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Biology AS > Cell Recognition 3.2 > Flashcards

Cell Recognition 3.2 Flashcards

1
Q

What are antigens?

A

They are molecules which can generate an immune response when detected by the body, they are proteins found on the outside of cells.

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2
Q

What are foreign antigens?

A

Antigens that are not normally found in the body.

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3
Q

What are pathogens?

A

Organisms that cause disease.

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4
Q

What are some examples of pathogens?

A

Bacteria, viruses and fungi.

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5
Q

What are examples of abnormal body cells?

A

Cancerous or pathogen-infected cells.

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6
Q

What can the immune system respond to as well as pathogens?

A

Toxins.

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7
Q

Why do organ transplant recipients take drugs?

A

This is because they will have some foreign antigens and these will trigger an immune response and lead to rejection.

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8
Q

What are the most important antigens in blood transfusions?

A

The ABO blood group antigens. A and B antigens not recognised by the recipient’s immune system will generate an immune response.

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9
Q

What happens if two individuals are closely related?

A

They have more antigens in common.

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10
Q

What is involved in non-specific immune response?

A

Phagocytosis.

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11
Q

What is involved in specific immune response?

A

T cells, B cells and antibody production.

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12
Q

What is phagocytosis?

A

The cellular process of engulfing solid particles using the cell membrane.

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13
Q

Where are phagocytes made?

A

In the bone marrow.

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14
Q

Where do phagocytes travel through?

A

In capillaries but they can squeeze through walls into tissues.

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15
Q

What are the two types of phagocytes?

A

Neutrophils and macrophages.

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16
Q

What do phagocytes do?

A

Patrol the body in search for invaders (non-self antigens).

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17
Q

What do neutrophils do?

A

Engulf and digest pathogens as well as dead human cells.

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18
Q

What do macrophages do?

A

They can punch holes in the bacteria or stick proteins to the outside of the bacteria to make them more appealing for the neutrophils to destroy.

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19
Q

What are the key stages of phagocytosis?

A
  1. The phagocyte recognises the foreign antigens on the pathogen.
  2. The cytoplasm moves and engulfs the pathogen.
  3. This is now contained in a phagocytic vacuole.
  4. A lysosome fuses with this vacuole and allows for lysozymes to break it down.
  5. The phagocyte then presents the pathogens antigens on itself in order to active other immune system cells.
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20
Q

Why is phagocytosis not enought to cope with large numbers of pathogens?

A

It is a non-specifc response.

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21
Q

When phagocytes become antigen presenting cells what does it signal?

A

The t-lymphocytes, which start a specific immune response.

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22
Q

What are the two types of lymphcytes?

A

T and B cells.

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23
Q

Where are lymphocytes made?

A

In bone marrow.

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24
Q

Where do T cell mature?

A

In the thymus gland.

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25
Q

What type of lymphocytes produce antibodies?

A

B cells.

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26
Q

What is the activation of B and T cells called?

A

Clonal Selection.

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27
Q

How do lymphocyte cells clone themselves?

A

Through mitosis.

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28
Q

What are the three types of T cells?

A

Helper, memory and cytotoxic.

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29
Q

What do T Helper cells do ?

A

They release chemical signals in order to activate and stimulate phagocytes as well as activating B cells.

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30
Q

What do T Cytotoxic cells do?

A

They kill foreign and abnormal cells in the body.

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31
Q

What are B cells coverd in?

A

Antibodies.

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32
Q

What does each B cell have?

A

A different shaped antibody on its membrane which is complementary to specifc antigens.

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33
Q

What do activated B-cells divide into?

A

Plasma cells.

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34
Q

What are plasma cells?

A

Antibody producing cells.

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35
Q

What do plasma cells do?

A

Secrete monoclonal antibodies, which bind to the antigen on the pathogens and form many antigen-antibody complexes.

36
Q

What is the benefit of having two binding sites?

A

The cell is able to bind to two pathogens at the same time.

37
Q

What is agglutination?

A

This is when two pathogens are binded to the same plasma cell at the same time and end up clumped together.

38
Q

What happens after agglutination?

A

Phagocytes bind to the antibodies and destroy them.

39
Q

What are antibodies made up of?

A

Two heavy and two light chains.

40
Q

What does each antibody have?

