CRTh2 (chemoattractant‐receptor homologous molecule expressed on Th2 cells) is expressed by Th2 cells and other cells involved in allergic inflammation. Single nucleotide polymorphisms (SNPs) in CRTh2 (rs11571288, rs545659, rs634681) have been associated with various phenotypes of allergy in ethnically distinct populations. Here, we assessed the association between CRTh2 rs533116 and allergic asthma, expression of CRTh2 and Th2 cytokine production.

CRTh2 rs533116 was genotyped in an ethnically diverse population (n = 1282). The proportion of cells expressing CRTh2 was determined in peripheral blood from subjects with allergic airways disease and controls as well as with in vitro differentiated Th2 cells. Receptor function was assessed by stimulating Th2 cells with the CRTh2‐specific agonist 13,14‐dihydro‐15‐keto‐PGD₂ (DK‐PGD₂) and measuring IL‐4 and IL‐13 by intracellular staining and ELISA.

CRTh2 rs533116 was associated with allergic asthma in White people (2.67 [1.09–6.55], P < 0.05), and expression of CRTh2 was higher in subjects with allergic airways disease compared to controls (P < 0.05). Among allergic individuals, the AA genotype was significantly associated with more eosinophils and higher expression of CRTh2 by both CD4⁺ T cells and eosinophils (P < 0.05). In vitro, the AA genotype was associated with a higher proportion of CRTh2⁺ cells during Th2 differentiation as well as more IL‐4 and IL‐13 expression following DK‐PGD₂ stimulation (P < 0.05).

These findings show an association between CRTh2 rs533116 and allergic asthma and suggest this may be mediated by elevated expression of CRTh2, leading to higher numbers of circulating eosinophils and Th2 cytokine production.