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Confocal Imaging of Double-Stranded RNA and Pattern Recognition Receptors in Negative-Sense RNA Virus Infection
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Microglia recognize double-stranded RNA via TLR3

Terrence Town1, David Jeng, Lena Alexopoulou

  • 1Section of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 06520, USA.

Journal of Immunology (Baltimore, Md. : 1950)
|March 7, 2006
PubMed

Insights

Microglia sense viral dsRNA via Toll-like receptor 3 (TLR3). This recognition triggers inflammatory responses, crucial for detecting central nervous system viral infections.

Area of Science:

  • Neuroimmunology
  • Innate Immunity
  • Molecular Biology

Background:

  • Microglia are the primary immune cells of the central nervous system (CNS).
  • Toll-like receptors (TLRs) are key sensors of pathogen-associated molecular patterns in innate immunity.
  • Previous studies indicated TLR3-deficient mice are resistant to viral encephalitis.

Purpose of the Study:

  • To investigate if microglia recognize double-stranded RNA (dsRNA) through the TLR3 pathway.
  • To elucidate the role of TLR3 in microglial activation and inflammatory responses to dsRNA.

Main Methods:

  • In vitro studies using primary cultured microglia stimulated with synthetic dsRNA (poly(I:C)).
  • Analysis of TLR3 and IFN-beta mRNA expression, cytokine secretion (TNF-alpha, IL-6), and MAPK activation.
  • In vivo studies using wild-type and TLR3-deficient mice injected with poly(I:C) or LPS, assessing microglial activation via immunofluorescence.

Main Results:

  • Wild-type microglia activated morphologically and increased TLR3 and IFN-beta mRNA upon poly(I:C) stimulation.
  • Poly(I:C) induced dose-dependent secretion of TNF-alpha and IL-6 in wild-type microglia, but diminished in TLR3-deficient microglia.
  • In vivo, poly(I:C) induced significant microgliosis in wild-type mice, which was nearly absent in TLR3-deficient mice.
  • MAPK activation kinetics were time-dependent in wild-type microglia and delayed in TLR3-deficient microglia.

Conclusions:

  • Microglia recognize dsRNA via the TLR3 pathway.
  • TLR3 signaling in microglia is critical for sensing viral dsRNA and initiating innate immune responses in the CNS.
  • Microglia act as key sensors for dsRNA-producing viruses entering the CNS.

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