Incompatibility of human minor histocompatibility (hmH) antigens can induce rejection of grafts in organ transplantation and graft-versus-host reactions in bone marrow transplantation. In spite of their importance in clinical transplantation, hmH antigens are not well studied. Previous studies have demonstrated the expression of hmH antigens on T and B cells, hematopoietic progenitor cells and keratinocytes. We have for the first time demonstrated the expression of hmH antigens on cultured kidney cells using HLA-B35-restricted, hmH antigen-specific cytotoxic T lymphocyte (CTL) clones, which were previously established from a patient who rejected two kidneys from HLA-identical sisters. The CTL clones could not kill cultured kidney cells. Since cultured kidney cells expressed very low levels of HLA class I antigens it was thought that their failure to be killed by the CTL clones was due to lack of expression of HLA-B35 antigens. After induction of class I antigens on cultured kidney cells by interferon-gamma (IFN-gamma), the IFN-gamma-treated cultured kidney cells were killed by the CTL clones. Furthermore, we isolated hmH antigens as peptides from cultured kidney cells after treatment with IFN-gamma. These results indicate that cultured kidney cells express hmH antigens when HLA class I antigen is induced by IFN-gamma and hmH antigens on cultured kidney cells are recognized by T cells as peptides presented by HLA-B35 molecules.