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AQA A Level Biology 2018 > The Immune System > Flashcards

The Immune System Flashcards

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1
Q

What are Antigens?

A

Molecules that can generate an immune response when detected by the body.

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2
Q

Where are Antigens usually found?

A

On the surface of cells.

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3
Q

How are Antigens used?

A

To identify: pathogens, abnormal body cells, toxins and cells from other individuales of the same species (e.g. organ transplants)

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4
Q

What is a Phagocyte?

A

A type of white blood cell that carries out phagocytosis.

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5
Q

Where are Phagocytes found?

A

In the blood and in tissues.

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6
Q

How do Phagocytes work? (4)

A
  • phagocyte recognises the foreign Antigens on a pathogen.
  • cytoplasm of the phagocyte moves round the pathogen, engulfing it so the pathogen is now contained in a PHAGOCYTIC VACUOLE.
  • a lysosome fuses with the phagocytic vacuole and the lysozyme break down the pathogen.
  • the phagocyte then presents the pathogen’s Antigens - it sticks the Antigens on its surface to activate other immune system cells.
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7
Q

What happens after the Phagocytes have engulfed the pathogens?

A

Active T Cells

  • T cells have receptor proteins which bind to complementary Antigens presented to it by Phagocytes = actives them.
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8
Q

How do helper T cells react?

A

They release chemical signals that activate and stimulate Phagocytes.

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9
Q

What to cytotoxic T cells do?

A

They kill abnormal and foreign cells.

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10
Q

What do the helper T cells do?

A

CLÓNAL SELECTION

  • when the antibody on a BCell meets a complimentary shaped antigen, it binds to it.
  • this & substances released from helper T cells activate the B cells.
  • the activated B cell divides into plasma cells.
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11
Q

What are plasma cells?

A

Identical to B-Cells… they secrete loads of antibodies specific to the antigen…. MONOCLONAL ANTIBODIES.

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12
Q

Why can two pathogens bins to an antibody at the same time?

What is this called?

A

Because an antibody has two binding sites - this means pathogens can be clumped together.

AGGLUTINATION.

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13
Q

How can the immune response be split?

A

Cellular

Humoral

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14
Q

What is the Cellular immune response?

A

The T Cells and other immune system cells that they interact with.

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15
Q

What is the Humoral immune response?

A

B-Cells, clonal selection and the production of monoclonal antibodies.

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16
Q

What is the primary immune response?

A
  • when an antigen enters the body for the first time, it activates the immune system.
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17
Q

Why is the primary response slow, does it change?

A

Because there aren’t many B Cells that can make the antibody needed to bind to it.

Eventually the body will produce enough of the right antibody to overcome the infection.

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18
Q

What gets produced after a while?

A

T CELLS AND B CELLS PRODUCE MEMORY CELLS.

Memory T cells = remember the specific antigen and will recognise it again.
Memory B cells = record the specific antibodies needed to bind the antigen.

IMMUNITY

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19
Q

What is the secondary immune response?

A

If the same pathogen enters the body again, the immune response will be quicker and stronger.

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20
Q

What happens faster in the secondary immune response?

A

Clonal selection - memory B cells are activated and divide into plasma cells that produce the right antibody to the antigen.

Memory T cells are activated and divide into the correct type of T cells to kill the cell carrying the antigen.

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21
Q

What is HIV?

A

Human Immunodeficiency Virus - a virus that affects the immune system.

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22
Q

What does HIV lead to?

A

AIDS - acquired immune deficiency syndrome.

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23
Q

What is AIDS?

A

A condition where the immune system deteriorates and fails - they are more vulnerable to other infections.

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24
Q

What does HIV infect?

A

Helper T cells which acts as the host cells - this means you can’t have an effective response to infections (can’t activate Phagocytes etc)

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25
Q

People who have AIDS have…

A

A critically low level of helper T cells.

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26
Q

What is the structure of HIV like? (4)

A
  • core containing genetic material (RNA) and enzyme: reverse transcriptase which is needed for virus Replication.
  • attachment protein (to attach to host)
  • lipid envelope (stolen from host cell)
  • capsid (protein coat)
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27
Q

How does HIV replicate? (5)

A
  • the attachment protein attaches to a receptor molecule on the cell membrane of the host helper T cell.
  • the capsid is released into the cell, where it uncoats and releases genetic material.
  • reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template.
  • host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA.
  • the viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells.
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28
Q

What is the process of AIDS?

A
  • initial flu like symptoms.
  • as AIDS progresses, the number of immune system cells decreases further.
  • late stages of AIDS = very very low number of immune system cells = can develop a range of serious infections.
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29
Q

What can you develop with AIDS?

A
  • Toxoplasmosis (brain parasite infection)

- Candidiasis of the respiratory system (fungal infection)

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30
Q

Why can’t antibodies work on viruses?

