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PubMed1988

Detection of the terminal complement complex in patient plasma following acute myocardial infarction.

The mechanisms of inflammation responsible for the myocardial tissue damage seen after an acute myocardial infarction (AMI) have not been clearly identified. Recent lines of evidence, demonstrating depressed sera levels of individual complement components in patients after myocardial infarction, have suggested involvement of the complement (C) system in micro- and macrovascular injury subsequent to AMI. The present study assessed the role of complement as a mediator of myocardial inflammation by quantifying products of complement activation including, the terminal complement complex (TCC) the cytolytic component of the complement system, C1rC1s-C1 inhibitor complex and C3bBbP complex, formed following activation of the classical and alternative pathway, respectively, and anaphylatoxins C3a and C5a in 41 patients following AMI. Plasma TCC and C1rC1s-C1 inhibitor complex concentrations increased up to 32-fold (P less than 0.001) and 8-fold (P less than 0.001), respectively, while the C3bBbP complex, C3a des-Arg and C5a des-Arg each increased over 2-fold (P less than 0.001) 16 h after AMI, and were only minimally detectable during non-inflammatory myocardial conditions. Furthermore, TCC concentrations increased over 150% (P less than 0.001) one day after patients reinfarcted, subsequent to hospitalization for a primary AMI. These results demonstrate activation of complement after AMI and suggest that inflammatory mediators of the complement system may contribute to myocardial tissue damage during the infarction process.

Adult↗
PubMed1987

Activation of the third component of complement (C3) detected by a monoclonal anti-C3'g' neoantigen antibody in a one-step enzyme immunoassay.

A previously produced and characterized rat monoclonal antibody recognizing a neoantigen in the human C3'g' fragment was used as the capture antibody in an enzyme-linked immunosorbent assay. Detection was made using a polyclonal rabbit anti-human C3d and a peroxidase-linked anti-rabbit Ig antiserum. The activity in normal human EDTA plasma was found to be 3% of that in a zymosan-activated serum pool. Fractionation experiments revealed that most of the activity in normal plasma, in vivo activated plasma and in vitro activated serum eluted in one peak with a molecular weight corresponding to iC3b. A positive correlation (P less than 0.01) was found between the present assay and a previously established two-step C3d ELISA both with respect to normal plasma, individual patient samples and consecutively drawn samples following artificial in vivo activation. Complement activation assays based on specific antibodies to 'activation antigens' should be preferred whenever available since they enable direct, rapid and specific quantification of the actual fragment(s).

Antibodies, Monoclonal↗
PubMed1989

A new method for the estimation of C3d. Affinity clearance of C-determinant-bearing C3 molecules and fragments followed by estimation of C3d by ELISA.

A method is described to quantitate human complement fragment C3d. Test samples were treated with a predetermined excess of anti-C3c-Sepharose beads in the presence of EDTA to remove all the C-determinant-bearing C3 molecules or fragments. C3d left in the supernatant was then estimated by ELISA. Using this method, C3d could be estimated accurately in normal plasma samples. A good correlation (r = 0.93) was observed between C3d values obtained by this method and values obtained by the widely used method of Perrin and coworkers. The average C3d plasma concentration was 2.8 mg/l (SD = 0.7 mg/l, n = 21). The interassay coefficient of variation using a normal plasma pool (C3d 2.7 mg/l) was 8.3% and using normal plasma pools in which the C3d concentrations were raised to 10.3 and 17.4 mg/l by the addition of aged normal serum the levels were 8.0 and 7.5% respectively. Intra-assay coefficients of variation with these samples were 4.6, 3.0 and 2.8%, respectively. 16 patients with renal dysfunction had C3d levels in the range of 4.3-10.0 mg/l and 15 patients undergoing continued ambulant peritoneal dialysis had levels of 3.3-12.2 mg/l. The C3d content in peritoneal dialysate of patients undergoing dialysis varied from 9.3 to 383 micrograms/l.

Antibody Specificity↗
PubMed1990

Detection of C3bBb-stabilizing activity (C3 nephritic factor) in the serum from patients with membranoproliferative glomerulonephritis.

