A type of treatment that uses substances made from living organisms to treat disease. These substances may occur naturally in the body or may be made in the laboratory. Some stimulate or suppress the immune system to help the body fight cancer, infection, and other diseases. Other attack specific cancer cells, which may help keep them from growing or kill them. They may also lessen certain side effects caused by some cancer treatments. Types of include immunotherapy (such as vaccines, cytokines, and some antibodies), gene therapy, and some targeted therapies.