In 57 refractory AML patients, the expansion of haploidentical NK cells was greater in 15 patients that received host regulatory T cell-depleted IL-2 diphtheria fusion protein (IL2DT) following cyclophosphamide and fludarabine than in patients who did not receive IL2DT (27% vs. 10%). This evidence concerns the gene IL2 and acute myeloid leukemia.