Modification of immunological potential by ultraviolet radiation. II. Generation of suppressor cells in short-term UV-irradiated mice.

When normal mice are exposed for short periods to ultraviolet light (UV), they support the progressive growth of transplanted syngeneic UV-induced tumors. Normal nonirradiated mice almost always reject these tumor implants. The UV-mediated suppression of the antitumor response can be adoptively transferred to normal syngeneic mice with lymphoid cells derived from short-term UV-irradiated donors. Transfer of the suppressive effect is dosage dependent and also appears to require the presence of viable T lymphocytes. Suppressive activity was observed in both the spleen and thymus of UV-irradiated donors. In the preceding paper we have established that UV irradiation does not cause a general depression of testable immune functions. Collectively these data suggest that short-term UV irradiation of mice leads to an increase in suppressor cell activity, thereby causing an inhibition in the host's ability to respond to an antigenic UV-induced tumor. The possible role of this phenomenon in the mechanism of UV carcinogenesis is discussed.