Antigens

• Antigens are molecules that generate an immune response when detected
• Antigens are usually proteins
• Antigens are found on the surface of cells
• Used by immune system to identify:

  • pathogens
  • abnormal body cells (cancerous cells/ tumours)
  • Toxins released from bacteria
  • Foreign cells (transplants)
• Antigens activate primary response
• Pathogens can slightly change antigens through antigenic variation so that memory cells don't recognise them. This makes vaccine development difficult
• Antigenic variation affects vaccinations:

  • flu antigens change yearly
  • Vaccine produced with one strain won't recognise other strains
  • Each strain is immunologically distinct