Commensal epitopes drive differentiation of colonic T(regs)

The gut microbiome is the largest source of intrinsic non–self-antigens that are continuously sensed by the immune system but typically do not elicit lymphocyte responses. CD4(+) T cells are critical to sustain uninterrupted tolerance to microbial antigens and to prevent intestinal inflammation. However, clinical interventions targeting commensal bacteria–specific CD4(+) T cells are rare, because only a very limited number of commensal-derived epitopes have been identified. Here, we used a new approach to study epitopes and identify T cell receptors expressed by CD4(+)Foxp3(+) (T(reg)) cells specific for commensal-derived antigens. Using this approach, we found that antigens from Akkermansia muciniphila reprogram naïve CD4(+) T cells to the T(reg) lineage, expand preexisting microbe specific T(regs), and limit wasting disease in the CD4(+) T cell transfer model of colitis. These data suggest that the administration of specific commensal epitopes may help to widen the repertoire of specific T(regs) that control intestinal inflammation.