An orphan G protein-coupled receptor called G2A has important immunoregulatory roles because its deletion in mice results in an autoimmune disorder similar to systemic lupus erythematosus. Kabarowski et al. (see the Perspective by Carson and Lo) have now determined that a lipid present in cell membranes and serum called lysophosphatidylcholine (LPC) is the activating ligand of this receptor. LPC has previously been implicated in chronic inflammatory conditions such as systemic autoimmune diseases and atherosclerosis. The G2A-LPC interaction altered the migratory behavior of T cells.
M. J. Carson, D. Lo, The push-me pull-you of T cell activation. Science 293, 618-619 (2001). [Full Text]