B & I - Complement

Question 1

what is complement?

Answer 1

a proteolytic activation cascade

Question 2

what is complement essential for?

Answer 2

innate immunity

Question 3

what is the most abundant complement component in serum?

Answer 3

C3

Question 4

how many pathways can complement be activated through?

Answer 4

3

Question 5

what is the classical pathway of complement mediated by?

Answer 5

antibodies IgM or IgG binding to a microbe surface which is then bound by complement C1

Question 6

what is the deposition of complement on microbes essential for?

Answer 6

phagocytosis - called opsonisation

Question 7

what are deposited complexes called?

Answer 7

convertases

Question 8

what do convertases do?

Answer 8

activate more complement which then deposits to coat the surface

Question 9

how are convertases bound?

Answer 9

irreversibly bound through a covalent bond

Question 10

what does cleavage of C3, C4 and especially C5 produce?

Answer 10

small fragments called C3a, C4a and C5a

Question 11

what are C3a, C4a and C5a known as

Answer 11

chemoattractants called anaphylatoxins

Question 12

what do anaphylatoxins do

Answer 12

attract and activate neutrophils

Question 13

what does the end stage of complement (C5 onwards) activate

Answer 13

a lytic pore

Question 14

what does the lytic pore do

Answer 14

causes some bacteria to lyse

Question 15

what is the pore known as

Answer 15

membrane attack complex or MAC

Question 16

what specific type of people are susceptible to chronic infections?

Answer 16

people with deficiencies in a complement component

Question 17

what protein do many microbes produce

Answer 17

virulence factors

Question 18

what do virulence factors do

Answer 18

inhibit the complement cascade

Question 19

what is the alternative pathway

Answer 19

complement C3 is activated just by being close to the surface of the microbe which activates another type of C3 convertase

Question 20

what are lectins

Answer 20

carbohydrate-binding proteins in the blood that bind to unusual carbohydrates found only on microbes - complement condenses on these bound lectins

Question 21

neutrophils and macrophages have complement receptors that do what?

Answer 21

bind complement and initiate phagocytosis