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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?
Direct Killing of pathogens
: 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?
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?
Mannose-binding Lectin (MB-Lectin) 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