Fig. 3.

Vaccination recalls influenza virus-specific CD4⁺ and CD8⁺ T-cell responses after H3N2 challenge. Groups of BALB/c mice were vaccinated (two doses) with the respective vaccine agents or PBS and challenged with 40 LD₅₀ H3N2 virus 2 wk later. At day 7 postchallenge, influenza-specific CD4⁺ and CD8⁺ T-cell responses were measured by IFN-γ ICS assay after ex vivo stimulation with H5N2 virus. T-cell responses in BAL (A), mLN (B), and spleen (C) are shown. Cells were gated on FSC/SSC, CD4⁺ or CD8⁺, IFN-γ⁺. Data represent mean ± SD; n = 3–5; ^#P < 0.05, *P < 0.01, ^##P < 0.005, **P < 0.001; experiments were repeated at least twice.