It is known that membranoproliferative glomerulonephritis (MPGN), hypocomplementaemia and C3 nephritic factor (C3NeF) are closely related to each other, and the presence or absence of C3NeF in the serum is important for evaluating the nature of MPGN. However, some difficulties have been encountered in detecting this factor and therefore a new assay permitting the direct detection of C3NeF without purifying IgG from the patient's serum has been devised. Using this assay method, C3bBb-stabilizing activity was observed even in sera from MPGN patients who were non-hypocomplementaemic. Furthermore, among 98 cases with hypocomplementaemia. C3NeF was found to be absent in 66 cases.

Complement C3 Convertase, Alternative Pathway↗
PubMed1991

A flow cytometric assay for measuring complement receptor 1 (CR1) and the complement fragments C3d and C4d on erythrocytes.

A flow cytometric assay (FCA) was developed to measure complement receptor 1 (CR1) and the complement fragments C3d and C4d on erythrocytes. It was possible to measure these parameters accurately with intra- and interassay coefficients of variation of 2.0% and 6.5% respectively. The method was able to discriminate between low and high levels of erythrocyte CR1, C3d and C4d. Comparison with a previously described RIA method gave excellent correlation coefficients with r2 values of 0.94, 0.93 and 0.91 for CR1, C3d and C4d respectively. The flow cytometric assay was used to measure CR1, C3d and C4d on the erythrocytes of 98 healthy individuals and the 95% upper limits for C3d and C4d were established. There was a wide distribution of CR1 levels amongst these individuals but their C3d and C4d levels were low and often not above background. The possible application of this method in clinical medicine is discussed.

Antigens, CD↗
PubMed1988

Complement activation occurs through both classical and alternative pathways prior to onset and resolution of adult respiratory distress syndrome.

We have previously reported that plasma concentrations of the terminal complement (C) complex (TCC), C5b-9, increased significantly 2 days prior to onset of adult respiratory distress syndrome (ARDS) and also 1 day preceding its resolution. To determine the pathway of complement activation that preceded development and resolution of this acute inflammatory lung injury in septic patients, we quantified the C1rC1s-C1 inhibitor complex and the C3bP complex, which are generated following activation of classical and alternative complement pathways, respectively. Two days prior to diagnosis of ARDS, the plasma C1rC1s-C1 inhibitor complex and C3bP complex levels increased 22 and 14%, respectively. Furthermore, significant correlations were identified between concentrations of the TCC and C1rC1s-C1 inhibitor complex (r = 0.73, P = 0.003) and also with the levels of the TCC and C3bP complex (r = 0.81, P = 0.002) before onset of ARDS. Equally of interest, the C1rC1s-C1 inhibitor complex and C3bP complex concentrations increased 68 and 35%, respectively, 1 day before resolution of ARDS. Similarly, significant elevations of TCC concentrations preceding resolution of ARDS correlated with C1rC1s-C1 inhibitor complex (r = 0.66, P = 0.02) and also with C3bP complex (r = 0.72, P = 0.002) levels. Our results indicate that both the classical and alternative complement pathways are activated prior to onset of ARDS and also before its resolution in septic patients.

Complement Activating Enzymes↗
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↗
PubMed1996

Complement activation by 3-mercapto-1,2-propanediol immobilized on gold surfaces.

Thiol-modified surfaces are chemically well defined and suited for surface biological model experiments and biomaterials research. 3-Mercapto-1,2-propanediol (mercaptoglycerol, MG), immobilized on gold, spontaneously binds immunoglobulins from human serum and activates the complement system. The surface-bound complement factors were detected by ellipsometry-antibody techniques. The overall complement activation was subsequently corroborated independently with enzyme immunosorbent assay (EIA) and sheep and chicken erythrocyte haemolytic complement techniques. EIA experiments indicated elevated levels of C4d, but no significant increase of factor Bb was evident in the test serum from the MG system. The haemolytic assays show that MG surfaces consume complement factors from both pathways. Ellipsometry revealed that immunoglobulin G (IgG) and complement factor 1q (C1q) are transiently antibody detectable on MG after exposure to whole serum by the use of antibody techniques. Complement factor 3 (C3), C2, C4 and properdin could be detected on the surface, but not factors H and B. The total adsorbed mass and particularly C3 antibody deposition were suppressed by using EGTA-Mg2+ serum. The results suggest that MG surfaces initially activate complement via the classical pathway. Other IgG binding surfaces also appear to behave in a similar manner.

