IL-23 has been shown to play a key role in both innate and T cell mediated chronic colitis in mouse models (Hue et al., 2006; Kullberg et al., 2006; Uhlig et al., 2006b; Yen et al., 2006) and IL23R has been identified as a risk gene in IBDs (Burton et al., 2007; Duerr et al., 2006). This evidence concerns the gene IL23A and Chronic colitis.