Tumor Specific Immunity to Mouse Melanoma In Vitro 1

Summary

An in vitro assay that measures the ability of mouse spleen cells to inhibit DNA synthesis (IDS) of syngeneic melanoma tumor cells was used in the evaluation of tumor immunity. The IDS assay was used in the measurement of both specific immunity mediated by spleen cells from tumor-bearing mice and nonspecific tumor cell growth inhibition mediated by normal spleen cells. Specific IDS was first demonstrable 2 weeks after injection of 10⁶ B-16 tumor cells sub-cutaneously and persisted during advanced stages of disease. Changes in spleen cell IDS activity were correlated with changing mitogen reactivity during the course of tumor growth. A portion of the spleen cells mediating nonspecific IDS was removed by nylon wool filtration, but the effector cells exhibiting specific immunity were not removed by this procedure. Immune spleen cells did not need to synthesize DNA or divide to inhibit tumor cell DNA synthesis.