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E Arnaud, M Lafay, P Gaussem, V Picard, M Jandrot-Perrus, M Aiach and F Rendu
CJF 91-01 INSERM, Faculte des Sciences Pharmaceutiques et Biologiques,
Universite Paris V, France.
An autoantibody, developed by a patient with severe and recurrent arterial
thrombosis, was characterized to be directed against the anion- binding
exosite of thrombin, and inhibited all thrombin interactions requiring this
secondary binding site without interfering with the catalytic site. The
effect of the antibody was studied on thrombin interactions with platelets
and endothelial cells from human umbilical veins (HUVEC). The autoantibody
specifically and concentration- dependently inhibited
alpha-thrombin-induced platelet activation and prostacyclin (PGI2)
synthesis from HUVEC. It had no effect when gamma- thrombin or the thrombin
receptor activation peptide SFLLR were the inducers. The effect of the
antibody on protein C activation has been studied. The antibody blocked the
thrombin-thrombomodulin activation of protein C. The inhibition of the
activation was maximal with a low concentration of thrombomodulin. The fact
that the autoantibody inhibited concentration-dependent
alpha-thrombin-induced platelet and endothelial cell functions emphasizes
the crucial role of the anion- binding exosite of thrombin to activate its
receptor. In regard to the pathology, the antibody inhibited two vascular
processes implicated in thrombin-antithrombotic functions, PGI2 secretion,
and protein C activation, which could be implicated in this arterial
thrombotic disease.
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| Copyright © 1994 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||