Prediction of graft versus host disease by frequency analysis of cytotoxic T cells after unrelated donor bone marrow transplantation.

HLA "matched" unrelated donor bone marrow transplants are associated with an increased incidence and severity of graft-versus-host disease in comparison with HLA-identical sibling transplants. This is presumably due to HLA and non-HLA histocompatibility differences between donor and recipient. Using a limiting dilution assay, we have previously demonstrated a relationship between cytotoxic T lymphocyte precursor frequency and HLA disparity. In this study we have compared CTL-p frequencies with clinical GVHD, and demonstrate for the first time a significant correlation (P less than 0.005) between high CTL precursor frequency prior to BMT and severity of acute GVHD after HLA A, B, DR "matched" unrelated donor transplants using T cell depleted marrow. This assay system may be of value in the final selection of HLA "matched" unrelated donors for BMT.