FRI0286 Rank-l is expressed by salivary gland epithelial cells in primary sjogren’s syndrome: a novel actor in ectopic lymphoid structure neogenesis
Authors: P.-M. DURET, R. VEBER, R. FELTEN, F. MONNEAUX, C. MUELLER, J. SIBILIA, H. DUMORTIER, J.-E. GOTTENBERG
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Tertiary Lymphoid Organs (TLOs) are observed in target tissues of various immune-mediated inflammatory diseases (IMIDs) such as salivary glands in primary Sjogren's syndrome<sup>1</sup> (pSS). TLOs are mimicking secondary lymphoid organs (SLOs) architecture and strikingly share common features with lymph nodes.<sup>2</sup> SLOs organogenesis is coordonated by a complex stromal network that has not been fully characterised in TLOs yet. Although RANK-L (Receptor Activator of NF-kB Ligand) has been recently involved as a pivotal cytokine in precoce steps of lymph nodes development,<sup>3</sup> notably through a stromal cell expression, its contribution in TLOs neogenesis remains unclear. <h3>Objectives</h3> To characterise stromal cells subsets within TLOs arising in the salivary glands and to determine wether RANKL is expressed or not in the the target tissue of pSS. <h3>Methods</h3> Stromal cells and RANK-L expression were analysed in TLOs from salivary glands by immuno-fluorescence on frozen sections in the NZB/NZW F1 mouse model and in minor salivary gland biopsies of patients fullflling 2016 ACR-EULAR Sjögren's syndrome criterias and by flow- cytometry after enzymatic digestion of NZB/NZW F1 salivary glands. RANK-L expression has also been assessed by Real Time quantitative Polymerase Chain Reaction (RT-qPCR) and immunofluorescence on primary cultures of salivary gland epithelial cells (SGECs) with or without IL-1b or Interferon alpha (INF-a) stimulation. <h3>Results</h3> Most of SLOs stromal cells populations: Fibroblastic Reticular Cells (FRCs), Follicular Dendritic Cells (FDCs), Lymphatic Endothelial Cells (LECs), Blood Endotholial Cells (BECs) and High Endothelial Veinules (HEVs) were identified in salivary TLOs of both NZB/NZW F1 mice and patients with pSS. FRCs were the dominant subset in salivary TLOs and their proportion correlated with the degree of lymphocytic infiltration (r=0,7 ; p=0,007). In SLOs, RANK-L was mainly expressed by MRCs, whereas, none of them could be detected in salivary TLOs. However, despite the absence of MRCs in TLOs, RANK-L was still expressed by a few T-cells within the infiltrates and strikingly by epithelial cells. Furthermore, RANK-L expression by SGECs in primary cultures was increased after INF-a or IL-1b stimulation. <h3>Conclusions</h3> To our knowledge, this is the first report of a RANK-L contribution to primary Sjögren's syndrome. These results suggest that RANK-L could be an important actor of ectopic lymphoid neogenesis. RANK-L inhibition might represent, in the future, a relevant immuno-modulatory strategy in primary Sjögren's syndrome. <h3>References</h3> [1] Corsiero E, Nerviani A, Bombardieri M, Pitzalis C. Ectopic Lymphoid Structures: Powerhouse of Autoimmunity. Front. Immunol. 2016;7:430. [2] Buckley CD, Barone F, Nayar S, Bénézech C, Caamaño J. Stromal cells in chronic inflammation and tertiary lymphoid organ formation. Annu. Rev. Immunol. 2015;33:715–745. [3] Kong YY, Yoshida H, Sarosi I, Tan HL, Timms E, Capparelli C, et al. OPGL is a key regulator of osteoclastogenesis, lymphocyte development and lymph- node organogenesis. Nature. 1999Jan 28;397(6717):315–23. <h3>Disclosure of Interest</h3> None declared