AB0190 CROSSTALK BETWEEN SALIVARY GLAND EPITHELIAL CELLS AND B LYMPHOCYTES IN PRIMARY SJÖGREN’S SYNDROME
Authors: Elodie Rivière, Juliette Pascaud, Nicolas Tchitchek, Saida Boudaoud, Audrey Paoletti, Bineta Ly, Alice Thai, Norm Allaire, Bernd Jagla, Michael Mingueneau, Gaetane Nocturne, Xavier Mariette
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Primary Sjögren's syndrome (pSS) is an auto-immune disorder characterized by lymphocytic infiltrates and destruction of the salivary glands. Mechanisms leading to B lymphocytes chronic activation remain partially understood and we assumed that salivary gland epithelial cells (SGECs) might play a key role in B lymphocytes activation and differentiation. <h3>Objectives:</h3> We aimed to study the interactions between SGECs from pSS patients or controls and B lymphocytes. <h3>Methods:</h3> Patients with pSS according to 2016 EULAR/ACR criteria and controls with sicca symptoms were studied. RNASeq analysis was performed on SGECs and B lymphocytes sorted from salivary gland and blood using a FACS ARIA. Enrichment analysis was performed using Ingenuity Pathway Analysis software. Validation of the results was performed by qPCR (Biomark technology). Primary cultured SGECs from pSS patients (n=6) and controls (n=6) were co-cultured with B lymphocytes sorted from healthy donors blood and stimulated with or without PolyIC, INFα or IFNγ for 5 days. Transwell assays were performed. Survival, activation (CD38 positivity) and differentiation of B lymphocytes were assessed at day 5 by flow cytometry. <h3>Results:</h3> The RNASeq analysis of B lymphocytes sorted from salivary gland showed an up-regulation of CD40 and CD48 which are involved in their activation. The analysis of sorted SGECs highlighted IL-7, interferon (IFN) signaling pathways and genes potentially involved in immune responses, including HLA-DRA, BST2 (bone marrow stromal cell antigen 2) and BAFF-R. Co-culture experiments showed an increase of B lymphocytes viability when co-cultured with SGECs compared to B lymphocytes cultured alone (p&lt;0.05). Co-culture with SGECs from pSS compared to controls lead to an increased survival of B lymphocytes (calculated as the percentage of alive co-cultured B lymphocytes – percentage of alive cultured alone B lymphocytes) without stimulation or stimulated with Poly(I:C) (p&lt;0.01) (<b>Figure 1A</b>). Similarly, SGECs from pSS were more likely to induce higher activation of B lymphocytes compared to SGECs from controls, assessed by the percentage of CD38+ B lymphocytes (significant after stimulation with Poly(I:C)) (<b>Figure 1B</b>). To determine whether the activation of B lymphocytes and SGECs required a direct cell contact, we used transwell experiments. Preliminary results suggested that the increase of B lymphocytes viability could depend mostly on soluble factors that are currently being identified and will be communicated at the congress. <h3>Conclusion:</h3> Epithelial cells from patients with pSS have better ability than controls to stimulate survival and activation of B cells. According to preliminary results, this effect could be mediated at least partially by soluble factors. The pathways responsible for this stimulation are being determined by RNASeq analysis of purified epithelial cells and B lymphocytes and inhibitory experiments that can represent new therapeutic perspectives are ongoing. <h3>Disclosure of Interests:</h3> Elodie Rivière: None declared, Juliette Pascaud: None declared, Nicolas Tchitchek: None declared, Saida Boudaoud: None declared, Audrey Paoletti: None declared, Bineta Ly: None declared, Alice Thai Employee of: Alice Thai is employed by Biogen., Norm Allaire Employee of: Norm Allaire is employed by Biogen., Bernd Jagla: None declared, Michael Mingueneau Employee of: Michael Mingueneau is employed by Biogen., Gaetane Nocturne: None declared, Xavier Mariette Grant/research support from: Servier, Consultant for: AstraZeneca, Bristol-Myers Squibb, GlaxoSmithKline, Janssen, Pfizer, UCB Pharma