Nonspecific resistance to tumor allograft.

The effects of an increased volume of reticulohistiocyte system and macrophage activation in the recipient after treatment with BCG and Zymosan on the course of antitumor concomitant allograft-immunity reaction were studied. The results were verified on animals affected with immunosuppression due to whole body irradiation. A factor of essential significance for resistance to tumor allograft is an increase of the total number of small lymphocytes supplied by the transplantation of syngeneic spleen cells. A substantially lower efficiency was shown by prophylactic administration of BCG and Zymosan. Transplantation of macrophages syngeneic to the host failed to affect the latter's resistance to subsequent tumor allograft. The irradiated host's reactivity was regenerated with a suspesion of spleen cells of purified small lymphocytes, but transplantation of syngeneic macrophages remained without effect.