Ultraviolet radiation inhibits alloantigen presentation by epidermal cells: partial reversal by the soluble epidermal cell product, epidermal cell-derived thymocyte-activating factor (ETAF).

It has been postulated that ultraviolet radiation (UVR) alters antigen presentation by macrophages. This is thought to be due, in part, to inhibition of macrophage-derived interleukin 1 (IL-1), which is a hormone-like factor with immunoregulatory functions. Conventional stimulator cells for antigen presentation are macrophages; however, other cell types such as epidermal Langerhans cells are capable of antigen presentation. Keratinocytes also play a role in the immune system by providing a factor with IL-1-like activity, termed Epidermal cell-derived Thymocyte-Activating Factor (ETAF). The purpose of this study was to determine whether UVR affects alloantigen presentation by epidermal cells and if so, whether the UV-induced change is due to UVR alteration in ETAF activity. Epidermal cells from UV-treated BALB/c mice (UV-EC) or from non-UV-treated mice (EC) were x-irradiated and then cocultured for 5 days with allogeneic T cells from C57Bl/6 mice. UV-EC caused less T-cell stimulation than did EC from non-UV-treated animals. When chromatography purified fractions of ETAF were added to cultured UV-EC, partial restoration of T-cell stimulation was seen. These results suggest that this UV-induced defect in alloantigen presentation is due, in part, to decreased ETAF activity.