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B cell-activating factor of the TNF family (BAFF) plays a key role in promoting B lymphocyte activation and survival. We previously showed in primary Sjögren's syndrome that salivary gland epithelial cells (SGECs), the resident targeted cells of autoimmunity in this disease, can produce BAFF after infection with a double-stranded RNA (dsRNA) virus by a protein kinase RNA (PKR)-dependent mechanism. This study aimed to assess the effect of different viruses on various cell types - SGECs but also dendritic cells (DCs) and monocytes - in the induction of BAFF. BAFF induction was observed after Sendai virus infection of monocytes and SGECs, as well as poly(I:C) stimulation of DCs. However, PKR inhibition by 2-aminopurine failed to reduce BAFF expression in these infected or stimulated cells. Conversely, in Sendai virus-infected monocytes, blocking type 1 interferon (IFN) receptor by anti-IFNAR1 antibody strongly inhibited BAFF expression. These results provide additional data suggesting that both dsRNA virus stimulation of DCs and single-stranded RNA virus infection of SGECs or monocytes can induce BAFF expression, but through a PKR-independent mechanism for these 3 cell types and a type 1 IFN-dependent mechanism in monocytes and SGECs. Thus, BAFF induction by viral infection is a general phenomenon, but the types of viruses and mechanisms of the induction depend on the cell type., (Copyright © 2010 S. Karger AG, Basel.)

Gene expression analysis of target organs might help provide new insights into the pathogenesis of autoimmune diseases. We used global gene expression profiling of minor salivary glands to identify patterns of gene expression in patients with primary Sjögren's syndrome (pSS), a common and prototypic systemic autoimmune disease. Gene expression analysis allowed for differentiating most patients with pSS from controls. The expression of 23 genes in the IFN pathways, including two Toll-like receptors (TLR8 and TLR9), was significantly different between patients and controls. Furthermore, the increased expression of IFN-inducible genes, BAFF and IFN-induced transmembrane protein 1, was also demonstrated in ocular epithelial cells by quantitative RT-PCR. In vitro activation showed that these genes were effectively modulated by IFNs in salivary gland epithelial cells, the target cells of autoimmunity in pSS. The activation of IFN pathways led us to investigate whether plasmacytoid dendritic cells were recruited in salivary glands. These IFN-producing cells were detected by immunohistochemistry in all patients with pSS, whereas none was observed in controls. In conclusion, our results support the pathogenic interaction between the innate and adaptive immune system in pSS. The persistence of the IFN signature might be related to a vicious circle, in which the environment interacts with genetic factors to drive the stimulation of salivary TLRs.