[Different proportions of factor VIII and factor VIII inhibitors in their antigen-antibody complexes]

We examined the physico-chemical properties of factor VIII inhibitors in two patients. There is no stoichiometric mixture of factor VIII and factor VIII inhibitor since one polyvalent factor VIII particle can be bound by various numbers of factor VIII inhibitor particles. The balance between free factor VIII and inhibitor and their antigen-antibody complexes cannot be explained by the homogeneous natural law of mass action. A patient with classical hemophilia A exhibited an inhibitor which shows conformity with the Poisson distribution as far as the portion of free factor VIII activity is concerned. The spontaneously occurring inhibitor showed a different binding characteristic to factor VIII. We demonstrated here that the Freundlich's adsorption isotherme is effective for a spontaneous factor VIII inhibitor. During follow up qualitative and quantitative changes of both inhibitor types were observed. We assume that the change of property of inhibitor in hemophiliacs is due to a stronger binding to factor VIII and of the spontaneous inhibitor to a poorer fit of antigen and antibody.