Dectin-2-dependent host defense in mice infected with serotype 3 Streptococcus pneumoniae

Yukiko Akahori, Tomomitsu Miyasaka, Masahiko Toyama, Ikumi Matsumoto, Anna Miyahara, Tong Zong, Keiko Ishii, Yuki Kinjo, Yoshitsugu Miyazaki, Shinobu Saijo, Yoichiro Iwakura, Kazuyoshi Kawakami

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7 Citations (Scopus)

Abstract

Background: Streptococcus pneumoniae, a major causative bacterial pathogen of community-acquired pneumonia, possesses a thick polysaccharide capsule. Host defense against this bacterium is mediated by activation of innate immune cells that sense bacterial components. Recently, C-type lectin receptors (CLRs) have garnered much attention in elucidating the recognition mechanism of pathogen-derived polysaccharides. Methods: In the present study, we first compared the clinical course and neutrophil accumulation in the lungs of Dectin-2 knock-out (KO) and wild type (WT) mice. Mice were infected intratracheally with a serotype 3 strain of S. pneumoniae, and S. pneumoniae bacterial engulfment by neutrophils and inflammatory cytokine and anti-pneumococcal polysaccharide-specific IgG levels were evaluated in bronchoalveolar lavage fluid (BALF). We also examined the effect of Dectin-2 deficiency on interleukin (IL)-12 production by bone marrow-derived dendritic cells (BM-DCs) stimulated with the bacterial components. Results: S. pneumonia-infected Dectin-2KO mice had a shorter survival time, larger bacterial burden and lower interferon gamma (IFN-γ) production in the lungs than WT mice. Although neutrophilic infiltration in the lungs was equivalent between Dectin-2KO mice and WT mice, S. pneumonia engulfment by neutrophils was attenuated in Dectin-2KO mice compared to WT mice. The anti-pneumococcal polysaccharide-specific IgG and IgG3 levels in BALF were lower in Dectin-2KO mice than in WT mice. When BM-DCs were stimulated with S. pneumoniae culture supernatant or its Concanavalin A (ConA)-bound fraction, IL-12 production was abrogated in Dectin-2KO mice compared to WT mice. Conclusions: We demonstrated that Dectin-2 is intimately involved in the host defense against infection with a serotype 3 strain of S. pneumoniae. Dectin-2-dependent IL-12 production may contribute to IFN-γ synthesis and subsequent production of serotype-specific anti-capsular polysaccharide IgG after S. pneumoniae infection, which may promote S. pneumoniae bacterial opsonization for engulfment.

Original languageEnglish
Article number1
JournalBMC immunology
Volume17
Issue number1
DOIs
Publication statusPublished - 2016 Jan 5

Keywords

  • Anti-capsular polysaccharide IgG
  • Dectin-2
  • IFN-γ
  • Neutrophils
  • Streptococcus pneumonia

ASJC Scopus subject areas

  • Immunology

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    Akahori, Y., Miyasaka, T., Toyama, M., Matsumoto, I., Miyahara, A., Zong, T., Ishii, K., Kinjo, Y., Miyazaki, Y., Saijo, S., Iwakura, Y., & Kawakami, K. (2016). Dectin-2-dependent host defense in mice infected with serotype 3 Streptococcus pneumoniae. BMC immunology, 17(1), [1]. https://doi.org/10.1186/s12865-015-0139-3