OP0152 OLIGOARTICULAR JUVENILE IDIOPATHIC ARTHRITIS DOES NOT SHOW SIGNS OF T-CELL EXHAUSTION, IN SPITE OF INCREASED EXPRESSION OF CO-INHIBITORY RECEPTORS
Authors: Erdal Sag, Selcan Demir, Morten Aagard Nielsen, Malene Hvid, Egemen Turhan, Yelda Bilginer, Seza Özen, Bent Deleuran
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Oligoarticular Juvenile idiopathic arthritis (O-JIA) is a common inflammatory joint disease in children, driven by continuous local T-cell activation.[1] T cell activation is counter-balanced via signals generated by co-inhibitory receptors (co-IRs) such CTLA-4, PD-1, LAG-3, and TIM-3.[2] <h3>Objectives</h3> Here we identify the role of co-IRs in the pathogenesis of O-JIA. <h3>Methods</h3> Paired synovial fluid (SF) and plasma, PBMCs and SFMCs, were obtained from O-JIA patients together with clinical data (n=14). Plasma from healthy controls (HC, n=14); paired SF and plasma from 5 non-arthritis juvenile orthopedic patients (OC, n=5) served as controls. Soluble levels of co-IRs were measured by ELISA and their cellular expression by flow cytometry. Spontaneously differentiated fibroblast like synoviocytes (FLS) from SFMCs were co-cultured with autologous PBMCs/SFMCs and used as an <i>ex-vivo</i> disease model. Functional effects of co-IRs were evaluated via blocking them with checkpoint inhibitors in these <i>ex-vivo</i> disease models. <h3>Results</h3> In O-JIA patients, increased levels of sPD-1, sLAG-3 and sTIM-3, but not sCTLA-4, were present in the SF compared with plasma. (Figure 1A) There was a close correlation between sPD-1 levels in the plasma and SF (r=0.65, p=0.029). In plasma, sTIM-3 levels correlated with sPD-1 levels (r=0.84, p=0.001) and sLAG-3 levels (r=0.68, p=0.021). In the SF, there was a significant correlation between sLAG-3 levels and sPD-1 levels (r=0.54, p=0.047). None of the soluble co-IR levels correlated with disease activity scores. Plasma and SF levels of sLAG-3 and sTIM-3 were higher in O-JIA patients when compared with HC and OC. (Figure 1A) On the CD3+CD4+CD45RO+ T cells, the surface expression of PD-1 (p=0.02), LAG-3 (p=0.001), TIM-3 (p&lt;0.001), but not CTLA-4 (p=0.48), were higher in the SFMC compared with PBMC. MHC class II expression was induced on FLS when these were co-cultured with autologous PBMCs and SFMCs, together with an increased Monocyte Chemoattractant Protein-1 (MCP-1) production. (Figure 1B) Only addition of neutralizing anti-LAG3 antibodies significantly increased the MCP-1 production in PBMC monocultures (p&lt;0.01) and FLS+PBMC co-cultures (p&lt;0.01). PBMCs and SFMCs produced significantly higher levels of IFN-γ after CD3/CD28 activation both in monocultures and co-cultures (p&lt;0.001), but they were not affected from addition of any of the checkpoint inhibitor. <h3>Conclusion</h3> This is the first report studying the effects of different co-IRs in O-JIA. Both the soluble levels and the surface expressions of the co-IRs were higher at the site of inflammation in O-JIA. SFMCs and PBMCs of O-JIA patients are not exhausted, based on their ability to respond to CD3/CD28 activation. This is opposite to what has been shown in adult inflammatory arthritis.[3] Co-cultures of autologous FLSs and PBMCs/SFMCs may serve as an <i>ex-vivo</i> arthritis model to perform functional analysis. LAG-3 stands out among the co-IRs and might play a role in O-JIA pathogenesis and a potential therapeutic option for O-JIA. <h3>References</h3> [1] Wedderburn, L.R., et al., Int Immunol, 2001. 13(12): p. 1541-50. [2] Wherry, E.J. and M. Kurachi, Nat Rev Immunol, 2015. 15(8): p. 486-99. [3] Frenz, T., et al., J Allergy Clin Immunol, 2016. 138(2): p. 586-589e10. <h3>Acknowledgement</h3> This work was supported by a research grant from FOREUM Foundation for Research in Rheumatology <h3>Disclosure of Interests</h3> Erdal Sag: None declared, Selcan Demir: None declared, Morten Aagard Nielsen: None declared, Malene Hvid: None declared, Egemen Turhan: None declared, Yelda Bilginer: None declared, Seza Özen Consultant for: Seza Ozen is receiving consultancy fees from Novartis, Speakers bureau: Roche, Bent Deleuran: None declared