Effects of the removal of adherent and phagocytic cells on the spleen cell lymphoproliferative response of tumor-bearing mice.

Cell-mediated immunity was investigated in two BALB/c mouse tumor systems using the lymphoblastogenesis test with phytohemagglutinin as the mitogen. This lymphoproliferative response was quantitated using the Stimulation Index (SI). There was little evidence for suppressor cell activity in cell mixing experiments in which spleen cells from #51 cell-injected mice were mixed with spleen cells from normal mice. Following macrophage removal by Sephadex G-10 columns and carbonyl iron ingestion, there were no significant changes in the SI values for spleen cells from the #51 cell-injected mice. In contrast, spleen cells from mice injected with H238 cells, a herpes virus-transformed cell line, had a significantly lower SI value than that of normal mice. Suppressor cell activity was demonstrated in cell mixing experiments in which spleen cells from H238 cell-injected mice were mixed with normal spleen cells. Removal of adherent cells from spleen cells from H238 cell-injected mice by Sephadex G-10 columns restored the SI value to that of normal mice. An increased SI value was also seen after removal of phagocytic cells by carbonyl iron. These results suggested that cells with the functional properties of macrophages played an important part in the immunosuppression observed in the H238 tumor system. Comparison of the two macrophage depletion methods suggested that another cell population was also involved in the suppressive effect. Results of immunofluorescent techniques with anti-Lyt-1 and anti-Lyt-2 monoclonal antibodies show these cells to be Ly 1-, Ly 2,3+ phenotypes of T-lymphocytes.