The fate of subepithelial deposits in acute poststreptococcal glomerulonephritis.

The resolution of subepithelial deposits was studied by electron microscopy in 17 biopsies from five patients (mean follow-up 2.8 years) with clinically and histologically resolving acute poststreptococcal glomerulonephritis. The electron-dense subepithelial deposits were present in biopsies obtained 45 days or less after onset. By 30 to 45 days after onset, the dense deposits had decreased in number, and there appeared electron-lucent subepithelial deposits, areas suggestive of foci where deposits had recently been resorbed, as well as lucent deposits covered by a layer of lamina densa-like material (intramembranous deposits). These developments indicate that some of the subepithelial dense deposits had been completely resolved, that some were resolving, and that some had been transformed into intramembranous deposits. The resolution appeared to take place both from a continuous loss of electron microscopically invisible components of deposited material and through a removal of larger fragments of the deposits by epithelial vesicles. The intramembranous deposits persisted in all but one patient during the entire time of follow-up. The findings indicate that membranous changes--although mild and segmental--develop regularly in acute poststreptococcal glomerulonephritis and that they constitute a normal phase in the resolution of the subepithelial deposits. The absence of progressive membranous changes in these patients can probably be attributed to the short time during which immune complexes are deposited in the glomeruli.