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Alevel - Biology > Immunity > Flashcards

Immunity Flashcards

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1
Q

Each type of cell has specific molecules on its surface that identify it. These molecules include proteins and enable the immune system to identify…

A
  1. Pathogens
  2. Cells from other organisms of the same species
  3. Abnormal body cells
  4. Toxins
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2
Q

What’s a pathogen

A

Microorganism that causes disease

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3
Q

How does disease spread?

A
  1. Direct contact / exchange of bodily fluids (sharing needles/sex)
  2. Water / food
  3. Droplet (cough/sneeze) 4. Vectors (mosquitos)
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4
Q

What’s a pathogen

A

Microorganism that causes disease

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5
Q

How do pathogens cause disease?

A
  1. Secrete toxins - products of their metabolism
  2. Destroys cells - host tissue / host cells
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6
Q

5 main types of pathogens

A
  1. Bacteria
  2. Fungi
  3. Viruses
  4. Prostits
  5. Parasites
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7
Q

Responses to pathogens

A
  1. Prevents entry of pathogens
  2. Swelling and redness - non-specific response
  3. Specifc immune response (antibody production)
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8
Q

Antigen

A

Substance (usually a protein) not normally found in the hosts body, that stimulates the production of complimentary antibodies.

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9
Q

effect of antigen variability on disease and disease prevention

A

Antigenic variation not only enables the pathogen to avoid the immune response in its current host, but also allows re-infection of previously infected hosts as it has had a change in structure so the same antibodies that were used too combat the antigen originally cant be sued as the tertiary structure has changed.

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10
Q

Phagocytosis steps

A
  1. Phagocyte approaches bacterium. If bacteria is recognised as non-self (foreign), it’s engulfed
  2. Bacteria has been engulfed and and its taken in by a phagysome (bag with membrane around it)
    and it’s surrounded by lysosomes (sacks of digestive enzymes)
  3. A phagolyosome is formed as the lysosome is fused with the phagosiome
  4. Digestive enzymes hydrolyse the bacterium to the extent that its dead
  5. Exocytosis of the products of phagocytosis
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11
Q

Humoral response

A

B-cells
Antibodies

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12
Q

Cell mediated response

A

T-cells

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13
Q

B lymphocytes

A

Mature in the bone marrow
Secrete antibodies into the blood

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14
Q

T lymphocytes

A

Mature in the thymus gland
Do not secrete antibodies

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15
Q

How do antigen presenting cells occur?

A
  1. Pathogen gets in
  2. Engulfed by phagocyte
  3. Antigens from the hydrolysed pathogen then presented on the cell that now has immunity
  4. Activation of the T helper cells
  5. The cells activated 2 different systems
    - cell mediated, done by T-killer cells, whole cell attacks pathogen, can inject toxins, produce T memory cells
    - humoral, antibody mediated, select a clone of B cells, plasma cells produce lots of antibodies and memory cells produced
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16
Q

Humoral immunity - explain

A
  1. The surface antigens of the invading pathogen are taken up by B cells.
  2. The B cell process the antigens and present them on their surfaces.
  3. T helper cells attach to the processed antigens on the B cells thereby activating them.
  4. The B cells are now activated to divide by mitosis to give a clone of plasma cells.
  5. The cloned plasma cells produce antibodies that exactly fit the antigens on the pathogen.
  6. The antibodies attach to antigens on the pathogen and destroy them. This is the primary immune response.
  7. Some B cells develop into memory cells. These can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies. This is the secondary immune response.
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17
Q

What are plasma cells

A

Cells that secrete antibodies directly into the blood plasma.
Primary immune response

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18
Q

What are memory cells?

A

Provide Long term immunity against a specific pathogen by remembering the antibodies used to destroy it the first time.
Secondary immune response

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19
Q

Monoclonal antibodies - how are they made in the body?

A

B-cells dividing by mitosis

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20
Q

Cell mediated response - explained

A
  1. Pathogens invade body cells or are taken in by phagocytes.
  2. The phagocyte places antigens from the pathogen on its cell surface membrane
  3. Receptors on a specific helper T cell (TH) fit exactly onto the antigens.
  4. This T cell is now activated and begins to divide rapidly by mitosis to form a large clone of identical cells.
  5. The cloned T cells:
    - Develop into memory cells that enable a rapid response to future infections by the same pathogens (memory T cells)
    - Stimulate phagocytes to engulf pathogens by phagocytosis (helper T cells or TH cells) stimulate the B cells to divide by mitosis (helper T cells)
    - Helper T cells stimulate cytotoxic T cells (TC cells) to kill infected cells
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21
Q

Advantage of having antigen presenting cells?

