Recent research has demonstrated that TLR9 may be involved in the development of chronic hepatitis B.[25] Xu et al found that patients with chronic hepatitis B have lower TLR9 mRNA expression than normal individuals in peripheral blood mononuclear cells.[26] HBV might inhibit the mRNA expression of TLR9 in the peripheral blood mononuclear cells (PBMCs) of patients with chronic hepatitis B as a certain starter factor, causing immune escape or immune tolerance. The gene discussed is TLR9; the disease is chronic hepatitis B virus infection.