A conserved Bacteroidetes antigen induces anti-inflammatory intestinal T lymphocytes

The microbiome contributes to the development and maturation of the immune system. In response to commensal bacteria, intestinal CD4+ T lymphocytes differentiate into functional subtypes with regulatory or effector functions. Whereas the development of small intestine intraepithelial lymphocytes that express CD4 and CD8aa homodimers (CD4IELs) depends on the microbiota, the identity of the microbial antigens recognized by CD4+ T cells that can differentiate into CD4IELs remains unknown. We identified B-hexosaminidase, a conserved enzyme across commensals of the Bacteroidetes phylum, as a driver of CD4IEL differentiation. In a mouse model of colitis, B-hexosaminidase-specific lymphocytes protected against intestinal inflammation. Thus, T cells of a single specificity can recognize a variety of abundant commensals and elicit a regulatory immune response at the intestinal mucosa. Overall design: mRNA profile of 175 IELs tetramer-positive or negative for P. goldsteinii B-N-acetylhexosaminidase (B-hex)