Suppression of the immune response to allogeneic histocompatibility antigens by a single exposure to ultraviolet radiation.

Sensitization of C3H mice with allogeneic BALB/c spleen cells after a single exposure to ultraviolet (UV) radiation renders the mice incapable of generating an effective delayed-type hypersensitivity (DTH) response against BALB/c cells. In addition to the depressed DTH response, spleen cells from the UV-irradiated mice are unable to proliferate to alloantigen in a one-way mixed lymphocyte reaction (MLR). This inability to respond to alloantigen appears to be mediated by suppressor T cells, in that nylon-wool-nonadherent cells from the spleens of the UV-irradiated mice could suppress the MLR response of normal spleen cells to allogeneic spleen cells. In addition, the amount of interleukin-2 (IL-2) in the supernatants of the suppressed MLR cultures was also decreased. In all cases, the observed suppression was specific for the antigen used to sensitize the UV-irradiated animals. These data suggest that UV radiation can be used as an agent to induce a selective suppression of immune reactivity against allogeneic cells.