Immune status of autochthonous and adoptively protected mice toward spontaneous and chemically induced tumors.

mice were used. Autografts of either of these tumors grew better than isografts into normal mice. Attempts to transfer this conditioned status from primary hosts bearing MCA tumors to syngeneic recipients were unsuccessful. Neither with lymphoid cells nor with serum could we induce such state in recipient mice in which latency and growth of primary and transplanted, MCA-induced tumors was measured. On the other hand, attempts to transfer specific immunity from actively immunized mice to syngeneic recipients were success ful. When mice bearing primary or transplanted tumors were lethally irradiated and repopulated with lymphoid cells from normal or tumor-immunized donors, tumor growth was markedly inhibited. This treatment was effective for MCAinduced sarcomas both in inbred and random-bred mice, but not for spontaneous mammary carcinomas. Procedures in volving repopulation of tumor-bearing mice with lymphoid cells from normal or immunized mice seem to correct a decreased level of reactivity of the animals toward their own tumors.