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Department of Medicine and Department of Microbiology-Immunology, University of California, San Francisco, CA 94143
Sphingosine 1-phosphate (S1P) is a natural lipid mediator that regulates immune cell traffic, Ab production, and T cell cytokine generation by mechanisms that enhance Th2 activities. Responses to S1P are controlled principally by the diverse expression patterns of its receptors in different cells. In T cells, the type 1 (S1P1) and type 4 (S1P4) G protein-coupled receptors are predominant. S1P1 mainly transduces effects on T cell migration and trafficking, whereas S1P4 transduces immunosuppression via its effects on T cell proliferation and cytokine production. Using T cell-specific S1P1 transgenic (TG) mice, we investigated the regulatory effects of the S1P-S1P1 axis on T cell cytokine production. The production of IL-4, but not IL-2 or IFN-
, was significantly up-regulated >10-fold in activated CD4 T cells from S1P1 TG mice compared with those from wild-type mice. Quantitative real-time PCR analysis revealed that IL-4 up-regulation was initiated at the mRNA level as early as 4 h after T cell activation. The up-regulation of IL-4 mRNA was mediated by c-Maf, Jun B, and Gata3 as demonstrated by increases in their protein expression and DNA-binding activities. In contrast, the expression and DNA-binding activities of T-bet, FosB, C-Fos, Jun D, Fra-1, Fra-2, and c-Jun all were identical in wild-type and TG CD4 T cells. Immunological assays showed that increased IL-4 levels induced greater production of IgE. Thus, the S1P-S1P1 axis specifically up-regulates c-Maf, Jun B, and Gata3, which consequently enhance IL-4 production that may lead to a Th2 phenotype.
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1 This work was supported by Grant R01-HL31809 from the National Institutes of Health (to E.J.G.) and the Rainin Endowed Research Fellowship.
2 Address correspondence and reprint requests to Dr. Edward J. Goetzl, University of California, UB8B, Box 0711, 533 Parnassus at 4th Avenue, San Francisco, CA 94143. E-mail address: Edward.Goetzl{at}ucsf.edu
3 Abbreviations used in this paper: S1P, sphingosine 1-phosphate; TG, transgenic; WT, wild type; HPRT, hypoxanthine phosphoribosyltransferase; CT, threshold cycle; FoxP3, forkhead box P3; GITR, glucocorticoid-induced TNF-like receptor; CHIP, chromatin immunoprecipitation; Treg, regulatory T cell; GPCR, G protein-coupled receptor.
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