5.1: Defence mechanisms

Question 1

The immune system

Answer 1

The immune system is a system of biological:
1. Structures
2. Processes
within an organism that protects against disease by identifying and killing pathogens (and tumour cells)

Question 2

Pathogen

Answer 2

A pathogen is a disease-causing organism

Question 3

Infection

Answer 3

An infection is an interaction between the:

1. Pathogen
2. Body’s various defence mechanisms

Question 4

Immunity

Answer 4

Immunity is when the body’s defence is better prepared for that pathogen

Question 5

Many pathogens cannot cause disease due to what?

Answer 5

Many pathogens cannot cause disease due to:
1. Non-specific barriers
2. Cellular defences
that prevent them from entering the body

Question 6

Many pathogens cannot cause disease due to non-specific barriers (what barriers) and cellular defences that prevent them from entering the body?

Answer 6

Many pathogens cannot cause disease due to:
1. Non-specific barriers (physical and chemical barriers)
2. Cellular defences
that prevent them from entering the body

Question 7

The main defence mechanisms of the body:

Defence mechanisms are what or what?

Answer 7

Defence mechanisms are:
1. Specific
Or,
2. Non-specific

Question 8

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With specific defence mechanisms, the response is what?

Answer 8

With specific defence mechanisms, the response is:

1. Slower
2. Specific to each pathogen

Question 9

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With non-specific defence mechanisms, the response is what?

Answer 9

With non-specific defence mechanisms, the response is:

1. Immediate
2. The same for all pathogens

Question 10

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With non-specific defence mechanisms, the response is immediate and the same for all pathogens.
What are the non-specific defence mechanisms of the body?

Answer 10

The non-specific defence mechanisms of the body are:

1. Physical barriers
2. Phagocytosis

Question 11

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With specific defence mechanisms, the response is slower and specific to each pathogen.
What are the specific defence mechanisms of the body?

Answer 11

The specific defence mechanisms of the body are the:

1. Cell-mediated response - T lymphocytes
2. Humoral response - B lymphocytes

Question 12

What about when the defence mechanisms of the body fail?
Unfortunately, the defence mechanisms of the body aren’t perfect.
They can and do fail some of the time.
When this happens, what can microorganisms do?

Answer 12

When this happens, microorganisms can:

1. Enter the bloodstream
2. Cause an infection

Question 13

An infection is an interaction between the pathogen and the body’s various defence mechanisms.
Sometimes the pathogen does what and the individual dies?

Answer 13

Sometimes the pathogen overwhelms the defences and the individual dies

Question 14

An infection is an interaction between the pathogen and the body’s various defence mechanisms.
Sometimes the pathogen overwhelms the defences and the individual dies.
Sometimes the body’s defence mechanisms do what and the individual recovers from the disease?

Answer 14

Sometimes the body’s defence mechanisms overwhelm the pathogen and the individual recovers from the disease

Question 15

An infection is an interaction between the pathogen and the body’s various defence mechanisms.
Sometimes the pathogen overwhelms the defences and the individual dies.
Sometimes the body’s defence mechanisms overwhelm the pathogen and the individual recovers from the disease.
Having overwhelmed the pathogen, however, the body’s defences seem to be better prepared for a second infection from the same pathogen and can kill it before it can cause any harm.
This is known as immunity and is the main reason why some people are unaffected by certain pathogens.
Much depends on the overall state of health of an individual.
A fit, healthy adult will rarely die to an infection.
Who are usually more vulnerable?

Answer 15

1. Those in ill health
2. The young
3. The elderly
   are usually more vulnerable

Question 16

To defend the body from invasion by foreign material, lymphocytes must be able to do what?

Answer 16

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish:
1. The body’s own cells and molecules (self)
from those
2. Molecules that are foreign (non-self)

Question 17

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, what would the lymphocytes do?

Answer 17

If they could not do this, the lymphocytes would destroy the organism’s own tissues

Question 18

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, the lymphocytes would destroy the organism’s own tissues.
Each type of cell, self or non-self, has specific molecules on its surface that do what?

