Dietary influence and immune balance: Regulating CD4+IEL responses and MHCII in the gut

Abstract

Over the past decade, interest in CD4 positive intraepithelial lymphocytes (IELs) has been growing. This subset of long-overlooked helper T cell plays critical roles in intestinal homeostasis and in responses to intestinal infections. Located in the interface of the gut, this subset includes T cells reactive to both microbial-derived and food antigens. However, microbial stimulation seems to be indispensable for their maturation. The major regulator of CD4+ CD8αα+ cells in the IEL compartment is MHCII-mediated antigen presentation by intestinal epithelial cells (IECs) and epithelial MHCII is induced only by certain commensal bacterial strains under physiological conditions.