Explain how immune function relates to the development of cancer.

The immune system plays an important role in preventing and combating the diseases caused by pathogens as well as against abnormal cells present in the body such as cancerous cells. Normal cells have a limited life span and once they undergo apoptosis, new cells replace them through cell division and differentiation. This process is under control of several factors that keep a check on the number of cells so that it remains constant by the contact inhibition ( a property of normal cells). Cancerous cells seem to have lost this property and thus they do not respond to the normal growth control mechanisms of the body. Unregulated growth of these cancerous cells for tumors or neoplasm.

The immune cells such as T cells are capable of detecting the abnormalities and mark the abnormal cells as non-self or foreign cells. The abnormal cells are eliminated by the immune system but in some cases, the mutated cells are able to escape from the immunosurveillance of the immune system and continue their proliferation as cancer cells. These cancerous cells may do so by producing chemicals that act as immunosuppressants thus inhibit the immune responses. Some other cancerous cells are able to produce antigens on their cell surface which make them resemble self cells but once these antigens are no longer present on the surface of the cells, natural killer cells kill these abnormal cells.