In juvenile idiopathic arthritis (JIA) inflammatory T cells and their produced cytokines are drug targets and play a role in disease pathogenesis. Despite their clinical importance, the sources and types of inflammatory T cells involved remain unclear. T cells respond to polarizing factors to initiate types of immunity to fight infections, which include immunity types 1 (T1), 2 (T2), and 3 (T17). Polarizing factors drive CD4+ T cells towards T helper (Th) cell subtypes and CD8+ T cells towards cytotoxic T cell (Tc) subtypes. T1 and T17 polarization are associated with autoimmunity and production of the cytokines IFNγ and IL-17 respectively. We show that JIA and child healthy control (HC) peripheral blood mononuclear cells are remarkably similar, with the same frequencies of CD4+ and CD8+ naïve and memory T cell subsets, T cell proliferation, and CD4+ and CD8+ T cell subsets upon T1, T2, and T17 polarization. Yet, under T1 polarizing conditions JIA cells produced increased IFNγ and inappropriately produced IL-17. Under T17 polarizing conditions JIA T cells produced increased IL-17. Gene expression of IFNγ, IL-17, Tbet, and RORγT by quantitative PCR and RNA sequencing revealed activation of immune responses and inappropriate activation of IL-17 signaling pathways in JIA polarized T1 cells. The polarized JIA T1 cells were comprised of Th and Tc cells, with Th cells producing IFNγ (Th1), IL-17 (Th17), and both IFNγ-IL-17 (Th1.17) and Tc cells producing IFNγ (Tc1). The JIA polarized CD4+ T1 cells expressed both Tbet and RORγT, with higher expression of the transcription factors associated with higher frequency of IL-17 producing cells. T1 polarized naïve CD4+ cells from JIA also produced more IFNγ and more IL-17 than HC. We show that in JIA T1 polarization inappropriately generates Th1, Th17, and Th1.17 cells. Our data provides a tool for studying the development of heterogeneous inflammatory T cells in JIA under T1 polarizing conditions and for identifying pathogenic immune cells that are important as drug targets and diagnostic markers.

Objective. T helper cells develop into discrete Th1, Th2 or Th17 lineages that selectively express IFN-gamma, IL-4/IL-5/IL-13, or IL-17, respectively and actively silence signature cytokines expressed by opposing lineages. Our objective was to compare Th1, Th2 and Th17 polarization in cell culture models using JIA patient samples. Methods. Peripheral blood mononuclear cells were isolated from JIA or healthy prepubescent children. T cell naive and memory phenotypes were assessed by flow cytometry. T cell proliferation was measured using a fluorescence-based assay. Th cell cultures were generated in vitro and IFN-gamma, IL-17, and TNF-alpha measured by ELISA and flow cytometry. Results. JIA Th1 cells produced increased IFN-gamma and inappropriately produced IL-17. JIA Th17 cells produced increased IL-17. JIA Th1 cell cultures develop dual producers of IFN-gamma and IL-17, which are Th1.17 cells. JIA Th1 cultures expressed elevated levels of both T-bet and ROR-gamma-T. RNA sequencing confirmed activation of immune responses and inappropriate activation of IL-17 signaling pathways in Th1 cultures. A subset of JIA patient samples was disproportionally responsible for the enhanced IFN-gamma and IL-17 phenotype and Th1.17 phenotype. Conclusions. This study reveals that JIA patient uncommitted T cell precursors, but not healthy children, inappropriately develop into inflammatory effector Th1.17 and Th17 cells under Th1 polarizing conditions.