Macrophages and resistance to tumors

Summary Delayed-type hypersensitivity (DTH) reactions in mouse feet were depressed by irradiation and by treatment with carrageenan, niridazole, or reserpine. Specific resistance of immunized mice to footpad challenge with a syngeneic methylcholanthrene-induced fibrosarcoma was also depressed by irradiation, carrageenan, niridazole, and reserpine. Growth of the tumor in the feet of normal mice was unaffected by irradiation or niridazole. It could be inhibited or enhanced by carrageenan treatment, depending on the dose of tumor cells injected. Paradoxically, treatment with reserpine inhibited tumor growth in the feet of nonimmune mice. It is suggested that: (a) specific, acquired resistance to this tumor is strongly akin to DTH; (b) mice offer some natural resistance to this tumor; (c) the establishment of an isograft of this tumor may depend on the occurrence of some degree of inflammation.This work was carried out pursuant to Research Contract NO1-CB-63973 with the U.S. National Cancer Institute. It was supported in part by a grant from the Australian National Health and Medical Research Council