CLOSE ANATOMICAL RELATIONSHIPS BETWEEN NERVE-FIBERS AND MHC CLASS II-EXPRESSING DENDRITIC CELLS IN THE RAT-LIVER AND EXTRAHEPATIC BILE-DUCT

The anatomical relationships between immunocytochemically identified n erve fibers and MHC class II-expressing antigen presenting dendritic c ells were investigated in the rat hepatobiliary system using immunocyt ochemistry, confocal laser scanning, and electron microscopy. Close pr oximity of nerve fiber varicosities immunostained for PGP 9.5 and MHC class II-expressing dendritic cells was frequently observed in the wal l of extrahepatic bile ducts, in Glisson's area, around central and he patic veins, and in the liver capsule, Contacts between nerve fibers s taining for substance P, calcitonin gene-related peptide, calretinin, and vasoactive intestinal polypeptide and dendritic cells were more of ten observed around extrahepatic bile ducts than in Glisson's area. Ne rve fibers immunostaining for tyrosine hydroxyl ase and neuropeptide Y were numerous both in the wall of extrahepatic bile ducts and in Glis son's area and frequently contacted dendritic cells there. At the ultr astructural level, close membrane contacts between bare axolemmal area s of unmyelinated nerve fibers and processes of MHC class II-expressin g cells were observed. These: results demonstrate close anatomical rel ationships of nerve fibers from various sources with antigen presentin g dendritic cells in the visceral domain and suggest modulation of ant igen presentation by the autonomic nervous system.