Discovery of the Clinical Candidate IDOR-1117-2520: A Potent and Selective Antagonist of CCR6 for Autoimmune Diseases.

Migration of immune cells to sites of inflammation is a critical step in the body's response to infections but also during autoimmune flares. Chemokine receptors, members of the GPCR receptors, are instrumental in directing specific cell types to their target organs. Herein, we describe a highly potent small molecule antagonist of the chemokine receptor CCR6, which came out of fine-tuned structural elaborations from a proprietary HTS hit. Three main issues in the parent chemical series-cytotoxicity, phototoxicity, and hERG, were successfully solved. Biological characterization demonstrated that compound 45 (IDOR-1117-2520) is a selective and insurmountable antagonist of CCR6. In vivo proof-of-mechanism studies in a mouse lung inflammation model using a representative compound from the chemical class of 45 confirmed that the targeted CCR6+ cells were efficiently inhibited from migrating into the bronchoalveoli. Finally, ADMET and physicochemical properties were well balanced and the preclinical package warranted progress in the clinic.

Treatment with shCCL20-CCR6 nanodendriplexes and human mesenchymal stem cell therapy improves pathology in mice with repeated traumatic brain injury.

Traumatic brain injury (TBI) is a devastating neurological disorder, although the underlying pathophysiology is poorly understood. TBI causes blood-brain barrier (BBB) disruption, immune cell trafficking, neuroinflammation and neurodegeneration. CCL20 is an important chemokine mediating neuroinflammation. Human mesenchymal stem cell (hMSC) therapy is a promising regenerative approach but the inflammatory microenvironment in the brain tends to decrease the efficacy of the hMSC transplantation. Reducing the inflammation prior to hMSC therapy improves the outcome. We developed a combined nano-cell therapy by using dendrimers complexed with plasmids (dendriplexes) targeting CCL20 and its sole receptor CCR6 to reduce inflammation followed by hMSC transplantation. Treatment of TBI mice with shRNA conjugated dendriplexes followed by hMSC administration downregulated the inflammatory markers and significantly increased brain-derived neurotrophic factor (BDNF) expression in the cerebral cortex indicating future possible neurogenesis and improved behavioral deficits. Taken together, this nano-cell therapy ameliorates neuroinflammation and promotes brain tissue repair after TBI.

CCL20-CCR6 axis directs sperm-oocyte interaction and its dysregulation correlates/associates with male infertility‡.

The interaction of sperm with the oocyte is pivotal during the process of mammalian fertilization. The limited numbers of sperm that reach the fallopian tube as well as anatomic restrictions indicate that human sperm-oocyte encounter is not a matter of chance but a directed process. Chemotaxis is the proposed mechanism for re-orientating sperm toward the source of a chemoattractant and hence to the oocyte. Chemokines represent a superfamily of small (8-11 kDa), cytokine-like proteins that have been shown to mediate chemotaxis and tissue-specific homing of leukocytes through binding to specific chemokine receptors such as CCRs. Here we show that CCR6 is abundantly expressed on human sperms and in human testes. Furthermore, radioligand-binding experiments showed that CCL20 bound human sperm in a specific manner. Conversely, granulosa cells of the oocyte-surrounding cumulus complex as well as human oocytes represent an abundant source of the CCR6-specific ligand CCL20. In human ovaries, CCL20 shows a cycle-dependent expression pattern with peak expression in the preovulatory phase and CCL20 protein induces chemotactic responses of human sperm. Neutralization of CCL20 in ovarian follicular fluid significantly impairs sperm migratory responses. Conversely, analyses in infertile men with inflammatory conditions of the reproductive organs demonstrate a significant increase of CCL20/CCR6 expression in testis and ejaculate. Taken together, findings of the present study suggest that CCR6-CCL20 interaction may represent an important factor in directing sperm-oocyte interaction.

DEPDC1 drives hepatocellular carcinoma cell proliferation, invasion and angiogenesis by regulating the CCL20/CCR6 signaling pathway.

