PTGDR2 and asthma: It contributes to chemotaxis and activation of Th2 cells, eosinophils, basophils, and group 2 innate lymphoid cells (ILC2) through its receptor chemoattractant receptor–homologous molecule expressed on Th2 lymphocytes (CRTH2/DP2), and thus plays an important pro-inflammatory role in asthma and allergic diseases.