Lecture #5

Question 1

Complement System

Answer 1

Consists of several plasma proteins that work together to opsonize microbes, to promote the recruitment of phagocytes to the site of infection, and in some cases directly kill the microbes

Question 2

What three pathways can activate the complement system?

Answer 2

Classical pathway, Alternative pathway, and Lectin Pathway

Question 3

Classical Pathway Requires?

Answer 3

IgM or IgG and C1

Question 4

Classical C3 Convertase

Answer 4

C4bC2a (same as alt)

Question 5

Classical C5 Convertase

Answer 5

C4bC2aC3b (same as alt)

Question 6

In Lectin Pathway, what happens when MBP binds to bacteria?

Answer 6

MASP’s are activated

Question 7

Lectin C3 Convertase

Answer 7

C4bC2a (same as classical)

Question 8

Lectin C5 Convertase

Answer 8

C4bC2aC3b (same as classical)

Question 9

Alternative Pathway needs?

Answer 9

Factors B and D

Question 10

What happens to C3 in Alternative Pathway?

Answer 10

It undergoes spontaneous hydrolysis

Question 11

Alternative C3 Convertase

Answer 11

C3bBb

Question 12

Alternative C5 Convertase

Answer 12

C3bBb3Cb

Question 13

DAF (Decay-accelerating factor)

Answer 13

• Blocks C2:C4b interaction

- Disassociates C4bC2a

Question 14

CR1 (Complementary receptor 1)

Answer 14

• Disassociates C4bC2a (C3 convertase for classical and lectin)
• Cleaves C4b and C3b
• Co-factor for FI (Factor I or aka C3/C4 Indicator**)

Question 15

Factor I

Answer 15

• *Aka C3/C4 Indicator**
• Cleaves C4b and C3b
• Prevents assembly of C3 Convertase and C5 Convertase

Question 16

Microbes can survive in a phagolysosome if?

Answer 16

If they express catalyse

Question 17

Members of collectin family include:

Answer 17

• Mannose binding lectin (MBL)
• Pulmonary surfactant porteins SP-A
• SP-D

Question 18

Collectins

Answer 18

A family of soluble trimeric proteins with lectin head which serve as effector molecules of the innate immune system

Question 19

MBL (Mannose binding lectin)

Answer 19

A soluble PRR that binds carbohydrates with terminal mannose and enhance phagocytosis

Question 20

Low levels MBL

Answer 20

Associated with increased susceptibility to a variety of infections

Question 21

SP-A / SP-D

Answer 21

Have lipophilic properties and their major functions are to maintain the ability of lungs to expand and as mediators of innate immune responses

Question 22

SP-A / SP-D can directly

Answer 22

Inhibit bacterial growth and activate macrophages

Question 23

Ficolins

Answer 23

Plasma proteins that are structurally similar to collectins, but they have a fibrinogen-type carbohydrate recognition domain

Question 24

Ficolins recognize?

Answer 24

N-acetylglucosamine and lipoteichoic acid

Question 25

Ficolins binds

Answer 25

N-acetylglucosamine on the surface of microbes and activates MASP1 and MASP2

Question 26

Regulators of complement Activation (RCA)

Answer 26

Inactivation of human C3 is regulated by a family of related proteins

Question 27

RCA proteins are

Answer 27

1. Decay-accelerating factor (DAF or CD55) - membrane-attached 2. membrane cofactor protein (MCP or CD46) - membrane-attached 3. complement receptor 1 (CR1) - membrane-attached 4. Factor I (FI) - soluble

Question 28

How do RCA proteins control complement activation?

Answer 28

1. RCA proteins can promote the irreversible dissociation of complement convertases. 2. RCA proteins can serve as cofactors in the FI-mediated cleavage of C3b and C4b.

Question 29

Special function of RCA?

Answer 29

DAF acts to accelerate the decay of the a) classical/lectin (C4C2a) and b) alternative C3 (C3bBb) convertases

Question 30

Classical pathway

Answer 30

1. Blockage of binding | 2. Dissociation of C2a and C4b, enhanced by DAF or CR1

Question 31

Alternative pathway

Answer 31

DAF attaches to C3bBb and Bb dissociates

Question 32

MCP is a cofactor for the FI-mediated cleavage of

Answer 32

A. cell-bound C3b (created by any 3 of comp. pathways) | B. C4b (only classical/lectin pathway)

Question 33

CR! is a cofactor for the FI-mediated cleavage of:

Answer 33

A. cell-bound C3b (created by any 3 of comp. pathways) | B. C4b (only classical/lectin pathway)