Human blood lymphocytes from donors sensitized by skin grafting were inhibited in their migration from capillary tubes by antigens from the skin graft donor. Lymphocytes from non-sensitized human subjects showed no or a very slight inhibition with similar antigens. When confronted with cell antigens from individuals which did not possess any of the detectable HL-A specificities of the donor, the sensitized lymphocytes exhibited a marginal degree of inhibition (15·3±2·0%). The degree of migration inhibition increased to an average of 24·9±2·0% when the sensitized lymphocytes were confronted with one HL-A antigen similar to that of the immunizing donor. When there were two and three HL-A antigens involved, inhibition increased to 29·4±4·1% and 37·8±4·6%, respectively.
Lymphocytes from two patients who had received kidney allografts exhibited a small but significant degree of inhibition when tested against cells sharing one antigen with the allograft. Lymphocytes from these patients maintained strong reactivity to tubercle bacilli and streptococcal antigens despite prolonged immunosuppressive therapy.