Cytostatic effect of macrophages from non-immunised mice on mastocytoma P-815 cells in vitro.

Peritoneal macrophages from non-immunised C57/bl, C3H, and DBA/2 mice were examined for their capability of inhibiting the growth of mastocytoma P-815 cells in vitro. The rate of tumour cell growth was measured by the uptake of 125IUDR into the DNA of the tumor cells. Sodium thioglycollate-induced macrophages as well as resident macrophages inhibited the growth of allogeneic tumor cells distinctly, when incubated for 48 h. The effect depended on the effector to target cell ratio. Tumor cell growth was still reduced at a ratio of one macrophage to one tumor cell. A decrease in the proliferative activity of mastocytoma cells was observed in the presence of non-stimulated and non-immune macrophages from DBA/2 mice. This decrease in target cell proliferation, however, occurred more slowly.