Pegylated interferon α-2a(Peg-IFN-α)and Nucleoside analog(ue) drugs can inhibit viral replication , but Peg-IFN-α also play an important role in immune regulation . In hepatitis B infection, Treg cells play an important role in immune regulation.Peg-IFN-α recommended as the first-line treatment has a higher chance to achieve HBeAg seroconversion and even HBsAg disappearance than nucleoside analog(ue) drugs, which may be related to the functional activation of Treg cells in the case of hepatitis and the function enhancement of Treg cells during Peg-IFN-α therapy. This study was aimed at investigating the changes of Treg cells frequency and function, and the expression of costimulatory molecules during Peg-IFN-αand nucleoside analog(ue) therapy.Meanwhile, the investigators wanted to verify whether Peg-IFN-α suppressed the virus, which led to the decline of Treg cells frequency and function;negative regulation of Tregs for immune cells diminished, hence, the function of immune cells recovered.