercatabolism of C3, is attributable to an abnormal IgM population.

Complement Activation↗
PubMed1984

[The anticomplementary activity of 2 intravenous gamma globulin preparations in children with acute lymphatic leukemia].

Children with acute lymphocytic leukemia received gammaglobulin replacement therapy using either one of two i.v. gammaglobulin preparations in order to reduce the frequency and severity of infections during cytostatic treatment. Sera and EDTA-plasma taken prior to each infusion and following each infusion were analyzed for several complement components and immune complexes in order to assess in vivo anticomplementary activity. Preliminary data published in this paper show only little changes in the complement system. This may be related to fact that infusions were well tolerated. IgG-levels could be raised for more than 200 mg/dl by administration of doses around 150 mg/kg body weight.

Adolescent↗
PubMed1985

Immunonephelometric quantitation of complement split product (C3d) plasma levels in rheumatic disease.

A simple method is described for routine quantitative determination of C3d by laser nephelometry after precipitation of intact C3 by polyethylene glycol. Plasmas from 292 patients with different types of rheumatic disease was tested. Elevated C3d levels were a far more common finding than low levels of complement components C3 or C4, but despite the increased sensitivity, the test only seemed diagnostically useful for systemic lupus erythematosus and MCTD. Though a better test than the quantitation of C3 and C4, the value of C3d determination in rheumatic disease seems to be limited.

Adult↗
PubMedDate not supplied

Epitope specificities and quantitative and serologic aspects of monoclonal complement (C3c and C3d) antibodies.

Twenty-two monoclonal antibodies to human C3c and ten to C3d were obtained by hybridization after the immunization of mice with complement-coated human red cells and/or purified human complement components. C3c antibodies were variable in their agglutination reactions with cells coated with C3 by antibody in vitro; more consistent and potent reactions with these cells were observed with anti-C3d, and all anti-C3d reacted with red cells coated with C3 in vivo. Immunoradiometric assays were used to estimate antibody concentration, affinity, and epitope specificity. The antibody content in ascitic fluids varied from less than 0.1 mg per ml to 5.6 mg per ml. The estimated values of antibody affinities for Sepharose-coupled C3 ranged from 2.8 X 10(6) l per M to 5.0 X 10(8) l per M; on average, IgM antibodies had higher affinities than IgG antibodies. Competitive binding assays showed that the monoclonal antibodies recognized at least seven different epitopes, four on the C3c and three on the C3d fragment of C3. When the results of serologic and quantitative assays were compared, no convincing relationship was found between serologic performance and epitope specificity, antibody concentration, or affinity. IgM antibodies generally gave higher agglutination scores than IgG antibodies, and Ig class was the only useful predictor of serologic efficacy.

Animals↗
PubMed1985

Correlation of disease activity with circulating immune complexes (C1qbA) and complement breakdown products (C3D) in patients with systemic lupus erythematosus. A prospective study.

Most biologic effects of immune complexes are mediated through the activation of the complement system. The relationship between lupus disease activity and the presence of C3 breakdown products (C3d) and circulating immune complexes (CIC) as demonstrated with the C1q binding assay (C1qbA), was evaluated. Nearly all 13 systemic lupus erythematosus (SLE) patients had a stable disease course in this prospective study, nevertheless, in each patient the profiles of the serologic parameters were quite different. Despite the small number of investigated patients (13), it is concluded that irrespective of the disease activity, the serologic parameters could be either positive or negative. No relationship could be obtained between disease activity and the presence of C3d and/or CIC. Nor was there any evidence that the presence of CIC would indicate increased levels of C3 breakdown products (C3d). This observation argues against a pathogenetic significance of CIC detected by the C1qbA in SLE. In conclusion, the supposed link between the presence of CIC, consumption and activation of the complement system, and the activity of SLE needs further study.

Adult↗
PubMed1984

Determination of complement breakdown fragments C3d and its subfragments in health and disease.

The breakdown products of the third component of complement in approximately 400 samples were measured by rocket immunoelectrophoresis and two-dimensional electrophoresis using the method of Brandslund et al [3]. It was confirmed that the measurement of the C3d level provides useful information on increased C3 consumption irrespective of the synthetic rate. Furthermore, three subfragments with C3d but without C3c antigenicity were distinguished, which were designated as C3d1, C3d2, and C3d3. The subfragment C3d3 which migrated to the most anodal side was a predominant component in the plasma from patients with autoimmune diseases. Little C3d3 subfragment was detected in normal plasma and in normal sera incubated in vitro for 24 hr. Even in the normal sera converted completely in vitro which contained little intact C3, only a limited amount of C3d3 was detected. In the plasma from postsurgical patients in whom activation of the complement system was considered to be in an acute phase, C3d3 was detected, but the C3d2 level was higher than the C3d3 level. In the plasma from patients with systemic lupus erythematosus having the normal C3d level, C3d3 was a major fragment. It is predicted that the preponderant presence of C3d3 in plasma could be the result of chronic continuous complement activation by immune complexes.

