Purpose. To investigate alpha B-Crystallin expression and localization in t
he lacrimal gland and tear fluid.
Methods. Mouse, rat, porcine, monkey and human lacrimal gland samples were
immuno-histochemically and immunoelectron-microscopically stained with vari
ous antibodies against alpha B-crystallin. Western- and Northern-blotting w
as performed to demonstrate the presence of alpha B-crystallin mRNA and pro
tein. 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 fou
nd in apical electron-dense granules of lacrimal duct cells, occasionally a
lso in the duct lumina. Western blotting confirmed the presence of alpha B-
crystallin in the lacrimal gland, Northern blot samples revealed the presen
ce of alpha B-crystallin mRNA.
In the human tear fluid, alpha B-crystallin was present in all samples inve
stigated.
Conclusions. We demonstrate for the first time that alpha B-crystallin is p
resent in the lacrimal gland. Presence of the protein in apical secretory g
ranules as well as presence in the tear fluid might indicate secretion of a
lpha B-crystallin into the tear fluid.