Complement System

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What is the complement system?

Major pathway acting to protect against infection and inflammation
What triggers a cascade?

Interaction with complement components with each other in an enzyme
What are zymogens?
- Protease (complement component)
- require activation by enzyme cleavage
Function of the complement system?
- Production of opsinin
- Production of anaphylatoxins
- Direct Killing of pathogens
- Others: Maintenance to homeostasis, enhancing Ag-specific immune response
Function of opsinin?

enhance phagocytosis of particles by macrophage and neutrophils
How do opsinin work?
- Coat bacteria which are then recognised by specific receptors on phagocytes (macrophages, neutrophils)
- Trigger phagocytosis of bacteria
Products of the complement cascade?

Opsinin
What do opsinin stimulate?

phagocytosis of bacteria (MOST IMPORTANT COMPLEMENT FUNCTION)
What are anaphylatoxins?

Peptide/fragments from cleavage of complement protein
What do anaphlatoxins do?

Induce local and systemic inflammatory response
Anaphylatoxins bind to many cell types. Give an example and what occurs?
- Bind to neurophils
- Stimulate directional migration
- migrate from area of lesser conc to area of higher conc
- chemotatic for neutrophils --> more phagocytes recruited to site of complement activation
What are the 3 pathways of active complement?
- Classical pathway
- Mannose-binding Lectin (MB-Lectin) pathway
- Alternative pathway
How is the classical pathway initiated?

binding of C1q to pathogen surface
How is mannose-binding lectin pathway initiated?

binding of mannose-binding lectin to carbohydrates on bacteria/virues
How is the alternative pathway initiated?

Binding of spontaneously active C3 in plasma to pathogen surface

Author

J.Seet

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Card Set

Complement System

Description

Complement System

Updated

2013-11-17T16:24:44Z

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