The deleterious effects of ultraviolet B radiation (UVB) on the antigen-presenting function of human epidermal Langerhans cells (LC) were studied by using the in vitro primary and secondary T-cell proliferative responses to the trinitrophenyl hapten (TNP) modified autologous LC. Increasing doses of UVB radiation (100-200 J/m(2)) induced a dose dependent inhibition of the primary and secondary TNP-specific T cell response. However, this decreased T-cell proliferative response after UVB radiation, was strongly enhanced when freshly isolated LC, as compared with cultured LC, were used as antigen-presenting cells (APC), suggesting an impaired development of LC accessory function. Moreover, the exogenous addition of IL1beta, TNFalpha, IL10 or their specific monoclonal antibodies neither modified nor reversed the immunosuppressive effect of UVB radiation. Even if the low doses of UVB radiation (100 and 200 J/m(2)) seemed to slightly affect HLA-DR synthesis, the antigen-presenting function of human LC cannot be related to the decreased expression of these molecules but might be associated with an impaired development of accessory molecules such as a downregulation of B7-2 antigen.