The role of intrinsic epithelial activation in the pathogenesis of Sjögren's syndrome.

Sjögren's syndrome (SS) is a chronic autoimmune disorder that is characterized by dysfunction and destruction of the exocrine glands. Exocrinopathy is associated with periductal mononuclear cell infiltrates in the affected exocrine glands and B-cell hyperreactivity. Epithelial cells are thought to play an important pathogenetic role, as suggested by the occurrence of infiltrating lesions in various epithelial tissues (described as autoimmune epithelitis) as well as the increased epithelial expression of several inflammatory proteins in the histopathologic lesions of patients. The application of long-term cultured non-neoplastic salivary gland epithelial cell (SGEC) lines has permitted the more explicit investigation of the role of these cells in the pathophysiology of SS. These studies have revealed the inherent capacity of SGEC to induce and promote chronic inflammatory reactions, as corroborated by the constitutive or inducible expression of various molecules implicated in innate and acquired immune responses. Furthermore, significantly increased constitutive expression of several molecules has been observed in SGEC lines derived from SS patients, as compared to those obtained from disease control patients. This fact strongly indicates the operation of intrinsic activation mechanisms in the epithelia of SS patients and further supports the active participation of these cells in the pathogenesis of the disorder.