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1B > CGP The Immune System > Flashcards

CGP The Immune System Flashcards

1
Q

What are antigens?

A

Proteins that cam generate an immune response when detected by the body.
Usually found on the surface of cells.

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2
Q

Antigens are used by the immune system to identify…

A
  • pathogens
  • abnormal body cells
  • toxins
  • cells from other individuals from the same species (eg organ transplants)
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3
Q

Outline the primary immune response.

A
  1. When an antigen enters the body for the first time, it activates the immune system - the primary response.
  2. The primary response is slow because there aren’t enough B-cells that can make the antibody needed to bind to it.
  3. Eventually the body will produce enough of the right antibody to overcome the infection.
  4. After being exposed to the antigen, T and B cells will produce memory cells which will remain in the body for a long time.
    Memory T cells remember the specific antigen and will remember the second time around.
    Memory B cells record the specific antibodies needed to bind to the antigen.
  5. The person is now immune - their immune system has the ability to respond quickly to a second infection.
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4
Q

Outline the secondary immune response.

A
  1. If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response.
  2. Clonal selection happens faster.
    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.
  3. The secondary response often gets rid of the pathogen before you show the symptoms.
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5
Q

How do vaccines work?

A

Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease.
Meaning you become immune without any symptoms.

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6
Q

How can vaccines protect individuals and populations against disease?

A

Vaccines protect individuals who have them and, because they reduce the occurrence of the disease, those not vaccinated are less likely to catch it (because there are fewer people to catch it from). This is herd immunity.

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7
Q

Outline antigenic variability.

A
  • when you are infected a second time with the same pathogen (with the same antigens on the surface), they activate the secondary response so you don’t get ill.
  • however some pathogens can slightly change their surface antigens.
  • this means when you’re infected for a second time, the memory cells produced from the 1st infection will not recognise the different antigens. So the immune system has to restart another primary response against these new antigens.
  • the primary response takes time to get rid of the infection, so you get ill again.
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8
Q

What is active immunity?

A

When your immune system makes its own antibodies after being stimulated by an antigen. There are two different types.

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9
Q

What is natural, active immunity?

A

When you become immune after catching a disease.

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10
Q

What is artificial active immunity?

A

When you become immune after you’ve been given a vaccination containing a harmless dose of an antigen.

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11
Q

What is passive immunity?

A

When you have been given antibodies made by a different organism - your immune system doesn’t produce antibodies on its own.

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12
Q

Outline natural passive immunity.

A

When a baby becomes immune due to the antibodies it receives from its mother through the placenta and in breast milk

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13
Q

Outline artificial passive immunity.

A

When you become immune after being injected with antibodies from someone else.
Eg if you contract tetanus, you can be injected with antibodies against the tetanus toxin, collected from blood donations.

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14
Q

Differences between active and passive immunity?

A

ACTIVE:

  • requires exposure to antigen
  • takes a while for protection to develop
  • memory cells are produced
  • protection is long time because the antibody is produced (after activation of memory cells) in response to complementary antigen being present in the body

PASSIVE:

  • doesn’t require exposure to antigen
  • protection is immediate
  • memory cells aren’t produced
  • protection is short term because the antibodies given are broken down
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15
Q

What are monoclonal antibodies?

A

Antibodies produced from a single group of genetically identical B cells (plasma cells). This means they’re all identical in structure.

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16
Q

What does the ELISA test stand for?

A

Enzyme linked immunosorbent assay

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17
Q

What does the ELISA test do?

A

Allows you to see if a patient has any antibodies to a certain antigen, or any antigens to a certain antibody.

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18
Q

What are the ethical issues surrounding vaccines?

A
  • all vaccines are tested on animals before they’re tested on humans.
  • some people don’t want to take vaccines due to the risk of side effects. But they are still protected due to herd immunity.
  • testing vaccines on humans can be tricky, eg volunteers may put themselves at unnecessary risk of contracting the disease because they think they’re fully protected.
  • if there was an epidemic of a new disease, there would be a rush to get the vaccine and there would be a difficult decision about who would be the first to receive it.
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19
Q

What is a phagocyte?

A

A type of white blood cell that carries out phagocytosis. They are the first cells to respond to an immune system trigger inside the body.

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20
Q

Where are phagocytes found?

A

In the blood and in tissues.

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21
Q

How do phagocytes engulf pathogens?

A
  1. The phagocyte recognises the foreign antigens on a protein.
  2. The cytoplasm of the phagocyte engulf the pathogen.
  3. The pathogen is now contained in a phagocytic vacuole.
  4. A lysosome fuses with the phagocytic vacuole. And the lysosomes engulf the pathogens.
  5. The phagocyte then presents the pathogen’s antigens - to activate other immune system cells.
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22
Q

How do phagocytes activate T cells?

