Cytokine-mediated activation of a neuronal retinal resident cell provokes antigen presentation

The retinal pigment epithelial (RPE) cell has long been considered an important regulatory cell, maintaining physiological and structural balance within the retina. We have previously shown that the RPE cell may also be important in autoimmunity and transplantation. These cells can be induced by cytokines to express MHC class II Ag in ocular inflammatory and autoimmune conditions. In this report we show that isolated rat RPE cells can be induced to express class II Ag following incubation with rat rIFN-gamma. The ability of RPE cells to present Ag was determined by both T cell proliferation assays and IL-2 production. Only the Ia-positive RPE cells can present retinal Ag (S-Ag and interphotoreceptor-binding protein) to specifically sensitized rat Th cells. Moreover, the ability of chloroquine to inhibit this activity suggests that the RPE cell is also capable of processing Ag prior to Ag presentation. These studies indicate that cytokine-mediated activation of RPE cells may be a basic component of ocular immunity and an important aspect of RPE cell transplantation.