Enhanced clearance of MHCI-deficient target cells by ItpkB^−/− NK cells. (A) MHCI^+/+ or MHCI^−/− splenocytes were labeled with low or high CFSE amounts, respectively. A 1:1 mixture was injected IV into WT versus ItpkB^−/− mice. CFSE^low versus CFSE^high target cell content in recipient spleens was assessed 24 hours later. (B) Statistical analysis of the ratio (± SEM) of WT control to MHCI^−/− targets harvested from recipient spleens (n = 5) revealed significantly underrepresented MHCI^−/− targets in ItpkB^−/− recipients (P = .008, paired t test), indicating increased MHCI^−/− target clearance.