CD4 and infection: Both primary adjuvanted rGP immunization and LCMV i.n. infection induced small numbers of lung-infiltrating memory I-Ab:gp66-77 tetramer+ CD4+ T cells detected at 39 dpi (S6A–S6C Fig) that were dramatically boosted in frequency and number at 8 days after influenza infection and were significantly higher compared to the PR8(1°) and PR8(1°)PR8(2°) groups (Fig 5A–5B).