The specific immune response and immunity

Question 1

Define the term “antigen” and differentiate between “self” and “non-self” antigens.

Answer 1

Identifying chemical on the surface of the cell that triggers an immune response.
Self antigens are on your own cells and non-self antigens are on the cells of pathogens

Question 2

Define the term antibody

Answer 2

Y-shaped glycoproteins made by B ells of the immune system in response to the presence of an antigen

Question 3

Define the term antigen-antibody complex

Answer 3

The complex formed when an antibody binds to an antigen

Question 4

Define the term lymphocyte

Answer 4

WBC that make up the specific immune response

Question 5

Define the term specific immune response

Answer 5

It is the slower than non-specific responses.

However the immune memory cells mean it reacts very quickly to a second invasion by the same pathogen

Question 6

Draw, label and annotate a diagram of an antibody.

Answer 6

1. Y-shaped- made up of two identical long polypeptide chains called the heavy chains and two much shorter chains called the light chains
2. The chains are held together by disulfide brides as well as disulfide bridges within the polypeptide chain holding them in shape
3. Bottom of y is receptor binding site
4. Two ends of the branches of the y are the antigen binding sites- variable region - is a different shpa eon each antibody- gives it it’s specificity
5. the rest is the constant region and is always the same

Question 7

Describe and explain 4 ways in which antibodies defend the body.

Answer 7

1. The antibody of the antigen-antibody complex acts as an opsonin so the complex is easily engulfed and digested by phagocytes
2. Most pathogens can no longer effectively invade the host cells once they are part of an antigen-antibody complex.
3. Antibodies act as agglutinins causing pathogen carrying antigen-antibody complexes to clump together. This helps to prevent them form spreading through the body- makes it easier for phagocytes to engulf a number of pathogens at the same time
4. Antibodies act as anti-toxins, binding to the toxins produced by pathogens and making them harmless

Question 8

Explain why B lymphocytes are called “B” whereas T lymphocytes are called “T”.

Answer 8

1. B lymphocytes mature in the Bone marrow

2. T lymphocytes mature in the Thymus gland

Question 9

Name the 4 main types of T lymphocytes

Answer 9

1. T helper cells
2. T killer cells
3. T memory cells
4. T regulator cells

Question 10

Decribe the role of T helper cells

Answer 10

1. Have receptors on their cell-surface membrane which bind to the surface antigens on APCs
2. Produce interleukins- type of cytokine (cell signalling molecule)
3. These interleukins help to stimulate the activity of B cells which increases antibody production, stimulates the production of other types of T cells and attracts and stimulates macrophages to ingest pathogens with antigen-antibody complexes

Question 11

Describe the role of T killer cells

Answer 11

1. Destroy pathogens carrying the antigen
2. Produce a chemical called perforin which kills the pathogen by making holes in the cell membrane so it is freely permeable

Question 12

Describe the role of T memory cells

Answer 12

1. Live for long time as part of immunological memory
2. If they meet an antigen for the second time they divide rapidly to form a huge number of clones of T killer cells that destroy the pathogen

Question 13

Describe the role of T regulator cells

Answer 13

1. Suppress the immune system acting to control and regulate it.
2. They stop the immune response once a pathogen has been eliminated and make sure the body recognises self antigens and does not set up an autoimmune response
3. Interleukins are important in this control

Question 14

Name the 3 main types of B lymphocytes

Answer 14

1. Plasma cells
2. B effector cells
3. B Memory cells

Question 15

Describe the role of plasma cells

Answer 15

1. Produce antibodies to a particular antigen and release them into the circulation

Question 16

Describe the role of B effector cells

Answer 16

1. Divide to form plasma cell clones

Question 17

Describe the role of B memory cells

Answer 17

1. Live a long time as part of the immunological memory
2. Programmed to remember a specific antigen and enable the body to make a very rapid response when a pathogen carrying that antigen is encountered again

Question 18

Define the term “cell mediated immunity” and suggest what it is particularly effective against.

Answer 18

1. T lymphocytes respond to cells of an organism that have been changed in some way e.g. by a virus infection, by antigen processing or by mutation (cancer cell) and to cells from transplanted tissue

Question 19

Describe the process of cell mediated immunity.

Answer 19

1. Antigen presenting cells formed:- from phagocytosis, a viral infection or cancer
2. APC comes into contact with many different T helper cells – only T helper cells with complementary receptors to the antigens will be activated.- Clonal selection
3. T helper cells produce interleukins which stimulate other types of activated T-cell to clone by mitosis (as well as making the T helper cells themselves clone by mitosis)- Clonal expansion
4. T cells cloned may:
   - develop into T memory cells which give a rapid response if this pathogen invades again
   - Develop into T helper cells which either produce interleukins that stimulate phagocytosis or produce interleukins that stimulate B cells to clone by mitosis
   - Stimulate the development of a T killer cells that are specific for the presented antigen and then destroy infected cells

Question 20

Define the term “humoral immunity” and suggest what it is particularly effective against.

