Contribution of PD-1 and its ligand to immune tolerance in chronic hepatitis B

Hepatitis B virus(HBV) infection is easily becoming chronic. It has been accepted that the major mechanism is the immune tolerance of the host to the antigens of HBV. Programmed death-1 (PD-1) is one of the negative co-stimulate molecules found recently,Its Iigands (PD-L1 and PD-L2) belong to CD28/B7 family. This pathway can provide inhibitory signals that can regulate the fine-tuning, inhibition and activation of T-cell and antigen presenting cells (APC) responses. It plays an important role in the mechanism of immune tolerance in chronic hepatitis B. Key words: Hepatitis B virus;  Programmed death-1;  Programmed death-L;  Immune tolerance