In the present review, we present the characteristics of KIR and HLA class I gene polymorphisms, their expression, the KIR/HLA interactions that regulate the NK cell repertoire in healthy individuals, and the relevance of KIR/KIR ligands to NK-cell-based immunotherapies for adult patients with hematological malignancies, especially in the context of allogeneic HSCT. The gene discussed is KIR3DL1; the disease is hematologic disorder.