Th17 cells express high levels of RARα, RARγ, and RORγt mRNA. (A,B) CD4⁺CD62L⁺ cells isolated by MACS were polyclonally stimulated for 3 days under Th-neutral, Th1, Th2, or Th17 conditions. Relative expression of RAR and RXR receptors was analyzed by quantitative RT-PCR. Expression is normalized to β-actin levels under Th-neutral conditions, and error bars represent standard deviation (n = 3). Detected RAR and RXR receptors are shown (RAR-β and RXR-γ were not present). (C) Naive CD4⁺ T cells were polyclonally stimulated for 3 days under Th-neutral or Th17 conditions in the presence or absence of 1 μM ATRA. Relative expression of RORγt mRNA was analyzed by quantitative RT-PCR. Expression is normalized to β-actin levels and relative to Th-neutral conditions; error bars represent standard deviation (n = 3). The inhibition of RORγt mRNA was confirmed in 3 independent experiments.