However, conflicting data emerged in registry-based studies of patients with acute myeloid leukemia (AML) (20) and patients with myelodysplastic syndrome (MDS) or secondary AML (21), illustrating the limitation of the current understanding of NK cell-mediated alloreactivity and the need for improvement in current KIR ligand modeling systems. This evidence concerns the gene KIR3DL1 and myelodysplastic syndrome.