Leukemic cells trigger PARP-1–dependent T-cell and NK-cells apoptosis. Bars show the percentage of apoptosis ± SEM. (A) CD4⁺ T cells (n = 3), (B) CD8⁺ T cells (n = 3), and (C) NK cells (n = 5) after overnight incubation with FACS-sorted mature malignant FAB-M4/M5 AML cells in the presence or absence of the NADPH oxidase inhibitor DPI (3μM), catalase (200 U/mL), or the PARP-1 inhibitor PJ34 (0.5μM). For T cells, the AML to T-cell ratio was 1:1, whereas the lowest AML to NK-cell ratio to reach 50% NK-cell apoptosis is presented (range, 1:8-1:2).