Retinal pigment epithelial cells are heterogeneous in their expression of MHC-II after stimulation with interferon-gamma

The pattern of interferon-gamma-induced major histocompatibility complex Cl ass II antigen expression was evaluated on the retinal pigment epithelium. Experiments were performed in vitro using explant cultures of aged and feta l human eyes and in vivo in albino rabbits. The human explants were stimula ted with 50 U ml(-1) interferon-gamma for 3 days prior to immunostaining fo r Class II. The rabbit eyes were subretinally injected in vivo with 50 mu l of interferon-gamma (500 U ml(-1)) and analyzed immunohistochemically 3 da ys later. A heterogeneous pattern of Class LI expression was present in the interferon-gamma-stimulated retinal pigment epithelial cells, in both the in vivo and the in vitro experiments. In aged human eyes the percent of Cla ss-II positive cells was higher in the periphery than in the posterior pole (macular region) after interferon-gamma stimulation (P < 0.01). No such di fference was found in the fetal eyes. These data demonstrate that retinal p igment epithelial cells are heterogeneous in their response to interferon-g amma. The results are supportive of previous studies demonstrating the stru ctural and proliferative heterogeneity of the retinal pigment epithelium. T ogether, these studies provide support for the possibility of functional re tinal pigment epithelial heterogeneity. (C) 1999 Academic Press.