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Functional analysis of mouse ficolin-B and detection in neutrophils
Katja Hunold1, Dorothea Weber-Steffens, Valeria L Runza
1Institute of Immunology, University of Regensburg, Germany.
Abstract:
Ficolins and mannan-binding lectin recognize pathogen-associated molecular patterns and initiate the lectin pathway of complement activation via the associated serine proteases. In contrast to human ficolins and mouse ficolin-A, mouse ficolin-B has been considered incapable of complement activation. Dose-dependent binding of recombinant ficolin-B to immobilized GlcNAc, acetylated BSA, acetylated LDL, and fetuin was detected with ficolin-B-specific monoclonal antibodies. Recombinant ficolin-B bound to immobilized acetylated bovine serum albumin interacted with recombinant human mannan-binding lectin-associated serine protease-2, which led to C4 cleavage, thus demonstrating the capability of ficolin-B to activate the lectin pathway. Ficolin-B-specific monoclonal antibodies identified natural ficolin-B protein in lysates of mouse granulocytes isolated from the bone marrow. These results identify mouse ficolin-B as a functional member of the ficolin family activating complement via the lectin pathway.
Insights
Mouse ficolin-B, previously thought inactive, can activate the lectin complement pathway. This discovery identifies ficolin-B as a functional complement-activating ficolin in mice.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Ficolins and mannan-binding lectin initiate the lectin complement pathway.
- Mouse ficolin-B was previously considered unable to activate complement.
Purpose of the Study:
- To investigate the complement-activating potential of mouse ficolin-B.
- To determine if ficolin-B functions within the lectin pathway.
Main Methods:
- Recombinant ficolin-B binding assays using immobilized ligands (GlcNAc, acetylated BSA, LDL, fetuin).
- Interaction studies between ficolin-B and mannan-binding lectin-associated serine protease-2 (MASP-2).
- Detection of C4 cleavage as an indicator of complement activation.
- Immunological identification of natural ficolin-B in mouse granulocytes.
Main Results:
- Mouse ficolin-B demonstrated dose-dependent binding to various ligands.
- Ficolin-B interacted with MASP-2, leading to C4 cleavage.
- Natural ficolin-B protein was detected in mouse bone marrow granulocytes.
Conclusions:
- Mouse ficolin-B is capable of activating the lectin complement pathway.
- Ficolin-B functions as a pattern recognition molecule in complement activation.
- This study reclassifies ficolin-B as a functional member of the ficolin family.
