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1B > The Immune System > Flashcards

The Immune System Flashcards

1
Q

What is a phagocyte?

A

A white blood cell that carries out phagocytosis.

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2
Q

Where are phagocytes found?

A

In the blood and in tissues

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3
Q

What does the immune system do?

A

It recognises and destroys foreign cells, pathogens, abnormal cells or toxins.

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4
Q

Main difference between phagocytes and lymphocytes?

A

Phagocytes are non-specific: they ingest and destroy any pathogen.

However lymphocytes are specific: they attach only one type of antigen.

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5
Q

How are B lymphocytes and T lymphocytes different?

A

The lymphocytes have gone through a maturing process which begins before birth.

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6
Q

What do B lymphocytes do?

A

They mature in bone marrow and release antibodies into the blood.

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7
Q

What do T lymphocytes do?

A

Mature in the thymus. They cause a cellular response to infection (and do not release antibodies into the blood).

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8
Q

Define antigen.

A

A large ‘foreign’ molecule that stimulates an immune response (including antibody generation).

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9
Q

Example of antigens?

A

Proteins, glycoproteins and lipoproteins (all large and complex molecules).

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10
Q

Define antibody.

A

A protein released by a B lymphocytes in response to a non self organism.

Each antibody binds with a specific antigen.

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11
Q

How can antibodies bind to one or more bacterium or virus?

A

Because they have at least two sides where they can bind to an antigen - meaning they can bind to one or more bacterium or virus.

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12
Q

What is an agglutination?

A

Antibodies have at least two sides where they can bind to an antigen - meaning they can find to more than one bacterium. When the his happens, a network of antibodies and particles form a clump known as an agglutination.

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13
Q

How many polypeptide chains does a T cell have?

A

2

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14
Q

If a pathogen gets into your body, an inflammatory response if your second line of defence. What type of response is this?

A

Non-specific.

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15
Q

What does a non-specific response mean?

A

That response is the same for all pathogens.

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16
Q

There are many different types of _____ blood cells.

A

White

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17
Q

Where are phagocytes found?

A

In the blood and in tissues.

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18
Q

Phagocytes are the _____ cells to respond to an immune system trigger inside the body.

A

First

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19
Q

Explain phagocytosis.

A
  1. A phagocyte recognises foreign antigens on a pathogen.
  2. The cytoplasm of the phagocyte engulfs the pathogen.
  3. The phagocyte is now contained in a phagocytise vacuole in the cytoplasm of the phagocyte.
  4. A lysosome fuses with the phagocytise vacuole. And the lysosomes break down the pathogen.
  5. The phagocyte then presents the pathogen’s antigens on its surface to activate other immune system cells.
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20
Q

What happens in the third line of response?

A

The body is able to recognise foreign cells and target particular pathogens in a specific immune response.

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21
Q

What happens if the second line of defence fails?

A

The third line of defence occurs.

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22
Q

Examples of the first line of defence.

A

Skin, membranes, tears, saliva.

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23
Q

In the immune system, what are surface proteins important for?

A

Enabling the body to recognise its own cells (self) and the cells of pathogens that are invading the body (non-self)

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24
Q

How does the release of a chemical called histamine help neutrophils (a phagocyte) leave the blood?

A

By making the walls of the capillary leaky.

Histamine is released by a mast cell (a type of WBC) when tissues outside the circulatory system are damaged. It causes capillary walls to become more permeable so that they lose more fluid to the surroundings. This leads to localised swelling.

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25
Q

Are phagocytes specific or non-specific?

A

Non-specific (its the second line of defence).

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26
Q

What WBC is a specific response?

A

Lymphocytes.

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27
Q

What must happens before lymphocytes work?

A

They must go through a maturing process before they are capable of fighting infection.

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28
Q

What does the maturing process of a lymphocyte lead to?

A

Two types of lymphocytes : B lymphocytes and T lymphocytes

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29
Q

Where do B lymphocytes mature? What do they do?

A

They mature in bone marrow and release antibodies into the blood.

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30
Q

Where do T lymphocytes mature? What do they do?

A

T lymphocytes mature in the thymus. They cause a cellular response to infection (and do not release antibodies into the blood).

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31
Q

Define antigen.

A

A large, foreign molecule that stimulates an immune response (eg antibody generation).

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32
Q

Example of antigens.

A

Proteins, glycoproteins, lipoproteins

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33
Q

Define antibody

A

A protein released by a B cell in response to a non-self antigen.

34
Q

What does an antibody look like?

A

Every antibody has at least one Y-shaped molecule made of 4 polypeptide chains (quaternary structure).

35
Q

In an antibody, what holds the polypeptides together?

A

Disulphide bridges.

36
Q

How can antigens and antibodies fit into one another?

A

They have complementary molecular shapes - so can fire into each other to form an antigen-antibody complex.

37
Q

How is an antigen-antibody complex formed?

A

When an antibody randomly collides with a cell that’s carrying a non-self antigen that has a similar shape, it binds to the antigen.

