E2 antigen in primary biliary cholangitis

Confocal micrographs of bile ducts from a patient with primary biliary cholangitis (PBC) (panels A and C) and primary sclerosing cholangitis (PSC, panels B and D). The sections are stained with a mouse monoclonal antibody directed against the E2 antigen of human pyruvate dehydrogenase. Panel A: The PBC bile duct epithelial cells demonstrate intense homogeneous luminal staining (arrow). Only one of eight mouse monoclonal antibodies reacted with the luminal antigen in the PBC bile duct cell. This suggests that the reaction was with protein that had some antigenic similarity to pyruvate dehydrogenase but was different from it. Panel B: The PSC bile duct shows only granular staining similar to that of normal mitochondrial staining in the cytoplasm. Panel C: The PBC bile duct section was examined using Lutz color intensity banding. Red staining, which is the second highest intensity to white, is found at the luminal surface and is different from the blue and green staining of mitochondria. Panel D: In the PSC bile duct, staining is restricted to low intensity green and blue and demonstrates only the normal staining of mitochondria.