Studies into the transplantation biology of ultraviolet light-induced tumors

The majority of skin tumors induced in mice by ultraviolet (UV) light are rejected when implanted into normal syngeneic recipients. Subcarcinogenic levels of UV light exposure render the normally resistant mice susceptible to tumor challenge. The immunoregulatory effect of UV light appears to be additive, since the growth rate of a tumor transplant is dependent upon the length of UV exposure administered prior to implantation. This suppressive influence does not appear to be directly mediated by the UV light, because the amputation of UV-irradiated tail skin allows for a retention of tumor resistance in otherwise tumor-susceptible hosts. UV-irradiated mice could also be immunized against UV tumors, which suggests that immune recognition of tumor-specific transplantation antigens has not been inhibited. The ability of UV exposure to alter normal immunological reactivity to UV-induced tumors is possibly an integral factor in the mechanism underlying UV carcinogenesis.