PDCD1 and acute myeloid leukemia: Another checkpoint, KLRG-1 was reported to be involved in AML relapses post allo-HCT by Hutten et al.; importantly this study highlighted the simultaneous expression of multiple inhibitory checkpoints (PD-1/TIGIT/KLRG-1) on antigen specific CD8 T-cells of the PB as a key feature of T-cell dysfunction [48].