Antigenicity and nephritogenicity of trypsin-digested and purified renal tubular basement membrane (TBM) antigen from the Lewis (LEW) strain rat was investigated. Immune reactions to TBM antigen in BN, LEW and F1 hybrid rats were also studied using syngeneic and allogeneic injection systems to evaluate the possible antigenic differences between the two strain rat antigens. Immunization with LEW TBM antigen led to antibody formation against the antigen and induction of tubulointerstitial nephritis (TIN) in BN rats, BALB/c mice with immune deposits and XIII guinea pigs without deposits along the TBM. Circulating anti-LEW TBM antibody could be detected by immunodiffusion and immunofluorescence methods. These data indicates that the LEW rat has nephritogenic antigen on the TBM, though the lack of the antigen in the LEW TBM has been repeatedly reported based on the two lines of results, the failure to detect the TBM by the immunofluorescent technique and to induce TIN in the LEW rat. In comparison of LEW TBM antigen with BN TBM antigen in syngeneic and allogeneic systems, the BN rat was a higher responder to both TBM antigens than the LEW rat. Furthermore, immune response to BN TBM antigen was higher than that to LEW TBM antigen in BN rats. It was indicated that the host immune reaction to TBM antigen along with antigenicity and nephritogenicity of the antigen plays a significant part in induction of TIN.
