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Although rheumatoid arthritis has been known to be a common autoimmune disease characterized by chronic inflammation mainly evident in diarthrodial joints, its pathogenesis remains to be clarified. In the present study, to investigate the pathogenic signaling system taken place in the rheumatoid joints, we assessed whether synovial fluid obtained from patients with rheumatoid arthritis contains inducers for proinflammatory cytokines such as interleukin (IL)-12 and IL-23. Peritoneal macrophages isolated from IL-12/IL-23 p40-YFP reporter mice were stimulated with synovial fluid, followed by flow cytometry to screen CD11b+ and YFP-expressing cells, reflective of IL-12/IL-23 p40-producing macrophages. The expression levels of Toll-like receptor (TLR)-2 and -4, which have a potential to mediate IL-12/IL- 23 p40 induction, were determined in synovial cells obtained from a patient with rheumatoid arthritis by RT-PCR analyses. One out of 10 synovial fluid from rheumatoid arthritis patients induced IL-12/IL-23 p40 expression, while all of 10 synovial fluid from osteoarthritis patients did not. Synoviocytes constitutively expressed Toll-like receptor (TLR)-2 and -4 which are candidate receptors for IL-12/IL-23 inducers. Upon LPS stimulation, the levels of TLR-2 and -4 were downregulated and upregulated, respectively. Taken together, these results suggest that some patients with rheumatoid arthritis elicit synovitis through TLR-2- and -4-mediated induction of proinflammatory cytokines IL-12 and IL-23.
Animals ; Arthritis, Rheumatoid ; Autoimmune Diseases ; Cytokines ; Flow Cytometry ; Fluorescence* ; Humans ; Inflammation ; Interleukin-12 ; Interleukin-23 ; Interleukins ; Joints ; Macrophages ; Macrophages, Peritoneal ; Mass Screening* ; Mice* ; Osteoarthritis ; Synovial Fluid* ; Synovitis ; Toll-Like Receptors

BACKGROUND: To determine the molecular structure of type II collagen-specific T-cell receptors associated with rheumatoid arthritis (RA). METHODS: We generated CII-specific T-cell lines of 8 RA patient s by prolonged in vitro culture with bovine CII (bCII) and the immunogenic peptide (256-270) of human CII. The proliferation response towards CII stimulation was measured from the uptake of 3 H-thymidine. Changes in the secretion of Th 1 and Th2 cytokines in the culture supernatent were measured by ELISA. The TCR clonotypes of these T-cells were examined by RT-PCR/ SSCP analyses of all 22 V beta chains. RESULTS: T-cells from patients' tissue exhibited strong proliferation index upon CII stimulation, which was maintained up to 6 months in the culture. The secretion of INF-gamma from these T-cells increased along with the duration of culture time, while the amount of IL-4 production did not show significant changes. The SSCP band patterns of patients' T-cells appear as discrete bands unlike the smeary streak produced from normal samples. Some SSCP bands, each representing selected expansion of a TCR containing certain subtype of V beta peptides, appeared to be identical in more than one patients. Among these, the expansion of SSCP band representing the V beta 14 CDR3 region persisted after switching the antigen to the immunogenic human peptide (256-270). CONCLUSION: CII-reactive T-cells expressing distinct CDR3 motifs are selectively expanded in the peripheral blood and synovial fluid of RA patients, and their persistent proliferation upon CII stimulation, as well as the production Th 1-type cytokines, may play pivotal roles in RA pathogenesis.
Arthritis, Rheumatoid* ; Cytokines ; Enzyme-Linked Immunosorbent Assay ; Humans ; Interleukin-4 ; Molecular Structure ; Peptides ; Polymorphism, Single-Stranded Conformational ; Receptors, Antigen, T-Cell ; Synovial Fluid ; T-Lymphocytes*

