(A) WT and Ccr7^–/– mice were infected with 10⁷ PFUs of PR8-OTI virus. Forty-eight hours later, MLN cells were cocultured with CFSE-labeled CD8⁺ OT-I T cells for 3 days. Proliferation was measured by flow cytometry assessment of CFSE dilution (representative histograms). Graph represents the number of divided T cells per well. Each dot represents 1 mouse. (B) WT mice were infected with 10⁷ PFUs of PR8-OTI virus. Lung migratory CD103⁺ DCs and CD11b⁺ DCs and LN-resident CD8⁺ and CD4⁺ DCs purified from the MLN 24 hours after infection were cocultured with CFSE-labeled CD8⁺ OT-I T cells for 3 days. Proliferation was measured by flow cytometry assessment of CFSE dilution (representative histograms). Graph represents the number of divided T cells per well after coculture with different numbers of DCs per well (DC:T ratio). Data are representative of 3 separate experiments. (C) CD45⁺CD11c⁺MHCII⁺ lung phagocyte populations (CD103⁺ DCs, CD11b⁺ DCs, and CD103^–CD11b^– alveolar macrophages) were analyzed by flow cytometry in naive WT and Batf3^–/– mice. Representative percentages of each population in the CD45⁺CD11c⁺MHCII⁺ gate are noted. (D and E) WT and Batf3^–/– mice were infected with 3 × 10³ PFUs of NS1-GFP virus. Seven days later, the percentages and absolute numbers of NP-specific endogenous CD8⁺ T cells in the MLNs (D) and the lungs (E) were measured by flow cytometry using H2D^b/ASNENMETM-specific dextramer staining. Graphs represent the percentage (%) and the absolute numbers (abs no.) of dextramer-positive CD8⁺ T cells among total CD3⁺CD8⁺B220^– T cells. Data are representative of 3 separate experiments.