Tumor immunity is the immune system's response to tumors, abnormal cell growths arising in the body. There is some scientific evidence to support theories that the body has some natural tumor immunity, depending on the type of tumor involved, as some tumors can spontaneously regress without medical treatment. Studying the way the immune system interacts with tumors is an important aspect of developing appropriate treatments for tumors, including treatments designed to enhance immune responses to more effectively combat tumors from within.
From an immunologist's perspective, the problem with tumors is their composition. Tumors are made up of natural cells growing out of control. The immune system is designed to ignore cells from within the body, and during the maturation of immune cells, cells targeting the body's own tissues are usually destroyed, although there are usually a handful of survivors. As a result, when immune cells are exposed to tumors, most do not react, because they don't see anything abnormal. The handful of cells that do are not numerous enough to kill the tumor.
Researchers have identified a number of tumor antigens, chemicals found on the surface of tumors with the potential to interact with the immune system. Tumor immunity is based on reacting to those antigens and targeting a tumor for destruction. Tumors with antigens the body recognizes as harmful will be attacked by the immune system, although it may not be able to completely destroy them. In other cases, the immune response is highly effective and a patch of malignant growth is destroyed before it has a chance to develop into a full-blown tumor.
Immunity is achieved in a number of different ways, including through exposure to antigens, as seen with vaccination, where small amounts of antigens are introduced into the body to teach the immune system to recognize them. In the case of tumor immunity, the primary area of interest is the normal antigens expressed in excess on a tumor. Teaching the immune system to differentiate between healthy body cells and cancerous ones might be possible by getting immune cells to target cells that are overexpressing.
Another area of research in the field of tumor immunity has been the possibility of using medications to tag overexpressing cells. The tags are identified by the immune system as dangerous, and it will attack the attached cells, breaking down the tumor. This requires successful diagnosis and typing of a tumor, preferably in the early stages, before it has an opportunity to become highly invasive.