Adoptive immunotherapy in BALB-c times DBA-2 Cr F1 mice bearing an immunogenic subline of L1210 leukemia

That treatment with 5 (3,3 dimethyl 1 triazeno) imidazole 4 carboxamide (DIC) in vivo may have induced new antigen(s) on L1210/Ha leukemic cells is supported by the finding of spleen cells in sensitized mice that are specifically immune to the DIC treated L1210/Ha leukemia (L1210/Ha/DIC). An infusion of immune spleen cells 'cured' immunosuppressed BALB/c x DBA/2 Cr F1 mice bearing the L1210/Ha/DIC leukemia and did not exhibit any therapeutic activity in mice bearing 106 cells of the parental L1210/Ha leukemia. Spleen cells that are immune to syngeneic or allogeneic tumor cells did not protect the mice challenged with 106 L1210/Ha/DIC cells. The therapeutic activity of immune spleen cells is increased as the number of cells is increased. The extent of activity was influenced by the size of the tumor inoculum, the time of lymphocyte transfusion following inoculation of viable leukemia, and the amount of sensitizing antigen. Adoptive immunotherapy using L1210/Ha cells with increased immunogenicity resulting from in vivo DIC treatment provides a potential approach for experimental cancer therapy.