KIR2DL1 and leukemia: This observation predicts that the NK cell-mediated anti-leukemia effect would be greatest in individuals with HLA-C alleles lacking NK-Pro activity (HLA-C*02, -C*05, -C*07, -C*08, -C*17) and lowest in individuals that possess HLA-C*06 together with the C2-binding KIR2DL1 inhibitory receptor, a factor that may be significant when choosing donors for stem cell transplantation.