Abstract： Objective To investigate the effect of programmed death(PD)-1/PD-L1 interaction on immunc response of HBsAg-pulsed dendritic cells(DCs)vaccine.Methods DCs were genermed from bone marrow cells from BALB/c mice and pulsed with HBsAg protein.HBV transgenic mice were injected i.D with PD-L1 blocking monoclonal antibodies(Abs)1 d before DC/HBsAg transfer with an interval of 3 d for 3 times,and then divided into 5 groups:DC/HBsAg+PD-L1 Abs group,DC/HBsAg group,DC group,mlgG group and phosphate buffered saline(PBS)group.Extracellular molecule and intraceilular cytokine of splenic T cells were analyzed by flow cytometry,HBsAg-specific activity of splenic cytotoxic T lymphocytes (CTLs)was detected by LDH release assay,HBsAg and HBV DNA titers in sera were monitored by ELISA and fluorescent quantitative PCR,and hepatic injury Was monitored by measuring serum ALT at 3th and 6th after immunization,respectively.SPSS 13.0 software Was used for data processing,and ANOVA(analysis of variance)as well as q test were performed to compare the measurement data among the groups.Results At 3th and 6th after immunization,PD-L1 blockade stimulated splenic CD_3~+CD_8~+T lymphocytes proliferation more efficiently than that with no PD-L1 blockade(mice with DC/HBsAg treatment alone)(F=25.22 and 39.01,P<0.01),and the secretion of IFNγ WaS hisher(F=32.35 and 36.98.P<0.01);meanwhile the differences between mice with DC/HBsAg treatment and those with DC alone were only observed at 3th(t=6.79,P=0.012).The activity of HBsAg-specific CTL and serum HBsAg levels at 6th were significantly higher in mice with anti-PD-L1 Abs treatment compared with those in other groups (F=6.12,P<0.05).Serum ALT levels in mice with anti-PD-L1 Abs treatment were the same with DC/HBsAg group at 3th,but were higher than those in other groups at both 3th and 6th(F=19.22 and 14.30,P<0.05).All groups were similar in the clearance of HBV DNA.but HBV DNA hvel decreased one log copy in one mouse with anti-PD-L1 Abs treatment.Conclusion Blocking PD-1/PD-L1 interaction can enhance specific CD_3~+CD_8~+ T lymphocyte proliferation and the capability of secreting IFNγ,which improves the inhibition of HBV in transgenic mice induced by HBsAg-pulsed DC vaccine.