The synthesis of transcobalamin II, a vitamin B₁₂ transport protein by stimulated mouse peritoneal macrophages

The concentration of transcobalamin II (TCII), the vitamin B₁₂ binding protein which delivers vitamin B₁₂ to the tissues, was determined in stimulated and non stimulated mouse peritoneal exudate cells (PEC). Following a single intraperitoneal thioglycollate injection there was a marked increase in TCII which was shown to be produced by the adherent cells of the PEC, i.e., the macrophages. It has been concluded that the PEC macrophages synthesize TCII.