Pregnancy tests

Appliance of antibodies

We can exploit the ability of antibodies to bind to a specific antigen

Monoclonal antibodies (mAbs) are sets of identical antibodies that come from genetically identical immune cells and all bind to the same substance. Drug developers use them to create drugs capable of targeting specific types of cells.

Diagram of an antibody

Annotated diagram of an antibody:

A. Antigen binding sites
B. Variable region
C. Constant region
D. Heavy chain
E. Disulphide bridge
F. Light chain


‘Big Picture: Immune System’

The breast cancer drug Herceptin (trastuzumab) is a monoclonal antibody that specifically targets breast cancer cells by binding to a protein called HER2 on the surface of the cells. The HER2 protein drives the growth of cancer cells and Herceptin blocks that growth.

Antibodies (see annotated image) can also be used in test kits. The pregnancy test, for example, uses an antibody to bind and detect in blood or urine a hormone called human chorionic gonadotropin, which is produced in early pregnancy.

If you have been infected by a particular virus, say, you will have antibodies against it in your body, so monoclonal antibodies are also useful in diagnostic tests. One of the most common methods of detecting HIV uses an antibody-based test called an ELISA – an enzyme-linked immunosorbent assay. It is more accurate a few weeks after initial infection, because it takes a while for the body to build up antibodies against the virus. So early tests are often repeated or alternative methods are used to confirm the diagnosis.

Lead image:

mob mob/Flickr CC BY NC ND


Downloadable resources

About this resource

This resource was first published in ‘Immune System’ in January 2015.

Health, infection and disease, Immunology
Immune System
Education levels:
16–19, Continuing professional development