CD4 and allergic disease: The species Flavonifractor plautii is a gram-positive anaerobic bacterium from the genera Flavonifractor belonging to Firmicutes. An animal experiment demonstrated that oral intervention of Flavonifractor plautii ameliorated antigen-induced Th2 immune responses and allergy by inhibiting interleukin-4 and IgE production and augmenting CD4+CD25+ T cells and CD103+CD11c+ DCs [51].