Monoclonal Antibodies in Medical Diagnosis

Turning specific binding into a diagnosis

Antibodies recognise particular antigens by binding to them. Monoclonal antibodies are identical copies that bind to the same chosen target. This makes them useful for finding where a target is in the body: if a detectable label is attached to the antibodies, its position can be found with a scan.

For this type of imaging, a radioactive substance is attached to a monoclonal antibody. The labelled antibodies are put into the bloodstream and travel around the body. Where they meet their matching target, some bind and the radioactive label can be detected by a scanner. The resulting image helps show the target’s position. The antibody provides the specific binding; the label provides the detectable signal.

Locating a blood clot

A blood clot contains proteins that can be targeted by a suitable monoclonal antibody. Labelled antibodies travelling in the blood bind to those proteins at the clot. A scan detects the label concentrated there, helping doctors locate the clot. The scan is locating it, not removing it.

Locating cancer cells

Some cancer cells have distinctive surface antigens, often called tumour markers. A monoclonal antibody chosen to bind to one of these markers can carry a radioactive label to cells bearing it. Where labelled antibodies collect, a scan can help show the position of those cancer cells. This can help doctors investigate where a cancer is and plan further care. The same principle—matching target, binding and detection—explains both diagnostic uses, although the antibody must be chosen for the particular target.

Diagnostic principle

Choose a monoclonal antibody that binds the target antigen → attach a radioactive label → give the labelled antibody → scan for where the label collects.

Targets

Blood clot: antibodies bind targeted clot proteins, helping locate the clot.

Cancer cells: antibodies bind a chosen tumour marker, helping locate cells bearing it.

In both cases the scan provides information about position; diagnosis is not itself treatment.