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A2 Biology Module 1 - Physiology, Coordination and Control, and Ecosystems > Chapter 2 - Immunity > Flashcards

Chapter 2 - Immunity Flashcards

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1
Q

Give an example of some microorganisms which are harmless or even beneficial

A

The many types of bacteria and fungi involved in decay and decomposition which are essential for life on Earth.

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2
Q

Most microorganisms are …

A

Harmless or even beneficial

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3
Q

Most microorganisms are harmless or even beneficial (for example, the many types of bacteria and fungi involved in decay and decomposition are essential for life on Earth). However, …

A

A small percentage of microorganisms, including some bacteria, fungi, protoctists and viruses (although technically viruses are not classified as living organisms) can cause disease or be pathogenic.

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4
Q

Name some microorganisms which can cause disease or be pathogenic

A

Bacteria
Fungi
Protoctists
Viruses

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5
Q

What could happen if a pathogen gains entry to the body?

A

It could cause significant harm or even death

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6
Q

What is the body’s first line of defence against pathogens?

A

The body’s first line of defence against pathogens is to try to prevent entry

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7
Q

If pathogens enter the body, the subsequent defence mechanisms can be grouped into how many types?

A

Two types

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8
Q

If pathogens do enter the body, the subsequent defence mechanisms can be grouped into two types:

A
  • Non-specific

* Specific immune response

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9
Q

What are the non-specific defence mechanisms?

A

These defence mechanisms are not specific to individual types of pathogens.

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10
Q

Give an example of a non-specific defence mechanism

A

Phagocytosis

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11
Q

What are the specific immune response defence mechanisms?

A
  • This type of response does distinguish between individual pathogens and the response is tailored to the pathogen involved.
  • Specific immune responses take longer to work but tend to provide long term immunity.
  • Specific immune responses involve lymphocytes, a specialised type of white blood cell.
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12
Q

Name some of the natural barriers to pathogen entry

A
  1. An outer protective covering (skin)
  2. The enzyme lysozyme
  3. Epithelial linings covered in mucus
  4. Hydrochloric acid in the stomach
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13
Q

Describe how skin, the outer protective covering of the body, is a natural barrier preventing the entry of pathogens

A
  • The skin provides a tough physical barrier that most pathogens cannot penetrate.
  • The skin only ceases to be an effective barrier to most pathogens if it is punctured, for example, a wound or cut, or if it is not in its healthy condition.
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14
Q

Describe how the enzyme lysozyme is a natural barrier preventing the entry of pathogens

A
  • The enzyme lysozyme is contained in many body secretions including tears, saliva and sweat.
  • Lysozyme is anti-bacterial as it is able to digest (hydrolyse) bacteria cell walls.
  • Tears can also wash away debris and pathogens from the front of the eye, which is delicate and easily damaged.
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15
Q

Describe how epithelial linings covered in mucus act as a natural barrier preventing the entry of pathogens

A
  • Epithelial linings covered in mucus, such as in the respiratory tract.
  • The mucus traps pathogens (and other foreign particles) and prevents them penetrating the underlying membranes.
  • Cilia, tiny hairs that line the respiratory tract, sweep the mucus and its trapped pathogens back up the trachea.
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16
Q

Describe how hydrochloric acid in the stomach is a natural barrier preventing the entry of pathogens

A
  • This kills most pathogens that are in the food we eat or the liquids we drink.
  • It is effective as it provides a very low pH that denatures the enzymes of the pathogens.
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17
Q

The body’s first line of defence against pathogens is to try to prevent entry. However, despite barriers to pathogen entry, many do invade our body. What is the next line of defence?

A

Phagocytosis

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18
Q

What is one of the advantages of phagocytosis?

A

Phagocytosis is non-specific but has the advantage of being rapid.

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19
Q

What type of cells carry out phagocytosis?

A

Phagocytosis is carried out by a number of types of white blood cell, collectively known as phagocytes.

Polymorphs, also known as microphages, are the most common and first to arrive at the site of infection.
Phagocytic macrophages, which develop from monocytes in the blood, are larger but much longer lived than polymorphs.

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20
Q

What does the body do in response to infection by a pathogenic microorganism?

A
  • As part of an inflammatory response following infection, the capillaries in the area affected become leaky, allowing plasma to seep into the surrounding areas.
  • Inflamed parts of the body tend to become swollen with phagocytes, dead pathogens and cell debris, collectively known as pus.
  • Inflamed areas appear red due to the increased blood flow to that area.
  • Inflammation also involves the affected part of the body becomes hot (as well as swollen). The raised temperature helps reduce infection by denaturing enzymes in the pathogen.
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21
Q

Outline the process of phagocytosis

A
  1. Phagocytes are able to squeeze through capillary walls to reach the site of infection.
  2. The phagocyte moves towards the pathogen, attracted by the chemicals it produces.
  3. As it does so the phagocyte membrane invaginates to begin to enclose the pathogen.
  4. As the pathogen is engulfed, the invaginated phagocyte membrane forms a vesicle (phagosome) around the pathogen.
  5. Lysosomes move towards the phagosome and fuse with it.
  6. Hydrolytic enzymes within the lysosome are released into the phagosome, onto the pathogen.
  7. The enzymes hydrolyse the pathogen.
  8. The soluble digested products are absorbed into the cytoplasm of the phagocyte.
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22
Q

What do phagocytes engulf?

A

Pathogenic microorganisms and surrounding cell debris at sites of infection.

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23
Q

Specific immune responses are associated with what type of cell?

A

Lymphocyte white blood cells

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24
Q

What triggers the specific immune response?

A

The response is triggered by the body’s ability to recognise ‘foreign’ cells, linked to the concept of self and non-self tissue.

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25
Q

What are foreign (non-self) cells?

A

Cells not recognised by the body

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26
Q

What will happen if foreign (non-self) cells are detected in the body?

A

They will produce and immune response.

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27
Q

What part of the non-self cell is recognised as foreign by the body’s immune system?

A

Specific molecules, or clusters of molecules, that form part of the cell surface membrane of the foreign cell.

These molecules are often protein, but can be other substances, for example, polysaccharides, glycoprotein and glycolipid, and are collectively referred to as antigens.

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28
Q

Different pathogens have …

A

Different antigens

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29
Q

Different pathogens have different antigens, consequently …

A

The immune response is specific to these antigens.

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30
Q

Draw a diagram showing the process of phagocytosis

A

Textbook page 22

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31
Q

Different pathogens have different antigens, consequently the immune response is specific to these antigens. How does the immune system bring this specific response about?

A
  • This specific response is due to the lymphocyte having a receptor on its cell surface membrane that is complementary in shape to the antigen.
  • Antigen and lymphocyte fit together like substrate and enzyme in the lock and key model of enzyme action.
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32
Q

What is an antigen?

A

A chemical capable of producing a specific immune response.

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33
Q

How do lymphocytes know what is self and non-self?

A
  • There are many million different types of lymphocytes, each having receptors with a complementary shape to a potential antigen.
  • In the foetus, these lymphocytes frequently make contact with other foetal (self) cells.
  • Lymphocytes that are complementary in shape with foetal cells are ‘switched off’ so by the time the baby is born the functional lymphocytes that remain are those that are not complementary to self cells.
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34
Q

Give one reason why the specific immune response is relatively slow

A

There are many million functional lymphocytes within the body, but there are only a few of each type that are specific to the invading pathogens antigens.

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35
Q

How many types of lymphocyte are there?

A

Two

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36
Q

What are the two types of lymphocyte?

A

B-lymphocytes (B-cells)

T-lymphocytes (T-cells)

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37
Q

Where are B-lymphocytes formed?

A

Formed from stem cells in the bone marrow

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38
Q

Where are T-lymphocytes formed?

A

Formed from stem cells in the bone marrow

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39
Q

Where is the site of development (maturation) for B-lymphocytes?

A

Mature in bone marrow

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40
Q

Where is the site of development (maturation) for T-lymphocytes?

A

Mature in thymus gland

lymph gland in the neck

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41
Q

What is the name of the immune response associated with B-lymphocytes?

A

Antibody-mediated (humoral) immunity

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42
Q

What is the name of the immune response associated with T-lymphocytes?

A

Cell-mediated immunity

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43
Q

What is the nature of the immune response associated with B-lymphocytes?

A
  • Produce antibodies which respond to antigens found in body fluids (for example, blood and tissue fluid).
  • Respond usually to bacterial or viral infection.
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44
Q

What is the nature of the immune response associated with T-lymphocytes?

A
  • Respond to antigens attached to body cells.

* Respond usually to body cells affected by viral infection.

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45
Q

Once infection occurs, how is the specific immune response activated?

