Topic 2---C: Cells and The Immune System- 4. Antigenic Variation

Question 1

What is antigenic variation?

Answer 1

When a pathogen changes their surface antigens.

Question 2

How are different antigens formed?

Answer 2

Due to the changes in the genes of a pathogen.

Question 3

What activates the primary response?

Answer 3

The antigens on pathogens surface.

Question 4

What activates the secondary response?

Answer 4

When you’re infected a second time with the same pahogen which has the same antigens on it’s surface and you don’t become ill.

Question 5

What does it mean when you’re infected for the second time and you’re undergoing antigenic variation?

Answer 5

• When you’re infected for the second time, the memory cells produced from the first infection will not recognise the different antigens.
• So the immune system has to start off from scratch and carry out a primary response against these new antigens.
• The primary response takes time to get rid of the infection which is why you become ill again.

Question 6

What does antigenic variation make it difficult to develop?

Answer 6

Vaccines against some pathogens.

Question 7

What are examples of pathogens that show antigenic variation?

Answer 7

• HIV
• Influenza virus

Question 8

How does antigenic variation affect the production of vaccines to help prevent people catching influenza?

Answer 8

• The influenza (flu) vaccine changes every year because of the antigens on the surface of the influenza virus changing regularly which forms new strains of the virus.
• Memory cells produced from vaccination of one strain of the flu wont recognise other strains with different antigens so a different vaccine has to be made.
• New vaccines are developed and one is chosen every year that is the most effective against the recently circulating influenza virus.

Question 9

Why do you become ill with flu even if you’ve been infected by the influenza virus before?

Answer 9

• If the influenza virus undergoes antigenic variation the memory cells produced from the first infection will not recognise the different antigens.
• The immune system has to carry out a primary response to the new antigens.
• This takes time to get rid of the infection which is why you become ill again.