Cells In Collagen-induced Arthritis Research Articles

ITGA5+ synovial fibroblasts orchestrate proinflammatory niche formation by remodelling the local immune microenvironment in rheumatoid arthritis.

To investigate the phenotypic heterogeneity of tissue-resident synovial fibroblasts and their role in inflammatory response in rheumatoid arthritis (RA). We used single-cell and spatial transcriptomics to profile synovial cells and spatial gene expressions of synovial tissues to identify phenotypic changes in patients with osteoarthritis, RA in sustained remission and active state. Immunohistology, multiplex immunofluorescence and flow cytometry were used to identify synovial fibroblasts subsets. Deconvolution methods further validated our findings in two cohorts (PEAC and R4RA) with treatment response. Cell coculture was used to access the potential cell-cell interactions. Adoptive transfer of synovial cells in collagen-induced arthritis (CIA) mice and bulk RNA sequencing of synovial joints further validate the cellular functions. We identified a novel tissue-remodelling CD45-CD31-PDPN+ITGA5+ synovial fibroblast population with unique transcriptome of POSTN, COL3A1, CCL5 and TGFB1, and enriched in immunoregulatory pathways. This subset was upregulated in active and lympho-myeloid type of RA, associated with an increased risk of multidrug resistance. Transforming growth factor (TGF)-β1 might participate in the differentiation of this subset. Moreover, ITGA5+ synovial fibroblasts might occur in early stage of inflammation and induce the differentiation of CXCL13hiPD-1hi peripheral helper T cells (TPHs) from naïve CD4+ T cells, by secreting TGF-β1. Intra-articular injection of ITGA5+ synovial fibroblasts exacerbates RA development and upregulates TPHs in CIA mice. We demonstrate that ITGA5+ synovial fibroblasts might regulate the RA progression by inducing the differentiation of CXCL13hiPD-1hi TPHs and remodelling the proinflammatory microenvironments. Therapeutic modulation of this subpopulation could therefore be a potential treatment strategy for RA.

Diminished LAG3+ B cells correlate with exacerbated rheumatoid arthritis

Background Lymphocyte activation gene-3 (LAG3) positive B cells have been identified as a novel regulatory B cell subset, while the role of LAG3+ B cells in the pathogenesis of rheumatoid arthritis (RA) remains elusive. Materials and methods Peripheral blood mononuclear cells (PBMCs) from RA, osteoarthritis (OA) patients and healthy volunteers were collected for flow cytometry staining of LAG3+ B cells. Their correlation with RA patient clinical and immunological features were analyzed. Moreover, the frequencies of LAG3+ B cells in collagen-induced arthritis (CIA) mice and naive mice were also detected. Results A significant decrease of LAG3+ B cells was observed in RA patients as compared with healthy individuals and OA patients. Notably, the frequencies of LAG3+ B cells were negatively correlated with tender joint count (r = −0.4301, p = .0157) and DAS28-ESR (r = −0.4018, p = .025) in RA patients. In CIA mice, LAG3+ B cell frequencies were also decreased and negatively correlated with the CIA arthritis score. Conclusions Impairment of LAG3+ B cells potentially contributes to RA development. Reconstituting LAG3+ B cells might provide novel therapeutic strategies for the persistent disease. Key messages LAG3+ B cells have been identified as a novel regulatory B cell subset. However, its role in the pathogenesis of RA remains unknown. This study revealed the decreased frequency of LAG3+ B cells in RA patients. Notably, LAG3+ B cells were negatively correlated with RA disease activity including the tender joint count and DAS28-ESR. In CIA mice, LAG3+ B cell frequencies were also decreased and negatively correlated with the CIA arthritis score. Reconstitution of LAG3+ B cells might provide novel therapeutic strategies for disease perpetuation.

