Involvement of the major triggering receptors in the recognition of different human tumor cell lines by LAD1 NK cells. (A) IL-2–activated NK cell populations derived from LAD1 patient 1 and healthy donor 1 were analyzed for cytolytic activity against the indicated (FcγR-negative) target cell lines either in the absence (white bar) or in the presence of the mAbs specific for the indicated molecules (black bars). The E/T ratios used were 20:1 (LAD1 patient) and 5:1 and 1:1 (healthy donor) for M14 and DAUDI cell lines, respectively; 10:1 (LAD1 patient) for MEL15 and HeLa tumor cells. The results are representative of 3 independent experiments; the standard deviation of the mean of the triplicates was less than 5%. The chi-square test was used for statistical analysis. (B) IL-2–activated NK cell populations from LAD1 patients and age-matched healthy donors were cocultured with the representative HTLA230 (human) target cell lines, either in the absence or in the presence of mAbs (IgM isotype) specific for the indicated molecules. After 24 hours of coculture, IFN-γ production was assessed by ELISA. The IFN-γ production by effector or target cells alone was below the limit of detection of the assay. The NK/HTLA230 ratio used was 1:1. Data represent the mean of 3 independent experiments (standard deviation < 5%).