Immunotherapy first began by Dr. William B. Coley in the 1890s. It is a type of biological therapy and is used to prevent and treat diseases such as cancer by using substances to stimulate one's immune response. Cells in the body are constantly changing to evade the immune system and antibodies are attached to antigens to alert other disease-fighting cells. Immunotherapy is classified into three categories: checkpoint inhibitors, which disrupts signals that allow cancer cells to hide from an immune attack; cytokines, are protein molecules that regulate and direct the immune system; and cancer vaccines, both treat and prevent development of a cancer. While going through immunotherapy, side effects to be aware of are: fatigue, fever, weakness, chills, muscle aches, shortness of breathe, etc. Cancers that can be treated with immunotherapy are: Bladder, Brain, Breast, Cervical, Childhood, Colorectal, Esophageal, Head and Neck, Kidney, Leukemia, Liver, Lung, Lymphoma, Melanoma, Multiple Myeloma, Ovarian, Pancreatic, Prostate, Sarcoma, and Stomach.