IL-2 is transiently induced following peptide stimulation but is not induced by IL-12 and IL-18. Spleen cells from mice at day 8 (A,C) and day greater than 200 (B,D) after infection were activated as in Figure 2. IFNγ and IL-2 were detected by intracellular staining. Dotplots (A-B) are gated on CD8⁺ cells and show IFNγ and IL-2 produced after 1, 3, and 8 hours of direct ex vivo stimulation with peptide or IL-12 plus IL-18 in the presence of BFA for the last hour, or 8 hours of peptide stimulation with continuous BFA (8/8 h BFA). Graphs (C-D) show the percentage of CD8⁺ T cells producing IL-2 at each time interval. Values are averages ± SDs (n = 4 day 8, n = 8 day > 200). (E) The relative rates of IL-2 production by day 8 and day greater than 200 (immune) CD8⁺ T cells are represented as the percentage of maximum IL-2 response at each time interval, with 100% maximum at 3 hours.