Cellular and humoral immune responses of mice during immunological enhancement of an allogeneic tumor.

Spleen cells obtained from C57BL/Ks (Ks, H-2d) mice carrying passively enhanced Sarcoma I (Sa I, H-2a) tumors were tested for alloantibody formation, lymphocyte blastogenesis, antibody-dependent cellular cytotoxicity, and cell to cell cytotoxicity. Assays were usually performed approximately 6 weeks after tumor inoculation. The results of these assays indicate that spleen cells from tumor-bearing mice are actively synthesizing alloantibody, but have a depressed blastogenic response to phytohemagglutinin and allogeneneic cells, and manifest no detectable cytotoxic activity in 51Cr release assays for antibody-dependent or cell to cell cytotoxicity. The absence of cell to cell cytotoxicity was specific and could not be attributed to the activity of suppressor cells acting in vitro, or to immunoglobulin secreted during the in vitro assay. These results indicate that Ks mice carrying immunologically enhanced Sa I tumors have a strong humoral response but a defective cellular response to the alloantigens of their tumors. These results are compatible with a mechanism of immunological enhancement which involves suppression of the development of the cellular immune response throughout the course of tumor growth.