Cell Recognition and the Immune System- Antibodies

Question 1

What are monoclonal antibodies?

Answer 1

Antibodies produced from a single group of genetically identical B cells which means they’re all identical in structure

Question 2

Why are antibodies very specific?

Answer 2

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

Question 3

How are antibodies used in targeting drugs to cancer cells?

Answer 3

1. Cancer cells have antigens called tumour markers
2. Monoclonal antibodies are found that will bind to tumour markers
3. Can also attach anti-cancer drugs to antibodies
4. Antibodies will bind with tumour markers when they come into contact with cells
5. Drug will only accumulate where there are cancer cells
6. Side effects of antibody-based drugs are lower than other drugs as they accumulate near specific cells

Question 4

How are antibodies used in pregnancy testing?

Answer 4

1. Application area contains antibodies for hCG bound to blue coloured beads
2. hCG will bind to antibody when urine is applied and an antigen-antibody complex
3. Urine moves up stick to test strip and carries any beads with it
4. Test strip contains antibodies to hCG that are stuck in place (immobilised)
5. If hCG is present then test strip turns blue due to hCG binding to immobilised antibody
6. If no hCG is present then beads will pass through the test area without binding so no colour change

Question 5

What is the purpose of the ELISA (enzyme-linked immunosorbent assay) test?

Answer 5

Allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody

Question 6

What can the ELISA test be used for?

Answer 6

Testing for pathogenic infections, allergies, and anything you can make an antibody for

Question 7

What happens in the ELISA test?

Answer 7

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

Question 8

What does it mean if there’s a colour change in the ELISA test?

Answer 8

It demonstrates that the antigen or antibody of interest is present in the sample being tested

Question 9

How can the quantity of antigen/antibody be worked out in the ELISA test?

Answer 9

From the intensity of the colour change

Question 10

What is the direct ELISA test?

Answer 10

Uses a single antibody that is complementary to the antigen you’re testing for

Question 11

What is the indirect ELISA test?

Answer 11

Uses two antibodies

Question 12

How can an indirect ELISA test be used as an HIV test?

Answer 12

1. HIV antigen bound to the bottom of a well in a well plate
2. Sample of patient’s blood plasma added to the well
3. Any HIV-specific antibodies will bind to HIV antigen stuck to well
4. Well is washed out to remove any unbound antibodies
5. Secondary antibody with a specific enzyme attached is added to well
6. Secondary antibody can bind to HIV-specific antibody
7. Well is washed out to remove any unbound secondary antibody (secondary antibody is washed away if there’s no primary antibody bound)
8. Solution that contains substrate added to well and substrate can bind to enzyme and cause colour change