A

T cells have receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes (activating the T cell).

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23
Q

Different type of T cells do different things. What do helper T cells do?

A

Th (helper T) cells release chemical signals that activate and stimulate phagocytes and cytotoxic T cells, which kill abnormal / foreign cells.

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24
Q

Outline how T cells activate B cells, which divide into plasma cells.

A
  1. When an antibody on the surface of a B cell meets a complementary shaped antigen, it binds to it.
  2. This, together with substances released from Th cells activates the B cell (clonal selection).
  3. The activate B cell divides into plasma cells.
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25
Q

What is the final stage in which pathogens are removed from the body?

A

One antibody can bond to 2 pathogens at the same time (as the antibody has 2 binding sites).
This means the pathogens clump together (aka as an agglutination).
Phagocytes then bind to the antibodies and phagocytosis many pathogens at once. This process leads to the destruction of pathogens carrying this antigen in the body.

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26
Q

What determines the antigen binding site?

A

The specificity of an antibody depends on its variable region, which forms the antigen binding sites.

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27
Q

All antibodies have the same ___________ _________.

A

Constant region.

28
Q

The immune response can be split into…?

A

The clonal and humoral response.

29
Q

What is the humoral response?

A

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

30
Q

What forms the clonal response?

A

T-cells and the other immune system cells they interact with eg phagocytes.

31
Q

Outline the primary immune response.

A
  1. An antigen enters the body for the first time, activating the immune system.
  2. This is the primary response, and is slow because there aren’t many B-cells that can make the antibody needed to bind to it.
  3. Eventually, the body produces enough of the specific antibody to overcome the infection. Meanwhile the person shows symptoms.
  4. After being exposed to the antigen, B and T cells produce memory cells which remain in the body for a long time. Memory B cells record the specific antibodies needed to bind to the antigen, whilst memory T cells remember the specific antigen and will remember it a second time around.
  5. The person is now immune - they have the ability to respond quickly to an antigen.
32
Q

What is the secondary immune response?

A
  1. If the same pathogen enters the body again, the immune system produces a quicker, stronger immune response.
  2. Clonal selection happens faster. Memory B cells are activated, and divide into plasma cells that produce the correct antibody to antigen. Memory T cells are activated and divide into the correct type of T cells to kill the cell carrying the antigen.
  3. This secondary response often gets rid of the pathogen before you show symptoms (you’re immune to the pathogen).
    3.
33
Q

Outline how vaccinations work.

A

Vaccines contain antigens (which may be free or attached to dead or attenuated (weakened) pathogens) that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease.

34
Q

Why are vaccines not usually take orally?

A

Because it could be broken down by enzymes in the gut.

Or the molecules may be too large to be absorbed into the blood.

35
Q

What is antigenic variability?

A

Different antigens are formed due to changes in the genes of the pathogens.

This means that when infected for a second time, the memory cells produced from the primary response will not recognise the different antigens. So the antigens will have to carry out primary response again.

36
Q

Why is it difficult to produce vaccinations against some pathogens (eg the influenza virus)?

A

Antigenic variation.

  1. The antigens on the surface of the influenza virus change regularly, forming new strains of the virus.
  2. Memory cells produced from a vaccination with one strain of flu will not recognise other strains with different antigens (the strains are immunology distinct).
37
Q

Immunity can be either ________ or ________.

A

Active or passive.

38
Q

What is active immunity?

A

When your immune system makes its own antibodies after being stimulated by an antigen.

39
Q

Outline the two different type sod 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 the pathogen.

40
Q

What is passive immunity?

A

The type of immunity you get from being given antibodies made by a different organism - your immune system doesn’t produce any of its own antibodies.

41
Q

What are the 2 types of passive immunity?

A

Natural - a baby becomes immune due to the antibodies it receives from its mother, via the placenta or breast milk.

Artificial - you become immune after being injected with antibodies from someone else. Eg if you contract tetanus, you can be injected with antigens against the tetanus toxin collected from blood donations.

42
Q

Active or passive immunity: memory cells are produced?

A

Active.

43
Q

Active or passive immunity: memory cells aren’t produced.

A

Passive

44
Q

Active or passive immunity: requires exposure to antigen.

A

Active.

45
Q

Active or passive immunity: doesn’t require exposure to an antigen.

A

Passive.

46
Q

Active or passive immunity: protection is immediate.

A

Passive

47
Q

Active or passive immunity: protection is short term. Why?

A

Passive.

Short term because the antibodies given are broken down.

48
Q

Active or passive immunity: protection is long term. Why?

A

Active.

Because the antibody is produced (after activation of memory cells) in response to complementary antigen being present in the body.

