Background/Purpose: Primary Sjögren’s syndrome (pSS) is an auto-immune disorder characterized by a chronic hyperactivation of B lymphocytes. We previously showed that salivary gland epithelial cells (SGECs) could play a role in this B-cell activation (1). We developed a co-culture model of SGECs and B lymphocytes and showed that SGECs from pSS induced a higher survival and activation (when stimulated with Poly(I:C)) of B lymphocytes compared to SGECs from controls. The aims of this study were to identify the factors involved in the activation of B lymphocytes by pSS SGECs and to evaluate the efficacy of different treatments for inhibiting this interaction.

Methods: Patients with pSS according to 2016 EULAR/ACR criteria and controls were studied. Primary cultured SGECs from pSS and from controls were stimulated or not with Poly(I:C) and co-cultured with B lymphocytes sorted from healthy donors blood. Transwell assays were performed. Inhibition experiments with anti-BAFF antibody (belimumab) 10µg/mL, anti-JAK1/3 (tofacitinib) 50nM, anti-APRIL antibody 2µg/mL (kindly provided by P. Schneider) and anti-IL-6 receptor (tocilizumab) 50 µg/mL were performed. Survival and activation (CD38) of B lymphocytes were assessed by flow cytometry after 5 days of co-culture. Cytokines concentrations were assessed in supernatants (Luminex). Statistical analyses were performed with Prism using Mann-Whitney test (not paired data) and Wilcoxon (paired data) tests.

Results: The induction of B lymphocytes survival and activation was mostly dependent on soluble factors as assessed by transwell assays (Figure 1). Soluble factors were assessed in co-cultures supernatants. BAFF was detectable in co-cultures supernatants only with stimulation with poly(I:C), but adding belimumab to the co-culture did not inhibit the effect of SGECs on B lymphocytes survival and activation, even in the condition stimulated with Poly(I:C). SGECs were able to secrete APRIL and, interestingly, the co-culture of SGECs from pSS with B lymphocytes increased the secretion of APRIL by SGECs compared to SGECs cultured alone (Figure 2). However, inhibition by an anti-APRIL antibody did not decrease survival of co-cultured B lymphocytes. IL-6 was secreted by SGECs in co-culture supernatants (Figure 2). However, addition of tocilizumab in the co-culture did not inhibit B lymphocytes survival and activation by SGECs. Similar results were obtained with tofacitinib. Lastly, chemokines such as CXCL10 and CXCL13 were also detected in SGECs supernatants (Figure 2).

Conclusion: Several soluble factors secreted by SGECs could play a role in the interactions between SGECs and B lymphocytes. However, targeting one by one the suspected cytokines did not allow identifying a single responsible factor suggesting that a combination of several factors could be required. In the context of the NECESSITY project, further inhibition experiments with the combination of leflunomide and hydroxychloroquine and with inhibitors of specific B-cell mediators as Btk and Pi3K are planned and will be presented at the congress.

(1) Rivière E, Pascaud J, Tchitchek N, et al. Crosstalk between salivary gland epithelial cells and B lymphocytes in primary Sjögren’s syndrome [abstract]. EULAR 2019

Figure 1

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/an-ex-vivo-assay-to-evaluate-the-efficacy-of-different-treatments-for-inhibiting-b-lymphocytes-activation-by-salivary-gland-epithelial-cells-in-sjogrens-syndrome/