Anne M. Pesenacker

CD161 defines the subset of FoxP3+ T cells capable of producing proinflammatory cytokines

Regulatory FoxP3+CD4+ T cells (Treg) are vital for maintaining the balance between tolerance, adequate immune response, and autoimmunity. Despite this immunoregulatory role, it has been shown that Treg may also produce proinflammatory cytokines. Here we present a distinct population of Treg, defined by CD161 expression, as the major source of FoxP3+ Treg-derived proinflammatory cytokines. CD161+ Treg can be followed throughout development, from thymus and cord blood to healthy child and adult samples. CD161+ Treg display anergy, are suppressive in cocultures with conventional T cells (Tconv), and possess a predominantly demethylated Treg-specific demethylated region of the FOXP3 locus. In addition to the production of interleukin (IL) 17A, interferon γ, and IL-2, CD161+FoxP3+ cells share markers with Tconv, including expression of the transcription factors retinoic acid-related orphan receptor Cv2 (RORCv2) and T-cell-specific T-box transcription factor (Tbet). Expression of CD161 and enrichment for cytokine production are stable characteristics of CD161+ Treg upon both short- and longer-term culture in vitro. Additionally, CD161+ Treg are highly enriched within the inflammatory environment of childhood arthritis, suggesting a role in disease. Our data therefore demonstrate that CD161+FoxP3+ T cells are a novel Treg subset, found in health and disease, which display high proinflammatory potential but also exhibit hallmark Treg characteristics.

Th1 and Th17 cell subpopulations are enriched in the peripheral blood of patients with systemic juvenile idiopathic arthritis

Objective. The role of the adaptive immune system has not been explored in detail compared with the innate immune system in systemic JIA (sJIA) pathogenesis. The aim of this study was to examine the phenotype of circulating peripheral blood CD4+ T-cell subpopulations in a cross-sectional study of sJIA patients during disease remission on medication and during acute flare of the disease. Methods. Flow cytometry was used to examine the phenotype and cytokine production of IFNγ-, IL-4- and IL-17-producing CD4+ T cells in the peripheral blood of 10 sJIA patients with active disease, 9 sJIA with inactive disease, 14 JIA patients with oligoarticular onset, 10 adult control subjects and 10 age-matched control subjects. In parallel, we examined the proportion of FoxP3+ Tregs. Results. IFNγ- and IL-17-producing CD4+ T cells and IL-17-producing CD3+CD4− T cells were present at higher proportions in the peripheral blood of sJIA patients, irrespective of their disease status. Our data also confirm the known increase of the proportions of IFNγ-producing Th1 cells with increasing age and suggest an increase with age in the IL-17-producing CD4+ T-cell population. Conclusion. This study is the first to describe significantly higher proportions of Th1 and Th17 T helper cell subsets in the peripheral blood of sJIA patients. These proinflammatory cells may play a pathogenic role in sJIA. Our data also emphasize the importance of using paediatric age-matched control subjects when evaluating the T-cell cytokine profile in JIA.

T cell expression of granulocyte-macrophage colony-stimulating factor in juvenile arthritis is contingent upon Th17 plasticity.

Granulocyte–macrophage colony stimulating factor (GM‐CSF) is a potent inflammatory mediator that is responsible for recruitment and activation of innate immune cells. Recent data from murine studies have identified Th17 cells as a key source of GM‐CSF and suggest that T cell–derived GM‐CSF is instrumental in the induction of autoimmune disease. The present study was undertaken to analyze the expression of T cell–derived GM‐CSF in the joints of patients with juvenile idiopathic arthritis (JIA) and to investigate the differentiation of Th17 cells and how this relates to GM‐CSF+ T helper cells.

Hypomethylation at the regulatory T cell-specific demethylated region in CD25hi T cells is decoupled from FOXP3 expression at the inflamed site in childhood arthritis.

The maintenance of FOXP3 expression in CD25hi regulatory T cells (Tregs) is crucial to the control of inflammation and essential for successful Treg transfer therapies. Coexpression of CD25 and FOXP3 in combination with a hypomethylated region within the FOXP3 gene, called the Treg-specific demethylated region (TSDR), is considered the hallmark of stable Tregs. The TSDR is an epigenetic motif that is important for stable FOXP3 expression and is used as a biomarker to measure Treg lineage commitment. In this study, we report that, unlike in peripheral blood, CD4+ T cell expression of CD25 and FOXP3 is frequently dissociated at the inflamed site in patients with juvenile idiopathic arthritis, which led us to question the stability of human Tregs in chronic inflammatory environments. We describe a novel CD4+CD127loCD25hi human T cell population that exhibits extensive TSDR and promoter demethylation in the absence of stable FOXP3 expression. This population expresses high levels of CTLA-4 and can suppress T conventional cell proliferation in vitro. These data collectively suggest that this population may represent a chronically activated FOXP3lo Treg population. We show that these cells have defects in IL-2 signaling and reduced expression of a deubiquitinase important for FOXP3 stability. Clinically, the proportions of these cells within the CD25hi T cell subset are increased in patients with the more severe courses of disease. Our study demonstrates, therefore, that hypomethylation at the TSDR can be decoupled from FOXP3 expression in human T cells and that environment-specific breakdown in FOXP3 stability may compromise the resolution of inflammation in juvenile idiopathic arthritis.

