Cancer immunotherapy is the use of the
immune system to treat
cancer. Immunotherapies are often categorized as active, passive, or combinatory (active and passive). These immunotherapeutic approaches exploit the fact that
cancer cells often have subtly different molecules on their surface that can be detected by the immune system known as
cancer antigens; cancer antigens are often
proteins or other macromolecules (e.g.
carbohydrates).