The Immune Privilege of the Eye: Human Retinal Pigment Epithelial Cells Selectively Modulate T-Cell Activation In Vitro

Abstract

Purpose: To examine the effect of human retinal pigment epithelial (RPE) cells on phytohemagglutinin (PHA) activation of T cells. Methods: Resting peripheral blood lymphocytes (PBLs) were stimulated with PHA with or without the presence of γ -irradiated RPE cells. Proliferation and the cell cycle profile were thereafter investigated by 3H-thymidine incorporation and flow cytometric analysis. In addition, the PBLs expression of CD69, major histocompatibility complex (MHC) class I and II, CD3, as well as the IL-2 receptor chains were evaluated by flow cytometry, and the content of IL-2 in cell culture supernatant was measured by ELISA. Results: Human RPE cells were found to suppress PHA-induced proliferation, cyclin A, IL-2R-α and -γ, and CD71 expression and decrease the production of IL-2; but RPE cells do not inhibit the PHA-induced expression of early activation markers CD69, MHC class I and II, and of cyclin D of the PBLs. Conclusions: These results are the first to indicate that RPE cells impede generation of activated T cells by interfering with the induction of high-affinity IL-2R-α β γ, IL-2 production, and the expression of CD71 and cyclin A.

KEYWORDS:

• IL-2R
• inhibition
• proliferation
• RPE
• T cells