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 for

  • locating lymphocytes with complementary receptors (clonal selection)

  • mitosis of lymphocytes to occur

  • antibody production to begin

Secondary immune response

• If the same antigen is encountered a second time the memory cells recognise the antigen

• This allows them to divide very quickly and differentiate into plasma cells to produce antibodies

• As a result, the secondary response is

  • quicker than the primary immune response

  • produces more antibodies than the primary immune response

• If memory cells are present, infections can be destroyed and removed before the pathogen population increases too much and symptoms of the disease develop