Anticoagulant Activity in Non-Immunoglobulin Fraction from Plasma of Patients with Antiphospholipid Syndrome

Abstract

Anticoagulant activity is present in non-immunoglobulin (IgG) fractions from plasma of patients with antiphospholipid syndrome (APS). Plasma from six patients with primary or secondary APS was passed through a protein A sepharose 4B column. Anticoagulant activity in IgG samples and non-IgG samples was determined by both dilute aPTT based clotting assay and by dilute PT based clotting assay. Thrombin generation was determined by prothrombinase complex assay in the presence of IgG sample or non-IgG sample.

Anticoagulant activity was detected in the IgG samples with the dilute aPTT based clotting assay and in non-IgG samples with the dilute PT based clotting assay. The activity was not detected in IgG samples with the dilute PT clotting assay. Forty percent of total thrombin generation was inhibited in the presence of non-IgG samples although thrombin generation was not inhibited in the presence of IgG samples and β2-glycoprotein I.

The anticoagulant activity detected by dilute PT based clotting assay and prothrombinase complex assay was non-IgG, phospholipid-Ca++-dependent and β2-glycoprotein I-independent. The role of non-IgG anticoagulants should be determined as well as the role of LA Igs antibodies in the mechanisms of thrombosis.

Keywords:

Antiphospholipid syndrome (APS) - lupus anticoagulant (LA) - IgG - anticoagulant - thrombin generation