Feys H B, Liu F, Dong N, Pareyn I, Vauterin S, Vandeputte N, Noppe W, Ruan C, Deckmyn H, Vanhoorelbeke K
Laboratory for Thrombosis Research, IRC, K.U. Leuven Campus Kortrijk, E. Sabbelaan 53, 8500 Kortrijk, Belgium.
J Thromb Haemost. 2006 May;4(5):955-62. doi: 10.1111/j.1538-7836.2006.01833.x.
The recently discovered plasma enzyme ADAMTS-13 cleaves the A2-domain of von Willebrand factor (VWF). A defective cleaving protease results in unusually large VWF multimers, which cause thrombotic thrombocytopenic purpura (TTP).
Analysis of the ADAMTS-13 antigen levels in TTP patients compared with normal donors.
An antigen ELISA test was built, based on high affinity anti-ADAMTS-13 monoclonal antibodies, which were generated using genetic immunization.
Specificity of the ADAMTS-13 antigen test was confirmed, as (i) plasma from a patient with acquired TTP but presenting without inhibitor did not contain antigen and (ii) the binding of recombinant ADAMTS-13 was inhibited by increasing amounts of normal plasma. The assay is sensitive as it can detect antigen levels as low as 1.6% of normal. The concentration in normal pooled human plasma was determined (1.03 +/- 0.15 microg mL(-1)) and arbitrarily set to 1 U mL(-1). The antigen levels in congenital TTP samples (34 +/- 21 mU mL(-1), n = 2), as well as in samples from patients with acquired TTP (231 +/- 287 mU mL(-1), n = 11), were clearly reduced when compared with normal Caucasian donors (951 +/- 206 mU mL(-1), n = 16). Remarkably, normal Chinese donors have a significantly lower antigen titer (601 +/- 129 mU mL(-1), n = 15), when compared with normal Caucasians.
Our results show that acquired TTP patients suffer mainly from ADAMTS-13 antigen depletion, thereby indicating the importance of ADAMTS-13 antigen determination in diagnosis and patient follow-up.
最近发现的血浆酶ADAMTS - 13可切割血管性血友病因子（VWF）的A2结构域。有缺陷的切割蛋白酶会导致异常大的VWF多聚体，从而引发血栓性血小板减少性紫癜（TTP）。
分析TTP患者与正常供体相比的ADAMTS - 13抗原水平。
基于通过基因免疫产生的高亲和力抗ADAMTS - 13单克隆抗体建立了抗原ELISA检测法。
ADAMTS - 13抗原检测的特异性得到了证实，因为（i）一名获得性TTP但无抑制剂的患者血浆中不含抗原，以及（ii）重组ADAMTS - 13的结合受到正常血浆量增加的抑制。该检测方法很灵敏，因为它能检测到低至正常水平1.6%的抗原水平。测定了正常混合人血浆中的浓度（1.03±0.15μg mL⁻¹），并将其任意设定为1 U mL⁻¹。与正常白种人供体（951±206 mU mL⁻¹，n = 16）相比，先天性TTP样本（34±21 mU mL⁻¹，n = 2）以及获得性TTP患者样本（231±287 mU mL⁻¹，n = 11）中的抗原水平明显降低。值得注意的是，与正常白种人相比，正常中国供体的抗原滴度显著较低（601±129 mU mL⁻¹，n = 15）。
我们的结果表明，获得性TTP患者主要存在ADAMTS - 13抗原耗竭，从而表明ADAMTS - 13抗原测定在诊断和患者随访中的重要性。
