IL-15Rα–Fc administration results in reduced IAV-specific CD8 T cell responses and increased CD8 T cell apoptosis in the lungs after IAV infection. Groups of BALB/c mice were infected with a sublethal dose of IAV. On days 3, 4, and 5 p.i., mice were i.n. administered IL-15Rα–Fc (black bars) or control human Fc fragments (white bars). On day 6 p.i., the lungs were analyzed for (A) the frequency and (C) number of tetramer⁺ CD8 T cells or (B and D) for apoptosis of tetramer⁺ CD8 T cells. Representative FACS plots are gated on (A) CD3⁺CD8⁺ T cells or (B) CD3⁺CD8⁺tetramer⁺ T cells. Numbers of tetramer⁺ CD8 T cells in the lungs were determined by subtracting background staining using the media control (A, left). Data are representative of two separate experiments and represent means ± SEM (n = 3–5 mice/group).