A
  • An antigen will come into contact with its complementary lymphocyte - a process that may take some time due to the small numbers involved.
  • When this happens the lymphocytes become sensitised or activated.
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46
Q

Give a similarity and difference between the processes of cell- mediated and antibody-mediated immunity

A

Similarity
• In both B and T-cells, sensitised lymphocytes are cloned (involving division by mitosis).
Difference
• In B-lymphocytes, certain genes are activated to set in motion a process that eventually leads to the production of antibodies.
• Whereas in T-lymphocytes, a number of types of T-cell are produced, each type having different roles in the battle against infection.

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47
Q

In an immune response, what stimulates the production of T-cells?

A

The production of T-cells is stimulated by the body’s own cells that have been changed due to the presence of non-self material within them.

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48
Q

What are antigen-presenting cells?

A

Body cells that have been changed due to the presence of non-self material within them.

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49
Q

Cell-mediated immunity

In an immune response, the production of T-cells is stimulated by the body’s own cells that have been changed due to the presence of non-self material within them. These cells are then referred to as …

A

Antigen-presenting cells

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50
Q

Give some examples of antigen-presenting cells

A
  1. Macrophages (phagocytes) that have engulfed and broken down a pathogen and ‘present’ some of the pathogen’s antigens on their own cell surface membrane.
  2. Any type of body cell that has been invaded by a virus - again some of the viral antigens are presented on the cell surface membrane of the body cell (remember, viruses cannot live on their own, they must live inside other cells).
  3. Cancer (tumour) cells, as many cancer cells present abnormal antigens on their cell surface membranes.
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51
Q

Draw a diagram showing the series of events in which an antigen-presenting cell brings about a cell-mediated immune response

A

Textbook page 24

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52
Q

Cloned T-cells produced during cell-mediated immunity can develop into how many different cell types?

A

Four

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53
Q

Cloned T-cells produced during cell-mediated immunity can develop into what different cell types?

A
  1. Killer (cytotoxic) T-cells
  2. Helper T-cells
  3. Suppressor T-cells (also known as regulatory T-cells)
  4. Memory T-cells
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54
Q

What are killer T-cells?

A

• Killer (cytotoxic) T-cells destroy infected cells by attaching to the antigens on the cell surface membrane of the infected or abnormal cell and destroying it by direct enzyme action.

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55
Q

What are helper T-cells?

A
  • These cells stimulate other cells involved in the immune response, for example, they stimulate B-cells to divide (and produce the plasma cells that produce antibodies) and promote the process of phagocytosis through their effect on phagocytes.
  • Phagocytosis is a slow process without the activating role of the helper T-cells.
  • They also attach special chemicals (opsonins) to the pathogens that mark them out for the attention of phagocytes.
  • Helper T-cells also secrete the protein interferon that helps limit the ability of viruses to replicate.
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56
Q

What are suppressor T-cells?

A
  • These cells ‘suppress’ the immune response of other immune cells when required.
  • Suppressor T-cells switch off the immune response after invading microbes and infected cells have been destroyed.
  • They are also important in preventing autoimmune responses, the situation where the immune system attacks ‘self’ cells in the body.

Note: Suppressor T-cells deactivate the immune response of both B and T-cells.

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57
Q

What are memory T-cells?

A
  • These cells circulate in body fluids and can respond rapidly to future infection by the same pathogen (presenting the same antigen(s)).
  • If a subsequent infection occurs, as the memory cells are already sensitised, they can very rapidly produce a large clone of T-lymphocytes.
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58
Q

What causes Type 1 diabetes?

A

It is thought that the onset of Type 1 diabetes, an autoimmune condition, is linked to reduced numbers of a type of suppressor T-cell, resulting in a cell-mediated attack on the insulin-producing cells in the pancreas.

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59
Q

What does the antibody-mediated immune response target?

A

Microorganisms (usually bacteria or viruses) that are found in the body fluids (for example, blood and tissue fluid), rather than in body cells.

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60
Q

How does antibody-mediated immunity defend the body?

A

Through the production and action of antibodies

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61
Q

What are antibodies?

A

Antibodies can be defined as globular proteins which are complementary to specific antigens and which can react with the antigens (microbes) leading to their destruction.

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62
Q

Draw a diagram showing the series of events in which an invading pathogen found in the body fluids triggers an antibody-mediated immune response

A

Textbook page 25

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63
Q

Describe the series of events in which an invading pathogen found in the body fluids triggers an antibody-mediated immune response

A
  • Pathogen is present in the body fluids.
  • B-lymphocyte that has a receptor with the exact complementary fit to the bacterial antigen is sensitised
  • A sensitised (activated) B-lymphocyte divides rapidly by mitosis to form a clone. The cloned cells develop into plasma cells and memory cells.
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64
Q

Specific antigens sensitise …

A

Specific B-lymphocytes

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65
Q

Specific antigens sensitise specific B-lymphocytes that …

A

Have receptors that match the pathogen’s antigens.

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66
Q

Specific antigens sensitise specific B-lymphocytes that have receptors that match the pathogens antigens. Therefore, following infection by a particular pathogen, …

A

A particular type (or types) of B-lymphocyte becomes cloned.

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67
Q

In common with sensitised T-cells, sensitised B-cells produce …

A

Different types of cell, in the case of B-cells, plasma cells and memory cells.

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68
Q

Most cloned B-cells become what type of cell?

A

Plasma cells

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69
Q

What are plasma cells?

A

Plasma cells are short lived (a few days) but each produces very large numbers (many millions) of antibodies.

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70
Q

How do antibodies neutralise pathogens?

A

The antibodies neutralise the pathogens as a consequence of antigen-antibody reactions.

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71
Q

Antibodies will be produced as a consequence of what?

A

As a consequence of a specific antibody-mediated immune response

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72
Q

The antibodies produced as a consequence of a specific antibody-mediated immune response will be what in relation to the invading pathogen’s antigens?

A

Complementary in shape.

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73
Q

How do antibodies form an antigen-antibody complex?

A
  • The antibodies latch on to the bacterial antigens clumping the bacteria together.
  • Typically, the build up of antibodies in the body fluids will enable a sufficient number to be present to immobilise the bacteria causing their agglutination or clumping as an antigen-antibody complex.
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74
Q

What will happen to the antigen-antibody complex?

A

In due course the antigen-antibody complex (clump of bacteria and antibodies) is engulfed by polymorphs and other phagocytes.

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75
Q

Draw a diagram showing the series of events leading to the formation of an antigen-antibody complex

A

Textbook page 26

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76
Q

What are some of the methods by which antibodies can defend against disease?

A
  1. Agglutination.
  2. Destruction of the invading cells directly via antigen-antibody reactions.
  3. Antibodies can also act as opsonins by attaching to pathogens and marking them for phagocytosis.
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77
Q

What are antibodies?

A

Antibodies are globular proteins that are complementary in shape to a specific antigen.

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78
Q

Which molecule is ideal for the composition of antibodies?

A

Protein

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79
Q

Why is protein the ideal molecule for the composition of antibodies?

A

As small changes in the sequence of amino acids in the primary structure can produce the millions of different three-dimensional shapes required to be complementary in shape to the range of antigens that exist.

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80
Q

The receptor on the sensitised B-lymphocyte and the part of the antibody that attaches to the antigen are …

A

Exactly the same shape (and both are complementary in shape to the antigens on the invading pathogen).

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81
Q

For how long do memory cells, produced by B-cells, live?

A

For many years (sometimes for life) in the body fluids.

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82
Q

Outline the series of events leading to the secondary immune response

A
  • Memory cells produced by B-cells can live for many years (sometimes for life) in the body fluids.
  • These cells remain inactive unless stimulated by the presence of the same antigen (pathogen) again.
  • If this happens, the memory cells divide rapidly (they are already sensitised) and produce vast numbers of plasma cells, as there are more memory cells than there were ‘correct’ B-cells at the start of the primary response.
  • The plasma cells produce the antibodies necessary to destroy the pathogen while the memory cells provide a guarantee of further long term protection.
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83
Q

What is the primary immune response?

A

The initial response of the body to the antigen when meeting it for the first time.

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84
Q

The memory cells produced by B-cells can live for many years (sometimes for life) in the body fluids. These cells remain inactive unless stimulated by the presence of the same antigen (pathogen) again. If this happens, the memory cells divide rapidly (they are already sensitised) and produce vast numbers of plasma cells as there are more memory cells than there were ‘correct’ B-cells at the start of the primary response. The plasma cells produce the antibodies necessary to destroy the pathogen while the memory cells provide a guarantee of further long term protection. This is known as …

A

The secondary immune response

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85
Q

What is the secondary immune response?

A

The secondary response of the body to the antigen when meeting it for the second time, involving memory cells.

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86
Q

Pathogens can contain …

A

Many different types of antigen

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87
Q

Pathogens can contain many different types of antigen. Each antigen can …

A

Produce an immune response with a different type of B-lymphocyte.

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88
Q

Pathogens can contain many different types of antigen. Each antigen can produce an immune response with a different type of B-lymphocyte. Therefore, …

A

For any one type of pathogen there may be many different antigen-antibody reactions taking place at the same time.

