Extracellular distribution of galectin-10 in the esophageal mucosa of patients with eosinophilic esophagitis

Eosinophilic esophagitis is a T-cell-driven allergic condition hallmarked by eosinophil infiltration of the esophagus. Eosinophils exposed to proliferating T cells release galectin-10 and have T-cell suppressive function in vitro. The aims of this study were to evaluate if eosinophils co-localize with T cells and release galectin-10 in the esophagus of patients with eosinophilic esophagitis. Esophageal biopsies from 20 patients with eosinophilic esophagitis were stained for major basic protein, galectin-10, CD4, CD8, CD16, and CD81 and analyzed by immunofluorescence confocal microscopy before and after topical corticosteroid treatment. CD4+ T-cell numbers decreased in the esophageal mucosa of responders to treatment but not in the non-responders. Suppressive (CD16+) eosinophils were present in the esophageal mucosa of patients with active disease and decreased after successful treatment. Unexpectedly, eosinophils and T cells were not in direct contact with each other. Instead, the esophageal eosinophils released large amounts of galectin-10-containing extracellular vesicles and featured cytoplasmic projections that contained galectin-10, both of which disappeared from the esophagus of the responders but remained in the non-responders. To conclude, the presence of CD16+ eosinophils together with the massive release of galectin-10-containing extracellular vesicles in the esophageal mucosa might indicate that eosinophils exert T-cell suppression in eosinophilic esophagitis.