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B = Biological Molecules & Cells = > Immune System > Flashcards

Immune System Flashcards

1
Q

What is an antigen?

A

A PROTEIN in the cell-surface membrane that triggers an IMMUNE RESPONSE.

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2
Q

Describe the process of how phagocytes destroy pathogens?

A

1) Pathogen releases chemicals called chemoattractants which attract phagocytes which moves along the concentration gradient
2) The pathogen is ENGULFED in a vesicle called a PHAGOSOME
3) The phagosome membrane FUSES with the membrane of the lysosomes in the phagocyte
4) Lysosome contains hydrolytic enzymes, lysozymes which are released into phagosome
5) Lysozymes hydrolyse the molecules the pathogen is made of
6) Soluble products of breakdown are absorbed into cytoplasm (e.g. glucose, amino acids, antigens)
7) Non-soluble products expelled out of the cell

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3
Q

What is a chemoattractant? Where is it produced?

A

Chemical that attracts pathogens

In the pathogen itself, or the cells affected by pathogens.

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4
Q

What is an example of a chemoattractant?

A

Cytokines

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5
Q

What are phagocytes?

A

Cells which engulf pathogens, or cells that are infected, damaged, or dying.

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6
Q

What do phagocytes include?

A

Macrophages

Dendritic cells

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7
Q

What are antigen presenting cells (APC)?

A

Cells that have engulfed a pathogen and presented it’s antigens on the surface membrane.

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8
Q

How are T cells activated?

A

When the receptor cells bind to complementary antigens on the surface of phagocytes that have presented them.

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9
Q

Outline the process of the cell-mediated response [6 marks]

A

1) Phagocyte engulfs pathogen - presents antigens on cell surface membrane = APC
2) Specific Helper T-cells with RECEPTORS complementary to the specific antigen BIND to the APC. The TH cells become ACTIVATED
3) The activated TH cells divide by mitosis (clonal selection)
> They also secrete chemicals which activate other T-cells and B-cells which have the same receptors.
> T helper cells divide by mitosis. T helper cells…

4)
> Activates Killer T cells / Cytotoxic T-Cells (TC) are stimulated –> Produces chemicals which make the APC’s membrane permeable - the holes also allow toxins to get in, which kills the cell and everything in it (e.g. viruses that invaded)

> B-cells are stimulated

> Stimulate phagocytosis by phagocytes

> Become T-memory cells

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10
Q

What can occur after Helper-T cells divide by mitosis in the cell-mediated response?

A

1) Cytotoxic T-Cells are stimulated –> Produces chemicals which make the APC’s membrane permeable which can kill the cell. The holes also allow toxins to get in, which kills the cell and everything in it (e.g. viruses that invaded)

2) B-cells are stimulated

3) Stimulate phagocytosis by phagocytes

4) Form T-memory cells

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11
Q

Give 2 differences between specific and nonspecific immune responses [4 marks]

A

Nonspecific =
> immediate response to all pathogens
> physical barriers (e.g. skin) and phagocytes

Specific =
> time lag - slower and specific to each pathogen
> includes cell-mediated response (T lymphocytes) & humoral response (B lymphocytes)

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12
Q

Name the 2 types of specific immune response.

A

Cell-mediated response

Humoral response

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13
Q

What kind of cells or molecules stimulate an immune response?

A

1) Pathogens

2) Abnormal cells - (cancer)

3) Foreign cells from other organisms of the same species - transplants

4) Toxins (released by pathogens)

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14
Q

What is another name for lymphocytes?

A

T cells

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15
Q

What are T cells / lymphocytes?

A

> WBCs involved In specific immune response - in cell-mediated response

> Made in bone marrow but T cells mature in thymus.

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16
Q

What will T-lymphocytes respond to?

A

Antigens of a pathogen attached to an APC

T cells will NOT respond to antigens directly still attached to a pathogen,
only antigens that have gone through phagocytosis.

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17
Q

What is an antibody?

A

Protein produced by B plasma cells which binds to a specific complementary antigen.

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18
Q

Describe the structure of an antibody

A

1) Antibodies are proteins with a quaternary structure

2) Made of 4 polypeptide chains…
> 2 heavy chains (large polypeptide chain)
> 2 light chains (small polypeptide chain)

3) The heavy and light polypeptide chains are held by DISULPHIDE bonds

4) Contains VARIABLE regions which form antigen binding sites

5) The rest of the antibody is CONSTANT.

http://www.biology.arizona.edu/immunology/tutorials/antibody/structure.html

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19
Q

Why is the antigen-binding site on an antibody specific to one antigen?

A

> Antibodies have different VARIABLE regions…

…with an antigen-binding site that is COMPLEMENTARY to one specific antigen/toxin produced by a pathogen.

