ABSTRACT
Serum levels of the C3 nephritic factor (C3NeF), an IgG autoantibody directed against the C3bBb convertase of the alternative complement pathway, and of eight complement components (C1q, C4, C3, C3d, C5, C9, fB and properdin) were measured in 109 serum samples from 27 patients with idiopathic membranoproliferative glomerulonephritis (MPGN) (type I, 20 cases, and type II, 7 cases) and 14 patients with secondary MPGN. Correlations between the concentrations of C3NeF, serum complement levels and progression of the renal damage were studied during the course of the disease in 14 patients with C3NeF activity. The results showed that (1) C3NeF activity was more frequent in patients with type II MPGN than in patients with type I disease; nevertheless there was a high incidence of this splitting activity in patients with secondary MPGN, (2) high levels of the complement components were present in patients with MPGN, (3) low levels of C3 occurred frequently in type II disease and in secondary MPGN, (4) there was no correlation between C3, fB and C3NeF levels, (5) the presence of C3NeF was associated with a more rapid deterioration of renal function. Longitudinal studies showed that serum levels of C3NeF were not satisfactory for monitoring the clinical course of the illness and, in this respect, are similar to the levels of other autoantibodies in patients with autoimmune disease. As MPGN is a clinical syndrome with various pathogeneses, we suggest that the autoantibody, C3NeF, should be considered only as a marker of some forms of MPGN.
Subject(s)
Complement C3 Nephritic Factor/blood , Complement Inactivator Proteins/blood , Glomerulonephritis/immunology , Autoantibodies/analysis , Complement C3/metabolism , Complement System Proteins/metabolism , Humans , Immunoglobulin G/immunology , Kidney Function Tests , Regression AnalysisSubject(s)
Glomerulonephritis/etiology , Adult , Aged , Complement C3/analysis , Complement Factor B/analysis , Creatinine/blood , Female , Glomerulonephritis/immunology , Humans , Male , Middle AgedABSTRACT
Activation of the alternative complement pathway (AP) has been investigated in 79 serial serum samples obtained from 28 patients which had different types of glomerulonephritis. Serum factors activating the AP of the complement system have been detected in 12 patients with various forms of glomerulonephritis. Immune complexes (IC), levels of complement components of the classical and the alternative pathways and cobra venom factor activity were measured. Serum specimens were subcategorized as 2 study populations: (i) patients with serum factors activating AP and (ii) patients with both serum activators and IC. Although CoVF-AH50, properdin factor B and C3 concentrations were comparably depressed in these two groups, the levels of Clq and C4 were very low only in patients with circulating IC. These data were highly suggestive of AP activation due to serum factor. In contrast the patients also showing circulating IC had activation of both pathways. The presence of these factors suggests that renal damage can be determined by other immunological stimuli.
