Phenotype of NK cells exposed to RMA-H60. (A) Histograms show the expression of the indicated activation receptors or the forward size scatter (FSC) of control RMA- (open histogram) and RMA-H60-exposed (gray shaded histogram) NK cells. Numbers indicate the mean fluorescence intensity (MFI) of staining. The dotted line depicts the FSC of fresh splenic NK cells. These results are from one representative experiment of 6 performed. (B) Bar graphs show the mean MFI (±SD) of NKG2D staining normalized to that of NK cells cocultured with control RMA cells (□, RMA; ▦, RMA-H60) for 3 days. Data for ex vivo-isolated NK cells (▨; n = 8) and for the 72-hour time point (n = 12) are compiled from numerous independent experiments, whereas individual values (circles) and their means (bars) from 2 independent experiments are shown for 24 hours and 48 hours of coculture. Statistical significance of the difference at 72 hours of coculture was evaluated using the one-tailed unpaired Student t test; ^*P < .001.