specific immune response

• phagocytes that present some of the pathogen's antigens on their surface are antigen presenting cells
• T cell's receptor proteins bind to specific antigen presenting cells, forming a antigen-receptor complex
• antigen-receptor complex activates the T cell to divide by mitosis, producing clones
• T cells can differentiate/stimulate its cells to:

  1. B cells
  2. killer T cells
  3. memory cells
  4. release signalling chemicals
• killer T cells

  • bind to antigens on infecting cells and kills abnormal/foreign cells
  • kill infected cells with a protein called perforin
  • perforin makes holes in the cell's surface membrane
  • infected cell becomes permeable -> loses all its contents
• memory cells:

  • circulate the blood and body fluids
  • provide rapid response against the same pathogen in the future
• signalling chemicals:

  • activate the phagocytes to continue destroying pathogens by phagocytosis
• T cells are apart of cell-mediated response
• B cells are apart of humoral response
• B cells get the antigen from pathogens or antigen-presenting cells and presents it on its cell membrane
• B cells response:

  1. T cells activate B cells
  2. B cells divide by mitosis, producing clones
  3. these clones are plasma cells
  4. plasma cells secrete antibodies
  5. plasma cells produce memory cells
• antibodies bind to specific antigens to form an antigen-antibody complex
• antibodies structure:

  • made up of 4 polypeptide chains - 2 heavy and 2 light
  • chains joined together by disulphide bridges
  • all antibodies have the same constant regions
  • variable regions form the binding site
  • variable regions have different tertiary structures complementary to an antigen
• one antibody can bind to to two pathogens at once
• antibody functions:

  • agglutination
  • neutralising toxins
  • prevent viruses entering host cells
• agglutination:

  • antibodies bind to antigens on pathogens
  • clumps pathogens together
  • clumps are destroyed by phagocytosis
  • phagocytes can engulf multiple pathogens at once
• neutralising toxins:

  • antibodies bind to toxins released by pathogens
  • causes toxin's active region to change shape
  • this neutralises them
• preventing viruses entering host cells:

  • antibodies bind to attachment proteins on virus surface
  • virus can no longer bind to receptors on host cell surface
• how antibodies detect specific antigens:

  • the variable regions of the antibody has a specific sequence of amino acids
  • so the tertiary structure of the binding site is complementary to the antigen
  • so an antigen-antibody complex forms
• What are the two types of lymphocytes?

  T-cells and B-cells
• What is the process of the humoral response involving B cells?

  1. B cell receptors bind to complementary antigens on pathogen
  2. B cell destroys pathogen and presents the antigens on its surface
  3. helper T cell receptors bind to complementary B cell
  4. Antigen-receptor complex forms, stimulating B cells to divide by mitosis = clones
  5. Each clone differentiates into plasma or memory cells
  6. Plasma cells produce antibodies
  7. Memory cells trigger the secondary immune response
• what is the role of plasma cells?

  to produce and secrete antibodies
• what triggers the secondary immune response?

  memory cells
• what are the three types of antigen-presenting cells (APCs)?

  1. B-cells
  2. Phagocytes
  3. Virus-infected body cells
• How do T cells interact with antigens on APCs?

  T cells have receptors complementary to antigens
• What is the cell-mediated response involving T cells?

  1. Helper T cell binds to antigen on APC
  2. Antigen-receptor complex stimulates helper T cell to clone
  3. Clones have different roles:

  • Stimulate B cells to clone
  • Stimulate phagocytosis
  • Stimulate cytotoxic T cells
• What role does a helper T cell play in phagocytosis?

  It releases chemicals to attract phagocytes to the pathogen
• How do cytotoxic T cells function against infected body cells?

  They bind to antigens on infected body cells and release perforin
• What is the effect of perforin released by cytotoxic T cells?

  They create holes in the cell membrane
• What happens when perforins make holes in a cell's membrane?

  Substances flow in and out uncontrollably
• What are the roles of the clones produced by helper T cells?

  1. Stimulate B cells to clone into memory/plasma
  2. Stimulate phagocytosis
  3. Stimulate cytotoxic T cells