A) Representative histograms showing CFSE dilution and peak identification of NK cells that had (solid, thick line) or had not (dashed line) divided. B) Representative histograms showing relative expression of KLRG1, CD27, and Sca-1 on splenic NK cells that had (solid line) or had not divided (dashed line). C) Proportion of NK cells that had (■, solid line) or had not divided (◇, dashed line) that expressed KLRG1 (left), CD27 (middle), or Sca-1 (right) following 72 h of culture in 3, 20 or 50 ng/mL of IL-15. Data is composite of 2–3 independent experiments with pooled triplicates.