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Do antiphospholipid antibodies interfere with tissue factor pathway inhibitor?
E M Jacobsen1, P M Sandset, F Wisløff
1Haematological Research Lab., Ullevål University Hospital, Oslo, Norway. e.m.jacobsen@ioks.uio.no
Thrombosis Research
|May 21, 1999
Summary
Antiphospholipid antibodies (APA) are linked to higher tissue factor pathway inhibitor (TFPI) levels, both before and after heparin. However, strong lupus anticoagulants may inhibit TFPI
Area of Science:
- Hematology
- Immunology
- Thrombosis Research
Background:
- Antiphospholipid antibodies (APA) are associated with an increased risk of thrombosis.
- Tissue factor pathway inhibitor (TFPI) plays a crucial role in regulating coagulation.
- The interaction between APA and TFPI in the context of coagulation inhibition is not fully understood.
Purpose of the Study:
- To investigate whether antiphospholipid antibodies (APA) interfere with the phospholipid-dependent inhibition of coagulation by tissue factor pathway inhibitor (TFPI).
- To compare TFPI levels and activity in patients with APA versus healthy controls, both before and after heparin administration.
Main Methods:
- Eleven patients with APA and eleven matched healthy controls were enrolled.
- Blood samples were collected before and after intravenous heparin injection (5000 IE).
- TFPI antigen and activity were measured using chromogenic assays; TFPI anticoagulant activity was assessed with a modified diluted prothrombin time (dPT) assay.
Main Results:
- Preheparin TFPI antigen levels were significantly higher in APA patients (21.7 ng/ml) than in controls (14.2 ng/ml).
- Postheparin TFPI antigen and activity levels were significantly elevated in APA patients compared to controls.
- TFPI anticoagulant activity, measured by dPT assay, showed minimal increase after heparin in patients with strong lupus anticoagulants, suggesting inhibition.
Conclusions:
- Patients with APA exhibit elevated TFPI antigen and amidolytic activity, both basally and after heparin stimulation.
- These findings do not fully explain the thrombotic risk in APA patients but may indicate upregulated tissue factor activity.
- Strong lupus anticoagulants might inhibit the anticoagulant function of TFPI.
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