The Complement System.

Question 1

What are complement proteins?

Answer 1

Specialised proteins that can be activated by the innate or acquired immune system.

Question 2

What are the 3 main tasks that are carried out by the complement system?

Answer 2

Cell lysis.

Chemotaxis.

Opsonisation.

Question 3

Do complement proteins require antibodies in order to work?

Answer 3

No.

Question 4

Will complement proteins interact with antibodies?

Answer 4

Yes.

Question 5

Are there cells involved in the complement system?

Answer 5

No, there are no cells involved in the complement system.

Question 6

Are complement proteins part of the innate or adaptive immune system?

Answer 6

The innate immune system, but they have interactions with the acquired immune system.

Question 7

How many different complement proteins are there?

Answer 7

Around 20.

Question 8

What 2 cells can synthesise complement proteins?

Answer 8

Macrophages.

Hepatocytes.

Question 9

What will complement proteins exist as in the blood?

Answer 9

They exist as zymogens until they are activated.

Question 10

How are inactive complement proteins activated?

Answer 10

Via proteolytic cleavage.

Question 11

What names are used to designate different complement proteins?

Answer 11

A letter and a number.

E.g. C1, C2, C3.

Question 12

Can complement proteins kill cells, bacteria, viruses and parasites?

Answer 12

Yes.

Question 13

Will complement proteins interact with antibodies to kill pathogens?

Answer 13

They can kill pathogens with or without antibodies.

Question 14

What is one way that complement proteins will kill pathogens?

Answer 14

They can coat the pathogen and this marks it for phagocytosis.

This process is called opsonisation.

Question 15

Are complement proteins able to perform opsonisation?

Answer 15

Yes.

Question 16

Are complement proteins able to induce inflammation?

Answer 16

Yes.

Question 17

What are 2 ways that complement proteins can induce inflammation?

Answer 17

By attracting immune cells via chemotaxis.

By increasing vascular permeability and smooth muscle contraction.

Question 18

What is a common immune protein that complement proteins will interact with?

Answer 18

They promote the degranulation of mast cells.

Question 19

What are the 5 major functions of complement proteins?

Answer 19

The clearing of immune complexes.

Promotion of the degranulation of mast cells.

Induction of inflammation.

Opsonisation.

Killing of pathogens.

Question 20

What are immune complexes?

Answer 20

Complexes formed when an antibody binds to an antigen

Question 21

How does a complement protein perform opsonisation?

Answer 21

The protein binds to a bacterium and this marks the cell for phagocytosis.

Question 22

What region of an antibody will complement proteins bind to?

Answer 22

The FC region.

Question 23

Can complement proteins bind to an antibody that is already bound to a pathogen?

Answer 23

Yes, as they bind to the FC region. It is the variable region that pathogens bind to.

Question 24

What happens when a complement protein binds to an antibody that is already bound to a pathogen?

Answer 24

It leads to lysis of the cell or a phagocyte will come and consume the cell.

Question 25

What name is given to the antibodies that work with complement proteins?

Answer 25

Complement assisting antibodies.

Question 26

What molecules are involved in the complement system?

Answer 26

Only proteins, there are no cells involved in this system.

Question 27

What can initiate the complement cascade?

Answer 27

An infection.

Question 28

What happens when an infection activates the complement cascade?

Answer 28

Immune cells target the surface of the pathogen that is causing the infection.

Question 29

What are the 2 main ways that the complement cascade uses to eliminate pathogens?

Answer 29

Opsonisation and cell lysis.

Where opsonisation leads to phagocytosis and lysis leads to the death of the cell.