Sphingosine 1-phosphate (S1P) from platelets and macrophages stimulates migration and enhances survival of T cells. Mouse spleen CD4 and CD8 T cells are shown to express predominantly S1P1 (Edg-1) and S1P4 (Edg-6) G-protein-coupled receptors with only minimal representation of S1P2, S1P3, and S1P5. At and below plasma concentrations of healthy mammals (1 nM-1 microM), S1P evokes trans-Matrigel chemotaxis of mouse CD4 and CD8 T cells and recruits T cells into subcutaneous air pouches. T cell receptor-mediated activation of CD4 T cells suppresses expression of S1P1 and S1P4 receptors and eliminates their chemotactic responses to S1P. The immunoregulator FTY720, a structural homologue of S1P, lacks T cell chemotactic activity and competitively inhibits T cell chemotactic responses to S1P in vitro and in vivo. S1P may be a distinctive contributor to compartmental immunity by attracting naïve and memory T cells preferentially over activated effector T cells.

Murine CD4 and CD8 T cells express predominantly types 1 and 4 sphingosine 1-phosphate (S1P) G protein-coupled receptors (designated S1P1 and S1P4 or previously endothelial differentiation gene-encoded 1 and 6) for S1P, which has a normal plasma concentration of 0.1–1 μM. S1P now is shown to enhance chemotaxis of CD4 T cells to CCL-21 and CCL-5 by up to 2.5-fold at 10 nM to 0.1 μM, whereas 0.3–3 μM S1P inhibits this chemotaxis by up to 70%. Chemotaxis of S1P1, but not S1P4, transfectants to CXCL1 and CXCL4 was similarly affected by S1P. Activation of CD4 T cells, which decreases S1P receptor expression, suppressed effects of S1P on chemotaxis. Pretreatment of labeled CD4 T cells with S1P before reintroduction into mice inhibited by a maximum of 75% their migration into chemokine-challenged s.c. air pouches. The S1P-S1P1 receptor axis thus controls recruitment of naive T cells by maintaining their response threshold to diverse lymphotactic factors.

Sphingosine 1-phosphate (S1P) in blood, lymph, and immune tissues stimulates and regulates T cell migration through their S1P1 (endothelial differentiation gene encoded receptor-1) G protein-coupled receptors. We show now that S1P1Rs also mediate suppression of T cell proliferation and cytokine production. Uptake of [3H]thymidine by mouse CD4 T cells stimulated with anti-CD3 mAbs plus either anti-CD28 or IL-7 was inhibited up to 50% by 10−9–10−6 M S1P. Suppression by S1P required Ca2+ signaling and was reduced by intracellular cAMP. S1P decreased CD4 T cell generation of IFN-γ and IL-4, without affecting IL-2. A Th1 line from D011.10 TCR transgenic mice without detectable S1P1 was refractory to S1P until introduction of S1P1 by retroviral transduction. S1P then evoked chemotaxis, inhibited chemotaxis to CCL-5 and CCL-21, and suppressed Ag-stimulated proliferation and IFN-γ production. Thus, S1P1 signals multiple immune functions of T cells as well as migration and tissue distribution.

Sphingosine 1-phosphate (S1P) has diverse effects on T cells that are mediated by the predominant S1P1 and S1P4 G protein-coupled receptors (GPCRs). S1P4 is expressed principally by leukocytes, but little is known of its T cell effects in immunity. Two approaches were used to investigate S1P4 signals in T cells. First, S1P4 was introduced into D10G4.1 mouse Th2 cells and EL4.IL-2 mouse T cells lacking endogenous S1P GPCRs. Second, mouse splenic CD4 T cells were treated with FTY720 to suppress S1P1 and leave S1P4 GPCRs as the only functionally relevant S1P receptor. Unlike S1P1, S1P4 failed to transduce chemotactic responses of any of the S1P4-only T cells to S1P or the phyto-S1P ligand selective for S1P4, or to suppress their chemotactic responses to chemokines. The S1P-S1P4 axis significantly inhibited T cell proliferation in each of the S1P4-only T cells activated by anti-CD3 and anti-CD28 MoAbs. Secretion of IL-4 by S1P4-D10G4.1 cells, IL-2 by S1P4-EL4.IL-2, and IFN-gamma by FTY720-treated CD4 T cells were significantly inhibited by S1P. In contrast, S1P enhanced secretion of IL-10 by stimulated S1P4-D10G4.1 T cells. Thus, S1P4 mediates immunosuppressive effects of S1P by inhibiting proliferation and secretion of effector cytokines, while enhancing secretion of the suppressive cytokine IL-10.

