Immunotherapy is a cancer treatment that uses your own immune system to fight your cancer. Your immune system consists of cells, tissues, and organs that protect your body from illness and infection.
The immune system works through a series of actions called the immune response. In the immune response:
Your immune system often naturally recognizes cancer cells as harmful. If it does, then it attacks and destroys them. We never even notice many tiny cancers that are quickly destroyed right after they start. However, once a cancer has become big enough to cause symptoms, it's likely that your immune system can't fight it off anymore. That's why doctors have come up with ways to help your immune system fight your cancer.
There are several different ways doctors can boost your immune response to help your body fight your cancer. Doctors may:
Give you laboratory-made versions of antibodies to target and destroy cancer cells.
Take cells (white blood cells) from your own immune system, multiply them in the lab, and give them back to you
Give you substances that make your immune system better at finding and killing your specific cancer cells
Give you medicines that can weaken the defenses cancer cells have to protect them from the immune system
When doctors use cells from your own immune system, sometimes they use cells that already know how to attack the cancer, and sometimes they modify the cells to be more effective. Most immunotherapies work on only a few types of cancer.