Expression of CD44 isoforms in normal salivary gland tissue: an immunohistochemical and ultrastructural study

We studied the expression of CD44 isoforms immunoreactivity in normal human salivary gland tissue, aiming at its full characterisation in normal epith elial and myoepithelial cell types. Optical immunohistochemistry techniques using monoclonal antibodies anti-CD44v3, CD44v4/5 and, for CD44v6, togethe r with immunoelectron microscopy, were performed in serous, seromucinous an d mucinous glands. Normal human breast and a case of lactating breast adeno ma were used for comparative purposes and as controls. CD44v3 was positive in acinar and myoepithelial cells and was absent in mucin-producing cells f rom the different gland types. CD44v4/5 was consistently negative in all ty pes of salivary tissue. CD44v6 was constantly positive in serous acinar cel ls, focally positive in basal cells of ducts, and myoepithelial cells consi stently expressed it. At the ultrastructural level, CD44v6 was localised to the interdigitating processes of acinar cells, whenever they were not cove red by basal lamina and to the cell membrane facing myoepithelial cells. In myoepithelial cells, immunolabelling was found at the membranes facing the acinar cells and in caveolae present at this interface. No labelling was f ound at cell membranes of both acinar and myoepithelial cells in contact wi th basal lamina or at the luminal aspect of the former. The finding of CD44 v3 and v6 in myoepithelium of normal salivary glands may argue in favour of the role of these molecules in the regulation of growth and renewal of nor mal tissues and, potentially, on the morphogenesis of salivary gland neopla sms.