Immunity

Question 1

Define immunity

Answer 1

the means by which the body protects itself from infection

Question 2

Outline a non specific defence mechanism

Answer 2

Immediate response
Same for all pathogens

Physical barriers and phagocytosis

Question 3

Outline a specific defence mechanism

Answer 3

Slower response
Specific to each pathogen

Cell mediated response and humoral responce

Question 4

Name 3 physical barriers

Answer 4

Skin
Mucus
Ear wax
Hair
Tears
Stomach Acid
Scabbing

Question 5

Why does the body’s immune system take a number of days to control an infection?

Answer 5

Lymphocytes must build up their numbers/replicate

And this takes a long time

Question 6

Why is it incorrect to say the body takes several days to respond to infection?

Answer 6

The body responds immediately by recognising foreign antigens
And carrying out phagocytosis

Question 7

Briefly outline phagocytosis

Answer 7

1. Phagocyte identifies pathogen
2. Receptors bind to pathogen
3. Pathogen trapped in phagosome
4. Lysosomes fuse with phagosome
5. Pathogen is hydrolysed
6. Antigen is displayed of phagosome cell surface

Question 8

How are pathogens destroyed in phagocytosis

Answer 8

Lysosomes containing enzymes
Lysozymes
Hydrolyse the pathogen

Question 9

Why might phagocytes be abundant in tears?

Answer 9

Protective covering of the eye and tear ducts are pathogen entry points
Tears hydrolyse pathogens that try to enter through the eye
Before infection and harm can occur

Question 10

Define antigen

Answer 10

A molecule from the cell surface membrane
That triggers an immune response
By lymphocytes

Question 11

What are the two types of lymphocyte?

Answer 11

B lymphocytes

T lympohcytes

Question 12

Briefly outline cell-mediated immunity

Answer 12

1. Receptors on Th cells fit onto antigens displayed on phagocytes cell surface
2. Th cell activates
3. Th cell rapidly divides by mitosis to form clones

Question 13

What can a clones T helper cell do?

Answer 13

Develop into a memory cell
Stimulate phagocytes to perform phagocytosis
Stimulate B cells to divide
Activate Tc Cells

Question 14

How does a cytotoxic T cell kill infected cells?

Answer 14

Produces a protein; Perforin
That makes holes in the cell surface membrane
Allowing free movement of substances
Destroying the cell

Question 15

Which type of pathogen are Tc cells most effective against?

Answer 15

Virsuses

They use living cells to replicate

Question 16

Name 2 similarities between T cells and B cells

Answer 16

Both white blood cells
Both lymphocytes
Both have a role in immunity
Both produced from stem cells
Both produce memory cells

Question 17

Name 2 differences between T cells and B cells

Answer 17

Mature in: T cells = thyumus gland, B cell = bone marrow
T Cell = cell-mediated immunity, B cell = homural immunity
T Cells cant produce antibodies, B cells can
T Cells only detect presented antigens, B cells detect any antigens

Question 18

Briefly outline humoral immunity

Answer 18

1. B cells take up and process antigens
2. Th cells activate the B cell
3. The B cell rapidly divides by mitosis to form clones

Question 19

What can cloned B cells do?

Answer 19

Become plasma cells

Become memory cells

Question 20

What does a plasma cell do?

Answer 20

Produces antibodies
Only survive a few days
Produce 2000 antibodies a second

Question 21

What does a memory cell do?

Answer 21

Survive for up to decades
Rapidly divide into new T cells and B cells when they encounter a specific antigen
Providing long term immunity

Question 22

Why is a secondary immune response more rapid than a primary immune response?

Answer 22

Antigens have not been ingested, processed or presented in a primary response
The immune response takes time as these steps must occur consecutively

In a secondary response memory cells are present and only require cloning and development into plasma cells
Fewer processes mean a quicker response

Question 23

Outline 2 differences between Cell-mediated immunity and humoral immunity

Answer 23

Cell-mediated = T cells, Humoral = B cells
Cell mediated = no antibodies, Humoral = antibodies
Cell mediated = effective through cells, humoral = efffective through body fluid

Question 24

Outline 2 similarities between Cell-mediated immunity and humoral immunity

Answer 24

Both immune responses
Both specific immune responses
Both produce memory cells
Both require antigens

Question 25

Define antibody

Answer 25

A protein produced by lymphocytes in response to the presence of an appropriate antigen

Question 26

Outline the structure of an antibody

Answer 26

Four polypeptide chains; 2 heavy chains, 2 light chains Binding site that is complimentary to specific antigen Variable region that results in different binding site shapes Constant region that binds to receptors on cells (eg b cells)

Question 27

How does an antibody lead to the destruction of an antigen?