A

Because viruses are INSIDE cells and antibiotics only target the bacterial enzymes and ribosomes - viruses use your own enzymes and ribosomes.

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31
Q

Is there a cure for HIV?

A

No - but antiviral drugs can be used to slow down the progression of HIV infection and AIDS.

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32
Q

How can a pregnant HIV positive woman reduce the change of her baby being HIV positive?

A

By taking antiviral drugs during pregnancy.

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33
Q

What does a Vaccines contain?

A

Antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease.

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34
Q

What is herd immunity?

A

When lots of people are vaccinated, people who are not vaccinated are less likely to catch the disease.

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35
Q

How can you take vaccines?

A

Usually injected

But can be taken orally

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36
Q

Why is it not good to take vaccines orally?

A
  • it could be broken down by enzymes in the gut / molecules may be too large to be absorbed.
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37
Q

What can some pathogens do so that your memory cells don’t recognise them the second time?

A

They change their surface Antigens.

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38
Q

Why is Antigenic variation bad?

A

It makes it difficult to develop vaccines against some pathogens.

39
Q

Why does the flu vaccine change every year?

A

Because the Antigens on the surface of the influenza virus change regularly.

40
Q

What is Active Immunity?

A

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

41
Q

What are the 2 types of active immunity:

A
  • natural: when you become immune after catching a disease.

- artificial: when you become immune after you’ve been given a vaccination containing a harmless dose of antigen.

42
Q

What is Passive Immunity?

A

The type of immunity you get from being given antibodies made by a different organism.

43
Q

What are the two types of Passive Immunity?

A
  • natural: when a baby becomes immune due to the antibodies it receives from its mother in breast milk etc
  • artificial: when you become immune after being injected with antibodies from someone else.
44
Q

Give 4 differences between active immunity and passive immunity:

A

Passive doesn’t require exposure to antigen

Protection is immediate in passive

Memory cells aren’t produced in passive

Protection is short term because the antibodies given are broken down in passive but it is long term because antibody is produced in response to complementary antigen being present in the body.

45
Q

What are Monoclonal antibodies?

A

Antibodies produced from a single group of genetically identical B Cells.

46
Q

Why are antibodies so specific?

A

Because their binding sites have a a unique tertiary structure that only one particular antigen can fit into.

47
Q

How can monoclonal antibodies be used to treat cancer? (3)

A
  • cancer cells have antígena called tumour markers and MA can be made to bind to these.
  • you can attach anti-cancer drugs to the antibodies.
  • when the antibodies come into contact with the cancer cells, they bind to the tumour markers.
48
Q

What are the side effects of an antibody based drug for treatment of cancer?

A

Lower than other drugs because they accumulate near specific cells and the drug will only target the cancer cells.

49
Q

What hormone do pregnancy tests detect?

A

Human Chorionic Gonadotropin - HCG.

50
Q

Where is the hormone HCG found?

A

In the urine of pregnant women.

51
Q

How can monoclonal antibodies be used in a pregnancy test? (3)

A
  • application area contains antibodies for HCG bonded to a coloured bead (blue)
  • when urine containing HCG bonds to the antibody on the blue beads, forms an antigen antibody complex.
  • the urine moves up the stick to the test strip carrying the blue beads with it.
52
Q

What does the test trip in a positive pregnancy test contain?

A

Antibodies to HCG that are stuck in place.

53
Q

So why does the test strip turn blue?

A

Because the immobilised antibody vines to any HCG - concentrating the HCG-antibody complex with the blue beads attached.

54
Q

What is HIV?

A

A virus that affects the immune system.

55
Q

HIV eventually leads to…

A

AIDS

56
Q

What is AIDS?

A

A condition where the immune system fails.

57
Q

How does HIV affect the immune system?

A
  • HIV uses helper T cells as their host cells.

- infects and eventually kills helper T cells.

58
Q

Why is it bad that HIV targets the helper T cells?

A

Because the helper T cells activate phagocytes, cytotoxic T cells and B Cells.

Without them, immune system can’t mount effective responses.

59
Q

How do viruses like HIV replicate?
STEP 1

What gets released into the T cell?

A
  • attachment protein attaches to a receptor molecule on the membrane of the host helper T cell.

Capsid is released into the cell where it uncoats and releases RNA into the cell’s cytoplasm.

60
Q

How do viruses like HIV replicate?
STEP 2

What is made and inserted into the human DNA?

A
  • inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template.

Double stranded DNA is made from this and inserted into the human DNA.

61
Q

How do viruses like HIV replicate?
FINAL STEP

What gets assembled?

A
  • host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA.

The viral proteins are assembled into new viruses - infect other cells.

62
Q

What are the symptoms of HIV like during the initial infection period?

A

Severe - flu like symptoms.

63
Q

What is the latency period?

A

Where HIV Replication drops to a lower level - this can last years and the infected person won’t experience any symptoms.

