Immunoadjuvant effects of IL-15 and IL-2 on NK cell cytotoxicity and ADCC against neuroblastoma. A, NK cells were prestimulated with several concentrations of IL-2 and IL-15 for 24 hours and subsequently tested with the PDX SJNBL046_X at different E:T ratios. The assays were conducted with NK cells from two donors, with and without hu14.18K322A. All experiments were performed in technical quadruplets and mean tumor lysis and standard deviation were plotted. Tumor lysis by IL-15-activated NK cells was significantly greater than that of IL-2-activated NK cells, except in the marked conditions (NS). B and C, NK cells from four donors were tested against the two PDX lines PDX SJNBL046_X (B) and SJNBL047443_X1 (C), with an E:T ratio of 5:1 and intermediate concentrations of IL-2 (10 IU/mL) and IL-15 (5 ng/mL). IL-15–preactivated NK cells induced higher cytolysis when directly compared with that of IL-2–activated NK cells. This was noted in presence and absence of an anti-GD2 antibody. Exceptions are marked accordingly (NS).