Immunoelectrophoretic evidence of a thrombin-induced abnormality in a new variant of hereditary dysfunctional antithrombin III (AT III 'Vicenza').

An Italian family with thrombosis and hereditary dysfunctional AT III, i.e. reduced biological activity and normal levels of the immunoreactive protein is presented. The abnormal molecule, called AT III 'Vicenza', was characterized by two-dimensional crossed immunoelectrophoresis either in the absence or presence of heparin. In the presence of heparin, a normal pattern was found in plasma, but abnormality was evident in serum. A similar abnormality was found in plasma artificially clotted with thrombin. The role of thrombin in inducing the immunoelectrophoretic abnormality of AT III 'Vicenza' is discussed.