Expression of indoleamine 2,3-dioxygenase in acute myeloid leukemia and the effect of its inhibition on cultured leukemia blast cells.

Indoleamine 2,3-dioxygenase (IDO), a catabolizing enzyme of tryptophan, is a novel immunosuppressive agent blocking T-cell activation in neoplastic cells, including acute myeloid leukemia (AML) cells. IDO inhibitors as 1-methyl tryptophan (1MT) can abrogate IDO enzymatic activity and may result in an effective immune response. Mononuclear cells (MNCs) were separated from peripheral blood of 25 AML patients and 25 normal adults.