B220⁺ NK cells are highly cycling relative to mNK cells. (A) The mean percentage of BrdU incorporation on continuous labeling is shown for B220⁺, CD27⁺, and CD27⁻ NK-cell subsets. One of 3 representative experiments is shown, with 4 mice/group. (B) Cell size is depicted in the histogram for sorted B220⁺, CD27⁺, and CD27⁻ NK cells. The mean FSC-A is indicated for each NK-cell subset. Results are representative of ≥ 3 experiments.