Antigens

Question 1

What is an antigen?

Answer 1

a molecule (usually a protein) that triggers an immune response when detected by the body - located on the surface of the cell

Question 2

What’s a foreign antigen?

Answer 2

an antigen that are not normally found in the body - what the immune system usually responds to

Question 3

What do antigens enable to immune system to identify?

Answer 3

1.)Pathogens- have antigens on them which are identified as foreign by IS cells
2.) Abnormal Body cells - cancerous or pathogen infected cells have abnormal antigens on their surface which triggers an immune response
3.)Toxins
4.) Cells from other organisms of the same species - when you receive cells from another person those cells will have some antigens that are different to your own - forgein antigens will lead to immune response which leads to rejection of transplanted organs if drugs aren’t taken to suppress the immune response

Question 4

What is antigen variability?

Answer 4

• pathogen DNA can mutate frequently
• if a mutation occurs in the gene which codes for he antigen then the shape of the antigen will change
• any previous immunity to this pathogen is no longer effective as all the memory cells the in the blood will have a memory of the old antigen shape
  -e.g why we need a new flu vaccine each year

Question 5

How do lymphocytes recognise cells?

Answer 5

• each lymphocyte can recognise a different shaped antigen
  -lymphocytes are made when you’re a foetus when you’re unlikely to be exposed to any cells other than self cells
  -the lymphocytes complementary to the antigens on self cells will die or production will be suppressed to prevent lymphocytes attacking self cells
• the only remaining lymphocytes are complementary to non self cells and pathogenic cells
  -same processes occur in the b one marrow
• sometimes the process doesn’t work and lymphocytes which will attack self cells are produced