Interleukin-7 deficiency in rheumatoid arthritis

Interleukin-7 (IL-7) is a stromal factor that is crucial for the development of T lymphocytes in humans and mice, and also B lymphocytes in mice. IL-7 can act as a T cell growth factor as well as a critical anti-apoptotic survival factor. The essential non-redundant role of this cytokine for T cell development in vivo is indicated by the phenotype of murine knockout models as well as by humans with a T^-B⁺NK⁺ form of severe combined immunodeficiency (SCID) resulting from mutations in IL-7 receptor α chain. IL-7 deficiency has now been found in patients with rheumatoid arthritis, a finding that relates not only to the T-lymphocyte status in this disease but also to the ability of patients with rheumatoid arthritis to recover from therapy-induced lymphopenia.     

Suppression of proteoglycan-induced arthritis by anti-CD20 B Cell depletion therapy is mediated by reduction in autoantibodies and CD4+ T cell reactivity

B cells have been implicated in the pathogenesis of rheumatoid arthritis (RA) since the discovery of RA as an autoimmune disease. There is renewed interest in B cells in RA based on the clinical efficacy of B cell depletion therapy in RA patients. Although, reduced titers of rheumatoid factor and anti-cyclic citrullinated peptide Abs are recorded, the mechanisms that convey clinical improvement are incompletely understood. In the proteoglycan-induced arthritis (PGIA) mouse model of RA, we reported that Ag-specific B cells have two important functions in the development of arthritis. PG-specific B cells are required as autoantibody-producing cells as well as Ag-specific APCs. Herein we report on the effects of anti-CD20 mAb B cell depletion therapy in PGIA. Mice were sensitized to PG and treated with anti-CD20 Ab at a time when PG-specific autoantibodies and T cell activation were evident but before acute arthritis. In mice treated with anti-CD20 mAb, development of arthritis was significantly reduced in comparison to control mAb-treated mice. B cell depletion reduced the PG-specific autoantibody response. Furthermore, there was a significant reduction in the PG-specific CD4(+) T cell recall response as well as significantly fewer PG-specific CD4(+) T cells producing IFN-gamma and IL-17, but not IL-4. The reduction in PG-specific T cells was confirmed by the inability of CD4(+) T cells from B cell-depleted mice to adoptively transfer disease into SCID mice. Overall, B cell depletion during PGIA significantly reduced disease and inhibited both autoreactive B cell and T cell function.     

The molecular mechanism of osteoclastogenesis in rheumatoid arthritis

Bone-resorbing osteoclasts are formed from hemopoietic cells of the monocyte–macrophage lineage under the control of bone-forming osteoblasts. We have cloned an osteoblast-derived factor essential for osteoclastogenesis, the receptor activator of NF-κB ligand (RANKL). Synovial fibroblasts and activated T lymphocytes from patients with rheumatoid arthritis also express RANKL, which appears to trigger bone destruction in rheumatoid arthritis as well. Recent studies have shown that T lymphocytes produce cytokines other than RANKL such as IL-17, granulocyte–macrophage colony-stimulating factor and IFN-γ, which have powerful regulatory effects on osteoclastogenesis. The possible roles of RANKL and other cytokines produced by T lymphocytes in bone destruction are described.     

IL-17 plays an important role in the development of experimental autoimmune encephalomyelitis

IL-17 is a proinflammatory cytokine that activates T cells and other immune cells to produce a variety of cytokines, chemokines, and cell adhesion molecules. This cytokine is augmented in the sera and/or tissues of patients with contact dermatitis, asthma, and rheumatoid arthritis. We previously demonstrated that IL-17 is involved in the development of autoimmune arthritis and contact, delayed, and airway hypersensitivity in mice. As the expression of IL-17 is also augmented in multiple sclerosis, we examined the involvement of this cytokine in these diseases using IL-17(-/-) murine disease models. We found that the development of experimental autoimmune encephalomyelitis (EAE), the rodent model of multiple sclerosis, was significantly suppressed in IL-17(-/-) mice; these animals exhibited delayed onset, reduced maximum severity scores, ameliorated histological changes, and early recovery. T cell sensitization against myelin oligodendrocyte glycoprotein was reduced in IL-17(-/-) mice upon sensitization. The major producer of IL-17 upon treatment with myelin digodendrocyte glycopritein was CD4+ T cells rather than CD8+ T cells, and adoptive transfer of IL-17(-/-) CD4+ T cells inefficiently induced EAE in recipient mice. Notably, IL-17-producing T cells were increased in IFN-gamma(-/-) cells, while IFN-gamma-producing cells were increased in IL-17(-/-) cells, suggesting that IL-17 and IFN-gamma mutually regulate IFN-gamma and IL-17 production. These observations indicate that IL-17 rather than IFN-gamma plays a crucial role in the development of EAE.     

