An assay for complement factor B in species at different levels of evolution

Area of Science:

• Immunology
• Evolutionary Biology
• Biochemistry

Background:

• The alternative complement pathway is the evolutionary precursor to other complement systems.
• Understanding its components, like factor B, across species offers evolutionary insights.
• Factor B plays a crucial role in the alternative complement pathway's function.

Purpose of the Study:

• To functionally characterize factor B from diverse animal species within the alternative complement pathway.
• To investigate the evolutionary conservation of factor B's function.

Main Methods:

• Developed a functional assay utilizing Cobra Venom Factor (CVF) as a C3b analog.
• Employed a signal system based on C3-conversion in factor B-depleted chicken serum.
• Tested the interaction of factor B from various animal taxa with CVF.

Main Results:

• A functional C3 convertase was successfully generated using factor B from mammals.
• Factor B from aves (birds) also formed a functional C3 convertase.
• Factor B from amphibians demonstrated functional C3 convertase activity.

Conclusions:

• Factor B from mammals, aves, and amphibians can form a functional C3 convertase in the assay.
• This suggests a conserved function of factor B across these vertebrate classes within the alternative complement pathway.
• The findings support the ancient evolutionary origins of the alternative complement pathway.