Roles of CD4+ and CD8+ cells in UVB-induced suppression of splenic alloantigen-presenting function

Whole body ultraviolet light (UV) radiation causes systemic immunosuppression. Splenic antigen-presenting cell (APC) activity is decreased by UV radiation. To determine whether splenic CD4+ or CD8+ cells are involved in the UV-induced depression of splenic alloantigen-presenting function, we investigated the effect of in vivo UV radiation on the splenic stimulatory function in allogeneic mixed lymphocyte reaction in mice after the elimination of CD4+ or CD8+ cells by administering anti-CD8 or anti-CD4 Ab. Ab-treated and non-treated mice were exposed to UVB radiation (2.5 kJ/m2) twice or eight times. Two exposures to UVB radiation significantly suppressed the splenic alloantigen-presenting function of mice previously treated with anti-CD4 Ab, but hardly affected that of anti-CD8 Ab-treated or non-treated mice 2 days after the last radiation. On the other hand, eight exposures to UVB radiation suppressed this function in all mice. FACS analysis revealed that the UV-induced suppression is not associated with a significant decrease in the number of IA+ cell, as stimulator cells. It is suggested that CD4+ cells are somewhat preventive of the UV-induced depression of splenic allo-antigen-presenting function.