Number of Treg cells per microliter of blood after immunization and administration of denileukin diftitox for cohort 2. Whole blood was stained using BD Bioscience TruCount tubes analyzed by flow cytometry to determine total number of Treg cells per microliter of blood. The data are presented as the mean number of CD4⁺CD25^highFoxp3⁺ cells/μL blood plus or minus SE for 5 patients completing 4 vaccinations for cohort 2. Analysis was performed before each vaccine injection and following the final vaccination, and before each denileukin diftitox infusion.