Quantification of surface antigen expression on human NK subsets defined by CD56 and CD94. Peripheral blood NK cells were enriched to purity 50% to 85% using RosetteSep cocktail and then stained with anti-CD3, anti-CD56, and anti-CD94–conjugated mAb, as well as a mAb directed against the surface antigens indicated in each histogram. Each of the 3 gated populations (CD94^highCD56^bright, CD94^highCD56^dim, and CD94^lowCD56^dim) was then assessed for positivity for surface expression of the fourth antigen as shown compared with its isotype control (not shown). The number in each histogram shows the percentage of cells that are positive for the indicated antigen(s), and is averaged from at least 3 different normal donors.