PDCD1 and acute myeloid leukemia: Apart from PD-1/PD-L1 and CTLA-4, T-cell immunoglobulin and mucin domain 3 (TIM-3), which physiologically binds galectin-9 (Gal-9), is highly expressed on AML blasts, and plays a major role in immune escape of AML and relapse post allo-HCT [50].