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C5a-specific modulation of phagocyte functions in patients with localized bacterial infections
U Mrowietz1, E Christophers, J M Schröder
1Department of Dermatology, University of Kiel, Federal Republic of Germany.
Abstract:
Chemotaxis, enzyme release and superoxide-anion (O2-) generation of purified peripheral blood neutrophils (PMN) and monocytes were studied in a total of 87 patients suffering from localized bacterial infections. Shortly after disease onset, single or several PMN functions became non-responsive to the complement split product C5a. Functional activities elicited by the synthetic peptide f-met-leu-phe or leukotriene B4 remained unaltered. C5a-specific impairment lasted one to several days and returned to normal with the subsidence of the disease. C5a elicited release of beta-glucuronidase as well as generation of superoxide-anions was seen more often to be impaired as compared to chemotactic migration. In contrast to PMN, monocytes from the same patients failed to show paralleling C5a-specific functional alterations. There was no correlation between impairment of PMN functions and plasma levels of the complement split-products C3a and C4a as determined by RIA. It is concluded that in acute infectious disease a graded C5a-specific modulation of PMN functions may be present. This phenomenon is transient and not paralleled by functional alterations of monocytes or changes in plasma complement levels.
Insights
In acute bacterial infections, neutrophil functions responding to C5a become temporarily impaired, affecting enzyme release and superoxide generation. Monocyte function and complement levels remain unaffected.
Area of Science:
- Immunology
- Infectious Disease
Background:
- Neutrophils (PMN) and monocytes are key immune cells in combating bacterial infections.
- Complement component 5a (C5a) is a potent chemoattractant and activator of neutrophils.
Purpose of the Study:
- To investigate the functional responses of neutrophils and monocytes to C5a in patients with localized bacterial infections.
- To determine if C5a-specific impairments correlate with disease severity or complement levels.
Main Methods:
- Studied chemotaxis, enzyme release, and superoxide-anion generation in neutrophils and monocytes from 87 patients with bacterial infections.
- Assessed functional responses to C5a, f-met-leu-phe, and leukotriene B4.
- Measured plasma levels of C3a and C4a using RIA.
Main Results:
- Neutrophil functions, particularly C5a-mediated beta-glucuronidase release and superoxide-anion generation, were transiently impaired shortly after infection onset.
- Impaired neutrophil functions recovered within days as the disease subsided.
- Monocyte functional responses to C5a remained unaltered, with no correlation found between PMN dysfunction and plasma C3a/C4a levels.
Conclusions:
- Acute bacterial infections can induce a transient, C5a-specific modulation of neutrophil functions.
- This neutrophil dysfunction is not mirrored in monocytes and does not correlate with systemic complement levels.