Lecture 3 - Complement

Question 1

What is complement

Answer 1

augmented opsonization working with the actions of antibodies

Question 2

What 3 pathways make up the complement system?

Answer 2

1 - classical
2 - alternative
3 - lectin

Question 3

What component of blood is the complement system found

Answer 3

plasma

Question 4

T/F: the complement system is part of the adaptive defense system

Answer 4

False - innate

Question 5

T/F: the complement system plays a regulatory role in the adaptive immune system

Answer 5

True

Question 6

T/F: complements do not need to be activated as they are a natural part of the immune system

Answer 6

False - they must be activated via a cascade pathway

Question 7

What are the biochemical principles of complement systems

Answer 7

1. synthesized as inactive precursors
2. activated via cleavage
3. results in active complement protease
4. amplification

Question 8

what is added to an inactive complements name once it is cleaved

Answer 8

a lowercase suffix

Question 9

What is a complex of complements called

Answer 9

a factor

Question 10

what activates the complement system

Answer 10

1. pathogen itself
2. antibody bound to pathogen

Question 11

T/F: all pathways create a common effector complement protein

Answer 11

True

Question 12

what are the effector proteins created by complement pathways

Answer 12

C3a, C3b, C5b, MAC, C3 convertase

Question 13

What is the final goal of the three complement pathways

Answer 13

removal of the pathogen

Question 14

The classical pathway is activated by:

Answer 14

antibody bound to the pathogen

Question 15

The MBL (mannose-binding lectin) pathway is activated by:

Answer 15

lectin binds to mannose on the pathogen cell wall

Question 16

The alternative pathway is activated by:

Answer 16

binding of a complement directly to the pathogen surface

Question 17

Summarize the classical pathway in 5 steps

Answer 17

1 - C1 binds to antibody
2 - conformational changes cleave C4 and C2 proteins
3 - C4b and C2b combine (C3 convertase)
4 - C3 is cleaved
5 - C3b binds and activates C5 which stimulates MAC formation

Question 18

Summarize the alternative pathway in 5 steps

Answer 18

1 - spontaneous breakdown of C3
2 - if C3b binds to a healthy cell, factors H and I cause C3b degradation
3 - if C3b binds to a pathogen, factor H and I do not bind
4 - C3b will bind factor B
5 - B is cleaved by factor D which creates an alternate C3 convertase

Question 19

Summarize the MBL pathway in 5 steps

Answer 19

1 - lectin complex binds to lectin
2 - MASP cleaves C4 and C2
3 - C4b and C2b combine (C3 convertase)
4 - combined complex cleaves C3
5 - C3b binds and activates C5 which stimulates MAC formation

Question 20

Which pathway requires the adaptive immune system to initiate?

Answer 20

Classical

Question 21

Which pathway uses factors and letters instead of numbers?

Answer 21

alternative

Question 22

What does C3 convertase cause

Answer 22

• recruitment of inflammatory cells
• opsonization
• lysis of cell membrane

Question 23

Which complement component is an anaphylatoxin

Answer 23

C3a

Question 24

Which complement component is an opsonin

Answer 24

C3b

Question 25

Which complement component forms the pore of the MAC

Answer 25

C9

Question 26

C1 inactivator

Answer 26

inhibits C1 components in the classical pathway

Question 27

CD55

Answer 27

decay accelerating factor of complement factors on normal cells

Question 28

Factor H

Answer 28

a similar function in CD55 in the alternative pathway

Question 29

CD59

Answer 29

inhibits assembly of MAC

Question 30

Complement receptors

Answer 30

ensure removal of antigen-antibody complexes

Question 31

C3 deficiency in Brittany Spaniels can lead to ______ in old age. how?

Answer 31

renal disease - chronic inflammation of the glomerulus and reduced clearance of associated complexes

Question 32

What does factor H deficiency allow

Answer 32

overactive complement on healthy cells (autoimmune)