In vitro hyporesponsiveness of Itgb2^Jkr/Jkr NK cells in mixed BM chimeras. Bone marrow cells from WT (CD45.1⁺; open histograms) or Itgb2^Jkr/Jkr (CD45.2⁺; black histograms) mice were isolated and mixed at an equal ratio before transfer into irradiated WT (CD45.1⁺) recipients. Splenocytes from chimeric mice were analyzed 16-22 weeks after reconstitution. NK-cell IFN-γ production (A) and degranulation (CD107a exposure; B) were tested by flow cytometry after activation and surface and intracellular stainings. The responsiveness of WT (CD45.1 staining) and CD18-deficient (Itgb2^Jkr/Jkr, CD45.2 staining) on stimulation with the tumor YAC-1, NK1.1 monoclonal antibody-coated plates, or PMA/ionomycin was compared after 4 hours of stimulation. Data are expressed as the percentage of IFN-γ⁺ (A) and the percentage of CD107a⁺ (B) in the NK cell gate. n = 7 for each genotype, means ± SEM are shown. Statistical analysis was performed using a one-tailed Mann-Whitney test.