Abstract: Objective To investigate the involvement of Interleukin-21 (IL-21) in the immune response of individuals with HBeAg positive chronic Hepatitis B (CHB). Methods 45 HBeAg-positive CHB patients, 20 CHB patients in the immune tolerant (IT) phase, and 20 HBeAg-negative CHB patients in the inactive carrier (IC) phase were enrolled in this study. Levels of HBV serum markers, such as HBeAg, HBsAg, Anti-HBs、Anti-HBe、Anti-HBc, as well as ALT, HBV DNA levels, IL-21 cocentration, frequencies of IL-21⁺CD4⁺T cells, and frequencies of IL-21R⁺CD4⁺T cells were assessed before and after 48 weeks of antiviral therapy. Additionally, 15 healthy volunteers were included as a control group and were assessed during the same period. Results The serum concentration of IL-21 in the CHB group (82.21±22.32 pg/mL) and IC groups (72.32±25.26 pg/mL) was significantly higher compared to IT group (20.24±15.56 pg/mL, P<0.001). The frequency of IL-21⁺CD4⁺T cells (7.42±2.34)% and IL-21R⁺CD4⁺T cells (6.46±1.55)% in the IC group was higher compared to the CHB group (P<0.001). No correlation was observed between serum ALT levels and IL-21 concentration (r=0.136, P=0.20). Furthermore, the IL-21 level (92.58±25.76 pg/mL), as well as the frequency of IL-21⁺CD4⁺T cells (7.89±2.05)% and IL-21R⁺CD4⁺T cells (7.01±1.51)%, were significantly higher in the peripheral blood of HBeAg-positive CHB patients who achieved HBeAg serologic conversion after antiviral therapy compared to those who did not (P<0.01). Conclusion IL-21 plays a significant role in the immunopathogenesis of HBeAg-positive chronic hepatitis B.

Key words: Chronic hepatitis B, IL-21, Immunity