αB-crystallin in lacrimal gland duct and tears

Purpose. To investigate alpha B-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 immunoelectron-microscopically stained with various antibodies against alpha B-crystallin. Western- and Northern-blotting was performed to demonstrate the presence of alpha B-crystallin mRNA and protein. Human tear fluid was analyzed for the presence of alpha B-crystallin using dot blotting. Results. alpha B-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 alpha B-crystallin in the lacrimal gland, Northern blot samples revealed the presence of alpha B-crystallin mRNA. In the human tear fluid, alpha B-crystallin was present in all samples investigated. Conclusions. We demonstrate for the first time that alpha B-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 alpha B-crystallin into the tear fluid.