Decreased NK cell frequency in chronic hepatitis C does not affect ex vivo cytolytic killing

Prior studies have suggested that natural killer (NK) cell function might be impaired in chronic hepatitis C virus (HCV) infection. Circulating NK cell frequency and cytolytic activity were examined freshly ex vivo in HCV-infected and uninfected subjects. Surprisingly, the intrinsic cytolytic activity of peripheral blood NK-enriched cells was similar between HCV-infected and uninfected groups (P =.91). Although the percentage of circulating CD3(-)CD16/56(+) NK cells was 30% lower in HCV-infected compared with uninfected subjects (P =.02) paralleled by a decrease of CD56(dim) cytolytic NK cells (P =.02), overall K562 cytolysis by unfractionated peripheral blood mononuclear cells was not affected (P =.29). Analysis of the relationships between NK cytolytic activity and other clinical information revealed an inverse association with liver fibrosis stage (P =.035). In conclusion, NK cell cytolytic function does not appear to be impaired in chronic hepatitis C, but higher levels of NK cell cytolysis are associated with less liver fibrosis.