IL-12 PROMOTES THE ACCESSORY CELL-FUNCTION OF EPIDERMAL LANGERHANS CELLS

The objective of this study was to investigate the effects of cytokine s regulating cutaneous immune responses, on the accessory cell functio n of epidermal cells (EC). EC were treated with various cytokines, and the accessory cell function of the cytokine-pretreated EC was examine d by the allogeneic mixed epidermal cell-lymphocyte reaction (MECLR). Among the cytokines examined, IFN-gamma- and IL-12-pretreated EC augme nted IFN-gamma production in the MECLR, while none of the other cytoki nes was effective. However, the cytokine-pretreated EC did neither aff ect T cell proliferation nor IL-4 production in the MECLR. Next we att empted to analyze the mechanisms by which IL-12-pretreated EC increase IFN-gamma production in the MECLR. Endogenous IFN-gamma produced duri ng the IL-12 pretreatment of EC was found to play only a minor role in modulating the function of EC. The expression of MHC class II, CD80 a nd CD86 on EC was not affected by IL-12. On the other hand, soluble me diators that induce IFN-gamma production during the MECLR containing I L-12-pretreated EC were identified as endogenously produced IL-12 (the major mediator) and IL-18 (the minor mediator). Furthermore, the resu lts of depletion experiments indicate that IL-12 promotes the accessor y cell function of Langerhans cells to responder T cells in inducing I FN-gamma production in the MECLR. (C) 1998 Elsevier Science Ireland Lt d. All rights reserved.