IL-7R alpha gene expression is inversely correlated with cell cycle progression in IL-7-stimulated T lymphocytes

IL-7 plays a major role in T lymphocyte homeostasis and has been proposed as an immune adjuvant for lymphopenic patients. This prospect is based, at least in part, on the short-term expansion of peripheral T cells in rIL7-treated mice and primates. Nevertheless, in vivo, following initial increases in T cell proliferation and numbers, lymphocytes return to a quiescent state. As the bases for this cell cycle exit have not yet been elucidated, it is important to assess the long-term biological effects of IL-7 on quiescent human T lymphocyte subsets. In this study, we find that IL-7-stimulated CD4+ naive lymphocytes enter into cell cycle with significantly delayed kinetics as compared with the memory population. Importantly though, these lymphocytes exit from the cell cycle despite the continuous replenishment of rIL-7. This response is distinct in memory and naive CD4+ lymphocytes with memory cells starting to exit from cycle by day 10 vs day 18 for naive cells. Return to quiescence is associated with a cessation in IL-7R signaling as demonstrated by an abrogation of STAT-5 phosphorylation, despite an up-regulation of surface IL-7Ralpha. Indeed, an initial 10-fold decrease in IL-7Ralpha mRNA levels is followed by increased IL-7Ralpha expression in naive as well as memory T cells, with kinetics paralleling cell cycle exit. Altogether, our data demonstrate that IL-7 promotes the extended survival of both naive and memory CD4+ T cells, whereas cycling of these two subsets is distinct and transient. Thus, IL-7 therapy should be designed to allow optimal responsiveness of naive and memory T cell subsets.     

Intrinsic tolerance in autologous collagen-induced arthritis is generated by CD152-dependent CD4+ suppressor cells

Collagen-induced arthritis is a mouse model of rheumatoid arthritis (RA) and is commonly induced after immunization with type II collagen (CII) of a non-mouse origin. T cell recognition of heterologous CII epitopes has been shown to be critical in development of arthritis, as mice with cartilage-restricted transgenic expression of the heterologous T cell epitope (MMC mice) are partially tolerized to CII. However, the mechanism responsible for tolerance and arthritis resistance in these mice is unclear. The present study investigated the regulatory mechanisms in naturally occurring self-tolerance in MMC mice. We found that expression of heterologous rat CII sequence in the cartilage of mice positively selects autoreactive CD4(+) T cells with suppressive capacity. Although CD4(+)CD25(+) cells did not play a prominent role in this suppression, CD152-expressing T cells played a crucial role in this tolerance. MMC CD4(+) T cells were able to suppress proliferation of wild-type cells in vitro where this suppression required cell-to-cell contact. The suppressive capability of MMC cells was also demonstrated in vivo, as transfer of such cells into wild-type arthritis susceptible mice delayed arthritis onset. This study also determined that both tolerance and disease resistance were CD152-dependent as demonstrated by Ab treatment experiments. These findings could have relevance for RA because the transgenic mice used express the same CII epitope in cartilage as humans and because autoreactive T cells, specific for this epitope, are present in transgenic mice as well as in patients with RA.     