DEP domain containing 1 (DEPDC1) functions as an oncogene in hepatocellular carcinoma (HCC). However, the underlying mechanism of DEPDC1 remains largely unknown. The present study revealed that DEPDC1 knockdown inhibited HCC cell proliferation, colony formation and invasion in vitro and suppressed the growth of HCC xenografts in vivo. Furthermore, DEPDC1 overexpression promoted HCC cell proliferation, colony formation and invasion. DNA microarray, reverse transcription­quantitative­PCR and western blotting results demonstrated that DEPDC1 knockdown in Huh­7 significantly inhibited the expression of chemokine (C­C motif) ligand 20 (CCL20) and chemokine (C­C motif) receptor 6 (CCR6). In addition, the expression of CCL20 and CCR6 were upregulated in HCC tissues and cell lines, and were positively correlated with DEPDC1 expression. CCL20 or CCR6 knockdown via small interfering RNA reversed the effects of DEPDC1 overexpression in HCC cells. Furthermore, it was revealed that conditioned medium from DEPDC1 upregulated Li­7 and Hep3B cells led to angiogenesis in vitro, whereas CCL20 knockdown in Li­7 and Hep3B cells or CCR6 knockdown in human umbilical vein endothelial cells reversed the angiogenic effect of DEPDC1 overexpression. In conclusion, DEPDC1 facilitated cell proliferation, invasion and angiogenesis via the CCL20/CCR6 pathway in HCC.

Efficacy of Chemokine Receptor Inhibition in Treating IL-36α-Induced Psoriasiform Inflammation.

Several types of psoriasiform dermatitis are associated with increased IL-36 cytokine activity in the skin. A rare, but severe, psoriasis-like disorder, generalized pustular psoriasis (GPP), is linked to loss-of-function mutations in the gene encoding IL-36RA, an important negative regulator of IL-36 signaling. To understand the effects of IL-36 dysregulation in a mouse model, we studied skin inflammation induced by intradermal injections of preactivated IL-36α. We found the immune cells infiltrating IL-36α-injected mouse skin to be of dramatically different composition than those infiltrating imiquimod-treated skin. The IL-36α-induced leukocyte population comprised nearly equal numbers of CD4+ αß T cells, neutrophils, and inflammatory dendritic cells, whereas the imiquimod-induced population comprised γδ T cells and neutrophils. Ligands for chemokine receptors CCR6 and CXCR2 are increased in both GPP and IL-36α-treated skin, which led us to test an optimized small-molecule antagonist (CCX624) targeting CCR6 and CXCR2 in the IL-36α model. CCX624 significantly reduced the T cell, neutrophil, and inflammatory dendritic cell infiltrates and was more effective than saturating levels of an anti-IL-17RA mAb at reducing inflammatory symptoms. These findings put CCR6 and CXCR2 forward as novel targets for a mechanistically distinct therapeutic approach for inflammatory skin diseases involving dysregulated IL-36 signaling, such as GPP.

Modulation of the CCR6-CCL20 Axis: A Potential Therapeutic Target in Inflammation and Cancer.

Prototypical functions of the chemokine receptor CCR6 include immune regulation by maneuvering cell chemotaxis and selective delimiting of the pro-inflammatory TH17 and regulatory Treg subsets during chronic or acute systemic inflammation. Inhibition of CCR6 is proposed to attenuate disease symptoms and promote recuperation of multiple inflammatory and autoimmune disorders. Prescription medicines with pharmacodynamics involving the inhibition of the chemokine axis CCR6⁻CCL20 are very limited. The development of such therapeutics is still at an early experimental stage and has mostly involved the utilization of pre-clinical models and neutralizing mono or polyclonal antibodies against either partner (CCR6 or CCL20). Other methods include the constitutive use of small molecules as peptide inhibitors or small interfering ribonucleic acid (siRNA) to interfere with transcription at the nuclear level. In our review, we aim to introduce the wide array of potential CCR6⁻CCL20 inhibitors with an emphasis on attendant immune-modulator capacity that have been tested in the research field to date and are immensely promising compounds as forerunners of future curatives. Sixteen different tractable inhibitors of the CCR6⁻CCL20 duo have been identified as possessing high medicinal potential by drug developers worldwide to treat autoimmune and inflammatory diseases as shown in Figure 1. A multitude of antibody preparations are already available in the current pharmaceutical market as patented treatments for diseases in which the CCR6⁻CCL20 axis is operative, yet they must be used only as supplements with existing routinely prescribed medication as they collectively produce adverse side effects. Novel inhibitors are needed to evaluate this invaluable therapeutic target which holds much promise in the research and development of complaisant remedies for inflammatory diseases.

Identification of a novel series of potent and selective CCR6 inhibitors as biological probes.

