responses in cells, tissues, and animal models. GPR99/OXGR1 – ; GPR99, also known as the 2-oxoglutarate receptor 1 (OXGR1) or cysteinyl leukotriene receptor E (CysLTE), is a third CysLTR receptor; unlike CYSLTR1 and CYSLTR2, GPR99 binds and responds to Leukotriene E4 much more strongly than to leukotriene C4 or leukotriene D4. GPR99 is also the receptor for alpha-ketoglutarate, binding and responding to this ligand much more weakly than to any of the three cited leukotrienes. Activation of this receptor by LTC4 is associated with pro-allergic responses in cells and an animal model. The function of GPR99 as a receptor for leukotriene E4 has been confirmed in a mouse model of allergic rhinitis. GPR17 – ; while one study reported that leukotriene C4, leukotriene D4, and leukotriene E4 bind to and activate GPR17 with equal potencies, many subsequent studies did not confirm this. GPR17, which is mainly expressed in the central nervous system, has also been reported to be the receptor for the purines, Adenosine triphosphate and Uridine diphosphate, and certain glycosylated uridine diphosphate purines (http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=88) as well as to be involved in animal models of central nervous system Demyelinating reactions. However, recent reports failed to confirm the latter findings; a consensus of current opinion holds that the true ligand(s) for GPR17 remain to be defined (http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=88). Lipoxin Lipoxins: ALX/FPR2 (also termed FPR2, ALX, ALX/FPR, formyl peptide receptor-like 1) – ; receptor for Lipoxin A4 and 15-epi-Lipoxin A4 (or AT-LxA4) eicosanoids but also many other agents including the docosanoids resolvin D1, resolvin D2, and 17R-resolvin D1 (see specialized pro-resolving mediators; oligopeptides such as N-Formylmethionine-leucyl-phenylalanine; and various proteins such as the amino acid 1 to 42 fragment of Amyloid beta, Humanin, and the N-terminally truncated form of the chemotactic chemokine, CCL23 (see FPR2#Ligands and ligand-based disease-related activities). Relative potencies in binding to and activating ALX/FPR are: lipoxin A4=aspirin-triggered lipoxin A4>leukotriene C4=leukotriene D4>>15-deoxy-LXA4>>N-Formylmethionine-leucyl-phenylalanine (http://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=223}. Activation of ALX/FPR2 by the lipoxins is associated with anti-inflammatory responses by target cells and tissues. Receptors that bind and respond to a wide range of ligands with such seemingly different structural similarities as those of ALX/FPR are often termed promiscuous. Resolvin E Resolvin Es: CMKLR1 – ; CMKLR1, also termed Chemokine like receptor 1 or ChemR23, is the receptor for the eicosanoids resolvin E1 and 18S-resolvin E2 (see specialized pro-resolving mediators) as well as for chemerin, an adipokine protein; relative potencies in binding to and activating CMKLR1 are: