ATRA enhances FoxP3 expression independent of Stat3. Peripheral CD4⁺ cells from Stat3^fl/flCD4-Cre mice or WT controls were polyclonally stimulated for 3 days under Th-neutral conditions, Th17 conditions, or with TGF-β1 alone in the presence or absence of 1 μM ATRA. IL-17 and FoxP3 expression was measured on fixed cells by intracellular staining. Data are representative of 2 independent experiments. Numbers on plots are percentages of total cells.