Changes of regulatory T cells in the peripheral blood. Flow cytometry was performed on PBMCs. For details, see “Methods.” Regulatory T cells (Tregs) were defined as CD4, CD25hi, and FoxP3 coexpressing cells. The graph gives the frequency of Tregs as percentage of all CD4⁺ T cells in the respective sample at different time points before, during, and after R3 peptide vaccination in 4 patients.