CCR6 has been implicated in both autoimmune diseases and non-autoimmune diseases. Thus, inhibition of CCR6-dependent cell migration is an attractive strategy for their treatment. An orally available small molecule inhibitor of CCR6 could therefore be a useful biological probe for the pathophysiological studies. Initial SAR study of a hit compound provided potent N-benzenesulfonylpiperidine derivatives that suppressed CCL20-induced Gi signals. By subsequent scaffold morphing of the central ring and further optimization, we identified a novel series of 1,4-trans-1-benzenesulfonyl-4-aminocyclohexanes as potent and selective CCR6 inhibitors with good pharmacokinetic properties. Our compounds showed good correlation between Gi signal inhibitory activity and cell migration inhibitory activity in human CCR6-transfected CHO cells. In addition, representative compound 35 potently inhibited CCR6-dependent cell migration and the increase in ERK phosphorylation in human primary cells. Therefore, the compound could be used effectively as a biological probe against human CCR6.

A fully humanized IgG-like bispecific antibody for effective dual targeting of CXCR3 and CCR6.

Chemokines and their receptors are pivotal for the trafficking of leukocytes during immune responses, and host defense. However, immune cell migration also contributes to a wide variety of autoimmune and chronic inflammatory diseases. Compelling evidence suggests that both CXCR3 and CCR6 chemokine receptors play crucial roles in the migration of pathological Th1 and Th17 cells during the course of certain inflammatory diseases. The use of two or more receptors by pathogenic cells may explain why targeting of individual receptors has proven disappointing in the clinic. We therefore hypothesized that simultaneous targeting of both CXCR3 and CCR6 with a bispecific antibody (BsAb) might result in decreased chemotaxis and/or specific depletion of pro-inflammatory T cell subsets. In this study, we designed and characterized a fully humanized BsAb. We show that the BsAb binds to both chemokine receptors, as demonstrated by Flow Cytometry and Surface Plasmon Resonance analysis. Furthermore, we demonstrate that the BsAb effectively blocks cell chemotaxis and induces specific antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro. Therefore, we propose that dual targeting of CXCR3 and CCR6 with a fully humanized BsAb may display a potent interventional approach for the treatment of inflammatory and autoimmune diseases.

The RNA-binding protein HuR contributes to neuroinflammation by promoting C-C chemokine receptor 6 (CCR6) expression on Th17 cells.

In both multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), the C-C chemokine receptor 6 (CCR6) is critical for pathogenic T helper 17 (Th17) cell migration to the central nervous system (CNS). Whereas many cytokines and their receptors are potently regulated via post-transcriptional mechanisms in response to various stimuli, how CCR6 expression is post-transcriptionally regulated in Th17 cells is unknown. Here, using RNA-binding protein HuR conditional knock-out (KO) and wild-type (WT) mice, we present evidence that HuR post-transcriptionally regulates CCR6 expression by binding to and stabilizing Ccr6 mRNA and by promoting CCR6 translation. We also found that HuR down-regulates several microRNA expressions, which could target the 3'-UTR of Ccr6 mRNA for decay. Accordingly, knock-out of HuR reduced CCR6 expression on Th17 cells and impaired their migration to CNS compared with the response of WT Th17 cells and thereby ameliorated EAE. Together, these findings highlight how HuR contributes to Th17 cell-mediated autoimmune neuroinflammation and support the notion that targeting HuR might be a potential therapeutic intervention for managing autoimmune disorders of the CNS.

Chemokine/chemokine receptor pair CCL20/CCR6 in human colorectal malignancy: An overview.

Chemokines belong to a superfamily of small, cytokine-like proteins, which induce multiple physiological functions, particularly cytoskeletal rearrangement and compartment-specific migration through their interaction with G-protein-coupled receptors. Chemokines and their receptors have been widely acknowledged as essential and selective mediators in leukocyte migration in inflammatory response. It is now established that the chemokine/chemokine receptor system is also used by cancer cells to direct lymphatic and haematogenous spreading and additionally has an impact on the site of metastatic growth of different tumours. In recent years an increasing number of studies have drawn attention to CC-chemokine cysteine motif chemokine ligand 20 (CCL20) and its physiological sole receptor CCR6 to play a role in the onset, development and metastatic spread of various gastrointestinal cancer entities. Among various cancer types CCR6 was also demonstrated to be significantly overexpressed in colorectal cancer (CRC) and stimulation by its physiological ligand CCL20 has been reported to promote CRC cell proliferation and migration in vitro. Further, the CCL20/CCR6 system apparently plays a role in the organ-selective liver metastasis of CRC. Here we review the literature on expression patterns of CCL20 and CCR6 and their physiological interactions as well as the currently presumed role of CCL20 and CCR6 in the formation of CRC and the development of liver metastasis, providing a potential basis for novel treatment strategies.

