Humoral immunity

• B lymphocytes and humoral immunity:

  • Involves antibodies, which are soluble in blood and tissue fluid of the body
  • Each B cell starts to produce a specific antibody that responds to one specific antigen.
• Humoral immunity until endocytosis

  1.  When an antigen is on the surface of a pathogen, foreign cell, toxin, damaged or abnormal cell. 
  2. There will be only one B cell that has an antibody on its surface that is complementary to the antigen. The antibody attaches to this antigen.
  3. The antigen enters the B cell by endocytosis and gets presented on its surface.
• humeral immunity after endocytosis

  1. Helper T cells bind to these processed antigens and stimulate this B cell to divide via mitosis to form a clone of identical B cells which becomes a plasma cell,
  2.  Cloned plasma cells produce and secrete the specific antibody that exactly fits the antigen on pathogens surface
  3. So antibodies attach to the antigens on the pathogen and destroy it.
  4. Some B cells develop into memory cells to respond to future infections.
• Plasma cells:

  • Secrete antibodies usually into the blood plasma
  • Responsible for the immediate defence of the body against infection. 
  • Primary immune response
  • Only survive for a few days.
  • Produces antibodies needed to destroy pathogen
• Memory cells:

  • Secondary immune response
  • Live longer than plasma cells, often for decades
  • Do not produce antibodies directly, but circulate in blood and tissue fluid, when encountering the same antigen at a later date, they divide rapidly and develop into plasma cells and more memory cells.
  • New memory cells circulate in readiness for future infection
  • Provides long term immunity, ensures a new infection is destroyed before causing harm.