Differences in putative minor histocompatibility but not IgH genes can prevent T-cell priming and T--B co-operation in the response of mice to sheep erythrocytes.

A positive association has been observed in Igh allotype "congenic' mice between skin graft rejection and a block to effective T--B co-operation in the development of both IgM and IgG responses to sheep erythrocytes. Mismatch of Igh alone is insufficient for such a block to become apparent since pairs of Igh-allotype congenic strains of mice which reciprocally accept skin grafts for at least 5 weeks, show successful positive co-operation (help) between T and B cells. The observed block is manifest both during the education (priming) of T cells in irradiated (first stage) recipients and during co-operation between primed T cells and unprimed B cells in second stage irradiated "syngeneic' recipients.