Effect of a novel immunosuppressant, FK 506, on autoimmune glomerulonephritis in brown Norway rats

Mercuric-chloride (HgCl2) induces a lymphoproliferative disorder and autoim mune glomerulonephritis in Brown Norway rats. The effects of a new immunosu ppressant FK 506 on this model of glomerulonephritis were studied. Brown No rway rats were treated with HgCl2 according to a standard protocol (HgCl2 1 mg/kg s.c. 3 times/ week). Rats developed proteinuria at day 7, which reac hed a plateau level at day 14, On day 14, renal histology showed prominent mesangial cellular proliferation and the expansion of mesangial matrix. Ele ctron microscopic study showed the effacement of visceral epithelial foot p rocesses and the microvillous transformation of the visceral epithelium. Im munofluorescence study showed a strong linear staining for IgG and the adhe sion molecule ICAM-1 in all glomeruli. Coadministration of FK 506 (1 mg/kg s.c, daily) prevented the appearance of proteinuria at day 14 (621.4 +/- 30 .5 vs. 2.2 +/- 2.7 mg/day) and the morphological lesions. These findings su ggest that FK 506 could be useful for the therapy of certain types of human glomerulonephritis.