PPIB and influenza: Among the immunological parameters assessed, we found that influenza-induced levels of the antiviral cytokines IFNα, -β and -λ in bronchioalveolar lavage (BAL) fluid were markedly higher in susceptible 129 than in resistant B6 mice at most time points post infection for all influenza strains tested (Fig. 1b, Supplementary Fig. 2a).