Clinical significance of antibodies to bovine and human thrombin and factor V after surgical use of bovine thrombin.

Two patients exposed during surgery to bovine thrombin developed antibodies reacting with both bovine and human thrombin and Factor V. Their thrombin times were markedly prolonged with bovine thrombin and modestly prolonged with human thrombin. High titer anti-bovine Factor V created diagnostic confusion in one patient by neutralizing bovine Factor V in a prothrombin assay substrate. Although weaker, antibody activity against human Factor V led to postoperative factor V deficiency in both patients. Such cross-reacting antibodies, recognizable by their higher titer against bovine than human Factor V, should be suspected when a patient surgically exposed to bovine thrombin develops a Factor V anticoagulant after operation. Crossed immunoelectrophoresis of adsorbed bovine plasma with each patient's plasma as antibody revealed many precipitin arcs indicative of immunization of the patients to additional proteins in a commercial thrombin preparation.