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What are monoclonal antibodies?

A mouse is injected with the antigen for which the scientist needs a matching antibody. White blood cells are collected from the mouse. They are screened to find one making the right kind of antibody and then that cell is cultured. The white blood cells continue dividing until there are many of them. The cell culture continues to make antibodies, which are harvested. They are called monoclonal antibodies because they all come from the same white blood cell clone. This also means that the antibodies are all identical.

Using monoclonal antibodies to diagnose disease

Monoclonal antibodies can be made to match any antigen. It may be an antigen on the outside of a pathogen cell, an antigen on a diseased cell, or an antigen which is made by cells. An antibody will only match one antigen.

Monoclonal antibodies are very specific, and so the chance of false test results is fairly low. They have been used not only to help diagnose infectious diseases caused by bacteria, viruses and protozoa but also to diagnose cancer and metabolic and hormonal disorders.

Monoclonal antibodies may be attached to substances which are radioactive or toxic in order to kill cancer cells. Sometimes enzymes are attached to antibodies - these activate inactive medicines when they are near the cancer cell.

Antibodies may be attached to a fluorescent marker in order to make the diseased cells easily visible.

Cancer diagnosis and treatment

Cancerous cells often have antigens which are unique to them. Monoclonal antibodies can be designed to bind specifically with these antigens. When injected into a person's blood, the monoclonal antibodies will bind with these cancer cells and clump them together. This makes it easier to identify a cancerous tumour, which can then be treated or removed.

The traditional treatments for cancer are chemotherapy and radiotherapy. The medicines used for chemotherapy are toxic to cells. The faster the cell is dividing the more toxic the chemicals are - this means that cancer cells are the most susceptible to the medicine. Other rapidly dividing cells such as those in our bones, digestive system and hair follicles can also be harmed. This causes unpleasant side-effects. Radiotherapy is useful for treating some cancers, and new technologies can focus electromagnetic waves so that damage to healthy tissue is limited. The treatment can only be effective if the cancerous tumour cells have not migrated to different parts of the body, so early diagnosis is essential.

For this reason scientists have for years been looking for a way of turning chemotherapy medicines into 'magic bullets' which will target the diseased cells but not harm normal cells. Many think that monoclonal antibodies might be important in achieving this.

Monoclonal antibody therapy

Monoclonal antibodies have been designed to treat cancer by:

• carrying drugs that have been attached to them, to the tumour
• encouraging the immune system to attack the cancer cells directly

Learn more about monoclonal antibodies with Dr Alex Lathbridge.

Listen to the full series on ����ý Sounds.