Crosstalk between the microbiota and intestinal γδ T cell compartments in health and IBD.

Unconventional T cells expressing the γδ T cell receptor (TCR) are abundant within the intestine and largely function as 'first responders' to injury, infection and inflammation. To this end, murine γδ T cells are highly compartmentalized within the intestinal mucosa based on the expression of their Vγ chain and their effector function. The activation status also differs among these γδ T cell populations to ensure a timely and appropriate response within their local microenvironment. In this review, we will examine the role of γδ T cell populations in the epithelium (i.e. intraepithelial lymphocytes), the lamina propria and Peyer's patches and discuss the influence of the gut microbiota on the maintenance and effector function of each compartment. We will also highlight how γδ T cells contribute to the host response to luminal bacteria and how this reciprocal crosstalk is disrupted in the context of inflammatory bowel disease (IBD). An enhanced understanding of how γδ T cells function within distinct mucosal compartments and their regulation by commensal bacteria may lead to the development of novel microbiome-based therapies for IBD.