Complement

Question 1

What two components in blood serum are needed to right pathogens?

Answer 1

Heat-labile = complement
Heat-stable = antibodies

Question 2

Are antibodies present in all serums?

Answer 2

No, only present in the vaccinated

Question 3

Is complement present in all serums?

Answer 3

Yes

Question 4

Where are complement molecules mainly produced?

Answer 4

Liver

Question 5

What are zymogens?

Answer 5

Proteases secreted as inactive pro-enzymes

Question 6

How are zymogens activated?

Answer 6

Via proteolytic cleavage by other enzymes

Question 7

How is the Classical Pathway activated?

Answer 7

Antigen-antibody complex = recognized by C1q

Question 8

What is the structure of C1q?

Answer 8

Hexamer with collagen-like tail and 6 globular heads

Question 9

What activates C1r and what does this allow it to do?

Answer 9

Conformational change activates C1r = serine protease
Allowing it to cleave and activate C1s

Question 10

What cleaves C4 in the Classical Pathway?

Answer 10

C1s cleaves C4 into C4a and C4b

Question 11

What cleaves C2?

Answer 11

C2 is recognised by C1s and cleaved into C2a and C2b

Question 12

What makes up C3 convertase?

Answer 12

C4b2a

Question 13

How are C4b and C2a joined?

Answer 13

Chemically linked

Question 14

What activates the Alternative Pathway?

Answer 14

Spontaneous hydrolysis of C3

Question 15

What bond is hydrolysed in C3?

Answer 15

Thioester bond because of its inherent lability

Question 16

What C3 convertase is formed from Alternative Pathway?

Answer 16

Active initial fluid phase C3 convertase

Question 17

What does conformational change cause in the Alternative Pathway?

Answer 17

C3(H2O) to bind Factor B

Question 18

What activates Factor B?

Answer 18

Factor D cleaves Factor B

Question 19

What is produced from cleavage of Factor B?

Answer 19

Ba and Bb

Question 20

What makes the fluid-phase C3 convertase?

Answer 20

C3(H2O)Bb

Question 21

When is Factor B able to be cleaved?

Answer 21

Only when it is bound to C3(H2O)

Question 22

Where is mannose-binding lectin produced?

Answer 22

Liver

Question 23

At what concentrations is MBL present in plasma?

Answer 23

Low concentrations in plasma

Question 24

When does MLBs concentration increase?

Answer 24

During acute-phase reaction

Question 25

What is the structure of MBL?

Answer 25

Carbohydrate-recognition domain
alpha-helical coiled coil
Collagen helices

Question 26

What proteins does MBL form a compelx with?

Answer 26

MASP1/2 = MBL-Associated Serine Protease1

Question 27

What are MASP1/2?

Answer 27

Protease zymogens

Question 28

What do ficolins bind and with what domain?

Answer 28

N-acetylglucosamine
Fibronectin domain

Question 29

How does the Lectin Pathway generate C3 convertase?

Answer 29

Mannose residue on pathogen surface = recognized by MBL-MASP1/2 complex
Activates MASP2
MASP2 cleaves C4 and C2

Question 30

What makes the C5 convertase?

Answer 30

C3 convertase cleaves C3 -> C3a and C3b
C5 convertase = C4b2a3b

Question 31

How is MAC formed?

Answer 31

C5 convertase cleaves C5
C5b binds C6&7
C7 allows C5b67 to bind to membrane
C8 bind complex and inserts into cell membrane
C9 binds complex and polymerizes

Question 32

What does C1 inhibitor regulate?

Answer 32

Initiation
Binds active C1r-C1s = causing it to dissociate from C1q

Question 33

What does DAF regualte?

Answer 33

C3 convertase
Competes with Factor B for C3b = displaces Bb from convertase

Question 34

What does CR1 regulate?

Answer 34

C3 convertase
Similar to DAF

Question 35

What does Factor I regulate?

Answer 35

C3 convertase
Cleaves C3b to produce iC3b = inactive

Question 36

What cofactors work with Factor I?

Answer 36

Membrane Cofactor of Proteolysis (MCP)
Factor H

Question 37

What does Factor H regulate?

Answer 37

Competes with Factor B to displace Bb

Question 38

What regualtes C5 convertase?

Answer 38

Protectin = inhibits binding of C9 to C5b678

Question 39

What does Factor P do?

Answer 39

Properdin binds C3bBb
Enhances its stability