Monoclonal antibodies

What are monoclonal antibodies

• Monoclonal antibodies are antibodies that have come from a single clone of plasma cells

  • This means that they are identical antibodies that are complimentary to a single, specific antigen

What are the uses of monoclonal antibodies

• Pregnancy testing - targeting a particular substance for medical diagnosis

• Cancer cells - targeting drugs to a specific cell type

• Drug delivery - bind to specific cells, bringing therapeutic drugs with them

• Diagnosis of disease - bind to specific cell types to identify infected cells

Provide ane example of where monoclonal antibodies can be used in immunoassay

Monoclonal antibodies that are specific for particular antigens can be used in immunoassay (to measure the concentration of something) ,for example to find out the concentration of antibodies a patient has in their blood or the level of a specific hormones for example hCG detected in pregnancy tests

Explain how monolconal antibodies work

• The application area/ reaction site contains free antibodies for hCG bound to a colored bead/dye (blue)

• When urine, which contains the hormone hCG, is applied to the application area any hCG will bind to the antibody on the dye forming an antigen-antibody complex

• The urine moves up the stick to the test strip, carrying any dye with it

• The test site contains fixed antibodies to hCG

• If hCG is present the test strip turns blue because the immobilised antibody binds to any hCG  - concentrating the hCG-antibody complex with the blue dye attached

  • If no hCG is present, the beads will pass through the test area without binding to anything, and so won’t go blue.

What does ELISA stand for

• ELISA stands for enzyme-linked immunosorbent assay

• ELISA allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody

  • It can be used to test for pathogenic infections, for allergies and for just about anything you can make an antibody for 

Stage 1 of ELISA

• Add the sample (containing the target protein so in this case is the HIV antigen) to a well plate where the target protein can attach to the well

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

Stage 2 of ELISA

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

  • If there is no primary antibody in the sample, all of the secondary antibody will be washed away

Stage 3 of ELISA

• A solution is added to the well. This solution 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

Why are the washing steps important

• The washing steps are important to make sure unbound antibodies aren’t left in the well which could affect the results e.g. unbound secondary antibodies could cause the test to appear positive when there are no HIV antibodies present

How can monoclonal antibodies target cancer cells

• One use of monoclonal antibodies is to target medication to one specific cell type 

• Different cells in the body have different surface antigens

• Cancer cells have antigens called tumour markers that are not found on normal body cells so monoclonal antibodies can be made that will bind to the tumour markers

What can you attach to the monolconal antibodies to kill the cancer cells and what is the effect of this?

• You can then attach a therapeutic drug/anti-cancer drug  to the antibodies so when the antibodies come into contact with the cancer cells they will bind to the tumour markers

  • This means that the drug will only accumulate in the body where there are cancer cells. Therefore the side effects of any antibody-based drug are because the drug only accumulates near specific cells

What are the ethical issues of monoclonal antibodies

• There are some ethical issues involved with monoclonal antibody production:

• It involves the use of mice and to produce cells that multiply and produce antibodies, cancer cells are needed as well as plasma cells

  • So deliberately inducing cancer in mice (cause suffering or harm to the mice)

• To make the antibodies suitable for use in humans, transgenic mice are used which is where a human gene is inserted into the mice by genetic engineering

  • Some people have ethical objections to the use of genetic engineering

• Monoclonal antibody treatments are often expensive which raises concerns about fair access, especially in lower-income countries or healthcare systems

• Monoclonal antibodies are used to successfully treat many diseases but they may have serious side effects