Acute glomerulonephritis. Immunofluorescent and electron-microscopic observations in sporadic cases.

The authors studied by immunofluorescent and electron microscopy renal biopsy specimens from 29 patients with various glomerular diseases. Poststreptococcal glomerulonephritis was characterized by the presence of complement (beta1C) in the mesangium and/or on the basement membrane in all cases. Immunoglobulin G (IgG) was also present in less than half of the cases in the same distribution. Electron microscopy, carried out in six cases, revealed no uniform ultrastructural change: minimal subepi helial deposits were observed in three cases, intramembranous deposits were seen in two cases, and the basement membrane was normal in one case. Glomerular abnormalities during the courses of some systemic diseases were similar. Mild renal involvement was characterized by only beta1C deposition. This finding raises the question whether a mechanism other than or in addition to that involving immune complexes is operative in the pathogenesis of acute glomerulonephritis. There is circumstantial experimental evidence that an alternate pathway of complement activation and deposition may be operative in acute glomerulonephritis.