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89
Q

Are some individuals immune to all potential pathogens and diseases?

A

No one individual is immune to all potential pathogens and diseases. However, individuals can be immune to (protected against) specific diseases.

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90
Q

What are the two general types of immunity?

A

Active

Passive

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91
Q

What is passive immunity?

A

Passive immunity is when the individual receives antibodies from another source (ie from outside the body).

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92
Q

What is active immunity?

A

Active immunity is when the individual achieves immunity through the production of antibodies by his/her own body.

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93
Q

What are some of the methods by which passive immunity can develop?

A
  1. Antibodies passing from mother to baby across the placenta and in the mother’s milk (colostrum).
    - The passive immunity that this produces is crucial in the very early stages of life, a time when the baby’s immune system is still developing.
  2. Antibodies made in another individual, which are harvested and injected into another person as serum.
    - The antibodies can be obtained from individuals recovering from illness (they will have high levels of the required antibody in their blood).
    - An older method of obtaining antibodies involved immunising animals, for example horses, with attenuated pathogens or their inactivated toxins.
    - This causes the animal to produce the antibodies required and serum from the animals was given to individuals requiring rapid immunity.
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94
Q

What is serum?

A

Blood plasma with all blood clotting substances removed.

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95
Q

Antibodies can pass from mother to baby across the placenta and in the mother’s milk (colostrum). Why is the passive immunity that this produces crucial in the very early stages of life?

A

As this is during a time when the baby’s immune system is still developing.

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96
Q

A person who requires rapid immunity can receive antibodies from another source via an injection. How can these antibodies be obtained?

A
  1. From individuals recovering from illness (they will have high levels of the required antibody in their blood).
  2. An older method of obtaining antibodies involves immunising animals (for example, horses) with attenuated pathogens or their inactivated toxins. This caused the animal to produce the antibodies required and serum from the animals was given to individuals requiring rapid immunity.
  3. Monoclonal antibody production.
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97
Q

Passive immunity - can develop by a number of methods. These include:

  • Antibodies passing from mother to baby across the placenta and in the mother’s milk (colostrum). The passive immunity that this produces is crucial in the very early stages of life, a time when the baby’s immune system is still developing.
  • Antibodies made in another individual, which are harvested and injected into another person as serum. The antibodies can be obtained from individuals recovering from illness (they will have high levels of the required antibody in their blood). An older method of obtaining antibodies involved immunising animals, for example horses, with attenuated pathogens or their inactivated toxins. This caused the animal to produce the antibodies required and serum from the animals was given to individuals requiring rapid immunity.

The methods of obtaining antibodies for medical use from other live sources (described above) are now largely superseded by …

A

Monoclonal antibody production

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98
Q

What is the main method of obtaining antibodies for medical use?

A

Monoclonal antibody production

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99
Q

Outline the process of monoclonal antibody production

A
  1. Specific antigen (not a microbe) is injected into a mouse.
  2. Sensitised and cloned B-lymphocytes are removed from the mouse that has been infected with the particular antigen.
  3. The short lived mouse B-lymphocytes are hybridised with laboratory cultured tumour (cancer) cells (which are rapidly dividing and long lived ie immortal).
  4. The two cell types are fused together, combining the properties of each to produce long lived hybridoma (hybrid) cells that are cultured in optimum conditions (ie in a fermenter over a long period of time) to maximise monoclonal antibody production.
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100
Q

Draw a diagram showing the series of events leading to the production of monoclonal antibodies

A

Textbook page 27

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101
Q

What are the advantages of monoclonal antibodies?

A

Monoclonal antibodies have many advantages compared to obtaining antibodies from horses or other large mammals:

  • Can be produced in large quantities in the laboratory.
  • Can produce a single type of antibody (antibodies obtained from horses usually come as a range of types, together with other chemicals that can potentially cause allergies).
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102
Q

What are the advantages of passive immunity?

A
  • Passive immunity provides rapid immunity as the processes of B-lymphocyte sensitisation and plasma cell production do not need to take place first.
  • It is especially effective if someone becomes infected with a particularly harmful pathogen when it is probable that they have no defence against it (for example, a ‘new’ disease encountered in a foreign country or when suffering from a snake bite).
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103
Q

What are the disadvantages of passive immunity?

A

Passive immunity is only temporary, as in time the antibodies are broken down and the individual’s immune system is not programmed to make more.

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104
Q

Draw a graph showing the changes in concentration of antibodies during passive immunity.

A

Textbook page 28

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105
Q

How can active immunity develop in an individual?

A

From having had the disease, or via vaccinations.

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106
Q

Outline the key events which occur when:

  • an individual becomes infected with a pathogen for the first time
  • an individual re-encounters the same pathogen later on in life
A
  • The individual becomes ill but recovers as a consequence of the primary response to the infection.
  • The primary immune response is slow to develop and the individual usual suffers the disease symptoms for a period of time (it may take 4-5 days before antibody levels reach a high enough level to be effective in a primary response, due to the time involved in activating the specific B-lymphocytes and producing plasma cells) but once in place it is long lasting.
  • Should a subsequent infection occur, involving the same pathogen, the secondary response is so rapid and strong that the immune system may destroy the pathogen(s) so quickly that the individuals may not even be aware that they were infected.
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107
Q

Why is the secondary immune response strong and rapid compared with the primary immune response?

A

There are many more memory cells than there were specific B-lymphocyte cells at the start of the primary response (strength) and the memory cells are already sensitised (speed).

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108
Q

Why is active immunity long lasting?

A

Although some antibodies can last in the blood for a considerable length of time, the fact that active immunity is long lasting is primarily due to the presence of memory cells and their ability to respond quickly and effectively if a subsequent infection occurs.

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109
Q

Vaccinations also produce …

A

Active immunity

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110
Q

Vaccinations also produce active immunity. In the UK, vaccination programmes are in place for …

A

Many diseases

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111
Q

Give some examples of diseases which have vaccination programmes in the UK

A

Measles and mumps

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112
Q

When are most vaccinations given?

A

Early in childhood.

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113
Q

What is the function of vaccines?

A

To stop individuals being affected by potentially common and harmful infectious diseases.

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114
Q

Vaccinations trick the immune system into thinking …

A

The body has been infected by a particular pathogen

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115
Q

Vaccinations trick the immune system into thinking the body has been infected by a particular antigen; consequently …

A

The primary immune response is triggered and the immune system is equipped to produce a secondary response if required.

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116
Q

Vaccinations trick the immune system into thinking the body has been infected by a particular antigen; consequently the primary immune response is triggered and the immune system is equipped to produce a secondary response if required. Due to the speed and strength of the secondary response, vaccinations render the individual …

A

Immune

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117
Q

Vaccinations trick the immune system into thinking the body has been infected by a particular antigen; consequently the primary immune response is triggered and the immune system is equipped to produce a secondary response if required.

How does the vaccination render the individual immune?

A

The speed and strength of the secondary response renders the individual immune.

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118
Q

What do vaccinations contain?

A

Vaccinations normally contain one of the following:

  1. Killed or weakened (attenuated) pathogens
    - These pathogens contain the antigens required to produce an immune response but they will not cause the disease itself (however, mild symptoms may sometimes appear).
  2. Modified toxins produced by the pathogen
    - With some pathogens it is their toxins that can produce the immune response.
    - The toxins must be modified and made harmless but not changed so much they do not produce an immune response.
  3. Isolated antigens separated from the pathogen itself
    - For some pathogens the antigens can be made by genetic engineering.
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119
Q

What do some vaccinations required?

A

Subsequent booster injections

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120
Q

What are booster injections?

A

These produce a secondary immune response, similar to the response produced when catching a particular disease for a second time.

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121
Q

Draw an annotated graph showing the characteristic changes in the concentration of antibodies during active immunity

A

Textbook page 29

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122
Q

Immunity provided by cell-mediated immunity is also …

A

Active immunity

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123
Q

What is the main benefit of vaccination?

A

There are fewer sick people and the lives of many people are extended, often considerably.

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124
Q

Why has the world child mortality rate halved in the last 25 years?

A

Largely due to the increasing availability of vaccination programmes.

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125
Q

How does society benefit from vaccination programmes?

A
  1. Fewer people are ill.
  2. Less care is needed to tend the ill.
  3. Healthy children tend, on average, to do better at school.
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126
Q

Setting up vaccination programmes is …

A

Expensive

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127
Q

While setting up vaccination programmes is expensive, …

A

The overall benefit to a nation’s economy is much greater.

128
Q

What are the economic benefits of vaccination programmes?

A
  1. There are lower treatment costs to treat those who are ill.
  2. Employees do not have to take time off work, therefore productivity increases.
  3. Carers, for example parents, do not have to take time off work to care for the sick.
129
Q

The vaccination programmes in large developed countries save …

A

Billions of pounds annually

130
Q

The vaccination programmes in large developed countries save billions of pounds annually through …

A

Reducing illness from infectious disease.

