Purification of human NK cell subsets.

CD56^bright and CD56^dim NK cell subsets were FACS-purified from fresh peripheral blood lymphocytes. Flow cytometric analysis of CD56-PE (A) and CD56-PE/CD16-FITC expression before (B) and after (C) FACS purification of a representative donor is shown, and the percentages of cells are indicated in the upper right quadrant. (A) Gating on total peripheral blood lymphocytes; 12.8% of unpurified lymphocytes were CD56⁺, and (B) 11.8% were positive for both CD56 and CD16. (C) Purified CD56^bright and CD56^dim NK cell subsets were more than 98% pure, as shown by flow cytometry analysis of CD56 and CD16. Of CD56^brightcells, 51.5% expressed CD16 at low levels (mean fluorescence intensity [MFI] 49.2), whereas 98% of CD56^dim cells had high expression of CD16 (MFI 213.9). NK cell subsets were gated on total viable cells (more than 98% of all collected events).