Chapter 17
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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


Immunology

Immunology

  • Based on adaptive (specific) immunity

    • Humoral or antibody mediated

      • B cells produce antibodies

    • Cellular

      • T cells can directly attack pathogens


Immunization

Immunization

  • 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


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  • 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


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  • 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


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  • 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


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  • 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


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  • Toxoid vaccines

    • Modified toxins used to stimulate immunity

    • Stimulate antibody-mediated immunity

    • Require multiple doses because they possess few antigenic determinants


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  • 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


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  • 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


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Many limitations overcome through development of hybridomas


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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


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  • Tests are chosen based on:

    • suspected diagnosis

    • cost to perform the test

    • speed with which results can be obtained


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  • Precipitation Tests

    • Antigens and antibodies mixed

    • Form large macromolecular complexes called precipitates

    • Correct proportions are vital to create precipitation


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  • Agglutination Tests

    • Clumping due to cross-linking of antibodies with antigens

    • Hemagglutination used to determine blood type


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  • 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


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  • 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


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  • Antibody sandwich ELISA

    • Modification ELISA technique

    • Commonly used to detect antigen

    • Antigen being tested for is “sandwiched” between two antibody molecules


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  • 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


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