Indoleamine 2,3-dioxygenase (IDO) is a key negative regulator of immune responses and has been implicated in tumor tolerance, autoimmune disease and asthma. IDO was detected in the joint synovial tissue in the inflammatory microenvironment of rheumatoid arthritis (RA), but IDO expression in joint synovial tissue is not sufficient to overcome the inflamed synovial environment. This study aimed to unravel the mechanisms involving the failure to activate tolerogenic IDO in the inflamed joint. We demonstrate that both poly (I:C) and lipopolysaccharide (LPS) induce expression of IDO in synovial fibroblasts. However, inflammatory cytokines such as IL-17, TNF-alpha, IL-12, IL-23 and IL-16 did not induce IDO expression. Poly (I:C) appeared to induce higher IDO expression than did LPS. Surprisingly, toll-like receptor (TLR)4-mediated IDO expression was upregulated after depletion of myeloid differentiation primary response protein 88 (MyD88) in synovial fibroblasts using small interfering RNA (siRNA). IDO, TLR3 and TLR4 were highly expressed in synovial tissue of RA patients compared with that of osteoarthritis patients. In addition, RA patients with severe disease activity had higher levels of expression of IDO, TLR3 and TLR4 in the synovium than patients with mild disease activity. These data suggest that upregulation of IDO expression in synovial fibroblasts involves TLR3 and TLR4 activation by microbial constituents. We showed that the mechanisms responsible for IDO regulation primarily involve MyD88 signaling in synovial fibroblasts, as demonstrated by siRNA-mediated knockdown of MyD88.
Adaptor Proteins, Vesicular Transport/genetics/metabolism ; Arthritis, Rheumatoid/*metabolism ; Blotting, Western ; Cells, Cultured ; Fibroblasts/drug effects/*metabolism ; Humans ; Immunohistochemistry ; Indoleamine-Pyrrole 2,3,-Dioxygenase/genetics/*metabolism ; Interleukin-12/pharmacology ; Interleukin-16/pharmacology ; Interleukin-17/pharmacology ; Interleukin-23/pharmacology ; Lipopolysaccharides/pharmacology ; Myeloid Differentiation Factor 88/genetics/*metabolism ; Poly I-C/pharmacology ; Polymerase Chain Reaction ; RNA, Small Interfering/genetics/physiology ; Synovial Membrane/*cytology ; Toll-Like Receptor 4/genetics/metabolism ; Tumor Necrosis Factor-alpha/pharmacology

Myeloid-related protein (MRP)8/MRP14 is an endogenous Toll-like receptor 4 (TLR4) ligand and is abundant in synovial fluid (SF) of rheumatoid arthritis (RA) patients. Belonging to damage-associated molecular patterns, it amplifies proinflammatory mediators and facilitates a wide range of inflammatory and autoimmune diseases. Interleukin (IL)-17-producing T-helper (Th)17 cells have a crucial role in RA pathogenesis, and IL-6 is the key factor promoting Th17 differentiation. We investigated whether the level of MRP8/MRP14 is positively associated with IL-6 and IL-17 levels in RA SF and found that MRP8/MRP14 level had a significant correlation with IL-6 and IL-17 levels in RA SF. We also observed that MRP8-induced IL-17 production by peripheral blood mononuclear cells but MRP14 did not. Upon stimulation with MRP8, IL-6 production was enhanced by RA fibroblast-like synoviocytes (FLS) and was further elevated by coculturing RA FLS with activated CD4+ T cells. Moreover, we demonstrated that MRP8-activated IL-6 production by RA FLS promoted differentiation of Th17 cells using the coculture system consisting of CD4+ T cells and RA FLS. In addition, IL-6 blockade attenuated Th17 polarization of CD4+ T cells in the cocultures. Inhibitor studies revealed that MRP8 increased IL-6 production in RA FLS via TLR4/phosphoinositide 3-kinase/nuclear factor-kappaB and mitogen-activated protein kinase signaling pathways. Our results show that MRP8 has a crucial role in stimulating IL-6 expression by RA FLS, and subsequently promotes Th17 differentiation in RA, suggesting that neutralizing MRP8 level in RA synovium may be an effective therapeutic strategy in RA treatment.
ATP-Binding Cassette Transporters/*metabolism ; Adult ; Aged ; Arthritis, Rheumatoid/*pathology ; CD4-Positive T-Lymphocytes/metabolism ; Calgranulin B/metabolism ; Cell Differentiation/*immunology ; Fibroblasts/*metabolism/pathology ; Humans ; Inflammation Mediators/metabolism ; Interleukin-17/metabolism ; Interleukin-6/*biosynthesis ; Middle Aged ; Signal Transduction/immunology ; Synovial Fluid/cytology ; Synovial Membrane/metabolism/pathology ; Th17 Cells/*pathology ; Toll-Like Receptor 4/metabolism ; *Up-Regulation

