IDO expression in AML cells increased CD4⁺CD25⁺Foxp3⁺ T cells. (A-B) Flow cytometry analysis of CD4⁺CD25⁺ T cells before and after culture with AML cells in the presence and absence of 1-MT (1000 μM). Data are expressed as the percentage of CD4⁺CD25⁺ T cells (A) and as CD25 MFI on gated CD4⁺ T cells (B). Results are the mean ± SD of 10 independent experiments. (C) Surface CTLA-4 expression on purified CD4⁺CD25⁺ T cells obtained after culture with IDO-expressing AML cells in the presence and absence of 1-MT. Results are representative of 4 independent experiments. (D) FOXP3 mRNA expression by purified CD4⁺CD25⁺ and CD4⁺CD25⁻ T cells obtained after culture with IDO-expressing AML cells. Total MNCs stimulated with monoclonal antibodies against CD3 and CD28 were used as positive control. Results are representative of 4 independent experiments.