Frequency of intrahepatic FoxP3+ regulatory T cells during the natural course of chronic hepatitis B: An immunohistochemical study using needle-biopsied liver tissue

Background: Regulatory T cells (Tregs) may contribute to the immunological hyporesponsiveness against hepatitis B virus (HBV), and this can result in chronic infection. Tregs suppress the T cell responses directed against HBV and they protect hepatocytes by down-regulating the immune responses that cause liver damage, but the role of Tregs has not been well characterized. Methods: Fifty four patients were selected and classified into three groups (12 were in the immune-tolerance phase, 35 were in the immune-clearance phase and 7 were in the asymptomatic virus carrier phase). We examined the frequency of CD3+, CD4+ & CD8+ T cells and forkhead box P3 (FoxP3)+ Tregs in the needle-biopsied liver tissue by performing immunohistochemistry. Results: The FoxP3+ Tregs were mainly located at the portal tracts. In the immune-clearance phase, the frequency of FoxP3+ Tregs was significantly increased compared to that of the immune-tolerance group and the asymptomatic carrier group. Increased FoxP3+ T cells were observed in the patients with a higher histologic inflammatory index. No correlation was observed among the numbers of FoxP3+ Tregs, the serum alanine aminotransferase level, detection of HBeAg and the HBV-DNA viral load. Conclusions: FoxP3+ Tregs may play important roles in suppressing the immune response to HBV and the complete elimination of HBV.