Dissociation between cytotoxic activity and delayed hypersensitivity against syngeneic or allogeneic tumor grafts.

Cytotoxicity against tumor-specific antigen and allogeneic antigens in mice was raised by immunization with viable tumor cells in saline, but not by immunization with tumor cells in complete or incomplete Freund's adjuvant. On the other hand, strong delayed hypersensitivity as demonstrated by macrophage migration inhibition was detected in the mice immunized with tumor cells in complete or incomplete Freund's adjuvant in both syngeneic and allogeneic systems. After immunization with viable tumor cells, delayed hypersensitivity was raised to a moderate degree in allogeneic, but not at all in syngeneic mice. Cytotoxicity was retained after a booster with syngeneic tumor cells in complete Freund's adjuvant in the mice which had been immunized with viable tumor cells. Cytotoxicity was raised after a booster with viable syngeneic tumor cells in the mice which had been immunized with tumor cells in complete or incomplete Freund's adjuvant. Thus, the development of cytotoxicity depended entirely on the presence of viable tumor cells as an immunogen. Activation of helper T cells was not found in the syngeneic mice immunized with viable tumor cells or tumor cells in complete or incomplete Freund's adjuvant. In allogeneic mice, the activity was facilitated slightly by immunization with viable tumor cells or tumor cells in complete Fruend's adjuvant but not with tumor cells in incomplete Freund's adjuvant. This sytem may be useful for analytical studies on cellular immunity, since cytotoxicity, delayed hypersensitivity, and helper cell activation can be induced in dissociated forms.