It has been well demonstrated that in haplo-HSCT for high-risk acute myeloid and lymphoid leukemia, donor-derived alloreactive NK cells play a crucial role in the GvL effect due to KIR–HLA mismatches between donor and patient and the consequent lack of NK inhibition by KIR ligands [29,30,265,266]. Here, KIR3DL1 is linked to lymphoid leukemia.