Immunology-Complement

Question 1

What is the major way in which the complement pathway works?

Answer 1

triggers acute inflammation

promotes phagocytosis by macrophages and neutrophils

Question 2

What is the central event of complement activation?

Answer 2

Splitting of C3 into C3a and C3b

Question 3

Alternative pathway activation

Answer 3

C3>C3b>C3bB>C3bBb>C3bBb3b

positive feedback loop

C3bBb3b splits C5 into C5a and C5b

Factors I and H breakdown C3b to iC3b

Question 4

What are the main effects of the alternative complement activation pathway?

Answer 4

1. coat microorganisms with iC3b, a major target for phagocytosis via complement receptors
2. induce acute inflammatory response via C3a and C5a (anaphylotoxins)

Question 5

Classical pathway activation-antibody

Answer 5

C4>C4b>C4b2>C4b2b>C4b2b3b

Question 6

Classical pathway activation-lectin

Answer 6

binding of lectins (collectins and pentraxins) to pathogens

bind mannan carbs, activating mannan-binding lectin-associated proteases

Question 7

Membrane attack complex (MAC)

Answer 7

lytic pathway

activated by C3bBb3b or C4b2b3b

C5b binds to one C6>C5b6 binds one C7>binds one C8>binds 16 C9>pore formed>lysis by osmotic shock

Question 8

CD59

Answer 8

complement inhibitor

binds first molecule of C9 in MAC