In regard to colitis, various spontaneous animal models of colitis such as the HLA-B27 transgenic rats or genetically engineered mice deficient in the cytokines IL-2 or IL-10 do not develop colitis or develop a lesser degree of inflammation if they are kept in a germ-free environment, suggesting the importance of the gut microbiota as a driving force of the inflammatory process in the gut [9, 10]. Here, IL2 is linked to colitis.