IL21 and autoimmune hepatitis: Upon self-antigen presentation by liver APCs, the activation of a variety of immune cells such as Th0-, Th1- and Th2-CD4+ T cells, Th17 cells, cytotoxic CD8+ T cells, regulatory T cells (Treg), natural killer (NK) cells and B cells, along with the release of cytokines including interferon (IFN)-γ, transforming growth factor-β (TGF-β), interleukin (IL)-10, IL-21, IL-2 and autoantibodies results in autoimmune attack of liver in AIH.