The Immune System

Question 1

What is an immune response?

Answer 1

Its the body reaction to a foreign antigen.

Question 2

Whats an antigen?

Answer 2

Antigens are molecules (usually proteins or polysaccharides) found on the surface of cells.

Question 3

What happens when a pathogen (like bacterium) invades the body?

Answer 3

when a pathogen (like bacterium) invades the body the antigens on its cell surface are identified as foreign, which activates cells in the immune system.

Question 4

In what stages does the immune system respond?

Answer 4

The immune systems involves specific and non specific stages

Question 5

How does the non specific response happen?

Answer 5

The non specific response happens in the same way for all microorganisms - whatever foreign antigens they have?

Question 6

How does the specific response happen?

Answer 6

The specific response is antigen-specif - it is aimed at specific pathogens and involves blood cells called T and B lymphocytes

Question 7

Whats the first stage of the immune system?

Answer 7

1. Phagocytosis

Question 8

What’s a phagocyte?

Answer 8

Its a type of blood cell that carries out phagocytosis (engulfment of pathogens)

Question 9

Wheres a phagocyte found and was do they do?

Answer 9

They’re found in the blood and in tissues and carry out a non-specific immune system.

Question 10

How does a phagocyte work?

Answer 10

> A phagocyte recognises the antigens on a pathogen
The cytoplasm of the phagocyte moves round the pathogen, engulfing it.
The pathogen is no contained in a phagosomes ( a type of vesicle) in the cytoplasm of the phagocyte.
A lysosome (an organelle that contains digestive enzymes) fuses with the phagosome. The enzymes break down the pathogen.
The phagocyte then presents the pathogens antigen. It stick the antigen on its surface to activate other immune system cells. When a phagocyte does this its acting as an antigen presenting cell.

Question 11

How can the the cytoplasm of the phagocyte moving round the pathogen, engulfing it can be made easier?

Answer 11

It can be made easier by the presence of opsonins - molecules in the blood that attach to foreign antigens to aid phagocytosis.

Question 12

What are neutrophils?

Answer 12

its a type of pathogen and are the first white blood cells to respond to a pathogen inside the body

Question 13

What do neutrophils do?

Answer 13

They move towards a wound in response to signals from cytokines (protein that act as messenger molecules). The cytokines are released by cells at the site of the wound.

Question 14

What is T lymphocyte?

Answer 14

Its another type of white blood cells which is covered with receptors that bind to antigens presented by APCc

Question 15

How does a T Lymphocyte work?

Answer 15

> Each T lymphocyte has a diff receptor on its surface therefore when it meets a complementary antigen, it binds to it.
This process activates the T lymphocyte which is knows as clonal selection
The activated T lymphocyte then undergoes clonal expansion - it divides to produce clones of itself.

Question 16

Why do different types of activated T lymphocytes carry out different functions?

Answer 16

> T helper cells release substances to activate B lymphocytes and T killer cells
T killer cells attach to and kill cells that are infected with a virus
T regulatory cells suppress the immune response from other white blood cells. This helps to stop immune system cells from mistakenly attacking the hosts body cells.

Question 17

What happens to some activated T lymphocytes?

Answer 17

They become memory cells

Question 18

What are B lymphocytes?

Answer 18

They are a type of white blood cells which are covered with antibodies - proteins that bond antigens to form an antigen-antibody complex.

Question 19

What type of antibodies do B lymphocyte have?

Answer 19

Each B lymphocyte has a different shaped antibody on its membrane l, so different ones bind to different shaped antigens

Question 20

How do antibodies of B lymphocyte bind?

Answer 20

They meet a complementary antigen and bind to it. The substance released from helper T cells, activate the B lymphocyte. This process is another example of clinal expansion.

Question 21

What happens to the activated B lymphocytes?

Answer 21

They divide by mitosis into plasma cells and memory cells. This is another example of clinal expansion.

Question 22

What’s are clones of B lymphocytes?

Answer 22

Plasma cells

Question 23

What do plasma cells severely?

Answer 23

They decree loads of the antibody, specific to the antigen, into the blood.

Question 24

What happen to the antibodies of plasma cells?

Answer 24

These antibodies will bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes. This is the signal for the immune system to attack and destroy the pathogen.

Question 25

What is cell signalling?

Answer 25

It’s how cell communicate

Question 26

What cause a response of some kind in the other cell?

Answer 26

A cell may release a substance that bind to the receptors on another cell which would cause a response in the other cell

Question 27

Why is cell signalling important?

Answer 27

It’s important in the immune system because it helps to activate all the different types of white blood cells that are needed

Question 28

What do T helper cells release?

Answer 28

They release interleukins (a type of cytokine) that bind to receptors on B lymphocytes. This activates the B lymphocyte - the T helper cells are signalling to the B lymphocytes that there’s a pathogen in the body

Question 29

What are blood smears?

Answer 29

It’s a sample of blood smeared over a microscope slide

Question 30

How are red blood cells easy to spot?

Answer 30

They have no nucleus

Question 31

How do u recognise a neutrophils?

Answer 31

It’s nucleus look like three interconnected blobs and the cytoplasm is grainy

Question 32

How do u recognise a lymphocyte?

Answer 32

It’s much smaller than the neutrophil and the nucleus takes up most of the cell and there’s a very little cytoplasm to be seen

Question 33

How do u recognise a monocytes?

Answer 33

It’s the biggest white blood cell and a type of phagocyte. It had kidney-bean shaped nucleus and non-grainy cytoplasm