The role of fractalkine as an accelerating factor on the autoimmune exocrinopathy in mice

PURPOSE. Sjögren's syndrome (SS) is an organ-specific autoimmune disease caused by the progressive loss of exocrine glands and is associated with several autoimmune phenomena. Various research studies have been performed, and many molecules have been suggested as responsible for the pathogenesis of SS. Here the authors show the increased expression of fractalkine (CX₃CL1) in lacrimal glands of SS model mice. Among more than 50 known chemokines, fractalkine is the sole member of the CX₃C family and has unique structural and functional attributes. The purpose of this study was to analyze the role of fractalkine in exocrine glands. METHODS. The expression of fractalkine in the lacrimal glands of thymectomized NFS/sld mice was investigated by immunohistochemistry and RT-PCR. To confirm the effects of fractalkine in exocrine glands, tissue-specific fractalkine transgenic mice were generated using the salivary amylase promoter. RESULTS. The results demonstrated the upregulated fractalkine expression in thymectomized NFS/sld mice. Furthermore, the lacrimal and salivary gland-specific fractalkine transgenic mice showed the expression of fragmented fractalkine and lymphocytic infiltration in their lacrimal and submandibular glands. Interestingly, the dominant population was B cells in the lacrimal glands, whereas B cells and CD4⁺ T cells were infiltrated in the submandibular glands. These mice also demonstrated slightly decreased tear and salivary secretion compared with wild-type mice. CONCLUSIONS. Based on these results, it may be that fractalkine contributes to the development of SS, especially in lymphocyte migration to exocrine glands, and that it accelerates the disease in association with other molecules.