Answer 18

Each type of cell:
1. Self
Or,
2. Non-self
,has specific molecules on its surface that identify it

Question 19

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, the lymphocytes would destroy the organism’s own tissues.
Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and what?

Answer 19

This is because proteins have:

1. Enormous variety
2. A highly specific tertiary structure

Question 20

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, the lymphocytes would destroy the organism’s own tissues.
Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify what?

Answer 20

It is these protein molecules which usually allow the immune system to identify:

1. Pathogens
2. Non-self material
3. Toxins
4. Abnormal body cells

Question 21

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example what, non-self material, toxins and abnormal body cells?

Answer 21

It is these protein molecules which usually allow the immune system to identify:

1. Pathogens, for example the human immunodeficiency virus
2. Non-self material
3. Toxins
4. Abnormal body cells

Question 22

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as what, toxins and abnormal body cells?

Answer 22

It is these protein molecules which usually allow the immune system to identify:

1. Pathogens, for example the human immunodeficiency virus
2. Non-self material, such as cells from other organisms of the same species
3. Toxins
4. Abnormal body cells

Question 23

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by what, and abnormal body cells?

Answer 23

It is these protein molecules which usually allow the immune system to identify:

1. Pathogens, for example the human immunodeficiency virus
2. Non-self material, such as cells from other organisms of the same species
3. Toxins, including those produced by certain pathogens like the bacterium that causes cholera
4. Abnormal body cells

Question 24

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as what?

Answer 24

It is these protein molecules which usually allow the immune system to identify:

1. Pathogens, for example the human immunodeficiency virus
2. Non-self material, such as cells from other organisms of the same species
3. Toxins, including those produced by certain pathogens like the bacterium that causes cholera
4. Abnormal body cells, such as cancer cells

Question 25

Each type of cell, self or non-self, has specific molecules on its surface that identify it. While these molecules can be of a variety of types, it is the proteins that are the most important. This is because proteins have enormous variety and a highly specific tertiary structure. It is this variety of specific 3D structure that distinguishes one cell from another. It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells. All of the above are potentially harmful and their identification is the first stage in removing what?

Answer 25

All of the above are potentially harmful and their identification is the first stage in removing the threat they pose

Question 26

Each type of cell, self or non-self, has specific molecules on its surface that identify it. While these molecules can be of a variety of types, it is the proteins that are the most important. This is because proteins have enormous variety and a highly specific tertiary structure. It is this variety of specific 3D structure that distinguishes one cell from another. It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells. All of the above are potentially harmful and their identification is the first stage in removing the threat they pose. Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants. The immune system recognises these as non-self, even though they have come from individuals of the same what?

Answer 26

The immune system recognises these as non-self, even though they have come from individuals of the same species

Question 27

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells. All of the above are potentially harmful and their identification is the first stage in removing the threat they pose. Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants. The immune system recognises these as non-self, even though they have come from individuals of the same species. The immune system therefore attempts to do what?

Answer 27

The immune system therefore attempts to destroy the transplant

Question 28

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells. All of the above are potentially harmful and their identification is the first stage in removing the threat they pose. Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants. The immune system recognises these as non-self, even though they have come from individuals of the same species. The immune system therefore attempts to destroy the transplant. To minimise the effect of this tissue rejection, donor tissues for transplant are normally what?

Answer 28

To minimise the effect of this tissue rejection, donor tissues for transplant are normally matched as closely as possible to those of the recipient

Question 29

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells. All of the above are potentially harmful and their identification is the first stage in removing the threat they pose. Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants. The immune system recognises these as non-self, even though they have come from individuals of the same species. The immune system therefore attempts to destroy the transplant. To minimise the effect of this tissue rejection, donor tissues for transplant are normally matched as closely as possible to those of the recipient. The best matches often come from who?

Answer 29

The best matches often come from relatives that are genetically close

Question 30

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells. All of the above are potentially harmful and their identification is the first stage in removing the threat they pose. Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants. The immune system recognises these as non-self, even though they have come from individuals of the same species. The immune system therefore attempts to destroy the transplant. To minimise the effect of this tissue rejection, donor tissues for transplant are normally matched as closely as possible to those of the recipient. The best matches often come from relatives that are genetically close. In addition, what are often administered to reduce the level of the immune response that still occurs?

