In PB specimens, studies found PD-1 expressions on CD4+, CD8+ [75], Vδ2+ T cells [77] and Tregs [66] were upregulated in AML patients upon diagnosed, while others argued that PD-1 upregulation on CD8+ T cells [79] were only limited to relapsed cases. This evidence concerns the gene PDCD1 and acute myeloid leukemia.