Memory Cells & Immune Response (WJEC GCSE Biology)

Higher Tier Only

Developing immunity

• The immune system is activated when a new antigen is encountered
• A specific lymphocyte must be identified to produce the complementary antibody to the antigen on the pathogen. It can take several days before the correct lymphocyte is found
  • Then it must clone itself before it can start producing antibodies against the antigen
  • This is the reason why an infected person will experience symptoms of the disease the first time they contract it
• Memory cells are produced and remain in the blood after the infection has gone
  • The presence of memory cells means that a person is said to be immune to the pathogen
  • These cells can remain in the blood for many years, so the immunity gained from an initial immune response can be long-term
• Should the immune system encounter the same antigen again in the future, antibodies are produced
  • more quickly
  • in larger concentrations 
• This is because memory cells are present so the correct memory cells can detect an antigen, clone themselves and produce the specific antibody much more quickly
  • This will often eliminate the pathogen before the infected person can show symptoms

Immunity graph

The secondary response is much larger and faster than the primary response due to the presence of memory cells in the blood