A role for lymphotoxin in primary Sjogren's disease.

The etiology of salivary gland injury in primary Sjögren's disease is not well understood. We have previously described a mouse model of Sjögren's disease, IL-14α transgenic (IL14αTG) mice, which reproduces many of the features of the human disease. We now demonstrate a critical role for lymphotoxin α (LTA) in the pathogenesis of Sjögren's disease in IL14αTG mice. IL14αTG mice express LTA mRNA in their salivary glands and spleen and produce soluble LTA protein in their salivary secretions. When IL14αTG mice were crossed with LTA(-/-) mice, the IL14αTG.LTA(-/-) mice retained normal salivary gland secretions and did not develop either lymphocytic infiltration of their salivary glands or secondary lymphomas. However, both IL14αTG and IL14αTG.LTA(-/-) mice produced similar amounts of IFN-α and had similar deposition of autoantibodies in their salivary glands. Both IL14α and IL14α/LTA(-/-) mice had similar B cell responses to T-dependent and T-independent Ags, L-selectin expression, and expression of RelA, RelB, and NF-κB2 in their spleens. These studies suggest that LTA plays a critical role in the local rather than systemic inflammatory process of Sjögren's disease. Furthermore, local production of soluble LTA in the salivary glands of IL14αTG mice is necessary for the development of overt Sjögren's disease. Autoantibody deposition alone is not sufficient to produce salivary gland dysfunction. We also demonstrate that LTA is increased in the salivary gland secretions and sera of patients with Sjögren's disease, further strengthening the biological relevance of the IL14αTG model to understanding the pathogenesis of human disease.