Tumor necrosis factor alpha (TNF-α), belongs to the superfamily of TNF/TNFR cytokine superfamily, is a type II transmembrane protein (mTNF) with an intracellular N terminus that is produced as 26 kDa membrane-bound cytokine comprised of 233 amino acids. TNF-α also exists as a soluble cytokine (sTNF), which is a non-covalently bound 17 kDa trimer (157 amino acids with a 76 amino acid presequence) resulted from the cleavage of mTNF by TNF-α converting enzyme (TACE). Two distinct and highly affinitive receptors of TNF-α have been identified, including TNFR55 (a 55 kDa receptor) and TNFR75 (a 75 kDa receptor), through which multiple activities of TNF-α are mediated. TNF-α has been found to be involved in maintenance and homeostasis of the immune system, inflammation and host defence as well as a variety of pathological processes.