Complement system

Question 1

Basic functions of complement system

Answer 1

Lysis of cells, bacteria and virus
Opsonization
Immune clearance
Bind complement receptors

Question 2

What does Lysis entail

Answer 2

Antibody dependent or antibody independent mechanisms

Question 3

Opsonization?

Answer 3

The uptake of particulate antigens by phagocytosis

Question 4

What are the fragments generated during activation called

Answer 4

A and B

Question 5

With a and b, which is larger and which is smaller?

Answer 5

A is smaller, b is larger

Question 6

Where do larger fragments bind?

Answer 6

large fragments binds to the target near the site of activation

Question 7

What do the smaller fragments do?

Answer 7

They diffuse from the site and can initiate receptor mediated local inflammatory responses

Question 8

What happens when fragments interact with each other?

Answer 8

They form functional complexes such as C4b2a

Question 9

The classical, lectin and alternative pathway all create what?

Answer 9

C5b

Question 10

What molecules activates the classical pathway?

Answer 10

IgM and IgG

Question 11

What are the components involved in the classical pathway?

Answer 11

C1,C2,C3 and C4

Question 12

What happens when IgM binds to an antigen?

Answer 12

There is a change that exposes a binding site for C1

Question 13

What domains does C1r and C1’s have?

Answer 13

Catalytic and interaction

Question 14

For C1q to have a stable interaction, what needs to happen?

Answer 14

C1q needs to bind to at least two Fc sites

Question 15

What happens to C1s when C1r converts it

Answer 15

It becomes an active enzyme with two substrates C4 and C2

Question 16

What is C4

Answer 16

C4 is a glycoprotein with 3 polypeptide chains α, β, γ

Question 17

C1s cleave the amino terminal end of the a chain, what happens?

Answer 17

A binding site on C4b is exposed (it is the larger fragment)

Question 18

What are the two forms of IgM

Answer 18

Pentameric when in solution and monomeric when attached to the cell

Question 19

C4b binds to the target vicinity of C1, then what happens

Answer 19

C2 attaches to the exposed site on C4b, C1 then cleaves it leaving C2a and C2b, C2b then diffuses away leaving C3 convertase

Question 20

How many polypeptide chains does C3 have?

Answer 20

two, a and b

Question 21

what is generated when C3a is cleaved?

Answer 21

C3b

Question 22

C3b binds to C4b2a3b to form what

Answer 22

C4b2a3b aka C5 convertase

Question 23

when C4b2a cleaves C5 and C5a diffuses away, what happens to C5b

Answer 23

C5b attaches to C6 which starts the formation of MAC

Question 24

Where do all the reactions take place?

Answer 24

They take place on the hydrophilic surfaces of membranes or immune complexes

Question 25

The terminal sequence of compliment activation involves what molecules

Answer 25

C5b,C6,C7,C8 and C9

Question 26

What is MAC

Answer 26

Mac is a large channel through the target cell membrane

Question 27

Where does C5b bind?

Answer 27

C5b binds to the surface of the target cell which allows the binding of other components

Question 28

C5b is inactivated unless what molecule stabilises it?

Answer 28

C6

Question 29

What happens when C5b6 binds to C7?

Answer 29

The hydrophobic residues on the complex are exposed which messes with the membrane phospholipids and inserts into the bilayer

Question 30

What are the final two steps in the formation of MAC

Answer 30

C8 binds to C5b67 and then a bunch of C9 joins the C5b678 complex

Question 31

When MAC occurs what goes on?

Answer 31

The cell cant stay stable and is killed by the water flushing in

Question 32

What immune system is the alternative pathway

Answer 32

Innate

Question 33

What does the alternative pathways include

Answer 33

C3, factor B, factor D and properdin

Question 34

C3b binds to foreign surface antigens which then binds factor B. What site is then exposed?

Answer 34

the enzyme Factor D

Question 35

What does factor D do?

Answer 35

Factor D cleaves off a small fragment Ba which then generates C3 convertase activity

Question 36

C3bBb has an activity of five minutes. what needs to bind to it to extend its life to 30 minutes?

Answer 36

Properdin

Question 37

What does protein and glycoproteins circulate in the serum as?

Answer 37

Zymogens