CD4 and inflammatory bowel disease: B. fragilis strains can induce the induction of regulatory CD4+ and CD8 + T cells secreting IL-10 to control innate inflammatory responses and mediate beneficial anti-inflammatory effects on inflammatory bowel disease.36,37 Taken together, the result indicated enriched B. fragilis in centenarians might promote longevity through modulating anti-inflammatory factor IL-10 expression to mediate the critical balance between health and disease.