Development of a 64Cu-labeled CD4+ T cell targeting PET tracer: evaluation of CD4 specificity and its potential use in collagen-induced arthritis

BackgroundCD4+ T cells are central inflammatory mediators in the pathogenesis of autoimmune rheumatoid arthritis (RA), as they are one of the dominating cell types in synovial inflammation. Molecular imaging of CD4+ T cells has potential role for early detection and monitoring of RA. Here, we developed a new radiotracer for in vivo immunoPET imaging of murine CD4+ T cells and tested it in the collagen-induced arthritis (CIA) mouse model of human RA.ResultsThe tracer, [64Cu]Cu-NOTA-CD4-F(ab)’2 ([64Cu]Cu-NOTA-CD4), was generated from F(ab)’2 fragments of R-anti-mouse CD4 antibodies conjugated to the 2-S-(isothiocyanatbenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) chelator and radiolabeled with copper-64. Accumulation of the tracer and isotype control was evaluated in the CIA model and mice receiving whole-body irradiation (WBI) (5 Gy). The potential of [64Cu]Cu-NOTA-CD4 for response assessment was evaluated in CIA induced mice treated with dexamethasone (DXM). Imaging data were compared with flow cytometry and immunohistochemistry (IHC) of inflammatory cells including CD4+ T cells. [64Cu]Cu-NOTA-CD4 showed increased accumulation in T cell-rich tissues compared with isotype control (p < 0.0001). In addition, reduced accumulation of [64Cu]Cu-NOTA-CD4 was observed in T cell-depleted tissue (p < 0.0001). Flow cytometry and IHC confirmed the increased infiltration of CD4+ T cells in CIA mice.ConclusionsWe developed and evaluated a new radiotracer, [64Cu]Cu-NOTA-CD4, for immunoPET imaging of murine CD4+ T cells. [64Cu]Cu-NOTA-CD4 was successfully synthesized by F(ab)’2 fragments of R-anti-mouse CD4 antibodies conjugated to a chelator and radiolabeled with copper-64. We found that our novel CD4 PET tracer can be used for noninvasive visualization of murine CD4+ T cells.

Effects of α1-adrenoreceptor on Treg cell function in collagen-induced arthritis

Objective: An animal model of collagen-induced arthritis (CIA) was used to investigate the effects of norepinephrine (NE) and α1-adrenoreceptor (α1-AR) on Treg cells in CIA. Methods: Thirty-two male DBA/1 mice were randomly divided into control group and CIA model group. CIA was prepared by intradermal injection of collagen type II (CII, 100 μl) at the tail base of DBA/1 mice. On the 41th day following primary immunization, co-expression of CD4+T and α1-AR in mouse spleens was observed. Protein expressions of α1-AR in the ankle joints and the spleens of mice were measured by Western blot analysis. The CD4+ T cells were isolated from the mouse spleen tissues in CIA mice and treated with NE or α1-AR agonist phenylephrine. Percentage of Treg cells in mouse CD4+ T cells of CIA mice was determined by flow cytometry. Expressions of α1-AR, transforming growth factor-β (TGF-β) and IL-10 in CD4+T cells of CIA mice were assessed by Western blot. Results: Co-expression of CD4 and α1-AR was observed in spleens of both intact and CIA mice. Compared with intace mice, α1-AR expressions in the ankle joints and spleens were down-regulated in CIA mice. NE increased the function of Treg cells in CD4+ T cells of CIA mice compared with that of nothing-treated CD4+T cells of CIA mice. Moreover, the α1-AR agonist phenylephrine increased the Treg cell function in CD4+ T cells of CIA mice relative to that of nothing-treated CD4+T cells of CIA mice. Conclusion: Activating α1-AR on CD4+T cells of CIA mice enhances Treg cell function,facilitating a shift of CD4+T cells toward Treg polarization.

1,25-Dihydroxyvitamin D3 ameliorates collagen-induced arthritis via suppression of Th17 cells through miR-124 mediated inhibition of IL-6 signaling

