Some strains from clusters IV, XIVa and XVIII of Clostridia are benefical to the host, and oral administration of them can ameliorate mice colitis, because these bacteria lack prominent virulence and have been proven to provide a TGF-β-rich environment to promote the growth and differentiation of anti-inflammatory cells and the upregulation of anti-inflammatory molecules, especially regulatory T cells (Treg) and IL-10 (67). Here, IL10 is linked to colitis.