Passive Heymann nephritis induced by rabbit antiserum to membrane antigens isolated from rat visceral yolk-sac microvilli

Passive Heymann nephritis (PHN) is an animal model of immune-complex-induced renal dis- ease resembling human membranous glomerulonephri- tis. It was induced in rats by injecting rabbit antiserum directed against glycoprotein antigens isolated from rat embryonic visceral yolk-sac microvilli (VYS-MV). The glycoprotein antigens were isolated by extracting the VYS-MV with detergent Nonidet P-40 followed by gel filtration in Sephacryl S-300 and finally by lectin affin- ity chromatography with Ricinus communis agglutinin I. In uitro immunofluorescent localization studies dem- onstrated that the nephritogenic antibodies were local- ized along the apical region of the visceral yolk-sac endodermal cells and the brush border of the proximal tubular cells of the kidney. Rats injected with a single dose of the antiserum manifested proteinuria. Indirect immunofluorescent studies showed that the injected rabbit IgG was localized in uiuo along the capillary walls of the glomerulus in a granular fashion. Electron microscopic examination of the same kidney glomeruli revealed numerous electron-dense deposits along the lamina rara externa of the glomerular basement mem- brane. Fusion of the epithelial foot processes was also present. These findings represent the typical immuno- pathological characteristics of Heymann nephritis. Furthermore, with the aid of Ouchterlony analysis, the antiserum against the isolated VYS antigens exhibited an immunoprecipitin band which was in common with that formed by the antiserum against the homogeneous nephritogenic antigen (gp330) of renal brush border or- igin. Thus, the nephritogenic antigens which have been found to be associated with the brush border of the renal proximal tubules may also be present or cross- reacted in the microvilli of the rat embryonic visceral yolk-sac.