BACKGROUND: CD4+Fop3+ regulatory T cells (Tregs) are needed to maintain peripheral tolerance, but their role in the development of autoimmune arthritis is still debated. The present study was undertaken to investigate the mechanism by which Tregs influence autoimmune arthritis, using a mouse model entitled K/BxN. METHODS: We generated Treg-deficient K/BxNsf mice by congenically crossing K/BxN mice with Foxp3 mutant scurfy mice. The arthritic symptoms of the mice were clinically and histopathologically examined. The proportions and activation of CD4+ T cells and/or dendritic cells were assessed in the spleens, draining lymph nodes and synovial tissue of these mice. RESULTS: K/BxNsf mice exhibited earlier onset and more aggressive progression of arthritis than their K/BxN littermates. In particular, bone destruction associated with the influx of numerous RANKL+ cells into synovia was very prominent. They also contained more memory phenotype CD4+ T cells, more Th1 and Th2 cells, and fewer Th17 cells than their control counterparts. Plasmacytoid dendritic cells expressing high levels of CD86 and CD40 were elevated in the K/BxNsf synovia. CONCLUSION: We conclude that Tregs oppose the progression of arthritis by inhibiting the development of RANKL+ cells, homeostatically proliferating CD4+ T cells, Th1, Th2 and mature plasmacytoid dendritic cells, and by inhibiting their influx into joints.
Animals ; Arthritis ; Dendritic Cells ; Joints ; Lymph Nodes ; Memory ; Mice ; Peripheral Tolerance ; Phenotype ; Spleen ; Synovial Fluid ; Synovial Membrane ; T-Lymphocytes ; T-Lymphocytes, Regulatory ; Th17 Cells ; Th2 Cells

BACKGROUND: CD4+Fop3+ regulatory T cells (Tregs) are needed to maintain peripheral tolerance, but their role in the development of autoimmune arthritis is still debated. The present study was undertaken to investigate the mechanism by which Tregs influence autoimmune arthritis, using a mouse model entitled K/BxN. METHODS: We generated Treg-deficient K/BxNsf mice by congenically crossing K/BxN mice with Foxp3 mutant scurfy mice. The arthritic symptoms of the mice were clinically and histopathologically examined. The proportions and activation of CD4+ T cells and/or dendritic cells were assessed in the spleens, draining lymph nodes and synovial tissue of these mice. RESULTS: K/BxNsf mice exhibited earlier onset and more aggressive progression of arthritis than their K/BxN littermates. In particular, bone destruction associated with the influx of numerous RANKL+ cells into synovia was very prominent. They also contained more memory phenotype CD4+ T cells, more Th1 and Th2 cells, and fewer Th17 cells than their control counterparts. Plasmacytoid dendritic cells expressing high levels of CD86 and CD40 were elevated in the K/BxNsf synovia. CONCLUSION: We conclude that Tregs oppose the progression of arthritis by inhibiting the development of RANKL+ cells, homeostatically proliferating CD4+ T cells, Th1, Th2 and mature plasmacytoid dendritic cells, and by inhibiting their influx into joints.
Animals ; Arthritis ; Dendritic Cells ; Joints ; Lymph Nodes ; Memory ; Mice ; Peripheral Tolerance ; Phenotype ; Spleen ; Synovial Fluid ; Synovial Membrane ; T-Lymphocytes ; T-Lymphocytes, Regulatory ; Th17 Cells ; Th2 Cells