Disruption of CCL20-CCR6 interaction inhibits metastasis of advanced cutaneous T-cell lymphoma.

We recently demonstrated that upregulation of a chemokine receptor CCR6 and its ligand CCL20 led to metastasis of advanced cutaneous T-cell lymphoma (CTCL) cells, suggesting the involvement of CCL20-CCR6 interaction in initiating CTCL cell metastasis. In this study, we determined whether this interaction is functional in metastatic CTCL cells. We first demonstrated increased STAT3 expression during the progression of primary CTCL. STAT3 was spontaneously activated and mediated the transcription of CCL20 in CTCL cell lines. Next, to determine whether the transient knockdown of STAT3, CCL20, or CCR6 or treatment with neutralizing antibody against CCL20 (neutralizing CCL20 antibody) could reduce the migration ability of CTCL cells, we conducted an in vitro migration assay. All treatments reduced the nutrition-dependent migration activity of CTCL cells. Notably, treatment with neutralizing CCL20 antibody reduced the migration ability of the cells without decreasing the expression of CCL20 and CCR6. This demonstrated that the CCL20-CCR6 interaction is actually functional in metastatic CTCL cells. Finally, to examine the in vivo effect of neutralizing CCL20 antibody, we used NOD/Shi-scid IL-2γnul mice inoculated with CTCL cells. These mice were expected to die due to metastasis of CTCL cells into multiple organs. However, administration of neutralizing CCL20 antibody significantly prolonged the survival of the xenografted mice. These findings suggested that automatic activation of the STAT3/CCL20/CCR6 cascade was involved in CTCL lymphomagenesis and that disruption of CCL20-CCR6 interaction could be a key therapeutic strategy against advanced CTCL.

The ribosomal S6 kinase inhibitor BI-D1870 ameliorated experimental autoimmune encephalomyelitis in mice.

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS) caused by the infiltration of TH1 and TH17 cells into the CNS. Ribosomal S6 kinase 2 (RSK2; RPS6KA3) regulates TH17 differentiation by attenuating RORγt transcriptional activities and IL-17A production. The pan-RSK inhibitor BI-D1870 also inhibits TH17 differentiation, but the effect of BI-D1870 in vivo remains unclear. Here, we generated mice with experimental autoimmune encephalomyelitis (EAE) and treated them with BI-D1870. BI-D1870 administration protected mice from EAE by reducing the infiltration of TH1 and TH17 cells into the CNS and decreasing mRNA levels of Ccr6 in TH17 cells. These results suggest that RSK inhibition is a promising strategy for the treatment of MS.

Human ß-defensin-3 promotes intestinal epithelial cell migration and reduces the development of necrotizing enterocolitis in a neonatal rat model.

BACKGROUND: The aim of this study was to investigate the effects of human ß-defensin-3 (hBD3) on intestinal wound healing and in a neonatal rat model of necrotizing enterocolitis (NEC). METHODS: Enterocyte migration and proliferation were detected in vitro and in vivo. The role of chemokine receptor CCR6 and its downstream signaling pathway was assessed. Newborn Sprague-Dawley rats were randomly divided into four groups: Control+NS, Control+hBD3, NEC+NS, and NEC+hBD3. Body weight, histological score, survival time, cytokines expression, and mucosal integrity were evaluated. RESULTS: hBD3 could stimulate enterocyte migration, but not proliferation, both in cultured enterocytes and in the NEC model. Neutralizing antibody and small interfering RNA confirmed this stimulatory effect was mediated by CCR6. Furthermore, hBD3 induced Rho activation, myosin light chain 2 phosphorylation, and F-actin accumulation. The bactericidal activity of hBD3 was maintained throughout a broad pH range. Strikingly, hBD3 administration decreased the incidence of NEC, increased the survival rate, and reduced the severity of NEC. Moreover, hBD3 reduced the proinflammatory cytokines expression in ileum and serum and preserved the intestinal barrier integrity. CONCLUSION: This study provided evidence that the antimicrobial peptide hBD3 might participate in intestinal wound healing by promoting enterocyte migration and show beneficial effects on newborn rats with NEC.

The effects of the CCR6/CCL20 biological axis on the invasion and metastasis of hepatocellular carcinoma.

