Microbiota promote enhanced CD39 expression in gamma delta (gd) intraepithelial lymphocytes through the activation of TCR and IL-15 signaling.

Intraepithelial lymphocytes expressing the gd T cell receptor (gd IEL) provide continuous surveillance of the intestinal epithelium. We report that mice harboring a microbiota-specific hyperproliferative gd IEL (gdHYP) phenotype also upregulate the expression of the ectonucleotidase CD39, a marker of regulatory gd T cells. Enhanced TCR and IL-15 signaling correlates with a progression from a naïve-like CD39neg gd IEL to a more mature, tissue-adapted CD39hi IEL population. We find that TCRgd activation drives CD122-mediated CD39 upregulation on gdHYP IELs and increased mucosal IL-15 further amplifies CD39 expression in gdHYP IELs. Notably, CD39 induction requires sustained exposure to the gdHYP-associated microbiota. Increased IL-15 signaling prolongs IEL survival and enhances gdHYP IEL bioenergetic potential. Notably, CD39hi gd IELs produce less pro-inflammatory cytokine, which may explain the lack of histopathology in gdHYP mice. Overall, our study identifies a previously unappreciated mechanism by which an altered microbiota amplifies CD39 expression on gdHYP IELs, leading to the expansion of gd IELs with regulatory potential. RNAseq was performed on sorted Vg7 and Vg1 IELs isolated from murine small intestine from wildtype and gdHYP mice.