IL6 and bacterial infectious disease: To better understand the inflammatory milieu in the lung at day 3 post infection, when we observed the SFB-mediated resistance against bacterial infection, we also examined cytokine mRNA expression levels in the lungs including IL-1β, IFNγ, IL-12a, and IL-6, all of which have been demonstrated to be induced in the lungs during S. pneumoniae infection (Bergeron et al., 1998; Mcneela et al., 2010; Supplementary Figure 4).