T regulatory cells in childhood arthritis - novel insights.

In recent years, there have been many new developments in the field of regulatory T cells (Treg), challenging the consensus on their behaviour, classification and role(s) in disease. The role Treg might play in autoimmune disease appears to be more complex than previously thought. Here, we discuss the current knowledge of regulatory T cells through animal and human research and illustrate the recent developments in childhood autoimmune arthritis (juvenile idiopathic arthritis (JIA)). Furthermore, this review summarises our understanding of the fields and assesses current and future implications for Treg in the treatment of JIA.

Immunological characteristics and T-cell receptor clonal diversity in children with systemic juvenile idiopathic arthritis undergoing T-cell-depleted autologous stem cell transplantation

Children with systemic Juvenile Idiopathic Arthritis (sJIA), the most severe subtype of JIA, are at risk from destructive polyarthritis and growth failure, and corticosteroids as part of conventional treatment can result in osteoporosis and growth delay. In children where there is failure or toxicity from drug therapies, disease has been successfully controlled by T‐cell‐depleted autologous stem cell transplantation (ASCT). At present, the immunological basis underlying remission after ASCT is unknown. Immune reconstitution of T cells, B cells, natural killer cells, natural killer T cells and monocytes, in parallel with T‐cell receptor (TCR) diversity by analysis of the β variable region (TCRVb) complementarity determining region‐3 (CDR3) using spectratyping and sequencing, were studied in five children with sJIA before and after ASCT. At time of follow up (mean 11·5 years), four patients remain in complete remission, while one child relapsed within 1 month of transplant. The CD8+ TCRVb repertoire was highly oligoclonal early in immune reconstitution and re‐emergence of pre‐transplant TCRVb CDR3 dominant peaks was observed after transplant in certain TCRVb families. Further, re‐emergence of pre‐ASCT clonal sequences in addition to new sequences was identified after transplant. These results suggest that a chimeric TCR repertoire, comprising T‐cell clones developed before and after transplant, can be associated with clinical remission from severe arthritis.

Regulatory T cells from the inflamed joints of patients with juvenile idiopathic arthritis (JIA) are dysregulated and display a pro-inflammatory profile

Background Regulatory T cells (Treg) are abundant in the inflamed joints of children with JIA. However the high number of Treg is not able to control the inflammation within the joint, suggesting a shortcoming of their regulatory function. It has been suggested that Treg can develop a proinflammatory profile that is specifically related to the local pro-inflammatory response. In this study we investigated whether Treg within the inflamed joint of JIA patients express pro-inflammatory markers. Aim This study examines the pro-inflammatory potential of Treg and how this might impact their regulatory function within the inflamed joint of children with JIA. Methods Peripheral blood mononuclear cells (PBMC) and synovial fluid mononuclear cells (SFMC) of 12 children with JIA were analysed by flow cytometry for Treg, their maturation and lineage markers, and cytokine production.

PReS-FINAL-1002: Dissecting the dissociation of foxp3 and cd25 expression on cd4+ t cells in synovial fluid identifies three distinct subpopulations of human t regulatory cells present at the chronically inflamed site

T regulatory cells (Treg), vital to prevent autoimmunity, are defined by expression of FoxP3 in combination with high CD25 and low CD127 expression. It has been reported, however, that upon in vitro activation, conventional T cells (Tconv) can manifest phenotypic marks associated with Treg and, as such, expression of these markers alone is insufficient to determine Treg commitment. A unique feature of Treg is the presence of a Treg specific demethylated region (TSDR) in intron 1 of the FOXP3 gene. This distinguishes activated Tconv from bona fide Treg. In CD4+ T cells from the joints of children with JIA we have observed a clear dissociation of CD25 and FoxP3 expression. The relationship between CD25, CD127 and FoxP3 expression and commitment to Treg lineage at the inflamed site is unclear; meaningful investigation is hampered by the technical difficulties in isolating cells based on FoxP3 status.

PReS-FINAL-2069: T cells secreting granulocyte-macrophage colony stimulating factor (GM-CSF) within the inflammed joint originate from an "EX-Th17" population

Since 2003, the established paradigm of T cell immunology has defined interleukin (IL)-17 as a dominant Th17 cell derived cytokine driving autoimmune disease. Recent murine studies have challenged this, identifying GM-CSF as a Th17 related cytokine necessary and sufficient for the induction of autoimmunity. The origin of GM-CSF+ T cells and their relationship with IL-17 secreting cells is unclear in human autoimmune disease. Trials of biologic agents targeting the GM-CSF pathway show promise in rheumatoid arthritis, so it is important to establish if GM-CSF contributes to the inflammatory environment of the arthritic joint in Juvenile Idiopathic Arthritis (JIA).

18th Pediatric Rheumatology European Society (PReS) Congress Bruges, Belgium. 14-18 September 2011. Abstracts.

Regulatory T cells from the inflamed joints of patients with juvenile idiopathic arthritis (JIA) are dysregulated and display a pro-inflammatory profile