IL-22 is a relatively new cytokine that is characterized by several unique biological properties. In the intestines, the effect of IL-22 is restricted mainly to non-lymphoid cells such as epithelial cells. Interestingly, the expression pattern and major cellular source of IL-22 have distinct difference between large and small intestines. IL-22 possesses an ability to constitutively activate STAT3 for promoting epithelial cell regeneration and reinforcing mucosal barrier integrity through stimulating the expression of anti-bacterial peptide and mucins. Of note, IL-22 is characterized as a two-faced cytokine that can play not only protective but also deleterious roles in the intestinal inflammation depending on the cytokine environment such as the expression levels of IL-23, T-bet, and IL-22 binding protein. Most importantly, clinical relevance of IL-22 to inflammatory bowel disease has been well highlighted. Mucosal healing, which represents the current therapeutic goal for IBD, can be induced by IL-22. Indeed, indigo naturalis, which can activate IL-22 pathway through Ahr, has been shown in a clinical trial to exhibit a strong therapeutic effect on ulcerative colitis. Despite the beneficial effect of IL-22, continuous activation of the IL-22 pathway increases the risk of colitis-associated cancer, particularly in patients with an extended history of IBD. This review article discusses how IL-22 regulates colitis, how beneficial versus deleterious effects of IL-22 is determined, and why IL-22 represents a promising target for IBD therapy.

flammation. [9][10][11][12][13] Although the anti-inflammatory and anti-tumor effects of CAF have been reported by many groups in several organs, the possibility for coffee (but not only CAF) to affect intestinal inflammatory diseases is still controversial, as nicely reviewed by 2 recent review articles. 14,15 Notably, coffee is likely to play a protective role in mucosal inflammation based on a meta-analysis of the association between Crohn' s disease (CD) and beverage intake. 16 However, the biological mechanisms underlying the CAF-mediated effects on colonic epithelial cells (CECs) and colon cancer, especially colitis-associated cancer, remain controversial for almost the past 2 decades [17][18][19][20][21] and have not been fully explained scientifically.As one of the CAF-oriented research groups, we do not intend to discuss the detail of immunological or biological mechanisms of action on low-dose CAF and sugar (mainly sucrose) combinational administration in the incidence of inflammation-associated carcinogenesis, but we would like to suggest new possibilities for the relationship between the 2

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that affects many individuals throughout their lives. Ulcerative colitis (UC) and Crohn’s disease (CD) are two major forms of IBD. Until the early 1990s, a murine model of spontaneous chronic colitis was unavailable. As a major breakthrough in the basic research field of IBD, three genetically manipulated murine chronic colitis models, including interleukin (IL)-2 knockout (KO), IL-10 KO, and T cell receptor alpha chain (TCRα) KO models, were established in 1993. Since then, complicated immunobiological mechanisms during the development of UC have been gradually discovered by utilizing a wide variety of murine models of IBD, including the TCRα KO mouse model. In particular, it has been recognized that four major factors, including enteric, environmental, and immunological factors as well as enteric microbiota are highly and mutually involved in the pathogenesis of UC. As a pioneer of the TCRα KO murine model of UC, our group has identified that the interactions between the unique TCRα-β+ T cell population and antigen-presenting cells, including dendritic cells and B cells, play a key role for the development and regulation of UC-like chronic colitis, respectively. Here we have summarized clinically proven pathogenic and regulatory factors which have been identified by this novel TCRα KO murine model of UC in the past nearly three decades.