PDCD1 and autoimmune hepatitis: Collectively, the decrease of CTLA-4 and TFR-related factor IL-10/TGF-β1 and the increase of PD-1/ICOS in AIH patients lead to the decrease of TFR cells, while the increase of TFH-related factor IL-21 increases the number of TFH cells and the decrease of TFR/TFH ratio, thus promoting the differentiation of B cells and the production of immunoglobulin.