Singling out Th2 cells in eosinophilic esophagitis.

Eosinophilic esophagitis (EoE) is a recently described disease in which exposure to specific foods and allergens leads to type 2 inflammation, epithelial barrier dysfunction, and difficulty in swallowing. In the current issue of the JCI, Wen and colleagues investigate tissue T cell heterogeneity in patients with EoE using single-cell RNA sequencing (scRNA-seq). Esophageal epithelium from individuals with EoE convtained a prominent population of Th2 cells not seen in controls. The short-chain fatty acid (SCFA) receptor FFAR3 was found to be highly expressed in EoE Th2 cells. Experiments presented here provide evidence that SCFAs may promote type 2 inflammation in allergic diseases such as EoE and asthma. This study provides an early example of scRNA-seq for identifying relevant cell populations and mechanisms underlying allergic diseases.