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Biology > Chapter 11: Immunity > Flashcards

Chapter 11: Immunity Flashcards

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1
Q

What is an antigen?

A

An antigen is a substance that is foreign to the body and stimulates an immune response.

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2
Q

What are the two types of white blood cell?

A

Phagocytes and lymphocytes

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3
Q

What is the immune response?

A

The immune response is the complex series of responses of the body to the entry of a foreign antigen, involving the activity of lymphocytes and phagocytes.

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4
Q

What is ‘non-self’?

A

Non-self refers to any substance or cell that is recognised by the immune system as being foreign and will stimulate an immune response.

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5
Q

What is ‘self’?

A

Self refers to substances produced by the body that the immune system does not recognise as foreign, so they do not stimulate an immune response.

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6
Q

Where are phagocytes produced?

A

In the bone marrow

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7
Q

What are the two types of phagocytes?

A

Neutrophils and macrophages

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8
Q

Are neutrophils short or long lived cells?

A

Short

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9
Q

Which are larger: neutrophils or macrophages?

A

Macrophages.

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10
Q

Where are neutrophils found?

A

They are found in the blood. In fact, 60% of WBCs in the blood are neutrophils.

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11
Q

Where are macrophages found and in what form do they get there?

A

Macrophages travel in the blood as monocytes, which develop into macrophages once they leave the blood and settle into organs, removing any foreign matter found there.

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12
Q

Are macrophages long or short lived cells?

A

Long

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13
Q

Describe the stages of phagocytosis with respect to neutrophils

A

During an infection, some of the cells under attack release chemicals such as histamine. These, with any other chemicals released by the pathogens themselves, attract passing neutrophils to the site. The neutrophils move towards the pathogens which may be clustered together and covered with antibodies. The antibodies further stimulate the neutrophils to attack the pathogens due to the receptors on the neutrophils recognising the antibodies and attach to them. When the neutrophil attached to the pathogen, the cell surface membrane engulfs the pathogen and traps it within a phagocytic vacuole in a process called endocytosis. Digestive enzymes are secreted into the vacuole and therefore destroy the pathogen. After killing and digesting some pathogens, the neutrophils die and often collect at the site of infection as pus.

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14
Q

What is the function of a macrophage?

A

It plays a crucial role in initiating immune response. They do not destroy the pathogens completely and instead cut them up to display antigens that can be recognised by lymphocytes.

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15
Q

Which is bigger: lymphocyte or phagocyte?

A

Phagocytes

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16
Q

Where are lymphoctes produced?

A

In the bone marrow

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17
Q

What are the two types of lymphocytes?

A

B-lymphocytes and T-lymphocytes

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18
Q

Where do B -cells mature and where do they remain after maturation?

A

B cells remain in the bone marrow until they mature and then spread throughout the body, concentrating in the spleen and lymph nodes.

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19
Q

Where do T -cells mature and where do they remain after maturation?

A

T cells leave the bone marrow and mature in the thymus.

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20
Q

Do the B and T cells circulate around the blood and lymph and why?

A

This ensures that they are distribute around the body and interact with each other.

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21
Q

`What type of cell produces antibodies?

A

B-lymphocytes

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22
Q

What is a clone and describe the structure of antibodies in clones.

A

Mature B cells divide to produce a small number of cells that are able to make the same type of antibody. Each small group of identical cells is known as a clone. At his stage, the antibody molecules do not leave the cell and instead form part of the cell surface membrane as glycoprotein receptors which can combine specifically with one type of antigen.

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23
Q

How and when does clonal selection and expansion occur?

A

When an antigen enter the body for the first time, the small numbers of B cells with receptors complementary to that of the antigen are stimulated to divide repeatedly by mitosis. This stage is known as clonal selection producing a large number of B cells complementary to that antigen in a stage known as clonal expansion.

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24
Q

What are the two types of B cells?

A

Plasma and memory cells

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25
Q

When an antigen enters a body, what happens to the activated B cells after clonal expansion?

A

Some of these activated B cells become plasma cells that secrete antibody molecules. They do not live long and the antibody molecules secreted stay in the blood longer, until they too eventually decrease.
Other B cells become memory cells remaining in the blood for a very long time. If the same antigen is reintroduced after the first infection, memory cells divide rapidly differentiating into memory and plasma cells.

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26
Q

What is the difference in the rate of immune response between the primary and secondary response?

A

The primary response is slow because there are very few B cells that are specific to the antigen. The secondary response is quicker because there are many memory cells, which quickly divide and differentiate to secrete antibodies and produce more memory cells.

