IL-23 has been shown to be important in a number of inflammatory diseases including experimental autoimmune encephalitis (EAE), collagen-induced arthritis (CIA), colitis, and dermal inflammation (Cua et al., 2003; Murphy et al., 2003; Uhlig et al., 2006b; Zheng et al., 2007). The gene discussed is IL23A; the disease is colitis.