Answer 30

In addition, immunosuppressant drugs are often administered to reduce the level of the immune response that still occurs

Question 31

Why are specific lymphocytes not produced in response to an infection?

Answer 31

Specific lymphocytes are not produced in response to an infection, because they already exist

Question 32

Specific lymphocytes are not produced in response to an infection, because they already exist - all how many different types?

Answer 32

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types

Question 33

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types. Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, what?

Answer 33

Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen

Question 34

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types. Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen. The lymphocyte will what?

Answer 34

The lymphocyte will 'recognise' the pathogen

Question 35

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types. Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen. The lymphocyte will 'recognise' the pathogen. Not surprisingly with so many different lymphocytes, there are how many of each type?

Answer 35

Not surprisingly with so many different lymphocytes, there are very few of each type

Question 36

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types. Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen. The lymphocyte will 'recognise' the pathogen. Not surprisingly with so many different lymphocytes, there are very few of each type. When an infection occurs, what happens to the one type of lymphocyte already present that has the complementary proteins to those of the pathogen?

Answer 36

When an infection occurs, the one type of lymphocyte already present that has the complementary proteins to those of the pathogen is stimulated to divide to build up its numbers to a level where it can be effective in destroying it

Question 37

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types. Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen. The lymphocyte will 'recognise' the pathogen. Not surprisingly with so many different lymphocytes, there are very few of each type. When an infection occurs, the one type of lymphocyte already present that has the complementary proteins to those of the pathogen is stimulated to divide to build up its numbers to a level where it can be effective in destroying it. This explains why there is a time lag between what?

Answer 37

This explains why there is a time lag between: 1. Exposure to the pathogen 2. The body's defences bringing it under control

Question 38

How lymphocytes recognise cells belonging to the body: | 1. There are probably around 10 million different lymphocytes present when?

Answer 38

There are probably around 10 million different lymphocytes present at any time

Question 39

How lymphocytes recognise cells belonging to the body: | 1. There are probably around 10 million different lymphocytes present at any time, each capable of doing what?

Answer 39

There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape

Question 40

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, what are these lymphocytes constantly doing?

Answer 40

In the fetus, these lymphocytes are constantly colliding with other cells

Question 41

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Why is infection in the fetus rare?

Answer 41

Infection in the fetus is rare, because it is protected from the outside world by: 1. The mother 2. In particular, the placenta

Question 42

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. What will lymphocytes therefore do?

Answer 42

Lymphocytes will therefore collide almost exclusively with the body's own material (self)

Question 43

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that do what?

Answer 43

Some of the lymphocytes will have receptors that exactly fit those of the body's own cells

Question 44

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. What happens to these lymphocytes?

Answer 44

These lymphocytes either: 1. Die Or, 2. Are suppressed

Question 45

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (what) or are suppressed?

Answer 45

These lymphocytes either: 1. Die (apoptosis or cell death) Or, 2. Are suppressed

Question 46

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. What are the only remaining lymphocytes?

Answer 46

The only remaining lymphocytes are those that might fit foreign material (non-self)

Question 47

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only do what?

Answer 47

The only remaining lymphocytes: 1. Are those that might fit foreign material (non-self) 2. Therefore only respond to foreign material

Question 48

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material. 7. In adults, lymphocytes produced in the bone marrow initially only do what?

Answer 48

In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens

Question 49

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material. 7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens. Any lymphocytes that show an immune response to these self-antigens undergo what?

Answer 49

Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis)

Question 50

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material. 7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens. Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can do what?

Answer 50

Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes

Question 51

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material. 7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens. Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes. 8. No what will appear in the blood?

Answer 51

No clones of these anti-self lymphocytes will appear in the blood

Question 52

How lymphocytes recognise cells belonging to the body: 1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape. 2. In the fetus, these lymphocytes are constantly colliding with other cells. 3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta. 4. Lymphocytes will therefore collide almost exclusively with the body's own material (self). 5. Some of the lymphocytes will have receptors that exactly fit those of the body's own cells. These lymphocytes either die (apoptosis or cell death) or are suppressed. 6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material. 7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens. Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes. 8. No clones of these anti-self lymphocytes will appear in the blood, leaving only what?