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27
Q

What is an antibody?

A

An antibody is a globular glycoprotein that form the group of plasma proteins called immunoglobins. They are secreted by B plasma cells in response to an antigen.

28
Q

Describe the structure of an antibody.

A

All antibodies consist of four polypeptide chains, with two long and two short chains. Disulfide bonds hold the chains together. Each molecule has two identical antigen binding sites made from both the long and short chains. The sequences in amino acids in these regions make the specific 3D shape which binds to one specific antigen. The antigen binding sites form the variable region. The hinge region between the two variable regions, gives flexibility for the antibody molecule to bind around the antigen.

29
Q

What are some of the functions of bacteria? (6)

A
  1. They combine with viruses and bacterial toxins preventing them from entering and damaging cells.
  2. They attach to the flagella of bacteria making them less active and easier for the phagocytes to engulf.
  3. Antibodies with multiple antigen binding sites may cause the clumping of bacteria reducing the spread of bacteria.
  4. Antibodies may make holes in the cell walls of bacteria causing them to burst via osmosis.
  5. Antibodies may coat bacteria making it easier for phagocytes to digest them.
  6. Antibodies may combine with toxins, neutralising them and making them harmless. These antibodies are called antitoxins.
30
Q

What are the two types of T cells?

A

Helper T cells and killer T cells

31
Q

What is the name of the receptors present on the surface of T cells?

A

They are called T cell receptors.

32
Q

What is antigen presentation?

A

The display of antigen on the surface of cells invaded by a pathogen is called antigen presentation.

33
Q

What is the function of helper T cells?

A

When helper T cells are activated, they release the hormone cytokines that stimulates the appropriate B cells to divide and develop into plasma cells and secrete antibodies. They may also stimulate macrophages to carry out phagocytosis more vigorously or stimulate killer T cells to divide by mitosis and to differentiate by producing vacuoles full of toxins.

34
Q

What is the function of killer T cells?

A

Killer T cells recognise the antigens, attach themselves on the surface of infected cells, and secrete toxic substances, killing the body cells and the pathogens inside.

35
Q

What are platelets?

A

They are small cell fragments that do not have a nucleus and are formed from the break down of cells in the bone marrow. They release substances that stimulate blood clotting.

36
Q

Which type of cells does HIV affect?

A

Helper T cells.

37
Q

Where are white blood cells made and from what cells?

A

WBCs originate from stem cells in the bone marrow.

38
Q

What are the two types of bone marrow stem cells?

A

Myeloid stem cells and lymphoid stem cells

39
Q

What types of cells are produced by myeloid stem cells?

A

Neutrophils, monocytes and platelets

40
Q

What types of cells are produced by lymphoid stem cells?

A

Both lymphocytes(B and T cells)

41
Q

What is leukaemia?

A

Leukaemias are cancers of stem cells.

42
Q

How does leukaemia lead to immunosuppression?

A

Immature WBCs are produced very quickly. This means that the body does not have enough RBCs or platelets leading to anaemia and increasing the risk of excessive bleeding. Also, the numbers of lymphocytes and neutrophils decrease so that people with these cancers are more susceptible to infections and are said to be immunosuppressed.

43
Q

What is active immunity?

A

Active immunity is immunity gained when an antigen enters the body, an immune response occurs and antibodies are produced by plasma cells.

44
Q

What is passive immunity?

A

Passive immunity is immunity gained without an immune response. It may be where antibodies are injected or where antibodies pass from mother to child across the placenta or in breast milk.

45
Q

What is natural immunity?

A

Natural immunity is immunity gained by being infected or by receiving antibodies from the mother across the placenta or in breast milk.

46
Q

What is artificial immunity?

A

Artificial immunity is immunity gained either by vaccination or by injecting antibodies.

47
Q

What is vaccination and what type of immunity is it?

A

Vaccination is giving a vaccine containing antigens for a disease, either by injection or by mouth. It constitutes as artificial active immunity.

48
Q

What are antitoxins and what type of immunity is it?

A

Antitoxins is a preparation of human antibodies against a pathogen. This is only temporary as they are removed from the body due to being regarded as non-self. They provide artificial passive immunity.

49
Q

What is colostrum and what type of immunity is it?

A

Colostrum is a fluid produced by a mother’s breasts for the first four or five days after birth and contains an antibody called IgA which acts in the gut to prevent the growth of bacteria and viruses. This is natural passive immunity.

