Determinants of glomerular localization of subepithelial immune deposits: effects of altered antigen to antibody ratio, steroids, vasoactive amine antagonists, and aminonucleoside of puromycin on passive Heymann nephritis in rats

Abstract

The role of circulating immune complex deposition versus in situ complex formation in membranous nephropathy is controversial. Passive Heymann nephritis in rats resembles membranous nephropathy in man and was induced by injection of sheep antibody to rat proximal tubular epithelial cell brush border antigen (anti-Fx1A). Minutes after injection of 1 ml. of anti-Fx1A, subepithelial immune deposits were seen by immunofluorescence and electron microscopy, and proteinuria appeared within 5 days. The effects of alterations in the dose of administered antibody, corticosteroid therapy, and vasoactive amine blockade on the development of subepithelial deposits and consequent proteinura were studied. Variation of the dose of anti-Fx1A from 0.25 ml. to 1 ml. resulted in a progressive increase in the size and number of glomerular capillary wall deposits, but no alterations in their distribution. Only those rats which received 1 ml. became proteinuric within 5 days. Corticosteroid therapy and vasoactive amine blockade, begun 24 hours prior to the induction of passive Heymann nephritis and continued until termination of the study 5 days later, had no effect on the amount or site of immune complex formation, nor on the extent of proteinuria as compared to untreated controls. In contrast, in rats with unilateral proteinuria produced by the selective perfusion of one kidney with aminonucleoside of puromycin 7 days prior to the induction of passive Heymann nephritis, there was a marked reduction of subepithelial deposits in the perfused kidney as compared to the nonperfused contralateral kidney. In this model of membranous nephropathy, systemic factors play little role in the development of subepithelial deposits, whereas local factors are critical. These findings are consistent with the hypothesis that subepithelial immune deposits form locally.