Nature of the antigenic complex recognized by T lymphocytes: specific sensitization by antigens associated with allogeneic macrophages.

Alloreactive guinea pig thymus-derived (T) cells generated in vitro were rendered unresponsive to allogeneic macrophages by treatment with bromodeoxyuridine and light. The remaining T cells were subsequently primed and rechallenged in tissue culture with trinitrophenyl (Tnp)-modified syngeneic or allogeneic macrophages. By this procedure we found that the remaining T cells primed with Tnp-modified allogeneic macrophages could be restimulated only with Tnp-modified allogeneic, not syngeneic, macrophages. Similarily, if the remaining T cells were primed with Tnp-modified syngeneic macrophages, they could be restimulated only by Tnp-modified syngeneic, and not by allogeneic, macrophages. In contrast, no T cell sensitization with Tnp-modified syngeneic or allogeneic macrophages occurred if the alloreactive T cells were treated with light alone, suggesting that an uninhibited mixed leukocyte reaction causes nonspecific suppression of antigen-specific T cell priming. These results indicate that the genetic restriction of T cell-macrophage interactions is imposed by the type of macrophage used for initial sensitization rather than by a requirement for self-recognition through cellular interaction structures.