Expression of Fas-Fas ligand antigens and apoptotic marker APO2 center dot7 by the human conjunctival epithelium. Positive correlation with class IIHLA DR expression in inflammatory ocular surface disorders

Fas antigen (CD95) is a membrane receptor that plays a major role in induct ion of apoptosis, In surface conjunctival epithelial cells the expressions of Fas, Fas ligand, the apoptotic marker APO2.7 and of HLA DR class II anti gen, a membrane marker known to be expressed in inflammatory conditions wer e investigated. Impression cytology specimens were collected in 65 patients : 20 normal ones, 15 contact lens wearers, 20 receiving chronic topical ant iglaucoma treatment and 10 with nonspecific chronic conjunctivitis. Cells w ere processed for now cytometry, using monoclonal antibodies to Fas, Fas li gand, APO2.7, HLA DR antigens and a negative isotypic control. Percentages of positive cells were recorded and levels of fluorescence quantified using fluorescent beads at standardized fluorescence intensities, In addition, a human conjunctival cell line was incubated with anti-Pas stimulating antib odies in order to test Pas-induced apoptosis in vitro. Fas was found in all specimens in most of the conjunctival cells, but quantitation of levels of fluorescence showed a significantly higher expression in pathologic eyes t han in normal ones, Fas ligand and APO2.7 were variably expressed by conjun ctival cells, but in a significantly higher percentage of cells in patholog ical eyes than in normal ones. In these eyes a strong expression of HLA DR was also observed, whereas normal eyes showed lowest levels. Highly signifi cant correlations were found between Pas, Fas ligand, APO2.7 and HLA DR lev els. Anti-Fas antibodies in vitro induced strong apoptosis in epithelial ce lls as confirmed by APO2.7 expression and DAPI staining, This study confirm s that conjunctival epithelial cells normally express Fas antigen, and more inconstantly its ligand, as do corneal ones or keratinocytes. Fluorescence quantitation by now cytometry showed much higher expression in inflammator y eyes than in normal ones, and demonstrated a strong correlation between a poptotic and inflammatory pathways in the ocular surface. (C) 1998 Academic Press.