A normal female donor (H9) is described, whose cells generate strong cytotoxicity against a human minor histocompatibility antigen in vitro. These cytotoxic T lymphocytes are generated after secondary restimulation with cells from an HLA-A, -B, -C, and -DR-matched donor and are HLA restricted (HLA-B7). No other donor could be identified whose cells responded to this antigen. The two children of...