IN-VITRO EFFECTS OF ULTRAVIOLET-B RADIATION ON HUMAN LANGERHANS CELL ANTIGEN-PRESENTING FUNCTION

The effects of ultraviolet B radiation (UVB) on the immune function of human epidermal Langerhans cells (LC) were studied by using the mixed epidermal cell-lymphocyte reaction (MELR), Exposure of both enriched LC suspensions (eLC, 8-20% LC) and purified LC suspensions (pLC, 70-90 % LC) to increasing doses of UVB radiation (25 to 200 J/m(2)) decrease d the proliferative T cell response in a very similar dose-dependent w ay, suggesting that keratinocytes did not play a major role in the UVB -induced inhibition of MELR, Supernatants from irradiated cultured eLC or pLC failed to inhibit T cell proliferation induced by untreated pL C, Furthermore, addition of irradiated eLC to untreated pLC did not af fect the allogeneic T cell response. Taken together, these results pro vide evidence that in vitro UVB-induced immunosuppression was not medi ated by inhibitory soluble factors that could affect either LC allosti mulatory property or T cell proliferative response, UVB irradiation of human LC inhibited the capacity of these cells to induce CD4(+) as we ll as CD8(+) T cell proliferation, UVB-irradiated LC also induced a de creased T cell response to recall antigen or mitogen, Moreover, additi on of exogeneous cytokines such as IL-1 beta, IL-1 alpha, or IL-2 did not reverse the defective function of UVB-irradiated LC in MELR. The i nhibitory effect of UVB radiation on human LC was not related to a dec reased HLA-DE expression, Because cultured LC appeared to be less sens itive than freshly isolated LC to UVB-induced suppressive effects, the deleterious effects of UVB radiation on human LC allostimulatory prop erties may be associated with an impaired development of LC accessory function. (C) 1995 Academic Press, Inc.