 (A) Model of post-influenza bacterial infection illustrating infection with sub-lethal dose of influenza virus (25 pfu) followed by sub-lethal dose of secondary bacterial challenge (Streptococcus pneumoniae serotype 19F, 2x105 cfu) 7 days later. Where appropriate, mice lungs were analysed at days 0, 1 and 3 post-secondary bacterial infection, corresponding to days 7, 8 and 10 post-influenza virus infection, respectively 