Distinction of two pathologic antithrombin III molecules: antithrombin III "Aalborg' and antithrombin III "Budapest'.

Plasma from two different thrombophilic families with functional inherited antithrombin III deficiency, i.e., with low antithrombin III activity but normal immunoreactive antithrombin III concentration, were investigated simultaneously in the same laboratory. The experiments (thrombin and Factor Xa inactivation, heparin affinity chromatography, modified two dimensional immunoelectrophoresis and gel filtration) showed a distinct difference between the two antithrombin III anomalies. The antithrombin III "Aalborg' had decreased thrombininactivating activity but normal Factor Xa-inactivating activity. The heparin affinity and the molecule weight are normal. The antithrombin III "Budapest' displays a more profound abnormality with pathologic thrombin and Factor Xa inactivation, decreased heparin affinity and abnormal molecular weight.