EXPRESSION OF FAS LIGAND AND ITS RECEPTOR IN CUTANEOUS LUPUS - IMPLICATION IN TISSUE-INJURY

Fas ligand (Fast) is a type II membrane protein which belongs to the t umor necrosis factor family. Ligation of its receptor (Fas/APO-1/CD95) by Fast induces apoptosis of Fas expressing cells. However, the in vi vo function of these molecules in cutaneous immunity is presently unkn own. In the present study, we investigated the involvement of Fas and Fast in the pathogenesis of cutaneous lupus by immunohistochemical met hods. In normal skin, expression of Fas was observed on keratinocytes in the basal to granular layers. Unexpectedly, Fast was constitutively expressed on histiocytes in the dermis. In specimens of cutaneous lup us, Fas was expressed on infiltrating lymphocytes, as well as on kerat inocytes as observed in normal skin. Fast was expressed on a portion o f infiltrating CD4(+) T cells and on histiocytes more frequently than those in normal skin. Double staining indicated that these Fast-expres sing histiocytes were CD68 positive macrophages. Especially, Fast-expr essing macrophages were distributed around appendages such as hair fol licles. These results suggest the Fas/Fast interaction may be involved in the destruction of hair follicles which is a characteristic featur e of cutaneous lupus. (C) 1997 Academic Press.