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Sphingosine 1-phosphate (S1P) evokes T cell chemotaxis at 1-100 nM and inhibits chemotaxis to chemokines at 300 nM-1 uM through their predominant S1P1 G protein-coupled receptor (R). Mouse CD4+25+ regulatory T cells now are shown to express the same pattern of S1P1 > S1P4 >>other S1P Rs as other CD4 T cells. CD4+25+ T cell suppression of 3H-thymidine uptake and IL-2 generation by CD4+25- T cells stimulated with anti-T cell receptor antibodies without S1P was enhanced significantly by S1P at normal blood and lymph concentrations. These levels of S1P also enhanced IL-10 generation by CD4+25+ T cells by up to threefold compared with that without S1P but decreased IL-10 from CD4+25- T cells. That IL-10 from CD4+25+ T cells incubated with S1P mediates suppressive activity was demonstrated by prevention with neutralizing anti-IL-10 or anti-IL-10 receptor antibodies. Extracellular fluid S1P thus is required for optimal activity of CD4+25+ T cells.

Sphingosine 1-phosphate (S1P) from mononuclear phagocytes and platelets signals T cells predominantly through S1P 1 G protein-coupled receptors (Rs) to enhance survival, stimulate and suppress migration, and inhibit other immunologically relevant responses. Cellular S1P 1 Rs and their signaling functions are rapidly down-regulated by S1P, through a protein kinase C (PKC)-independent mechanism, but characteristics of cell-surface re-expression of down-regulated S1P 1 Rs have not been elucidated. T cell chemotactic responses (CT) to 10 and 100 nM S1P and inhibition of T cell chemotaxis to chemokines (CI) by 1 and 3 M S1P were suppressed after 1 h of preincubation with 100 nM S1P, but recovered fully after 12-24 h of exposure to S1P. Late recovery of down-regulated CT and CI, but not early down-regulation, was suppressed by PKC and PKC⑀-selective inhibitors and was absent in T cells from PKC⑀-null mice. The same PKC⑀ inhibitors blocked S1P-evoked increases in T cell nuclear levels of c-Fos and phosphorylated c-Jun and JunD after 24 h, but not 1 h. A mixture of c-Fos plus c-Jun antisense oligonucleotides prevented late recovery of down-regulated CT and CI, without affecting S1P induction of down-regulation. Similarly, S1P-elicited threonine phosphorylation of S1P 1 Rs was suppressed by a selective inhibitor of PKC⑀ after 24 h, but not 1 h. Biochemical requisites for recovery of down-regulated S1P 1 Rs thus differ from those for S1P induction of down-regulation.The lysophospholipids sphingosine 1-phosphate (S1P) 1 and lysophosphatidic acid (LPA) are generated and secreted by many types of stimulated cells (1, 2). At concentrations of 0.1-1 micromolar found normally in plasma and other extracellular fluids, S1P and LPA evoke cellular proliferation and diverse other functional responses through at least eight members of a family of homologous G protein-coupled receptors (GPCRs) (3, 4). Originally termed endothelial differentiation gene-encoded or Edg receptors (Rs), those specific for S1P now are officially re-named S1P 1 (Edg-1), S1P 2 (Edg-5), S1P 3 (Edg-3), S1P 4 (Edg-6), and S1P 5 (Edg-8), and those for LPA are LPA 1 (Edg-2), LPA 2 (Edg-4), and LPA 3 (Edg-7). Stimulated mononuclear phagocytes and platelets are the predominant sources of S1P and LPA in the immune system. Blood and lymphoid tissue CD4 and CD8 T cells, B cells, and mononuclear phagocytes all express S1P and LPA GPCRs, in cell type-specific patterns, which are regulated distinctively by their respective ligands and by cellular immune activation (5-8).T cells express predominantly S1P 1 and S1P 4 , of which S1P 1 transduces two distinct effects of S1P on T cell migration and also regulates other T cell functional responses (7,8). S1P is chemotactic for T cells at 0.001-0.1 M, enhances chemotactic responses to chemokines at 0.01-0.1 M, and suppresses T cell chemotaxis to numerous stimuli at 0.3-3 M. As T cell antigen receptor-dependent activation of T cells suppresses expression of S1P GPCRs and functional responses to S1P in parallel, the S1P-S1P 1 R ax...