Evidence of the direct interaction between spontaneously occurring anti-factor VIII autoantibody and intravenous...

A previously normal female (39-year-old) who developed anti-factor VIII autoantibodies experienced massive and prolonged bleeding after the emergency operation for intramuscular hemorrhage in her left calf. Administration of high-dose intravenous immunoglobulin, 400 mg/kg for 5 consecutive days, decreased the antibody titer from 115 Bethesda units/ml (B U/ml) to 17 B U on the third day after the treatment. However, it again returned spontaneously to the original level there-after. In vitro studies using plasma from the patient were done to investigate the role of intravenous immunoglobulin. The autoantibody bound to an affinity column (intravenous immunoglobulin coupled CN-Br Sepharose 4B) and was eluted as a single peak. These results suggested that intravenous immunoglobulin directly interacted with auto-factor VIII antibody. This interaction might be involved in the in vivo decrease of antibody titer.