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Toll-like receptor stimulation enhances phagocytosis and intracellular killing of nonencapsulated and encapsulated Streptococcus pneumoniae by murine microglia.

Department of Geriatrics, Evang. Krankenhaus Göttingen-Weende, An der Lutter 24, D-37075 Göttingen, Germany.
Infection and immunity (Impact Factor: 4.16). 11/2009; 78(2):865-71. DOI: 10.1128/IAI.01110-09
Source: PubMed

ABSTRACT Toll-like receptors (TLRs) are crucial pattern recognition receptors in innate immunity that are expressed in microglia, the resident macrophages of the brain. TLR2, -4, and -9 are important in the responses against Streptococcus pneumoniae, the most common agent causing bacterial meningitis beyond the neonatal period. Murine microglial cultures were stimulated with agonists for TLR1/2 (Pam(3)CSK(4)), TLR4 (lipopolysaccharide), and TLR9 (CpG oligodeoxynucleotide) for 24 h and then exposed to either the encapsulated D39 (serotype 2) or the nonencapsulated R6 strain of S. pneumoniae. After stimulation, the levels of interleukin-6 and CCL5 (RANTES [regulated upon activation normal T-cell expressed and secreted]) were increased, confirming microglial activation. The TLR1/2, -4, and -9 agonist-stimulated microglia ingested significantly more bacteria than unstimulated cells (P < 0.05). The presence of cytochalasin D, an inhibitor of actin polymerizaton, blocked >90% of phagocytosis. Along with an increased phagocytic activity, the intracellular bacterial killing was also increased in TLR-stimulated cells compared to unstimulated cells. Together, our data suggest that microglial stimulation by these TLRs may increase the resistance of the brain against pneumococcal infections.

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Available from: Sven Hammerschmidt, Jun 17, 2015
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