A

A variable region which has its own unique teritary structure, allowing it to be complementary to one specific antigen.

41
Q

What is the same in all antigens?

A

They have the same constant region.

42
Q

When does cellular immunity happen?

A

Inside cell which have been infected and is mediated by t-lympohcytes. It becomes an antigen presenting cell and then undergos lysis.

43
Q

What is humoural immunity?

A

It is where B cells differentiate into plasma cells which can produce antibodies for a specifci antigen.

44
Q

What are the two types of active immunity?

A

Natural and artificial.

45
Q

What is natural active immunity?

A

This is when you become immune after catching the disease.

46
Q

What is artifical active immunity?

A

This is when you become immune after being given a vaccinne.

47
Q

What is active immunity?

A

This is when your immune system produces it’s own antiboies for the disease from the stimulation by an antigen.

48
Q

What is passive immunity?

A

This is when you are given antibodies from a different organism.

49
Q

What are the two types of passive immunity?

A

Natural and artifical.

50
Q

What is natural passive immunity?

A

When a baby recieves antibodies from their mother through the placenta and breastmil.

51
Q

What is artifical passive immunity?

A

When you are injected with antibodies from someone else, sometimes through blood donations against the tetanus toxin.

52
Q

What is a vaccination?

A

When a dead or attenuated foreign organism is introduced to the body through an injection in order to stimulate production of antibodies in the body and to create memory cells.

53
Q

What is herd immunity?

A

When a certain percentage of the population is vaccinated to prevent it from spreading far or quickly within the population to protect those who are unable to get a vaccine.

54
Q

What is antigenic variation?

A

This is where pathogens are able to change their antigens, this causes the body to be unable to recognise it when it reinfects the body as it is nit exactly the same.

55
Q

Why does antigentic variation make it difficult ot develop vaccines?

A

The new strains of the pathogen are immunologically distinct.

56
Q

What was the MMR 1998 vaccine study on?

A

Twelve children who are autistic.

57
Q

What is herceptin?

A

A drug used to treat breast cancer, the type where the tumour produces more than the usual amount of HER2.

58
Q

What does herceptin contain?

A

Monoclonal antibodies which prevent the cells from growing and dividing.

59
Q

What are the three ways in which antibodies work?

A
  1. Agglutination.
  2. Neutralising Toxins.
  3. Preventing viruses from entering cells.
60
Q

Why is agglutination beneficial?

A

It allows for phagocytes to engulf more of them at once.

61
Q

How can monoclonal antibodies be made?

A
  1. Inject a mouse with the pathogen.
  2. Plasma cells produce antibodies.
  3. Lymphocytes are removed and fused with rapidly dividing mouse tumour cells.
  4. These new cells are called hybridomas.
  5. They divide and release lots of antibodies which are collected.
62
Q

How can monoclonal antibodies be used?

A
  1. For target medication.
  2. Pregnancy Test.
  3. Medical diagnosis through the ELISA test.
63
Q

What are antibodies?

A

Antibodies are proteins which are specific to an antigen as they have a complementary shape. Antibodies can bind to antigens to form an antigen-antibody complex.

64
Q

What is an antigen?

A

An antigen is a protein found on the outside of cells, that triggers an immune response.

65
Q

What happens in agglutination?

A

Antibodies cause microbes to clump together to make it easier for phagocytes to engulf more of them at once.

66
Q

What do killer t-cells do?

A

Killer T-cells find and destroy infected cells that have been turned into virus-making factories. To do this they need to tell the difference between the
infected cells and healthy cells with the help of special molecules called antigens.

67
Q

What do helper t-cells do?

A

Helper T-cells don’t make toxins or fight invaders themselves. Instead, they are like team coordinators. They use chemical messages to give instructions to the other immune system cells.
These instructions help Killer T-cells and B-cells make a lot more of themselves so they can fight the infection.

68
Q

How do anti-cancer drugs work?

A

They involve the use of monoclonal antibodies which are made to specifically bind to the tumour markers on the cancer cells. You can attach these drugs to antibodies so that the drug accumulates where the cancer is.

69
Q

How do pregnancy tests work?

A

The application area contains antibodies that are complementary to the hCG protein, bound to a blue coloured bead.

When urine is applied to the application area any hCG will bind to the antibody on the beads, forming an antigen-antibody complex.

