HLA DR and DQ expression on human retinal pigment epithelial cells in vitro

In a previous immunohistopathological study, we demonstrated a deviant expression of class II antigens on the uveal pigment epithelial cells of patients with proliferative diabetic retinopathy. The mechanisms triggering this abnormal expression by epithelial cells are not well known, and we tried to induce this phenomenon on primary cultures of human retinal pigment epithelial (RPE) cells. Confluent RPE-cell monolayers were supplemented with several biological or chemical reagents [recombinant interferon gamma, phytohemagglutinin A-P (PHA-P), phorbol-myristate acetate (PMA), recombinant interleukin-2, fibroblast growth factor (FGF), Insulin], to investigate their ability to induce HLA DR and DQ expression. On days 1, 3 and 5 after stimulation, the cells were incubated with monoclonal antibodies directed against human class II antigens: all reagents used failed to induce class II antigen: all reagents used failed to induce class II antigen expression. However, on day 7, we demonstrated the presence of numerous positive HLA DR and HLA DQ cells stimulated by gamma interferon, the percentages being closely related to the dose of this lymphokine. These findings, together with those of other investigators and our previous work on uveal pigmented epithelial cells in diabetic patients, may shed light on the exact implication of RPE in many poorly documented ocular diseases.