Recombinant IL-2 regulates FOXP3 expression in CD4⁺CD25⁺ Tregs. (A) CD4⁺CD25^- (▪) and CD4⁺CD25⁺ () T cells purified from healthy individuals were cultured for 6 hours in the presence of recombinant IL-2 with or without anti-CD3 stimulation. FOXP3 expression was then assessed by quantitative PCR. (B) Purified CD4⁺CD25^- and CD4⁺CD25⁺ cells were cultured for 18 hours with or without IL-2. Levels of FOXP3 protein were subsequently assessed by Western blotting. Control blotting of α-tubulin is also shown in this figure. (C) Purified CD4⁺CD25^- (□) or CD4⁺CD25⁺ (○) cells were cultured for 6 hours with varying concentrations of IL-2 and then assessed for FOXP3 expression by quantitative PCR.