Transfer of tubular basement membrane (TBM)-primed thymocytes from BALB/c mice that had been immunized with allogeneic TBM antigen without adjuvant prevented the development of interstitial nephritis (IN) in recipient BALB/c mice that had been immunized with TBM antigen with complete Freund's adjuvant (CFA) to produce IN. TBM antigen was prepared from TBM of normal ddY mice (ddY TBM antigen). BALB/c mice were highly susceptible to IN and showed a high immune response to TBM antigen when they were immunized with TBM antigen in CFA. Development of IN in high responder BALB/c mice was clearly suppressed by transfer with ddY TBM-thymocytes. The anti-TBM antibody response and the proliferative response of splenic T cells to TBM antigen were also depressed by the transfer. The cell extract of ddY TBM-thymocytes had also suppressive activity on the development of IN and on the immune response to TBM antigen. This simple system without any adjuvant for inducing the thymocytes, which has strong suppressive activity on the development of IN and on the immune response to TBM antigen, may allow us to analyse the role of suppressor T cells in negative regulation of IN.