A Familial Abnormality of Circulating Vitamin B12Binding Proteins: Occurrence in a Family of High Serum Concentrations of Transcobalamin II

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Abstract
A family is described in which 2 members (a father and daughter), both with quiescent ulcerative colitis, had abnormally high serum concentrations of a vitamin B12 binding protein. This protein had the molecular weight of transcobalamin II [TC II] on gel filtration, and behaved like TC II with respect to its elution from DE-23 cellulose, its inhibition at acid pH, its absorption by uncoated charcoal, its binding by anti-TC II antibodies, and its ability to transfer vitamin B12 to transformed lymphocytes. Its plasma clearance and tissue distribution when injected into rabbits was indistinguishable from that of TC II from normal subjects. It migrated on electrophoresis in the .beta..gamma. region. This is the 1st case report of related subjects in whom high serum concentrations of TC II were observed.