IDO1 and acute myeloid leukemia: Since NK cells are the main cell population expressing TIM-3 in response to cytokine stimulation and as the engagement of TIM-3 with Gal-9 ligand induces significant increase in IFNγ production by NK cells [4], we speculated that TIM-3/Gal-9 interaction in BM could be responsible of IDO1 induction in AML blasts and could contribute to mediate the consequent immune escape mechanism.