Lack of FasL expression in cultured human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells have been proposed to play a part in maintaining the eye as an immune privileged organ. However, our knowledge of the implicated mechanism is still sparse. Pas ligand (FasL) expression o f RPE cells is generally recognized to be essential for the immune privileg e of the eye, but due to contradictory published results, it is unclear whe ther RPE cells express this molecule. The purpose of this study was to inve stigate the expression of FasL in RPE cells in vitro and in vivo. Cultured human fetal and adult RPE cells were examined by flow cytometry, Western bl otting, RT-PCR and RNase Protection assay for FasL expression. Additionally , sections of ocular tissue were stained for FasL by immunohistochemistry. None of the used methods indicated FasL expression in cultured fetal or adu lt RPE cells of various passages. However, RPE cells in vivo, as judged fro m tissue sections, were positive for FasL, indicating a discrepancy between RPE cells in vitro and in vivo with regard to this molecule. Copyright (C) 2001 S. Karger AG, Basel.