Y12 MS - Immunity Flashcards

1
Q

What is an antigen?

A

A molecule which triggers an immune response

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2
Q

What is an antibody?

A

A protein produced by lymphocytes in response to the presence of specific antigens

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3
Q

What is a pathogen?

A

A microorganism which causes disease

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4
Q

What is immunity?

A

When the body is resistant to a disease

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5
Q

What is an immune response?

A

The production of antibodies against specific antigens of a pathogen

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6
Q

What are self cells?

A

The body’s own cells

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7
Q

What are non-self cells?

A

Cells not from the body (may be from a pathogen, cancer or transport)

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8
Q

What are toxins?

A

The waste products released by pathogens

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9
Q

What kind of response is phagocytosis?

A

Non specific

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10
Q

What is the process of phagocytosis?

A

Phagocytes are white blood cells found in the blood and tissues
Chemical products released by abnormal cells attract them
The receptor binding points on the cell surface attach to the antigen. The phagocyte then changes shape to engulf the pathogen
Once the pathogen is engulfed it is held within a phagosome vesicle which will then fuse with a lysosome
The lysosome releases its contents and the lysozymes hydrolyse the pathogen, destroying it
Soluble products are absorbed and used by the phagocyte

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11
Q

Where are phagocytes produced?

A

The bone marrow

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12
Q

What types of molecules can be antigenic?

A

Proteins
Polysaccharides
Glycoproteins

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13
Q

Why does antigenic variability occur?

A

The shape of antigens frequently alter due to mutations which change the tertiary structure

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14
Q

Does the cellular response involve T lymphocytes or B lymphocytes?

A

T lymphocytes

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15
Q

Does the humoral response involve T lymphocytes or B lymphocytes?

A

B lymphocytes

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16
Q

What is exocytosis?

A

The release of contents from a cell

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17
Q

What is the process of the cell mediated response?

A

Pathogens which invade body cells are destroyed through phagocytosis. The phagocyte presents the antigens from the pathogen on its cell surface
T lymphocytes are activated when they bind to the specific antigen presented on the cell surface and produce cytokines to stimulate rapid cell division by mitosis
Cloned T cells can differentiate into cytotoxic cells which produce perforin, a protein which makes holes in infected cell membranes so they become permeable and die
Cloned T cells can also stimulate B cells to divide by mitosis and secrete antibodies, stimulate phagocytosis and differentiate into memory cells for a more rapid future response

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18
Q

What is the process of the humoral response?

A

A pathogen invades the body with a specific antigen. B cells recognise the antigen and small numbers with complementary antibodies bind to them
When T lymphocytes bind to the antigen of a pathogen presented on the cell surface of a phagocyte, rapid division of B cells by mitosis to form clones which produce the correct antibody
These clones of B cells can differentiate into either plasma cells which can secrete complementary antibodies to destroy the pathogen or memory cells which circulate in the blood and tissue fluid. If the pathogen invades the body again, a rapid response is made as memory cells can divide and develop into plasma cells and more memory cells

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19
Q

What does 1 show?

20
Q

What do 2 and 3 show?

21
Q

What does 5 show?

22
Q

What does 4 show?

23
Q

What is a vaccination?

A

When a dead or weakened pathogen is introduce to induce an immune response where memory cells are produced so that future infection by the same pathogen produces a more immediate immune response

24
Q

What is the structure of an antibody?

A

An antibody has a quaternary structure with two heavy polypeptide chains bonded to two light chains by disulphide bonds

25
Q

How do antibodies help destroy pathogens in the body?

A

When an antibody collides with a cell with non-self complementary antigens, an antigen-antibody complex is formed
As antibodies have two antigen-binding sites they can bind to more than one pathogen at a time, causing agglutination where groups of pathogens become clumped together
This attracts phagocytes to engulf and destroy the pathogens

26
Q

What type of cells does the cell mediated response involve?

27
Q

What type of cells does the humoral response involve?

28
Q

Following cloning by mitosis, what can B cells differentiate into?

A

Memory cells or plasma cells

29
Q

Following cloning by mitosis, what can T cells differentiate into?

A

Cytotoxic cells

30
Q

Describe a secondary immune response

A

When the antigen enters the body a second time, the memory cells produced from the initial immune response quickly divide to produce more plasma cells. These plasma cells secrete antibodies complementary to the antigen

31
Q

What is antigenic variation?

