2: CELLS - ANTIGENS

Question 1

What are antigens?

Answer 1

• molecules (usually proteins) that are found on the surface of cells

Question 2

What are foreign antigens?

Answer 2

• antigens that aren’t normally found in the body
• trigger an immune response when when detected by the body

Question 3

What do antigens allow the immune system to identify?

Answer 3

• pathogens
• abnormal body cells (cancerous/pathogen-infected cells have abnormal antigens on their surface)
• cells from other individuals of the same species (cells from another individual will have some antigens that are different to yours unless the donor is genetically identical to you)
• toxins

Question 4

What is antigenic variation?

Answer 4

a change in a cells antigens due to a mutation

Question 5

What are some issues caused by antigenic variation?

Answer 5

• pathogens can’t be recognised by memory cells so they have to go through primary defences again which is slower
• new vaccines have to be developed as strains are immunologically distinct