Sphingosine-1-phosphate (S1P) is a sphingolipid metabolite formed through sphingosine phosphorylation by way of sphingosine kinases.1 S1P regulates several physiological processes including lymphocyte trafficking, cardiac function, and vascular tone. These activities are mediated through interaction of S1P with five G-protein coupled receptors (S1P1-5 receptors) that have an effect on diverse cell types including lymphocytes, atrial myocytes, endothelial cells as well as other cell types.2
In lymphoid tissue, S1P binds to S1P1 on the surface of lymphocytes. Triggered by an S1P gradient, B and T lymphocytes exit lymphoid tissue and enter circulation.4 S1P signaling does not affect subsets of lymphocytes that do not travel through the lymphoid tissue, and thus remain in circulation for immune surveillance against infections and tumors.2 Lymphocytes (including B and T cells) play a critical role in regulating proinflammatory and anti-inflammatory activity.3
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