Immunofluorescence studies on the occurrence and localization of the CEA-related biliary glycoprotein I (BGP I) in normal human gastrointestinal tissues.

Biliary glycoprotein, I(BGP I) is a carcinoembryonic antigen (CEA) cross-reactive glycoprotein of normal human bile. Its occurrence and localization was studied in normal human gastrointestinal tissues by means of direct immunofluorescence using immunadsorbent purified BGP I antibodies with high selectivity for BGP I, as compared to CEA and 'non-specific cross-reacting antigen' (NCA). As controls fluorescein-labelled CEA and NCA were used. Specific BGP I fluorescence was only found in the biliary tract, i.e. in bile canaliculi, in the lumen of large bile ducts and on the surface of the gall bladder mucosa. No fluorescence was found in the hepatocytes or in the cells lining larger bile ducts or the gall bladder. Fluorescence probably due to cross-reaction with NCA was obtained in the cytoplasm of macrophages in different organs and on the surface of bowel epithelium.