Characterization of an abnormal antithrombin (Milano 2) with defective thrombin binding

A. Tripodi, A. Krachmalnicoff, P. M. Mannucci

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Four members of an Italian family (two with histories of venous thromboembolism) had a qualitative defect of antithrombin III reflected by normal antigen concentrations and half-normal antithrombin activity with or without heparin. Anti-factor Xa activities were consistently borderline low (about 70% of normal). For the propositus' plasma and serum the patterns of antithrombin III in crossed-immunoelectrophoresis with or without heparin were indistinguishable from those of normal plasma or serum. A normal affinity of antithrombin III for heparin was documented by heparin-sepharose chromatography. Affinity adsorption of the propositus' plasma to human α-thrombin immobilized on sepharose beads revealed defective binding of the antithrombin III to thrombin-sepharose. Hence the molecular defect of this variant appears to be at the active site responsible for binding and neutralizing thrombin, thus accounting for the low thrombin inhibitory activity.

Original languageEnglish
Pages (from-to)349-352
Number of pages4
JournalThrombosis and Haemostasis
Issue number3
Publication statusPublished - 1986

ASJC Scopus subject areas

  • Hematology


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