肿瘤坏死因子(tumornecrosisfactor，TNF)是一种具有多种生物活性的细胞因子。人TNF-α基因编码前体蛋白，其信号肽将前体蛋白固定在细胞膜上，成为具有活性的跨膜干扰素(TNF)，分子质量为26×103，经酶切去除信号肽生成分泌型TNF-α，分子质量为17×103。TNF-α细胞来源广泛，包括各种免疫细胞、内皮细胞、成纤维细胞、表皮细胞、角质细胞、平滑肌细胞、星形细胞、成骨细胞等。
本试剂盒应用双抗体夹心酶标免疫分析法测定标本中TNF-α水平。用纯化的抗体包被微孔板，制成固相抗体，往包被单抗的微孔中依次加入TNF-α抗原、生物素化的抗大鼠TNF-α抗体、HRP标记的亲和素，经过彻底洗涤后用底物TMB显色。TMB在过氧化物酶的催化下转化成蓝色，并在酸的作用下转化成最终的黄色。颜色的深浅和样品中的TNF-α呈正相关。用酶标仪在450nm波长下测定吸光度（OD值），计算样品浓度。
Intended use
This immunoassay kit allows for the specific measurement of human TNF-α concentrations in cell culture supernates, serum, sputum, and plasma.
Introduction
The prototype ligand of the TNF superfamily, TNF-α/TNFSF1A, is a pleiotropic cytokine that plays a central role in inflammation and apoptosis. It is synthesized as a 26 kDa, type II transmembrane protein that is 233 amino acids in length. It contains a 30 amino acid (aa) cytoplasmic domain, a 26 aa transmembrane segment, and a 177 aa extracellular region. TNF-αis assembled intracellularly to form a transmembrane, non-covalently-linked homotrimeric protein. The 157 aa residue soluble form of TNF-α(sTNF-αis released from the C-terminus of the transmembrane protein through the activity of TNF-α-converting enzyme (TACE), a membrane -bound disintegrin metalloproteinase. Human cells known to express TNF-αinclude B cells, colonic columnar epithelial cells, NK and CD3+CD56+ hepatic natural T cells, macrophages, monocytes and monocyte-derived dendritic cells, CD4+ and CD8+ T cells, mast cells, neutrophils, keratinocytes, plasma cells, and adipocytes.
Test principle
This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for TNF-α has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any TNF-α present is bound by the immobilized antibody. An enzyme-linked monoclonal antibody specific for TNF-α is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of TNF-α bound in the initial step. The color development is stopped and the intensity of the color is measured.
