specific immune response

• What are the 2 types of specific immune response?

  1. Cell mediated
  2. Humoral
• What is the process of the cell-mediated response?

  1. Complementary T helper lymphocytes bind to foreign antigens on APC
  2. Cell signalling via secretion of interleukins stimulates clonal expansion of complementary T helper lymphocytes (via rapid mitosis) which become memory cells or trigger the humoral response
  3. Clonal expansion of cytotoxic T cells/ T killer cells secrete perforin to destroy infected cells
• What is the process of the humoral response?

  1. complementary T helper lymphocytes bind to foreign antigens on antigen-presenting cells
  2. The antigen-presenting cells then release cytokines (interleukins?) that stimulate clonal expansion (rapid mitosis) of complementary B lymphocytes
  3. B lymphocyte cells then differentiate into plasma cells
  4. Plasma cells secrete antibodies with a complementary variable region to the antigen
• What is the function of B lymphocytes?

  To differentiate into plasma cells to secrete antibodies.
• What are the 3 types of T lymphocytes?

  T helper cells: secrete cytokines

  T killer cells: secrete perforins

  T regulatory cells: suppress other immune cells to prevent autoimmune disease
• What is an antibody?

  A Y-shaped glycoprotein made by a plasma B lymphocyte in response to a foreign antigen
• Describe the structure of an antibody.

  1. Antibodies have a quaternary structure: 2 light chains held together by disulfide bridges to 2 longer heavy chains
  2. They have antigen binding sites on the variable region of the light chain (and heavy chain), they have specific tertiary structures complementary to an antigen -> 2 variable regions allow binding of more than one antigen
  3. The rest of the molecule is known as the constant region: allows recognition by phagocytes
• Role of variable regions on antibodies?

  variable region allows binding to the complementary antigen

  variable region on different antibodies allow specificity to different antigens

  2 variable regions allow binding of more than one antigen
• How do antibodies lead to destruction of a pathogen?

  Agglutinins form antigen-antibody complexes to enhance phagocytosis. Antibodies bind to antigens on multiple pathogens, causing them to clump together.

  Opsonins mark microbes for phagocytes.

  Antitoxins make toxins insoluble via neutralisation -> prevents the toxin from working.
• What are memory cells?

  Specialised T helper/ B cells produced from the primary immune response.

  They remain in low levels in the blood.

  They can divide rapidly by mitosis if the organism encounters the same pathogen again.
• What are the differences between the primary and secondary immune response?

  The secondary immune response has a faster rate of antibody production

  shorter lag time between exposure and antibody production

  higher concentration of antibodies

  antibody level remains higher after the secondary response

  pathogen is usually destroyed before any symptoms shown
• What is agglutination?

  • Antibodies act as agglutinins causing pathogens carrying antigen-antibody complexes to clump together (agglutination). This reduces the chance that the pathogens will spread through the body and makes it possible for phagocytes to engulf a number of pathogens at one time
• What is opsonisation?

  • Antibodies can attach to bacteria making them readily identifiable to phagocytes, this is called opsonisation.
  • Once identified, the phagocyte has receptor proteins for the heavy polypeptide chains of the antibodies, which enables phagocytosis to occur
• Anti-toxins?

  • Antibodies can act as anti-toxins by binding to toxins produced by pathogens (e.g. the bacteria that cause diphtheria and tetanus) which neutralises them making them harmless