64
Q

During the late stages of AIDS, why can patient develop such severe infections?

A

Because patients have a very low number of immune system cells - it’s the serious infections that kills AIDS patients, not HIV itself.

65
Q

Give 2 examples of serious illnesses people with AIDS could develop:

A
  • toxoplasmosis (brain parasite infection)

- candidiasis of the respiratory system (fungal infection)

66
Q

What kind of infections do initial symptoms of AIDS cause?

A

Minor infections of mucous membranes - e.g. inside nose, ears.

67
Q

As AIDS progress, what kind of infections can patients get?

A

More serious ones like severe bacterial infections, tuberculosis etc

68
Q

What do Antibiotics target?

A

Bacteria by interfering with their metabolic reactions - target bacterial enzymes and ribosomes.

69
Q

Why can’t antibiotics treat viruses?

A

Because viruses use enzymes and ribosomes of the host cells (human cells) - antibiotics don’t target human processes.

70
Q

What are most antiviral drugs designed to target?

A

The few specific enzymes that exist - e.g. reverse-transcriptase inhibitors drugs.

71
Q

Is there a cure for HIV?

A

No - but antiviral drugs can be used to slow down its progression.

72
Q

How can HIV be controlled?

A

Reducing the spread.

73
Q

How is HIV spread?

A

Unprotected sex & sharing of body fluids.

74
Q

Give examples of ethical issues surrounding vaccines: (3)

A
  • vaccines tested on animals = unethical.
  • some people don’t want to take vaccines due to risk of side effects but they’re still protected because of herd immunity - some think this is unfair.
  • if there was an epidemic of a new disease, rush for vaccines = who would be the first to receive it?
75
Q

What’s an ethical issue surrounding the use of monoclonal antibody therapy?

A

Animal rights issues - animals are used to produce the cells from which the monoclonal antibodies are produced.

76
Q

What is the EILSA test?

A

A test which allows you too see if a patient had any antibodies to a certain antigen / an antigen to a certain antibody.

77
Q

What’s used in an ELISA test?

A

An antibody with an enzyme attached - the enzyme can react with a substrate to produce a coloured product.

78
Q

What does it mean if there’s a colour change in the ELISA test?

A

That there’s a antigen/antibody of interest present in the sample being tested.

79
Q

What does direct ELISA do?

A

Used a single antibody that is complementary to the antigen you’re testing for.

80
Q

What does the indirect ELISA do?

A

Uses two different antibodies.

81
Q

What can the indirect ELISA test be used to test for?

A

Can see if a patient possesses antibodies to the HIV virus.

82
Q

Using ELIA as a HIV test
Step 1

What must you do to the well?

A
  • HIV antigen is bound to the bottom of a well in a well plate.
  • sample of blood is added to the well - any HIV specific antibodies will bind to the antigen.

THE WELL IS THEN WASHED OUT TO REMOVE ANY UNBOUND ANTIBODIES.

83
Q

Using ELIA as a HIV test
Step 2

What must you do the well?

A
  • a secondary antibody with a specific enzyme attached to it is added to the well.

This antibody can bind to the HIV specific antibody (primary A)

THE WELL IS THEN WASHED OUT TO REMOVE UNBOUND SECONDARY ANTIBODY - if there’s no primary antibody, all secondary will be washed away.

84
Q

Using ELIA as a HIV test

FINAL STEP

A
  • a solution containing a substrate which is able to react with the enzyme attached to the secondary antibody to give a coloured product is added to the well.
85
Q

What happens if the solution changes colour during the ELISA test?

A

It indicates that the patient has HIV specific antibodies in their blood so has HIV.

86
Q

Why are the washing steps important in the ELISA test?

A

To make sure unbound antibodies aren’t left in the well which would affect the results.

87
Q

What is significant about 20% of women with breast cancer?

A

They have rumours that produce more than the usual amount of a receptor called HER2.

88
Q

What is Herceptin?

A

A drug used to treat a type of breast cancer. It contains MA which bind to the HER2 receptor on a tumour cell.

89
Q

What happened in 2005 with Herceptin?

A

A study tested it on women who had already undergone chemotherapy for a year and then a control group of other women without it.

90
Q

What were the results of the test on Herceptin?

A

Almost twice as many women in the control group developed breast cancer again/died.

91
Q

What was published in 1998?

A

A study which suggested a link between the MMR vaccine and autism.

92
Q

Why was the MMR scare deemed unreliable?

A
  • small sample size: 12 children.

- one scientist needed a lawsuit against MMR vaccine manufacturer = biased.

93
Q

What other studies have been carried out that contradict the MMR scare?

A

2005 Japanese study on 30,000 children - counted who developed autism before age 7.

94
Q

Why is a bigger sample better?

A

Can be certain the results aren’t just due to chance.

AQA A Level Biology 2018 (17 decks)

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