GENE EXPRESSION IN HETEROZYGOTES AND SYNTHESIS OF PLASMA ANTIHAEMOPHILIC FACTOR.

Abstract

THE communication by McLester and Graham1 illustrates the difficulties which can arise when the concentration of a plasma protein cannot be measured but can only be inferred from its biological activity. Patients with von Willebrand's disease can synthesize antihaemophilic globulin (AHG, factor VIII): their plasma has AHG activity ranging from 1.6 to 100 per cent of the normal2 and, when stimulated by injection of a plasma fraction free from AHG, the AHG activity of their plasma rises3. If the hypothetical ‘activator’ or ‘inhibitor’ or ‘inducer’ of AHG suggested by McLester and Graham exists, it is presumably qualitatively and quantitatively normal in haemophilia-A and in carriers of the haemophilia-A gene. It follows that von Willebrand's disease is irrelevant to any discussion of gene action in heterozygotes for haemophilia-A, though of great importance in the haematological aspects of the bleeding diatheses.