A

The functioning of both cytotoxic and helper T cells is dependent on APCs. Antigen presentation allows for specificity of adaptive immunity and can contribute to immune responses against both intracellular and extracellular pathogens.

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22
Q

How do T killer cells kill pathogens?

A

They produce a protein (perforin) that makes holes in the cell surface membrane, so it becomes freely permeable so dies.

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23
Q

How effective are T-killer cells in the immune response for viruses?

A

Very effective as viruses live inside cells and need living cells to reproduce, the sacrificing of body cells prevents them from multiplying and infecting a larger number of cells.

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24
Q

What is an antibody?

A

A protein made by a B lymphocyte in response to a [articular antigen.
Antigen-antibody complex formed as they’re complimentary.

25
Q

Antibody structure

A

Has 2 antibody binding sites that are variable.
Has a constant region
Made up of 2 types of polypeptide chains (2 heavy chains, 2 light chains = 4 total) that are held together by disulfide bonds.
Has a quaternary structure
Has a hinged region.

26
Q

How is the structure of an antibody’s bonding site specific to 1 pathogen?

A

An antigen and an antibody have complementary molecular shapes, complementary specific tertiary structures meaning that they can fit precisely into eachother due to specific sequence of amino acids.

27
Q

Advantage of hinged region in antibody

A

Provides flexibility which is essential for the function of antibodies - more chance to fit antigen

28
Q

Primary immune response

A

After first exposer antibodies and memory cells are made against the antigen.

29
Q

Secondary immune response

A

More rapid with a a higher concentration of antibodies in the blood, as a larger number of plasma cells are produces so a larger number of antibodies are secretes

30
Q

Why do you not often show symptoms upon secondary exposure?

A

Body able to destroy pathogen more rapidly by producing high amount of antibodies.
Less toxins produces / cells are damaged

31
Q

What are viruses able to do (infection of a person twice)

A

Mutate - change their antigen structure so antigens initially produces on primary / previous exposers arent complimentary to virus so new antibodies must be made.

32
Q

Advantages of antigen-antibody complexes - how do they occur?

A

Antigen and antibody are complementary - fit into each other when they collide.

Antigen-antibody complexes are able to clump together (agglutination) so its easier for phagocytosis to occur as they’re able to engulfed and tracked more easily if they’re immobilised.

33
Q

What’s passive immunity?

A

Introduction of antibodies into the body that have been made elsewhere.

Eg. Anti-toxins / antibodies from mother to foetus

34
Q

What’s active immunity?

A

Stimulating of production of antibodies within the body.

Eg. B-cells

35
Q

What are the 2 types of active immunity?

A

Natural - exposure to antigens

Artificial - vaccines

36
Q

What are the 2 types of passive immunity?

A

Natural - placenta / breast milk

Active - inject antibodies (snake anti-venom)

37
Q

Compare and contrast active and passive immunity

A

Active - long term
Passive - short term as immune system not stimulated

Active - not instant
Passive - instant

Active - stimulates immune system, produced internally
Passive - immune system not required as antibodies produces externally

Both aim to get rid of the pathogen
Both types of immunity

38
Q

What is herd immunity?

A

When a significant proportion of the population is vaccinated so have immunity against a virus so provide protection for the individuals who aren’t vaccinated or haven’t got immunity.

Spread of disease stooped as it cant infect people so cant replicate itself.

39
Q

Why is herd immunity needed for the population?

A

Protects groups of people that aren’t able to be vaccinated.
Eg. Young children / people with immune problems

40
Q

What are monoclonal antibodies

A

Antibodies that all have the same shape and tertiary structure and only bind to a specific antigen.

41
Q

How are monoclonal antibodies formed?

