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. Author manuscript; available in PMC: 2018 Dec 1.
Published in final edited form as: Nat Rev Microbiol. 2018 Jun;16(6):355–367. doi: 10.1038/s41579-018-0001-8

Fig. 2. bacterial and host factors affecting pneumococcal shedding from carriers.

Fig. 2

Streptococcus pneumoniae is found predominantly in the mucus layer overlying the epithelial surface of the upper respiratory tract. Inflammation (indicated by the presence of neutrophils), which is induced by the pore-forming toxin pneumolysin or by co-infection with influenza virus or other respiratory viruses, stimulates secretions and increases shedding. By contrast, agglutinating antibodies such as anti-capsule immunoglobulin G (IgG) and IgA1 decrease shedding unless they are cleaved by the human IgA1-specific pneumococcal protease. Capsule type and amount also influence mucus association and numbers of shed bacteria.