Chemokines and their receptors have recently been shown to play major roles in cancer metastasis. Chemokine receptor 6 (CCR6) and its ligand, CCL20, were highly expressed in a variety of human cancers. In our present study, we aimed to clarify whether CCR6/CCL20 was correlated with the migration of hepatocellular carcinoma (HCC). RT-PCR and Western blot results showed that CCR6 was overexpressed in different invasive potential HCC cell lines (p<0.05), while the expression of CCL20 had no obvious difference (p>0.05). CCR6 was suppressed by siRNA in HCCLM6, and then the biological behaviors of HCCLM6 cells were observed. The results showed that the CCR6/CCL20 biological axis increased the capacity of proliferation and adhesion, as well as the chemotactic migration and the level of cytokines related to degraded extracellular matrix. In conclusion, these findings indicate that CCR6 indeed participates in regulating the migration and invasion of HCC, and it might become a prognostic factor of HCC.

Selective down-regulation of Th2 cell-mediated airway inflammation in mice by pharmacological intervention of CCR4.

BACKGROUND: The chemokine receptor CCR4 has been implicated in Th2 cell-mediated immune responses. However, other T cell subsets are also known to participate in allergic inflammation. OBJECTIVE: The role of CCR4 in Th1, Th2, and Th17 cell-mediated allergic airway inflammation was investigated. METHOD: We generated an allergic airway inflammation model by adoptive transfer of in vitro-polarized ovalbumin (OVA)-specific Th1, Th2, and Th17 cells. The effect of a low-molecular weight CCR4 antagonist, Compound 22, on this model was examined. RESULTS: Upon in vitro polarization of DO11.10 naïve T cells, Th1- and Th2-polarized cells dominantly expressed CXCR3 and CCR4, respectively, while Th17-polarized cells expressed CCR6 and CCR4. Intranasal OVA-challenge of mice transferred with each T cell subset induced accumulation of T cells in the lungs. Eosinophils were also massively accumulated in Th2-transferred mice, whereas neutrophils were preferentially recruited in Th1- and Th17-transferred mice. Compound 22, as well as anti-CCL17 or anti-CCL22 antibody selectively suppressed accumulation of Th2 cells and eosinophils in the lungs of Th2-transferred and OVA-challenged mice. Compound 22 also inhibited bronchial hyperresponsiveness but had little effect on goblet cell hyperplasia in Th2-transferred and OVA-challenged mice. CONCLUSIONS AND CLINICAL RELEVANCE: There were notable differences in allergic lung inflammation mediated by different T cell subsets. CCR4 blockage was selectively effective for suppression of Th2-mediated allergic inflammation by blocking infiltration of Th2 cells.

CCR6 as a possible therapeutic target in psoriasis.

IMPORTANCE OF THE FIELD: Psoriasis is a common, chronic autoimmune disease of the skin. Despite a number of effective treatments, new therapies are needed with enhanced efficacy, safety and convenience. Chemokine receptors are GPCRs that control leukocyte trafficking, and like other GPCRs, are good potential drug targets. The chemokine receptor CCR6 is expressed on the T(H)17 subset of CD4(+) T cells, which produces IL-17A/F, IL-22, TNF-alpha and other cytokines, and which has been implicated in the pathogenesis of psoriasis. CCR6 and its ligand, CCL20/MIP-3alpha, are highly expressed in psoriatic skin and CCR6 is necessary for the pathology induced in a mouse model of psoriasis-like inflammation. AREAS COVERED IN THIS REVIEW: This review summarizes the evidence for the importance of the IL-23/T(H)17 axis, and in particular CCR6 and CCL20 in psoriasis, dating from 2000 to the present, and discusses the possibility of inhibiting CCR6 as a treatment for the disease. WHAT THE READER WILL GAIN: The review informs the reader of the current thinking on the mechanisms of inflammation in psoriasis and the possible roles for CCR6 (and CCL20) in disease pathogenesis. TAKE HOME MESSAGE: We conclude that CCR6 should be investigated as a potential therapeutic target in psoriasis.

IFN-beta inhibits human Th17 cell differentiation.

