Understanding the basis for specificity in KIR binding to HLA-C allotypes is also relevant to hematopoietic stem cell transplantation for the treatment of certain leukemias, as the clinical outcome is improved when donor KIR and recipient HLA-C genes are mismatched according to the C1–C2 model for KIR specificity (16–18). The gene discussed is HLA-C; the disease is leukemia.