Defense Mechanisms

Question 1

What are the two types of defense mechanism?

Answer 1

Non-specific
Specific

Question 2

What are the characteristics of a non-specific response?
(2 points)

Answer 2

The response is:
- Immediate
- Same for all pathogens

Question 3

What are examples of non-specific responses?
(2 points)

Answer 3

• Physical barriers
• Phagocytosis

Question 4

What are the characteristics of a specific response?
(2 points)

Answer 4

The response is:
- Slower
- Specific to each pathogen

Question 5

What are the two types of lymphocyte?

Answer 5

T and B lymphocytes

Question 6

Which response does the T lymphocyte do?

Answer 6

Cell-mediated response

Question 7

Which response does the B lymphocyte do?

Answer 7

Humoral response

Question 8

How does the immune system recognise self and non-self cells?

Answer 8

By analysing the proteins on the surface of the cell

Question 9

What is the first step of phagocytosis?

Answer 9

Phagocyte is attracted to the pathogen by chemical products

Question 10

What happens after the phagocyte is attracted to the pathogen by chemical products in phagocytosis?

Answer 10

The phagocyte attaches to the pathogen by its receptors

Question 11

What happens after the phagocyte attaches to the pathogen by its receptors in phagocytosis?

Answer 11

The phagocyte engulfs the pathogen, forming a phagosome

Question 12

What happens after the phagocyte becomes a phagosome in phagocytosis?

Answer 12

Lysosomes move towards the phagosome

Question 13

What happens after the lysosomes move towards the phagosome in phagocytosis?

Answer 13

The lysosomes release lysozymes, which hydrolyse the pathogen

Question 14

What is an antigen?

Answer 14

Any part of an organism that is recognised as non-self by the immune system and stimulates an immune response

Question 15

Where are antigens usually found?

Answer 15

Usually proteins on the cell surface membranes or cell walls of invading cells

Question 16

Where are lymphocytes produced?

Answer 16

In the bone marrow

Question 17

Where do B lymphocytes mature?

Answer 17

In bone marrow

Question 18

Where do T lymphocytes mature?

Answer 18

In the Thymus gland

Question 19

What is the first step of the cell-mediated response?

Answer 19

Pathogen invades body cells or are taken in by phagocytes

Question 20

What happens after the pathogen is taken in by a phagocyte in the cell mediated response?

Answer 20

The phagocyte places the pathogen’s antigens on its cell surface membrane

Question 21

What happens after the phagocyte places the pathogen’s antigens on its cell surface membrane in the cell mediated response?

Answer 21

Receptors on specific T cells fit exactly onto these antigens

Question 22

What happens after receptors on the T cells fit onto the pathogen’s antigens on the phagocyte’s cell surface membrane in the cell mediated response?

Answer 22

The T cell becomes activated and divides rapidly by mitosis

Question 23

What can the cloned T cells do after the cell-mediated response has taken place?
(4 points

Answer 23

• Develop into memory cells that can respond rapidly if the same pathogen invades again
• Stimulate phagocytes to engulf pathogens
• Stimulate B cells to divide and secrete antibodies
• Activate cytotoxic T cells

Question 24

How do cytotoxic T cells kill infected cells?

Answer 24

They release a protein called perforin that makes holes in the cell-surface membrane, causing it to become freely permeable to all substances, making the cell die

Question 25

What does humoral immunity involve?

Answer 25

Antibodies

Question 26

What is the first step of humoral immunity?

Answer 26

Surface antigens of a pathogen are taken up by a B cell

Question 27

What is the step after **surface antigens of a pathogen are taken up by a B cell** in the humoral response?

Answer 27

The B cell processes the antigens and presents them on its surface

Question 28

What is the step after **the B cell processes the antigens and presents them on its surface** in the humoral response?

Answer 28

A helper T cell attaches to the processed antigens on the B cell, activating it

Question 29

What is the step after **a helper T cell activates the B cell** in the humoral response?

Answer 29

The B cell divides by mitosis to make plasma cells and memory cells

Question 30

What do plasma cells do?

Answer 30

They secrete antibodies into the blood plasma

Question 31

What do memory cells do?

Answer 31

When they come into contact with an antigen a second time, they divide rapidly into plasma cells and more memory cells

Question 32

What is a monoclonal antibody?

Answer 32

When a single antibody can be isolated and cloned outside the body

Question 33

How can direct monoclonal antibody therapy be used to treat cancer?

Answer 33

- Monoclonal antibodies are produced that are specific to the antigens on the cancer cells - These antibodies are given to the patient and attach to the receptors of the cancer cells - They then block the chemical signals that the cancer cells release in order to replicate rapidly

Question 34

How can indirect monoclonal antibody therapy be used to treat cancer?

Answer 34

Attaching a radioactive or cytotoxic drug to the monoclonal antibody. When the antibody attaches to the cancer cells and kills them

Question 35

How do pregnancy tests use monoclonal antibodies?

Answer 35

Placenta produces a hormone called hCG, that is found in the urine. hCG in the urine bind to the monoclonal antibodies on the test strip. The hCG-antibody-colour complex moves along the strip until it is trapped by another antibody creating a line

Question 36

What are ethical issues with the use of monoclonal antibodies?

Answer 36

- Use of mice in production - Parents need to have full knowledge and give full consent as the use of monoclonal antibodies can have risks as well as benefits - Safety testing of new drugs can have dangers

Question 37

What is passive immunity?

Answer 37

The introduction of antibodies into individuals from an outside source.

Question 38

How quickly is immunity acquired from passive immunity?

Answer 38

Immediately

Question 39

What are examples of passive immunity?

Answer 39

- Anti-venom given to snake bite victims - Antibodies passing through the placenta from mother to fetus

Question 40

What is active immunity?

Answer 40

Stimulation of the production of antibodies by the individuals' own immune system

Question 41

How long does active immunity take to develop

Answer 41

Several weeks

Question 42

What are the two types of active immunity?

Answer 42

- Natural active immunity - Artificial active immunity

Question 43

What is natural active immunity?

Answer 43

Results from when the individual is infected naturally. The body creates its own antibodies and continues to do so for many years

Question 44

What is artificial active immunity?

Answer 44

From vaccination. Inducing an immune response without suffering the symptoms of the disease

Question 45

What is the intention of vaccination?

Answer 45

To stimulate an immune response against a particular disease. This makes memory cells be produced which allow for a quicker response to a future infection from the same disease

Question 46

What are the features of a successful vaccination program?

Answer 46

- The vaccine must be economically available to immunise the vulnerable population - Must be few side-effects - Means of producing, storing and transporting the vaccine - Qualified staff to administer the vaccine - Must be possible to vaccinate the majority of the vulnerable population (herd immunity)

Question 47

What is herd immunity?

Answer 47

When a sufficiently large proportion of the population has been vaccinated. This makes it difficult for the pathogen to spread

Question 48

Why is herd immunity important?

Answer 48

Its never possible to vaccinate everyone in a large population. Therefore if most of the population is vaccinated, the transmission of the pathogen is interrupted.

Question 49

How might a vaccine not induce immunity?

Answer 49

- If an individual has a faulty immune system - Individuals could develop the disease immediately before they are immune, and harbour the disease and transmit it - The pathogen could mutate and therefore develop different antigens