Selective IL-10 inhibition of HLA-DR expression in IFN-?-stimulated human retinal pigment epithelial cells

Abstract

PURPOSE. Human RPE cells express HLA-DR antigens, bind leukocytes via ICAM-1, and secrete IL-8 and MCP-1, which attract and activate leukocytes. Since little is known concerning endogenous cytokines that may alter ocular immunologic and inflammatory mechanisms, we investigated whether IL-10, an immunosuppressive cytokine, modulates these HRPE features. METHODS. IL-10 effects on HLA-DR and ICAM-1 were examined by HRPE exposures to: (1) IFN-? (10–1000 U/ml) + IL-10 (1–100 U/ml) and (2) IL-10 pre-incubation followed by IFN-? + IL-10. Immunohistochemistry for HLA-DR and ICAM-1 was graded by masked observers. Flow cytometric analysis quantitated HRPE HLA-DR and ICAM-1. Effects of IL-10 on IL-1ß (0.2 or 2 ng/ml)-, or TNF-a (0.2 or 2 ng/ml)-induced IL-8 and MCP-1 secretion and gene expression were assessed using enzyme-linked immunosorbent assay (ELISA) and Northern blot analysis. RESULTS. HLA-DR expression, detected by immunohistochemistry and flow cytometric analysis, showed dose-dependent increases to IFN-?. IL-10 pre-/co-incubation, but not co-incubation alone, markedly reduced HLA-DR expression, but did not modulate constitutive or IFN-?-induced ICAM-1. IL-10 alone did not induce MCP-1 or IL-8 secretion or steady-state mRNA expression, nor modulate IL-1ß-, TNF-a- or IFN-?-induced IL-8 or MCP-1. CONCLUSIONS. This study suggests that HRPE HLA-DR antigens are selectively inhibited by IL-10, but the timing of IL-10 exposure may be crucial.