The most relevant mechanism by which DCs induce Tregs is through the upregulation of indoleamine 2,3-dioxygenase 1 (IDO1) (15–18), an enzyme that degrades the essential amino acid tryptophan into kynurenine and is involved in the generation of an immunosuppressive microenvironment in AML (19, 20). The gene discussed is IDO1; the disease is acute myeloid leukemia.