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PubMed1988

Solubilization of immune precipitates by complement in the absence of properdin or factor D.

Various experiments have demonstrated that immune precipitates (IPs) are not solubilized by complement in the absence of alternative pathway function. To determine whether the characteristics of the IPs were responsible for these observations, we studied the solubilization (Sol) of IPs formed by bovine serum albumin (BSA)-rabbit antiBSA and tetanus toxoid (TT)-human antiTT. Sera deficient in properdin solubilized a fraction of BSA-antiBSA precipitates, although only when the IPs were formed in antibody excess. The same sera solubilized TT-antiTT precipitates with some delay but almost as efficiently as normal serum. Factor D-depleted serum solubilized a fraction of TT-antiTT precipitates too, indicating that Sol may proceed through activation of the classical pathway only. Thus, the requirements for complement-mediated Sol depend on the characteristics of the IPs and do not necessarily include alternative pathway function.

Antibodies↗
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↗
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↗
PubMed1987

Leukotriene C4 production by normal-density and low-density eosinophils of atopic individuals and other patients with eosinophilia.

With the use of a percoll gradient separation procedure, eosinophils of individuals with asthma and with allergy could be separated into normal- and low-density cell fractions. The presence of low-density eosinophils possibly reflects an ongoing process of activation of these cells induced by the allergic reaction. Ca-ionophore-induced leukotriene (LT) C4 production, in the absence of added substrates, demonstrated a decreased potency for LT generation by low-density eosinophils compared with the LT generation of normal-density cells (57 +/- 33 ng and 103 +/- 44 ng per 10(6) cells, respectively). In contrast with the Ca-ionophore-induced LT formation, incubations with serum-treated zymosan in the presence of glutathione demonstrated higher productions of LTC4 with the low-density eosinophilic subpopulation compared with normal-density cells. This is compatible with a possibly higher expression of complement C3b receptors on the low-density eosinophils. Total arylsulfatase contents demonstrated that low-density eosinophils are not degranulated with respect to their small granules. Although release of the large granules by low-density eosinophils cannot be excluded, electron-microscopy studies indicated that degranulation is not the only (or major) factor that determines the density of the various eosinophilic subpopulations.

Cell Count↗
PubMed1992

Immunohistochemical evidence for C3bi involvement in Graves ophthalmopathy.

PURPOSE: To determine by immunohistochemical methods if components of the complement system are present in Graves ophthalmopathy extraocular and periocular tissues compared with non-Graves ophthalmopathy ocular tissues, and, if so, whether a qualitative difference exists. METHODS: Orbital muscle, periorbital muscle, and adipose tissue from 10 Graves ophthalmopathy patients were studied with in situ assays using monoclonal antibodies for C3bi and C5b-9 (the terminal attack complex) complement components. Extraocular muscle, periocular muscle, and adipose tissue from 12 patients treated for unrelated orbital disorders were used as controls. RESULTS: All nine Graves extraocular and periocular muscle tissues exhibited C3bi positive staining in an intense, localized oval- to spindle-shaped reaction that appeared to represent cells on a diffuse staining background of the endomysial and perimysial connective tissues with no staining of the muscle fibers themselves. Some reactivity was seen in 6 of the 12 control muscles, but this was much less intense than that of Graves ocular muscle tissue. Only two Graves muscle samples stained minimally with the monoclonal antibody for the C5b-9 terminal attack complex while none of the control muscle samples demonstrated reactivity. Orbital fat from Graves and control patients did not demonstrate any reactivity for C3bi or C5b-9. CONCLUSION: C3bi and not C5b-9 (the terminal attack complex) is present in Graves ophthalmopathy extraocular and periocular tissues in a qualitatively greater way than in control non-Graves ophthalmopathy ocular tissue. Consequently, C3bi may contribute to the pathophysiology of Graves ophthalmopathy.

Adult↗