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Preventing Disease
Artificial immunity
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© Boardworks Ltd 2008
Immunological memory
What is vaccination?
Vaccines stimulate the production of antibodies and memory
cells against the target pathogen without causing illness.
Why don’t vaccines cause illness?
They may contain an inactivated
form of the pathogen, killed by heat
treatment (which leaves the
immune-stimulating antigens intact).
They may contain an attenuated
(less virulent) form of the pathogen.
They may contain isolated antigens,
such as cell surface proteins, from
the pathogen.
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© Boardworks Ltd 2008
Influenza vaccines
New strains of the influenza virus are constantly emerging.
This is because antigens displayed on the virus change due
to mutation. This causes antigenic variation.
Antigenic variation makes it
hard to immunize a patient
against the influenza virus for
life with just a single vaccine.
The government works with other
organizations to identify current
strains of influenza. An effective
vaccine is developed each year.
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© Boardworks Ltd 2008
The MMR controversy
In 1998, a scientific paper was published in the medical
journal The Lancet, speculating that the MMR vaccine could
cause autism.
The authors thought that the MMR vaccine could damage
the bowel, allowing toxins that are normally destroyed in
digestion to move into the blood. If these toxins travelled to
the brain they might cause autism.
The authors did not prove
that this was the case but still
recommended that doctors
stop administering the MMR
vaccine until more research
was done.
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© Boardworks Ltd 2008
1988 Measles, mumps and rubella
vaccination introduced.
1996/7 Dr. Andrew Wakefield (and
others) carried out research to establish
whether or not there was a link
between the MMR vaccine and autism.
1998 Paper published in The Lancet
claiming that there was evidence for a
link between the MMR vaccine,
inflammatory bowel disease and
“Autism is a lifelong developmental
disability that affects how a person
communicates with, and relates to,
other people. It also affects how they
make sense of the world around them.”
The National Autistic Society
- Viral disease
- Highly infectious
- Transmitted via droplets
- Complications include meningitis and pneumonia
Case study
- Infectious viral
- Transmitted via droplets
- Complications caused when virus spreads from
parotid glands to CSF
- Infectious viral disease
- Transmitted via droplets
- Usually mild
- Dangerous for unborn babies when mother is
UK newspapers sensationalised
the story, ignoring studies that
refuted Wakefield’s claims.
In April 2006, the
first UK measles
death for 14
years occurred.
A journalist called Brian Deer
started to look more closely at
the situation…
• MMR is safe
• Single vaccines less safe (lower uptake; more
vaccines needed)
• Wakefield struck off by GMC
• Lives in US – anti-vaccination movement
• Measles cases and deaths increased
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© Boardworks Ltd 2008
Herd Immunity
• If more people are vaccinated against a particular
pathogen, an unvaccinated person is less likely to
come into contact with someone who is carrying
the pathogen.
• This reduces the spread of disease.
• Vaccination levels need to be high enough to
protect everyone – HERD IMMUNITY.
Herd Immunity
• In order to protect a whole community against an
infectious disease, at least 80% of the population
need to be immunized.
• This keeps the level of transmission low, protecting
those who cannot be immunized.
• The percentage needed to maintain herd immunity
varies between different diseases; for example, the
herd immunity threshold for measles is 83–94%.
Past paper question
Answers cont’
What are monoclonal antibodies?
Polyclonal antibodies are naturally produced in an immune
response. Different plasma cells secrete antibodies, resulting
in a variety of different antibodies against a specific antigen.
Monoclonal antibodies (mAbs) are antibodies produced
from clones of a single plasma cell and are therefore all
identical. They have many important uses, such as:
the treatment of cancer
and other diseases
drug screening
home pregnancy kits
scientific research.
Production of monoclonal antibodies
Large quantities of mAbs can be produced using mice or
A specific antigen is injected into
the animal, stimulating the
production of plasma cells.
The plasma cells are removed
from the animal and fused
with cancerous myeloma
cells from normal mice.
These form immortal
hybridoma cells, which can
produce a single type of
antibody indefinitely.
Exam question – monoclonal antibodies
- Antigen injected into animal
- Plasma cells produced
- Plasma cell fused with myeloma (cancer)
- Hybridoma cell formed – multiplies quickly
and indefinitely to produce many identical
antibodies (for the original antigen).