Isolation of NP366-374 specific CD8⁺ T cells following stimulation with recombinant vaccinia virus. CFSE-labeled splenocytes (10⁷) were transferred from F5 Rag^−/− to C57BL/6 mice and the recipients infected 24 hours later with 10⁷ PFU recombinant vaccinia virus expressing NP366-374 by intraperitoneal injection. (A) Epitope-specific cells were tracked using CFSE and tetramer-PE. The size of the transferred epitope-specific population is shown as percentage of lymphocytes. (B) CFSE profiles of the transferred CTL population are shown at each time point. (C) Epitope-specific cells were analyzed following infection with recombinant vaccinia expressing the OVA peptide (0-, 24-, 48-, and 96-hour time points are shown). Identical results were seen with sham infection using PBS alone. (D) FACS gave up to approximately 99% purity. All plots show data representative of at least 6 individuals in the “lymphocyte” gate.