CD34 and leukemia: 2. NK cells in haplo-HSCT to cure high-risk leukemia - Transplant of “pure” donor CD34+ cells. NKG2A+ NK cells are detectable after 2 weeks, while KIR+, cytolytic NK cells only after 6–8 weeks. Central role of NK cells in GvL, especially of “alloreactive” NK cells (13, 14); - Transplant of αβT- and B cell-depleted mononuclear cells. Donor NK cells and γδT cells, being present in the graft, are immediately available for the control of infections and leukemia relapses. Better clinical outcome, particularly in AML (15–19).