131
Q

The concept of ____ ________ is important in vaccination programmes

A

Herd immunity

132
Q

What is the concept of herd immunity?

A

If a high enough proportion of the population is vaccinated, those who are not vaccinated are less likely to catch a particular infectious disease (as they are less likely to come into contact with someone who is infectious).

133
Q

Why is herd immunity important?

A
  • Herd immunity is very important in protecting those who cannot get vaccinated, for example newborns (first NHS immunisation is currently at six weeks) and the very ill.
  • Of course, it also helps protect the small numbers who, against medical advice, choose not to get vaccinated.
134
Q

What are the two general types of immunity?

A

Active

Passive

135
Q

What are the two general types of active immunity?

A

Natural

Acquired (artificial)

136
Q

What are the two general types of passive immunity?

A

Natural (innate)

Acquired (artificial)

137
Q

What is natural active immunity?

A

Immunity developed through having had the disease

138
Q

What is acquired (artificial) active immunity?

A

Acquired via vaccination

139
Q

What is natural (innate) passive immunity?

A

Immunity from mother via placenta or milk (colostrum)

140
Q

What is acquired (artificial) passive immunity?

A

Immunity via an injection of antibodies

141
Q

Draw a flow diagram summarising the different types of immunity

A

Textbook page 30

142
Q

When will the body produce an immune response?

A

When it detects the presence of any non-self antigens.

143
Q

The body will produce an immune response to the presence of any non-self antigens. Normally this response occurs as a consequence of …

A

Infection

144
Q

The body will produce an immune response to the presence of any non-self antigens. Normally this response occurs as a consequence of infection. In what scenario can this response also occur?

A

Transplanted organs (such as kidneys) or tissue (such as skin grafts) will also produce an immune response.

145
Q

The body will produce an immune response to the presence of any non-self antigens. Normally this response occurs as a consequence of infection. However, transplanted organs (such as kidneys) or tissue (such as skin grafts) will also produce and immune response. Why is this?

A

As the transplanted organ/tissue will contain non-self antigens if they come from someone else.

146
Q

The body will produce an immune response to the presence of any non-self antigens. Normally this response occurs as a consequence of infection. However, transplanted organs (such as kidneys) or tissue (such as skin grafts) will also produce and immune response, as the transplanted organs/tissue will contain non-self antigens if they come from someone else. Exceptions are if …

A
  • The tissue is transplanted within the same person (as can happen with skin grafts)

OR

  • If tissues/organs are transplanted between identical twins (identical twins are genetically identical and therefore they have identical antigens).
147
Q

Most organ transplants …

A

Do not take place between identical twins

148
Q

What chemical do killer T-cells produce to destroy non-self cells?

A

A protein called perforin

149
Q

Most organ transplants do not take place between identical twins, therefore …

A

The risk of transplant rejection exists.

150
Q

What is the main reason for many organ transplants failing?

A

Transplant rejection

151
Q

Describe the steps involved in transplant rejection

A
  1. T-lymphocytes are stimulated (sensitised) by the non-self antigens present in the transplanted tissue.
  2. These T-cells are cloned by mitosis to produce killer T-cells (and the range of other T-cells associated with cell-mediated immunity).
  3. The killer T-cells destroy the transplanted cells.
152
Q

The process of rejection involves the following steps:

  1. T-lymphocytes are stimulated (sensitised) by the non-self antigens present in the transplanted tissue.
  2. These T-cells are cloned by mitosis to produce killer T-cells (and the range of other T-cells associated with cell-mediated immunity).
  3. The killer T-cells destroy the transplanted cells.

Transplant rejection can also involve the action of …

A

B-lymphocytes and antibodies

153
Q

The process of rejection involves the following steps:

  1. T-lymphocytes are stimulated (sensitised) by the non-self antigens present in the transplanted tissue.
  2. These T-cells are cloned by mitosis to produce killer T-cells (and the range of other T-cells associated with cell-mediated immunity).
  3. The killer T-cells destroy the transplanted cells.

Transplant rejection can also involve the action of B-lymphocytes and antibodies. In what scenario might this occur?

A

If the blood of a donor and a recipient is different, this can produce an immune response involving antibodies.

154
Q

The process of rejection involves the following steps:

  1. T-lymphocytes are stimulated (sensitised) by the non-self antigens present in the transplanted tissue.
  2. These T-cells are cloned by mitosis to produce killer T-cells (and the range of other T-cells associated with cell-mediated immunity).
  3. The killer T-cells destroy the transplanted cells.

Transplant rejection can also involve the action of B-lymphocytes and antibodies. For example, if the blood of a donor and a recipient is different, this can produce an immune response involving antibodies. Why does this normally not occur?

A

As normally tissue matching is accurate so rejection by B-lymphocytes in this situation is unlikely to occur.

155
Q

Why has considerable scientific endeavour gone into devising strategies for reducing transplant rejection?

A

As organ transplants may be a last resort in saving a life or even in providing a better quality of life for a patient.

156
Q

As organ transplants may be a last resort in saving a life or even providing a better quality of life for a patient, considerable scientific endeavour has gone into …

A

Devising strategies for reducing transplant rejection.

157
Q

What are some of the strategies used to reduce the chances of transplant rejection?

A
  1. Tissue typing
  2. Immunosuppression techniques
  3. X-rays
158
Q

Describe how tissue typing is a strategy used to reduce transplant rejection

A
  • This is the term that describes the process of matching the donor and recipient cell surface markers (antigens) so that there is as good a match as possible, ie there is as small a difference as possible between the self and non-self antigens.
  • Generally, the best tissue matching will take place between close relatives.
  • The best possible transplant will be between identical twins, who will have identical antigens therefore the transplant is much less likely to be rejected.
159
Q

Describe now immunosuppression techniques are a strategy used to reduce transplant rejection

A
  • Immunosuppression techniques such as the use of drugs to inhibit DNA replication and therefore the cloning of lymphocytes (and the production of killer T-cells) will slow down or stop rejection processes.
  • For many types of transplant, the immunosuppression drugs have to be taken for a very long time (for the life of the transplant and therefore often for life).
160
Q

Describe how the use of X-rays is a strategy used to reduce transplant rejection

A
  • Can be used to inhibit the production of lymphocytes through the irradiation of bone marrow or lymph tissue.
  • Unpleasant side effects can result and the use of X-rays is usually a backup to immunosuppressant drugs rather than a first course of action.
161
Q

What is the major disadvantage of the use of immunosuppression techniques and X-rays in reducing transplant rejection?

A

Immunosuppression (whether by drugs or X-rays) will compromise the recipient’s immune system.

162
Q

Immunosuppression (whether by drugs or X-rays) will compromise the recipient’s immune system. What does this mean for the individual?

A

This makes the individual susceptible to infection.

163
Q

Immunosuppression (whether by drugs or X-rays) will compromise the recipient’s immune system. Why will this make the individual susceptible to infection?

A

As immunosuppression depresses the immune system in general (not just its response to the antigens involved in the transplanted tissue).

164
Q

What are some of the additional strategies used to help support the transplant patient against subsequent infections?

A
  • Anti-viral drugs
  • Anti-bacterial mouth rinses
  • Anti-T-cell monoclonal antibodies to help target and reduce the effect of the T-cells involved in rejection.
165
Q

Immunosuppression (whether by drugs or X-rays) will compromise the recipient’s immune system. This makes the individual susceptible to infection, as immunosuppression depresses the immune system in general (not just its response to the antigens involved in the transplanted tissue). A number of additional strategies are used to help support the transplant patient against subsequent infections including anti-viral drugs, anti-bacterial mouth rinses and the use of monoclonal antibodies to help target and reduce the effect of the T-cells involved in rejection.

Nonetheless, there is …

A

A delicate balance between reducing the risks of rejection and restricting the side effects that are linked to the use of immunosuppressant technologies.

166
Q

Draw an annotated diagram illustrating the delicate balancing act between risk of transplant rejection and use of immunosuppressant agents

A

Textbook page 31

167
Q

With blood transfusions, it is important to remember that …

A

Red blood cells also have antigens (markers) on their cell surface membrane just like other body cells.

168
Q

Red blood cells also have antigens (markers) on their cell surface membranes just like other body cells. From this information what can be determined about the blood of any one individual?

A

The blood of any one individual will not have antibodies that correspond to the antigens on his/her red blood cells as this would trigger an immune reaction.

169
Q
  • Blood transfusion
    Red blood cells also have antigens (markers) on their cell surface membrane. The blood of any one individual will not have antibodies that correspond to the antigens on his/her red blood cells as this would trigger an immune reaction. As with other B-lymphocytes that correspond with self-antigens, the lymphocytes responsible for these blood antibodies are …
A

Switched off during very early development

170
Q

The type of antigens on the red blood cells of different people …

A

Varies

171
Q

Give an example of a blood group system

A

The ABO system

172
Q

How many different types of blood group are there in the ABO system?