Answer 52

No clones of these anti-self lymphocytes will appear in the blood, leaving only those that might respond to non-self antigens

Question 53

The first line of defence

Answer 53

The first line of defence are the physical barriers

Question 54

The first line of defence are the physical barriers. | What do the physical barriers do?

Answer 54

The physical barriers prevent the entry of: 1. Pathogens 2. Microorganisms only when they are intact

Question 55

The first line of defence are the physical barriers. The physical barriers prevent the entry of pathogens and microorganisms only when they are intact. Examples of the types of physical barriers

Answer 55

Examples of the types of physical barriers are: 1. Skin 2. Tears 3. Eyelashes 4. Mucus 5. Ciliated cells

Question 56

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a what barrier to infection?

Answer 56

The skin is a huge barrier to infection

Question 57

``` The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. What secrete sebum? ```

Answer 57

Sebaceous glands in the dermis secrete sebum

Question 58

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, a what substance?

Answer 58

Sebaceous glands in the dermis secrete sebum, an oily substance

Question 59

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin what?

Answer 59

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable

Question 60

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also what?

Answer 60

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic

Question 61

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so what does it do?

Answer 61

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it: 1. Is also acidic 2. So lowers the pH of the skin

Question 62

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so lowers the pH of the skin, thus inhibiting what?

Answer 62

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it: 1. Is also acidic 2. So lowers the pH of the skin ,thus inhibiting the growth of some types of bacteria

Question 63

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so lowers the pH of the skin, thus inhibiting the growth of some types of bacteria. Sweat is also a defence mechanism that contains what?

Answer 63

Sweat is also a defence mechanism that contains: 1. Salts 2. Enzymes

Question 64

The first line of defence are the physical barriers. Skin: The skin is an organ. The skin is a huge barrier to infection. Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so lowers the pH of the skin, thus inhibiting the growth of some types of bacteria. Sweat is also a defence mechanism that contains salts and enzymes, which make it difficult for bacteria to do what and make it difficult for certain types of bacteria to do what?

Answer 64

Sweat is also a defence mechanism that contains salts and enzymes, which make it difficult for: 1. Bacteria to inhabit the skin's surface 2. Certain types of bacteria to survive

Question 65

The first line of defence are the physical barriers. Tears: What do tears contain?

Answer 65

Tears contain lysozymes

Question 66

The first line of defence are the physical barriers. Tears: Tears contain lysozymes that are enzymes that can do what?

Answer 66

Tears contain lysozymes that are enzymes that can destroy bacterial cells

Question 67

The first line of defence are the physical barriers. Tears: Tears contain lysozymes that are enzymes that can destroy bacterial cells. What does this do?

Answer 67

This prevents the entry of pathogens in the eyes

Question 68

The first line of defence are the physical barriers. Eyelashes: What do eyelashes do?

Answer 68

Eyelashes respond to foreign bodies near the eyes

Question 69

The first line of defence are the physical barriers. Eyelashes: Eyelashes respond to foreign bodies near the eyes by what?

Answer 69

Eyelashes respond to foreign bodies near the eyes by blinking

Question 70

The first line of defence are the physical barriers. The digestive system: The stomach contains hydrochloric acid that lowers what?

Answer 70

The stomach contains hydrochloric acid that lowers its pH

Question 71

The first line of defence are the physical barriers. The digestive system: The stomach contains hydrochloric acid that lowers its pH to what?

Answer 71

The stomach contains hydrochloric acid that lowers its pH to between: 1. 1.5 2. 2.5 pH

Question 72

The first line of defence are the physical barriers. The digestive system: The stomach contains hydrochloric acid that lowers its pH to between 1.5 and 2.5 pH. What does this mean?

Answer 72

This means that it is an inhospitable environment for bacteria to survive

Question 73

What do cilia do?

Answer 73

Cilia sweep away trapped particles

Question 74

What does mucus do?

Answer 74

Mucus traps foreign bodies