Polyarticular juvenile idiopathic arthritis has a distinct co-inhibitor receptor profile.

Objectives: Juvenile Idiopathic Arthritis (JIA) is the most common rheumatic disease of childhood; the pathogenesis is associated with T cell activation. T cell activation can be counter-balanced by signals generated by inhibitory receptors (IRs) such as CTLA-4, PD-1, LAG-3, and TIM-3. Here, we identify the role of IRs in the pathogenesis of different JIA subtypes.
Methods: In total, we included 67 oligoarticular JIA, 12 IgM-RF negative polyarticular JIA, 17 enthesitis related arthritis, 11 systemic JIA patients and 10 healthy controls. We collected plasma (and synovial fluid) samples from the patients either at the onset or during a flare of their disease. We measured the soluble levels of co-IRs (IL-2Rα, 4-1BB, CD86, TGF-β1, CTLA-4, PD-L1, PD-1, TIM-3, LAG- 3, Galectin-9) by cytometric bead array kits and their cellular expression (PD-1, CTLA-4, TIM-3, LAG-3) by flow cytometry. We compared the plasma levels and cellular expressions of different co-IRs within different JIA subgroups.
Results: The polyarticular-JIA group was different from the three other examined JIA subgroups, having higher levels of plasma sCTLA-4(p< 0.001), sPD-1(p< 0.05), and s4-1BB(p< 0.05) when compared with the other JIA subgroups and healthy controls. We analyzed the cellular surface expression of different co-IRs on the PBMCs of different JIA subtypes. Similar to plasma levels, both the percentage(p< 0.05) and the MFI (mean fluorescence intensity) (p< 0.01) of CTLA4 expression were higher in the poly-JIA subgroup.
Conclusion: This is the first report studying the expression profile of different co-IRs in different subtypes of JIA. Polyarticular JIA patients had a different co-IR profile, having more CTLA-4, PD-1 and 4-1BB in their plasma than the other subtypes of JIA.
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