Characterization of R-type vitamin B12-binding proteins by isoelectric focusing. III. Cobalophilin (R protein) in myeloproliferative states and leukocytosis.

The R-type vitamin B12-binding protein (cobalophilin) in plasma and serum of patients with myeloproliferative diseases and leukocytosis was studied by gel filtration and isoelectric focusing. The isoproteins composing the cobalophilin were mainly the same in these disorders as in plasma of health subjects. In half the patients with chronic myelogenous leukaemia and a few of those with leukocytosis some of the isoproteins were more acid than those found in healthy subjects. In chronic myelogenous leukaemia the high unsaturated vitamin B12-binding capacity of plasma was due to an increase in the fairly acid isoproteins, whereas in polycythaemia vera and in most cases of leukocytosis there was an increase in the least acid isoproteins.