Alterations of both responder T cells and stimulator non-T cells are responsible for abnormal mixed lymphocyte reaction in aged humans

Summary The autologous and allogeneic mixed lymphocyte reactions of 15 young and 15 aged human adults were compared. Both autologous and allogeneic mixed lymphocyte reactions were significantly reduced in the aged group. T cells from aged adults displayed a reduced proliferative response to non-T cells of either aged or young adults. T cells from young adults also showed a reduced proliferative response to non-T cells from aged adults. Sera from aged adults, showing depression of autologous and allogeneic mixed lymphocyte reaction, did not exert any inhibitory effect on the autologous and allogeneic mixed reaction of lymphocytes from young donors. These data suggest that depression of mixed lymphocyte reaction in aged humans probably reflects intrinsic abnormalities of both responder T cells and stimulatory non-T cells. This work was supported by a grant from theConsiglio Nazionale delle Ricerche (CNR), Roma, Italy ‘Progetto Finalizzato Medicina Preventiva, Sottoprogetto Meccanissmi di Invecchiamento’.