Expansion of naive and memory p14 T cells in vivo. (A) Naive (1 × 10⁷) p14 splenocytes (•) containing approximately 6 × 10⁶ gp33-specific naive CD8⁺ T cells (Vα2⁺CD45.1^–) or 3.6 × 10⁶ memory p14 splenocytes (▪) containing 2 × 10⁵ gp33-specific memory CD8⁺ T cells (Vα2⁺CD45.1^–) were injected intravenously into imatinib-treated (high-dose 50/100 regimen; filled symbols) and nontreated (open symbols) CD45.1⁺ recipients. Sixteen hours later, the mice were infected intravenously with 10⁴ pfu LCMV. On days 5, 8, and 14 after infection, the number of CD45.1^–CD8⁺ T cells in the spleen was analyzed by flow cytometry. Symbols represent the means ± SEM of 3 to 4 mice per group and time point. (B) The frequencies of IFNγ-, TNFα-, and IL-2–secreting CD45.1^–CD8⁺ T cells were analyzed in the spleen by flow cytometry on day 8 after infection after in vitro restimulation with gp33. Results are given as means ± SEM of 3 to 4 mice per group.