Sjögren's syndrome: pathogenesis.

Sjögren's syndrome is a chronic inflammatory disease of the lacrimal and salivary gland with subsequent keratoconjunctivitis sicca and xerostomia. Histopathologic findings include damaged acini of the lacrimal and salivary glands with mononuclear cell infiltrates of lymphocytic and plasma cell type. The cause of the damage is cell-mediated cytotoxicity. The pathogenesis of Sjögren's syndrome is still unknown. The role of viral infections failed to show a causative effect. On the other hand, tissue destruction was shown to be mediated by activated T cells of CD4+ type that home into the lacrimal gland. This process is signal-mediated through the T-cell receptor that interacts with class II antigen on the epithelial cells of exocrine glands. This, in turn, induces the expression of Fas/APO-1 and Fas-mediated apoptosis of acinar cells. Granzyme A and perforin are cytolytic enzymes secreted by activated T lymphocytes that seem to participate in acinar cell destruction.