Induction of IL-10-producing CD4+CD25+ T cells in animal model of collagen-induced arthritis by oral administration of type II collagen

Induction of oral tolerance has long been considered a promising approach to the treatment of chronic autoimmune diseases, including rheumatoid arthritis (RA). Oral administration of type II collagen (CII) has been proven to improve signs and symptoms in RA patients without troublesome toxicity. To investigate the mechanism of immune suppression mediated by orally administered antigen, we examined changes in serum IgG subtypes and T-cell proliferative responses to CII, and generation of IL-10-producing CD4+CD25+ T-cell subsets in an animal model of collagen-induced arthritis (CIA). We found that joint inflammation in CIA mice peaked at 5 weeks after primary immunization with CII, which was significantly less in mice tolerized by repeated oral feeding of CII before CIA induction. Mice that had been fed with CII also exhibited increased serum IgG1 and decreased serum IgG2a as compared with nontolerized CIA animals. The T-cell proliferative response to CII was suppressed in lymph nodes of tolerized mice also. Production of IL-10 and of transforming growth factor-beta from mononuclear lymphocytes was increased in the tolerized animals, and CD4+ T cells isolated from tolerized mice did not respond with induction of IFN-gamma when stimulated in vitro with CII. We also observed greater induction of IL-10-producing CD4+CD25+ subsets among CII-stimulated splenic T cells from tolerized mice. These data suggest that when these IL-10-producing CD4+CD25+ T cells encounter CII antigen in affected joints they become activated to exert an anti-inflammatory effect.     

靶定IL-17 治疗类风湿关节炎研究进展

IL-17作为前炎症因子参与类风湿关节炎,系统性红斑狼疮等自身免疫性疾病的病理过程。它主要由CD4+T细胞的一个亚群--Th17细胞分泌释放。目前,IL-17在类风湿关节炎的病理过程中的作用引起了医学界广泛的关注,抗IL-17A抗体已经生产并进入临床实验,用于治疗类风湿关节炎、银屑病关节炎等疾病。但其在类风湿关节炎病理过程中的作用尚需进一步研究,其有效性亦尚需进一步探讨。本文主要针对IL-17家族的各个亚型的表达、调控、生物学作用及与类风湿关节炎发病的关系进行阐述,为类风湿关节炎的治疗提供新的思路。     

Isolation and characteristics of autoreactive T cells specific to aggrecan G1 domain from rheumatoid arthritis patients

NTRODUCTIONRheumatoid arthritis (RA) is a common disease characterized by the chroniclesion of polyarthritis. The etiology and pathogenesis of RA remain unknown. Autoimmunity to cartilage alltigens may play a significant role in the pathogenesis ofchronic inflammatory polyarthritis. It is commonly accepted that cell mediated immune responses are involved in chronic inflammation since T and B lymphocytes andatigen presenting cells were observed to be enriched in the synovium fluid of RA…     

Specific overexpression of IL-7 in the intestinal mucosa: the role in intestinal intraepithelial lymphocyte development

IL-7 plays a crucial role in controlling T cell development and homeostasis. Since IL-7 may be derived from extraintestinal sources, and exogenous IL-7 broadly affects lymphoid populations, the actions of epithelial cell (EC)-derived IL-7 are not fully understood. The effect of intestinal specific expression of IL-7 on intestinal mucosal lymphocytes was investigated by using an IL-7 transgenic mouse model. We generated an intestinal EC-specific overexpressing IL-7 transgenic mouse model (IL-7(vill)) and compared their phenotype and function to wild-type C57BL/6J mice. EC-derived IL-7 overexpression was found to be exclusively in the small and large intestine. Numbers and subtypes of mucosal lymphocytes, including intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL), significantly changed in IL-7(vill) mice. From a functional standpoint, IEL proliferation also significantly increased in IL-7(vill) mice. IEL cytokine expression significantly changed in both T cell receptor (TCR)-alphabeta(+) and TCR-gammadelta(+) IEL subpopulations, including a significant increase in IFN-gamma and TNF-alpha as well as an increase in keratinocyte growth factor expression. EC expression of CD103 (integrin alpha(E)beta(7)), the ligand of E-cadherin, markedly upregulated and may account for a mechanism of the massive expansion of IEL in transgenic mice. Systemic lymphoid populations did not change in transgenic mice. IL-7 overexpression by intestinal EC significantly affected IEL phenotype and function. These results offer insight into the role of IL-7 in IEL development and suggest a critical role of EC-derived expression of IL-7 in the phenotype and function of IEL.     

