Tumor-specific resistance in mice detected by inhibition of macrophage migration.

Resistance against a methylcholanthrene-induced fibro sarcoma and a spontaneous mammary carcinoma in syngeneic C3Hf mice was demonstrated in vitro by specific inhibition by tumor antigens of peritoneal cell emigration from capillary tubes. The soluble antigens of the two tumors did not cross-react, but strong nonspecific inhibition of migration was observed when tumor cells or particulate matter was present in the reaction mixture. The degree of inhibition of macrophage migration was related to the stage of the development of antitumor immunity in the peritoneal cell donor. Depression of fully developed immunity by excess tumor antigen (desensitization) was not reflected in the motility of the peritoneal cells of the host in the presence of tumor antigen. Host resistance could also be detected by a simple but nonquantitative procedure in which the effect of tumor antigens on macrophage spreading was observed in ordinary culture dish or microtest plate cultures of peritoneal exÃodate cells.