When radioactive B12 was added to normal serum, it was bound predominantly to beta globulin. Deficient binding was observed in the serum of five of ten patients with untreated pernicious anemia. Treatment of these patients with B12 restored the beta globulin B12 binding capacity toward normal.
In one of the five patients there was virtually no beta globulin binding of added B12 before treatment. This patient exhibited a malabsorptive pattern Schilling test when first seen. Treatment with B12 was attended by an increase of beta globulin binding capacity, and by return of the ability to absorb oral B12 when given with intrinsic factor. It is possible that these two abnormalities are related in that the beta globulin may have an important role in the absorption and transport of B12.