Monoclonal Antibodies Revision notes | A-Level Biology AQA

Monoclonal Antibodies

This lesson covers:

What monoclonal antibodies are
The uses of monoclonal antibodies in medicine
The use of antibodies in the ELISA test

Monoclonal antibodies

Monoclonal antibodies are antibodies produced from a single clone of plasma cells:

'Mono' means single.
'Clonal' means clone.

Each of these antibodies are identical to one another and so will bind to a specific molecule.

Monoclonal antibodies have many uses:

Diagnosis of disease - Monoclonal antibodies bind to specific cell types to identify infected cells.
Treatment of disease - Monoclonal antibodies bind to specific cells, bringing therapeutic drugs with them.
Pregnancy testing - Monoclonal antibodies bind to a pregnancy hormone in home pregnancy testing kits.
Detecting certain cancers - For example, monoclonal antibodies can bind to prostate specific antigens (PSA) to identify prostate cancer in men.

ELISA test

The Enzyme-Linked ImmunoSorbant Assay (ELISA) test uses monoclonal antibodies to to detect both the presence and quantity of protein in a sample. It is often used to find out whether a patient has antigens for a pathogen, and hence has the disease.

There are two types of ELISA test:

The direct test - This uses only one antibody.
The indirect test - This uses two antibodies.

The following steps outline how the indirect ELISA test is carried out:

Diagram showing the process of the indirect ELISA test with multiple steps involving target protein and antibodies.

Add the sample (containing the target protein) to a well plate where the target protein can attach to the well.

Diagram showing the process of the ELISA test with antibodies binding to target proteins and a pipette adding a solution.

Add the antibody that is specific to the target protein. These antibodies will bind to the target proteins attached to the well.

Diagram showing the steps of the indirect ELISA test, including binding of antibodies and washing out unbound antibodies.

Wash the well to remove any unbound antibodies.

Diagram showing the process of the indirect ELISA test with antibodies and enzyme attachment.

Add a second antibody that will bind to the first antibody. These secondary antibodies are attached to an enzyme.

Diagram showing the steps of the indirect ELISA test including antibody binding and washing.

Wash the well again to remove any unbound secondary antibody.

Diagram showing the steps of the indirect ELISA test process including antibody binding and colour change.

Add a solution containing substrate to the well. The enzyme attached to the second antibody will act on the substrate to cause a colour change. The intensity of the colour indicates the quantity of protein present.