A

Four

A
B
AB
O

173
Q

However, the type of antigens on the red blood cells of different people varies. In the ABO system, there are four different types of blood group (A, B, AB and O) and everyone …

A

Belongs to one of these groups.

174
Q

However, the type of antigens on the red blood cells of different people varies. In the ABO system, there are four different types of blood group (A, B, AB and O) and everyone belongs to one of these groups. This is an example of …

A

Polymorphism

175
Q

However, the type of antigens on the red blood cells of different people varies. In the ABO system, there are four different types of blood group (A, B, AB and O) and everyone belongs to one of these groups. This is an example of polymorphism.

What is polymorphism?

A

A situation where there are several distinct categories or forms.

176
Q

When may an individual require a blood transfusion?

A

Following surgery
Following an accident
When treating a specific illness

177
Q

When giving a blood transfusion to an individual it is important that …

A

The transfusion is compatible.

178
Q

Why can blood be donated from an individual with blood group A (the donor) to another individual with blood group A (the recipient)?

A

Because the recipient has no anti-a antibodies that correspond to the antigens on the donor’s red blood cells.

179
Q

Can blood be donated from an individual with blood group A (the donor) to another individual with blood group A (the recipient)?

A

Yes

180
Q

Can blood be donated from a donor with blood group A to a recipient with blood group B?

A

No

181
Q

Blood cannot be donated from a donor with blood group A to a recipient with blood group B. Why?

A
  • Because the recipient has anti-a antibodies in his/her plasma.
  • The presence of both antigen A and anti-a antibodies causes an antigen-antibody reaction.
  • The anti-a antibodies cause the blood, containing red blood cells with antigen A, to agglutinate or clump.
  • This agglutination could block capillary networks and lead to organ failure and death.
182
Q

An individual with blood group B will have what type of antibodies in their blood?

A

Anti-a antibodies

183
Q

Why will an individual with blood group B have anti-a antibodies in their blood?

A

As they had no A antigens in early development; therefore, A antigens were not identified as self antigens and the lymphocytes responsible for producing antibody-a were not ‘switched off’.

184
Q

Draw a table showing the antigens and antibodies of the ABO blood group system

A

Textbook page 32

185
Q

What antigens will an individual with blood group A have on the surface of their red blood cells?

A

Antigen A

186
Q

What antigens will an individual with blood group B have on the surface of their red blood cells?

A

Antigen B

187
Q

What antigens will an individual with blood group AB have on the surface of their red blood cells?

A

Both antigens A and antigens B

188
Q

What antigens will an individual with blood group O have on the surface of their red blood cells?

A

Neither antigens A nor antigens B

189
Q

What antibodies will an individual with blood group A have in their blood plasma?

A

Anti-b antibodies

190
Q

What antibodies will an individual with blood group B have in their blood plasma?

A

Anti-a antibodies

191
Q

What antibodies will an individual with blood group AB have in their blood plasma?

A

Neither anti-a nor anti-b antibodies

192
Q

What antibodies will an individual with blood group O have in their blood plasma?

A

Both anti-a and anti-b antibodies

193
Q

Using a table showing the antigens and antibodies of the ABO blood group system it is possible to work out …

A

Which blood can be transfused into which other type(s).

194
Q

Using a table showing the antigens and antibodies of the ABO blood group system it is possible to work out which blood can be transfused into which other type(s). Donated blood does not have to be the same type a the recipient but it is important that …

A

The donated blood type does not lead to an antigen-antibody reaction and subsequent agglutination.

195
Q

Draw a table showing which blood can be transfused into which other type(s).

A

Textbook page 32

Blood group of donor/ Blood group of recipient

196
Q

As blood group O does not have either A or B antigens, blood of group O can be …

A

Transfused into any of the four blood groups.

197
Q

Why can blood of group O be transfused into any of the four blood groups?

A

As blood of group O does not have either A or B antigens.

198
Q

Blood group O is often referred to as …

A

The universal donor

199
Q

As blood of group O does not have either A or B antigens, blood of group O can be transfused into any of the four blood groups. Consequently, …

A

Blood group O is referred to as the universal donor.

200
Q

As blood of group AB lacks both anti-a and anti-b antibodies, people with blood group AB can …

A

Receive blood from any group.

201
Q

Why can people with blood group AB receive blood from any group?

A

As they lack both anti-a and anti-b antibodies

202
Q

Blood group AB is often referred to as …

A

The universal recipient

203
Q

Blood group AB lacks both anti-a and anti-b antibodies, therefore this is referred to as …

A

The universal recipient

204
Q

What is a key point to remember when working out transfusion compatibility?

A

Donated blood is mainly red blood cells and the amount of donated plasma is insignificant.

205
Q

A key point when working out transfusion compatibility is that donated blood is mainly red blood cells and that the amount of donated plasma is insignificant.
Blood group A can be donated to a recipient with blood group AB. This is only because …

A

None, or a very insignificant number of, anti-b antibodies in blood group A will be transfused into the recipient with blood group AB.

206
Q

Why do we have an ABO system?

A
  • It is thought that the different antigens (groups) evolved as a consequence of mutations.
  • Currently, none of the blood groups appears to give individuals a selective advantage (ie the mutations are neutral).
  • However, it is possible that in our evolutionary past some of the mutations gave selective advantage against specific diseases - this would explain why the different groups have persisted through time.
207
Q

The ABO is only one of …

A

A number of many blood group systems in humans.

208
Q

The ABO is only one of a number of many blood group systems in humans, although it is …

A

The most important in clinical practice.

209
Q

What is the most important blood group system in clinical practice?

A

The ABO system

210
Q

The ABO is only one of a number of many blood group systems in humans, although it is the most important in clinical practice. Another very important blood group system is …

A

The rhesus system

211
Q

What is the rhesus system based on?

A

The presence or absence of an antigen (the rhesus antigen or antigen D) on the cell surface membranes of the red blood cells.

212
Q

What percentage of the population have the rhesus antigen on their red blood cells?

A

Around 85%

213
Q

The rhesus system - This system is based on the presence or absence of an antigen (the rhesus antigen or antigen D) on the cell surface membranes of the red blood cells. Around 85% of the population have this antigen and are described as …

A

Rhesus positive

214
Q

Give the notation for rhesus positive and rhesus negative

A

Textbook page 33

215
Q

The rhesus system - This system is based on the presence or absence of an antigen (the rhesus antigen or antigen D) on the cell surface membranes of the red blood cells. Around 85% of the population have this antigen and are described as rhesus positive. Rhesus negative individuals …

A

Do not have the antigen.

216
Q

Unlike the antibodies for the ABO system, antibodies against the antigen D marker (anti-D antibodies) …

A

Do not occur naturally in the plasma.

217
Q

Why will a rhesus positive individual not produce anti-D antibodies?

A

As relevant B-lymphocytes are ‘switched off’ when the rhesus positive marker is recognised as self during development.

218
Q

Why do anti-D antibodies not normally occur in the plasma of individuals?

A
  • An individual who is rhesus positive will not produce anti-D antibodies (relevant B-lymphocytes are ‘switched off’ when the rhesus positive marker is recognised as self during development).
  • Rhesus negative individuals do not normally have the antibodies either, but can produce anti-D antibodies if their blood becomes contaminated with blood containing antigen D.
219
Q

In what situations can a rhesus negative individual’s blood become contaminated with blood containing antigen D?

A
  1. Blood transfusion between a rhesus positive donor and a rhesus negative recipient. In reality, this is unlikely to occur with modern blood matching techniques.
  2. When a rhesus negative mother has a rhesus positive baby.
220
Q

What is the typical sequence of events when a rhesus negative mother has a rhesus positive baby?

A
  1. During birth (or late in pregnancy) some foetal red blood cells (rhesus positive so contain antigen D) leak into the mother’s circulation.
  2. This causes the rhesus negative mother’s immune system to produce anti-D antibodies. By the time the antibodies are produced in significant numbers by the mother, the baby will have been born therefore there is no threat to the developing foetus.
  3. However, during subsequent pregnancies, if the foetus is rhesus positive, the relevant B-lymphocytes in the mother are already sensitised and large numbers of anti-D antibodies can be produced immediately if any foetal blood cells enter the maternal circulation. The anti-D antibodies can cross the placenta and cause agglutination of foetal red blood cells, a condition known as haemolytic disease of the newborn.
221
Q

What effect can haemolytic disease of the newborn have on the child?

A

Agglutination of foetal red blood cells can lead to death, or serious illness.

222
Q

Why does foetal death, or serious illness, due to haemolytic disease of the newborn seldom occur today?

