Serum transcobalamin in myeloid leukemia.

Abstract

Abstract The determination of serum vitamin B 12 concentrations, unsaturated B 12 binding capacity, and total B 12 binding capacity of whole serum and of the separate transcobalamin I and transcobalalamin II fractions has shown that the increased B 12 binding capacity of serum proteins in chronic myeloid leukemia is due mainly to an increase in transcobalamin I. Transcobalamin II is relatively unchanged. Serum B 12 concentrations and unsaturated B 12 binding capacity are only slightly elevated in acute myeloblastic leukemia; total binding capacity of transcobalamin I is within the normal range. The findings observed in acute promyelocytic leukemia are similar to those found in chronic myeloid leukemia. These observations suggest that the excessive amounts of transcobalamin I in chronic myeloid leukemia are produced by proliferating and differentiated myeloid cells beginning at the promyelocytic stage. Transcobalamin I is decreased markedly following the administration of cytotoxic agents.