Expression of costimulatory and homing molecules on antigen-specific CD28⁻CD45RA^hi cells before and after stimulation with viral peptide. (A) Replicate cultures of sorted CD28⁻CD45RO⁻ CD8⁺ T cells were stimulated with peptide-pulsed autologous monocytes and harvested at intervals for flow cytometry. Expression of CD137 (at day 5), CD278 (at day 5), and CD28 (at day 7) is shown against peptide-MHC Class I multimer, gated on CD8⁺ T cells. (B) Kinetics of expression of CD137, CD278, and CD28 after peptide stimulation (filled histograms) compared with isotype control (open histograms) gated on total input CD8⁺ cells (day 0) or gated on multimer-positive CD8⁺ T cells (days 5-12). (C) Kinetics of expression of CCR7, CD62L, CCR5, and CXCR3 after peptide stimulation gated on total input CD8⁺ cells (day 0) or gated on multimer-positive CD8⁺ T cells (days 5-12).