Background CRTH2 (chemoattractant receptor-homologous molecule), which is also known as the putative G protein-coupled receptor GPR44, is expressed on Th2 cells and is a novel member of the G protein-coupled leukocyte chemoattractant receptor family, which is selectively expressed in Th2 but not Th1 lineage cells. CRTH2 is selectively expressed in vivo in an activated state of Th2 cells including allergen-responsive Th2 cells, suggesting its pivotal roles in ongoing Th2-type immune reactions. |