A
  • As rhesus negative mother’s are treated during pregnancy (around 30 weeks) by being given an injection of anti-D antibodies.
  • These attach to any antigen D-containing foetal red blood cell fragments that may pass across the placenta and enter the mother’s circulation before the mother’s B-lymphocytes are stimulated to produce anti-D antibodies.
  • Following birth, if the baby proves to be rhesus positive, another injection of anti-D antibodies is given with 72 hours.
  • However, if medical screening and intervention is bypassed and the condition does occur, the baby can be treated by blood transfusion.
223
Q

Foetal death, or serious illness, due to haemolytic disease of the newborn seldom occurs today as:
• Rhesus negative mother’s are treated during pregnancy (around 30 weeks) by being given an injection of anti-D antibodies.
• These attach to any antigen D-containing foetal red blood cell fragments that may pass across the placenta and enter the mother’s circulation before the mother’s B-lymphocytes are stimulated to produce anti-D antibodies.
• Following birth, if the baby proves to be rhesus positive, another injection of anti-D antibodies is given with 72 hours.

How can the newborn child be treated if medical screening and intervention is bypassed and the condition does occur?

A

By blood transfusion

224
Q

What are antibiotics?

A

Drugs that are developed to kill bacteria.

225
Q

Antibiotics are drugs that are developed to kill bacteria. Different antibiotics work …

A

In different ways

226
Q

Antibiotics are drugs that are developed to kill bacteria. Different antibiotics work in different ways but they usually kill bacteria by one or more of the following methods:

A
  • Disrupt cell wall formation by inhibiting an enzyme involved in the process. The bacteria are killed as the cell bursts, as it cannot resist osmotic pressure due to a weakened cell wall. Penicillin works in this way.
  • Inhibit metabolic processes including protein synthesis, for example, erythromycin destroys the ribosomes in prokaryotic cells.
227
Q

What is the main advantage of erythromycin?

A

The fact that erythromycin does not affect the larger ribosomes (80S) in eukaryotic cells means it can disrupt protein synthesis in bacteria (70S ribosomes) and not damage the ribosomes in patients taking this antibiotic.

228
Q

Antibiotics are drugs that are developed to kill bacteria. Different antibiotics work in different ways but they usually kill bacteria by one or more of the following methods:

  • Disrupt cell wall formation by inhibiting an enzyme involved in the process. The bacteria are killed as the cell bursts, as it cannot resist osmotic pressure due to a weakened cell wall. Penicillin works in this way.
  • Inhibit metabolic processes including protein synthesis, for example, erythromycin destroys the ribosomes in prokaryotic cells.

However, in recent decades …

A

More and more species of bacteria are becoming antibiotic resistant.

229
Q

Bacteria are antibiotic when …

A

One, or more, antibiotics no longer have an effect on them.

230
Q

When one, or more, antibiotics no longer have an effect on a species of bacteria, the bacteria can be described as …

A

Antibiotic resistant

231
Q

Mutations in the bacterial genome lead to …

A

Metabolic changes that result in antibiotics no longer being effective

232
Q

Mutations in the bacterial genome lead to metabolic changes that result in antibiotics no longer being effective. As bacteria can reproduce very rapidly …

A

By binary fission (asexually), one resistant bacterium can very rapidly result in a large population of antibiotic resistant bacteria.

233
Q

Draw a diagram showing how antibiotic resistance can arise in a population of bacteria

A

Textbook page 34

234
Q

How can some bacteria be resistant to penicillin?

A

Penicillin-resistant bacteria have evolved a number of methods of resisting the effects of penicillin.

235
Q

Penicillin-resistant bacteria have evolved a number of methods of resisting the effects of penicillin. These include:

A
  • Producing penicillinase to break penicillin down.
  • Exporting the active ingredient in penicillin out of the cell before it can work.
  • Alternative metabolic pathways in cell wall formation that render the penicillin ineffective.
236
Q

Some antibiotic resistant bacteria are …

A

Resistant to a number of types of antibiotics

237
Q

Some antibiotic resistant bacteria are resistant to a number of types of antibiotics and the risk is …

A

That some strains could become resistant to all antibiotics

238
Q

Some antibiotic resistant bacteria are resistant to a number of types of antibiotics and the risk is that some strains could become resistant to all antibiotics, resulting in …

A

A so-called ‘antibiotic winter’.

239
Q

The graph below shows deaths in Northern Ireland where the antibiotic resistant MRSA (Methicillin Resistant Staphylococcus aureus) was the underlying cause of death between 2004 and 2014.

The decrease in deaths in recent years is due to …

A
  1. A more rigorous hygiene culture in hospitals.
  2. More effective isolation of MRSA patients.
  3. A more judicious approach to antibiotic use.
  4. New targeted drug treatments.
240
Q

The graph below shows deaths in Northern Ireland where the antibiotic resistant MRSA (Methicillin Resistant Staphylococcus aureus) was the underlying cause of death between 2004 and 2014.

The decrease in deaths in recent years is due to a combination of a more rigorous hygiene culture in hospitals, more effective isolation of MRSA patients, a more judicious approach to antibiotic use and new targeted drug treatments. It doesn’t mean that …

A

The problem of antibiotic resistance is decreasing!

241
Q
  • The importance of discovering new sources of antibiotics to society and economy

With so many bacteria being antibiotic resistant it is very important that …

A

New sources of antibiotics are found.

242
Q

Why is it important that new sources of antibiotics are found?

A

As many bacteria are antibiotic resistant to the current generation of antibiotics.

243
Q
  • The importance of discovering new sources of antibiotics to society and economy

With so many bacteria being antibiotic resistant it is very important that new sources of antibiotics are found. It is hoped that …

A

Bacteria that are resistant to the current generation of antibiotics will not be resistant to ‘new generation’ antibiotics that work in different ways.

244
Q

What are the benefits to the individual and society of discovering new antibiotics?

A

Similar to the benefits of having vaccination programmes with very high rates of uptake, ie more effective treatment, less treatment costs and less time off work.

245
Q
  • The importance of discovering new sources of antibiotics to society and the economy

Many research programmes are investigating the possibility of …

A

Finding new sources of antibiotics in natural environments

246
Q
  • The importance of discovering new sources of antibiotics to society and the economy

Many research programmes are investigating the possibility of finding new sources of antibiotics in natural environments, for example, …

A

The soil

247
Q
  • The importance of discovering new sources of antibiotics to society and the economy

Many research programmes are investigating the possibility of finding new sources of antibiotics in natural environments, for example, the soil, an environment where …

A

Some types of microbe naturally produce antimicrobial substances as a defence mechanism within the soil against competing microbes.

248
Q
  • The importance of discovering new sources of antibiotics to society and the economy

Many research programmes are investigating the possibility of finding new sources of antibiotics in natural environments, for example, the soil, an environment where some types of microbe naturally produce antimicrobial substances as a defence mechanism within the soil against competing microbes. Recent research has been investigating …

A

The antibiotic properties of some bacteria that are naturally found in the human nasal cavity.

249
Q

How rapidly a disease spreads through a population depends on many factors including …

A
  1. How easily it is spread from person to person.
  2. How likely someone will fall ill to the disease once infected.
  3. Whether there is a vaccination for that disease and the percentage uptake of that vaccination.
  4. Bacterial resistance to antibiotics is another factor if the disease in question is caused by a bacterium.
250
Q

Diseases that spread rapidly through a small region (usually within one country) and affect a higher proportion of the population than normal are called …

A

Epidemics

251
Q

Diseases affecting many thousands of people or several countries at the same time are referred to as …

A

Pandemics

252
Q

What is an epidemic?

A

A disease that spreads rapidly through a small region (usually within one country) and affects a higher proportion of the population than normal.

253
Q

What is a pandemic?

A

A disease that affects many thousands of people or several countries at the same time.

254
Q

What type of microbe is the major cause of epidemics and pandemics?

A

Although scientists are very worried that antibiotic resistance in bacteria could lead to the rapid spread of previously controlled bacterial infections, most major epidemics and pandemics are caused by viruses.

255
Q

What are some of the factors that make viruses the more likely causal agents of widespread infections?

A
  1. Viruses have very small genomes that are prone to mutation.
  2. Many disease-causing viruses are retroviruses with RNA in the genome. These viruses are much less stable than those with the genome as DNA.
  3. Antibiotics are not effective against viruses.
256
Q

Give some examples of diseases caused by viruses with RNA as the genetic material

A 
Influenza
SARS
rabies
Hendra
Ebola
AIDS
257
Q

It is though that AIDS (arising from …

A

HIV infection)

258
Q

It is thought that AIDS (arising from HIV infection) has been responsible for …

A

30 million plus deaths over the last few decades.

259
Q

What was the result of the ‘Spanish’ flu pandemic?

A

The ‘Spanish’ flu virus killed between 30-50 million people in a worldwide pandemic in 1918-1919.

260
Q

Case Study - HIV and AIDS

The virus that causes AIDS is …

A

HIV, a retrovirus that converts its RNA to DNA in host cells.

