Abrogation of allospecific T lymphocyte responses in swine by ultraviolet light-B irradiation

Immunomodulatory effects of ultraviolet-light B (UV-B) irradiation were tested in pigs, using peripheral blood lymphocytes (PBL), with special emphasis on the generation of cytotoxic T lymphocytes (CTL). Stimulator PBL were irradiated with 300-1100 Joules/m2 (J/m2) of UV-B (experimental group) and cultured for 24 h prior to being placed in mixed lymphocyte culture (MLC) to determine proliferative responses against alloantigens, or placed in bulk culture with allogeneic PBL to determine the induction of CTL. PBL that received 3000 rads gamma irradiation were used as controls. Proliferative alloresponses against gamma irradiated PBL (control group) were high, with stimulation indices (S.I.) ranging from 13.46 to 81.93. The generation of allospecific CTL activity was also high, ranging from 50.78% to 95.40%. In contrast, proliferative responses and generation of allospecific CTL were markedly inhibited (> 49.77%) against the same donor PBL irradiated with > or = 500 J/m2 UV-B. These results demonstrated that ultraviolet light treatment of pig PBL can reduce or prevent allospecific T cell proliferation as well as the generation of specific CTL, similar to results obtained with UV-B irradiation of lymphocytes in rodents.