Abstract Objectives To explore the molecular mechanisms in which vitamin D (VD) regulates T cells, especially Th17 cells in collagen-induced arthritis (CIA). Methods DBA1/J mice induced for CIA were intraperitoneally treated with VD. CIA clinical symptoms and inflammatory responses including Th1/Th17/Tregs percentages were determined and compared. Mouse naïve CD4+ T cells transduced with miR-124 inhibitor or not were polarized to Th17 cells with or without VD. Subsequently, cellular differentiation and IL-6 signaling moleculars were analyzed. Results VD treatment significantly delayed CIA onset, decreased incidence and clinical scores of arthritis, downregulated serum IgG levels and ameliorated bone erosion. VD downregulated IL-17A production in CD4+ T cells while increased CD4+Foxp3+Nrp-1+ cells both in draining lymph nodes and synovial fluid in arthritic mice. VD inhibited Th17 cells differentiation in vivo and in vitro and potentially functioning directly on T cells to restrain Th17 cells through limiting IL-6R expression and its downstream signaling including STAT3 phosphorylation, while these effects were blocked when naïve CD4+ T cells were transduced with miR-124 inhibitor. Conclusions VD treatment ameliorates CIA via suppression of Th17 cells and enhancement of Tregs. miR-124-mediated inhibition of IL-6 signaling, provides a novel explanation for VD’s role on T cells in CIA mice or RA patients and suggests that VD may have treatment implications in rheumatoid arthritis.

1,25-Dihydroxyvitamin D3 Ameliorates Collagen-Induced Arthritis via Suppression of Th17 Cells Through miR-124 Mediated Inhibition of IL-6 Signaling.

Objectives: To explore the molecular mechanisms in which vitamin D (VD) regulates T cells, especially Th17 cells in collagen-induced arthritis (CIA).Methods: DBA1/J mice induced for CIA were intraperitoneally treated with VD. CIA clinical symptoms and inflammatory responses including Th1/Th17/Tregs percentages were determined and compared. Mouse naïve CD4+ T cells transduced with miR-124 inhibitor or not were polarized to Th17 cells with or without VD. Subsequently, cellular differentiation and IL-6 signaling moleculars were analyzed.Results: VD treatment significantly delayed CIA onset, decreased incidence and clinical scores of arthritis, downregulated serum IgG levels and ameliorated bone erosion. VD downregulated IL-17A production in CD4+ T cells while increased CD4+Foxp3+Nrp-1+ cells both in draining lymph nodes and synovial fluid in arthritic mice. VD inhibited Th17 cells differentiation in vivo and in vitro and potentially functioning directly on T cells to restrain Th17 cells through limiting IL-6R expression and its downstream signaling including STAT3 phosphorylation, while these effects were blocked when naïve CD4+ T cells were transduced with miR-124 inhibitor.Conclusions: VD treatment ameliorates CIA via suppression of Th17 cells and enhancement of Tregs. miR-124-mediated inhibition of IL-6 signaling, provides a novel explanation for VD's role on T cells in CIA mice or RA patients and suggests that VD may have treatment implications in rheumatoid arthritis.

Germinal Center B Cells Are Essential for Collagen-Induced Arthritis.

Rheumatoid arthritis (RA) is considered to be a prototypical autoimmune disorder. Several mechanisms have been proposed for the known pathologic function of B cells in RA, including antigen presentation, cytokine secretion, and humoral immunity. The aim of this study was to address the function of B lymphocytes in experimental arthritis. We mapped the adaptive immune response following collagen-induced arthritis (CIA). We subsequently monitored these responses and disease outcomes in genetically modified mouse strains that lack mature B cell or germinal center (GC) functionality in a B cell-intrinsic manner. Following primary immunization, the draining lymph nodes broadly reacted against type II collagen (CII) with the formation of GCs and T cell activation. Mice that lacked mature B cell function were fully protected against CIA and had a severely attenuated ability to mount isotype-switched humoral immune responses against CII. Almost identical results were observed in mice that were selectively deficient in GC responses. Importantly, GC-deficient mice were fully susceptible to collagen antibody-induced arthritis. We identified GC formation and anticollagen antibody production as the key pathogenic functions of B cells in CIA. The role of B cells in RA is likely to be more complex. However, targeting the GC reaction could allow for therapeutic interventions that are more refined than general B cell depletion.

