Lysophosphatidic acid as a regulator of lymphocyte trafficking in the lymph nodes
Lysophosphatidic acid (LPA) is a bioactive lysophospholipid that regulates multiple biological functions, including cell migration, survival, and proliferation, through the binding of specific G-protein coupled receptors. Although LPA is known to enhance immune cell migration, the identity of the LPA-expressing cells and the mechanism by which LPA regulates leukocyte migration in lymphoid tissues have remained unclear. Using imaging mass spectrometry and intravital two-photon microscopy, we examined the localization of LPA in the lymph nodes and determined its role in lymphocyte migration. We found that LPA is produced by the vascular endothelial cells and other stromal cells within the lymph nodes by the action of the ectoenzyme, autotaxin (ATX). We also found that LPA regulates both lymphocyte transendothelial migration across high endothelial venules (HEVs), and interstitial lymphocyte migration, by acting on both stromal cells and lymphocytes through specific cell-surface receptors for LPA. In this review, we focus on recent advances in our understanding of the expression and function of LPA in immune cell trafficking.