KLRK1 and chronic hepatitis B virus infection: In conclusion, our study shown that NK cells, at least in this group of patients with chronic hepatitis B was immune tolerant, especially in patients at IA stage, which characterized by the reduced cytotoxicity, the down regulated expression of IFN-γ and TNF-α, along with the decreased expression of activating receptors of NKp30 and NKG2D.