IL-23 Dependent and Independent Stages of Experimental Arthritis: No Clinical Effect of Therapeutic IL-23p19 Inhibition in Collagen-induced Arthritis

IL-23p19 deficient mice have revealed a critical role of IL-23 in the development of experimental autoimmune diseases, such as collagen-induced arthritis (CIA). Neutralizing IL-23 after onset of CIA in rats has been shown to reduce paw volume, but the effect on synovial inflammation and the immunological autoimmune response is not clear. In this study, we examined the role of IL-23 at different stages of CIA and during T cell memory mediated flare-up arthritis with focus on changes in B cell activity and Th1/Th17 modulation. Anti-IL-23p19 antibody (anti-IL23p19) treatment, starting 15 days after the type II collagen (CII)-immunization but before clinical signs of disease onset, significantly suppressed the severity of CIA. This was accompanied with significantly lower CII-specific IgG1 levels and lower IgG2a levels in the anti-IL-23p19 treated mice compared to the control group. Importantly, neutralizing IL-23 after the first signs of CIA did not ameliorate the disease. This was in contrast to arthritic mice that underwent an arthritis flare-up since a significantly lower disease score was observed in the IL-23p19 treated mice compared to the control group, accompanied by lower synovial IL-17A and IL-22 expression in the knee joints of these mice. These data show IL-23-dependent and IL-23-independent stages during autoimmune CIA. Furthermore, the memory T cell mediated flare-up arthritis is IL-23-mediated. These data suggest that specific neutralization of IL-23p19 after onset of autoimmune arthritis may not be beneficial as a therapeutic therapy for patients with rheumatoid arthritis (RA). However, T cell mediated arthritis relapses in patients with RA might be controlled by anti-IL-23p19 treatment

Dendritic cell-specific deletion of β-catenin results in fewer regulatory T-cells without exacerbating autoimmune collagen-induced arthritis

Dendritic cells (DCs) are professional antigen presenting cells that have the dual ability to stimulate immunity and maintain tolerance. However, the signalling pathways mediating tolerogenic DC function in vivo remain largely unknown. The β-catenin pathway has been suggested to promote a regulatory DC phenotype. The aim of this study was to unravel the role of β-catenin signalling to control DC function in the autoimmune collagen-induced arthritis model (CIA). Deletion of β-catenin specifically in DCs was achieved by crossing conditional knockout mice with a CD11c-Cre transgen

CD4+CCR6+ T cells, but not γδ T cells, are important for the IL-23R-dependent progression of antigen-induced inflammatory arthritis in mice

IL-23 plays an important role in the development of arthritis and the IL-23 receptor (IL-23R) is expressed on different types of T cells. However, it is not fully clear which IL-23R+ T cells are critical in driving T cell-mediated synovitis. We demonstrate, using knock-in IL-23R-GFP reporter (IL-23RGFP/+) mice, that CD4+CCR6+ T cells and γδ T cells, but not CD8+ T cells, express the IL-23R(GFP). During early arthritis, IL-23R(GFP)+CD4+CCR6+ T cells, but not IL-23R(GFP)+ γδ T cells, were present in the inflamed joints. IL-23RGFP/+ mice were bred as homozygotes to obtain IL-23RGFP/GFP (IL-23R deficient/IL-23R−/−) mice, which express GFP under the IL-23R promotor. Arthritis progression and joint damage were significantly milder in IL-23R−/− mice, which revealed less IL-17A+ cells in their lymphoid tissues. Surprisingly, IL-23R−/− mice had increased numbers of IL-23R(GFP)+CD4+CCR6+ and CCR7+CD4+CCR6+ T cells in their spleen compared to WT, and IL-23 suppressed CCR7 expression in vitro. However, IL-23R(GFP)+CD4+CCR6+ T cells were present in the synovium of IL-23R−/− mice at day 4. Finally, adoptive transfer experiments revealed that CD4+CCR6+ T cells and not γδ T cells drive arthritis progression. These data suggest that IL-23R-dependent T cell-mediated synovitis is dependent on CD4+CCR6+ T cells and not on γδ T cells

