By Lila Havens, Staff Writer, myOptumHealth

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Immunotherapy is a type of treatment that uses the immune system to fight cancer. The idea of immunotherapy has been around for a long time, but it has become a reality in recent decades. Now, it's one of the most exciting areas in cancer research.

Immunotherapy may also be called biological therapy or biotherapy.

Related link: A Guide to Cancer Treatment 

How does the immune system work?
The immune system is your body's natural defense system. Its job is to defend you against invading germs that could make you sick. Germs have substances on their surface that the immune system recognizes as foreign. These substances (called antigens) trigger the immune system to attack.

The immune system response is a coordinated effort by different types of cells. Most of them are white blood cells, or lymphocytes. They travel through the blood and lymph system on the alert for antigens. When antigens are present:

• Antigen-presenting cells help the lymphocytes find the antigens.
• B lymphocytes make sticky proteins called antibodies. These lock onto the antigens and help destroy them.
• T lymphocytes can help B lymphocytes and can also kill the affected cells.

Why doesn't the immune system kill cancer cells?
Germs are very different from normal human cells. Cancer cells are also different. But since they start in your own body, they may not be different enough for the immune system to recognize them as foreign. Or they may give off substances that reduce the immune system response.

Related link: Treating Skin Cancer 

That's where immunotherapy comes in. Scientists are finding ways to help the immune system recognize cancer cells and have a stronger response to them.

Are there different types of immunotherapy?
The three types of immunotherapy are:

• Passive. In this type, antibodies are made in a lab and put into your body. Monoclonal antibodies are a kind of passive immunotherapy. Trastuzumab (Herceptin) is an example of a monoclonal antibody that is used to treat breast cancer.
• Active. This type stimulates your body's immune system to work harder. Cancer vaccines are active immunotherapy, because they trigger the body's immune system to attack cancer cells. So far, no cancer vaccines have been approved, but many types are being studied in clinical trials.
• Nonspecific therapies. These boost the immune system in a general way. They may be used alone to fight cancer or they may be given along with other treatments. Often, they are used to reduce the side effects of chemotherapy. Interleukin-2 (IL-2) is a type of nonspecific immunotherapy that is used to treat kidney cancer and melanoma.

What types of cancer can be treated with immunotherapy?
Scientists are studying immunotherapy as a treatment for many types of cancer. It offers hope for people with cancers that don't respond well to chemotherapy and other treatments.

Related link: Treating Colon Cancer 

So far, the U.S. Food and Drug Administration (FDA) has approved immunotherapy to treat:

• Melanoma skin cancer
• Colorectal cancer
• Breast cancer
• Cervical cancer
• Lung cancer
• Kidney cancer
• Blood cancers such as leukemia and lymphoma

Your doctor can tell you if immunotherapy is an option for you. If it has not been approved for your type of cancer, you might be able to enroll in a clinical trial. Clinical trials to study new types of immunotherapy are being done at sites all over the country.

Related link: Basics of Kidney Cancer (Renal Cell Carcinoma): Symptoms