A
  1. Mouse exposed to pathogen
  2. B-cells in the mouse produce antibodies which are extracted from the mouse
  3. Antibodies joined to a tumour cell as they’re able to divide out the body and contain the antibody
  4. Detergent added to the mitre to break down the cell surface membranes and allow the cells to enable them to fuse together
  5. The fused cells are separated under a microscope and each cell is cultured to from clones and each clone can be tested to make sure its producing the antibody.
  6. Cloned cells can be grown on a large scale
42
Q

What can monoclonal antibodies be used for?

A
  1. Separate chemicals from mixtures
  2. Injected into somebody in the initial stages of a particular infection, providing them with a large number of antibodies
  3. Used in transplant surgery - reduce the effect of the T-cells on the new tissue / organ / cells
  4. Immunotherapy - targets specific cells by carrying medication / toxin to kill or treat a certain group / type of cells
  5. Pregnancy tests
43
Q

How does immunotherapy work for cancer?

A

Monoclonal antibody bound to a toxic substance.
The antibody will only attach to cancer cells as they are the only cell that is complementary to the antibodies tertiary structure.

44
Q

How do pregnancy tests work?

A

A pregnant woman produces HCG so when a pregnant woman urinates on a pregnancy test strip:

  1. Reaction site - free antibody traps the HCG and a dye enzyme is present
  2. Test site - fixed antibody traps the HCG and there is a dye substrate - colour change is HCG present
  3. Control site - fixed antibodies trap the free antibodies and there is a dye substrate - colour change is test valid.
45
Q

How are monoclonal antibodies used in diagnosis?

A

Pregnancy tests

A fluorescent dye can be added to a monoclonal antibody. A build up of dye in an area of the body can indicate a problem.

46
Q

Ethical issues of monoclonal antibodies / vaccines

A
  1. Production involves mice - suffering of animals
  2. Testing drugs in human volunteers is dangerous - can suffer organ failure
  3. Sometimes long term effects are unknown
  4. Monoclonal antibodies / vaccines have been used too treat a number of diseases increase people QOL and saving their lives
47
Q

What is the ELISA test?

A

Enzyme linked immunosorbant assay

Used to diagnose diseases / conditions - they’re quick and reliable

48
Q

How does the ELISA test work?

A
  1. Antigens are isolated and attached to the base of a well in a test dish
  2. A sample of the blood plasma under test is added to the well. If antibodies are present, they will attach to the antigens. The well is washed to move and blood plasma. If antibodies preset in blood plasma they should remain attached to antigen.
  3. Indicator solution added
  4. Second antibody with enzyme attached is put into the well - specific to antibody. The well is washed throughly to remove unattached antibody.
  5. Solution added - colour change if enzyme present in the well = positive test.
49
Q

Why is it important to wash away all unattached antibodies in the ELISA test

A

Because them a false positive will be produced

50
Q

Why are antibodies not effective against viruses?

A

Because viruses are not living so can’t interfere With the virus is metabolism, stop cell wall synthesis, stock proteins being made at the ribosomes because viruses are not cells so they don’t have a cell structure nor their own metabolism

51
Q

How does HIV Infection occur?

A
  1. Enters the body
  2. Seeks out T helper cells due to particular CD4 receptors
  3. Attaches via attachment protiens as the attachment proteins are complementary to the CD4 protiens
  4. Virus enters (endocytosis)
  5. Makes DNA from RNA (reverse transcriptase)
  6. DNA is incorporated into the cells DNA
  7. Viral protiens are made (eg. Capsid)
  8. Viral particles are assembled
  9. Burst out and look for other CD4 cells on T helper cells
52
Q

How does HIV cause disease?

A

Enters the bloodstream when body fluids mix.
Eg. sexual intercourse, blood transfusion, sharing needles, placenta from mother to foetus

53
Q

How does HIV cause the symptoms of AIDS

A

Symptoms of AIDS are caused by the deterioration of the immune system and the decline of CD4+ T cells.

HIV destroys these cells.

54
Q

HIV capsid

A

HIV’s core that contains HIV RNA

55
Q

HIV envelope

A

Outer surface of HIV

56
Q

HIV enzymes

A

Proteins that carry out the steps in HIV life cycle

57
Q

HIV glycoproteins

A

Protein spikes embedded in the HIV envelope

58
Q

HIV RNA

A

HIV’s genetic material

Alevel - Biology (5 decks)

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