PGD2 injection in the esophagus leads to an increase of eosinophil infiltration in esophageal epithelium at the injection site (Zhang et al., 2014), and prostaglandin D synthase is expressed in adaptive CD4+ effector memory Th2 cells in EoE (Mitson-Salazar et al., 2016). Here, CD4 is linked to eosinophilic esophagitis.