Endogenous IL-7 and IL-15 regulate different CD8⁺ T-cell subsets during contraction. (A) OT-I CD8⁺ T cells (10⁵) were adoptively transferred into B6 or IL-15^−/− mice followed by infection with VSV-OVA. Beginning on day 2, mice were treated with anti–IL-7Rα mAb. Percentage maximal response of donor OT-I among PBLs is shown at the indicated time points. (B) Phenotype of donor OT-I CD8⁺ T cells at day 16 in mice treated as in panel A. (C) B6 or IL-15^−/− mice were infected with LM-OVA. Percentage maximal response of tetramer⁺ CD8⁺ T cells is shown. (D) Phenotype of tetramer⁺ T cells on day 16 as shown in panel C. Mice treated with IL-15 complexes from day 7 through day 16 are indicated. (E) OT-I T cells (10⁵) were adoptively transferred into B6 mice followed by infection with LM-OVA. On day 7 of infection, donor T cells were isolated and transferred into secondary B6 or IL-7^−/− hosts. Percentage maximal response of donor OT-I among PBLs are shown at indicated time points. (F) Phenotype of donor OT-I T cells at day 21 as in panel E. All data are representative of 2 independent experiments.