A recent study of gene expression in myelodysplastic syndrome and AML patients demonstrated upregulation of PD-L1 and PD-L2 in leukemia blast, indicating a role for the PD-1 pathway in AML pathogenesis.37 In addition, Norde et al.38 reported that minor histocompatibility antigen-specific T cells expressed elevated PD-1 in a patient during the accelerating phase of chronic myeloid leukemia and a patient with AML post donor lymphocyte infusion. This evidence concerns the gene PDCD1 and leukemia.