Immunologic aspects of tumor induction by ultraviolet radiation.

Chronic treatment of mice with UVR not only induced skin cancer but also produced a systemic change that interfered with host resistance against these tumors. The studies leading to the this conclusion were prompted by the discovery that most tumors induced in C3H mice by chronic UV irradiation were immunologically rejected following transplatation to normal syngeneic recipients. This raised the question of why these tumors were able to grow progressively in the autochthonous host without being destroyed immunologically. We found that after a short course of UV treatment, the UV-irradiated mice lost their ability to reject transplanted UV-irradiated mice lost their ability to reject transplanted UV-induced tumors, even though such transplants were rejected by unirradiated animals. The growth of the transplanted tumors in UV-treated mice resulted from a systemic alteration in the animals that was induced by UV irradiation of the skin.