Novel function of hydroxychloroquine: Down regulation of T follicular helper cells in collagen-induced arthritis

Hydroxychloroquine (HCQ) is an immunosuppressive agent widely used in rheumatoid arthritis (RA). T follicular helper (Tfh) cells play a vital role in the pathogenesis of RA. However, whether HCQ suppresses arthritis development through interfering with Tfh cells have never been reported. To address this issue, we investigated the percent of Tfh cells in newly diagnosed RA patients and found that they were up-regulated in peripheral blood. Importantly, in ex vivo experiments of peripheral blood mononuclear cells (PBMCs) from healthy volunteers, we proved that the percentage of Tfh cells in PBMCs and purified CD4+ T cells were decreased after HCQ treatment. In in vivo experiments of collagen-induced arthritis (CIA) model, we discovered that HCQ suppressed the incidence and score of arthritis, reduced the secretion of proinflammatory cytokines in serum. Similar to ex vivo study, the ratio of Tfh cells in HCQ treated CIA mice declined to the level of vehicle-treated group. Further research demonstrated that HCQ inhibited the generation of Tfh cells stimulated by IL-12 and IL-21. In conclusion, our study indicates a previously unrecognized mechanism of HCQ in RA, that HCQ directly suppresses the generation of Tfh cells by blocking IL-12 and IL-21 signaling pathways probably.

Periplocoside A ameliorated type II collagen-induced arthritis in mice via regulation of the balance of Th17/Treg cells

Periplocoside A (PSA) has been extracted from the Chinese herbal medicine Periploca sepium Bge to treat rheumatoid arthritis (RA) via immune regulation. We previously found that PSA exhibits immunosuppressive activity both in vitro and in vivo. Balanced regulation of helper T 17 (Th17)/regulatory T (Treg) cells is the current therapeutic direction for the treatment of RA. The present study investigated the mechanism of PSA in treating collagen-induced arthritis (CIA). The therapeutic effects and potential pharmacological mechanisms of PSA were specifically clarified by examining its effects on CIA in DBA/1 mice. PSA administration significantly relieved the severity of the arthritis, and preventive administration of PSA reduced the incidence of arthritis in the mice with CIA and relieved joint damage in terms of morphology. PSA was also able to reduce the levels of anti-collagen II (CII) antibodies and pro-inflammatory cytokines in the serum. As a result, the proportion of Th17 cells decreased, and the proportion of Treg cells increased. A follow-up study of the ex vivo immunological reactions induced by a specific antigen found that PSA suppressed lymphocyte proliferation, inhibited the differentiation and reactivity of Th17 cells, and promoted the proportion of Treg cells among helper T cells. PSA also exhibited pharmacological effect in regulating the balance between Th17 and Treg cells in CIA through relevant signalling pathways. Thus, PSA played a specific role in CIA treatment. In particular, our results suggest that the therapeutic effects of PSA on RA are partially realized via the regulation of the balance of Th17/Treg cells.

Neutrophil extracellular traps exacerbate Th1-mediated autoimmune responses in rheumatoid arthritis by promoting DC maturation.

Aberrant formation of neutrophil extracellular traps (NETs) is a key feature in rheumatoid arthritis (RA) and plays a pivotal role in disease pathogenesis. However, the mechanism through which NETs shape the autoimmune response in RA remains elusive. In this study, we demonstrate that inhibition of peptidylarginine deiminases activity in collagen-induced arthritis (CIA) mouse model significantly reduces NET formation, attenuates clinical disease activity, and prevents joint destruction. Importantly, peptidylarginine deiminase 4 blocking markedly reduces the frequency of collagen-specific IFN-γ-producing T helper 1 (Th1) cells in the draining lymph nodes of immunized mice. Exposure of dendritic cells (DCs) to CIA-derived NETs induces DC maturation characterized by significant upregulation of costimulatory molecules, as well as elevated secretion of IL-6. Moreover, CIA-NET-treated DCs promote the induction of antigen-specific Th1 cells in vitro. Finally, NETs from RA patients show an increased potential to induce the maturation of DCs from healthy individuals, corroborating the findings obtained in CIA mouse model. Collectively, our findings delineate an important role of NETs in the induction and expansion of Th1 pathogenic cells in CIA through maturation of DCs and reveal a novel role of NETs in shaping the RA-autoimmune response that could be exploited therapeutically.