The urine moves up the stick, carrying the beads with it.

The test strip contains antibodies to hCG that are stuck in place (immobilised).

If there is hCG present the test strip turns blue because the
immobilised antibody binds to any hCG concentrating the
hCG-antibody complex with blue beads attached.

If no hCG is present, the beads will pass straight through the test area without binding to anything, so it won’t turn blue.

70
Q

What is the purpose of an ELISA test?

A

To see whether a patient has any antibodies to a certain antigen or any antigen to a certain antibody.

71
Q

What are the two types of the ELISA test?

A

Direct and indirect.

72
Q

What is a direct ELISA test?

A

This just involves one antibody binding to an antigen – used to look for the presence of an antigen in a sample.

73
Q

What is an indirect ELISA test?

A

This uses multiple antibodies and can be used to look for antibodies that are
complimentary to a specific antigen in a sample

74
Q

What are the steps for a direct ELISA test?

A

A patients sample containing antigens are bound to the inside of a well plate.

A known detection antibody (with an attached enzyme) that is complementary to the antigen of interested is added.

If the antigen of interest is present in the patient sample, it will be immobilised on the inside surface of the well.

The detection antibody will bind to it.

The well is then washed out to remove any unbound antibody and a substrate solution is added.

If the detection antibody is present, the enzyme reacts with the substrate to give a colour change. This is a positive result for presence of the antigen. The intensity of the colour change can indicate the concentration of the antigens from the pathogen are present.

75
Q

What are the steps for an indirect ELISA test?

A

A known antigen from a pathogen is bound to the bottom of a well plate.

A sample of the patient’s blood plasma (which might contain several different antibodies) is added to the well. If there are any specific antibodies in the plasma, they will bind to the antigen stuck to the bottom
of the well. The well is then washed out to remove any unbound antibodies.

A secondary antibody, that has a specific enzyme attached to it, is added to the well. This secondary antibody can bind to the first primary antibody. The well is washed out again to remove any unbound secondary
antibody. If there’s no primary antibody in the sample, all of the
secondary antibody will be washed away because there will be nothing to bind to.

A solution is added to the well. The solution contains a substrate, which reacts with the enzyme attached to the secondary antibody and produces a colour product. If the solution changes colour, it indicates the patient has specific antibodies in their blood and is infected.

76
Q

Describe the efficiency of ELISA tests.

A

Indirect ELISAs can be more sensitive than direct detection
methods, but there is also the risk of cross-reactivity with the
antigen, which could cause higher background readings.

Indirect ELISAs also take longer due to the extra step. An
advantage is that you can use the same secondary antibody
(with the enzyme) for multiple different assays.

77
Q

What does HIV do?

A

HIV infects and kills helper T-cells, which act as host cells for the virus.

78
Q

What should healthy T count be?

A

A healthy T cell count should be between 500 and 1,600 T cells per cubic millimeter of blood (cells/mm3). But AIDS is defined as below 200 cells/mm3 (cells per cubic millimeter).

79
Q

When does HIV become AIDS?

A

When T helper cell numbers reach a critically low level.

80
Q

What does HIV cause?

A

Helper T-cells send chemical signals that activate phagocytes, cytotoxic T-cells and B-cells in the immune system.
Without enough helper T-cells, the immune system is unable to mount an effective response to infections.

81
Q

What happens during the initial infection period of HIV?

A

During the initial infection period, HIV replicates rapidly

The person may experience severe flu-like symptoms

After this, HIV replication drops to a lower level = latency period.

82
Q

What happens during the latency period of HIV?

A

During the latency period, which can last for years, the infected person won’t experience symptoms. Virus ‘hides’ within T helper-cells

Latency period can be lengthened with antiviral medication

83
Q

What are the way HIV can be transmitted?

A

Unprotected sex with an infected person, use of infected blood in a blood transfusion and mother to child or a child drinking a mother’s milk, known as vertical transmission.

84
Q

What are the key structures of HIV?

A

Phospholipid Envelope (stolen) –
outer layer

Capsid (protein coat )– protects
genetic information

2 strands of RNA (can be DNA in
others)

Reverse transcriptase enzyme – turns RNA in to DNA

Glycoprotein (attachment/envelope proteins) – antigens which bind to hosts helper T-cells.

85
Q
A

Biology AS (12 decks)

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