Answer 20

1. The body responds to antigens found outside the cells- bacteria, fungi and to APCs.
2. The humoral immune system produces antibodies that are soluble in the blood and tissue fluid and are not attached to the cells.

Question 21

Describe the process of humoral immunity.

Answer 21

1. B lymphocytes have antibodies on their cell surface membrane which are specific to only one antigen,
2. When a pathogen enters the body, a B cell with complementary antibodies will bind to the antigens on the pathogen - it will engulf and process the antigen to become an APC.
3. Clonal selection- Selection of the appropriate B cell by the T helper cells to be cloned- T cell binds to the B cell APC
4. Clonal expansion- T helper cell produces interleukins to activate the B cells which then divide by mitosis to produce clones
5. B cells differentiate to form plasma and B effector cells and B memoery cells
6. Plasma cells secrete antibodies which are specific to the antigen which help to destroy the pathogen
7. Memory cells remain in circulation to provide a secondary response- faster response to subsequent exposure

Question 22

Define the term primary immune response

Answer 22

The relatively slow production of a small number of the correct antibodies the first time a pathogen is encountered

Question 23

Define secondary immune response

Answer 23

The relatively fast production of very large quantities of the correct antibodies the second time a pathogen is encountered as a result of the immunological memory.

Question 24

Draw, label and annotate a graph of quantity of antibody in the blood over time to compare the primary and secondary immune responses.

Answer 24

1. Secondary immune response produces a lot more anitbodies
2. The rate at which antibodies are produced is much faster
3. They are quicker to start producing antibodies

Question 25

Why is the secondary immune response quicker

Answer 25

1. Antigen presentation still happens 2. Clonal selection- many more cells 3. Clonal expansion- less needs to happen because there are already a lot of cells- memory cells- this is what saves the most time

Question 26

Define active immunity

Answer 26

The type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen.

Question 27

Define passive immunity

Answer 27

Type of immunity when you are given antibodies made by a different organism

Question 28

Define natural immunity

Answer 28

Occurs when the person is exposed to a live pathogen develops the disease and becomes immune as a result of the primary immune response- developed without intervention

Question 29

Define artificial immunity

Answer 29

Body is given immunity to a disease by intentional exposure to small quantities of it

Question 30

Give one example for each of natural active immunity, natural passive immunity, artificial active immunity and artificial passive immunity.

Answer 30

Natural active- immune after catching a disease Natural passive- baby becomes immune due to antibodies it receives form its mother though placenta/ breast milt Artificial active- Vaccination Artificial passive- Injected with antibodies from someone else

Question 31

Draw a table comparing active and passive immunity.

Answer 31

Time taken- A: not immediate, P: immediate Duration- A: long term, P: short term Exposure to antigens- A: Yes P: No Clonal expansion/selection- A: Yes, P:No Antibodies supplied/ made- A: made, P: supplied Production of memory cells- A: yes, P: no Requires fully functioning immune system- A: Yes, P: no

Question 32

Define the term “autoimmune disease” and name and describe 3 examples of autoimmune diseases.

Answer 32

Autoimmune disease- a condition or illness resulting from an autoimmune response- when the immune system acts against its own cells and destroys health tissue in the body 1. Lupus- immune system attacks cells in connective tissue which causes painful inflammation- affects skin, joints and heart and lungs 2. Rheumatoid arthritis- attacking cells in the joints which cases pain and inflammation 3. Type 1 diabetes- affects insulin-secreting cells of the pancreas

Question 33

Suggest how autoimmune diseases may occur.

Answer 33

If the immune system can't recognise self antigens so treats them as foreign antigens and launches an immune response against organisms own tissues

Question 34

Define vaccine

Answer 34

A safe form of an antigen which is injected into the blood stream to provide artificial active immunity against a pathogen bearing the antigen

Question 35

Define vaccination

Answer 35

The administering of a vaccine causing immunisation

Question 36

Describe 5 ways in which antigens can be obtained for use in vaccines.

Answer 36

1. Isolated antigens 2. Genetically engineered antigens 3. Killed or inactive pathogens 4. Weakened (attenuated) pathogens 5. Altered toxins

Question 37

Describe how vaccination results in artificial active immunity.

Answer 37

1. It triggers the primary immune response by the foreign antigens and your body produces antibodies and memory cells 2. If you come into contact with a live pathogen, the secondary immune response is triggered and you destroy the pathogen rapidly

Question 38

Define the term epidemic

Answer 38

When a communicable disease spreads rapidly to a lot of people at a local or national level

Question 39

Define the term pandemic

Answer 39

When a communicable disease spreads rapidly to a lot of people across a number of countries

Question 40

Define the term “herd immunity”.

