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TNFa (Tissue Necrosis Factor alpha)
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Tumor necrosis factor α (TNF-α), also known as cachectin, and tumor necrosis factor β (TNF-β) also known as lymphotoxin, are two closely related proteins (about 34% amino acid residue homology) that bind to the same cell surface receptors and produce a vast range of similar, but not identical, effects. In contrast to the similarity of their biological activities, the regulation of the expression and processing of the two factors is quite different. TNF-α is produced by neutrophils, activated T and B lymphocytes, NK cells, LAK cells, astrocytes, endothelial cells, smooth muscle cells, and some transformed cells. TNF-β is produced by lymphocytes.
Mature human TNF-α is a polypeptide of 157 amino acid residues. The apparent molecular weight of human TNF-α under denaturing conditions is approximately 17 kDa.
The two TNFs are extremely pleiotropic factors. TNFs play a critical role in normal host resistance to infections and to the growth of malignant tumors, serving as immunostimulants and as mediators of the inflammatory response. Many of the actions produced by the TNFs are functionally similar to the effects produced by IL-1. On the other hand, over-production of TNF has been implicated as playing a role in a number of pathological conditions, including cachexia (progressive wasting), septic shock following infection with Gram-negative bacteria, autoimmune disorders, and meningococcal septicemia.
The TNF-α assay is a solid-phase ELISA desinged to quantitate TNF-α in cell supernates, serum and plama. The assay employs the quantitative sandwich enzyme immunoassay principle.