Induction of regulatory T cells by MDSCs is RA dependent. CD4⁺ T cells were stimulated with anti-CD3/CD28/CD2–coated beads and cocultured in the absence or presence of CD14⁺HLA-DR^−/low or CD14⁺HLA-DR⁺ cells. As indicated atRA (A,E), AM580 (B,F), LE540 (C,G), or A7980 (D,H) was added to the cocultures at various concentrations. ICS for IL-17 and Foxp3 was performed after 3 days gating on CD4⁺ T cells. Shown are representative dot plots from 4 (A,C) or 2 (B,D) independent experiments. Numbers represent percentages of events within the respective quadrants. (E-H) Results from single experiments using CD14⁺HLA-DR^−/low cells were plotted as bars gating on CD4⁺ T cells (*P < .05; n.s. indicates not significant).