Expression and significance of programmed death 1 in T cell in peripheral blood of patients with chronic hepatitis B during the immune clearance phase

Objective To test feature of PD-1 expression and the effect of PD-1 expression on viral load and biochemical feature of chronic hepatitis B(CHB) patients in immune clearance phase.Methods Forty-five CHB with increased ALT were enrolled.PD-1 expression in total peripheral CD8+ and CD4+ T cell were evaluated by flow cytometry.Immunostaining was performed according to the EnVision ChemMate methods to determine PD-L1 expression.Results It was found that in CHB patients in immune clearance phase the percentage of total peripheral CD8+ T and CD4+ T cells with positive PD-1 expression was elevated compared with those in the healthy control.A similar pattern was observed for the mean fluorescence intensity(MFI) of PD-1 expression on these CD8+ T and CD4+ T cells in serum.Neither of the percentage of PD-1 positive and the density of PD-1 expression per cell were correlated with viral load.In contrast to the viral load,both ALT level and total bilirubin were correlated with the MFI of PD-1 expression on total CD8+T cells significantly.PD-L1 was upregulated on hepatocytes infected HBV,and positively correlated with the severity of liver inflammation and fibrosis.Conclusion The level of PD-1 expression per cell rather than the presence or absence of PD-1 plays important role in regulating the immune-host interaction in CHB patients in immune clearance phase.And the MFI of PD-1 was correlated with high inflammatory reaction rather than the viral load.