PurposeIL-15 and IL-15 receptor expression was measured in retinal pigment epithelial (RPE) cells to support a possible role of IL-15 in ocular inflammatory and immune responses.MethodsReverse transcription-coupled polymerase chain reaction (RT-PCR) and Northern blot analysis of IL-15 mRNA in previously characterized non-transformed and simian virus (SV)-40 transformed human fetal RPE cells were carried out. Biological activities of IL-15 produced by the RPE cells were assayed by co-culture with IL-15 responsive cells. Expression of the IL-15 receptor (IL-15R)α, IL-2Rβandγchains were examined by RT-PCR.ResultsBoth non-transformed and SV-40 transformed human fetal RPE cells express IL-15, a T cell growth factor which has similar biological activities to IL-2, and the expression of IL-15 is enhanced by interferon-γ(IFN-γ) or tumor necrosis factor-α(TNF-α) stimulation. In addition, transcripts for all three IL-15 receptor components (IL-15Rα, IL-2Rβand IL-2Rγ) were detected in these cells.ConclusionsRPE cells produce IL-15, which may play an important role in ocular immune and inflammatory responses by stimulating infiltrated T cells and RPE cells via paracrine and autocrine loops, respectively. Curr. Eye Res. 15: 876–882, 1996.