MHC class II positive retinal pigment epithelial (RPE) cells can function as antigen-presenting cells for microbial superantigen

Retinal pigment epithelial (RPE) cells induced to express MHC class II (HLA-DR) by incubation with interferon gamma (IFN-α) were investigated for their ability to present a microbial superantigen to T lymphocytes. Superantigens bind to MHC class II antigens and appear to play a role in a number of infectious and autoimmune diseases through stimulation of large numbers of T cells. Primary cultures of human RPE cells treated with IFN-α for three days to induce HLA-DR expression bound staphylococcal enterotoxin E (SEE) via HLA-DR and presented SEE to T cells as measured by proliferation of purified peripheral blood T cells and IL-2 synthesis by the Jurkat T cell line. Untreated RPE cells were essentially ineffective as superantigen presenting cells. These results suggest that MHC class II expressing RPE cells could contribute to immune and inflammatory activity in the eye by presenting superantigens to T lymphocytes.