Surface expression of the major triggering receptors and IFN-γ release by LAD1 NK cells. (A) IL-2–activated NK cell populations from LAD1 patients and from representative age-matched healthy donors were stained with monoclonal antibodies specific for the indicated molecules followed by PE-conjugated goat anti–mouse isotype-specific secondary reagent and analyzed by flow cytometry. NK cells represented virtually all purified cells as demonstrated by the homogeneous expression on viable cells of different NK markers including the NK-restricted NCR. White profiles indicate cells incubated with the secondary reagent only. (B) IL-2–activated NK cell populations from LAD1 patient 1 or the representative age-matched healthy donor 1 were stimulated with plate-bound mAbs specific for the indicated molecules. After 24 hours of culture, IFN-γ production was assessed by ELISA. Data represent the mean of 5 independent experiments (standard deviation < 5%).