Answer 40

When a significant number of people have been vaccinated, this gives protection to those who do not have immunity - herd immunity - as there is minimal opportunity for an outbreak to occur. Helps people who can't get vaccinated- young, old or immunosupressed people

Question 41

Give two examples of vaccination programmes that aim to provide herd immunity.

Answer 41

1. MMR- given to children at a year old and just before they start school 2. Meningitis C - given to babies at 3 months and boosters are given at 1 year and to teens.

Question 42

Suggest why the Influenza vaccine needs to be redeveloped and people need to be revaccinated each year.

Answer 42

1. Because the antigens on the surface of the influenza virus change regularly forming new strains of the virus 2. Memory cells produced from the vaccination with one strain of the flu will not recognise other strains with different antigens- immunologically different

Question 43

Describe 6 examples of common medicinal drugs derived from living organisms.

Answer 43

1. Penicillin- from mould on melons- antibiotic 2. Docetaxel- derived from yew trees- treatment for breast cancer 3. Aspirin- based on compounds from sallow bark- painkiller, anti-coagulent, anti-pyretic, anti-inglammatory 4. Prialt- derived from venom of a cone snail- pain killing drug 5. Vancomycin- derived from soil fungus- one of most powerful anti-biotics 6. Digoxin- based on digitoxin originally extracted from foxgloves- powerful heart drug used for atrial fibrillation and heart faliure

Question 44

Explain the need to maintain biodiversity in relation to the discovery of new medicines.

Answer 44

If we don't protect biodiversity some species may die out before we get a chance to study them. They could prove to be useful sources of medicine

Question 45

Define the term “personalised medicine”, give an example of how treatment is being personalised, and suggest the value of personalising medicine to a person’s genetic information.

Answer 45

1. They are medicines that are tailored to an individual's DNA- dependent upon the characteristics of the individual (size, age but particularly the individual's genomes) 2. The theory is that doctors will be able to predict how you will respond to different drugs and only prescribe the ones that will be most effective for you- avoid side effects.

Question 46

Define the term “synthetic biology” and give 2 examples of how synthetic biology may lead to better medical treatments.

Answer 46

1. Involves using technology to design and make things like artificial proteins, cells and even microorganisms. 2. scientists are looking at engineering bacteria to destroy cancer cells while leaving healthy body cells intact 3. Drugs produced by organisms that wouldn't normally make that chemical- genetic engineering

Question 47

Define the term antibiotic

Answer 47

A chemical or compound that kills or inhibits the growth of bacteria

Question 48

Define the term selective toxicity

Answer 48

The ability to interfere with the metabolism of a pathogen without affecting the cells of the host.

Question 49

Draw a table to outline the different ways 4 common antibiotics have their effect.

Answer 49

1. Affects cell walls made of peptidoglycan- burst 2. Enzymes- inhibit the metabolic pathways 3. Bacteria have a circular chromosome that is different to humans, so they can target the different DNA replication- prevent reproduction 4. Ribosomes- prevent protein synthesis 5. Make holes in the membrane altering the permeability

Question 50

Explain why antibiotics do not work on viral infections.

Answer 50

1. Target things only bacteria have | 2. Viruses use our system to reproduce to stop they would kill our cell as well

Question 51

Explain how a population of bacteria may develop resistance to an antibiotic.

Answer 51

1. You start with a population with no resistance o bacteria 2. A chance mutation in one bacterium produced a gene for antibiotic resistance- creating a population with a few antibiotic resistance bacteria 3. Antibiotic A applies a selection pressure- there is a strong natural selection for bacteria with a gene for antibiotic-resistance 4. This creates a population with mainly antibiotic-resistance 5. Continued selection pressure means almost all bacteria on the population will be antibiotic resistant

Question 52

Suggest two ways in which the use of antibiotics may be increasing the likelihood of resistance evolving.

Answer 52

1. Farmers using antibiotics in animal feed to prevent animals losing condition due to infection 2. Over subscription to antibiotics

Question 53

Give two examples of antibiotic resistant bacteria.

Answer 53

MRSA, C.difficile

Question 54

Suggest two methods used to reduce the likelihood of resistance developing in bacteria.

Answer 54

1. Minimising he use of antibiotics and ensuring every course of antibiotics is completed- reduces risk of resistant individuals surviving and developing into a resistant strain population 2. Good hygiene in hospitals, care home and in general- major impact on spread of all infections

Question 55

Explain why not completing a course of antibiotics may lead to antibiotic resistance developing.

Answer 55

1. Only weaker bacteria will be killed if you don't finish it which allows stronger bacteria to become resistant