Specific Cellular Defences

Question 1

What are lymphocytes?

Answer 1

White blood cells involved in the specific immune response(achieved by lymphocytes)

Question 2

What will each lymphocyte respond do?

Answer 2

A specific pathogen
They do this by recognising specific molecules(often proteins) on the surface of invading pathogens called antigens
Antigens are located on the surface of cells and trigger a specific immune response

Question 3

How do lymphocytes recognise specific antigens?

Answer 3

Lymphocytes recognise specific antigens on pathogens as they have a single type of membrane receptor which is specific for one antigen

Question 4

What happens after they bind with the antigen?

Answer 4

On binding with a specific antigen each lymphocyte will undergo repeated cell division to form a clonal population of identical lymphocytes that are all able to respond to the pathogen

Question 5

What at the two types of lymphocytes?

Answer 5

B lymphocytes
T lymphocytes

Question 6

What do B lymphocytes do in response to invading pathogens?

Answer 6

These cells produce antibodies against specific antigens this leads to the destruction of the pathogen
Antibodies are Y shaped proteins with receptor binding sites specific to a particular antigens on a pathogen
Antibodies produced by activated B lymphocytes become bound to antigens, inactivating the pathogen
The resulting antigen antibody complex can then be destroyed by phagocytosis

Question 7

How do B lymphocytes cause allergies?

Answer 7

B lymphocytes can respond to antigens on the substances that are harmless to the body eg pollen
This hypersensitive response is called an allergic reaction

Question 8

What do t lymphocytes do in response to invading pathogens?

Answer 8

They destroy infected body cells by recognising antigens of the pathogen on the cell membrane and inducing apoptosis
Apoptosis is programmed cell death where the cell essentially commits suicide
T lymphocytes recognise antigens of the pathogen on the surface of the cell membrane of the infected cell
T lymphocyte attaches onto infected cells and releases proteins
Proteins diffuse into infected cell causing production of self destructive enzymes which cause cell death
The remains of the cell are removed by phagocytosis

Question 9

How do T lymphocytes cause autoimmune diseases?

Answer 9

T lymphocytes can normally distinguish between self antigens on the body’s own cells and non self antigens on infected cells
If this does not occur(failure of regulation of the immune system) then T lymphocytes can respond to self antigens thus leading to them attacking the body’s own cells
This causes autoimmune disease like type 1 diabetes

Question 10

What do some of the cloned B and T lymphocytes survive as after infection?

Answer 10

Long term memory cells
This means when a secondary exposure to the same antigen occurs, these memory cells quickly produce a new clone of specific lymphocytes
These destroy invading pathogens before the individual shows symptoms and prevents illness as it means that antibodies are produced more quickly in higher concentration and last for longer
(Antibody production greater and more rapid during secondary response compared to primary response)

Question 11

What does the human immunodeficiency virus(HIV) do to T lymphocytes?

Answer 11

HIV attacks and destroys T lymphocytes
This leads to the depletion of T lymphocytes which leads to the development of AIDS
Sufferers have a weakened immune system and are more vulnerable to opportunistic infections