Immunologic studies on a pancreatic oncofetal protein

Immunization of rabbits with a human fetal pancreas extract produced precipitating antibody against an antigen present only in fetal pancreas and extracts of human pancreatic carcinoma. Pancreatic oncofetal protein (POP) migrated on immunoelectrophoresis in the alpha1-alpha2 region, thus making possible its detection by counterimmunoelectrophoresis. POP was found in the 12,000 X g supernatant of fetal pancreas and could be precipitated with (NH4)2SO4 at concentrations between 30 and 45%. The antigen was partially purified by consecutive centrifugation at 12,000 X g, 40% (NH4)2SO4 precipitation, and ion-exchange chromatography. Treatment of the POP with trypsin completely abolished its antigenic activity; this suggested that the antigen was a protein or a moiety closely associated with protein.