A systemic effect of ultraviolet irradiation and its relationship to tumor immunity.

Chronic irradiation of mice with UV light produces a systemic alteration that is immunologic in nature and may be due to the presence of specific suppressor lymphoid cells. The immunologic aspect of this systemic alteration was demonstrated by cell transfer experiments. Lymphoid cells from UV-treated donors were unable to confer tumor resistance to lethally X-irradiated and neonatal liver reconstituted recipients, whereas recipients given lymphoid cells from normal donors were resistant to a challenge with a syngeneic UV-induced tumor. Therefore, lymphoid cells from normal donors could mediate tumor rejection, but lymphoid cell from UV-irradiated donors could not. Furthermore, lymphoid cells from UV-treated donors suppressed the ability of lymphoid cells from normal donors to mediate syngeneic tumor rejection when mixed 1:1 before transfer into lethally X-irradiated recipients. This suppression was specific since all recipients recipients resisted an allogeneic UV-induced tumor challenge. Serum transfer experiments failed to demonstrate any inactivating or suppressive substances in the serum of UV-treated animals. The findings suggested that UV-treated mice failed to reject UV-induced tumors because UV irradiation induced specific suppressor lymphoid cells that prevented the development of an immune respons against these tumor antigens.