2C - Antibodies in medicine

Question 1

What are monoclonal antibodies?

Answer 1

Antibodies produced from a single group of genetically identical B cells (plasma cells) specific to 1 type of antigen.

Question 2

How are all monoclonal antibodies similar in structure?

Answer 2

They have the same primary structure as they are coded for by the same genes.

Therefore they have the same secondary and tertiary structures.

Question 3

Why are antibodies very specific?

Answer 3

They have a unique tertiary structure that only 1 particular antigen will fit into (one with a complementary shape).

Question 4

How are monoclonal antibodies produced?

Answer 4

The specific antigen binds to the receptor on the B cell.

A helper T cell sends out a chemical signal to activate the B cell which then releases specific antibodies.

Thus by using the same plasma cells, identical antibodies will be produced.

Question 5

What is the most successful cancer treatment so far?

Answer 5

Direct monoclonal antibody therapy.

Question 6

Explain direct monoclonal antibody therapy:

Answer 6

Antibodies given to patient and attach themselves to the receptors on their cancer cells. They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth.

Question 7

What can you also attach to antibodies used to target cancer cells?

Answer 7

Anti-cancer drugs.

Question 8

What do the antibodies bind to when targeting cancer cells?

Answer 8

Tumour markers.

Question 9

What does the fact that certain antibodies that target cancer cells and bind to the tumour markers mean?

Answer 9

The drug will only accumulate in the body where there are cancer cells.

Question 10

Give an example of a monoclonal antibody that is used to treat cancer:

Answer 10

Herceptin used to treat breast cancer.

Question 11

What is an advantage of using direct monoclonal antibody therapy?

Answer 11

Since the antibodies are non-toxic and are highly specific, they lead to fewer side effects than other forms of therapy.

Question 12

What does indirect monoclonal antibody therapy involve?

Answer 12

Attaching a radioactive or cytotoxic drug (a drug that kills cells) to the monoclonal antibody. When this antibody attaches to the cancer cells it kills them.

Question 13

What are the benefits of using monoclonal antibodies in smaller doses?

Answer 13

Cheaper and reduces any side effects the drug might have.

Question 14

How can we target drugs using monoclonal antibodies?

Answer 14

They all have the same, unique tertiary structure. Therefore, they will bind to a specific antigen with a complementary shape. Therefore, you can make monoclonal antibodies bind to a specific target molecule e.g. a cell antigen.

Question 15

In cancer treatment, what do monoclonal antibodies bind to?

Answer 15

Tumour markers (the cancers unique antigens).

Question 16

How do monoclonal antibodies work in cancer treatments?

Answer 16

There are anticancer drugs attached to the antibodies which will only be released where antibody binding occurs i.e. at cancer cells.

Question 17

What is a benefit of the fact that anticancer drugs that are attached to the antibodies in cancer treatments will only be released where antibody binding occurs?

Answer 17

This reduces side effects as the drugs will only stay at specific cells.

Question 18

Apart from treatments, how else are monoclonal antibodies used?

Answer 18

In medical diagnosis.

Question 19

What can monoclonal antibodies help to diagnose?

Answer 19

Influenza, hepatitis and chlamydia infections where they produce a much more rapid result than conventional methods of diagnosis.

Also, certain cancers.

Question 20

What is a benefit of using monoclonal antibodies in diagnosis?

Answer 20

They produce a much more rapid result than conventional methods of diagnosis.

Question 21

In pregnancy testing, what is the monoclonal antibody binding to?

Answer 21

hCG produced by the placenta.

Question 22

How do the monoclonal antibodies work in pregnancy testing?

Answer 22

The hCG antibody-colour complex moves along the strip until it is trapped by a different type of antibody. The complexes accumulate to produce a coloured line to confirm pregnancy.

Monoclonal antibodies are immobilised in coloured beads on a test strip.

Question 23

What are the ethical issues of monoclonal antibodies?

Answer 23

Involves mice and uses tumour cells.

Helps treat cancer and diabetes but there have been negative results in treating other issues such as MS (involving death).

Drug trials for the safety of new drugs aren’t always certain.

Question 24

What is the ELISA test?

Answer 24

A medical diagnostic test that uses antibodies.

Question 25

What does ELISA stand for?

Answer 25

Enzyme-linked immunosorbent assay.

Question 26

What is the ELISA test used for?

Answer 26

To test for pathogenic infections, for allergies etc.

Question 27

Explain what happens in an ELISA test

Answer 27

An antibody is used which has an enzyme attached to it. This enzyme can react with a substrate to produce a coloured product causing the solution in the reaction vessel to change colour.

If there is a colour change, it demonstrates that the antigen or antibody of interest is present in the sample being tested. The quantity can be worked out by the intensity of the colour change.

Question 28

What is a positive result in the ELISA test?

Answer 28

If there is a colour change, it demonstrates that the antigen or antibody of interest is present in the sample being tested. The quantity can be worked out by the intensity of the colour change.

Question 29

What are the different types of ELISA test?

Answer 29

Direct ELISA and indirect ELISA.

Question 30

What is direct ELISA?

Answer 30

Uses a single antibody that is complementary to the antigen you are testing for.

Question 31

What is indirect ELISA?

Answer 31

Uses 2 different antibodies to test for the antigen.

Question 32

How are direct and indirect ELISA different?

Answer 32

Direct ELISA uses a single antibody that is complementary to the antigen you are testing for.

Indirect ELISA uses 2 different antibodies to test for the antigen.

Question 33

What type of ELISA is used as a HIV test?

Answer 33

Indirect

Question 34

Explain how you can use an ELISA as a HIV test.

Answer 34

Indirect ELISA can be used to see if a patient possesses antibodies to the HIV virus:

HIV antigen is bound to the bottom of a well in a well plate.

A sample of the patient’s blood plasma, which might contain several different antibodies, is added to the well. If there are any HIV-specific antibodies, these will bind to the HIV antigen stuck to the bottom of the well. The well is then washed out to remove any unbound antibodies.

A secondary antibody, that has a specific enzyme attached to it, is added to the well. This can bind to the HIV-specific antibody (the primary antibody). The well is washed out again to remove any unbound secondary antibody.

A solution is added to the well that contains a substrate which is able to react with the enzyme attached to the secondary antibody and produce a coloured product. If the solution changes colour, it indicates that the patient has HIV-specific antibodies in their blood and is infected with HIV.

Question 35

When using the ELISA test to test for HIV, why are the washing steps important?

Answer 35

To make sure unbound antibodies aren’t left in the well which could affect the results - they could cause the test to appear positive when there are no HIV antibodies present.

Question 36

What happens to the secondary antibody if there is no primary antibody in the sample being tested in the ELISA test when the well is washed out?

Answer 36

Then all of the secondary antibody will be washed away.

Question 37

What would the solution look like is there was a negative result to the ELISA test?

Answer 37

No colour change because there would be no specific antibodies for the secondary antibodies to bind to.

Question 38

How are monoclonal antibodies produced outside of the body?

Answer 38

Mouse is exposed to non-self material against which an antibody is required.

The B cells in the mouse then produce a mixture of antibodies, which are extracted from the spleen of the mouse.

To enable these B cells to divide outside the body, they are mixed with cells that divide readily outside the body - tumour cells.

Detergent is added to the mixture to break down the cell-surface membranes of both types of celland enable them to fuse together - these fused cells are called hybridoma cells.

The hybridoma cells are separated under a microscope and each single cell is cultured to form a clone. Each clone is tested to see whether it is producing the required antibody.

Any clone producing the required antibody is grown on a large scale and the antibodies are extracted from the growth medium.