The preparation of human intrinsic factor-cobalamin complex from human gastric juice by immunoadsorption

Immune complexes of human intrinsic factor were prepared by mixing gastric juice saturated with vitamin B12, and sera from patients with pernicious anaemia that had a high proportion of binding (Type II) antibody. The complexes were isolated by sodium sulphate precipitation followed by Sephadex G-150 gel filtration. Acid conditions dissociated the immune complexes and allowed separation of specific antibody and purified antigen bound to vitamin B12 by Sephadex G-200 gel filtration. Specific antibody was covalently attached to Protein A Sepharose CL-4B by coupling with water soluble carbodiimide which allowed intrinsic factor-B12 complex to be purified directly from gastric juice. The intrinsic factor obtained after iodination, ran as a single band on SDS-polyacrylamide gel electrophoresis and was biologically active.