BETA(2)-GLYCOPROTEIN-I IN THROMBOSIS - EVIDENCE FOR A ROLE AS A NATURAL ANTICOAGULANT

Although the physiological role of beta(2)-glycoprotein I (B(2)GPI) is unknown, in vitro evidence indicates that B(2)GPI may be a natural an ticoagulant. In this study we have examined whether fluctuations of pl asma B(2)GPI occur in in vivo coagulation. Serial measurements of B(2) GPI and other anticoagulant proteins were performed in 51 patients wit h thrombotic (group 1: six patients with disseminated intravascular co agulation (DIC), group 2: venous (n=4) or arterial (n=17) thrombosis) and non-thrombotic disease (group 3: 24 patients undergoing elective s urgery). Reductions in plasma B(2)GPI levels were seen in most patient s which were roughly proportional to the severity of their illness. Pa rticularly striking reductions of B(2)GPI, protein C (PC) and antithro mbin III (AT-III) (mean +/- 95% CI: 42.7 +/- 8.6%, 42.1 +/- 14.8%, 39. 1 +/- 28.4% respectively) were seen in group 1. The reductions in plas ma B(2)GPI were significantly greater in group 1 than in the other gro ups. Dilutional factors explain most of the reductions in B(2)GPI, PC and AT-III in groups 2 and 3, but contribute little to group 1. In con clusion, although B(2)GPI behaves as a 'negative acute phase reactant' , the magnitude of reduction of plasma B(2)GPI levels, accompanied by reductions in other anticoagulant proteins in patients with DIC, sugge sts specific consumption of B(2)GPI in in vivo coagulation. This study provides further evidence that B(2)GPI is an anticoagulant of physiol ogical importance.