IDO1 inhibition reduces the conversion of CD4⁺Foxp3⁻ T cells to CD4⁺Foxp3⁺ T_reg-like cells. Primary human CD4⁺ CD25⁻ T cells were cultured in the presence of IDO⁺ human DCs, 100 U/mL IL-2, and 1μM INCB024360 or 500μM L-1MT for 6 days. Cells were costained for CD4 and Foxp3 expression. (A) A representative plot of FACS analysis is presented. (B) Average values of 3 independent experiments are shown in the graph. Error bars represent SD.