Further characterization of immunological unresponsiveness induced in mice by ultraviolet radiation. Growth and induction of nonultraviolet-induced tumors in ultraviolet-irradiated mice.

Ultraviolet (UV)-irradiated mice were compared with unirradiated mice for their susceptibility to primary and transplanted tumors etiologically unrelated to UV radiation. Although UV-irradiated mice are unable to reject transplants of highly antigenic syngeneic tumors induced by UV light, the growth of syngeneic, non-UV-induced tumors generally was not accelerated in these animals. Furthermore, UV-irradiated mice were no more susceptible to the induction of primary leukemias, mammary tumors, or sarcomas than were unirradiated animals. Tests of immune responses to weak transplantation antigens showed that UV-irradiated mice rejected H-Y-incompatible skin grafts as vigorously as did normal animals, and that the primary in vitro cytotoxic responses of spleen cells from UV-irradiated mice to trinitrophenyl (TNP)-modified syngeneic cells and to Hh antigens were unaffected. We conclude that the susceptibility of UV-irradiated mice to challenge with UV-induced tumors represents a selective unresponsiveness, and that it is not attributable to a generalized deficiency in the immune response to tumor-specific antigens or to weak transplantation antigens.