Proteinuria induced by anti-dipeptidyl peptidase IV (gp108); role of circulating and glomerular antigen.

Massive proteinuria is induced in rats by administration of rabbit antibody to dipeptidyl peptidase IV (DPPIV, gp108), a glycoprotein present on glomerular cell membranes and in serum. This study was undertaken to know which antigen, glomerular or serum DPPIV, is responsible for forming immune complex in glomeruli and development of proteinuria. An i.p. injection of the antibody resulted in a rapid decrease of serum DPPIV and a gradual increase of rabbit IgG deposited along glomerular capillary wall for 4-8 h. Abnormal proteinuria appeared within 8 h, peaked on day 2 (> 200 mg/24 h) and then declined. An increase of urinary protein and glomerular deposition of IgG also occurred, when the antibody was injected into serum DPPIV-depleted rats that had received preinjection of anti-DPPIV antibody. These results suggest that proteinuria is induced by direct binding of anti-DPPIV antibody to the membrane antigen of glomerular cells.