The immunologic character of acquired inhibitors of antihemophilic globulin (factor 8) and the kinetics of their interaction with factor 8.

Investigations were undertaken of the chemical nature and kinetics of interaction of three acquired inhibitors of Factor VIII. The inhibition was stoichiometric, one molecule of inhibitor (or one site on a molecule) being required to inactivate one molecule of Factor VIII. All three inhibitors were found to be monotypic antibodies of class IgG, Type K (gamma(2) kappa(2)). This appears to be the second syndrome due to the production of monotypic antibody, and the first instance involving IgG immunoglobulins.