An overactive immune system over the long term may be a significant factor in the development of cancer.
Researchers at the University of Leicester say that, while cancer may have a variety of causes, many of these ultimately work in the same way - by switching on the immune system for too long. When the immune system is activated in this way, it can lead to inflammation of the tissues, which may play a role in the development of cancer.
The inflammatory process may initiate cancer in many ways. Immune cells that would normally kill cancer cells may be switched off. Blood vessel growth is stimulated, providing nutrition for cancer cells. Production of oxygen-reactive species is increased, leading to DNA damage and mutations.
What triggers the process is still not clear, although it could be long-term exposure to a carcinogenic chemical or infection. When this happens, the immune system loses its ability to fight disease, and may instead begin to nurture and protect young cancer cells (Br J Cancer, 2001; 85: 473-83).