Tumor immunity to murine plasma cell tumors. II. Essential role of T lymphocytes in immune response

Spleen cells, thoracic duct lymphocytes and adherent peritoneal exudate cells from mice immunized to syngeneic plasma cell tumors were capable of transferring specific protective immunity to these tumors. Pre-treatment of these cells with anti-Θ serum or anti-lymphocyte serum, but not with anti-ΘK serum, effectively abolished the ability of lymphoid cells to transfer this immune response. These studies demonstrate that T cells are essential in the adoptive transfer of immunity. Furthermore, immunization of athymic (nude) mice to plasma cell tumors was not achieved. Attempts to activate normal macrophages in vitro with sensitized lymphoid cells were unsuccessful. Admixture of immune lymphoid cells and target tumor cells to unrelated tumor cells did not inhibit the growth of the unrelated tumor cells. It is proposed that the immune response to syngeneic tumor associated antigens of plasma cell tumors not only involves essential sensitization of T lymphocytes, but that activated cytotoxic T lymphocytes are directly responsible for inhibiting target tumor growth.