肿瘤坏死因子相关凋亡诱导配体(TRAIL)是肿瘤坏死因子(TNF)超家族的一员，属于Ⅱ型跨膜蛋白，表达于人类T淋巴细胞、NK细胞、单核细胞、鼠T或B细胞以及其它一些细胞和组织。它能诱导突变的T细胞、肿瘤细胞及病毒转染的细胞凋亡。
本试剂盒应用双抗体夹心酶标免疫分析法测定标本中sTRAIL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sTRAIL抗原、生物素化的抗人sTRAIL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sTRAIL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 soluble tumor necrosis factor-related apoptosis inducing ligand（sTRAIL） concentrations in cell culture supernates, serum, and plasma.
Introduction
TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is a recently identified member of the TNF gene superfamily. Five different receptors have been identified for TRAIL. Two receptors, DR4 and DR5, are transmembrane proteins containing death domain similar to FAS and other TNF family receptors. Two other receptors, DcR1 and DcR2, act like decoy proteins for TRAIL binding because they lack the death domain. TRAIL can also bind, though weakly, to osteoprotegrin (OPG), a soluble receptor, which plays a role in osteoclastogenesis. TRAIL induces apoptosis in various tumor cell lines, whereas most primary cells seem to be resistant. TRAIL-mediated apoptosis occurs following its binding to DR4 or DR5 receptors. The mechanism of apoptosis involves activation of caspase-8 and subsequent activation of effector caspases. Also, NF-κB and JNK activation play a role in the TRAIL signaling pathway.TRAIL expression is detectable in many normal organs and tissues. Several studies suggest that TRAIL may play a physiological role by contributing to immune privilege, normal cellular development, and inhibition of autoimmune responses. The expression of TRAIL is upregulated in activated T cells, B cells, NK cells, monocytes and macrophages. LPS activation stimulates the release of soluble TRAIL from monocytes and macrophages, suggesting a role of TRAIL in their cytotoxic/phagocytic function. Also, TRAIL expression is increased in transformed cell lines and various diseases including cancer and autoimmune disorders. TRAIL may also be involved in
activation-induced T cell death during HIV infection. Certain anti-cancer agents also upregulate TRAIL and TRAIL receptor expression on tumor cells, thus sensitizing cells to apoptosis.
Test principle
This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for sTRAIL has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any sTRAIL present is bound by the immobilized antibody. An enzyme-linked monoclonal antibody specific for sTRAIL 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 sTRAIL bound in the initial step. The color development is stopped and the intensity of the color is measured.
