Activation of natural Tregs in the presence of Tregitope. Human PBMC were stimulated directly in vitro for 4 days in the presence of tetanus toxin peptide (TT830-844), Tregitope, or no stimulus. A. Cells were stained extracellularly with anti-CD4 and anti-CD25 and intracellularly with FoxP3 and analyzed by flow cytometry. Incubation with Tregitope increased the percentage of CD4⁺CD25⁺FoxP3⁺ T cells (54%) compared to TT830-844 (13%) or no stimulus (20%). Numbers in boxes are the percentage of cells in that gate. B. From top to bottom, FoxP3 expression is shown in PBMC from the same subject following incubation with Tetanus toxin epitope (13%); hTregitope 289 (54%) and no stimulus (20%).