The following day the mice were infected with influenza virus and on day 12 post infection (p.i.)the responding CD8 T cells were tested for reactivity to a panel of five MHC class I influenza-specific epitopes from the viral proteins - nucleoprotein (NP366/Db), acid polymerase (PA224/Db), basic polymerase I (PB1703/Kb), the F2 of PB1 (PB1 F262 /Db) and non-structural protein 2 (NS2114/Kb) Fig. 1a. Here, CD8A is linked to infection.