Interactions between IL-32 and tumor necrosis factor alpha contribute to the exacerbation of immune-inflammatory diseases

IL-32 is a newly described cytokine in the human found to be an in vitro inducer of tumor necrosis factor alpha (TNFalpha). We examined the in vivo relationship between IL-32 and TNFalpha, and the pathologic role of IL-32 in the TNFalpha-related diseases - arthritis and colitis. We demonstrated by quantitative PCR assay that IL-32 mRNA was expressed in the lymphoid tissues, and in stimulated peripheral T cells, monocytes, and B cells. Activated T cells were important for IL-32 mRNA expression in monocytes and B cells. Interestingly, TNFalpha reciprocally induced IL-32 mRNA expression in T cells, monocyte-derived dendritic cells, and synovial fibroblasts. Moreover, IL-32 mRNA expression was prominent in the synovial tissues of rheumatoid arthritis patients, especially in synovial-infiltrated lymphocytes by in situ hybridization. To examine the in vivo relationship of IL-32 and TNFalpha, we prepared an overexpression model mouse of human IL-32beta (BM-hIL-32) by bone marrow transplantation. Splenocytes of BM-hIL-32 mice showed increased expression and secretion of TNFalpha, IL-1beta, and IL-6 especially in response to lipopolysaccharide stimulation. Moreover, serum TNFalpha concentration showed a clear increase in BM-hIL-32 mice. Cell-sorting analysis of splenocytes showed that the expression of TNFalpha was increased in resting F4/80+ macrophages, and the expression of TNFalpha, IL-1beta and IL-6 was increased in lipopolysaccharide-stimulated F4/80+ macrophages and CD11c+ dendritic cells. In fact, BM-hIL-32 mice showed exacerbation of collagen-antibody-induced arthritis and trinitrobenzen sulfonic acid-induced colitis. In addition, the transfer of hIL-32beta-producing CD4+ T cells significantly exacerbated collagen-induced arthritis, and a TNFalpha blockade cancelled the exacerbating effects of hIL-32beta. We therefore conclude that IL-32 is closely associated with TNFalpha, and contributes to the exacerbation of TNFalpha-related inflammatory arthritis and colitis.     

Transforming growth factor-beta and cellular immune responses in synovial fluids

Mononuclear cells in synovial fluids (SF) from patients with rheumatoid arthritis and other arthropathies are characterized by functional and phenotypic changes, including impaired mitogen responsiveness and inverted ratios of CD4+/CD8+ T lymphocytes. This is related to previously described activities in synovial fluids that inhibit proliferation of lymphocytes induced by mitogens and cytokines. The present study examines the relationship of these activities and transforming growth factor beta (TGF-beta), which is now known as the most potent endogenous inhibitor of lymphocyte function. It is shown that most of the activity in SF that inhibits IL-1-induced thymocyte or T cell proliferation is neutralized by a specific antibody to TGF-beta. Analysis of the SF in the CCL64 assay, a standard test for TGF-beta, showed a close correlation between the levels of immunosuppressive activity and TGF-beta. SF contain spontaneously active inhibitors of T cell function and this is caused by the presence of active TGF-beta. Higher titers are found after transient acidification, which is known to activate the latent form of TGF-beta. Characterization of the TGF-beta isoforms showed that most of the material in SF is TGF-beta 2. Analysis of TGF-beta effects on T cell subsets demonstrated that it completely inhibits proliferation of CD4+ cells whereas at the same concentrations of purified or rTGF-beta CD8+ cells are only inhibited by maximally 31.1%. SF also preferentially inhibit CD4+ Th cell proliferation and this effect is neutralized by antibody to TGF-beta. Collectively these results indicate that the presence of TGF-beta accounts for most of the immunosuppressive activities in SF and that this factor may be responsible for functional and phenotypic changes of SF lymphocytes.     

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.     

