The lesion is Sjögren's syndrome consists of lymphocytic infiltration and has a pathology characteristic of the potential apoptotic death of salivary gland secretory epithelial cells. To examine the role of the glandular epithelial cells in the pathogenesis of autoimmune exocrinopathy, we studied Fas and Fas ligand (FasL) expression and quantitated the levels of apoptosis in salivary and lacrimal glands from NOD and NOD-scid mice, an animal model that develops a Sjögren's syndrome-like pathology.
The parotid, submandibular and lacrimal tissues of NOD, NOD-scid, and BALB/c mice were evaluated by immunohistochemical analysis for the expression of Fas and FasL. Nuclear fragmentation of DNA from the epithelial cells of exocrine tissues was evaluated by the terminal UTP nucleotide end labeling method (TUNEL). Messenger RNA was isolated from 8 and 18 week old mice and was analyzed by the reverse transcription-polymerase chain reaction (RT-PCR) for the expression of Fas and FasL.
We found suggestive evidence that apoptosis of the secretory epithelial cells occurs in both NOD and NOD-scid mice despite the lack of T- and B-lymphocytes in the latter. FasL mRNA and cell surface protein were expressed in salivary and lacrimal gland epithelial cells from 8 and 18 week old NOD, NOD-scid, and BALB/c mice. Fas protein and mRNA were expressed only in the exocrine glands from 18 week old NOD and NOD-scid mice. Glandular secretory epithelial cell apoptosis was elevated in both NOD and NOD-scid mice, however; there was little evidence of apoptosis in the control strain of BALB/c mice.
These results suggest a potential apoptotic process dependent on Fas:FasL interactions occurring in NOD-scid glandular secretory epithelial cells in the absence of lymphocytic infiltration.