Immune system:

Question 1

Whats the immune system?

Answer 1

The immune system is a group of cells, tissues, organs and mechanisms that defend an organism against pathogens and other foreign substances.

Question 2

Define pathogen:

Answer 2

A disease causing microorganism

Question 3

Whats an immune response?

Answer 3

An immune response is a complex series of specific and non-specific processes involving a range of cells and chemicals.

If the body successfully fights an infection, it will respond more quickly and effectively if the same pathogen is re-encountered.

Question 4

Whats a non specific immune response?

Answer 4

The non-specific response quickly targets a wide range of pathogens and foreign substances.

Phagocytosis, inflammation and the antimicrobial proteins lysozyme and interferons are all part of this immune response.

Question 5

Whats a lysozyme?

Answer 5

Lysozyme is an enzyme that disrupts the cell walls of gram-positive bacteria by digesting the peptidoglycan. It is found in human tears, saliva and lysosomes.

Question 6

Whats an interferon?

Answer 6

Interferons are proteins produced by virus-infected body cells in response to the virus. Interferons trigger the production of a second protein that inhibits viral replication by binding to mRNA coded by the virus.

Question 7

What are the two main groups of white blood cell?

Answer 7

PHAGOCYTES & LYMPHOCYTES

Question 8

What do phagocytes do?

Answer 8

Phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens or toxins.

They then either:
-ingest and absorb the pathogens or toxins
-release an enzyme to destroy them
Having absorbed a pathogen, the phagocytes may also send out chemical messages that help nearby lymphocytes to identify the type of antibody needed to neutralise them.

Question 9

What do lymphocytes do?

Answer 9

Pathogens have chemicals on their surface that are called antigens.
Each lymphocyte carries a specific type of antibody - a protein that has a chemical ‘fit’ to a certain antigen.
When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen.

Question 10

Antibodies (from lymphocytes) neutralise pathogens in a number of ways which are…

Answer 10

1) they bind to pathogens to destroy them
2) they coat pathogens, clumping them together so that they are easily ingested by phagocytes
3) they bind to the pathogens and release chemical signals to attract more phagocytes

Lymphocytes may also release antitoxins that stick to the appropriate toxin and stop it damaging the body.

Question 11

What a leucocyte ?

Answer 11

a white blood cell

Question 12

What are the different granulocytes?

Answer 12

Basophil, neutrophil and eosinophil.

Question 13

Whats an example of phagocyte?

Answer 13

Monocytes -> macrophages

Question 14

Whats a natural barrier do?

Answer 14

Natural barriers reduce the chance of infection:

Question 15

Examples of natural barriers- the first barriers:

Answer 15

• the skin
• blood clotting to seal wounds
• inflammation to localise breaks in the barrier
• phagocytosis to destroy invading microbes
• ciliated mucous membranes that trap microbes in inhaled air
• Lysozyme in tears, saliva and stomach acid that kills bacteria.

Question 16

What happens in phagocytosis?

Answer 16

White blood cell moves around bacterium and engulfs it.

Question 17

Whats specific immune response:

Answer 17

The specific immune response can target a specific pathogen, although it is slower to act than the non-specific response.

It features two main types of response to pathogens:

1) Cellular or cell mediated
2) humoral response

Question 18

Whats primary response?

Answer 18

when you first get into contact with a microbe/cancer/vaccine.

Question 19

Whats secondary response?

Answer 19

The secondary immune response occurs the second time (or 3rd, 4th, etc.) the person is exposed to the same antigen. At this point immunological memory has been established and the immune system can start making antibodies immediately.

Question 20

Describe Cell-mediated immune response?

Answer 20

T cells recognize infected cells by interacting with antigens present on their molecules, but before a T cell can do so, it must be activated via interaction with an antigen presenting cell.

Once a cytotoxic T cell (TC cells) is activated, it will clone itself, producing many TC cells with the correct receptors. Some of these cells are active and will help destroy infected cells, while others are inactive memory cells that will create more active TC cells if the infection returns.

Helper T cells (TH cells) also aid in the cell-mediated immune response by releasing signalling molecules known as cytokines which can recruit natural killer cells and phagocytes to destroy infected cells and further activate TC cells. TH cells do not directly destroy pathogens.

Question 21

Whats an antigen?

Answer 21

proteins or parts of proteins that the human body recognises as ‘foreign’. Antibody’s are generated in response to Antigens

Question 22

Whats an antibody?

Answer 22

Antibodies are proteins that are highly specific for a certain Antigen. Once they are bound they don’t come off and can cause many different effects to the organism the antigen is part of.

Question 23

Describe humoral response

Answer 23

B lymphocytes have receptors for the detection of its specific antigen;

activation stimulates production of plasma cells, and memory cells;

memory cells remain in the circulation ready to divide if the same antigen is encountered again.

When the antigen is encountered again, many copies of the antibody are produced, which bind to the antigen.

Antibodies are proteins which are specific to a certain antigen with which they bind to form an antigen - antibody complex.

An antigen-antibody complex renders the antigen inactive which increases the rate of engulfment by phagocytes.

Question 24

What’s a cytotoxic t cell

Answer 24

a subgroup of lymphocytes (white blood cells) that are capable of inducing death to infected or tumour cells

Question 25

Define cytokine

Answer 25

any of the various small regulatory proteins that regulate the cells of the immune system

Question 26

Whats the two types of lymphocyte?

Answer 26

T cells and B cells

once they mature, they migrate to our lymph nodes to await infection

Question 27

Where are b cells made

Answer 27

Bone marrow

Question 28

Where are t cells made?

Answer 28

made in bone marrow but mature in the Thymus