Transplantation research has focused on cytotoxic T-cell and plasma cell/B-cell-targeted strategies, but little attention has been paid to the role of T helper 17 (Th17) cells in allograft dysfunction. However, accumulating evidence suggests that Th17 cells contribute to the development of acute and chronic allograft injury after transplantation of various organs, including the kidney. This review summarizes recent reports on the role of Th17 cells in kidney transplantation. Means of improving allograft outcomes by targeting the Th17 pathway are also suggested.
Allografts ; Kidney Transplantation* ; Kidney* ; Plasma ; T-Lymphocytes ; Th17 Cells*

Sjögren syndrome (SS) is a chronic autoimmune disorder that primarily targets the salivary and lacrimal glands. The pathology of these exocrine glands is characterized by periductal focal lymphocytic infiltrates, and both T cell-mediated tissue injury and autoantibodies that interfere with the secretion process underlie glandular hypofunction. In addition to these adaptive mechanisms, multiple innate immune pathways are dysregulated, particularly in the salivary gland epithelium. Our understanding of the pathogenetic mechanisms of SS has substantially improved during the past decade. In contrast to viral infection, bacterial infection has never been considered in the pathogenesis of SS. In this review, oral dysbiosis associated with SS and evidence for bacterial infection of the salivary glands in SS were reviewed. In addition, the potential contributions of bacterial infection to innate activation of ductal epithelial cells, plasmacytoid dendritic cells, and B cells and to the breach of tolerance via bystander activation of autoreactive T cells and molecular mimicry were discussed. The added roles of bacteria may extend our understanding of the pathogenetic mechanisms and therapeutic approaches for this autoimmune exocrinopathy.

OBJECTIVE: Rheumatoid arthritis (RA) is a chronic autoimmune disease. Macrophage migration inhibitory factor (MIF) has been shown to be an important pro-inflammatory cytokine in RA. The aim of this study was to determine if the engagement of toll-like receptor 3 (TLR3) induces the production of MIF in the fibroblast-like synoviocytes (FLS) of patients with RA. METHODS: The expression of inflammatory cytokines (e.g. MIF, IL-6, IL-1beta and TNFalpha) and toll-like receptors (e.g. TLR2, TLR3 and TLR4) in the synovial tissue were quantified by immunohistochemistry. FLS were isolated from the synovial tissues of patients with RA and stimulated with TLR-3 ligand polyI:C, in the presence of a neutralizing antibody against IL-6. The concentrations of MIF and IL-6 in the culture supernatants from the FLS were measured using sandwich ELISA. RESULTS: The engagement of TLR3 with PolyI:C increased the production of MIF in FLS. The stimulatory effect of these TLR ligands showed a dose-dependent trend. The combination of TLR3 and TLR4 synergistically increased the level of MIF and IL-6 production. The addition of neutralizing antibodies against IL-6 abrogated the stimulatory effect of the ligands of TLR3 and TLR4 on the production of MIF. CONCLUSION: These results show that TLR3 engagement stimulates the production of MIF and IL-6. Therefore, the TLRs help perpetuate of RA pathogenesis through production of MIF from the FLS in patients with RA, and might provide a new therapeutic approach for the treatment of rheumatoid arthritis.
Antibodies, Neutralizing ; Arthritis, Rheumatoid ; Autoimmune Diseases ; Cytokines ; Enzyme-Linked Immunosorbent Assay ; Humans ; Immunohistochemistry ; Interleukin-6 ; Ligands ; Macrophages ; Toll-Like Receptor 3 ; Toll-Like Receptors ; Up-Regulation