NK-cell subsets differentially express surface antigens. PBMCs were stained with anti-CD56, anti-CD3, a cocktail of NKG2A and KIR antibodies, and FITC-conjugated antibodies against CD2, 16, 44, 62L, 94, and 161. NK-cell subsets were gated on the expression of CD56, and on the presence or absence of NKG2A and KIR. Shown are representative histograms (n = 5-11) for the surface antigens indicated. To facilitate comparison of antigen density, a vertical line (designated by a downward arrow above the CD56^bright plots) is drawn through the approximate mean channel fluorescence of the subpopulation of CD56^dim cells expressing NKG2A and/or KIR.