The possible relationship between the antiheparin activity of serum and thrombosis.

Stored serum reduces the anticoagulant effect of heparin on the clotting times of normal plasma. This is also well marked with sera from patients with Christmas (factor IX) deficiency, with factor VII-deficient sera, and in sera derived from patients treated with phenindione with a gross defect in thromboplastin generation. The possible relationship between antiheparin activity of serum and heparin resistance in recent thrombosis is discussed. The antiheparin agent resembles factor VII and Christmas factor in being present in excess in serum, adsorbed and subsequently eluted from alumina. Unlike these, however, it does not appear to be appreciably reduced by phenindione treatment. It appears to have some properties in common with those described for the thrombotic agent of serum described by Wessler and his colleagues. It may play a part in the increased coagulability associated with thrombosis from the release of serum products into the circulation, although its relationship to the production of thrombosis in man remains to be established.