Immunotherapy, also called biologic therapy, uses the body’s own immune system to fight cancer cells or protect the body from side effects. Immunotherapy relies on antibodies, naturally occurring proteins dedicated to defending the body against invasion by foreign substances. In one kind of immunotherapy, antibodies are used to attack tumor cells directly, while in another approach, antibodies are used to deliver toxic agents, such as radioactive substances or drugs, that selectively target and harm cancer cells. Monoclonal antibodies are laboratory-produced antibodies used to fight many diseases, including cancer. One of the newest treatments for breast cancer is a monoclonal antibody called Herceptin, which targets cancer cells that overproduce HER-2, the protein implicated in about one-third of all breast cancers.
In the creation of a monoclonal antibody, a normal B cell (a type of lymphocyte, or white blood cell) is united with a myeloma cell (a type of cancer). This union results in the formation of hybridomas (hybrid cells) that have the cancer cell’s trait of dividing endlessly and the B cell’s ability to produce a specific type of antibody. Monoclonal antibodies are designed to target specific molecules in the body. They have a variety of uses from pregnancy testing to treating certain cancers.
Other forms of immunotherapy include the use of interferon, a naturally and synthetically produced protein that fights disease-causing agents in the body, particularly viruses. Interferons slow the growth of tumor cells in some patients, and they stimulate the immune system to attack cancerous cells. Another therapy, interleukin-2, is a naturally occurring immune system chemical that stimulates a type of immune cell that attacks cancer cells. Colony stimulating factors help regulate the production of white blood cells, enabling the body to better combat the disease.
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