Epithelial-immune cell interplay in primary Sjogren syndrome salivary gland pathogenesis

In primary Sjogren syndrome (pSS), the function of the salivary glands is often considerably reduced. Multiple innate immune pathways are likely dysregulated in the salivary gland epithelium in pSS, including the nuclear factor-kappa B pathway, the inflammasome and interferon signalling. The ductal cells of the salivary gland in pSS are characteristically surrounded by a CD4(+) T cell-rich and B cell-rich infiltrate, implying a degree of communication between epithelial cells and immune cells. B cell infiltrates within the ducts can initiate the development of lymphoepithelial lesions, including basal ductal cell hyperplasia. Vice versa, the epithelium provides chronic activation signals to the glandular B cell fraction. This continuous stimulation might ultimately drive the development of mucosa-associated lymphoid tissue lymphoma. This Review discusses changes in the cells of the salivary gland epithelium in pSS (including acinar, ductal and progenitor cells), and the proposed interplay of these cells with environmental stimuli and the immune system. Current therapeutic options are insufficient to address both lymphocytic infiltration and salivary gland dysfunction. Successful rescue of salivary gland function in pSS will probably demand a multimodal therapeutic approach and an appreciation of the complicity of the salivary gland epithelium in the development of pSS. Salivary gland dysfunction is an important characteristic of primary Sjogren syndrome (pSS). In this Review, the authors discuss various epithelial abnormalities in pSS and the mechanisms by which epithelial cell-immune cell interactions contribute to disease development and progression

TLR2 signals via NF-κB to drive IL-15 production in salivary gland epithelial cells derived from patients with primary Sjögren's syndrome

Toll-like receptors (TLRs) are pattern recognition receptors linking innate and adaptive immune responses, which resulted overexpressed in primary Sjögren's syndrome (pSS). Interleukin-15 (IL-15) is a pro-inflammatory cytokine which was recently demonstrated to be involved in pSS pathogenesis. The study was undertaken to clarify whether TLR2 is involved in the production of IL-15 in human salivary gland epithelial cells (SGEC) from pSS patients. SGEC primary cell cultures were established from pSS minor salivary gland tissues explanted from patients with a sure diagnosis of SS. After neutralization of TLR2 with a blocking monoclonal antibody, IL-15 production was assayed by immunoblotting and flow cytometry, IL-15 in the culture supernatants was measured by ELISA, and mRNA levels were assessed by RT-PCR and real-time PCR. The production of IL-15 by pSS SGEC decreased in culture supernatants and in protein lysates (p < 0.01) when TLR2 signaling was inhibited in pSS SGEC. In addition, a control at the transcriptional level was also detected; in fact, inhibition of nuclear factor (NF)-κB through the transfection of pSS SGEC with the dominant-negative inhibitory κBα proteins (IκBα) vector (IκBαDN) abrogated the stimulatory effect of TLR2 on IL-15 production. These data suggest that TLR2 activation is involved in the induction of IL-15 production by pSS SGEC and promotes inflammation through NF-κB activation. Therefore, therapeutic strategies that target TLR2/IL-15 pathway might be strong candidates for preventing or treating pSS