Changes in the character of Factor VIII inhibitors following Factor VIII transfusion

Factor VIII inhibitors from 4 haemophiliacs have been studied at intervals following transfusion of a factor VIII preparation with an aim to correlate their reaction kinetic and avidity with their immuno-chemical character. Post-treatment antibodies are more avid than pre-treatment antibodies and show a second order reaction while pre-treatment antibodies produce a graph of complex nature for the time course inactivation of Factor VIII. It seems that IgG3 anti VIII:C that forms a significant part of post-treatment antibody is responsible for these discrepancies.