GP-specific iTreg down-regulated the T cell–stimulating capacity of DCs. GPIIb/IIIa-pulsed DCs were cultured alone (unmodulated DCs) or in the presence of GPIIb/IIIa-specific iTreg or conventional CD4⁺ GPIIb/IIIa-reactive T cells (Tconv) for 2 days. Then T cells were depleted using CD4 magnetic beads, and the isolated iTreg- or Tconv-modulated DCs (2 × 10⁴) or unmodulated DCs (2 × 10⁴) were used to stimulate CFSE-labeled GPIIb/IIIa-reactive T cells at a 1:10 ratio. After 3 days of culture, proliferation was measured as the percentage of proliferating GPIIb/IIIa-reactive T cells by flow cytometry. Results are representative of 16 independent experiments (A) and shown as mean plus or minus SD with error bars representing SD (B).