immune response

Question 1

what is an antigen?

Answer 1

Proteins on the cell surface membrane that stimulate an immune response

Question 2

What do antigens allow the immune system to identify?

Answer 2

Pathogens, cells from other organisms of the same species, abnormal cells, toxins

Question 3

What is a pathogen?

Answer 3

any microorganism that causes disease

Question 4

What is the biological importance of antigens?

Answer 4

If the immune system can recognise or differentiate between self and non self cells, then a quick response to destroy non self cells reduces the risk of harm

Question 5

what is the potential problems with antigens?

Answer 5

Transplants can be rejected so use of immunosuppressive drugs needed, problems with blood transfusions

Question 6

What is antigenic variability?

Answer 6

Antigens on the cell surface membrane can change due to genetic mutations

Question 7

Why is antigenic variability a problem for the immune system?

Answer 7

Surface receptors on lymphocytes and memory cells that produce antibodies are complimentary to only one specific antigen. If the shape of the antigen changes, the antibody on the cell surface membrane is no longer complimentary, so there is a reinfection

Question 8

What is a non specific defence mechanism?

Answer 8

The response is immediate and the same for all pathogens, such as physical barriers and phagocytosis

Question 9

What is a specific defence mechanism?

Answer 9

The response is slower but more long lasting and it is specific to each pathogen, such as cell mediated responses

Question 10

How to lymphocytes recognise self body cells?

Answer 10

Each type of cell has specific molecules

Question 11

how do vaccines prevent people against disease?

Answer 11

vaccines contain antigens and the dead/inactive pathogen is injected. This triggers an immune response and memory cells are made. on second exposure to the same pathogen, memory cells recognise the pathogen and rapidly produce antibodies. the antibodies destroy the pathogen

Question 12

explain how phagocytosis of a virus leads to presentation of its antigens

Answer 12

phagosome fuses with lysosome and virus is destroyed by lysozymes released by lysosome. any soluble products are absorbed by phagocytes cytoplasm and antigens are displayed on the cell surface membrane

Question 13

describe how presentation of a virus’ antigen leads to the secretion of an antibody against the virus

Answer 13

t-helper cell binds to the antigen on the antigen presenting cell. th cell then stimulates a specific b cell which divides by mitosis to create clones, which then form plasma cells which release the specific antibody