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Chapter 17: . Immunization and Immune Testing. Immunology. Based on adaptive (specific) immunity Humoral or antibody mediated B cells produce antibodies Cellular T cells can directly attack pathogens. Immunization. Two Artificial Methods of Immunity Active immunization

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chapter 17
Chapter 17:

Immunization and Immune Testing

  • Based on adaptive (specific) immunity
    • Humoral or antibody mediated
      • B cells produce antibodies
    • Cellular
      • T cells can directly attack pathogens
  • Two Artificial Methods of Immunity
    • Active immunization
      • administration of a vaccine
      • patient actively produces antibodies
    • Passive immunization
      • individual acquires immunity through direct transfer of antibodies
Brief History of Immunization
    • 12th century Chinese and variolation
      • Spread to England and America
    • 1796 – Edward Jenner discovered process of vaccination
      • Smallpox
    • 1879 – Louis Pasteur developed vaccine
      • Avirulence of Pasteurella multocida
      • Anthrax and rabies vaccines
    • Discovery that vaccines protected through the action of antibodies lead to practice of transferring antibodies directly
Vaccination Development Issues
    • Socioeconomic and political problems prevent nations from receiving vaccines
    • Effective vaccines unavailable for some pathogens
    • Vaccine-associated risks discourage investment in developing new vaccines
Active Immunization
    • Vaccine types
      • Attenuated (live) vaccines
        • Contain active pathogens with reduced virulence
        • stimulate a strong immune response due to the large number of antigen molecules
        • Can result in mild infections but no serious disease
Inactivated (killed) vaccines
      • Whole agent vaccines –deactivated but whole microbes
      • Subunit vaccines –antigenic fragments of microbes
        • Both types are safer than live vaccines because they cannot replicate or mutate to a virulent form
      • Antigenically weak so contain adjuvants
Toxoid vaccines
      • Modified toxins used to stimulate immunity
      • Stimulate antibody-mediated immunity
      • Require multiple doses because they possess few antigenic determinants
Problems with existing active immunizations:
        • Mild toxicity most common
        • Risk of anaphylactic shock
        • Residual virulence from attenuated viruses
        • Allegations that certain vaccines cause or trigger autism or other diseases
          • Research has not substantiated these allegations
Passive Immunization (Immunotherapy)
    • Antiserum
      • Contains preformed antibodies
      • Provides immediate protection
      • Limitations:
        • Contains antibodies against many antigens
        • Can trigger serum sickness (allergic reaction)
        • May be contaminated with viral pathogens
        • Antibodies are degraded relatively quickly
immune testing
Immune Testing
  • Serology
    • study of antigen-antibody interactions in blood serum
  • Diagnostic uses
    • Use known antibodies to detect antigens associated with an infectious agent
    • Use antigens to detect specific antibodies in a patient’s blood to determine exposure to a specific pathogen
Tests are chosen based on:
    • suspected diagnosis
    • cost to perform the test
    • speed with which results can be obtained
Precipitation Tests
    • Antigens and antibodies mixed
    • Form large macromolecular complexes called precipitates
    • Correct proportions are vital to create precipitation
Agglutination Tests
    • Clumping due to cross-linking of antibodies with antigens
    • Hemagglutination used to determine blood type
Labeled Antibody Tests
    • Antibody molecules are linked to some molecular “label” that enables them to be easily detected
      • Radioactive or florescent
    • Used to detect either antigens or antibodies
ELISA (enzyme-linked immunosorbent assay)
    • Uses enzyme as label
    • Reaction of the enzyme with its substrate produces a colored product
    • Most commonly used to detect antibodies in serum
Antibody sandwich ELISA
    • Modification ELISA technique
    • Commonly used to detect antigen
    • Antigen being tested for is “sandwiched” between two antibody molecules
Advantages of the ELISA
    • Can detect either antibody or antigen
    • Can quantify amounts of antigen or antibody
    • Easy to perform, inexpensive, and can test many samples quickly