Activation of and signaling through Akt is required for CD8 memory cell formation in vivo. (A,B) Naive WT clone 4 CD8⁺ T cells were transduced with retroviral constructs encoding GFP only (empty) as a control or GFP coupled with a dominant-negative form of Akt (dnAkt). The transduced cells were sorted, and 3 × 10³ GFP⁺CD8⁺ (Thy1.1⁺) T cells were transferred into B10.D2 recipients (Thy1.2⁺), which were then vaccinated with 5 × 10⁵ pfu rVV-HA intraperitoneally. At 42 days later, mice were boosted with 2 × 10⁹ pfu Ad-HA intraperitoneally. Seven days after infection, splenocytes were analyzed for the expansion of clonotypic T cells and their function by IFN-γ intracellular staining. (A) The percentages of clonotypic T cells among total lymphocytes (top) and IFN-γ–producing clonotypic T cells among total CD8⁺ T cells (bottom) are indicated. (B) The absolute cell numbers per spleen of CD8⁺Thy1.1⁺ clonotypic T cells in both empty vector and dnAkt groups with SDs are indicated (n = 4 per group). Empty versus dnAkt, P < .001. Data shown are representative of 3 independent experiments.