J Bacteriol Virol.  2014 Jun;44(2):121-132. 10.4167/jbv.2014.44.2.121.

The in vivo and in vitro Roles of Epithelial Pattern Recognition Receptors in Pneumococcal Infections

• Shin SG
• Koh SH
• Lim JH

• KMID: 2168687
• DOI: http://doi.org/10.4167/jbv.2014.44.2.121

Abstract

Streptococcus pneumoniae, also called pneumococcus, is a major cause of infectious disease in human. Pneumococcus resides in the nasopharynx as an upper respiratory commensal, and most of pneumococcal colonizations are asymptomatic in immunocompetent individuals. When nasopharyngeal mucosal homeostasis is disrupted, pneumococcus migrates into middle ear and lower respiratory tract and causes detrimental colonization. In this regard, the epithelial cells of middle ear and lung act as first line of defense against pneumococcus to prevent invasive pneumococcal diseases. Respiratory epithelial cells express various cell-surface and intra-cellular receptors sensing microbial pathogens and respond to sensed pathogens by triggering intra-cellular signaling pathways and inducing pathogen-specific innate immune responses. Various epithelial cell-surface and intra-cellular receptors, such as Toll-like receptors (TLRs), Nod-like receptors (NLRs), intracellular DNA sensing receptors, and scavenger receptors (SRs), participate in sensing of pneumococcus, and the activation of these receptors by pneumococcal components induces anti-pneumococcal innate immune responses including epithelial apoptosis and inflammatory cytokine/chemokine expressions. Epithelial sensing of pneumococcus is a critical step for setting an early defense against pneumococcal infection, and also is required to recruit and activate innate immune cells and trigger adaptive immunity.

Keyword

Streptococcus pneumoniae; Pneumococcus; Epithelial cell; Pattern recognition receptor; Inflammation

MeSH Terms

Adaptive Immunity
Apoptosis
Colon
Communicable Diseases
DNA
Ear, Middle
Epithelial Cells
Homeostasis
Humans
Immunity, Innate
Inflammation
Lung
Nasopharynx
Pneumococcal Infections*
Receptors, Pattern Recognition*
Receptors, Scavenger
Respiratory System
Streptococcus pneumoniae
Toll-Like Receptors
DNA
Receptors, Pattern Recognition
Receptors, Scavenger
Toll-Like Receptors

Figure

• 

  Figure 1. Schematic diagram of epithelial sensors for pneumococcus. Abbrs: AP-1 activator protein 1; DAI, DNA-dependent activation of IRF; IRF, Interferon regulatory factor; LTA, lipoteichoic acid; NFκB, nuclear factor kappaB; NOD, Nucleotide-binding oligomerization domain 2; PGN, peptidoglycan; pIgR, polymeric immunoglobulin receptor; PLY, pneumolysin; TLR, Toll-like receptor.

• 

  Figure 2. Overview of regulation of anti-pneumococcal innate immune responses by epithelial PRRs. Abbr: PRRs, pattern recognition receptors.

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