Chronic mucosal inflammation and tissue damage predisposes patients to the development of colorectal cancer (CRC)1. This association could be explained by the hypothesis that the same factors and pathways important for wound healing also promote tumorigenesis. A sensor of tissue damage should induce these factors to promote tissue repair and regulate their action to prevent development of cancer. IL-22, a cytokine of the IL-10 superfamily, plays an important role for colonic epithelial cell repair, and is increased in the blood and intestine of IBD patients2, 3. This cytokine can be neutralized by the soluble IL-22 receptor, known as the IL-22 binding protein (IL-22BP, IL-22RA2), however the significance of endogenous IL-22BP in vivo and the pathways that regulate this receptor are unknown4, 5. We describe herein that IL-22BP plays a crucial role in controlling tumorigenesis and epithelial cell proliferation in the colon. IL-22BP is highly expressed by dendritic cells (DC) in the colon in steady state conditions. Sensing of intestinal tissue damage via the NLRP3 or NLRP6 inflammasomes led to an IL-18-dependent down regulation of IL-22BP, thereby increasing the ratio of IL-22/IL-22BP. IL-22, which is induced during intestinal tissue damage, exerted protective properties during the peak of damage, but promoted tumor development if uncontrolled during the recovery phase.Thus the IL-22-IL-22BP axis critically regulates intestinal tissue repair and tumorigenesis in the colon.

Summary T helper 17 (Th17) cells are important for host defense against extra-cellular microorganisms. However they are also implicated in autoimmune and chronic inflammatory diseases, and as such need to be tightly regulated. The mechanisms that directly control committed pathogenic Th17 cells in vivo remain unclear. We showed here that IL-17A-producing CD4+ T cells expressed interleukin-10 receptor α (IL-10Rα) in vivo. Importantly, T cell specific blockade of IL-10 signaling led to a selective increase of IL-17A+IFN-γ− (Th17), and IL-17A+IFN-γ+ (Th17+Th1) CD4+ T cells during intestinal inflammation in the small intestine. CD4+ Foxp3− IL-10 producing (Tr1) cells and Foxp3+ regulatory (Treg) were able to control Th17 and Th17+Th1 cells in an IL-10-dependent manner in vivo. Lastly, IL-10 treatment of mice with established colitis decreased Th17 and Th17+Th1 cells frequencies via direct signaling in T cells. Thus IL-10 signaling directly suppresses Th17 and Th17+Th1 cells.

Interleukin-10 (IL-10) is essential to maintain intestinal homeostasis. CD4+ T regulatory type 1 (TR1) cells produce large amounts of this cytokine and being therefore currently examined in clinical trials as T-cell therapy in patients with inflammatory bowel disease (IBD). However, factors and molecular signals sustaining TR1 cell regulatory activity still need to be identified in order to optimize the efficiency and to ensure the safety of these trials. We investigated the role of IL-10 signaling in mature TR1 cells in vivo. Double IL-10eGFP Foxp3mRFP reporter mice and transgenic mice with impairment in IL-10 receptor signaling were used to test the activity of TR1 cells in a murine IBD model, a model that resembles the trials performed in humans. The molecular signaling was elucidated in vitro. Finally, we used human TR1 cells, currently employed for cell therapy, to confirm our results. We found that murine TR1 cells expressed functional IL-10 receptor α. TR1 cells with impaired IL-10 receptor signaling lost their regulatory activity in vivo. TR1 cells required IL-10 receptor signaling in order to activate p38 MAP kinase, thereby sustaining IL-10 production, which ultimately mediated their suppressive activity. Finally, we confirmed these data using human TR1 cells. In conclusion TR1 cell regulatory activity is dependent on IL-10 receptor signaling. These data suggest that in order to optimize TR1 cell-based therapy, IL-10 receptor expression has to be taken into consideration.

Acute liver injury can be secondary to a variety of causes, including infections, intoxication, and ischemia. All of these insults induce hepatocyte death and subsequent inflammation, which can make acute liver injury a life-threatening event. IL-22 is a dual natured cytokine which has context-dependent protective and pathogenic properties during tissue damage. Accordingly, IL-22 was shown to promote liver regeneration upon acute liver damage. However, other studies suggest pathogenic properties of IL-22 during chronic liver injury. IL-22 binding protein (IL-22BP, IL-22Ra2) is a soluble inhibitor of IL-22 that regulates IL-22 activity. However, the significance of endogenous IL-22BP in acute liver injury is unknown. We hypothesized that IL-22BP may play a role in acute liver injury. To test this hypothesis, we used -deficient mice and murine models of acute liver damage induced by ischemia reperfusion and-acetyl--aminophenol (acetaminophen) administration. We found that -deficient mice were more susceptible to acute liver damage in both models. We used × double-deficient mice to show that this effect is indeed due to uncontrolled IL-22 activity. We could demonstrate mechanistically increased expression of by hepatocytes, and consequently increased infiltration of inflammatory CD11bLy6C monocytes into the liver in -deficient mice upon liver damage. Accordingly, neutralization of CXCL10 reversed the increased disease susceptibility of-deficient mice. In conclusion, our data indicate that IL-22BP plays a protective role in acute liver damage, via controlling IL-22-induced expression.