Different responses of lymphoid cells from tumor-bearing as compared to tumor-immunized mice when sensitized to tumor specific antigens in vitro.

Lymphoid cells from spleen and lymph nodes of BALB/c mice were sensitized in vitro by cocultivation with cells from syngeneic methylcholanthrene-induced sarcomas. The donor mice were either immunized in vivo by tumor transplantation followed by excision ("tumor-excised mice") or were carrying a progressively growing tumor ("tumor-bearing mice"). The cell-mediated immune response of the sensitized cells was compared by a 36-hr microcytotoxicity assay. Lymphoid cells from tumor-excised mice were cytotoxic when tested after 3 days and also after 6 days of sensitization in vitro. Lymphoid cells from tumor-bearing mice were cytotoxic to cells of the tumor borne when tested after 3 days in culture. However, the cytotoxic effect was lost after 6 days of contact with the sensitizing tumor in vitro. Preliminary data suggest that the cultured lymphoid cells of tumor-bearing mice which have lost cytotoxicity, can suppress the reactivity of in vitro sensitized lymphoid cells from tumor-excised mice.