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20
Q

(a) Name the monomer that forms the heavy and light chains in an antibody

(b) Name the chemical bonds that join these monomers [2 marks]

A

(a) Amino acids

(b) Peptide bonds

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21
Q

The specificity of an antibody depends on the variable regions.
Explain how [3 marks]

A

Variable regions have different sequence of amino acids (primary structure) [1]

Affects tertiary structure [1]

Only a specific antigen can bind [1]

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22
Q

What is the role of antibodies?

A

1) They form antibody-antigen complexes.

2) Neutralises toxins released by pathogens

3) Antibodies do not destroy pathogens DIRECTLY.

Antibodies & substances released from Helper T cells activate the B cell.
This is called clonal selection. The activated B cell divides into plasma cells.

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23
Q

What do plasma cells do?

A

Produce antibodies with a complementary shape to the antigen.

24
Q

What are monoclonal antibodies?

A

Antibodies that come from the same CLONE of plasma cells…and have the same TERTIARY STRUCTURE and specific to ONE antigen.

25
Q

What is meant by agglutination?

A

The clumping of pathogens in the presence of their complementary antibody

This allows phagocytes to engulf more pathogens efficiently

(so a group of pathogens crowded together, then phagocytes engulf them easily)

26
Q

How do antibodies react to toxins produced by pathogens?

A

Neutralises the toxins with anti-toxins

27
Q

How do antibodies react to viruses?

A

Antibodies bind to the ATTACHMENT proteins on a virus to STOP them attaching to host cells.

28
Q

What type of response are antibodies involved with?

A

Humoral response

29
Q

What are lymphocytes also known as?

A

B cells

30
Q

Describe how B-lymphocytes respond when they are stimulated by antigens [4 marks] MS

A

1) Divide by mitosis / forms clones

2) To produce plasma cells

3) The plasma cells make antibodies

4) The plasma cells produce memory cells

31
Q

Describe how antibodies are produced in the body following a viral infection [6 marks]
(humoral response)

A

1) Virus contains antigen and is is engulfed by phagocyte and presents the antigens on its surface = APC

2) T cells with a specific complementary receptor bind to the antigen and are activated.

3) T cells undergo mitosis/differentiation (stimulate macrophages, become cytotoxic T cells/form memory T cells (Store memory of that antigen)

4) Remain T helper cells can also activate B cells

5) B cells divide by mitosis and undergo clonal selection

6) …(and) form plasma cells which produce antibodies (monoclonal)

32
Q

What are monoclonal antibodies?

A

Antigens produced from a single clone of B cells

33
Q

Compare the primary and secondary immune response.

A

Secondary immune response…

> Faster rate of antibody production

> Higher concentration of antibodies produced

> Shorter time lag between exposure & antibody production

> Pathogen usually destroyed before any symptoms

34
Q

What are the reasons for the delay in antibody production after exposure?

A

Antibody production is delayed due to:

1) Time taken for antigen to bind to complementary receptor on B-cell

2) Time taken for B cell to become activated by a TH cell

3) Time taken for B-cell to divide by mitosis to produce plasma cells

4) The plasma cells produce antibodies

35
Q

Explain what occurs during the primary immune response

A

1) Body will produce enough of the right antibodies to overcome the infection.

2) Infected person shows symptoms of the disease

3) T cells and B cells produce memory cells

4) T cells remember the specific antigen and B cells record the specific antibodies to bind to the antigen

5) The person is said to be immune to future infections.

36
Q

Explain what occurs during the secondary immune response

A

1) The primary response caused many clones of B memory cells

2) Causes the B memory cells to quickly form B plasma cells (clonal selection)

3) Plasma cells produce 100’s of more antibodies more quickly

4) Memory T cells are activated and divide into the correct type of T-cells.

5) The pathogen is quickly destroyed before it produces any symptoms.

37
Q

What is active immunity?

A

Involves the production of antibodies by the body itself and the subsequent development of memory cells.

38
Q

What is passive immunity?

A

Results from the acquisition of antibodies from another source and memory cells are not developed.

…could happen from blood transplants, or convalescent antibodies taken from people and put in a drip into other people to help them become immune.

39
Q

What are the 2 types of lymphocytes?

A

B cells - matures in Bone marrow

T cells - matures in the Thymus

40
Q

What is the interaction between B and T cells simply?

A

B cells represent antigens on it’s cell-surface membrane.

T cells with receptors complementary to the antigens bind onto it

The T cell stimulates the B cell causing it to clone itself.

The cloned B cells then differentiate into either…

> A plasma B cell
A memory B cell

Since the T cell helps the B cell clone itself, it’s called a Helper T cell

41
Q

Difference between T and B cells?