IFN-beta-1a has been used over the past 15 years as a primary therapy for relapsing-remitting multiple sclerosis (MS). However, the immunomodulatory mechanisms that provide a therapeutic effect against this CNS inflammatory disease are not yet completely elucidated. The effect of IFN-beta-1a on Th17 cells, which play a critical role in the development of the autoimmune response, has not been extensively studied in humans. We have investigated the effect of IFN-beta-1a on dendritic cells (DCs) and naive CD4(+)CD45RA(+) T cells derived from untreated MS patients and healthy controls in the context of Th17 cell differentiation. We report that IFN-beta-1a treatment down-regulated the expression of IL-1beta and IL-23p19 in DCs, whereas it induced the gene expression of IL-12p35 and IL-27p28. We propose that IFN-beta-1a-mediated up-regulation of the suppressor of cytokine signaling 3 expression, induced via STAT3 phosphorylation, mediates IL-1beta and IL-23 down-regulation, while IFN-beta-1a-induced STAT1 phosphorylation induces IL-27p28 expression. CD4(+)CD45RA(+) naive T cells cocultured with supernatants from IFN-beta-1a-treated DCs exhibited decreased gene expression of the Th17 cell markers retinoic acid-related orphan nuclear hormone receptor c (RORc), IL-17A, and IL-23R. A direct IFN-beta-1a treatment of CD45RA(+) T cells cultured in Th17-polarizing conditions also down-regulated RORc, IL-17A, and IL-23R, but up-regulated IL-10 gene expression. Studies of the mechanisms involved in the Th17 cell differentiation suggest that IFN-beta-1a inhibits IL-17 and induces IL-10 secretion via activated STAT1 and STAT3, respectively. IFN-beta's suppression of Th17 cell differentiation may represent its most relevant mechanism of selective suppression of the autoimmune response in MS.

Inhibition of CCR6 function reduces the severity of experimental autoimmune encephalomyelitis via effects on the priming phase of the immune response.

Chemokines are essential for homeostasis and activation of the immune system. The chemokine ligand/receptor pairing CCL20/CCR6 is interesting because these molecules display characteristics of both homeostatic and activation functions. These dual characteristics suggest a role for CCR6 in the priming and effector phases of the immune response. However, while CCR6 has been implicated in the effector phase in several models, a role in the priming phase is less clear. Herein we analyze the role of CCR6 in these two important arms of the immune response during experimental autoimmune encephalomyelitis (EAE). Both CCR6 and its chemokine ligand CCL20 were up-regulated in the draining lymph nodes and spinal cord during EAE, and CCR6 was up-regulated on CD4(+) T cells that had divided following induction of EAE. The functional role of this expression was demonstrated by impaired development of EAE in gene-targeted CCR6-deficient mice and in mice treated either with a neutralizing anti-CCR6 Ab or with a novel receptor antagonist. Inhibition of EAE was due to reduced priming of autoreactive CD4(+) T cells probably as a result of impaired late-stage influx of dendritic cells into draining lymph nodes. This was accompanied by reduced egress of activated lymphocytes from the lymph nodes. These results demonstrate a novel role for CCR6 in the mechanism of autoreactive lymphocyte priming and emigration to the efferent lymphatics.

Preferential recruitment of CCR6-expressing Th17 cells to inflamed joints via CCL20 in rheumatoid arthritis and its animal model.

This report shows that interleukin (IL) 17-producing T helper type 17 (Th17) cells predominantly express CC chemokine receptor (CCR) 6 in an animal model of rheumatoid arthritis (RA). Th17 cells induced in vivo in normal mice via homeostatic proliferation similarly express CCR6, whereas those inducible in vitro by transforming growth factor beta and IL-6 additionally need IL-1 and neutralization of interferon (IFN) gamma and IL-4 for CCR6 expression. Forced expression of RORgamma t, a key transcription factor for Th17 cell differentiation, induces not only IL-17 but also CCR6 in naive T cells. Furthermore, Th17 cells produce CCL20, the known ligand for CCR6. Synoviocytes from arthritic joints of mice and humans also produce a large amount of CCL20, with a significant correlation (P = 0.014) between the amounts of IL-17 and CCL20 in RA joints. The CCL20 production by synoviocytes is augmented in vitro by IL-1beta, IL-17, or tumor necrosis factor alpha, and is suppressed by IFN-gamma or IL-4. Administration of blocking anti-CCR6 monoclonal antibody substantially inhibits mouse arthritis. Thus, the joint cytokine milieu formed by T cells and synovial cells controls the production of CCL20 and, consequently, the recruitment of CCR6+ arthritogenic Th17 cells to the inflamed joints. These results indicate that CCR6 expression contributes to Th17 cell function in autoimmune disease, especially in autoimmune arthritis such as RA.