Comparison between natural cytotoxicity mediated by IL-2–activated LAD1 NK cells and normal NK cells against human tumor cell targets. IL-2–activated NK cell populations derived from LAD1 patient 1 (A), LAD1 patient 2 (B), and the representative age-matched healthy donors were analyzed for cytolytic activity against the indicated (FcγR-negative) target cell lines at different E/T ratios. Target cells are of human origin with the exception of murine BW5147 cells. The results are representative of 3 independent experiments; the standard deviation of the mean of the triplicates was less than 5%. Kruskal-Wallis test and Mann-Whitney test were used for statistical analyses of the data showed in panel A and B, respectively.