白细胞介素17在类风湿性关节炎中意义的探讨

白细胞介素17（interleukin-17,IL-17）是近年来发现的一种重要的炎症性细胞因子。主要由CD4＋效应T细胞的亚群-辅助性T细胞17（T help cell 17,Th17）、CD8＋T细胞和γδT细胞产生,能调节并促进多种炎性介质的产生,有强大的招募中性粒细胞的作用,在白细胞的迁移、破骨细胞的活化和骨质的吸收等方面发挥重要作用。近年来研究发现,IL-17与多种炎性疾病、感染、肿瘤、过敏、及自身免疫性疾病均有密切关系,尤其在类风湿性关节炎（rheumatoid arthritis,RA）发病的各个环节中起重要作用。本文对IL-17在类风湿性关节炎的发生、发展、诊断及治疗等方面的作用进行综述。     

Cytokine-stimulated T cells induce macrophage IL-10 production dependent on phosphatidylinositol 3-kinase and p70S6K: implications for rheumatoid arthritis

IL-10 is an anti-inflammatory cytokine produced in the joint in rheumatoid arthritis by macrophages and infiltrating blood lymphocytes. Regulation of its expression is poorly understood, but previous findings have suggested that physical interactions with T cells may play a role. This report investigates signalling mechanisms involved in the production of macrophage IL-10 upon interaction with fixed, cytokine-stimulated T cells (Tck). Elutriated monocytes were differentiated to macrophages by macrophage-colony-stimulating factor (M-CSF) and co-cultured with fixed T cells chronically stimulated in a cytokine cocktail of IL-2/IL-6/tumour necrosis factor (TNF)-α in the presence or absence of wortmannin and LY294002, inhibitors of phosphatidylinositol 3-kinase (PI3K), or of rapamycin, an inhibitor of p70 S6-kinase (p70S6K). Spontaneous IL-10 production by rheumatoid arthritis synovial-membrane mononuclear cells (RA-SMCs) and co-cultures of rheumatoid arthritis T cells (RA-Ts) and macrophages was also assessed. RA-T and Tck induction of macrophage IL-10 production was suppressed by cell separation and inhibition of PI3K and p70S6K. PI3K involvement was also shown by phosphorylation of the downstream effector protein kinase B. Spontaneous IL-10 production by RA-SMCs was also inhibited by LY294002 and depletion of the nonadherent (T-cell-enriched) fraction of the cell population. IL-10 production in RA-SMCs and M-CSF-primed macrophages, activated by interaction with Tck, is PI3K- and p70S6K-dependent.     

Cytokine-stimulated T cells induce macrophage IL-10 production dependent on phosphatidylinositol 3-kinase and p70S6K: implications for rheumatoid arthritis

IL-10 is an anti-inflammatory cytokine produced in the joint in rheumatoid arthritis by macrophages and infiltrating blood lymphocytes. Regulation of its expression is poorly understood, but previous findings have suggested that physical interactions with T cells may play a role. This report investigates signalling mechanisms involved in the production of macrophage IL-10 upon interaction with fixed, cytokine-stimulated T cells (Tck). Elutriated monocytes were differentiated to macrophages by macrophage-colony-stimulating factor (M-CSF) and co-cultured with fixed T cells chronically stimulated in a cytokine cocktail of IL-2/IL-6/tumour necrosis factor (TNF)-alpha in the presence or absence of wortmannin and LY294002, inhibitors of phosphatidylinositol 3-kinase (PI3K), or of rapamycin, an inhibitor of p70 S6-kinase (p70S6K). Spontaneous IL-10 production by rheumatoid arthritis synovial-membrane mononuclear cells (RA-SMCs) and co-cultures of rheumatoid arthritis T cells (RA-Ts) and macrophages was also assessed. RA-T and Tck induction of macrophage IL-10 production was suppressed by cell separation and inhibition of PI3K and p70S6K. PI3K involvement was also shown by phosphorylation of the downstream effector protein kinase B. Spontaneous IL-10 production by RA-SMCs was also inhibited by LY294002 and depletion of the nonadherent (T-cell-enriched) fraction of the cell population. IL-10 production in RA-SMCs and M-CSF-primed macrophages, activated by interaction with Tck, is PI3K- and p70S6K-dependent.     

Early rheumatoid arthritis is characterized by a distinct and transient synovial fluid cytokine profile of T cell and stromal cell origin

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis (RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines (e.g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-γ at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA.     

