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Vaccines and
Antibodies in
Medicine
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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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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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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The media’s role in the MMR controversy
Many studies have concluded that the MMR vaccine is safe
and only a few studies claim that it isn’t. However, this was
not reflected by the media coverage.
The majority of coverage centred on the possibility of
a link between the MMR vaccine and autism, while the
government insisted that the vaccine was safe.
This mixed message caused confusion among the general
public, leading to a drop in the number of children being given
the combined vaccine.
Should scientists be more careful about how they present
their research or should the media be responsible for how
they present controversial topics to society?
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Evaluating scientific papers
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The MMR controversy
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Vaccination
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Vaccines
1. During the primary response of your immune
system the B-cells are dividing to deal with the
pathogen. As this takes time you suffer from the
disease.
2. Vaccines can help avoid this. Vaccines contain
antigens that cause your body to produce
memory cells against a specific pathogen. Since
the pathogen is dead it does not cause disease.
3. Herd immunity – since vaccines reduce the
chances of getting a disease, those who are not
vaccinated also reduce the risk of catching the
disease (because there are fewer people to catch
it from).
Vaccines continued
4. When a vaccine is used, a dead or attenuated
(weakened) pathogen is injected. The vaccine
always contains antigens. These may be free or
attached to the pathogen.
5. Vaccines maybe taken orally or by injection. If
taken orally they maybe be broken down by
enzymes or not absorbed into the blood as the
molecules maybe too large.
6. Booster vaccines maybe given after several years
to make sure memory cells are still being
produced.
Pathogens can evade the immune
system!
1.
2.
3.
4.
5.
6.
We know that Antigens on the surface of pathogens activate
the primary response
If the pathogen returns a second time the antigens trigger a
secondary response and you do not become ill.
But, some antigens can change their surface antigens – known
as Antigenic Variation.
Therefore your immune system has to carry out a primary
response for the new antigens, which takes time and you fall ill
again.
Antigenic variation also makes if difficult to develop
vaccinations against some pathogens
HIV, S.pneumonia bacteria and the influenza virus all show
antigenic variation.
Antigenic variation in influenza
• AQA students need to know this.
1. The influenza virus causes influenza
2. Proteins (neuraminidase and haemagglutinin) on the
surface of the influenza virus act as antigens, triggering the
immune system.
3. These antigens can change regularly, forming new strains of
the virus.
4. Memory cells produced from infection with one strain of flu
will not recognise other strains with different antigens.
5. This means your immune system produces a primary
response every time you’re infected with a new strain.
6. This results in you suffering from flu, each time you are
affected by a new strain.
Influenza
• This image shows the antigenic variation.
Monoclonal Antibodies (mAB)
1. Monoclonal antibodies are antibodies produced
from a single group of genetically identical Bcells. Therefore they are all identical in structure.
2. Antibodies are very specific because their binding
sites have a unique structure that only one
particular antigen will fit into.
3. Monoclonal antibodies can bind to anything you
want. This is very useful in dealing with cell
antigen and they will only bind to this molecule.
4. http://www.youtube.com/watch?v=sOTdqLDMvc
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Plenary
• How do vaccines protect individuals?
• Vaccines contain antigens, which maybe free, dead
or ___________
• What is the disadvantage of taking a vaccine orally?
• What is antigenic variation?
• Describe antigenic variation and influenza
• Describe how mAB is used in pregnancy tests
• Describe how mAB is used for cancer
Example of mAB
• Monoclonal antibodies are used in pregnancy tests
1.
hCG hormone is detected during a pregnancy test. hCG
hormone is found in pregnant womens urine.
2. Antibodies for hCG are bound to a colured bead (blue)
3. When urine is applied to the specified area any hCG will
bind to the antibody on the beads, forming an antigenantibody complex.
4. Urine then moves up the stick to the test strip carrying any
beads with it
5. The test strip contains antibodies to hCG that are stuck in
place
6. The strip turns blue if hCG is present because the
immobilised antibody binds to any hCG. If no hCG is
present, the beads will pass through the test area without
binding to anything, and so it won’t go blue.
If you are still unclear watch this video!
https://www.o2learn.co.uk/o2_video.php?vid=1630
Targeting cancer cells
1. Different cells in the body have different surface antigens
2. Cancer cells have antigens called tumour markers that are
not found on normal body cells.
3. Monoclonal antibodies can be made that will bind to the
tumour markers.
4. Anti-cancer drugs can also be attached to the antibodies
5. When antibodies come into contact with the cancer cells
they will bind to the tumour markers
6. This results in the drug accumulating in the body where
there are cancer cells.
7. Therefore the side effects of an antibody-based drug are
lower then other drugs because they accumulate near
specific cells.
Plenary
• Vaccines contain free, dead or ______________
antigens
• What is herd immunity?
• What is the disadvantage of taking a vaccine orally?
• Antigens on the surface of pathogens activate a
_________ response
• What is antigenic variation?
• Describe antigenic variation in influenza
• Describe how mAB are used to treat cancer
• Describe how a pregnancy test works. You must use
(hCG, antibodies, and immobilised in your answer)
Exam questions
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Answers
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