Spontaneous and natural cytotoxicity receptor‐mediated cytotoxicity are effector functions of distinct natural killer subsets in hepatitis C virus‐infected chimpanzees

Summary In humans, CD16 and CD56 are used to identify functionally distinct natural killer (NK) subsets. Due to ubiquitous CD56 expression, this marker cannot be used to distinguish between NK cell subsets in chimpanzees. Therefore, functional analysis of distinct NK subsets during hepatitis C virus (HCV) infection has never been performed in these animals. In the present study an alternative strategy was used to identify four distinct NK subsets on the basis of the expression of CD16 and CD94. The expression of activating and inhibiting surface receptors showed that these subsets resemble human NK subsets. CD107 expression was used to determine degranulation of the different subsets in naive and HCV‐infected chimpanzees. In HCV‐infected chimpanzees increased spontaneous cytotoxicity was observed in CD94 high/dim CD16 pos and CD94 low CD16 pos subsets. By contrast, increased natural cytotoxicity receptor (NCR)‐ mediated degranulation after NKp30 and NKp44 triggering was demonstrated in the CD94 dim CD16 neg subset. Our findings suggest that spontaneous and NCR‐mediated cytotoxicity are effector functions of distinct NK subsets in HCV‐infected chimpanzees.