Regulation of Classical Pathway of Complement Activation by Interferons

Area of Science:

• Immunology
• Biochemistry

Background:

• Complement activation is crucial in immunity but can be dysregulated during inflammation.
• Humoral factors, including interferons, may influence complement system activity.
• Interferons (IFNs) are known to modulate immune responses, but their direct role in complement regulation is less understood.

Purpose of the Study:

• To investigate the influence of recombinant alpha2b- and gamma-interferon on C5-convertase formation.
• To determine if interferons can regulate complement activation pathways.
• To explore a potential new mechanism of interferon action in immune regulation.

Main Methods:

• Utilized a model system with stabilized C3-convertase bound to sheep erythrocyte membranes.
• Assessed the effect of recombinant alpha2b- and gamma-interferon on C5-convertase formation.
• Quantified the inhibition of complement activation and complement-induced hemolysis.

Main Results:

• Recombinant alpha2b- and gamma-interferon stabilized C3-convertase and facilitated its transformation into C5-convertase.
• Interferon addition inhibited complement activation and abrogated complement-induced hemolysis.
• Inhibition constants were determined for both alpha2b- and gamma-interferon, indicating dose-dependent effects.

Conclusions:

• Interferons act as inhibitors of complement activation, representing a novel mechanism of their action.
• The binding of C3b complement component to interferons may physiologically constrain complement cascade activation.
• This finding suggests a significant role for interferons in modulating inflammatory and immune responses through complement system regulation.