Expression of CD40 and CD40 ligand in the human conjunctival epithelium.

PURPOSE CD40 antigen is a membrane receptor that plays a role in the regulation of immune reactions. The expressions of CD40 and CD40 ligand (CD40L) were investigated ex vivo and in vitro in conjunctival epithelial cells, in correlation with HLA DR class H antigen, previously shown to be upregulated in conjunctival inflammatory conditions. METHODS Impression cytology specimens were collected in 186 patients: 52 normal ones, 65 with keratoconjunctivitis sicca, and 69 with chronic conjunctivitis. Cells were processed for flow cytometry, by using monoclonal antibodies to CD40, CD40L, and HLA DR antigens. Chang conjunctival cells were also used and treated with human recombinant interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha. CD40, CD40L, and HLA DR expressions were studied by flow cytometry after 24 and 48 hours of treatment. RESULTS CD40 was found in both normal and pathologic eyes. Quantitation of levels of fluorescence showed a significantly higher expression in pathologic eyes than in normal ones (P < 0.0001). CD40L was variably and inconstantly expressed by conjunctival cells. A strong expression of HLA DR was observed in pathologic eyes, whereas normal eyes showed very low levels (P < 0.0001). Significantly positive correlations were found among CD40, CD40L, and HLA DR levels. Chang conjunctival cells expressed CD40 in basal conditions, whereas CD40L and HLA DR were negative. CD40 expression significantly increased after 24 hours of IFNgamma treatment and after 48 hours' exposure to TNFalpha. These cytokines had no effect on CD40L expression. HLA DR was upregulated after 24 hours of treatment with IFNgamma but remained negative after exposure to TNFalpha. CONCLUSIONS Human conjunctival epithelial cells normally express CD40 antigen, and, more inconsistently, CD40L. Flow cytometry showed higher expression of these molecules in inflammatory eyes than in normal ones in correlation with class II antigen expression, as well as CD40 and HLA DR upregulation after treatment with proinflammatory cytokines in vitro.