[Evaluation of the role of circulating antigen-antibody complexes in the pathogenesis of glomerular nephropathies].

Immunofluorescence studies of the glomeruli in patients suffering from glomerulonephritis (GN) suggest the deposit of immune complexes from the circulating blood. Immune complexes were quantitated using a sensitive radioimmunoassay from sera of 41 patients with GN drawn at the time when renal biopsy was performed. Simultaneously, degradation products of C3 (C3d) were measured. Eleven of 12 patients with GN secondary to a systemic disease (usually LED) presented increased C1q-binding activity of their sera (C1q-BA). C3 was further demonstrated in 9 of these patients, suggesting the presence of circulating immune complexes. By contrast only 2 of 12 patients with idiopathic GN characterized by deposits of complement and IgG in the glomeruli exhibited increased C1q-BA. One of 17 patients with idiopathic GN without deposit of immunoglobulins and C3 in the glomeruli also had increased C1q-BA. The results observed in the group of patients with idiopathic GN with glomerular deposits could be accounted for either by a transitory or minimal presence of immune complexes or by local formation of complexes in the glomerular structures.