Objective To investigate the mechanism of immunointerstitial nephritis. Methods BN rat model was obtained with bovine tubular base membrane (bTBM). Monoclonal antibodies, immunohistochemical ABC method and indirect im-munofluorescent technique were used to detect the inflammatory cells and ICAM-1. Results 9 days after immunization with bTBM, inflammatory cells infiltration and a strong ICAM-1 expression were found in the intersitium, associated with the pathological degree. Conclusion Cellular immunity mediated by ICAM-1 may play an important role in the development of immunointerstitial nephritis. Macrophage is a leading factor among various inflammatory cells. Fluid immunity can not be excluded.