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Immune system Flashcards

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1
Q

What is a pathogen?

A

A microorganism that can cause disease.

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2
Q

What is an infectious pathogen?

A

One that can spread from one organism to another.
(They cause communicable diseases).

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3
Q

Can you name so infectious pathogens?

A

Bacteria, Fungi, Viruses.

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4
Q

What is transmission?

A

The passing of a pathogen from one organism to another.

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5
Q

When does disease occur?

A

When infection leads to recognisable symptoms in the host.

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6
Q

What are the two groups of defence mechanisms?

A

Specific and non-specific.

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7
Q

What is a non-specific defence mechanism?

A

A response which is immediate and the same for all pathogens.

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8
Q

What is a specific defence mechanism?

A

A slower response that is specific to each pathogen.

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9
Q

Can you give some examples of non-specific defence mechanisms?

A

Phagocytosis.
Physical barriers:
-Skin.
-Mucus lining of the trachea.
-Stomach acid.

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10
Q

Can you give some examples of specific defence mechanisms?

A

-Cell-mediated response: T-Cells.
-Humoral response: B-Cells.

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11
Q

What is phagocytosis?

A

The engulfment and destruction of microorganisms by phagocytes.

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12
Q

Can you explain the process of phagocytosis?

A

1- The phagocyte detects a pathogen by the chemicals it releases and moves towards it.
2- The phagocyte extends around the pathogen and engulfs it.
3- A phagosome is formed around the pathogen inside the phagocyte from the phagocyte’s cell membrane.
4- Lysosomes move towards and fuse with the phagosome.
5- The lysosomes release lysozymes (hydrolytic enzymes) into the phagosome which hydrolyse the pathogen.
6- Digestable products are absorbed by the phagosome and the pathogen’s antigens are represented on the phagocytes surface (making it an antigen-presenting cell).
7- Indigestible products are discharged from the phagocyte.

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13
Q

What is an antigen presenting cell?

A

A cell which embeds the antigens of a pathogen in its cell-surface membrane.

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14
Q

Why is phagocytosis beneficial?

A

It destroys unwanted cells found in the blood and other tissues, therefore reducing the spread of the unwanted cells to other parts of the organism.

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15
Q

What are the differences between non-specific and specific defence mechanisms?

A
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16
Q

What does the immune system detect?

A

Pathogens, abnormal cells, toxins, non-self cells, antigen-presenting cells.

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17
Q

What do specific defence mechanisms involve?

A
  • The activation of B lymphocytes (humoral).
  • The activation of T lymphocytes (cellular).
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18
Q

What is an antigen?

A

A protein or glycoprotein found on the surface of all cells.
It can also be present as a free molecule.

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19
Q

What do antigens stimulate?

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A

They stimulate an immune response.
For example, they stimulate B lymphocytes to produce and release antibodies specific to the antigen.

20
Q

What is antigenic variation?

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A

Antigens of a pathogen may change due to a mutation. Pathogen species with a high mutation rate will more likely end up with varied antigens.
This results in multiple strains of a pathogen.

21
Q

Why is antigenic variation a problem for potential hosts?

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A

The host may be immune to one strain of the pathogen but not to another as the antibodies previously produced won’t be complimentary to the new antigen and the memory B cells won’t recognise the new antigen. This means the immune system has to coordinate a primary immune response again.

22
Q

What produces antibodies?

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A

B lymphocytes (specifically plasma cells).

23
Q

What type of molecule are antibodies?

24
Q

Where are antibodies found?

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A

In blood plasma, tissue fluids, and breast milk.

25
What is the basic structure of an antibody?
4 polypeptide chains (2 light chains and 2 heavy chains) joined together by disulfide bonds.
26
What are the regions of an antibody?
The variable region and the constant region.
27
What is the constant region of an antibody?
Where the sequence of amino acids in the polypeptide chains is the same for all antibodies.
28
What is the variable region of an antibody?
The part of the polypeptide chains that have different amino acid sequences to other antibodies. The variable region of an antibody forms two antigen-binding sites.
29
What is the antigen binding site?
The area of the antibody that has a specific tertiary structure which is complimentary to the structure of the antigen it binds to. This is where the antigen-antibody complex is formed.
30
What is the role of antibodies?
To aid in the destruction of unwanted cells or toxins in the body.
31
What processes do antibodies stimulate and how?
They form an antibody-antigen complex which can stimulate agglutination or phagocytosis of the antigen/the antibody is bound to.
32
Can you describe the humoral response?
1- B cells secrete small small amounts of their specific antibody onto their cell-surface membrane. 2- A specific antigen may bind to the complimentary antibody on a B cell. 3- These B cells are stimulated to divide by mitosis. This is clonal selection. 4- Helper T cells have to activate the B cells to divide. 5- Mitosis results in a clone of identical plasma cells. 6-The plasma cells will all produce the same specific antibody and secrete it into the blood plasma. 7- These antibodies bind to the specific antigen, forming an antigen-antibody complex. 8- This stimulates processes leading to the destruction of the antigen/unwanted cell. 9- Some of the plasma cells are stimulated to differentiate into memory B cells.
33
Can you describe clonal selection?
1- The antigen enters the blood stream 2- The B cell secretes a small amount of antibodies onto its surface. 3- If the B cell comes across the antigen and has the specific, complimentary antibody, it will bind to this antigen to form an antigen-antibody complex. 4- The B cell engulfs the complex by endocytosis and separates the complex inside itself. 5- The B cell then embeds the antigen on its cell-surface membrane. This B cell is now an antigen-presenting cell. 6- The helper T cell with a receptor complimentary to the antigen will bind to the specific antigen on the B cell. This activates the helper T cell. This also stimulates the B cell to undergo clonal expansion and differentiation.
34
Can you describe the cellular response?
1- A pathogen enters the blood stream. 2- The phagocyte engulfs the pathogen and performs phagocytosis on it. 3- The helper T cell with the complimentary protein receptor will bind to the antigen. 4- This stimulates the helper T cell to divide by mitosis and form a clone of genetically identical T cells. 5- The helper T cells are activated. 6- The cloned T cells: - Activate cytotoxic T cells. - Develop into more helper T cells which stimulate B cells to divide and secrete antibodies. - Develop into memory T cells. - Stimulate phagocytes to perform more phagocytosis.
35
What is clonal expansion?
The process of rapid cell division resulting in a clone of genetically identical cells from a single parent cell.
36
Do T cells produce or release antibodies?
No.
37
What do memory T cells do?
Provide a rapid immune response, coordinate a secondary response, to a past infection.
38
What do memory B cells do?
Undergo mitosis and release specific antibodies as plasma cells when a past infection returns.
39
What iss thee primary immune response?
40
What is the secondary immune response?
41
What is herd immunity?
42
What is the ELISA test?
43
What is the difference between a direct and an indirect ELISA test?
44
What are the methods for indirect AND direct ELISA tests?
45
What is a vaccine?
46
What is the method for making monoclonal antibodies?
47
What is a monoclonal antibody?

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