The failure of granulocytes to produce transcobalamin I TC I.

The hypothesis that transcobalamin I (TC I) originates from granulocytes was tested by comparing the isoelectric focusing (IEF) patterns of the R-type binder (cobalophilin) of vitamin B12 of: 1) lysed granulocytes, 2) 24 h granulocyte output, and 3) plasma. The preparations came from the blood of 5 normal subjects and 4 with myeloproliferative states. The cobalophilin released into a culture of granulocytes resembled the binder in the granulocytes initially. TC I, defined as the alpha1 cobalophilin with components isoelectric between pH 2.9-3.35 and as a carrier of native plasma B12, was not released by granulocytes. The granulocyte binder of leukaemic granulocytes did not differ from the normal in content per cell or amount released.