HETEROGENEITY OF LUPUS ANTICOAGULANT (LA) ANTIBODIES - LA ACTIVITY INDILUTE RUSSELLS VIPER VENOM TIME AND DILUTE KAOLIN CLOTTING TIME DETECT DIFFERENT POPULATIONS OF ANTIBODIES IN PATIENTS WITH THE ANTIPHOSPHOLIPID SYNDROME

''Antiphospholipid'' (aPL) antibodies comprise two main groups of anti bodies, lupus anticoagulant (LA) antibodies and ''anticardiolipin'' (a CL) antibodies which can be separated by certain chromatographic techn iques. In this study we analysed the plasma of 10 patients with aPL an tibodies. and were able to demonstrate that in four patients with both clotting test reactivities, the dilute Russell's Viper Venom Time (dR VVT) activity can be separated from the dilute Kaolin Clotting Time (d KCT) reactivity by using a polyacrylamide-immobilised phosphatidylseri ne column but not with phospholipid liposomes. The differential reacti vity of the autoantibodies in this patient population is not due to bi nding to beta 2GPI, prothrombin or protein C in solid-phase immunoassa ys. Hence LA antibodies detected in different phospholipid dependent c lotting tests detect different populations of antibodies in some APS p atients and the routine detection of LA antibodies should be performed with at least two clotting tests looking at different coagulation rea ctions.