Absence of H-2 restriction in primary and secondary mixed-lymphocyte reactions to strong M1s determinants.

Negative and positive selection procedures were used to establish whether the strong proliferative response of T cells to M1sa determinants is H-2 restricted. After negative selection of H-2 determinants in vivo, it was shown that T cells give high primary mixed lymphocyte reactions in vitro to M1sa determinants presented on H-2-incompatible stimulator cells. Other studies demonstrated that (a) negative selection of T cells to M1sa determinants on H-2-incompatible cells removed T cells with specificity for M1sa-bearing H-2-compatible cells, and (b) T cells primed in vitro or in vivo to M1sa determinants on H-2-compatible cells gave high secondary responses to M1sa determinants presented either on H-2-compatible or H-2-incompatible stimulator cells. From these data we conclude that T cells recognize M1sa determinants per se rather than an association of M1sa plus self or allo-H-2 determinants.