Interleukin‐33/ST2‐Mediated Inflammation Plays a Critical Role in the Pathogenesis and Severity of Type I Autoimmune Hepatitis

Interleukin (IL)‐33 was recently described as a new member of the IL‐1 family; members of this family have proinflammatory activity. IL‐33 and its soluble receptor ST2 (sST2) have been implicated in the pathogenesis of autoimmune diseases. This study investigated serum IL‐33 and sST2 in type I autoimmune hepatitis (AIH) and the relationship of these molecules with clinical and pathologic parameters. Subjects included 65 patients with AIH who were diagnosed in our hospital. The control population included 17 healthy individuals and 36 patients with primary biliary cholangitis (PBC). Mean age at AIH diagnosis was 55.5 years, and the male‐to‐female ratio was 6:59. Serum IL‐33 and sST2 levels were significantly higher in patients with AIH than in those with PBC or controls. Importantly, immunohistochemistry revealed high IL‐33 expression in liver sections from patients with AIH. In particular, serum IL‐33 and sST2 levels were significantly higher in acute‐onset AIH than in chronic‐onset AIH. Serum IL‐33 levels were positively correlated with serum total bilirubin (TB), alanine aminotransferase (ALT), and necroinflammatory activity in AIH. We performed multivariate logistic regression analysis and found serum IL‐33 levels to be independent factors for severe activity. Serum sST2 levels were positively correlated with serum TB and ALT and negatively correlated with serum albumin and prothrombin time in AIH. In particular, serum sST2 levels were significantly higher in severe symptoms of AIH. Serum IL‐33 and sST2 levels in patients with AIH responsive to treatment with prednisolone were significantly decreased after treatment. Interestingly, serum IL‐33 level was associated with a significantly increased risk of relapse. Conclusion: IL‐33/ST2 may play an important role in the pathogenesis and severity of AIH and may be a promising target for AIH therapy.