C4. Antigenic Variation Flashcards
What is antigenic variation?
Definition of antigenic variation?
What does it mean for the secondary response?
What does it mean is difficult?
Some pathogens can change their surface antigens. This is called antigenic variation. (Different antigens are formed due to changes in the genes of a pathogen.) This means that when you’re infected 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 primary response against these new antigens. This primary response takes time to get rid of the infection, which is why you get ill again.
Antigenic variation also makes it difficult to develop vaccines against some pathogens for the same reason.
Tip:
What are strains?
Tip: Pathogens of the same type that show antigenic variation are often referred to as strains.
Examples of pathogens that show antigenic variation include HIV and the influenza virus. Here’s how antigenic variation affects the production of vaccines to help prevent people catching influenza: (3 points)
1) The influenza (flu) vaccine changes every year. That’s because the antigens on the surface of the influenza virus change regularly, forming new strains of the virus.
2) Memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens. The strains are immunologically distinct. Every year there are different strains of the influenza virus circulating in the population, so a different vaccine has to be made.
3) New vaccines are developed and one is chosen every year that is the most effective against the recently circulating influenza viruses. Governments and health authorities then implement a programme of vaccination using the most suitable vaccine.