261
Q

Humans infected by HIV usually suffer …

A

Long term damage to their immune systems with the result that they eventually succumb to one or more of the diseases associated with AIDS.

262
Q

Note: HIV describes …

A

The disease-causing virus

263
Q

Note: HIV describes the disease-causing virus and people infected are described as …

A

HIV positive (ie they produce antibodies to the antigen(s) of this virus).

264
Q

Note: HIV describes the disease-causing virus and people infected are described as HIV positive (ie they produce antibodies to the antigen(s) of this virus). AIDS is the term used to describe …

A

The syndrome of diseases associated with long term infection with HIV; diseases that are a consequence of a much weakened immune system.

265
Q

How did HIV arise?

A
  • It is thought that the HIV virus mutated from a similar virus (SIV) that causes the same type of immunodeficiency in chimpanzees that HIV does in humans.
  • The virus ‘transferred’ to human(s) in the early 1900s in central Africa, possibly through a human being bitten by a chimp or through eating or handling chimp meat.
266
Q

How did HIV spread?

A
  • Once HIV had evolved in humans, the disease AIDS was restricted to isolated pockets in central Africa for decades and only came to widespread public attention in western countries in the 1980s.
  • Major reasons for AIDS ‘exploding’ in western populations at that time included the advent of globalisation, the development of a more casual approach to sex in many societies and the increased use of air travel.
  • Each of these factors contributed to more opportunity for infection by HIV carriers in previously HIV-free societies.
267
Q

What are some of the major reasons for HIV ‘exploding’ in western populations in the 1980s?

A
  1. The advent of globalisation.
  2. The development of a more casual approach to sex in many societies.
  3. Increased use of air travel.
268
Q

It is thought that the HIV virus mutated from a similar virus (SIV) that causes the same type of immunodeficiency in chimpanzees that HIV does in humans. The virus ‘transferred’ to human(s) in the early 1900s in central Africa, possibly through a human being bitten by a chimp or through eating or handling chimp meat.

Once HIV had evolved in humans, the disease AIDS was restricted to isolated pockets in central Africa for decades and only came to widespread public attention in western countries in the 1980s. Major reasons for AIDS ‘exploding’ in western populations at that time included the advent of globalisation, the development of a more casual approach to sex in many societies and the increased use of air travel. Each of these factors contributed …

A

To more opportunity for infection by HIV carriers in previously HIV-free societies.

269
Q

Why is AIDS considered to be a disease-causing microbe that can potentially cause epidemics or pandemics?

A
  • (Until recently) HIV meets many of the criteria associated with disease-causing microbes that can potentially cause epidemics or pandemics.
  • It is an unstable retrovirus that has high rates of mutation.
  • It is not controlled by antibiotics.
  • It cannot be vaccinated against
  • (Until recently) there are very few drugs that are effective in its control.
270
Q

Why have death rates from HIV significantly reduced in recent years?

A

New antiretroviral drug treatments have significantly reduced death rates from HIV, greatly extending the life expectancy of patients with the condition.

271
Q
  • Animals as reservoirs of disease-causing viruses

In the case study on HIV and AIDS it was noted that HIV originated from …

A

A similar virus (SIV) in chimpanzees.

272
Q
  • Animals as reservoirs of disease-causing viruses

In the case study on HIV and AIDS it was noted that HIV originated from a similar virus (SIV) in chimpanzees before …

A

Crossing over into humans.

273
Q
  • Animals as reservoirs of disease-causing viruses
    In the case study on HIV and AIDS it was noted that HIV originated from a similar virus (SIV) in chimpanzees. Before crossing over into humans, SIV had almost certainly …
A

Co-existed with its primate hosts for a very long time.

274
Q

Animal species that harbour viruses that subsequently cause disease in humans are described as …

A

Reservoirs for that virus.

275
Q

What are reservoir species?

A
  • Animal species that harbour viruses that subsequently cause disease in humans are described as reservoirs for that virus.
  • Reservoir species often suffer little harm from the viruses and they are not really vectors as such, as they are not adapted to transfer the pathogen to another species; if a transfer does occur, it is usually a chance event.
276
Q

Terms such as ‘bird flu’ and ‘swine flu’ give a clue to …

A

The reservoir origins of the viruses responsible for causing these conditions.

277
Q

Animal species that harbour viruses that subsequently cause disease in humans are described as reservoirs for that virus. Reservoir species often suffer little harm from the viruses and they are not really vectors as such, as they are not adapted to transfer the pathogen to another species; if a transfer occurs, it is usually a chance event. Terms such as ‘bird flu’ and ‘swine flu’ give a clue to the reservoir origins of the viruses responsible for causing these conditions.

There are many example of viruses …

A

Transferring from other animal species to humans and then causing epidemics and pandemics.

278
Q

Animal species that harbour viruses that subsequently cause disease in humans are described as reservoirs for that virus. Reservoir species often suffer little harm from the viruses and they are not really vectors as such, as they are not adapted to transfer the pathogen to another species; if a transfer occurs, it is usually a chance event. Terms such as ‘bird flu’ and ‘swine flu’ give a clue to the reservoir origins of the viruses responsible for causing these conditions.

There are many example of viruses transferring from other animal species to humans and then causing epidemics and pandemics. Historically, …

A

A range of bat species have had a very significant role in this inter-species spread.

279
Q

Animal species that harbour viruses that subsequently cause disease in humans are described as reservoirs for that virus. Reservoir species often suffer little harm from the viruses and they are not really vectors as such, as they are not adapted to transfer the pathogen to another species; if a transfer occurs, it is usually a chance event. Terms such as ‘bird flu’ and ‘swine flu’ give a clue to the reservoir origins of the viruses responsible for causing these conditions.

There are many example of viruses transferring from other animal species to humans and then causing epidemics and pandemics. Historically, a range of bat species have has a very significant role in this inter-species spread.

Bats have been (or are) …

A

Reservoirs for the viruses that cause Marburg, SARS and Nipah, and are an initial reservoir for rabies before its transfer into dogs (and then into humans).

280
Q

Why are bats suitable reservoirs for disease-causing pathogens that subsequently infect humans?

A
  1. They are mammals and have a very similar physiology to humans.
  2. They are social animals and are in very close contact with large numbers of other bats, thereby ensuring that a high proportion of the bat population are carriers, thus increasing the possibility of cross-infection.
  3. They fly large ranges and therefore are potentially in contact with other organisms (humans) considerable distances away from their base.
281
Q

There are several reasons why bats make suitable reservoirs for disease-causing pathogens that subsequently infect humans. These include:

  • They are mammals and have a very similar physiology to humans.
  • They are social animals and are in very close contact with large numbers of other bats, thereby ensuring that a high proportion of the bat population are carriers, thus increasing the possibility of cross-infection.
  • They fly large ranges and therefore are potentially in contact with other organisms (humans) considerable distances away from their base.

A significant factor leading to the inter-species transfer of some viruses from bats to humans in recent decades has been …

A

The continual encroachment of man into habitats frequented by bats as a consequence of urbanisation and the clearing of woodland for housing and agriculture.

282
Q

There are several reasons why bats make suitable reservoirs for disease-causing pathogens that subsequently infect humans. These include:

  • They are mammals and have a very similar physiology to humans.
  • They are social animals and are in very close contact with large numbers of other bats, thereby ensuring that a high proportion of the bat population are carriers, thus increasing the possibility of cross-infection.
  • They fly large ranges and therefore are potentially in contact with other organisms (humans) considerable distances away from their base.

A significant factor leading to the inter-species transfer of some viruses from bats to humans in recent decades has been the continual encroachment of man into habitats frequented by bats as a consequence of urbanisation and the clearing of woodland for housing and agriculture. The bats referred to in the above paragraphs are …

A

The ‘flying foxes’ or ‘fruit’ bags found in tropical and sub-tropical areas; not the bats found in the British Isles.

283
Q

The previous section on viruses underlines that it is not just important to find new antibiotics. It is also essential that a new generation of …

A

Antimicrobials are developed.

284
Q

What are antimicrobial drugs?

A

Antimicrobial drugs are drugs that are effective against a broader range of microbes than antibiotics, or are effective against those pathogens that antibiotics cannot combat, for example, viruses.

285
Q
  • Diagnosing infection - an update

In recent years there has been …

A

Significant progress in the earlier, and more accurate, diagnosis of infection.

286
Q
  • Diagnosing infection - an update
    In recent years there has been significant progress in the earlier, and more accurate, diagnosis of infection. Earlier and more accurate diagnosis can lead to …
A

More effective treatment at an earlier stage of disease progression.

287
Q
  • Diagnosing infection - an update
    In recent years there has been significant progress in the earlier, and more accurate, diagnosis of infection. Earlier and more accurate diagnosis can lead to more effective treatment at an earlier stage of disease progression.

