In the field of hepatitis B virus (HBV)-related diseases, we found that HBV e antigen (HBeAg) seroconversion occurred in the antiviral therapy of chronic hepatitis B patients was closely related to IL-21[5], and the circulating CXCR5+CD4+ T cells benefit HBeAg seroconversion through IL-21 [6]. The gene discussed is IL21; the disease is chronic hepatitis B virus infection.