Thus, T cells with a reduced capacity to respond to TGF-β cannot be suppressed by Treg cells in mouse models of colitis (Fahlén et al., 2005; Liu et al., 2003) and experimental autoimmune encephalomyelitis (Zhang et al., 2006), and production of TGF-β1 by Treg cells is required for their suppression of colitic T cells in vivo (Nakamura et al., 2004; Pesu et al., 2008). This evidence concerns the gene TGFB1 and colitis.