Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Immunotherapy

What Is It?

Immunotherapy refers to treatments that stimulate, enhance or suppress the body's own immune system.

Immunotherapy is also called:

• Biological therapy

• Biotherapy

• Biological response modifier therapy

Immunotherapy is used to treat certain types of cancer. It is also used to treat inflammatory diseases. These include:

• Rheumatoid arthritis

• Crohn's disease

• Multiple sclerosis

Our body's immune system recognizes cancer cells as foreign or abnormal. Unlike normal cells, cancer cells have unique proteins (antigens) on their outer surface. Antibodies are proteins produced by the immune system. They latch onto the cancer cells' antigens. In this way, they label or tag the abnormal cells.

Ideally, special cells in the immune system would be recruited to destroy the tagged cancer cells. Sometimes, however, the immune system needs some help.

Biological therapy helps to stimulate the immune system to fight cancer. The chemicals used in immunotherapy often are called biological response modifiers. They enhance the body's normal immune-system reaction to a cancer threat.

Some biological response modifiers are chemicals that occur naturally in the body. But they are produced in larger amounts in a laboratory to help boost a person's immune response.

Biological response modifiers can play many different roles in fighting cancer. For example, they can:

• Recruit more immune system cells to attack a tumor

• Make cancer cells more vulnerable to an attack by the immune system

• Change the way cancer cells grow

• Coax cancer cells into behaving more like normal cells

Immunotherapy also can be used to suppress the immune system. This is particularly helpful in autoimmune disorders. In these disorders, the immune system "misfires." It wrongly attacks normal tissues.

Inflammation is useful for fighting infection. But in autoimmune diseases, it damages normal tissues. Biological therapies can cool off this harmful inflammation.

Examples of biological therapies currently in use include:

• Interferons. Boost the body's immune response. They also can act directly on cancer cells to control their rapid growth.

• Interleukins. Stimulate growth of the body's immune cells, especially lymphocytes. Lymphocytes are a type of white blood cell.

• Colony stimulating factors (CSFs). Encourage the growth of bone marrow stem cells. Bone-marrow stem cells, especially white blood cells, are needed to fight infections. But they often are destroyed by cancer treatments such as chemotherapy or radiation.

  CSFs are used after other cancer therapies. They help to grow a new population of cells in the blood.

• Monoclonal antibodies. These are made in a laboratory. They recognize the antigens on the surface of cancer cells.

  Monoclonal antibodies can be used alone. Or they can be linked to anti-cancer drugs or to radioactive substances. They can carry these linked poisons directly to tumor cells inside the body.

  Some antibodies acting alone can significantly interfere with cancer cells. They can stop them from growing. Or they can cause them to be destroyed by the body's immune system. Monoclonal antibodies spare the body's normal cells.

  Monoclonal antibodies also may help people with autoimmune diseases. They target immune cells or chemical messengers involved in inflammation. Monoclonal antibodies may reduce pain and improve joint function in people with rheumatoid arthritis.