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Generation of C5a by phagocytic cells
Markus Huber-Lang1, Ellen M Younkin, J Vidya Sarma
1Department of Pathology, University of Michigan Medical School, Ann Arbor 48109, USA.
The American Journal of Pathology
|November 5, 2002
Summary
Phagocytic cells, particularly lung macrophages, can generate the inflammatory molecule C5a from complement protein C5. This process is crucial for immune responses, especially within the lung environment.
Area of Science:
- Immunology
- Cell Biology
Background:
- C5a is a potent inflammatory mediator derived from complement protein C5.
- The primary pathways for C5a generation typically involve plasma complement system activation.
Purpose of the Study:
- To investigate the capacity of phagocytic cells, specifically macrophages and neutrophils, to generate C5a.
- To determine if C5a generation by these cells is dependent on plasma complement activation.
Main Methods:
- Incubation of human neutrophils and rat alveolar macrophages (AMs) with C5 and phorbol 12-myristate 13-acetate (PMA).
- Activation of rat AMs with lipopolysaccharide (LPS).
- Detection of C5a using specific antibodies and assessment of biological activity (chemotaxis).
Main Results:
- Both activated neutrophils and rat AMs generated C5a from C5.
- Activated macrophages exhibited more selective C5 cleavage than neutrophils.
- C5a generation by rat AMs was inhibited by transcription and protein synthesis inhibitors.
- Generated C5a demonstrated chemotactic activity and was sensitive to serine protease inhibitors.
Conclusions:
- Phagocytic cells, particularly lung macrophages, are capable of generating C5a.
- This cellular C5a generation pathway may be independent of the classical plasma complement system.
- This finding highlights a significant mechanism for local inflammatory mediator production in the lung.