Abstract

Intraepithelial lymphocytes expressing the {gamma}{delta} T cell receptor ({gamma}{delta} IELs) serve as a first line of defense against luminal microbes. Although the presence of an intact microbiota is dispensable for {gamma}{delta} IEL development, several microbial factors contribute to the maintenance of this sentinel population. However, whether specific commensals influence population of the {gamma}{delta} IEL compartment under homeostatic conditions has yet to be determined. We identified a novel {gamma}{delta} IEL hyperproliferative phenotype that arises early in life and is characterized by expansion of multiple V{gamma} subsets. Horizontal transfer of this hyperproliferative phenotype to mice harboring a phenotypically normal {gamma}{delta} IEL compartment was prevented following antibiotic treatment, thus demonstrating that the microbiota is both necessary and sufficient for the observed increase in {gamma}{delta} IELs. Further, we identified a group of unique gut bacteria represented by 5 amplicon sequence variants (ASV) which are strongly associated with {gamma}{delta} IEL expansion. Using intravital microscopy, we find that hyperproliferative {gamma}{delta} IELs also exhibit increased migratory behavior leading to enhanced protection against bacterial infection. These findings reveal that transfer of a specific group of commensals can regulate {gamma}{delta} IEL homeostasis and immune surveillance, which may provide a novel means to reinforce the epithelial barrier.