Figure 1. ATRA increased the percentages of Foxp3 expression on TGF-β-primed CD4⁺, but not on CD8⁺ cells.

(A) CD8⁺CD62L⁺CD25⁻Foxp3⁻(GFP⁻) and CD4⁺CD62L⁺CD25⁻Foxp3⁻(GFP⁻) cells isolated from C57BL/6 Foxp3^gfp reporter mice were stimulated with immobilized anti-CD3 (1 μg/ml), soluble anti-CD28 (1 μg/ml), IL-2 (100 U/ml), or TGF-β (2 ng/ml), with (CD4_TGFβ+ATRA or CD8_TGFβ+ATRA) or without ATRA (50 nM) (CD4_TGFβ or CD8_TGFβ) for 3 days. Foxp3 (GFP) expression was examined by flow cytometry. Left: typical FACS histograms. Right: summary of data showing the frequency of Foxp3⁺ cells from TGF-β-primed CD4⁺ or CD8⁺ cells. *P < 0.05, NS. (B) The expression levels of regulatory T-cell associated markers including CD25, GITR, CTLA-4, and TNFR2 on CD4_TGFβ, CD8_TGFβ, CD4_TGFβ+ATRA, or CD8_TGFβ+ATRA cells were analyzed by flow cytometry. The graph data indicate the mean ± sem of 3 separate experiments showing the frequency of the indicated markers gated on the CD4 or CD8 cell populations.