The three transcobalamins in myeloproliferative disorders and acute leukaemia

The unsaturated vitamin B12 binding capacity of whole serum (UBBC) and of the three transcobalamins (TC) has been studied in patients with various haematological diseases including myeloproliferative disorders (MPD) and acute leukaemia. The binding capacity of TC I and TC III was increased in MPD; TC I being particularly high in chronic granulocytic leukaemia (CGL) and TC III especially raised in polycythaemia rubra vera (PRV) and in infectious leucocytosis. The binding capacity of both TC I and TC III correlated with blood neutrophil count and the ratio TC III/TC I was low in CGL and increased in PRV. TC II was increased in acute myelogenous leukaemia, during remission and blast cell crisis of CGL and in refractory anaemia with excess of myeloblasts but not in acute lymphoblastic leukaemia (ALL). TC II correlated inversely with blood neutrophil count. There is an inverse ratio between TC II and TC I at least in myelogenous leukaemia. These abnormalities are discussed in relation to granulocyte kinetics. TC III and TC I reflect probably the total body granulocyte pool and share some biochemical and immunological properties supporting the view that they have a common origin in the more mature stages of the granulocyte cell line while TC II probably originates partly in more primitive granulocytes.