These advances include the use of …

A

ELISA techniques and the detection of cytokines as biomarkers.

288
Q

What does ELISA stand for?

A

Enzyme-linked immunosorbent assay

289
Q

Briefly state what an ELISA technique is

A

This is a laboratory technique that uses antibodies, enzymes and other molecules as biomarkers to detect the presence of particular molecules in the body.

290
Q

What can ELISA assays test for?

A

ELISA assays can test for a small, or large, number of potential antigens or biomarkers at the same time, thus screening for a large number of possible conditions.

291
Q

Typically, how is an ELISA test plate produced?

A
  • Typically, body fluids from a patient are added to a number of wells on a plate (a sophisticated spotting tray) and a range of antibodies are added to these wells.
  • Reaction between antibody and antigen triggers an enzyme linked to the antibody into causing a colour change thus identifying the antigens or other molecules present.
292
Q

What can ELISA diagnostic kits be used to detect?

A
  • Pathogens in the body
  • Cancer cell markers
  • Cardiac disease markers
  • Pregnancy (in home pregnancy kits)
293
Q

What are the advantages of ELISA techniques?

A

They have the advantage of enabling early, rapid screening and can provide a wide range of diagnostic feedback from the one test.

294
Q

Describe how an ELISA technique can be used for pregnancy testing

A
  • Following the implantation of an egg in the uterine wall, increased levels of the hormone chorionic gonadotropin (hCG) can be detected in the blood or urine.
  • In a pregnancy test, hCG antigens are detected by complementary hCG (monoclonal) antibodies immobilised on the ELISA test plate.
  • The formation of this antigen-antibody complex results in a linked enzyme reacting to produce the characteristic colour change associated with pregnancy test kits.
295
Q

Describe how an ELISA technique can be used to test for viral pathogens

A
  • An ELISA plate impregnated with the viral antigens is coated with blood serum from the patient.
  • If the patient’s blood contains complementary antibodies (evidence of infection), then the antigen-antibody complex triggers an enzyme reaction that leads to a colour change.
296
Q

What stimulates the enzyme reaction in an ELISA test plate?

A
  • The antibody-antigen complex normally stimulates the enzyme reaction, it is not the substrate as such.
  • The substrate for the enzyme is normally added as part of the process.
297
Q

What are cytokines?

A
  • Chemicals released by T-helper and other cells as part of the immune response during infection.
  • They are small proteins that help coordinate the immune response.
  • They can be found in the blood and are used as biomarkers to identify a number of conditions including TB and rheumatoid arthritis.
298
Q

Practical work - Investigating microorganisms using aseptic technique

Aseptic technique is used to …

A

Prevent contamination when working with microorganisms.

299
Q

What technique is used to prevent contamination when working with microorganisms?

A

Aseptic technique

300
Q

Aseptic technique is used to prevent contamination when working with microorganisms. This includes …

A

Preventing contamination of both the microbe culture and contamination of the individuals working with the microbes

301
Q

What substance(s) can be used to culture microorganisms?

A

Solid agar or liquid broth

302
Q

Aseptic technique is used to prevent contamination when working with microorganisms. This includes preventing contamination of both the microbe culture and contamination of the individuals working with the microbes.

Solid agar or liquid broth can be used to culture microorganisms and care is needed when …

A

Transferring microorganisms to Petri dishes or other containers for investigation.

303
Q

What is the common procedure for transferring microorganisms?

A

Metal inoculating or disposable plastic loops can be used.

  1. If using a metal inoculating loop it is necessary to ‘flame’ the loop in the hottest part of a Bunsen flame until it becomes red-hot.
    - After sterilising the metal loop it is necessary to air-cool the loop as when red-hot it would kill any microorganisms it comes into contact with.
    - After transfer of microorganisms, it is necessary to re-sterilise the loop.
    - However, for safety reasons it is important not to create a microorganism-rich aerosol when doing this.
    - Once used, disposable plastic loops should be discarded into a solution of disinfectant.
  2. When transferring microorganisms from a culture bottle to a Petri dish (or a fresh culture bottle), the lid of the bottle should be held in the same hand that holds the culture bottle and not allowed to touch the bench, with the other hand holding the inoculating loop.
    - Immediately after opening the culture bottle, it’s neck should be quickly passed through the Bunsen flame to sterilise the lid region; this should be repeated immediately before replacing the lid on the culture bottle.
  3. When transferring the microorganisms to a Petri dish, the lid of the dish should be only raised enough to allow the microorganisms to be added to the agar.
  • Petri dishes should be labelled on the outside of the base (and not the lid).
  • They should be incubated upside down in an incubator at an appropriate temperature for the microorganism concerned.
304
Q

What is an alternative method for transferring microorganisms?

A

• Alternatively, a spread plate method can be used, when cells in suspension are used in inoculation.

  • In this case an L-shaped spreader is used to spread the inoculating bacteria over the surface of the agar.
  • Plastic sterile disposable spreaders are a suitable alternative to the glass spreaders that require sterilisation before and after use.
305
Q

How can the effect of different antibiotics on bacteria be investigated at the very basic level?

A
  • At the very basic level, discs of antibiotics can be placed on agar in a Petri dish.
  • The agar is inoculated with a particular type of bacterium and the effect of the antibiotic (or antibiotics) on that strain of bacteria can be investigated.
306
Q

Draw a diagram showing how the effect of different antibiotics on bacteria can be investigated at the very basic level.

A

Textbook page 40

307
Q

What is an E-strip?

A

An E-strip is a prepared strip that contains a concentration gradient of antibiotic (or antimicrobial compound) running the length of the strip.

308
Q

How can the effect of different antibiotics on bacteria be investigated at a more sophisticated level?

A
  • Alternatively, E-strips are a more sophisticated way of measuring the effect of different concentrations of antibiotic on bacteria.
  • The process involves placing the E-strip on the agar of a Petri dish that has been inoculated with a bacterium.
  • Following incubation (normally between 18-72 hours needed), and depending on the E-strip and microorganism used, a result similar to that in the diagram below can be observed.
309
Q

As E-strips contain markings that show antibiotic concentrations at particular points on the strip, it is possible to work out …

A

The minimum antibiotic concentration that is necessary to inhibit bacterial growth.

310
Q

Draw a diagram showing the use of E-strips to investigate the effect of different concentrations of antibiotics on bacterial growth

A

Textbook page 40

311
Q

The technique of preparing a streak plate is commonly used to …

A

Isolate single colonies of microbial cells, ie a pure culture of cells, all of which share the same parental cell.

312
Q

Outline the procedure for preparing a streak plate to isolate single colonies. Include a flow diagram.

A
  1. Using an inoculating loop, spread the microorganisms over a small section of the agar in the Petri dish (the initial inoculation, stage 1).
  2. Then, with a new/sterilised inoculating loop, ‘streak’ several lines of microorganism across the agar at an angle, taking care not to allow the separate ‘lines’ to overlap (stage 2).
  3. Repeat stage 2 once or twice, making sure that a sterile loop is used on each occasion (stages 3 & 4).
  4. Make a final single streak as shown (stage 5).
  5. Incubate the Petri dish at a suitable temperature. After 24 hours or so it should be possible to identify isolated pure colonies (stage 6).

Flow diagram on page 41

313
Q
  • Investigating the antimicrobial properties of plants

Many plants have …

A

A range of defences against microorganisms.

314
Q
  • Investigating the antimicrobial properties of plants

Many plants have a range of defences against microorganisms. These help …

A

Prevent decay and further loss in parts of plants, for example leaves, which become damaged in their natural environment.

315
Q
  • Investigating the antimicrobial properties of plants

Many plants have a range of defences against microorganisms. These help prevent decay and further loss in parts of plants, for example leaves, which become damaged in their natural environment.

Many common woodland plants, such as …

A

Wood anemone, bluebell, lesser celandine, wild garlic and mint

316
Q
  • Investigating the antimicrobial properties of plants

Many plants have a range of defences against microorganisms. These help prevent decay and further loss in parts of plants, for example leaves, which become damaged in their natural environment.

Many common woodland plants, such as wood anemone, bluebell, lesser celandine, wild garlic and mint, produce …

A

Compounds that prevent or reduce fungal and/or bacterial growth

317
Q

What is the procedure for investigating the microbial properties of plants?

A
  1. Grind up the leaves of each woodland plant and a small amount of water in separate mortars.
  2. Prepare some agar plates (Petri dishes) and spread a fungus or bacterium culture on the plate using appropriate aseptic techniques.
  3. Soak a small disk of filter paper with each plant extract and place on the agar in the Petri dish.
  4. Incubate for 24-48 hours and compare results in the different Petri dishes.

Alternatively, instead of comparing antimicrobial properties in different plants, it is possible to compare the effect of extract concentration, temperature of incubation and many other variables.

A2 Biology Module 1 - Physiology, Coordination and Control, and Ecosystems (9 decks)

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