38
Q

Define antigen-antibody complex.

A

The complex formed when an antigen binds with a complementary antibody.

39
Q

How can antibodies bind yo more than one pathogen?

A

Because antibodies have at least two sites where they can bind to an antigen, so can bind to more than one bacterium or virus

40
Q

Define agglutination in the context of antigen-antibody complex.

A

Because of the two binding sites of an antibody, they can bind to more than one bacteria or virus. When this happens, a network of antibodies form a clump.

41
Q

How do antigen-antibody complexes work in the immune system?

A
  • the binding of antibodies to the antigen can neutralise the pathogen.
  • the binding of antibodies to the antigen can act as a ‘marker’ which attracts the phagocytic cells to engulf and destroy the cell bearing it.
42
Q

How is each B cell different?

A

Because each B cell has a unique shaped receptor on its surface membrane.

43
Q

What happens when a B cell has a receptor with a complementary shape to an antigen that has entered your blood?

A

The receptors bind to this antigen.
The B cells rapidly divide by mitosis to form a large number of daughter cells.
Since the daughter cells are genetically identical they form a clone.
The majority of cells on the clone become plasma cells (which release antibodies).
A smaller number became memory cells and remain in circulation king after the antigen is destroyed.
They can rapidly divide to produce clones if plasma cells of re exposed to their complementary antigen.

44
Q

What are antibodies made of?

A

Chains of amino acids (they are a protein).

45
Q

What is a macrophage?

A

A type of phagocytic cell (eg neutrophil).
Once a macrophage has ingested and partly digested a pathogen, it may transfer some of the pathogen’s antigens to its own surface membrane to then become an antigen presenting cell.

46
Q

What are the three differences between a T cell and B cell?

A
  • T cell has only 2 polypeptide chains.
  • T cell is never released as an antibody into the blood. B cells divide into daughter cells through osmosis, with the majority of the cells in the clone becoming plasma cells which release antibodies.
  • T cells only respond to an antigen if this antigen is present on the surface of a macrophage that has become an antigen presenting cell. B cells however respond to an antigen when its receptors have a complementary shape to shape of an antigen on a cell.
47
Q

How do T cells work?

A

The T cell has receptor proteins on its surface that bind to complementary antigen presented to it by phagocytes.
The T cell then divided rapidly to produce a clone of cells through mitosis.
Following cell division, the cells in each clone differentiate into more than one type of T cell.

48
Q

What are the four types of T cell?

A
  • cytotoxic T cell
  • helper T cell
  • memory cell
  • suppressor T cell
49
Q

What do memory T cells do?

A

Remain in the blood and cause a rapid increase in the number of T cells when re-exposed to their specific antigen.

50
Q

What do helper T cells do?

A

Helper T cells assist other WBC in the immunological response.

51
Q

Example of what helper T cells can do.

A

By releasing chemical messengers, called cytokines, they stimulate:

  • formation of memory T cells
  • activation of phagocytes
  • maturation of B cells into plasma cells that secrete antibody
  • activation of cytotoxic T cells that destroy tumour cells and cells activated with the virus.
52
Q

Why is there a time gap between the first injection of the antigen and an increase in concentration of antibody in the blood?

A

The first increase of antibody in the blood is the primary response.
The short delay between the injection of antigen and primary response is the time for a complementary, specific B cell to collide randomly with the antigen to form an antibody-antigen complex and then divide to form a clone of plasma cells that release their antibodies (and increase their concentration).

53
Q

After the first injection of an antigen, why would the concentration of antibody in the blood decrease (after just increasing)?

A

Because as antibodies destroy the pathogen, fewer and fewer B cells are made - so the concentration of the antibody falls.

54
Q

How can a secondary response result in a higher concentration of antibody in the blood?

A

After the first response, many memory cells that are specific for the antigen remain in the blood. As a result, the memory cells are much more likely to collide with the antigen and bind with it.

In addition, a larger number of plasma cells are produced, so the concentration of antibodies is higher during the secondary response.

55
Q

Why are lymphocytes a specific immune response?

A

Because their surface receptors have a shape complementary to only one antigen.

56
Q

Memory cells can only be effective against a pathogen if…

A

It always has the same antigen (as otherwise it can’t bind).

57
Q

Define antigenic variability.

A

As a result of gene mutations, some pathogens frequently change the antigens in their surface (eg the cold virus)

58
Q

Why do we get colds every winter?

A

Because the cold virus shows antigenic variability.

Therefore as a result of gene mutations, these pathogens have antigens that are no longer complementary to the surface receptors of the memory cells remaining from the cold last year - so will not have a secondary response so will catch a cold again.

59
Q

How can scientists become confident in their hypothesis for it to then become a theory?

A

Scientists use the hypotheses to make predictions and devise experiments to test the predictions.

If their results are always consistent with their predictions, they can become confident.

60
Q

Define inert.

A

It will not react with anything.

