The mechanism by which the host immune system develops immune tolerance to HBV is unknown, but previous research showed that the numbers and proportions of immunosuppressive cells, particularly Tregs and myeloid-derived suppressor cells, are significantly increased in patients with chronic hepatitis B. This increase in immunosuppressive cells impedes the anti-HBV responses, notably by reducing the availability of the specific CD8+ T cells that produce IFN-γ. This evidence concerns the gene IFNG and chronic hepatitis B virus infection.