Lack of IL-17 Receptor A signaling aggravates lymphoproliferation in C57BL/6 lpr mice

Defects in Fas function correlate with susceptibility to systemic autoimmune diseases like autoimmune lymphoproliferative syndrome (ALPS) and systemic lupus erythematosus (SLE). C57BL/6 lpr (B6/lpr) mice are used as an animal model of ALPS and develop a mild SLE phenotype. Involvement of interleukin-17A (IL-17A) has been suggested in both phenotypes. Since IL-17 receptor A is part of the signaling pathway of many IL-17 family members we investigated the role of IL-17 receptor signaling in disease development in mice with a B6/lpr background. B6/lpr mice were crossed with IL-17 receptor A deficient (IL-17RA KO) mice and followed over time for disease development. IL-17RA KO/lpr mice presented with significantly enhanced lymphoproliferation compared with B6/lpr mice, which was characterized by dramatic lymphadenomegaly/splenomegaly and increased lymphocyte numbers, expansion of double-negative (DN) T-cells and enhanced plasma cell formation. However, the SLE phenotype was not enhanced, as anti-nuclear antibody (ANA) titers and induction of glomerulonephritis were not different. In contrast, levels of High Mobility Group Box 1 (HMGB1) and anti-HMGB1 autoantibodies were significantly increased in IL-17RA KO/lpr mice compared to B6/lpr mice. These data show that lack of IL-17RA signaling aggravates the lymphoproliferative phenotype in B6/lpr mice but does not affect the SLE phenotype

Interleukin-17A Is Produced by CD4+ but Not CD8+ T Cells in Synovial Fluid Following T Cell Receptor Activation and Regulates Different Inflammatory Mediators Compared to Tumor Necrosis Factor in a Model of Psoriatic Arthritis Synovitis

Objective: Interleukin-17A (IL-17A) and tumor necrosis factor (TNF) contribute to the pathogenesis of psoriatic arthritis (PsA). However, their functional relationship in PsA synovitis has not been fully elucidated. Additionally, although CD8+ T cells in PsA have been recognized via flow cytometry as a source of IL-17A production, it is not clear whether CD8+ T cells secrete IL-17A under more physiologically relevant conditions in the context from PsA synovitis. This study was undertaken to clarify the roles of IL-17A and TNF in the synovial fluid (SF) from patients with PsA and investigate the impact of CD8+ T cells on IL-17A production. Methods: IL-17A+ T cells were identified by flow cytometry in SF samples from 20 patients with active PsA, blood samples from 22 treatment-naive patients with PsA, and blood samples from 22 healthy donors. IL-17A+ T cells were sorted from 12 PsA SF samples and stimulated using anti-CD3/anti-CD28 or phorbol myristate acetate (PMA) and ionomycin ex vivo, alone (n = 3) or together with autologous monocytes (n = 3) or PsA fibroblast-like synoviocytes (FLS) (n = 5–6). To evaluate the differential allogeneic effects of neutralizing IL-17A and TNF, SF CD4+ T cells and PsA FLS cocultures were also used (n = 5–6). Results: Flow cytometry analyses of SF samples from patients with PsA showed IL-17A positivity for CD4+ and CD8+ T cells (IL-17A, median 0.71% [interquartile range 0.35–1.50%] in CD4+ cells; median 0.44% [interquartile range 0.17–1.86%] in CD8+ T cells). However, only CD4+ T cells secreted IL-17A after ant

