MPO and streptococcal pneumonia: Immune responses supported by mast cell degranulation, including IL-6 and tumor necrosis factor alpha (TNF-α), may impair neutrophil and macrophage bacterial clearance of GBS, as recently observed in Streptococcus pneumoniae lung infection (111), perhaps explaining why neutrophil MPO responses were higher in Camp−/− mice (Fig. 4).