Expression of tyrosine hydroxylase in CD4+ T cells contributes to alleviation of Th17/Treg imbalance in collagen-induced arthritis.

Tyrosine hydroxylase (TH), a rate-limiting enzyme for the synthesis of catecholamines, is expressed in T lymphocytes. However, the role of T cell-expressed TH in rheumatoid arthritis (RA) is less clear. Herein, we aimed to show the contribution of TH expression by CD4+ T cells to alleviation of helper T (Th)17/regulatory T (Treg) imbalance in collagen-induced arthritis (CIA), a mouse model of RA. CIA was prepared by intradermal injection of collagen type II (CII) at tail base of DBA1/J mice. Expression of TH in the spleen and the ankle joints was measured by real-time polymerase chain reaction and Western blot analysis. Percentages of TH-expressing Th17 and Treg cells in splenic CD4+ T cells were determined by flow cytometry. Overexpression and knockdown of TH gene in CD4+ T cells were taken to evaluate effects of TH on Th17 and Treg cells in CIA. TH expression was upregulated in both the inflamed tissues (spleen and ankle joints) and the CD4+ T cells of CIA mice. In splenic CD4+ T cells, the cells expressing TH were increased during CIA. These cells that expressed more TH in CIA were mainly Th17 cells rather than Treg cells. TH gene overexpression in CD4+ T cells from CIA mice reduced Th17 cell percentage as well as Th17-related transcription factor and cytokine expression and secretion, whereas TH gene knockdown enhanced the Th17 cell activity. In contrast, TH gene overexpression increased Treg-related cytokine expression and secretion in CD4+ T cells of CIA mice, while TH gene knockdown decreased the Treg cell changes. Collectively, these findings show that CIA induces TH expression in CD4+ T cells, particularly in Th17 cells, and suggest that the increased TH expression during CIA represents an anti-inflammatory mechanism.

Kinetic changes of regulatory B10 cells in collagen-induced arthritis could be regulated by cytokines IFN-γ and TGF-β1.

The status of B10 cells in patients with rheumatoid arthritis (RA) has not been consistently reported. In this study, we observed the kinetic changes of the B10 cells in collagen-induced arthritis (CIA) mice and the influence of multiple cytokines on the B10 cells to investigate the potential mechanism underlying the changes of B10 cells. The kinetic changes of frequency and function of the CD19(+)CD1d(hi)CD5(+) cells in splenic cells were observed during the complete progress of CIA mice. The kinetic changes of cytokines IL-4, IL-6, IL-17A, IL-18, TNF-α, IFN-γ and TGF-β1 were also detected. Then influence of these cytokines on the status of B10 cells was investigated both in vitro and in vivo. The frequency and suppressive ability of the CD19(+)CD1d(hi)CD5(+) cells increased to its peak on the 14th day while gradually decreased subsequently. IFN-γ showed a similar tendency with the CD19(+)CD1d(hi)CD5(+) cells, whereas IL-6, IL-17A, IL-18, TNF-α, and TGF-β1 reached its peak on the 28-35th day. In addition, IFN-γ up-regulated while TGF-β1 down-regulated the frequency and function of the CD19(+)CD1d(hi)CD5(+) cells both in vitro and in vivo. The B10 cells in CIA mice could be regulated by IFN-γ and TGF-β1, suggesting that the status of B10 cells in RA may be influenced by the balance of pro-inflammatory and anti-inflammatory factors, and the impaired B10 cells could be recovered in vitro by adequate treatment before being used for a therapeutic method in clinical practice.

Modulating effects of leflunomide on the balance of Th17/Treg cells in collageninduced arthritis DBA/1 mice.

