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A simple assay of intrinsic factor-vitamin B12 complex employing the binding intrinsic factor antibody
  1. Elizabeth Jacob,
  2. H. A. W. O'Brien
  1. Department of Haematology, St Bartholomew's Hospital, London


    The reaction between binding intrinsic factor antibody and intrinsic factor-vitamin B12 complex has been studied. Initially in the zone of antibody excess, the relationship between the amount of antigen present and the amount of antigen-antibody complex adsorbed onto zirconium phosphate gel was linear. With increasing amounts of antigen, the curve departed from linearity and reached a plateau. The linear portion of the reaction forms the basis of a simple and reproducible assay for quantitating intrinsic factor to which vitamin B12 has already been bound. The assay provides a method for studying the fate of intrinsic factor-vitamin B12 complex during digestion and absorption. In two normal subjects given radioactive vitamin B12 orally, aspiration of ileal contents showed that only 50 to 70% of the radioactivity was bound to intrinsic factor at that level.

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