Related Experiment Videos
Antibody-independent interactions between Escherichia coli J5 and human complement components.
Journal of Immunology (Baltimore, Md. : 1950)
|November 1, 1981
Summary
Gram-negative bacteria can activate the complement system's first component (C1) without antibodies. This antibody-independent C1 activation leads to bacterial cell death, impacting assessments of bacterial serum sensitivity.
Area of Science:
- Immunology
- Microbiology
- Complement System
Background:
- The classical complement pathway (C) is typically initiated by antibody binding.
- Recent findings suggest molecules can activate C1 independently of antibodies.
- This study re-examines the potential for Gram-negative bacteria to activate C1 without natural antibodies.
Purpose of the Study:
- To investigate the antibody-independent binding and activation of the complement's first component (C1) by Gram-negative bacteria.
- To determine if this binding and activation can initiate a bactericidal cascade.
Main Methods:
- Utilized radiolabeled native C1 for binding assays with Escherichia coli J5.
- Assessed C1 activation using SDS-PAGE.
- Measured consumption of complement components C4 and C2 by the bacteria-C1 complex.
- Evaluated bacterial viability after addition of terminal complement components (C3-C9).
Main Results:
- Escherichia coli J5 demonstrated dose-dependent binding of radiolabeled C1.
- Bound C1 was largely activated, consuming C4 and C2.
- Addition of terminal complement components (C3-C9) significantly reduced bacterial viability.
Conclusions:
- C1 can bind to bacterial membranes and initiate complement activation independently of antibodies.
- This antibody-independent C1 activation pathway contributes to bacterial killing.
- Findings necessitate re-evaluation of Gram-negative bacterial serum sensitivity assays.