MAIT cells are associated with eosinophil presence and activation in the inflamed tissue of patients with eosinophilic esophagitis.

EoE is an inflammatory condition characterised by tissue lesions and significant activation of immune cells in the oesophageal mucosa. Phenotypic and functional analyses in this study revealed widespread accumulation and activation of multiple immune cell types, with eosinophils showing the most notable expansion and activation. MAIT cells were the only activated T cell population associated with eosinophil activation, and this activation correlated with eosinophil infiltration in oesophageal tissue. Functional tests indicated that eosinophils increase MR1 expression in response to bacterial ligands and can present microbial antigens to and activate MAIT cells through an MR1- and TCR-dependent process, which, in turn, promotes cytokine release and further eosinophil activation. These findings reveal a previously unrecognised eosinophil-MAIT cell interaction that might enhance local immune responses by presenting microbial antigens that penetrate the lesioned mucosa and sustain inflammation in active EoE.