Arthritis, Rheumatoid↗
PubMed1984

In situ characterization of cell infiltrates in human dental periapical granulomas. 2. Demonstration of receptors for the complement components C3b and C3d.

The inflammatory cell infiltrates in human dental periapical granulomas were studied through the demonstration of receptors (R) for fragments C3b and C3d of the complement component C3, C3bR and C3dR were detected in cryostat sections by the closed chamber hemadsorption technique. Sheep erythrocytes sensitized with rabbit IgM antibody and coated with human C3B or C3d were used as indicator cells. Of the 62 granulomas studied, 23 showed strong or moderate C3bR activity, and weak C3dR activity was detected in 5 out of 25 specimens. The C3bR activity was abolished by treatment with 0.25 mM periodic acid, indicating that carbohydrate is a part of the C3bR. Using an antiserum to C3R as first layer in indirect immunofluorescence experiments, the C3R was localized to cell membranes. The low C3dR activity indicates that a minor part of the mononuclear cells in the human periapical granulomas were B lymphocytes.

Adult↗
PubMed1986

C3d fragment of complement interacts with laminin and binds to basement membranes of glomerulus and trophoblast.

Two mouse monoclonal antibodies generated against human placental homogenate were found to react specifically with human complement component C3. In immunofluorescence of human tissues, these antibodies gave a bright linear staining outlining the glomerular basement membrane of the adult kidney and the trophoblast basement membrane of placenta. An identical staining pattern was observed with a rabbit C3d antiserum which also prevented binding of the monoclonal antibodies to tissue sections. Only negligible basement membrane staining was observed in the same tissues with antisera to human C3c, C5, IgG, IgA, or IgM. When interactions of C3 with basement membrane proteins were tested in enzyme immunoassays and column chromatography, C3(H2O) was found to bind efficiently to solid-phase laminin. Native C3 from fresh plasma did not bind to laminin but C3 from plasma treated with methylamine bound efficiently. When C3 was cleaved with trypsin, C3b and C3d but not C3c bound to laminin-Sepharose. The interaction of C3 and laminin was inhibited by soluble laminin and by high ionic strength. The results indicate that C3d, a biologically active breakdown product of C3, can be found in glomerular and placental basement membranes in the absence of signs for ongoing local complement activation or immune complex deposition. It is possible that binding affinities between C3 and basement membrane molecules, especially laminin, are involved in the retention of C3d at these sites. Such interactions between C3 and components of the glomerular basement membrane could play important roles in complement-related pathological processes of the glomerulus.

Antibodies, Monoclonal↗
PubMed1986

Regulation of human cytotoxic responses by complement: C3, C3b and C3d preparations enhance human allogeneic cytotoxic responses.

Complement components and complement breakdown products have been found to participate in the regulation of the immune response. In the present study we investigated the effect of C3 and its fragments, C3b, C3c and C3d on human allogeneic cell mediated lympholysis (CML). C3 and C3b at a concentration of 275 M X 10(-9) and C3d at a concentration of 330 M X 10(-9) enhanced human allogeneic CML by at least two fold. In contrast C3c did not affect CML responses. Both C3b and C3d had to be present at the initiation of the cultures in order to exert their effect. Similar doses of C3b and C3d did not affect the mixed lymphocyte responses (3H-thymidine uptake) while higher doses were clearly inhibitory. None of the preparations induced proliferative or cytotoxic responses in the absence of allogeneic stimulating cells. C3b and C3d added to the mixed lymphocyte cultures caused increased production of interleukin 2. We conclude that C3b and C3d facilitate allogeneic cytotoxic responses through increased production of interleukin 2.

Complement C3↗
PubMed1987

Isolation and analysis of complement activating aggregates from synovial fluid of patients with rheumatoid arthritis using monoclonal anti-C3d antibodies.

