Fig. 1.

Wild-type and T-Mtor^−/− mice were sacrifi ced. Spleens were harvested and subjected to CD4 purifi cation by magnetic sorting. 2 × 10⁶ CD4 cells were injected intravenously into C57/BL6 host mice previously immunized with 2 × 10⁶ PFU Vaccinia-OVA. Four days post transfer, host mice were sacrifi ced, and splenic cells were rechallenged with 50 μ g/mL OVA peptide overnight in the presence of a protein transport inhibitor. Splenocytes were then stained for Thy1.1 (upper panels) and intracellularly stained for IL-4 and IFN-γ to assess cytokine production (lower panels, gated on Thy1.1+ cells). Wild-type cells produce copious amounts of IFN-γ upon rechallenge, indicating that they have differentiated into Th1 cells. Cells deficient in mTOR fail to produce either cytokines when restimulated.