B- lymphocytes

• 1. Lymphocyte


  Type of lymphocyte that plays a key role in the specific immune response
• Maturation of B-lymphocytes


  1. B lymphocytes remain in the bone marrow until they are mature

  2. B cells gain specific cell surface receptors called B cell receptors (BCRs)
• B cell receptors (BCRs)


  Receptors on the cell surface of B cells that are antibodies and can combine specifically with one type of antigen
• B cells


  • A small number of B cells have the same BCRs, these genetically identical cells are called a clone
  • Mature B cells have many different types of antibody receptor on their cell surface membranes
• B cells in the immune response

  1. Clonal selection and activation

  2. Clonal expansion
• Clonal selection and activation

  1. B cells with complementary antibody receptors bind to antigens on antigen presenting cells

  2. This binding, together with interleukins released by T helper cells activates the B cells
• Clonal expansion


  Activated B cells divide by mitosis to produce clones
• Memory cells


  1. lymphocytes that remain circulating in the blood for a long time
• Plasma cells


  1. lymphocytes that secrete lots of antibody molecules (specific to the antigen) into the blood, lymph or linings of the lungs and the gut
• Activated B cells differentiate into

  1. Plasma cells

  2. Memory cells
• 1. lymphocytes


  • Only one of these cells has an antibody receptor that is specific to the shape of the antigen that has entered the body
  • The selected cell divides by mitosis
  • Some of the daughter cells develop into plasma cells, others into memory cells
• Plasma cells secrete antibodies


  That specifically bind to the antigen that entered the body
• This results in large numbers of identical B-lymphocytes being produced over a few weeks
• Plasma cells secrete lots of antibody molecules (specific to the antigen) into the blood, lymph or linings of the lungs and the gut
• The other B-lymphocytes become memory cells that remain circulating in the blood for a long time
• Antibodies appear roughly proportional to the amount of antigen and this is why symptoms disappear