humoral immune response

• B lymphocytes


  Also known as B cells, lymphocytes which are white blood cells involved in the specific immune response
• Humoral response

  The response involving B cells and antibodies
• The term 'humoral' comes from the olden days term for body fluids, 'humor', because antibodies are soluble and transport around in the blood and other bodily fluids
• 1. cell activation

  • B cells have approximately 10 million different antibodies on their surface, complementary to 10 million different antigens
  • When a B cell collides with its complementary antigen, it takes in the antigen by endocytosis and presents it on its cell surface membrane
  • This activates the B cell to go through clonal expansion and differentiation, also known as clonal selection
• Clonal expansion and differentiation

  1. B cell undergoes mitosis to create large numbers of clones

  2. Clones then differentiate into plasma cells and memory B cells
• Plasma cells

  Able to make antibodies
• Memory B cells

  Can divide rapidly into plasma cells if re-exposed to the same antigen, allowing for a rapid antibody response
• Primary immune response

  First exposure to an antigen, slower antibody production
• Secondary immune response


  Re-exposure to an antigen, rapid antibody production from memory B cells differentiating into plasma cells
• Antibodies

  • Quaternary structure proteins made up of four polypeptide chains
  • Variable region binds to specific antigens
  • Constant region is the same
• Agglutination

  Antibodies bind to antigens, causing them to clump together, making it easier for phagocytes to locate and engulf the pathogen
• Clonal selection creates monoclonal antibodies
• Memory B cells can remain in the blood for decades
• B cells

  Immune system cells that recognize antigens and trigger a series of immune system actions
• 1. cell activation, antibody production, and memory cell formation

  1. Mature B cell encounters pathogen

  2. B cell takes in antigen BCR complex

  3. Antigen gets broken down into peptides

  4. B cell presents peptides on surface using MHC class II

  5. Helper T cells recognize and bind to antigen MHC-2 complex

  6. B cell becomes fully activated

  7. Clonal expansion - B cell divides and differentiates into plasma cells and memory B cells

  8. Plasma cells secrete antibodies

  9. Antibodies neutralize virus, trigger complement system, or mark for destruction

  10. Memory B cells remember specific antigen and rapidly respond upon re-exposure

  11. Isotype switching - change antibody class to better target pathogen

  12. Affinity maturation - refine antibody binding to antigens
• Plasma cells

  • Antibody producing factories
• Antibodies

  • Specialized proteins that recognize and neutralize specific antigens
• Memory B cells

  • Provide long-lasting immunity by remembering specific antigens