Antigenic Variation

• What does antigenic variation do?

  Antigenic Variation helps some pathogens evade the immune system
• What activates the primary response?


  antigens on the surface of pathogens
• what do antigens on the surface of pathogens do?

  activate the primary response
• What happens when you are infected a second time with the same pathogen(which has the same antigens on its surface)?

  the antigens activate the secondary response and you do not get ill
• What can some pathogens do?

  change their surface antigens

  this antigen variability is called ANTIGENIC VARIATION (Different antigens are formed due to changes in the genes of a pathogen)
• What are the consequences of antigenic variation ?

  When you're infectd for a second time, the memory cells produced from the first infection will not recognise the different antigens.

  So the immune system has to start from scratch and carry out a primarh response against these new antigens

  this primary response takes time to get rid of the infection and this is why one gets ill again
• what does antigenic variation also make it difficult to do?

  To develop vaccines against some pathogens for the same reason.
• give 2 examples of pathogens that show antigenic variation?

  HIV and the influenza virus
• How does antigenic variation affect the production of vaccines against Influenza?

  • the influenza/flu vaccine changes every year due to antigenic variation
  • memory cells produced from vaccination with ONE STRAIN of the flu will not recognise other strains with different antigens. the strains are IMMUNOLOGICALLY DISTINCT