Answer 27

Agglutination; clumps bacterial cells together for easier location by phagocytes Serve as markers to stimulate phagocytosis

Question 28

Define monoclonal antibody

Answer 28

An antibody produced by a single clone of cells

Question 29

How can antibodies be used in medicine?

Answer 29

Targeting cancer cells Diagnosis of diseases Pregnancy testing

Question 30

Name 2 ethical pros of using antibodies in medicine

Answer 30

Treat life threatening diseases such as cancer Diagnose life threatening diseases Rapid results More effective than other methods of treatment

Question 31

Name 2 ethical cons of using antibodies in medicine

Answer 31

Involves use of mice by giving mice cancer Has resulted in some deaths; multiple sclerosis Trial tests in March 2006 resulted in all volunteers suffering multiple organ failure

Question 32

Define passive immunity

Answer 32

resistance to disease that is acquired from the introduction of antibodies from another individual rather than your own immune system

Question 33

Define active immunity

Answer 33

resistance to disease resulting from the activities of an individuals own immune system whereby an antigen induces plasma cells to produce antibodies

Question 34

What is the difference between natural active immunity and artificial active immunity

Answer 34

Natural results from an individual becoming infected and producing its own antibodies Artificial comes from vaccination and results in the production of antibodies due to exposure to the antigen, but no infection

Question 35

What signs must a vaccination show to be successful?

Answer 35

``` Economically beneficial Few side effects Easily produced, transported and stored Means of administration available Majority of vulnerable population must be vaccinated ```

Question 36

Define her immunity

Answer 36

Majority of the population is vaccinated So pathogen is difficult to spread Protecting susceptible individuals

Question 37

Why might a vaccination not eliminate a disease?

Answer 37

``` Vaccination fails to induce immunity Infection immediately after vaccination Frequent mutation of the pathogen Too many varieties of the pathogen Pathogens hiding in body cells Objections of vaccination (eg religion) ```

Question 38

Define antigenic variablity

Answer 38

A change in a pathogens antigens resulting in the immune system no long producing antibodies to destroy the pathogen

Question 39

Name 3 ethical questions that should be taken into account with vaccination

Answer 39

How acceptable is vaccine production? How can side-effects be balanced against the risk of infection? Who should vaccines be tested on? Should vaccines be compulsory? Should vaccination continue when the disease is almost eradicated? Should vaccines with unknown side effects be issued in emergency situations?

Question 40

What does HIV stand for?

Answer 40

Human immunodeficiency virus

Question 41

What does AIDS stand for?

Answer 41

Acquired Immune deficiency syndrome

Question 42

Outline the structure of HIV

Answer 42

``` Lipid envelope on outside With attachment proteins embedded Capsid inside protein layer Two strands of RNA inside capsid Reverse transcriptase inside capsid ```

Question 43

How does HIV replicate?

Answer 43

1. HIV enters blood stream and circulates body 2. HIV binds to helper t cells 3. Capsid fuses with cell surface membrane and contents of HIV enter cell 4. HIV reverse transcriptase converts RNA into DNA 5. New DNA inserts into cell's DNA 6. Messenger RNA creates new viral proteins and RNA 7. HIV is pieced together and burst from the cell

Question 44

How does HIV cause AIDS?

Answer 44

HIV attacks T helper cells Reducing the number of T helper cells So B cells cannot be stimulated Resulting in a lack of adequate humoral response

Question 45

What does ELISA stand for?

Answer 45

Enzyme linked immunosorbant assay

Question 46

Outline the ELISA test

Answer 46

1. Antigens attach to a surface 2. Wash to remove unattached antigens 3. Add antibody specific to antigen so they bind 4. Wash to remove excess antibody 5. Add second antibody to bind with first antibody with attached enzyme 6. Add colourless substrate of enzyme 7. Enzyme hydrolyses substance if present, giving a coloured positive result