IL-6 signaling in autoimmunity, chronic inflammation and inflammation-associated cancer

IL-6 activates various cell types carrying the membrane bound IL-6R (classical IL-6 signaling) as well as IL-6R(-) gp130(+) cells via the soluble IL-6R (IL-6 trans-signaling). IL-6 signaling plays a pivotal role in controlling the differentiation and activation of T lymphocytes by inducing the Jak/STAT-3 and the Ras/Erk/C/EBP pathways. In particular, IL-6 modulates the resistance of T cells against apoptosis, induces activation of T helper cells and controls the balance between regulatory T cells and Th17 cells. Importantly, recent findings suggest that blockade of IL-6 signaling is effective in treating experimental models of autoimmune and chronic inflammatory diseases such as inflammatory bowel diseases, diabetes, multiple sclerosis, asthma and rheumatoid arthritis as well as models of inflammation-associated cancer. Thus, anti-IL-6/anti-IL-6R strategies emerge as promising novel approaches for therapy of inflammatory diseases in humans. In this review article, we discuss the latest findings on the role of IL-6 in experimental models of autoimmunity and cancer, as well as clinical perspectives.     

Amelioration of collagen-induced arthritis by blockade of inducible costimulator-B7 homologous protein costimulation

B7 homologous protein (B7h)/B7-related protein 1 (B7RP-1) is a new member of the B7 family of costimulatory molecules that specifically interacts with inducible costimulator (ICOS) expressed on activated T cells. Collagen type II (CII)-induced arthritis (CIA) is an experimental model of arthritis that has been used to dissect the pathogenesis of human rheumatoid arthritis. In this study, we have investigated the effect of neutralizing anti-B7h mAb on the development and disease progression of CIA. Administration of anti-B7h mAb significantly ameliorated the disease as assessed by clinical arthritis score and histology in the joints, and a beneficial effect was also obtained by a delayed treatment after the onset of disease. Expression of ICOS and B7h was observed in the inflamed synovial tissue as well as in the draining lymph nodes (LNs) and expansion of ICOS(+) T cells in the LN was reduced by the anti-B7h mAb treatment. Expression of mRNA for proinflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6 in the joints was inhibited by the treatment. Proliferative responses and production of IFN-gamma and IL-10 upon restimulation with CII in vitro were significantly inhibited in LN cells from the anti-B7h mAb-treated mice. Serum anti-CII IgG1, IgG2a, and IgG2b levels were also reduced. Our present results showed a beneficial effect of the B7h blockade on CIA through anti-inflammatory actions and inhibition of both Th1- and Th2-mediated immune responses, suggesting that the ICOS-B7h interaction plays an important role in the pathogenesis of CIA and thus the blockade of this pathway may be beneficial for the treatment of human rheumatoid arthritis.     

IL-17/Th17 targeting: on the road to prevent chronic destructive arthritis?

Interleukin-17A (IL-17A) contributes to the pathogenesis of arthritis. Data from experimental arthritis indicate IL-17 receptor signaling as a critical pathway in turning an acute synovitis into a chronic destructive arthritis. The identification of six IL-17 family members (IL-17A-F) may extend the role of this novel cytokine family in the pathogenesis of chronic destructive joint inflammation. Whether the successful anti-IL-17A cytokine therapy in murine arthritis can be effectively translated to human arthritis need to be tested in clinical trials in humans. Interestingly, IL-17A and IL-17F are secreted by the novel T helper subset named Th17. This novel pathogenic T cell population induces autoimmune inflammation in mice and is far more efficient at inducing Th1-mediated autoimmune inflammation in mice than classical Th1 cells (IFN-gamma). In addition to IL-17A and IL-17F, Th17 cells are characterized by expression of IL-6, TNF, GM-CSF, IL-21, IL-22 and IL-26. Th17 cells have been established as a separate lineage of T helper cells in mice distinct from conventional Th1 and Th2 cells. Whether this also applies to human Th17 and whether RA is a Th1 or a Th17 mediated disease is still not clear. This review summarizes the findings about the role of IL-17 in arthritis and discusses the impact of the discovery of the novel Th17 cells for arthritis. Further studies are needed to unravel the role of Th17 cells and the interplay of IL-17 and other Th17 cytokines in the pathogenesis of arthritis and whether regulating Th17 cell activity will have additional value compared to neutralizing IL-17A activity alone. This might help to reach the ultimate goal not only to treat RA patients but to prevent the development of this crippling disease.