Immunology 3.2.4

Question 1

What are antigens?

Answer 1

Protein markers found on the
surface of all cells and viruses

Question 2

What are antibodies?

Answer 2

Proteins made by white blood
cells that bind to antigens

Question 3

What does immune mean?

Answer 3

Where the body is able to destroy a pathogen before it has a chance to cause disease

Question 4

What are white blood cell (lymphocytes)?

Answer 4

Cells in the blood that are involved in recognising and destroying pathogenic microorganisms

Question 5

What is the immune system?

Answer 5

A group of cells, tissues, organs and mechanisms that defend an organism against pathogens

Question 6

What are the two types immune system?

Answer 6

Non-specific and Specific

Question 7

What is active immunity?

Answer 7

The immunity which results from the production of antibodies by the immune system in response to the presence of an antigen

Question 8

An example of natural active immunity

Answer 8

Infection

Question 9

An example of artificial active immunity

Answer 9

Vaccination

Question 10

What is passive immunity?

Answer 10

Immunity which results from the introduction of antibodies from another person or animal

Question 11

An example of natural passive immunity

Answer 11

Maternal antibodies

Question 12

An example of artificial passive immunity

Answer 12

Monoclonal antibody

Question 13

What are the two types of non-specific immunity?

Answer 13

Physical barriers and phagocytes

Question 14

How do physical barriers prevent infection?

Answer 14

Physically prevent pathogens from gaining entry to
the body

Question 15

List 3 physical barriers and how they act as a barrier

Answer 15

1. Skin as an impervious barrier
2. Hydrochloric stomach acid as the acidic juices kill pathogens
3. Mucus on the trachea traps pathogens and wafts it up to be swallowed

Question 16

What are macrophages?

Answer 16

A type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells

Question 17

Why is phagocytosis non-specific?

Answer 17

Not dependent on recognising antigens

Question 18

What is the process of phagocytosis? (6 marks)

Answer 18

1) Detection of antigens
Foreign antigens bind to specific receptors on the cell surface of phagocytes.

2) Engulfing the pathogen
The phagocyte moves towards the pathogen.
The phagocyte cytoplasm surrounds the pathogen and the pathogen is engulfed.
When the pathogen is engulfed, it is sealed into a phagosome (a vacuole) inside the cytoplasm.

3) Digestion of the pathogen
Phagocytes have many organelles called lysosomes that contain proteolytic enzymes.
A lysosome fuses with the phagosome and releases the proteolytic enzymes into the phagosome.
The enzymes break down the pathogen.

4) Presenting the antigens
The pathogen antigens are transported to the phagocyte cell membrane and presented on the cell surface.
The antigens can activate the other cells in the immune response.

Question 19

What are the two branches of specific immunity? What lymphocytes are involved?

Answer 19

Cell-Mediated Response with T lymphocytes and Humoral response with B lymphocytes

Question 20

Where and what from are T and B lymphocytes formed?

Answer 20

Formed from stem cells in the bone marrow

Question 21

Where does each lymphocyte mature?

Answer 21

T lymphocyte - Thymus gland
B lymphocyte - Bone marrow

Question 22

Where are mature lymphocytes found when mature?

Answer 22

Lymph nodes and spleen

Question 23

What is an antigen presenting cell (APC)?

Answer 23

Any cell which presents a non-self antigen on the surface of cells

Question 24

Name the four antigen presenting cells

Answer 24

Infected body cells, macrophage, cells of transported organs, cancer cells

Question 25

Why are T cell responses known as 'cell mediated'?

Answer 25

As they only respond to antigens presented on cells (APC)

Question 26

What is the cell mediated response process ?

Answer 26

1) Pathogen goes through phagocytosis and has its antigens presented on the cell surface membrane so become an APC. 2) Helper T cells have receptors which can attach to the antigens on an APC. 3) Once attached this activates the T helper cells to begin dividing by mitosis in order to make clones. This is clonal expansion. 4) Cloned helper T cells differentiate into other cells.

Question 27

List the four other cells the cloned helper T cells can differentiate into and their function.

Answer 27

Remain as helper T cells to activate B lymphocytes by interleukins Macrophages to perform more phagocytosis Memory cells for that antigen to later rapidly divide when re-infected Cytotoxic T cells which kill the viral particles

Question 28

How do cytotoxic T cells kill infected or abnormal cells?

Answer 28

TC cells bind to antigens on the infected cell. Release the protein perforin which embeds into cell surface membrane and makes a pore. Cell cannot control which substances enters or leaves the cell. Cell death occurs.

Question 29

What response is B cells and antibodies involved in?

Answer 29

Humoral response

Question 30

Why is it called humoral response?

Answer 30

As antibodies are soluble and transport in bodily fluids. Humour is an old term for bodily fluids.

Question 31

What are the two branches of B Lymphocytes?

Answer 31

Plasma cells and B memory cells

Question 32

Plasma cell function

Answer 32

Produce specific antibodies to invading antigens. Only live for a few days but produce 2000 antibodies per second

Question 33

B memory cell function

Answer 33

Provide immunological memory and remain in the blood for a long periods of time

Question 34

How do B memory cells work

Answer 34

When re-infection occurs they reproduce rapidly to create more of the same specific antibody

Question 35

What is humoral immunity

Answer 35

A response to pathogens found in the blood stream

Question 37

What types of infections does humoral immunity fend off?

Answer 37

Bacteria and fungal

Question 38

What infection does cell mediated response fend off?

Answer 38

Viral infections

Question 39

What is the process of humoral immunity?

Answer 39

The B cell will engulf the pathogen and present the antigen on its surface, becoming an antigen-presenting cell. T helper cells bind to the antigens on the presenting B cell. This is clonal selection. Interleukins produced by the a t helper cells activate other B cells. The B cells rapidly divide (by mitosis) to produce many different B cells (plasma and memory cells). This is clonal expansion. These cloned plasma cells produce specific complementary antibodies to bind to the pathogens antigen, disabling them.