CLEC9A modulates macrophage-mediated neutrophil recruitment in response to heat-killed Mycobacterium tuberculosis H37Ra

PLoS One. 2017 Oct 24;12(10):e0186780. doi: 10.1371/journal.pone.0186780. eCollection 2017.

Abstract

Tuberculosis is a fatal human infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis) that is prevalent worldwide. Mycobacteria differ from other bacteria in that they have a cell wall composed of specific surface glycans that are the major determinant of these organisms' pathogenicity. The interaction of M. tuberculosis with pattern recognition receptors (PRRs), in particular C-type lectin receptors (CLRs), on the surface of macrophages plays a central role in initiating innate and adaptive immunity, but the picture as a whole remains a puzzle. Defining novel mechanisms by which host receptors interact with pathogens in order to modulate a specific immune response is an area of intense research. In this study, based on an in vitro lectin binding assay, CLEC9A (DNGR-1) is identified as a novel CLR that binds with mycobacteria. Our results with CLEC9A-knocked down cells and a CLEC9A-Fc fusion protein as blocking agents show that CLEC9A is involved in the activation of SYK and MAPK signaling in response to heat-killed M. tuberculosis H37Ra treatment, and it then promotes the production of CXCL8 and IL-1β in macrophages. The CXCL8 and IL-1β secreted by the activated macrophages are critical to neutrophil recruitment and activation. In a in vivo mouse model, when the interaction between CLEC9A and H37Ra is interfered with by treatment with CLEC9A-Fc fusion protein, this reduces lung inflammation and cell infiltration. These findings demonstrate that CLEC9A is a specialized receptor that modulates the innate immune response when there is a mycobacterial infection.

MeSH terms

  • Animals
  • Cell Line
  • Gene Knockdown Techniques
  • Hot Temperature*
  • Humans
  • Lectins, C-Type / genetics
  • Lectins, C-Type / physiology*
  • Macrophages / enzymology
  • Macrophages / physiology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mycobacterium tuberculosis / physiology*
  • Neutrophils / cytology*
  • Protein Kinases / metabolism
  • Receptors, Mitogen / genetics
  • Receptors, Mitogen / physiology*
  • Signal Transduction

Substances

  • CLEC9a protein, human
  • Lectins, C-Type
  • Receptors, Mitogen
  • Protein Kinases

Grants and funding

This work was supported by grants to P.-H.T. from the Taiwan Ministry of Science and Technology (MOST105-2321-B-010-005), and a grant from the “Aim for the Top University Plan” project of the Taiwan Ministry of Education. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.