61
Q

How are vaccines made harmless? (4 points)

A
  • killing the pathogen in a way that leaves its antigens unaffected
  • weakening the pathogen in a way that leaves its antigens unaffected (weakened pathogen are said to be attenuated)
  • using antigens to produce less harmful toxoids
  • using genetically engineered eukaryotic cells eg yeast to produce an antigen
62
Q

What is a vaccine?

A

A preparation of an antigen from a pathogen, but made safe by weakening or killing the pathogen (but in a way that leaves antigens unaffected).

63
Q

What happened after you’re vaccinated?

A

After the first treatment (primary response), you make antibodies against the antigens and you also make memory cells.

After the second treatment, you show secondary response, making large numbers of B cells and memory cells. These memory cells are then able to react rapidly if a new pathogen bearing the same antigen as the vaccine enters the body, killing the antigen before it does any harm.

64
Q

When does herd immunity occur?

A

When the vaccination of a significant portion of a population provides some protection for individuals who have not developed immunity.

Because when a high % of the population is protects through vaccination against a virus or bacterium, this makes it difficult for a disease to spread because there are so few susceptible people left to infect and fewer people to do the infecting.

65
Q

Why is here immunity particularly important?

A

It’s important for vulnerable people who cannot be vaccinated. Eg

  • children who are too young to be vaccinated
  • people with immune system problems
  • those who are too ill to receive vaccines (eg cancer patients)
66
Q

What can herd immunity lead to?

A

The eradication of some diseases. Eg like the eradication of smallpox.

67
Q

Structure of a virus?

A
  • 50x smaller than bacteria
  • acellular
  • they only replicate when inside a living cell
  • around the genetic material (of DNA or RNA) is a capsid (which is a protein coat like Lady Gaga’s meat dress)
  • the capsid is made up of capsomeres
68
Q

Structure of HIV?

A
  • protein coat (capsid)
  • attachment protein
  • 2 strands of RNA
  • spherical envelope of lipid bilayer with glycoproteins
69
Q

How is HIV spread?

A

HIV spreads from an infected person to a non infected person when bodily fluids mic. Main ways include sex, or blood transfusion from infected person to non-infected person, people share needles infected mother to her unborn baby through the placenta.

70
Q

How does HIV cause disease?

A
  1. HIV attaches to the surface of a helper T cell.
  2. Reverse transcriptase enzyme from the virus makes a DNA copy of the virus DNA.
  3. The virus DNA is inserted into the DNA of the helper T cell. The virus DNA stays inactive for years.
  4. Then, the virus DNA becomes active and the helper T cells make more viruses.
  5. New viruses are released from the cell. They infect new helper T cells.
  6. Gradually the virus destroys helper T cells.
71
Q

HIV eventually causes a shortage of helper T cells. Why is this bad?

A

Because with a shortage of helper T cells, B cells are not activated and no antibodies are produced - this is AIDS.

72
Q

Why are antibiotics not effective against viruses?

A

Because viruses are not living.

Viruses are not cells, so neither have a cell structure nor their own metabolism, and thus antibiotics cannot affect them.

73
Q

HIV can only infect helper T cells. Explain why.

A

Because helper T cells have receptor proteins on the cell surface membranes that the proteins in the surface of HIV can fit into.

74
Q

Without their helper T cells, AIDS sufferers lose their ability to overcome infections. Why?

A

Because helper T cells are needed to stimulate antibody production by B cells. Without helper T cells, the person’s ability to produce antibodies against infections is dramatically reduced.

75
Q

Drug users who share needles are at increased risk of becoming HIV positive. Explain why.

A

Because used needles will have traces of blood in them. If a person who used the needle is infected with HIV, the virus will be present in this blood.
The viruses will then be injected into the blood of the next person who uses the needle.

76
Q

How do antibiotics work?

A

Antibiotics kill bacteria by interfering with their metabolic reactions.
They target the bacterial enzymes and ribosomes used in these reactions.

77
Q

What are monoclonal antibodies?

A

Antibodies produced from a plasma cells. This means they’re all identical in structure.

78
Q

How are monoclonal antibodies used to target cancer cells?

A
  1. Different cells have different surface antigens.
  2. Cancer cells have antigens called tumour markers that are not found on normal body cells.
  3. Monoclonal antibodies can be made that will bind to the tumour markers.
  4. When these monoclonal antibodies come into contact with the cancer cells, they will bind to the tumour marker
  5. This means the drug will only accumulate in the body where there are cancer cells.
  6. So the side effects of an antibody based drug are lower than other drugs because they accumulate near specific cells.
79
Q

What is active immunity?

A

When the immune system responds to an antigen by producing specific antibodies against the antigen, and memory B cells in a primary immune response to the antigen.

This is what happens when a person is exposed to an infectious disease, or given a vaccination.

80
Q

What is passive immunity?

A

When a person is given antibodies. However this has no lasting effect because the individual has not had an immune response itself, so memory cells have not been made.

For example babies who are breast fed. The baby recieves antibodies that the mother has made, which protects them against any infection that the mother has been exposed to.

1B (35 decks)

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