Rejection of syngeneic tumor cells by the interaction of Lyt-1+ T lymphocytes and macrophages.

A high degree of cytostatic activity was detected in peritoneal exudate cells (PEC) from BALB/c mice immunized with mitomycin C-treated Meth A cells (MMC-MA) given intraperitoneally (i.p.) While this cytostatic activity was not detected in a nonadherent fraction of immune PEC, the addition of starch-induced PEC to the nonadherent immune cells led to a cytostatic activity. Treatment of these nonadherent cells with anti-Thy-1 X 2 or anti-Lyt-1 X 2 antibody plus complement abolished the restored cytostatic activity. Normal PEC were also rendered cytostatic after addition of the culture supernate of a nonadherent fraction of immune PEC mixed with MMC-MA. These findings suggest that macrophages are rendered cytostatic by immunization with tumor antigen and that these cytostatic macrophages evolve after activation of sensitized Lyt-1 positive T lymphocytes.