To evaluated the effect and mechanism of leflunomide (LEF) in murine model of collage-induced arthritis (CIA) on modulating the balance of Th17/Treg cells. DBA mice were divided into: control, CIA, CIA + LEF and CIA + Ibuprofen group. After 14 days immunization with bovine type II collagen (CII), except control group, mice were orally administered saline (CIA group), LEF or ibuprofen daily for 14 days. The severity of arthritis joint was assessed by using arthritis score. The numbers of CD3 + CD4 + interleukin 17 (IL-17) + Th17 cells and CD4 + CD25 + Foxp3+ Tregs were determined by flow cytometry, the expression of ROR-γt, Foxp3 and IL-21 mRNA in spleen were quantified by RT-PCR and IL-17, IL-21 and transforming growth factor β (TGF-β) level in serum was measured by ELISA.In comparison with CIA group, CIA + LEF and CIA + Ibuprofen group reduced the disease severity obviously (p < 0.05). Leflunomide reduced Th17 cells, the expression of ROR-γt and IL-21 mRNA (p < 0.05) and the levels of IL-17 and IL-21 in serum. In addition, Ibuprofen but not LEF has effect on Treg cells number, Foxp3 mRNA expression and TGF-β secretion.These results indicate that LEF effect on the balance od Th17/Treg through suppressing Th17 cells, but not stimulating Treg cells. Leflunomide may act as a potential immunomodulator for the treatment of rheumatoid arthritis (RA).

In vivo action of IL-27: reciprocal regulation of Th17 and Treg cells in collagen-induced arthritis

Interleukin (IL)-27 is a novel cytokine of the IL-6/IL-12 family that has been reported to be involved in the pathogenesis of autoimmune diseases and has a pivotal role as both a pro- and anti-inflammatory cytokine. We investigated the in vivo effects of IL-27 on arthritis severity in a murine collagen-induced arthritis (CIA) model and its mechanism of action regarding control of regulatory T (Tregs) and IL-17-producing T helper 17 (Th17) cells. IL-27-Fc-treated CIA mice showed a lower severity of arthritis. IL-17 expression in the spleens was significantly decreased in IL-27-Fc-treated CIA mice compared with that in the CIA model. The Th17 population was decreased in the spleens of IL-27-Fc-treated CIA mice, whereas the CD4+CD25+Foxp3+ Treg population increased. In vitro studies revealed that IL-27 inhibited IL-17 production in murine CD4+ T cells, and the effect was associated with retinoic acid-related orphan receptor γT and signal transducer and activator of transcription 3 inhibition. In contrast, fluorescein isothiocyanate-labeled forkhead box P3 (Foxp3) and IL-10 were profoundly augmented by IL-27 treatment. Regarding the suppressive capacity of Treg cells, the proportions of CTLA-4+ (cytotoxic T-lymphocyte antigen 4), PD-1+ (programmed cell death protein 1) and GITR+ (glucocorticoid-induced tumor necrosis factor receptor) Tregs increased in the spleens of IL-27-Fc-treated CIA mice. Furthermore, in vitro differentiated Treg cells with IL-27 exerted a more suppressive capacity on T-cell proliferation. We found that IL-27 acts as a reciprocal regulator of the Th17 and Treg populations in CD4+ cells isolated from healthy human peripheral blood mononuclear cells (PBMCs), as well as from humans with rheumatoid arthritis (RA) PBMCs. Our study suggests that IL-27 has the potential to ameliorate overwhelming inflammation in patients with RA through a reciprocal regulation of Th17 and Treg cells.

Expansion of a marginal zone B cell-like population in lymph nodes of mice developing collagen-induced arthritis (P4042)

Abstract The importance of B cells in collagen-induced arthritis led us to investigate whether particular B cell subsets participate in the autoimmune response to collagen type II. We show here that MZB cells in the spleen are naturally self-reactive to collagen type II and are the first cells to expand after collagen type II immunization. In contrast, the autoimmune collagen type II response in lymph nodes develops one week later. Due to this time lapse we hypothesized that the MZB cells may be involved in initiating the autoimmune response in the lymph nodes. We did indeed find a small MZB-like B cell population in the lymph nodes that expressed B220+CD23loCD1dhi, thereby being distinguishable from FOB cells. The MZB-like cells expanded almost two-fold after immunization with collagen type II but not the control antigen ovalbumin, making this phenomenon specific to the autoimmune response. The MZB-like cells displayed an antigen activated phenotype with increased cell surface expression of MHCII, FcγRIIb and CD70. Moreover, after immunization the MZB-like cells increased their expression of CXCR5, implying that they are migrating cells. Further investigation of the specific function of the MZB-like cells is warranted. In conclusion, MZB cells in the spleen trigger the autoimmune collagen type II response in collagen-induced arthritis, and a MZB-like population in the lymph nodes is specific for the autoimmune reaction and may be of importance for disease pathogenesis in this model.