IL-17/Th17 mediated synovial inflammation is IL-22 independent

ABSTRACT Background: Interleukin (IL)-17A and Th17 cells are critically involved in T cell-mediated synovial inflammation. Besides IL-17A, Th17 cells produce IL-22. Recently, Th22 cells were discovered, which produce IL- 22 in the absence of IL-17. However, it remains unclear whether IL-22 and Th22 cells contribute to T cellmediated synovial inflammation. Therefore, we examined the potential of IL-22 and Th22 cells to induce synovial inflammation and whether IL-22 is required for T cell-mediated experimental arthritis. Methods: Peripheral and synovial Th17 and Th22 cells were identified and sorted from patients with rheumatoid arthritis (RA). Co-culture experiments of these primary T cell populations with RA synovial fibroblasts (RASF) were performed. The in vivo IL-22 contribution to synovial inflammation was investigated by inducing T cell-mediated arthritis in IL-22 deficient mice and wild-type mice. Resu

Enhanced Expression of Bruton’s Tyrosine Kinase in B Cells Drives Systemic Autoimmunity by Disrupting T Cell Homeostasis

Upon BCR stimulation, naive B cells increase protein levels of the key downstream signaling molecule Bruton's tyrosine kinase (BTK). Transgenic CD19-hBtk mice with B cell specific BTK overexpression show spontaneous germinal center formation, antinuclear autoantibodies, and systemic autoimmunity resembling lupus and Sjogren syndrome. However, it remains unknown how T cells are engaged in this pathology. In this study, we found that CD19-hBtk B cells were high in IL-6 and IL-10 and disrupted T cell homeostasis in vivo. CD19-hBtk B cells promoted IFN-gamma production by T cells and expression of the immune-checkpoint protein ICOS on T cells and induced follicular Th cell differentiation. Crosses with CD40L-deficient mice revealed that increased IL-6 production and autoimmune pathology in CD19-hBtk mice was dependent on B T cell interaction, whereas IL-10 production and IgM autoantibody formation were CD40L independent. Surprisingly, in Btk-overexpressing mice, naive B cells manifested increased CD86 expression, which was dependent on CD40L, suggesting that T cells interact with B cells in a very early stage of immune pathology. These findings indicate that increased BTK-mediated signaling in B cells involves a positive-feedback loop that establishes T cell propagated autoimmune pathology, making BTK an attractive therapeutic target in autoimmune disease

GATA-3 protects against severe joint inflammation and bone erosion and reduces differentiation of Th17 cells during experimental arthritis

Objective. Rheumatoid arthritis is associated with the infiltration of T helper cells into the joints. It is unclear whether interferon-γ (IFNγ)-producing Th1 cells or the novel T helper subset, interleukin-17 (IL-17)-producing Th17 cells, are the pathogenic mediators of joint inflammation in chronic nonautoimmune arthritis. Therefore, this study was aimed at examining whether the Th2-specific transcription factor GATA-3 can regulate arthritis, in an experimental murine model, by modulating Th1 and/or Th17 cell polarization. Methods. Arthritis was induced with methylated bovine serum albumin (mBSA) in both wild-type and CD2 T cell-specific GATA-3 (CD2-GATA-3)-transgenic mice. At days 1 and 7 after the induction of arthritis, knee joints were scored macroscopically for arthritis severity and for histologic changes. Single-cell suspensions were generated from the spleens, lymph nodes, and inflamed knee joints. Cytokine expression by CD4+ T cells was determined using flow cytometry, and IL-17 expression in the inflamed knee joints was determined by enzyme-linked immunosorbent assay. Analyses of gene expression were performed for Th17-associated factors. Results. Wild-type mice developed severe joint inflammation, including massive inflammatory cell infiltration and bone erosion that increased significantly over time, reaching maximal arthritis scores at day 7. In contrast, only mild joint inflammation was observed in CD2-GATA-3-transgenic mice. This mild effect was further accompanied by systemic and local reductions in the numbers of IL-17+IFNγ- and IL-17+IFNγ+, but not IL-17-IFNγ+, CD4+ T cells, and by induction of Th2 cytokine expression. Moreover, GATA-3 overexpression resulted in reduced gene expression of the Th17-associated transcription factor retinoic acid-related orphan receptor γt. Conclusion. These results indicate that enforced GATA-3 expression protects against severe joint inflammation and bone erosion in mice, accompanied by reduced differentiation of Th17 cells, but not Th1 cells, during mBSA-induced arthritis