Humoral immune response

• B cells are activated when chemicals are released from T helper cells or the antibody molecules on their cell surface bind to a complementary antigen.

  • Once they are activated, the B cells divide by mitosis and differentiate into two kinds of cell - plasma cells and memory cells

  A) plasma

  B) memory

  
• B-lycophytes are involved in the humoral response (made in the bone marrow) and produce antibodies
• B-cell activation:

  1. B cells collide with complementary Helper T Cell receptors and activates the B Cell to go through clonal selection
  2. B cells are activated and undergo mitosis to make a large number of cells that differentiate into plasma cells and memory cells

  • B plasma cells make antibodies
  • B memory cells can divide rapidly into plasma cells when re-infected with same pathogen to make large number of antibodies
• antibodies are a quaternary structured protein made up of 4 polypeptide chains held together by disulphide bridges

  • variable region/ light chain where antigen binding site is located complementary to specific antigen
  • constant region/ heavy chain which is the same for all antibodies

  A) disulphide bridges

  
• How antibodies work:

  • Agglutination = antibodies contain 2 binding sites so bind to 2 antigens at a time so they are clumped together for phagocytes to engulf
  • Neutralising agent = some pathogens release toxins which make us ill but antibodies neutralise them
  • blocking access to human cells = when antibody bind to pathogen it prevents antigen fitting in host receptors so it cant get inside
• antibodies are proteins that have binding sites complementary to antigens and destroy the pathogen
• Antibiotics work by interfering with bacterial cell walls and ribosomes metabolic reactions, either killing the bacteria or stopping its growth

  no effect on viruses or our own cells because:

  • Viruses do not have ribosomes or cell walls (they use hosts ones) = antibiotic treatment is ineffective against bacteria
  • Human cells do not have cell walls and we do have ribosomes, but these are bigger than those found in bacteria and unaffected by antibiotics
• What is the role of the disulfide bridge in forming the quaternary structure of an antibody?

  • Joins two (different) polypeptides