Abstract
Abstract: :
Purpose: Th1–type response has been implicated in the pathogenesis of autoimmune diseases such as uveitis. The purpose of this study is to determine the role of IL–27/WSX–1 signaling in the differentiation of naive CD4+ T cells into Th1 cells. Methods: Interaction between WSX–1 and STATs was determined by immunoprecipitation in WSX–1–overexpressing cells and GST pull–down assay. Transcriptional activation of STAT1 was assessed by luciferase assay. IL–27–induced STAT1 tyrosine–phosphorylation was analyzed by Western blotting analysis and proliferation was determined by [3H] thymidine uptake. IL–27–induced IL–12–dependent IFN–γ production was assessed by ELISA. Western blotting analysis and RT–PCR were performed to examine the expression of IL–27–dependent T–bet, a key transcriptional factor for Th1 differentiation, and IL–12Rß2. Results: STAT1 but not other STATs interacted with tyrosine–phosphorylated WSX–1 in WSX–1–overexpressing cells or tyrosine–phosphorylated recombinant WSX–1. Transient expression system using IL–12Rß2/WSX–1 chimeric receptors revealed that transcriptional activation of STAT1 through downstream of WSX–1 is dependent on the conserved tyrosine residue of the cytoplasmic domain of WSX–1. IL–27 induced STAT1 tyrosine–phosphorylation and proliferation of wild–type but not WSX–1–deficient naïve CD4+ T cells. Although IL–27 did not directly induce IFN–γ production by wild–type naïve CD4+ T cells, IL–12–dependent IFN–γ production was augmented by IL–27 stimulation in wild–type naïve CD4+ T cells but not in WSX–1–deficient naïve CD4+ T cells. Additionally, IL–27 stimulation induced T–bet and IL–12Rß2 expression in wild–type, but not in WSX–1–deficient, CD4+ T cells. Conclusions: IL–27/WSX–1 signaling system plays a pivotal role in the initiation of Th1 differentiation by STAT1–dependent induction of T–bet and IL–12Rß2, suggesting that IL–27/WSX–1 signaling might be implicated in the pathogenesis of autoimmune diseases such as uveitis.
Keywords: immunomodulation/immunoregulation • signal transduction • transcription factors