Cancer immunotherapy is a therapy used to treat cancer patients that involves or uses components of the immune system. Some cancer immunotherapies consist of antibodies that bind to, and inhibit the function of, proteins expressed by cancer cells. Other cancer immunotherapies include vaccines and T cell infusions.Immunotherapies against existing cancers include various approaches, ranging from stimulating effector mechanisms to counteracting inhibitory. Cancer immunotherapy consists of approaches that modify the host immune system, and/or the utilization of components of the immune system, as cancer treatment. During the past 25 years, 17 immunologic products have received regulatory approval based on anticancer activity as single agents and/or in combination with chemotherapy. The anti-CTLA-4 monoclonal antibody ipilumumab, which blocks regulatory T-cells, is expected to receive regulatory approval in the near future, based on a randomized trial in melanoma. As the fourth modality of cancer treatment, biotherapy/immunotherapy is an increasingly important component of the anticancer armamentarium.Doctors don't yet use immunotherapy as often as other cancer treatments, such as surgery,chemotherapy, and radiation therapy. But they do use immunotherapy for some types of cancer, and researchers are doing clinical trials to see whether it also works for other types.