Animals↗
PubMed1982

Complement mediated lysis in chickens.

Rat erythrocytes, when either injected i.v. into chickens, or incubated in vitro with chicken serum, will be lysed within minutes. This lysis is complement dependent but does not involve specific antibodies since Ig-free bursectomized chickens behave in exactly the same way as normal chickens with high levels of haemagglutinating antibodies. The lysis is mediated by activation of complement component C3 via the alternative complement pathway and various observations lead us to doubt the functional existence in this lytic reaction of the classical complement pathway.

Animals↗
PubMed1989

Expression of the binding molecules for factor B and its fragment, Bb, of human complement on human monocytes after in vitro cultivation.

We have examined the expression of the binding molecules for Bb of human complement on the surface of resting and cultured human monocytes. Flow cytometry using biotinylated anti-B antibodies and phycoerythrin-avidin showed that although resting monocytes did not bind Bb significantly, monocytes cultivated for 24 h in the presence of fetal calf serum were capable of binding with Bb and its precursor B, but not with Ba fragment. The Bb-binding molecules were pronase-sensitive, suggesting that membrane proteins are associated with the Bb-binding molecules. In addition to human monocytes, liquid paraffin-induced guinea pig inflammatory macrophages were also found to express Bb-binding molecules on their surface. This implies that Bb receptor-like molecules become expressed during activation and differentiation of monocytes, just as observed with the C3d-receptor of monocytes.

Animals↗
PubMed1995

Chronically administered 3-nitropropionic acid induces striatal lesions attributed to dysfunction of the blood-brain barrier.

3-Nitropropionic acid (3-NPA), an irreversible inhibitor of succinate dehydrogenase, was administered to rats and the characteristics of the neuronal damage were investigated. Injections of 3-NPA (15 mg/kg s.c.) every 2 or 3 days for 1-2 weeks induced a mild neuronal loss and neutrophil invasions in the striatum (STR). The same administration for 4 weeks induced specific symmetric lesions in the lateral STR although the size was variable in each animal. Inside the lesions, strong neutrophil invasions and a strong immunoreaction for IgG, C3 as well as complement factor C3b/C4b receptor (C3b/C4br) were detected. Lesioned sites lost the immunoreaction for GFAP while the marginal areas contained abundant GFAP-labeled astrocytes around the vessels. In intoxicated animals, there was a weak but stout immunoreaction for IgG and C3b/C4br localizing around vessels in the STR even when there were no lesions or neuronal loss. The data suggest that the blood-brain barrier dysfunction is responsible for the specific vulnerability of the STR for the toxin.

Animals↗
PubMed1994

Biologically active recombinant human complement factor H: synthesis and secretion by the baculovirus system.

A complete cDNA clone (4.3 kb) encoding human complement factor H (hCFH; 155 kDa) has been cloned into the pVL1393 baculovirus expression vector and transfected into Spodoptera frugiperda Sf9 insect cells. A biologically active (92 +/- 15%) 140-kDa protein was secreted into the medium with a yield of more than 5 mg/liter. This is the first report of synthesis of biologically active recombinant hCFH in a heterologous system.

Animals↗
PubMed2005

Complement activation in diabetic ketoacidosis and its treatment.

Recent studies support the presence of an inflammatory response during the treatment of diabetic ketoacidosis (DKA). The objectives of this study were to monitor the complement activation products C3a, C4a, Bb, and C5b-9 prior to, during, and after correction of DKA. All patients had increased levels of C3a at 6-8 h and 24 h (P<0.05). C4a was increased in only one patient. Bb showed an upward trend at 6-8 h, and was significantly elevated at 24 h (P<0.05); sC5b-9 was elevated in all patients prior to treatment or in the first 6-8 h of treatment. Results indicate that the alternative pathway may be the primary pathway of activation. These results extend the observation that both DKA and its treatment produce varying degrees of immunologic stress during the time when acute complications are most likely to occur.

Adolescent↗