CORRIGENDUM

Invariant natural killer T (iNKT) cells play a protective role in the development of certain autoimmune diseases. However, their precise role in the pathogenesis of autoimmune arthritis remains unclear. In this study, we examined the possible contribution of iNKT cells in collagen-induced arthritis (CIA) by using iNKT cell-deficient mice (Jalpha281-/- mice). CIA in these mice was markedly suppressed and interleukin (IL)-17 production was reduced in a native type II collagen (CII)-specific T cell response. Draining lymph nodes of CII-immunized Jalpha281-/- mice contained a significantly low number of IL-17-producing T helper cells. To determine whether iNKT cells produce IL-17, we measured IL-17 by enzyme-linked immunosorbent assay in iNKT cells stimulated with the ligand, alpha-galactosylceramide (alpha-GalCer). Notably, splenocytes from Jalpha281-/- mice stimulated in this way were negative for IL-17, whereas those from C57BL/6 mice produced IL-17. Immunostaining for IL-17 in iNKT cells confirmed intracellular staining of the protein. RT-PCR analysis showed that iNKT cells expressed retinoid-related orphan receptor gammaT and IL-23 receptor. Moreover, cell sorting demonstrated that NK1.1- iNKT cells were the main producers of IL-17 compared with NK1.1+ iNKT cells. IL-17 production by iNKT cells was induced by IL-23-dependent and -independent pathways, since iNKT produced IL-17 when stimulated with either IL-23 or alpha-GalCer alone. Our findings indicate that iNKT cells are producers and activators of IL-17 via IL-23- dependent and -independent pathways, suggesting that they are key cells in the pathogenesis of CIA through IL-17.

A Citrullinated Fibrinogen-Specific T Cell Line Enhances Autoimmune Arthritis in a Mouse Model of Rheumatoid Arthritis

Citrullinated proteins, derived from the conversion of peptidyl-arginine to peptidyl-citrulline, are present in the joints of patients with rheumatoid arthritis (RA), who also uniquely produce high levels of anti-citrullinated protein Abs. Citrullinated fibrinogen (CF) is abundant in rheumatoid synovial tissue, and anti-citrullinated protein Ab-positive RA patients exhibit circulating immune complexes containing CF. Thus, CF is a potential major target of pathogenic autoimmunity in RA. T cells are believed to be involved in this process by initiating, controlling, and driving Ag-specific immune responses in RA. In this study, we isolated a CD4 T cell line specific for CF that produces inflammatory cytokines. When transferred into mice with collagen-induced arthritis (CIA), this T cell line specifically enhanced the severity of autoimmune arthritis. Additionally, pathogenic IgG2a autoantibody levels to mouse type II collagen were increased in mice that received the T cells in CIA, and levels of these T cells were increased in the synovium, suggesting the T cells may have had systemic effects on the B cell response as well as local effects on the inflammatory environment. This work demonstrates that CD4 T cells specific for CF can amplify disease severity after onset of CIA.

Enforced Expression of Roquin Protein in T Cells Exacerbates the Incidence and Severity of Experimental Arthritis

To investigate the role of Roquin, a RING-type ubiquitin ligase family member, we used transgenic mice with enforced Roquin expression in T cells, with collagen-induced arthritis (CIA). Wild-type (WT) and Roquin transgenic (Tg) mice were immunized with bovine type II collagen (CII). Arthritis severity was evaluated by clinical score; histopathologic CIA severity; proinflammatory and anti-inflammatory cytokine levels; anti-CII antibody levels; and populations of Th1, Th2, germinal center B cells, and follicular helper T cells in CIA. T cell proliferation in vitro and cytokine levels were determined to assess the response to CII. Roquin Tg mice developed more severe CIA and joint destruction compared with WT mice. Production of TNF-α, IFN-γ, IL-6, and pathogenic anti-collagen CII-specific IgG and IgG2a antibodies was increased in Roquin Tg mice. In addition, in vitro T cell assays showed increased proliferation and proinflammatory cytokine production in response to CII as a result of enforced Roquin expression in T cells. Furthermore, the Th1/Th2 balance was altered by an increased Th1 and decreased Th2 population. These findings suggest that overexpression of Roquin exacerbates the development of CIA and that enforced expression of Roquin in T cells may promote autoimmune diseases such as CIA.

