To further explore this shift in immunodominance in vivo, 2-day-old or 8-week-old mice were infected with an LD10 dose of PR8 influenza and at day 10 post-infection, lung digest and BAL CD8+ T cells were analyzed for antigen specificity by flow cytometry using tetramers for NP (366–374) and PA (224–233). The gene discussed is CD8A; the disease is infection.