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预期应用
ELISA法定量测定人血浆、细胞培养物上清或其它相关液体中TFPI含量。
实验原理
本试剂盒应用双抗体夹心酶标免疫分析法测定标本中TFPI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TFPI抗原、生物素化的抗人TFPI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TFPI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 TFPI concentrations in plasma and cell culture supernates.
Introduction
In plasma, Tissue Factor Pathway Inhibitor (TFPI) is found in several forms: one at 36,000 kD, one at 43,000 kD, and the various truncated forms. This size heterogeneity appears in part to be the result of the formation of mixed disulfide complexes between TFPI and apolipoprotein AII. Approximately 10% of total TFPI is carried by platelets, which release TFPI once they are activated by thrombin. Thus, at the site of a wound, where platelets aggregate, elevated levels of TFPI are present. TFPI has dual inhibitory function (against factor Xa and factor VIIa/TF). This is consistent with the presence of multiple Kunitz-type domains: (Kunitz for factor VIIa/TF and Kunitz for factor Xa interaction). Based on the initial isolation of the inhibitor, it was found that TFPI inhibits factor VIIa/TF and directly inhibits factor Xa by binding at or near its serine active site. The mechanism of action for factor Xa dependent inhibition of factor VIIa/TF by TFPI involves the formation of a quaternary factor Xa/TFPI/factor VIIa/TF complex. This results from the initial binding of factor Xa to TFPI, with subsequent binding of the factor Xa-TFPI complex to factor VIIa/TF. Alternatively, TFPI might bind to the factor Xa-VIIa/TF complex. Quantitation of TFPI, with its dual inhibitory role against factor Xa and factor VIIa/TF, offers insight into the mechanism of disseminated intravascular coagulation (DIC) triggered by tissue factor. It has been observed that infusion of TFPI abrogates DIC and prevents reocclusion following thrombolysis induced by injury. Clinical conditions in which thrombosis appears to be initiated by TF and in which TFPI treatment may be potentially useful include sepsis, inflammatory disease and transplant rejection. TFPI has potential as an antithrombotic agent.
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