IL-32 aggravates synovial inflammation and bone destruction and increases synovial natural killer cells in experimental arthritis models

This study was performed to investigate the effects of IL-32 on joint inflammation, bone destruction, and synovial cytokine expressions, and on synovial natural killer (NK) cell expressions in collagen-induced arthritis (CIA). CIA was induced by type II collagen in DBA1 mice, and phosphate-buffered saline (PBS group) or IL-32 (IL-32 group) were injected into both knee joints at day 28 and 32, then mice were killed at day 35. Severity of synovial inflammation and bone destruction was determined by histological scoring method, and synovial cytokine expressions such as IL-1β, TNF-α, IL-17, IL-18, IFN-γ, IL-21, and IL-23 were measured by real-time RT-PCR and western blot. Synovial NK cell expressions were determined by real-time RT-PCR, western blot and immunohistochemistry, and chemokines and chemokine receptors expressions that are associated with NK cell migration were determined by real-time RT-PCR. Scores of synovial inflammation and bone destruction, synovial expressions of IL-1β, TNF-α, IL-18, and IFN-γ were significantly increased in IL-32 group compared with PBS group. Synovial expressions of NK cell, and chemokines (CCL2 and CXCL9) and chemokine receptors (CCR2 and CCR5) that are associated with NK cell migration were significantly increased in IL-32 group compared with PBS group. IL-32 aggravated joint inflammation and bone destruction and increased synovial expressions of inflammatory cytokine and NK cells in CIA. These results suggest that IL-32 play a role in joint inflammation and bone destruction, and IL-32 might be a new target for treatment of rheumatoid arthritis.

Characterization of inhibitory T cells induced by an analog of type II collagen in an HLA-DR1 humanized mouse model of autoimmune arthritis

IntroductionWe used DR1 transgenic mice and covalently linked DR1 multimers to characterize analog-specific inhibitory T cells in collagen-induced arthritis (CIA). Because of the low numbers of antigen-specific T cells in wild-type mice, functional T-cell studies in autoimmune arthritis have been challenging. The use of T-cell receptor (TCR) transgenic mice has provided useful information, but such T cells may not represent the heterogeneous T-cell response that occurs in natural settings. Our focus was to develop tools to identify and characterize the population of immunoregulatory T cells induced in wild-type mice by an analog peptide of CII259-273, which contains amino acid substitutions at positions 263 (N) and 266 (D) (analog peptide A12).MethodsDR1 multimers, developed by loading empty class II molecules with exogenous peptide, provide a method for visualizing antigen-specific T cells with flow cytometry. However, the low binding avidity of A12 for the major histocompatibility complex (MHC) made this strategy untenable. To overcome this problem, we generated DR1 multimers in which the analog peptide A12 was covalently linked, hoping that the low-avidity analog would occupy enough binding clefts to allow detection of the responsive T cells.ResultsStaining with the tetramer revealed that A12-specific T cells were readily detectable at 10 days after immunization. These CD4(+) T cells are a highly selective subset of the TCR repertoire and have a limited clonality. Analysis of cytokine expression showed that cells detected by tetramer (A12) expressed primarily suppressive cytokines (interleukin-4 (IL-4) and IL-10) in response to collagen, compared with control cells. Although they did not express Fox-p3, they were extremely effective in preventing and suppressing inflammatory arthritis.ConclusionsIn summary, our studies showed that the use of covalently linked multimers allows characterization of analog-specific T cells that are otherwise difficult to detect. The suppressive character of the analog-specific T-cell response suggests that these cells attenuate autoimmunity and differ significantly in phenotype from the inflammatory T cells predominantly found in arthritic joints. Such reagents will become powerful tools to study T-cell responses in RA patients in upcoming clinical trials.