Abstract
Effector cells for cell-mediated lysis (CML) were generated by in vitro culture of lymphocytes from selected donors with X-irradiated cells from unrelated subjects who were HLA-D homozygous and matched to the responders for the antigens of the HLA-A and HLA-B regions. By using chromium labeled monocytes as target cells, cytotoxicity was found to correlate with presence of HLA-D region antigens matching those of the stimulating cells. Such CML reactions apparently directed at products of HLA-D, were inhibited by addition of unlabeled monocytes or B lymphocytes. These unlabeled cells had to be matched for HLA-D with the stimulating cells used to generate the effector populations. The results suggested that products of HLA-D, perhaps the DR antigens, were recognized by cytotoxic lymphocytes.