Expression of CD40 and CD40 ligand in the human conjunctival epithelium

Purpose. CD40 antigen is a membrane receptor that plays a role in the regul ation 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 II antigen, previously shown to be upregulat ed in conjunctival inflammatory conditions. Methods. Impression cytology specimens were collected in 186 patients: 52 n orm:ll ones, 65 with keratoconjunctivitis sicca, and 69 with chronic conjun ctivitis, Cells were processed for flow cytometry, by using monoclonal anti bodies to CD40, CD40L, and HLA DR antigens. Chang conjunctival cells were a lso used and treated with human recombinant interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha. CD40, CD40L, and HLA DR expressions were stud ied 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 patholo gic eyes than in normal ones (P < 0.0001). CD40L was variably; and inconsta ntly expressed by conjunctival cells. A strong expression of HLA. UR was ob served in pathologic eyes, whereas normal eyes showed very lon levels (P < 0.0001). Significantly positive correlations were found among CD40, CD40L, and HLA DR levels. Chang conjunctival cells expressed CD40 in basal conditi ons, whereas CD40L and HLA. DR were negative. CD40 expression significantly increased after 24 hours of IFN gamma treatment and after 48 hours' exposu re to TNF alpha. These cytokines had no effect on CD40L expression. HLA DR was upregulated after 24 hours of treatment with TFN gamma but remained neg ative after exposure to TNF alpha. Conclusions. Human conjunctival epithelial cells normally express CD40 anti gen, and, more inconsistently, CD40L. Flow cytometry showed higher expressi on of these molecules in inflammatory eyes than in normal ones in correlati on with class II antigen expression, as well as CD40 and HU DR upregulation after treatment with proinflammatory cytokines in vitro.