Cooperation across the histocompatibility barrier: H2d T cells primed to antigen in an H-2d environment can cooperate with H-2k B cells.

H-2d spleen cells derived from either tetraparental or semiallogeneic radiation bone marrow chimeras can be primed to antigen within H-2d recipients to generate helper T cells capable of cooperating in a secondary response with equal efficiency with H-2d or H-2k B cells. Thus it would seem that the cooperative act between T and B cells does not require that the T cell interacts with its target B cells by either cell interaction genes or via an altered self mechanism involving both antigen and the target B-cell I-region products. This does not preclude a requirement for associative recognition or altered self in the interaction of helper T cells with accessory cells.