Emerging Role of Interleukin 22 in Hepatitis B Virus Infection: a Double-edged Sword

Hepatitis B virus (HBV) infection remains a worldwide health problem, and is the major cause of hepatitis, liver cirrhosis, and hepatocellular carcinoma. The innate and adaptive immune responses of the HBV-infected host contribute greatly to the development and pathogenesis of chronic HBV infection, and often affect the efficacy of anti-HBV drugs. Interleukin (IL)-22 is a newly identified cytokine that is involved in the pathogenesis of liver disease, but its role in liver inflammation in patients with HBV infection remains controversial. In this report, we summarize the production and function of IL-22 in inflammatory environments, and review the current research into IL-22 biology in HBV infection. A better understanding of the intrahepatic microenvironments that directly influence the activity of IL-22 will be important for the development of new immunotherapeutic approaches that target IL-22-producing cells or IL-22 itself.