Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chapter 17: Immunization and Immune Testing

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Immunology Based on adaptive (specific) immunity – Humoral or antibody mediated – B cells produce antibodies – Cellular – T cells can directly attack pathogens

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Brief History of Immunization – 12 th 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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Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings – 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings – 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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Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Many limitations overcome through development of hybridomas

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Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Tests are chosen based on: – suspected diagnosis – cost to perform the test – speed with which results can be obtained

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Precipitation Tests – Antigens and antibodies mixed – Form large macromolecular complexes called precipitates – Correct proportions are vital to create precipitation

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Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Agglutination Tests – Clumping due to cross-linking of antibodies with antigens – Hemagglutination used to determine blood type

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Antibody sandwich ELISA – Modification ELISA technique – Commonly used to detect antigen – Antigen being tested for is “sandwiched” between two antibody molecules

Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings 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