Complement system
positive feedback system
- proteolysis of C3 (most important) by C3 convertase to C3a and C3b
- classical pathway: C1 binds to an antigen-antibody complex
- alternative pathway: microbial surface molecules and other nasties (cobra venom?!)
- lectin pathway: plasma mannose-binding lectin binds to carbohydrates on microbes and directly activates C1
- C3b → C5 convertase → forms C5a and C5b
- C5b attached to cell surface
for what?
- inflammation
- phagocytosis - C3b fixed to microbial cell wall acts as opsonin
source: Robbins