Endotoxin tolerance: is there a clinical relevance?

Area of Science:

• Immunology
• Cellular Biology

Background:

• Endotoxin tolerance, first defined in 1946, is a state of reduced fever response to lipopolysaccharide (LPS).
• It involves macrophages, glucocorticoids, and cytokines like IL-10 and TNF, with reduced TNF production being a key indicator.
• Cross-tolerance can occur between LPS and other immune stimuli, and similar LPS hypo-reactivity is seen in sepsis and SIRS patients.

Purpose of the Study:

• To review the mechanisms and implications of endotoxin tolerance.
• To compare experimental endotoxin tolerance with immune dysregulation in sepsis and Systemic Inflammatory Response Syndrome (SIRS).

Main Methods:

• Literature review of studies on endotoxin tolerance, LPS-induced responses, and immune cells in sepsis/SIRS.
• Analysis of cellular signaling pathways in tolerant and non-tolerant leukocytes.

Main Results:

• Endotoxin tolerance is characterized by reduced cytokine production (e.g., TNF) and altered leukocyte signaling pathways.
• Experimental and clinical LPS hypo-reactivity share similarities but are not identical.
• While tolerance can mitigate infection severity, it may enhance susceptibility to nosocomial infections in SIRS patients.

Conclusions:

• Endotoxin tolerance is a complex immune phenomenon with both protective and detrimental effects.
• Understanding these mechanisms is crucial for managing sepsis, SIRS, and related immune dysfunctions.
• Further research is needed to differentiate in vitro and in vivo endotoxin tolerance in various clinical settings.