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Increased expression of toll-like receptor-2 and -4 on leukocytes from patients with sepsis

Luc Härter1, Ladislav Mica, Reto Stocker

  • 1Division of Trauma Surgery, University Hospital Zurich, Zurich, Switzerland. luc.haerter@usz.ch

Shock (Augusta, Ga.)
|October 19, 2004
PubMed

Insights

Sepsis patients show higher Toll-like receptor (TLR) expression on immune cells, but this doesn't explain their reduced response to endotoxin. Other mechanisms are involved in endotoxin tolerance.

Area of Science:

  • Immunology
  • Molecular Biology

Background:

  • Endotoxin tolerance, a reduced immune cell response to endotoxin during sepsis, is a critical factor in patient outcomes.
  • Toll-like receptors (TLRs), specifically TLR-2 and TLR-4, are key mediators of endotoxin recognition and immune activation.

Purpose of the Study:

  • To investigate the expression levels of TLR-2 and TLR-4 on neutrophils and monocytes in sepsis patients compared to healthy controls.
  • To determine if altered TLR expression correlates with the functional endotoxin tolerance observed in sepsis.

Main Methods:

  • Flow cytometry (FACS) was used to quantify surface expression of TLR-2 and TLR-4 on peripheral blood neutrophils (PMN) and monocytes from 21 sepsis patients and 12 healthy controls.
  • Leukocytes were incubated with or without TLR-4 (LPS) or TLR-2 (MALP-2) ligands, and receptor expression was measured at 0, 4, and 16 hours.
  • Interleukin-8 (IL-8) and Tumor Necrosis Factor-alpha (TNF-alpha) release was quantified by ELISA to assess immune cell responsiveness.

Main Results:

  • PMN and monocytes from sepsis patients exhibited significantly higher baseline expression of both TLR-2 and TLR-4 compared to healthy controls.
  • In sepsis patients, TLR-2 and TLR-4 expression on PMN increased over a 16-hour incubation period, while remaining stable in controls.
  • Despite elevated TLR expression, endotoxin-induced release of TNF-alpha and IL-8 was similar in sepsis patients and controls, indicating functional unresponsiveness.

Conclusions:

  • Increased expression of TLR-2 and TLR-4 on immune cells in sepsis does not solely account for endotoxin tolerance.
  • The findings suggest that other downstream signaling pathways or regulatory mechanisms are responsible for the impaired immune response in sepsis.

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