Negative allogeneic effects in vitro. II. Mapping of histocompatibility differences leading to allosuppression

When splenic T cells from normal mice recognize alloantigens on primed spleen cells there is a dramatic suppression of the secondary antihapten PFC response of the latter cells. From studies using intra-MHC recombinants it appears that differences at K or D alone can elicit allosuppression. There is sometimes suppression to differences in the I region. Even small differences in H-2K, as seen in the H-2b mutants, are sufficient to lead to such negative allogeneic effects. Thus, as far as has been determined, the specificity of allosuppresive T cells is indistinguishable from that of cytotoxic effector cells. Negative allogeneic effects and positive allogeneic effects different in the degree to which they influenced the primary and secondary responses. In our experiments no evidence for positive allogeneic effects was seen in the secondary response to TNP-carrier even with cells differing at the I region only. In contrast the primary response to SRBC was much enhanced by allogeneic cells and little suppression of that response was seen. It is suggested that the allosuppression is distinct from cytotoxicity and may be a profitable model for the study of suppressor T cells.