Tumor necrosis factor is a substance produced by the immune system that intervenes primarily in the fight against cancerous cells. There are two types of tumor necrosis factors (TNF): TNFα (alpha) and TNFβ (beta). They are produced, respectively, by activated monocytes and by T lymphocytes, cells essential in the immune defense system. The two tumor necrosis factors are capable of destroying the tumors by engendering their necrosis. They are also involved in the inflammatory phase of an infection, hence the usage of anti-TNF intended to relieve inflammation.