11. Immunity

Question 1

Name and describe 3 of the external defense system

Answer 1

1. Epithelia that cover the airways are an effective barrier to the entry of pathogens
2. Hydrochloric acid in the stomach kills many bacteria that we ingest with food and drink
3. Blood clotting

Question 2

What are the two types of white blood cells?

Answer 2

Phagocytes and lymphocytes

Question 3

What are antibodies?

Answer 3

Glycoprotein molecules that act against specific antigens

Question 4

What is an immune response?

Answer 4

The response of lymphocytes to the presence of a foreign antigen

Question 5

What are the types of phagocytes?

Answer 5

Neutrophils and macrophages

Question 6

Explain what happens when pathogens invade the body.

Answer 6

Some of the cells under attack respond by releasing chemicals such as histamine

Question 7

Explain the process of Phagocytosis.

Answer 7

-The neutrophils move towards the pathogens which are clustered together and covered in antibodies.
-The antibodies stimulate the neutrophils to attack the pathogens, this is because neutrophils have receptor proteins on their surfaces that recognize antibody molecules and attach to them.
-After the neutrophil attaches to the pathogens, the neutrophil’s cell membrane engulfs the pathogens and traps them within a phagocytic vacuole in a process called endocytosis.
-Lysosomes fuse with the phagocytic vacuoles releasing enzymes that breakdown the pathogens.

Question 8

What is the lifespan of a neutrophil?

Answer 8

After killing and digesting some pathogens they die.
Dead neutrophils collect at a site of infection to form pus

Question 9

What are the two types of lymphocytes?

Answer 9

B-lymphocytes (B cells)
T-lymphocytes (T cells)

Question 10

Describe where you can find the B cells

Answer 10

They remain in the bone marrow until they are mature then they spread throughout the body.
Concentrating in lymph nodes and the spleen.

Question 11

Describe where you can find the T cells

Answer 11

They leave the bone marrow and collect in the thymus where they mature.

Question 12

Describe the immune response by the T cells.

Answer 12

-T cells coordinate the immune response stimulating B cells to divide and then secrete antibodies into the blood.
-The antibodies recognize the antigens on the pathogens and help destroy the pathogens.
-Other T cells find and kill any of the body’s own cells that are affected with pathogens.

Question 13

Describe what is clonal selection?

Answer 13

When the antigen enters the body for the first time, the small numbers of B cells with their cell membrane receptors complementary to the antigen are stimulated to divide by mitosis

Question 14

What is the primary immune response?

Answer 14

The first immune response to a specific antigen.
It is slow because there are very few B cells that are specific to the antigen.

Question 15

What is the secondary immune response?

Answer 15

The second and subsequent immune responses to a specific antigen. It is faster because there are now many memory cells which quickly divide and differentiate into plasma cells.

Question 16

Describe the structure of an antibody molecule

Answer 16

Each one consists of four polypeptide chains: two ‘long’/heavy chains and two ‘short’/‘light’ chains
Disulfide bonds hold the chains together

Question 17

What is the variable region on an antibody molecule?

Answer 17

The region that forms the antigen-binding site; the amino acid sequences of the variable site form a specific shape that is complementary to a particular antigen

Question 18

What are the two types of T cell

Answer 18

T-helper cells
T-killer cells

Question 19

What is the function of T-helper cells

Answer 19

When they are activated, they release cytokines that stimulate appropriate B cells to divide, develop into plasma cells and secrete antibodies

Question 20

What is the function of T-killer cells?

Answer 20

They search the body for cells that have become invaded by pathogens and are displaying foreign antigens from the pathogens on their cell surface membranes.
They recognize the antigens attach themselves to the surface of infected cells and secrete toxic substances such as hydrogen peroxide killing the body cells and the pathogens inside

Question 21

What is active immunity ?

Answer 21

Immunity gained when an antigen enters the body, an immune response occurs and antibodies are produced by plasma cells

Question 22

What is natural active immunity?

