Development of factor VIII antibody in haemophilic monozygotic twins. European Study Group of Factor VIII Antibody.

The immunologic consequences of replacement therapy have been studied in 2 pairs of young haemophilic monozygotic twins. In both pairs one cotwin only developed a factor VIII specific antibody. This non-concordance illustrates the influence upon a specific immune response of non-genetic factors since the blood products, administered to each brother-pair, were not at all time identical nor were the regimens of transfusion therapy.