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