CD244 and acute myeloid leukemia: When we further analyzed co-expression with CD244 and CD57, higher percentages of PD-1 + CD244 + CD3+ and PD-1 + CD244 + CD8+ T cells were also found in the BM group, indicating that PD-1 is frequently co-expressed with the exhausted phenotype on T cells and may be influenced by the AML BM microenvironment, particularly on CD8+ T cells.