Figure 3. ATRA enhanced the suppressive activity of CD4⁺ iTregs, but not of CD8⁺ iTregs, in vitro.

(A) CD4_TGFβ, CD8_TGFβ, CD4_TGFβ+ATRA, or CD8_TGFβ+ATRA cells generated as in Fig. 1A were added to cultures of soluble anti-CD3 (0.025 μg/ml), irradiated APCs (1:1), and CFSE-labeled responder T cells for 3 days. Suppressive activity by each cell population was demonstrated and compared by percentages of CFSE-diluted cells. A histogram representative of 3 separate experiments in 1:2 ratios of Treg-to-responder T cells is shown. (B) The same culture as in (A), but the graded ratio of Tregs was added to the culture. The graph shows the mean ± sem of results in 3 independent experiments. *P < 0.05. **P < 0.01.