A

Where a pathogen may mutate mutate frequently so its antigens change suddenly and vaccines become ineffective against it because the antigen are no longer recognised by the immune system

32
Q

What is herd immunity?

A

When a sufficiently large proportion of the population has been vaccinated and are therefore immune so it is more difficult for the pathogen to spread

33
Q

Why may vaccinations be ineffective?

A

Antigenic variation
Symptoms may be hard to diagnose or trace

34
Q

What is active immunity?

A

When an antigen enters the body and triggers a specific immune response, producing antibodies as a result

Can be naturally acquired through exposure to microbes or artificial through a vaccination

35
Q

What is passive immunity?

A

Immunity without an immune response so no antibodies produced by the body

Can be acquired naturally by antibodies received from another organism such as via the placenta or artificially with antibodies manufactured and injected into an organism e.g monoclonal antibodies

36
Q

What is the structure of HIV?

A

HIV is made up of two RNA strands, proteins (e.g reverse transcriptase), a capsid, attachment proteins and viral envelope consisting of a lipid bilayer and glycoproteins

37
Q

HIV is a ——

A

Retrovirus

38
Q

What is HIV transmitted by?

A

The direct exchange of bodily fluids such as from mother to child by breastmilk, blood donation or sharing needles

39
Q

How does HIV replicate?

A

When HIV enters the bloodstream, it attaches its receptors onto a T cell and injects its genetic material into the cell
The HIV uses the cellular machinery to replicate itself as the viral reverse transcriptase produces DNA from the RNA of HIV so each time the cell divides, the viral genetic information is copied
After many copies are made, the host cell is destroyed by the HIV

40
Q

How does HIV lead to the inability of the immune system to respond to infection

A

By HIV replication, T cells are destroyed meaning there is a decreased lymphocyte number. Therefore, there is reduced ability to produce antibodies against pathogens

41
Q

How are monoclonal antibodies produced?

A

A mouse is immunised with a specific antigen and an immune response is triggered
the spleen cells are extracted from the mouse where some B cells will be producing antibodies against the antigen
B cells from the mouse and cancerous B cells which divide rapidly and indefinitely are fused with the addition of detergent to disrupt the phospholipid bilayer. This produces hybridoma cells
The cells are then placed in a culture medium where only fused cells can grow
The hybridoma cells are separated and tested for required antibody production. They are then allowed to multiply and the antibodies are collected and purified for use e.g cancer treatments, pregnancy tests

42
Q

What are the uses of monoclonal antibodies?

A

Diagnostically
Pregnancy tests
Detecting cancer cells

Therapeutically
Targeted breast cancer treatment
Preventing blood clotting

43
Q

What is an ELISA test and what are the two types?

A

The ELISA test is used to see whether a patient has any antibodies to a specific antigen or any antigens to a specific antibody

These can be direct (using a single antibody) or indirect (using two antibodies)

44
Q

Describe an indirect ELISA test

A

Indirect tests for specific antibodies e.g for HIV

First the HIV antigens are bound to the bottom of a reaction vessel
A blood plasma sample is taken from the patient and added to the sample
Any HIV specific antibodies present in the sample bind to the antigens
Any other antibodies which are unbound are washed away
A second type of antibody with an enzyme attached to it is added to the reaction vessel
These secondary antibodies bind to the primary antibodies and the reaction vessel is washed again to remove any unbound antibodies
A solution containing a substrate which reacts with the enzyme attached to the secondary antibodies is added. If the secondary antibodies are present, there is a colour change indicating the patient has the HIV antibodies in their blood

45
Q

Describe a direct ELISA test

A

A direct ELISA test can be used to test whether a patient has specific antigens in their blood plasma e.g for prostate cancer

The antibodies specific to the prostate cancer antigens are bound to the bottom of the reaction vessel
The patient blood plasma sample is added and if present, the prostate cancer antigens bind to the primary antibody. The vessel is then washed
A secondary antibody with an enzyme attached is added and will only bind if the prostate cancer antigens are present
A solution containing the substrate complementary to the enzyme attached to the secondary antibody is added and if a colour change is present, the prostate cancer antigens are present