Cytolytic response of LAD1 NK cells in a redirected killing assay. (A) IL-2–activated NK cell populations derived from the LAD1 patients and from representative age-matched healthy donors were analyzed in a redirected killing assay against the FcγR⁺ P815 murine target cell line either in the absence (white bars) or in the presence of mAbs (IgG isotype) specific for the indicated molecules (black bars). The E/T ratios used were 40:1 and 2:1 for LAD1 patients and healthy donors, respectively. (B) NK cells from LAD1 patient 1 and healthy donor 1 were analyzed in redirected killing assays against the P815 cell line at various E/T ratios. Experiments were performed either in the absence (white circle) or in the presence of a mAb (IgG isotype) specific for CD16 (black circle) (2.5 μg/mL). Mann-Whitney test was used for statistical analysis. (C) IL-2–activated NK cell populations derived from the LAD1 patients and from representative age-matched healthy donors were analyzed for cytolytic activity against the BW5147 murine target cell line either in the absence of mAb (white bar) or in the presence of mAbs (IgM isotype) specific for the indicated molecules (gray bars). The E/T ratios used were 40:1 and 20:1 for LAD1 patients and healthy donors, respectively. (D) NK cells from healthy donor 1 were analyzed for cytolytic activity against the P815 cell line either in the absence of mAb (white bar) or in the presence of mAbs specific for the indicated molecules (black bars) used alone or in combination. mAbs of IgG or IgM isotype were used in order to either trigger or mask the different NK surface molecules, respectively. The E/T ratio used was 2:1. The results are representative of 3 independent experiments; the standard deviation of the mean of the triplicates was less than 5%.