Immunization of rabbits with physicochemically altered homologous or even autologous IgG induces formation of antibodies combining with IgG of rabbit and of foreign species. Cardiac but not renal lesions were reported in such animals. This study examined the nephritogenic potential of the immune response to cationized or heat-aggregated homologous IgG of b9 or b4 allotype in rabbits of the b4 allotype. Rabbits injected with either b9 or b4 cationized IgG produced antibodies reactive with rabbit and human IgG and with histones; they also developed abnormal glomerular deposits of IgG b4 and C3 corresponding to alterations of the glomerular basement membranes (GBM). Rabbits injected with either b9 or b4 aggregated IgG developed antibodies reactive with rabbit and human IgG and abnormal glomerular deposits of IgG b4 and C3 in the GBM and in the mesangium with subendothelial and mesangial electron-dense deposits. Some rabbits in both groups had proliferative and exudative glomerulonephritis and proteinuria. The results showed that immunization of rabbits with physicochemically altered homologous IgG induces an immune response to rabbit and human IgG and to histones as well as glomerular deposits of autologous IgG and C3 and other glomerular lesions.