49
Q

Why are all monoclonal antibodies similar in structure?

A

Because they’re produced from a single group of genetically identical B cells (plasma cells)

50
Q

Why are antibodies very specific?

A

Because their binding sites have a unique tertiary structure that will only bind to one particular antigen (with a complementary shape).

51
Q

How do pregnancy tests work?

A
  1. The application area contains antibodies for HcG bound to blue beads.
  2. The test strip contains antibodies to HcG that are immobilised.
  3. If there is HcG present, the test strip turns blue because to immobilised antibody binds to any HcG - concentrating the HCG-antibody complex with the blue beads attached. If no hCG is present, the beads will pass through the test area without binding to anything, so it won’t go blue.
52
Q

What is the ELISA test?

A

The ELISA test allows you to allows you to see if a patient has any antigens to a certain antigen. Or any antigen to a certain antibody.

53
Q

How does the ELISA test work?

A

An antibody is used which has an enzymes attracted to it. This enzyme can react with a substrate to produce a coloured product, causing the solution in the reaction solution to change colour.

If there is a colour change, it demonstrates that the antigen or antibody of interest is present in the sample being tested.
(In some ELISA tests, the quantity of the antigen / antibody can be determined by the intensity of the colour change).

54
Q

What are the two different types of ELISA test?

A

Direct and indirect.

55
Q

Outline the direct ELISA test.

A

Direct ELISA uses a single antibody that is complementary to the antigen you’re testing for.

56
Q

How is the indirect ELISA test different to the ordinary direct test?

A

The indirect ELISA test uses two different antibodies.

57
Q

What are the ethical issues regarding vaccinations?

A
  • all vaccines are tested on animals before humans.
  • some people don’t want the vaccine due to the side effects, but are still protected because of herd immunity; other people think this is unfair.
  • if there was an epidemic of a new disease, there would be a rush to receive the vaccine, and difficult decisions would have to be made about who is the first to receive it.
  • testing on humans may also be wrong; eg patients may put the,selves at unnecessary risk of contracting the disease because they they think they’re fully protected (eg they may have unprotected sex because they think they’re protected with the HIV vaccine; but the vaccine might not work).
58
Q

What is HIV?

A

A virus that affects the immune system and eventually leads to AIDS.

59
Q

HIV causes AIDS. But what is AIDS?

A

A condition where the immune system deteriorates and eventually fails. This makes the person more vulnerable to other infections eg pneumonia.

60
Q

What is the structure of HIV?

A
  • a core that contains the genetic material (RNA) and some proteins (including reverse transcriptase (enzyme), needed to virus replication).
  • a capsid.
  • an envelope (extra outer layer) made of the membrane taken from the cell membrane of the previous host cell.
  • lots of attachment proteins that help HIV to attach to the hoist helper T cell.
61
Q

How does HIV replicate?

A
  1. The attachment protein attaches to a receptor molecule on the cell membrane of the host helper T cell.
  2. The capsid is released into the cell, where it uncoats and releases RNA into the cell’s cytoplasm.
  3. Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template.
  4. From this, double stranded DNA is made and inserted into human DNA.
  5. Host cell enzymes are used to make viral enzymes from the viral DNA found within human DNA.
  6. The viral proteins are assembled into new viruses, which bud from the cell and go on to infect other cells.
62
Q

Why don’t antibodies work against viruses?

A

Because antibiotics interfere with metabolic reactions of bacterial enzymes and ribosomes used.
However, viruses don’t have these, so use the enzymes and ribosomes of the host cell.
Therefore, antibiotics don’t target and thus inhibit these metabolic reactions because they do not target human processes.

63
Q

What are antiviral drugs?

A

Most antiviral drugs are designed to target the few virus specific enzymes (enzymes that only the virus uses).

Eg HIV uses reverse transcriptase to replicate, but human cell don’t use this enzyme, so drugs can be designed to inhibit it without affecting the host cell (aka reverse transcriptase inhibitors).

64
Q

Where does HIV replicate?

A

Inside helper T cells of the host.

65
Q

Why does HIV replicate in help T host cells?

A

Because HIV doesn’t have the equipment (eg enzymes and ribosomes) to replicate on its own.

66
Q

How does HIV replicate?

A
  1. The attachment protein attaches to a receptor molecule on the cell surface membrane of the host helper T cell.
  2. The capsid is released into the cell, where it uncoats and releases RNA (genetic material) into cell’s cytoplasm.
  3. Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template.
  4. From this, double stranded DNA is made, and inserted into the human DNA.
  5. Host cell enzymes are used to make viral proteins from the viral DNA.
  6. The viral proteins are assembled into new proteins, which bud from the cell and go on to infect other cells.

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