Immune Response

Question 1

What is phagocytosis?

Answer 1

The cellular process of engulfing solid particles by the cell membrane to form an internal phagosome by phagocytes

Question 2

When is phagocytosis used?

Answer 2

As a non-specific second line of defence against pathogens - used by the immune system

Question 3

What characteristic of phagocytes allows it to squeeze out through tight junctions in capillaries/ gap between epithelial cells?

Answer 3

They live in the blood stream

Question 4

When do phagocytes invade the tissues?

Answer 4

If they recognise the release of histamine

Question 5

What hormone stimulates the arterioles to dilate so the phagocytes can head towards the damage

Answer 5

Histamine

Question 6

Why is yellow puss seen when phagocytes kill pathogens?

Answer 6

It is the dead pathogens

Question 7

What causes a phagocyte to be attracted to a pathogen?

Answer 7

Chemoattractants and toxins released by the pathogen

Question 8

How does the phagocyte move to the pathogen?

Answer 8

Along the concentration gradient

Question 9

What does the pathogen bind to on the phagocyte?

Answer 9

Receptors on the phagocyte attach to antigens on the pathogen

Question 10

How does the phagocyte engulf the pathogen?

Answer 10

The cell membrane forces it’s way over and extends around it then fuses back together

Question 11

What is created inside the phagocyte as the pathogen is engulfed

Answer 11

A vesicle called a phagosome

Question 12

How do the lysosomes interact with the phagosome?

Answer 12

They move towards the phagosome, then fuse with it and release lytic enzymes into it.

Question 13

How is the pathogen broken down?

Answer 13

Hydrolysis by the lysosomes hydrolytic enzymes

Question 14

What does the phagocyte do with the debris of hydrolyse pathogen?

Answer 14

Some leaves via exicitosis and some is retained by the cytoplasm, including the antigens which are placed on the cell surface membrane of a pathogen

Question 15

Why are the antigens of the pathogen retained?

Answer 15

So T cells and B cells can still recognise the non-self pathogen, meaning more clones of each are produced - immune response without causing harm

Question 16

What is immunity?

Answer 16

The ability of organisms to resist infection by protecting against disease causing microorganisms or their toxins that invade their bodies

Question 17

Is the initial response specific?

Answer 17

No

Question 18

What is an antigen?

Answer 18

A foreign protein on the cell surface membrane that triggers an immune response

Question 19

Where are B lymphocytes produced?

Answer 19

By stem cells in the bone marrow

Question 20

Where are T lymphocytes produced?

Answer 20

Thymus gland

Question 21

What type of immunity are T cells/ B cells involved in?

Answer 21

B cells = humoral immunity
T cells = cell-mediated immunity

Question 22

Why is it called humoral?

Answer 22

If involves antibodies which are present in body fluid (also known as “humour”)

Question 23

Why is it called cell mediated?

Answer 23

It involves body cells

Question 24

How do the lymphocytes distinguish between invader and normal cells? (4 ways)

Answer 24

1) pathogens antigens on phagocytes
2) body cells present viral antigens on their surface
3) transplanted cells have different antigens
4) cancer cells - different than normal cells so present different antigens

Question 25

What does a cell become when it presents different/foreign antigens on its cell surface membrane?

Answer 25

An antigen presenting cell

Question 26

Why are there vast numbers of Tcells?

Answer 26

Each one responds to a different antigen and therefore have different receptors on its surface that are complimentary to a single antigen

Question 27

What happens with T cells after phagocytosis?

Answer 27

Receptors on the T cell for exactly onto the antigens on the phagocytes surface - attachment activates the mitosis of the T cell and forms clones

Question 28

What 4 things does a cloned T cell become?

Answer 28

1) memory cell 2) stimulates phagocytosis 3) stimulates B cells to divide 4) Activates cytotoxic T cells

Question 29

What do cytotoxic cells produce?

Answer 29

The protein Perforin which makes holes on the cell surface membrane to kill the abnormal/infected cells

Question 30

How does perforin making holes in the membrane kill the cell?

Answer 30

Makes the membrane freely permeable to all substances - good ones leave

Question 31

Why are cytotoxic T cells most effective against viruses?

Answer 31

Sacrifices body cells and prevents viral replication

Question 32

What does humoral immunity involve?

Answer 32

Antibodies which are soluble in the blood and tissue fluid of the body

Question 33

Why are there as many as 10 million B cells?

Answer 33

Each B cell produces a specific antibody that responds to one specific antigen

Question 34

How do the Th cells recognise the B cell?

Answer 34

The surface antigens of an invading pathogen are taken up by a B cell

Question 35

How are B cells stimulated by Th cells?

Answer 35

They attach to the processed antigens on the B cell

Question 36

What do the B cells do after the Th cells activate them?

Answer 36

They divide by mitosis to give a clone of either memory or plasma cells

Question 37

What is the purpose of memory cells?

Answer 37

When the pathogen returns, they divide rapidly to plasma cells to produce lots of specific antibodies

Question 38

Why is the secondary response faster?

Answer 38

Plasma cells produce a higher concentration of antibodies at a faster rate

Question 39

What is the purpose of plasma cells?

Answer 39

They produce and secrete Antibodies that exactly fit the pathogen’s antigens