Premium
ADAMTS‐13 plasma level determination uncovers antigen absence in acquired thrombotic thrombocytopenic purpura and ethnic differences
Author(s) -
FEYS H. B.,
LIU F.,
DONG N.,
PAREYN I.,
VAUTERIN S.,
VANDEPUTTE N.,
NOPPE W.,
RUAN C.,
DECKMYN H.,
VANHOORELBEKE K.
Publication year - 2006
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/j.1538-7836.2006.01833.x
Subject(s) - antigen , thrombotic thrombocytopenic purpura , adamts , von willebrand factor , titer , adamts13 , monoclonal antibody , antibody , recombinant dna , microbiology and biotechnology , chemistry , medicine , immunology , platelet , metalloproteinase , enzyme , biology , biochemistry , thrombospondin , gene
Summary. Background: 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). Aim: Analysis of the ADAMTS‐13 antigen levels in TTP patients compared with normal donors. Methods: An antigen ELISA test was built, based on high affinity anti‐ADAMTS‐13 monoclonal antibodies, which were generated using genetic immunization. Results: 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 μ g 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. Conclusions: 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.