The complement activating aggregates in synovial fluids of patients with rheumatoid arthritis (RA) have been isolated using monoclonal IgM anti-C3d antibodies attached to solid phases, and the content of the material bound has been analysed. High levels of aggregated IgG bearing C3d were found in RA synovial fluids, and IgG was the major immunoglobulin bound from such synovial fluids by anti-C3d Sepharose. A strong correlation was shown between levels of aggregated IgG bearing C3d and complement activation, as judged by C3d levels. Significant (but less strong) relationships were also observed between C3d levels and both complement consuming and C1q binding activity. C3d levels and levels of aggregated IgG bearing C3d were both significantly associated with the numbers of polymorphonuclear leucocytes (PMNs) found in RA synovial fluids. From these results it is concluded that the aggregated immunoglobulins bearing C3d (particularly IgG) isolated from RA synovial fluids are responsible for activating complement and attracting PMNs into the joint space. Radioimmunoassay showed no correlation, however, between levels of aggregated IgG (or IgM) bearing C3d and rheumatoid factor (RF) activity bound by anti-C3d. In addition, the material bound by anti-C3d Sepharose from most synovial fluid polyethylene glycol precipitates did not contain either IgM or IgG RF. Thus both techniques show that the majority of complexes bearing C3d do not contain RF. As the complement fixing aggregates apparently contain only immunoglobulin and complement components the results raise the problem of how the aggregates are formed. It is suggested that RA IgG may remain aggregated after either antigen or antibody (RF) has dissociated from the complex.

Antibodies, Monoclonal↗
PubMed1995

Isolation of the C3 complement component and its C3d subunit from IY-1 fraction of Cohn's fractionation of human plasma.

C3 complement component and its C3d subunit were isolated from the IY-1 Cohn's fraction, which is the waste of industrially produced albumin and immunoglobulins. The first step was the fractionation of precipitate IY-1 by polyethylene glycol (PEG) 4000 to a final concentration of 16% PEG. The precipitate formed was separated by centrifugation. The supernatant contained the C3d subunit of C3, and the redissolved 16% PEG precipitate contained the C3 component. Then the supernatant and the dissolved precipitate were subjected to anion-exchange chromatography on DEAE-Toyopearl 650 M. In the last step fractions containing C3 and C3d concentrated by ultrafiltration were chromatographed on Sephacryl S-200.

Blood Proteins↗
PubMed1982

Measurement of the complement C3 breakdown product C3d by rocket immunoelectrophoresis.

A method is described for quantitative measurement of C3d in plasma and synovial fluid by the use of rocket immunoelectrophoresis after fractionation of the samples with 22% polyethylene glycol. This method has the advantage over radial immunodiffusion of being more sensitive (detecting C3d down to 3 mg/l) whilst proving equally reproducible. Investigations indicate that the collection of blood samples in EDTA prevents in vitro activation of C3 even after storage for up to 6 h at room temperature and up to 12 weeks at -70 degrees C. Elevated levels of C3d were found in a proportion of SLE and RA plasma samples and in synovial fluids from patients with inflammatory synovitis. It is suggested that C3 conversion in vivo may be assessed by measurement of C3d by the technique described, and when used in conjunction with measurements of complement components and immune complexes, offers a means of investigating complement catabolism by the classical and alternative pathways.

Animals↗
PubMed1981

Isolation of lymphocyte membrane complement receptor type two (the C3d receptor) and preparation of receptor-specific antibody.

A glycoprotein binding complement component C3d was isolated from media used for culture of Raji human lymphoblastoid cells. Analysis by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and gas/liquid chromatography indicated that the C3d-binding glycoprotein consisted of a single polypeptide chain with extensive intrachain disulfide bonds, a molecular weight of 72,000, and several different bound carbohydrates. Several lines of evidence indicated that this medium-derived C3d-binding protein originated from membrane complement receptor type two (CR2, the C3d receptor), presumably shed during membrane turnover. The C3d-binding protein bound to sheep erythrocytes coated with C3d (EC3d) but not to sheep erythrocytes coated with C3b (EC3b). Antisera, prepared by immunization with the purified C3d-binding glycoprotein, inhibited lymphocyte rosette formation with EC3d but not with EC3b. Analysis by sodium dodecyl sulfate gel electrophoresis of the radiolabeled and solubilized lymphocyte antigens reactive with the anti-C3d-binding protein sera revealed a single-chain cell-surface protein of molecular weight 72,000 that was apparently identical to the isolated C3d-binding protein. Parallel assay of lymphocytes for Cr2 by direct immunofluorescence with F(ab')2 anti-C3d-binding protein (anti-CR2) and rosette formation with EC3d indicated that both assays had the same specificity and nearly the same sensitivity. With both systems CR2 expression was limited to B cells, and was undetectable on T cells, monocytes, or neutrophils.

Animals↗