OP0176 Rna sequencing detection of gene dysregulation in b cells sorted from salivary gland tissue and peripheral blood reveals new pathways involved in sjÖgren’s syndrome pathophysiology
Authors: E. Rivière, N. Tchitchek, G. Nocturne, J. Pascaud, S. Boudaoud, A. Thai, N. Allaire, B. Jagla, M. Mingueneau, X. Mariette
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Primary Sjögren's syndrome (pSS) is a chronic auto-immune disorder characterised by lymphocytic infiltrates and destruction of the salivary glands (SG). Chronic B cell activation, the secretion of autoantibodies and the critical role of BAFF have been demonstrated. However, mechanisms leading to B cells dysregulation remain partially understood. <h3>Objectives</h3> To establish transcriptomic maps of the B cells sorted from the SG and from blood using RNASeq analysis. <h3>Methods</h3> Patients had pSS according to 2016 EULAR/ACR criteria and controls had sicca symptoms without any antibodies and with normal SG biopsy. B cells were sorted from SG biopsies and from blood using a FACS ARIA. Total RNASeq profiling was performed using MiSeq (Illumina). Statistical analysis (DESeq2) identified differentially expressed genes between pSS and controls in B cells sorted from SG (9 pSS and 4 controls), from blood (16 pSS and 7 controls); and between B cells sorted from SG and blood in the same patients (4 pSS). Functional enrichment analysis was performed using Ingenuity Pathway Analysis. <h3>Results</h3> The pSS vs controls comparison in B cells sorted from SG identified up-regulated genes involved in activation of B cells including CD48, CD22 and CD40. TLR10, which is involved in innate immunity was also up-regulated in pSS. The analysis of the non-coding expressed RNAs showed an up-regulation of Mir155 which is essential for B cell differentiation and antibody production (table 1A). In B cells sorted from blood, TLR7 and the downstream signalling molecule IRF7 were up-regulated in pSS. Additionally, IL-6 which is involved in B cells growth was up-regulated (table 1B). Enrichment analysis highlighted EIF2 signalling pathway, interferon (IFN) signalling pathway and role of JAK in IFN signalling. The paired comparison between B cells from SG and from blood identified up-regulated genes including CD138, a plasma cell marker, IL-6, TLR5 and IFN induced genes (table 1C). Mir155HG was also up-regulated. These results need to be confirmed by RT-qPCR and additional analysis of the non-coding expressed RNA is ongoing. Table 1 Selection of genes differentially expressed between pSS and controls in B cells sorted from biopsy (1A), blood (1B) and between SG and blood B cells from the same pSS patients (1C) <h3>Conclusions</h3> This study allowed exploring the mechanisms that support B cell activation in pSS focusing on tissue resident and circulating cells. Our data confirmed the B cell activation and differentiation through several markers including CD40, CD22, CD48, CD138 and highlighted the role of innate immunity with the TLRs and key pathways including IFN and JAK signalling. Lastly, the role of an epigenetic regulation of Ig secretion is suggested in tissue infiltrating B cells through mir155 expression. Precise understanding of these dysregulation should offer development of new targeted therapeutic perspectives for patients. <h3>Acknowledgements</h3> Arthritis Fondation Courtin for providing a PhD fellowship <h3>Disclosure of Interest</h3> None declared