[Macrophages and the functional differentiation of thymocytes (a review of the authors' own data)]

Cellular, humoral, and genetic mechanisms of induction of T-effectors of the transplant vs. host reaction (THR) have been studied in two-cell culture of phagocyte mononuclears and thymocytes. A direct physical contact and similarity of H-2K locus of major histocompatibility complex between the cooperating cells in culture is required for successful induction of T-effectors of THR. Contact interaction of macrophages with thymocytes leads to accumulation of a 67 KDa humoral factor in the culture medium. Incubation of intact thymocytes with this factor leads to functional transformation of immature thymocytes into corresponding effector cells. Similarity of H-2K locus of the factor producers and intact lymphocytes is also required for successful humoral induction of the T-effectors. The surface H-2K antigen is able to induce formation of THR t-effectors from non-reactive thymocytes. The H2-K-specific mediator, affinity-isolated from the supernatant of the macrophage-thymocyte culture can also cause this induction.