[An immunohistological study of normal parotid gland]

Cytoskeletal proteins from each epithelial component of the parotid gland were studied immunohistologically using monospecific monoclonal antibodies, and we obtained several interesting results: 1) The expression of vimentin, S-100 protein and GFAP were essentially unrecognizable. 2) The expression of alpha-actin was recognized only in myoepithelial cells, and was negative in other tissues. 3) The expression of CK-3, CK-6, CK-7, CK-8 and CK-18 was commonly recognized in both acinal and ductal cells. 4) The expression of CK-13 and CK-19 was recognized in ductal cells, but was negative in acinal cells. 5) We propose that the characteristic cell be referred to as a "duct satellite cell", as it comprises part of the intercalated duct and is sporadically localized around striated and layer ducts. 6) These duct satellite cells express all subclasses of cytokeratin observed in myoepithelial, acinal and ductal cells. 7) The duct satellite cells observed in this study are most likely to correspond to the undifferentiated reserve cells described in "bicellular theory", and we speculate that all epithelial tissues of the parotid gland originate from these cells.