Time course of CD45RA, CCR7, and CD25 surface expression after antigenic stimulation. The surface expressions of CD45RA and CCR7 were already shown in Figures 2A and 3A. CD25 surface expression was evaluated on samples collected from the cocultures at different time points. Cells were labeled with an APC-conjugated anti-CD8 antibody and either a PE-conjugated anti-CD25 antibody or a control isotype-matched antibody. Surface expression of these 3 markers is indicated as a percentage of the highest MFI, which was 318 for CD45RA, 28 for CCR7, and 789 for CD25.