2C.1 - Antigens

• what are antigens?

  molecules (usually proteins) that generate an immune response.
• where are antigens found?

  on the surface of all cells.
• what are pathogens? give an example.

  organisms that cause disease e.g. bacteria and fungi.
• what are toxins?

  poisonous antigens.
• why do only some antigens generate an immune response?

  foreign antigens (unusual to the body) trigger an immune response.
• name three places where are foreign antigens commonly found?

  pathogens.

  
  

  abnormal body cells e.g. carcinogenic.

  
  

  cells from other individuals of the same species e.g. organ donation.