Biotherapy is a form of treatment that uses the natural immune system to protect the body against infection, cancer, and other diseases, and can fortify the body against some side-effects of other treatments. Biotherapy employs substances called biological response modifiers (BRMs), which include vaccines, monoclonal antibodies, cytokines, and adjuvants. BRMs are used alone or in combination with each other. Several BRMs are widely accepted in the treatment of certain types of cancer, while others are being tried in research studies. Side-effects of biotherapy vary among agents and patients. However, these side-effects usually disappear after the end of treatment.