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The activation of the C3b feedback cycle with human complement components. II. Using components of the alternative
Clinical and Experimental Immunology
|November 1, 1977
Summary
The C3 convertase enzyme, crucial for complement system feedback, was generated and shown to effectively deplete complement in human serum. Its in vivo formation in rats led to complement component cleavage and neutrophil changes.
Area of Science:
- Immunology
- Biochemistry
Background:
- The complement system is a vital part of innate immunity.
- The C3b feedback cycle amplifies complement activation.
- Understanding C3 convertase function is key to modulating immune responses.
Purpose of the Study:
- To generate and characterize the C3 convertase enzyme from the C3b feedback cycle.
- To assess its decomplementing activity in human serum.
- To investigate its in vivo effects in a rat model.
Main Methods:
- Fluid-phase generation of C3 convertase using C3b, factor B, and factor D.
- Assay of decomplementing activity in human serum.
- In vivo administration in rats to observe complement and neutrophil dynamics.
Main Results:
- C3 convertase effectively decomplemented human serum.
- Enzyme activity was dependent on feedback loop operation.
- Iodine oxidation of factor B did not enhance enzyme potency or stability.
- Antrypol treatment of C3b inhibited enzyme formation.
- In vivo formation in rats caused C3 cleavage, C5-C7 consumption, and biphasic neutrophil changes.
Conclusions:
- The C3 convertase is a potent decomplementing agent.
- Its formation and activity are linked to the C3b feedback cycle.
- In vivo studies suggest a role in complement-mediated inflammatory responses.