Aberrant Naive CD4-Positive T Cell Differentiation in Systemic Juvenile Idiopathic Arthritis Committed to B Cell Help

Objective Systemic juvenile idiopathic arthritis (JIA) features characteristics of autoinflammation and autoimmunity, culminating in chronic arthritis. In this study, we hypothesized that aberrant or incomplete polarization of T helper cells contributes to disease pathology.Methods Cells or serum samples were obtained from healthy controls (n = 72) and systemic JIA patients (n = 171). Isolated naive T helper cells were cultured under Th1, Th17, and T follicular helper (Tfh) or T peripheral helper (Tph)-polarizing conditions and were partly cocultured with allogenic memory B cells. Cell samples were then analyzed for surface marker, transcription factor, and cytokine expression, as well as plasmablast generation. Serum samples were subjected to multiplexed bead and self-antigen arrays and enzyme-linked immunosorbent assays, and all data were compared to retrospective RNA profiling analyses.Results Differentiation of systemic JIA-naive T helper cells toward Th1 cells resulted in low expression levels of interferon-gamma (IFN gamma) and eomesodermin, which was associated in part with disease duration. In contrast developing Th1 cells in patients with systemic JIA were found to produce elevated levels of interleukin-21 (IL-21), which negatively correlated with cellular expression of IFN gamma and eomesodermin. In both in vitro and ex vivo analyses, IL-21 together with programmed cell death 1 (PD-1), inducible T cell costimulator (ICOS), and CXCR5 expression induced naive T helper cells from systemic JIA patients to polarize toward a Tfh/Tph cell phenotype. Retrospective analysis of whole-blood RNA-sequencing data demonstrated that Bcl-6, a master transcription factor in Tfh/Tph cell differentiation, was overexpressed specifically in patients with systemic JIA. Naive T helper cells from systemic JIA patients which were stimulated in vitro promoted B cellular plasmablast generation, and self-antigen array data indicated that IgG reactivity profiles of patients with systemic JIA differed from those of healthy controls.Conclusion In the pathogenesis of systemic JIA, skewing of naive T helper cell differentiation toward a Tfh/Tph cell phenotype may represent an echo of autoimmunity, which may indicate the mechanisms driving progression toward chronic destructive arthritis.

Automated summary

This study found that aberrant or incomplete polarization of T helper cells may contribute to the pathological processes in systemic juvenile idiopathic arthritis (sJIA).