An altered microbiota composition rendered IL-22−/− mice even more susceptible to colitis development than WT mice and can be explained by the fact that IL-22 plays a critical role in regulating the host microbiota composition due to its important antimicrobial properties including induction of antimicrobial peptides such as β-defensins, but also of the mucosal barrier forming mucins [27–30]. This evidence concerns the gene IL22 and colitis.