50
Q

What is a vaccine and how is it given?

A

A vaccine is a preparation of antigens which is used to stimulate an immune response artificially . It may contain a whole microorganism, a dead one, a harmless version, a harmless toxin or a preparation of surface antigens. They are either given intravenously or orally.

51
Q

Why do some people develop a poor response to vaccines?

A

Some may have a defective immune system and may not produce the necessary B and T cells. Some may suffer from malnutrition and do not have enough protein to make antibodies or clones of lymphocytes.

52
Q

What is an antigenic drift and shift?

A

When there are minor changes in the viral antigen, memory cells will recognise them and stimulate a secondary response. This is known as an antigenic drift. Major changes in antigen structure is known as antigenic shift.

53
Q

Why do eukaryotic pathogens have no effective vaccines in use against them?

A

This is due to the many genes compare to that of bacteria and viruses as well as the antigen change at different stages.

54
Q

What is the type of organism that causes smallpox?

A

Virus

55
Q

What is the name of the organism that causes smallpox?

A

Variola

56
Q

What were the reasons leading to the success of the eradication program of smallpox?

A
  1. The variola virus did not mutate or change its surface antigens. This means that the same vaccine could be used everywhere and would be cheaper.
  2. The vaccine was made from a harmless strain of a similar virus and was effective because it was a live vaccine.
  3. The vaccine could be kept at high temperatures for long periods of time.
  4. Infected people were easy to identify.
  5. The vaccine was easy to administer.
  6. The virus did not linger in the body after an infection to become active later.
  7. The virus did not affect animals making it easier to break the transmission cycle.
  8. Many youngsters spread information about the program.
57
Q

What are autoimmune diseases?

A

This is when the immune system is stimulated against a body’s own proteins(may include antibodies) due to T cells having T cell receptors complementary to that of self-antigens.

58
Q

What happens in myasthenia gravis?

A

People with MG have helper T cells that are specific for the cell surface receptors for acetylcholine. These cells stimulate a clone of B cells to secrete antibodies that bind to the receptor and block the transmission of impulses from the motor neurones. Muscle fibres absorb the receptor-antibody complexes and destroy them. Without acetylcholine receptors, muscle cells do not receive any stimulation and muscle tissue begins to break down.

59
Q

What are some effective treatments for people with MG?

A
  1. A drug that can inhibit the enzyme in synapses that breaks down acetylcholine. this drug increases concentration of acetylcholine in synapses so its action in stimulating muscle fibres to contract lasts longer.
  2. Surgical removal of the thymus gland to get rid of the site of maturation of helper T cells that stimulate B cells to produce antibodies.
60
Q

What are monoclonal antibodies?

A

They are highly specific and identical antibodies made by identical B cell clones.

61
Q

What is the problem with producing monoclonal antibodies?

A

B cells that divide by mitosis do not produce antibodies.

Plasma cells that secrete antibodies do not divide.

62
Q

What is a hybridoma?

A

A small number of plasma cells secreting a specific antibody were fused with cancer cells(divide indefinitely). The cell produced through this fusion is known as a hybridoma. The hybridoma cells divide by mitosis and secrete antibodies.

63
Q

How can monoclonal antibodies be used in diagnosis?

A
  1. Mabs can be used to detect the position of blood clots in the body. The antibodies are produced by injecting a mouse with human fibrin, the main protein found in blood clots. The mouse makes many plasma cells which are then collected and fused with cancer cells to form hybridomas that secrete the antifibrin antibody. A radioactive chemical is attached to each antibody molecule to make radioactively labelled antibodies. They are then introduced to the person’s blood and bind to any fibrin molecules with which they come into contact.
  2. They can be used to locate cancer cells, which have proteins in the cell surface membrane that differ from normal body cells and can therefore be detected by antibodies.
  3. They can be used to identify a particular strain of a virus or bacterium that is causing an infection.
64
Q

How can Mabs be humanised to prevent an immune response due to being considered as non-self?

A
  1. Altering the genes for the polypeptides of the antibodies so that they code for a human sequence of amino acids
  2. Changing the type and position of the sugar groups that are attached to the heavy chains to the arrangement found in human bodies.
65
Q

How can monoclonal antibodies be used in treatment?

A

▪ Used in cancer therapy by marking cancerous cells for
their destruction or binding to protein produced by T
cells that reduces immune response.
▪ Controls over/inappropriate production of B cells,
preventing leukaemia and autoimmune diseases

Biology (19 decks)

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