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The influence of complement receptor type 1 (CD35) and decay-accelerating factor (CD55) on complement receptor type
1Department of Immunology & Microbiology, Institute of Medical Biology, University of Southern Denmark, Denmark.
Insights
Complement receptor type 1 (CR1) remodels C3b fragments on B cells, enabling complement receptor type 2 (CR2) to activate the alternative pathway. Decay-accelerating factor (DAF) does not hinder this process.
Area of Science:
- Immunology
- Complement System Biology
Background:
- The complement system is crucial for innate and adaptive immunity.
- Complement receptor type 2 (CR2) plays a role in B cell activation.
- CR2-mediated complement activation is essential for B cell function.
Purpose of the Study:
- To investigate the role of complement receptor type 1 (CR1) and decay-accelerating factor (DAF) in CR2-mediated alternative pathway (AP) activation on B cells.
- To elucidate the mechanisms by which CR1 and DAF modulate complement activation on B cells.
Main Methods:
- Assessing the influence of CR1 and DAF on CR2-mediated AP activation.
- Analyzing the formation and function of the AP convertase on CR2.
- Investigating the remodelling of C3b fragments by CR1.
Main Results:
- Neither DAF nor CR1 impede the function of the AP convertase formed on CR2.
- CR1 significantly remodels C3b fragments at secondary acceptor sites on B cells.
- Remodelled C3b fragments become suitable ligands for CR2.
Conclusions:
- CR1 is essential for effective CR2-mediated AP activation by modifying C3b deposition.
- DAF does not inhibit CR2-mediated AP activation.
- These findings highlight a novel regulatory mechanism in B cell complement activation.
Abstract:
The influence of complement receptor type 1 (CR1; CD35) and decay-accelerating factor (DAF; CD55), both down-regulators of complement activation, on the complement receptor type 2- (CR2) mediated alternative pathway (AP) activation of complement on normal B cells, was assessed. The data indicate that, while neither DAF nor CR1 hinder the function of the AP convertase formed on CR2, CR1 plays a significant role in the remodelling of C3b fragments, generated by the convertase and deposited at secondary acceptor sites on the B-cell surface, such that they become suitable ligands for CR2. The significance of this finding is briefly discussed.