Acute inflammation cellular phase: complement system Flashcards
Why does the complement system clear immune complexes out of circulation?
So that they don’t get stuck in small blood vessels, which happens in vasculitis and causes fibrinoid necrosis
What are complement proteins?
Proteins that are produced by liver and circulate blood as inactive precursors, and are activated to help the inflammatory process
What molecules control complement system activation?
Regulatory proteins
How can protein deficiencies cause disease in regards to complement system activation
Lack of regulatory proteins causes uncontrollable complement system activation, which causes disease
What are the 3 pathways to activate the complement system?
Classical
Alternative
Mannose-binding lectin
How does the alternative pathway activate the complement system?
Microbial components directly activate complement system
How does the classical pathway activate the complement system?
Antigen binds to IgM or IgG, which activates C1 complement protein
How does the mannose-binding lectin pathway activate the complement system?
Mannose-binding lectin binds to mannose on bacterial surface
What is a lectin?
Protein that binds to carbohydrates
What complement protein do all 3 pathways activate formation of in the complement system?
C3 convertase formation
What molecule does C3 convertase bind to in the complement system?
Complementary C3 substrate
What 2 proteins are formed from the splitting of the C3 in the C3 convertase-substrate complex in the complement system?
C3a and C3b
What are the 2 functions of C3a protein in the complement system?
C3a is an anaphylatoxin which recruits leucocytes and stimulates histamine release from mast cells
What is the function of C3b protein in the complement system?
C3b is an opsonin that coats bacteria, so acts as an ‘eat-me’ signal and binds to C3b receptors on attracted neutrophils and macrophages to stimulate phagocytosis
How is C5 convertase formed in the complement system?
C3b proteins bind together
