IDO expression correlates with increased CD4⁺CD25⁺Foxp3⁺ T cells in patients with AML. (A) Percentage of circulating CD4⁺CD25⁺ T cells in PB collected from healthy donors and patients with AML at diagnosis. (B) Foxp3 mRNA expression in highly purified CD4⁺ cells obtained from patients with AML. Data are expressed as a percentage of FOXP3⁺ patients. Healthy donors, n = 9; IDO⁺ patients, n = 9; and IDO⁻ patients, n = 12. The data report the mean ± SD of independent experiments.