Antibodies in Medicine

Question 1

What are monoclonal antibodies?

Answer 1

Antibodies produced from a single group of genetically identical B-cells. This means they’re identical in structure

Question 2

Monoclonal antibodies are specific, explain

Answer 2

Their binding sites have a unique tertiary structure that only one specific antigen will fit into

Question 3

How can you use monoclonal antibodies to target cancer cells?

Answer 3

1. Different body cells have different surface antigens
2. Cancer cells have antigens called tumour markers
3. Monoclonal antibodies can be made to bind to tumour markers
4. You can attach anti-cancer drugs to these monoclonal antibodies
5. When the antibodies come in contact with the tumour markers they bind to them
6. The drug will only accumulate in the body where there are cancer cells

Question 4

How can you use monoclonal antibodies in pregnancy tests?

Answer 4

1. Application area contains antibodies for hCG bound to a coloured bead (blue)
2. When urine is applied any hCG will bind to the antibody on the beads, forming an antigen-antibody complex
3. The urine moves up the test stick, carrying any beads with it
4. The test strip contains antibodies to hCG that are immobilised
5. If hCG is present the strip turns blue because the immobilised antibody binds to any hCG

Question 5

What does ELISA stand for?

Answer 5

Enzyme-limked immunosorbent assay

Question 6

What is an ELISA test?

Answer 6

It allows you to see if a patient has any antibodies to a certain antigen, or any antigen to a certain antibody

Question 7

What happens in an ELISA test?

Answer 7

An antibody is used, that has an enzyme attached. This enzymes reacts with a substrate to form a coloured product - coloured product shows a positive result. The quantity of antigen/antibody present can be worked out using the intensity of the colour change

Question 8

What are the two types of ELISA test?

Answer 8

1. Direct - uses a single antibody that is complimentary to the antigen you’re testing for
2. Indirect - uses two different antibodies

Question 9

Explain the ELISA test for HIV

Answer 9

1. HIV antigen is bound to the bottom of a well
2. A sample of blood plasma is added to the well. If there are any HIV-specific antibodies they will bind to the HIV antigen. The well is washed to remove any unbound antibodies
3. A second antibody with an enzyme attached is added to the well. This can bind to the HIV-specific antibody. The well is washed out again to remove an unbound secondary antibody
4. A solution is added to the well that contains a substrate, which can react to the enzyme attached to the secondary antibody and produce a coloured product. If the solution changes colour, HIV-specific antibodies are present and the patient is infected with HIV