Chapter 16

• Immunology


  The scientific study of the immune system and immune responses
• Primary functions of the immune system

  • Differentiate between "self' and "non-self"
  • Destroy that which is "non-self"
• Cells involved in immune responses

  • B lymphocytes (or B cells)
  • T lymphocytes (or T cells)
  • Natural killer cells (NK cells)
• Helper T cells


  A type of T cell (1)
• Cytotoxic T cells


  A type of T cell (2)
• Major arms of the immune system

  • Humoral immunity
  • Cell-mediated immunity
• Acquired immunity


  Immunity that results from the active production or receipt of antibodies during one's lifetime
• Types of acquired immunity

  • Active acquired immunity
  • Passive acquired immunity
• Active acquired immunity


  Antibodies are produced within the person, usually providing long lasting protection
• Passive acquired immunity


  Antibodies are received that were produced by another person or persons or by an animal, usually providing only temporary protection
• Vaccine


  Material that can artificially induce immunity to an infectious disease, usually following injection or ingestion
• Types of vaccines

  • Attenuated vaccines
  • Inactivated vaccines
  • Subunit vaccines
  • Conjugate vaccines
  • Toxoid vaccines
• Natural passive acquired immunity


  Small antibodies, IgG, present in mother's blood cross the placenta to reach the fetus
• Artificial passive acquired immunity


  Antibodies from an immune person are transferred to a susceptible person, e.g. hepatitis B immune globulin
• Antigen


  Foreign organic substances that are large enough to stimulate the production of antibodies
• Antibody


  Proteins produced by lymphocytes in response to the presence of an antigen
• Primary immune response


  The initial immune response to an antigen, taking 10-14 days for antibodies to be produced
• Secondary immune response


  The increased production of antibodies following the second exposure to a particular antigen
• Antigen-antibody complex


  Formed when an antibody combines with an antigen
• Effects of antigen-antibody complexes

  • Activation of leukocytes
  • Lysis of bacterial cells
  • Increased phagocytosis as a result of opsonization
• Cell-mediated immunity (CMI)


  A complex system of interactions among many types of cells and cellular secretions (cytokines) that can control chronic infections by intracellular pathogens
• Cells involved in CMI

  • Macrophages
  • TH cells
  • TC cells
  • NK cells
  • Granulocytes
• Natural killer (NK) cells


  A subpopulation of lymphocytes that can kill target cells, including foreign cells, host cells infected with viruses or bacteria, and tumor cells
• Hypersensitivity


  An overly sensitive immune system
• Types of hypersensitivity reactions

  • Immediate-type (type I, II and III)
  • Delayed-type (type IV)
• Type I hypersensitivity reactions


  Also known as anaphylactic reactions, including classic allergic responses such as hay fever, asthma, hives, and food allergies
• Hypersensitivity


  Overly sensitive immune system
• Immediate-type hypersensitivity


  Occurs from within a few minutes to 24 hours after contact with a particular antigen
• Delayed-type hypersensitivity


  Usually takes more than 24 hours to manifest themselves
• Type I hypersensitivity reactions


  Also known as anaphylactic reactions, include classic allergic responses such as hay fever symptoms, asthma, hives, and gastrointestinal symptoms that result from food allergies, and allergic responses to insect stings and drugs
• The Allergic Response


  1. Atopic persons produce IgE antibodies when exposed to allergens

  2. IgE antibodies bound to basophils in the blood or to mast cells in connective tissues

  3. Allergic reaction results
• Factors in the development of Type I hypersensitivity

  • Exposure to allergen
  • Production of IgE antibodies
  • Binding of IgE to mast cells/basophils
  • Allergen cross-linking of IgE
  • Mast cell/basophil degranulation
  • Release of chemical mediators
• Events in Type I hypersensitivity reactions

  1. Allergen exposure

  2. IgE antibody production

  3. IgE binding to mast cells/basophils

  4. Allergen cross-linking of IgE

  5. Mast cell/basophil degranulation

  6. Release of chemical mediators

  7. Allergic symptoms
• Localized Type I hypersensitivity reactions


  Involve mast cell degranulation, result in allergic reactions like hay fever, asthma, food allergies
• Systemic Type I hypersensitivity reactions


  Involve basophil degranulation, occur throughout the body, can lead to anaphylactic shock, life-threatening
• Systemic anaphylaxis


  Results from the release of chemical mediators from basophils in the bloodstream, occurs throughout the body, much more serious than localized anaphylaxis
• Latex allergy


  Latex can trigger irritant contact dermatitis, allergic contact dermatitis, and immediate type hypersensitivity
• Allergy skin testing and allergy shots


  1. Skin tests used to identify offending allergens

  2. Positive test indicated by cutaneous anaphylaxis

  3. Immunotherapy (allergy shots) used to produce IgG blocking antibodies
• Type II hypersensitivity reactions


  Cytotoxic reactions where body cells are destroyed
• Sequence of events in Type II hypersensitivity

  1. Drug binds to cell surface

  2. Anti-drug antibodies bind to drug

  3. Complement activation on cell surface

  4. Complement cascade leads to cell lysis