A

T cells = cell-mediated response

B cells = humoral response

42
Q

Describe and explain how vaccinations can lead to a protection of people against a disease caused by a pathogen [6 marks]

A

1) A vaccine made from dead/weakened pathogen or antigens is injected.

2) The B cells with complementary receptors bind to the antigen.

3) Activated specific T helper cells activate these B cells.

4) B cells divide by mitosis to produce B-plasma cells

5) The B plasma cells release antibodies, which are complementary to the antigen

6) Some B plasma cells become B memory cells

7) If person is exposed again, B memory cells become active and divide by mitosis to produce B plasma cells, which produce more antibodies more quickly.

8) Antibodies destroy the pathogen before symptoms appear.

9) Vaccinating a large proportion of the population results in the herd immunity - (fewer people pass on the disease, so unvaccinated people are protected)

43
Q

What is meant by the cell-mediated response?

A

Response of T cells to a foreign antigen

44
Q

What is meant by the humoral response?

A

The response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal antibodies.

45
Q

What is herd immunity?

A

When more people are immune, fewer people carry the pathogen, so unvaccinated / susceptible people are less likely to make contact with infected people.

46
Q

Describe how B-lymphocytes respond when they are stimulated by antigens [6 marks]

A

1) A specific B-cell has protein receptors on its surface that are complementary to a specific antigen
2) This specific B cell encounters the antigen on the surface of a pathogen or on the surface of an Antigen Presenting Cell
3) This specific B-cell engulfs and presents the antigens on its own cell surface membrane

4) The receptor of the activated T-helper cell binds to the complementary antigen presented on the cell-surface membrane of the SPECIFIC B-cell

5) This activates B cell to divide by mitosis forming…

> B plasma cells - produce antibodies which circulate the blood and bind to the complementary antigen on the pathogen. Ultimately resulting in the pathogens being killed by agglutination.

> B memory cells - remain in the blood so if the pathogen re-invades, these cells divide by mitosis to make B plasma cells secondary response is much faster

47
Q

What is clonal selection?

A

The activation of a B cell that has a specific protein receptor, which is complementary to a specific antigen.

The activated B cell divides by mitosis to produce genetically identical clones.

They then differentiate into B plasma cells and B memory cells.

48
Q

Why might one type of pathogen cause the activation of more than one type of B cell and more than one type of T cell?

A

1) All cells (including pathogens) have more than 1 type of antigen on their surface.

2) B cells can also be activated by toxins (act as antigens) produced by pathogens

49
Q

What is a primary immune response?

A

A primary immune response occurs the first time an organism comes in contact with a specific pathogen (or antigen).

50
Q

What is a secondary immune response?

A

A secondary immune response occurs when an organism comes into contact with a specific pathogen which it has come into contact with previously

51
Q

What is antigenic variability?

What are the consequences for an organism who encounters a pathogen with antigenic variability?

A

Antigenic variability is when a pathogen has genes which code for the antigen proteins mutate from one generation to the next thus the antigens change from one generation to the next.

The organism will not have B-memory cells with antibodies complementary to the antigens. Therefore the organism will have a new primary immune response and will experience symptoms of the disease.

52
Q

What is antigenic variability?

A

If a pathogen has antigenic variability it means that the genes which code for the antigen proteins mutate from one generation to the next thus the antigens change from one generation to the next.

53
Q

Describe and explain how vaccination can lead to protection or people against bacterially cause diseases

A
  1. A vaccine is made from dead or weakened bacteria or antigens from them.
  2. B cells with complementary receptors bind to the antigen

3.Specific activated T helper cells, active these B cells.

  1. B cells divide by mitosis to produce B-plasma cells.
  2. The B plasma cells release antibodies, which are complementary to the bacterial antigens
  3. Some B plasma cells become B memory cells

7.If the person is exposed again to the antigen or pathogen, the B memory cells become active and divide by mitosis to produce B plasma cells , which produce more antibodies more quickly.

  1. These antibodies lead to the destruction of the pathogen before symptoms appear
  2. Vaccinating a large proportion of the population results in the herd effect (which means that there are fewer people to pass on the disease, so unvaccinated people are protected)
54
Q

What is herd Immunity?

A

When a large proportion of the population is vaccinated so that those who are not vaccinated / susceptible are protected from the disease.

55
Q

Why is herd Immunity important?

A

Protects people in the population who cannot be vaccinated e.g. if they are very old, very young, have a weakened immune system, are taking immunosuppressants etc

56
Q

What are the dangers of vaccines containing inactive form of virus?

A

> Inactive virus may become active

> Virus might become harmful

> Non-pathogenic virus may mutate and harm cells

> Genetic information / protein may harm cells

> People may test positive after vaccine used

> Vaccinated people may develop disease from a different strain to that in the vaccine
This may affect their work / life

B = Biological Molecules & Cells = (26 decks)

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