AlphaB-crystallin in lacrimal gland duct and tears

PURPOSE: To investigate alphaB-Crystallin expression and localization in the lacrimal gland and tear fluid. METHODS: Mouse, rat, porcine, monkey and human lacrimal gland samples were immuno-histochemically and immuno-electron-microscopically stained with various antibodies against alphaB-crystallin. Western- and Northern-blotting was performed to demonstrate the presence of alphaB-crystallin mRNA and protein. Human tear fluid was analyzed for the presence of alphaB-crystallin using dot blotting. RESULTS: alphaB-Crystallin is located in the lacrimal gland duct cells but not in the acini. Electron microscopically, the protein was frequently found in apical electron-dense granules of lacrimal duct cells, occasionally also in the duct lumina. Western blotting confirmed the presence of alphaB-crystallin in the lacrimal gland, Northern blot samples revealed the presence of alphaB-crystallin mRNA. In the human tear fluid, alphaB-crystallin was present in all samples investigated. CONCLUSIONS: We demonstrate for the first time that alphaB-crystallin is present in the lacrimal gland. Presence of the protein in apical secretory granules as well as presence in the tear fluid might indicate secretion of alphaB-crystallin into the tear fluid.