PDCD1 and acute myeloid leukemia: Patients newly diagnosed with AML or those undergoing relapse reported elevated PD-1 levels in peripheral blood (PB) and bone marrow (BM) T cells following front-line treatment, and by contrast, patients in durable remission reported reduced expression levels (Xu et al., 2021a; Brauneck et al., 2021), and TCRβ sequencing revealed clonal expansion in PD-1 positive CD8+ T cells (Feng et al., 2020).