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
