Autoimmune epithelitis in primary Sjögren's syndrome.

Primary Sjögren's syndrome (pSS) is characterized by an autoimmune epithelitis associated with chronic inflammation of the exocrine glands. Alterations of extra-glandular functions in pSS is associated with lymphocytic infiltrates that invade the epithelial structures of affected organs. Within epithelial tissue, the expression of class II major histocompatibility complexes and costimulatory molecules by epithelial cells acting as non-professional antigen presenting cells, leads to the activation of T and B lymphocytes through multiple cellular crosstalk pathways. Although the pathogenetic mechanisms underlying pSS have not yet been elucidated, it is accepted that glandular epithelial cells are central regulators of the local autoimmune response.