• During an immune response, B-lymphocytes form?two types of cell:?plasma cells?and?memory cells
• Memory cells form the basis of?immunological memory?– the cells can last for?many years?and often a lifetime
• There are two types of immune response:
  • Primary immune response?(responding to a?newly encountered antigen)
  • Secondary immune response?(responding to a?previously encountered antigen)

   

Primary immune response

• After clonal selection and expansion, the B-lymphocytes that have become?plasma cells? secrete lots of?antibody molecules?(specific to the antigen) into the blood, lymph or linings of the lungs and the gut
• These plasma cells are?short-lived?(their numbers drop off after several weeks) but the antibodies they have secreted stay in the blood for a longer time
• The other B-lymphocytes become?memory cells?that remain circulating in the blood for a?long time
• This response to a newly encountered pathogen is relatively slow

Secondary immune response

• If the?same antigen?is found in the body a second time, the memory cells recognise the antigen, divide very quickly and differentiate into plasma cells (to produce antibodies) and more memory cells
• This response is?very quick, meaning that?the infection can be destroyed and removed?before the pathogen population increases too much and symptoms of the disease develop
• This response to a previously encountered pathogen is,?relative to the primary immune response, extremely fast

During a secondary immune response, memory cells that remained in the blood divide very quickly into plasma cells (to produce antibodies) and more memory cells