Answer 22

Immunity gained by being infected by a pathogen

Question 23

What is artificial active immunity

Answer 23

Immunity gained by putting antigens into the body either by injection or by mouth

Question 24

What is passive immunity

Answer 24

The temporary immunity gained without there being an immune response

Question 25

What is artificial passive immunity

Answer 25

The immunity gained by injecting antibodies

Question 26

What is natural passive immunity

Answer 26

The immunity gained by a fetus when maternal antibodies cross the placenta or from breast milk

Question 27

What is herd immunity?

Answer 27

Vaccinating a large proportion of the population which provides protection for those not immunized as transmission of a pathogen is reduced

Question 28

Where are phagocytes produced and stored ?

Answer 28

In the bone marrow

Question 29

Where are macrophages located?

Answer 29

The lungs
Liver
Spleen
Kidney
Lymph Nodes

Question 30

What crucial role do the macrophages play?

Answer 30

They initiate immune responses and do not destroy the pathogens completely but cut them up to display antigen that can be recognized by lymphocytes

Question 31

Some of the activated B cells become 1._______ and others become 2._________. State the function of each of these.

Answer 31

1. Plasma cells
   Produce antibody molecules very quickly and they secrete the antibodies into the blood, lymph or linings of the lungs and gut.
2. Memory cells
   Remain circulating in the body for a long time if the same antigen is reintroduced a few weeks or months after the first infection, memory cells divide rapidly and develop into plasma cells and more memory cells.

Question 32

What is the function of the “hinge” region on an antibody?

Answer 32

It gives the flexibility for the antibody molecule to bind to antigens on the surface of a pathogen

Question 33

How are T-cells activated ?

Answer 33

They are activated when they recognize this antigen on another cell of the host ( the owners cells )

Question 34

What is a vaccine?

Answer 34

A preparation containing antigens which is used to stimulate an immune response artificially

Question 35

What can be used in the vaccine?

Answer 35

A whole live microorganism
A dead microorganism
A harmless microorganism (attenuated organism)

Question 36

What is a booster injection?

Answer 36

They are given after receiving less effective vaccines so that it stimulates secondary responses that give enhanced protection
It is also a good idea to receive booster shots if you are likely to be exposed to a disease

Question 37

What is ring immunity?

Answer 37

Vaccinating all those people in contact with a person infected with a specific disease to prevent disease transmission in the immediate area

Question 38

What is hybridoma?

Answer 38

A cell formed by the fusion of a plasma cell and a cancer cell, it can both secrete antibodies and divide to form other cells like itself

Question 39

How are the antibodies used in MABS produced?

Answer 39

By injecting a mouse with human fibrin (main protein found in blood clots) the mouse makes many plasma cells that secrete the antibody against fibrin. Then these plasma cells are collected from its spleen. Plasma cells are fused with cancer cells to form hybridoma that secrete the antifibrin antibody

Question 40

How are Mabs used to locate blood clots?

Answer 40

The radioactively labeled Mab is introduced to the patients blood and binds to any fibrin molecules it comes into contact with in the bloodstream. The radioactivity emitted by these labeled antibodies is used to detect where they are in the body. Then a gamma ray camera is used to detect the exact position of the antibodies in the person’s body

Question 41

What are Mabs used for?

Answer 41

To locate the position of blood clots in the body of a person though to have deep vein thrombosis
To locate cancer cells
To identify the exact strain of a virus or bacterium that is causing an infection

Question 42

How has Mabs now been developed to humanize it?

Answer 42

1. Altering the genes that code for the heavy and light polypeptide chains of the antibodies so that they code for human sequences of amino acids rather than mouse or rabbit sequences
2. Changing the type and position of the sugar groups that are attached to the heavy chains to the arrangement found in human antibodies

Question 43

State the role of the constant region on an antibody molecule

Answer 43

Determines the mechanism used to destroy the antigens

Question 44

Name 5 functions of the antibodies.

Answer 44

1. They can combine with viruses and toxins of pathogens to block them from entering or damaging cells.
2. They can act as antitoxins by binding to toxins produced by pathogens which neutralize them and make them harmless.
3. They can attach to bacteria making them readily identifiable to phagocytes.
4. They can attach to the flagella of bacteria making them less active which makes it easier for phagocytosis
5. They can create holes in the cell walls of pathogens causing them to burst when water is absorbed by osmosis.