Plasma & Memory Cells (AQA A Level Biology) : Revision Note

Plasma & Memory Cells

• During an immune response B-lymphocytes give rise to:

  • plasma cells, which produce antibodies

  • memory cells, which form the basis of immunological memory

• Plasma cells and memory cells are involved in two different levels of immune response:

  • primary immune response to a newly encountered antigen

  • secondary immune response to a previously encountered antigen

Primary immune response

• After clonal selection and mitosis the B-lymphocytes that have become plasma cells secrete specific antibodies into the blood

  • These plasma cells are short-lived and antibody numbers gradually decrease over time after the response has ended

• Some B-lymphocytes develop into memory cells that remain in the blood for a long time

• The primary response to a newly encountered pathogen is relatively slow, due to:

  • time taken to find lymphocytes with complementary receptors (clonal selection)

  • time taken for mitosis to occur

  • time taken for antibody production to begin

Secondary immune response

• If the same antigen is encountered a second time the memory cells recognise the antigen, divide very quickly and differentiate into plasma cells to produce antibodies

• 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