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Chapter 17 – Immunization and Immune Testing
Discuss the history of vaccination from the 12th century to the present?
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12th century the Chinese noticed that children who got small pox never got it again
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Procedure is called variolation
o This significantly reduced the population’s overall morbidity to the disease
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This allowed England to adopt the policy as well as American
colonies
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In late 1700’s, Jenner infected people with cowpox (mild related disease to smallpox) and they
were protected against smallpox so that gave rise to vaccination – since cowpox was called
vaccinia
o The protective inoculum was a vaccine
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People didn’t
understand how it worked
1879, Pasteur conducted experiments and realized this can be done to protect from other
diseases
Late 1900’s, immunologists formed vaccines ridding many infectious diseases
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Describe the advantages and disadvantages of the five types of vaccines
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Attenuated (Modified Live) Vaccines
o Virulent microbes aren’t normally used in vaccines because they cause disease
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o Attenuation – Reduction of virulence
o Attenuated Vaccines – They contain active, but avirulent organisms or viruses
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 Pregnant women can’t receive these vaccines in fear of harming the fetus
through the placenta
 Modified viruses can revert to wild type or mutate to a form that causes
infection or disease
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So, subunit vaccines are becoming more popular
 Antigenically weak since inactivated vaccines can’t reproduce
 Multiple or high doses increases risk of allergies and can stimulate inflammation
o Adjuvants can increase antigenicity of the vaccine by stimulating immune cell receptors
Toxoid Vaccines
o Chemically or thermally modified toxins used in vaccines to stimulate active immunity
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Vaccines Using Recombinant Gene Technology
o Advantages
 More effective, cheaper, safer
 Can selectively delete virulence genes from a pathogen, creating an irreversible
attenuated microbe that can’t revert back to virulence
 Can produce large quantities of pure viral or bacterial antigens for use in
vaccines
o Disadvantages
 Can express the antigen and act as a live vaccine

Describe three methods by which recombinant genetic techniques can be used to develop improved
vaccines
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They can delete virulence genes from a pathogen producing an irreversible attenuated microbe
that can’t revert to a virulent pathogen
Scientists isolate the gene that codes for an antigen and inserts it into a bacterium, yeast, or
other cell that then expresses and releases the antigen
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The body’s cell take the plasmid (with antigen’s DNA) and then transcribes and translates
the gene to produce antigen that then triggers the immune response
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When immunization in a population falls, local epidemics occur
Most vaccines have a mild toxicity associated with their administration, some of which
even cause pain at the injection site
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Active forms of the vaccine may linger and cause disease
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Passive immunotherapy is a term used to describe the process in which antibodies are
administered to a patient, in order to quickly protect that patient against a new or ongoing
disease
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o This serum is also collected from large animals, both of which can then be administered
intravenously to the patients in which they are needed
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passive immunotherapy
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o Active immunization provides long-term protection that is capable of re-stimulation to
produce memory cells
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 Since, preformed antibodies are removed rapidly from the blood; memory B
cells are not produced
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o Repeated use of passive immunotherapy can cause an allergic response known as serum
sickness
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What are hybridomas and how are they produced?
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Scientists have overcome the limitations of antiserum (as seen in the passive immunity
question) by developing hybridomas
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Each hybridoma divides continuously (because of the cancerous plasma cell component) to
produce clones of itself, and each clone secretes large amounts of a single antibody molecule
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The diagram below illustrates how hybridomas are produced

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