CSF2 and pneumococcal infection: The role of intestinal microbiota on lung susceptibility to pneumococcal infection also warrants further investigation in humans as murine studies suggest that Nod-stimulating microbiota in the gut induce GMCSF-dependent immunity, which influences alveolar macrophage function during pneumococcal infection (Schuijt et al., 2016; Brown et al., 2017).