Rabbit antibodies specific for the idiotype (Id) of autoantibodies to tubular basement membrane (TBM) eluted from kidneys of Brown Norway rats with tubulointerstitial nephritis (TIN) were used to analyze the immune response to TBM antigens at the humoral and cellular levels. These antibodies appeared to recognize Id determinants associated with the antigen combining site on the anti-TBM Id as well as on splenic lymphocytes. However, efforts to detect Id-positive cells in the interstitial infiltrates of kidneys with TIN failed. In contrast, in vivo injection of anti-Id serum before immunization with TBM resulted in a) significant selective suppression of antibodies to the autologous collagenase-solubilized TBM moiety but not to antigenic determinants of the intact TBM nor to those of heterologous TBM, and b) a corresponding decrease of TIN. These results suggest that anti-Id antibodies of this type can be useful as a probe for further dissecting the pathogenetic mechanisms underlying these complex autoimmune responses.