Tumor necrosis factor (TNF) is mainly produced by activated macrophages, NK cells, and T lymphocytes. In 1985, Shalaby named the TNF produced by macrophages TNF- α， Name the lymphotoxin (LT) produced by T lymphocytes as TNF- β。 Although TNF- α And TNF- β They have only about 30% homology, but they share a common receptor. Tumor necrosis factor (TNF) is mainly produced by activated macrophages, NK cells, and T lymphocytes. In 1985, Shalaby named the TNF produced by macrophages TNF- α， Name the lymphotoxin (LT) produced by T lymphocytes as TNF- β。 Although TNF- α And TNF- β They have only about 30% homology, but they share a common receptor. TNF α The biological activity of TNF accounts for 70% to 95% of the total activity of TNF, so the commonly used term TNF currently refers to TNF- α Human TNF- α The precursor consists of 233 amino acids (26kDa), including a signal peptide composed of 76 amino acid residues. Under the action of TNF converting enzyme TACE, the signal peptide is cleaved to form a mature TNF with 157 amino acid residues- α (17 kDa). Due to the absence of methionine residues, there is no glycosylation site, where the two cysteine residues at positions 69 and 101 form intramolecular disulfide bonds. Human TNF- α TNF in mice- α 79% amino acid composition homology, TNF- α There seems to be no significant species specificity in its biological effects.