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Vaccines and Antibodies in
Medicine
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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).
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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. We know that Antigens on the surface of pathogens activate the primary
response
2. If the pathogen returns a second time the antigens trigger a secondary
response and you do not become ill.
3. But, some antigens can change their surface antigens – known as Antigenic
Variation.
4. Therefore your immune system has to carry out a primary response for the
new antigens, which takes time and you fall ill again.
5. Antigenic variation also makes if difficult to develop vaccinations against some
pathogens
6. 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 B-cells. 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=sOTdqLDMvcg
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 antigen-antibody 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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