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A single dose of endotoxin activates neutrophils without activating complement.
Surgery
|August 1, 1987
Summary
Endotoxin triggers neutrophil activation in healthy individuals, increasing complement receptors on neutrophils without activating the complement system. This suggests endotoxin directly primes neutrophils, independent of complement system involvement.
Area of Science:
- Immunology
- Critical Care Medicine
Background:
- Complement (C) and neutrophils (PMN) are activated in critically ill patients.
- The role of endotoxin in this activation is not fully understood.
Purpose of the Study:
- To evaluate the role of endotoxin in complement and neutrophil activation.
- To assess changes in complement activation products and PMN cell surface receptors following endotoxin administration.
Main Methods:
- Seven healthy subjects received endotoxin or saline solution on separate occasions.
- Measured complement activation products and PMN cell surface receptors (C3b, iC3b) using indirect immunofluorescence.
- Assessed PMN chemotaxis (CTX) to C5a, formyl-methionyl-leucine-phenylalanine, and PMN phagocytosis and killing of S. aureus.
Main Results:
- Endotoxin induced subjective febrile illness, myalgia, headache, and transient leukocytosis.
- PMN cell surface receptors for C3b and iC3b significantly increased post-endotoxin, indicating sustained PMN activation.
- No significant changes in plasma complement activation products (C3a desArg, C4a desArg, C5a desArg) were observed.
- PMN chemotaxis, phagocytosis, and killing functions remained unaffected.
Conclusions:
- A single dose of endotoxin causes PMN activation in healthy individuals.
- This PMN activation, indicated by increased complement receptor numbers, occurs independently of complement system activation.
- Endotoxin directly primes neutrophils, suggesting a non-complement-mediated pathway for PMN activation in response to endotoxin.