title: Role of interleukin-21 in HBV infection: friend or foe?
abstract: Interleukin (IL)-21, a cytokine produced by activated CD4(+) T cells, has broad pleiotropic actions that affect the functions of a variety of lymphoid cells. The roles of IL-21 in modulating immunity to infections are currently being defined. Notably, IL-21-mediated cellular and humoral immune responses play an important role in determining the outcome of viral infection. This article reviews the current knowledge on the critical role of IL-21 in hepatitis B virus (HBV) infection. As a competent intermediary, IL-21 derived from virus-specific CD4(+) T cells plays key roles in sustaining CD8(+) T cells and promoting B-cell responses that are essential for effective viral control. However, as a mediator of inflammation, IL-21 is also involved in the development of HBV-induced liver cirrhosis and exacerbating liver injury. Overall, the current data point to IL-21 as an immunomodulatory cytokine in HBV infection. Immunotherapeutic strategies aimed at optimizing the beneficial effects of IL-21 in HBV infection may prove to be a rigorous challenge in the future, as they should foster the strengths of IL-21 while circumventing potential drawbacks.
authors.affiliation: 1] Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, China [2] State Key Laboratory of Organ Failure Research, Southern Medical University, Guangzhou, China [3] Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, China.
authors.forename: Yongyin
authors.initials: Y
authors.lastname: Li
authors.affiliation: 1] Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, China [2] State Key Laboratory of Organ Failure Research, Southern Medical University, Guangzhou, China.
authors.forename: Libo
authors.initials: L
authors.lastname: Tang
authors.affiliation: 1] Department of Infectious Diseases and Hepatology Unit, Nanfang Hospital, Southern Medical University, Guangzhou, China [2] State Key Laboratory of Organ Failure Research, Southern Medical University, Guangzhou, China [3] Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, China.
authors.forename: Jinlin
authors.initials: J
authors.lastname: Hou
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D006515:Hepatitis B virus / Q000276:immunology*; D019694:Hepatitis B, Chronic / Q000276:immunology* / Q000628:therapy; D006801:Humans; D056724:Immunity, Humoral; D056747:Immunomodulation; D007167:Immunotherapy / Q000639:trends; D007378:Interleukins / Q000276:immunology*; D008103:Liver Cirrhosis / Q000276:immunology* / Q000628:therapy; D000098546:Interleukin-21
chemical_list: D007378:Interleukins; D000098546:Interleukin-21