FIG 3.

Immunization induces polyfunctional secondary effector CD8 T cells. Prime-boost-immunized mice were rested for 42 to 45 days and then challenged with a lethal dose (5 × 10⁴ PFU) of MA15 (i.n.). Lungs and BAL were harvested 5 days postchallenge, and the percentage and number of epitope-specific CD8 T cells were determined. (A and B) The bar graphs show mean percentages (A) and numbers (B) of S436- and S525-specific IFN-γ⁺ CD8 T cells (after direct ex vivo stimulation with respective peptides) in the BAL and lungs 5 days after MA15 challenge. (C) IFN-γ⁺ CD8 T cells were further gated for TNF-α and IL-2 expression to determine polyfunctionality in the BAL and lungs. Data are representative of 3 independent experiments with 3 or 4 mice/group. *, P < 0.05; **, P < 0.01; ***, P < 0.001 (by unpaired two-tailed Student's t test).