Vaccines and Antibodies in

Medicine

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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.

The government works with other organizations to identify current strains of influenza. An effective vaccine is developed each year.

Antigenic variation makes it hard to immunize a patient against the influenza virus for life with just a single vaccine.

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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 did not prove that this was the case but still recommended that doctors stop administering the MMR vaccine until more research was done.

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.

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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.

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?

This mixed message caused confusion among the general public, leading to a drop in the number of children being given the combined vaccine.

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.

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Evaluating scientific papers

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The MMR controversy

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Vaccination

Vaccines1. 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. We know that Antigens on the surface of pathogens activate

the primary response2. 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 influenza2. 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 antigens2. 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 antibodies5. When antibodies come into contact with the cancer cells

they will bind to the tumour markers6. 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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