Cross reactivity of three T cell attracting murine chemokines stimulating the CXC chemokine receptor CXCR3 and their induction in cultured cells and during allograft rejection

The intratumoral CXCR3 chemokine system is predictive of chemotherapy response in human bladder cancer

Chemotherapy has direct toxic effects on cancer cells; however, long-term cancer control and complete remission are likely to involve CD8⁺ T cell immune responses. To study the role of CD8⁺ T cell infiltration in the success of chemotherapy, we examined patients with muscle invasive bladder cancer (MIBC) who were categorized on the basis of the response to neoadjuvant chemotherapy (NAC). We identified the intratumoral CXCR3 chemokine system (ligands and receptor splice variants) as a critical component for tumor eradication upon NAC in MIBC. Through characterization of CD8⁺ T cells, we found that stem-like T cell subpopulations with abundant CXCR3alt, a variant form of the CXCL11 receptor, responded to CXCL11 in culture as demonstrated by migration and enhanced effector function. In tumor biopsies of patients with MIBC accessed before treatment, CXCL11 abundance correlated with high numbers of tumor-infiltrating T cells and response to NAC. The presence of CXCR3alt and CXCL11 was associated with improved overall survival in MIBC. Evaluation of both CXCR3alt and CXCL11 enabled discrimination between responder and nonresponder patients with MIBC before treatment. We validated the prognostic role of the CXCR3-CXCL11 chemokine system in an independent cohort of chemotherapy-treated and chemotherapy-naïve patients with MIBC from data in TCGA. In summary, our data revealed stimulatory activity of the CXCR3alt-CXCL11 chemokine system on CD8⁺ T cells that is predictive of chemotherapy responsiveness in MIBC. This may offer immunotherapeutic options for targeted activation of intratumoral stem-like T cells in solid tumors.

Diagnostic value of CXCR3 and its ligands in spinal tuberculosis

The present study aimed to investigate whether C-X-C motif chemokine receptor 3 (CXCR3) and its ligands may aid in diagnosing spinal tuberculosis (ST). A total of 36 patients with ST and 20 healthy controls were enrolled in the present study. The morphology of tuberculous granuloma in spinal tissue was observed by hematoxylin and eosin staining. The presence and distribution of acid-fast bacilli (AFB) were observed by Ziehl-Neelsen (ZN) staining. The protein expression of Ag85B, IFN-γ, and CXCR3 and its ligands (CXCL9 and CXCL10) were detected by immunohistochemistry. The levels of IFN-γ, CXCR3, CXCL9 and CXCL10 in peripheral blood of patients with ST and healthy controls were detected by reverse transcription-quantitative polymerase chain reaction and ELISA. Typical tuberculous granuloma was observed in the ST close tissue. AFB was observed by ZN staining. Positive expression of Ag85B was found in the surrounding caseous necrotic tissue of the tuberculous granuloma. IFN-γ, CXCR3, CXCL9 and CXCL10 were expressed in the tissue surrounding the tuberculous granuloma and their expression levels were markedly higher than those in the distant tissues. The levels of IFN-γ, CXCR3, CXCL9 and CXCL10 in peripheral blood of patients with ST were significantly higher than those in the healthy controls. Receiver operating characteristic curve analysis demonstrated that IFN-γ, CXCR3 and CXCL10 were more reliable diagnostic markers in terms of sensitivity and specificity. IFN-γ, CXCR3, CXCL9 and CXCL10 were highly expressed in the lesion tissue and peripheral blood samples of patients with ST, and IFN-γ, CXCR3 and its ligands aided in diagnosing ST.

The Development and Homing of Myeloid-Derived Suppressor Cells: From a Two-Stage Model to a Multistep Narrative

Myeloid-derived suppressor cells (MDSC) represent a heterogeneous population of immature myeloid cells. Under normal conditions, they differentiate into macrophages, dendritic cells, and granulocytes. Under pathological conditions, such as chronic inflammation, or cancer, they tend to maintain their immature state as immature myeloid cells that, within the tumor microenvironment, become suppressor cells and assist tumor escape from immune eradication. MDSC are comprised of two major subsets: monocytic MDSC (M-MDSC) and polymorphonuclear MDSC (PMN-MDSC). Monocytic myeloid cells give rise to monocytic cells, whereas PMN-MDSC share similarities with neutrophils. Based on their biological activities, a two-stage model that includes the mobilization of the periphery as myeloid cells and their activation within the tumor microenvironment converting them into suppressor cells was previously suggested by D. Gabrilovich. From the migratory viewpoint, we are suggesting a more complex setup. It starts with crosstalk between the tumor site and the hematopoietic stem and progenitor cells (HSPCs) at the bone marrow (BM) and secondary lymphatic organs, resulting in rapid myelopoiesis followed by mobilization to the blood. Although myelopoiesis is coordinated by several cytokines and transcription factors, mobilization is selectively directed by chemokine receptors and may differ between M-MDSC and PMN-MDSC. These myeloid cells may then undergo further expansion at these secondary lymphatic organs and then home to the tumor site. Finally, selective homing of T cell subsets has been associated with retention at the target organs directed by adhesion molecules or chemokine receptors. The possible relevance to myeloid cells is still speculative but is discussed.

The N-terminal length and side-chain composition of CXCL13 affect crystallization, structure and functional activity

CXCL13 is the cognate chemokine agonist of CXCR5, a class A G-protein-coupled receptor (GPCR) that is essential for proper humoral immune responses. Using a `methionine scanning' mutagenesis method on the N-terminus of CXCL13, which is the chemokine signaling region, it was shown that minor length alterations and side-chain substitutions still result in CXCR5 activation. This observation indicates that the orthosteric pocket of CXCR5 can tolerate these changes without severely affecting the activity. The introduction of bulk on the ligand was well tolerated by the receptor, whereas a loss of contacts was less tolerated. Furthermore, two crystal structures of CXCL13 mutants were solved, both of which represent the first uncomplexed structures of the human protein. These structures were stabilized by unique interactions formed by the N-termini of the ligands, indicating that CXCL13 exhibits substantial N-terminal flexibility while the chemokine core domain remains largely unchanged. Additionally, it was observed that CXCL13 harbors a large degree of flexibility in the C-terminal extension of the ligand. Comparisons with other published structures of human and murine CXCL13 validate the relative rigidity of the core domain as well as the N- and C-terminal mobilities. Collectively, these mutants and their structures provide the field with additional insights into how CXCL13 interacts with CXCR5.

Effective Treatments for Bladder Cancer Affecting CXCL9/CXCL10/CXCL11/CXCR3 Axis: A Review

Bladder cancer (BC) originates mainly from the epithelial compartment of the bladder, which is defined as transitional cell carcinoma or urothelial cell carcinoma. About 70% of patients with BC will survive five years from diagnosis. Previous studies revealed that the immune system and its mediators, particularly chemokines, play a crucial role in modulating responses against BC. Chemokines, which serve as chemoattractants for leukocytes, are small proteins that can initiate inflammatory and anti-inflammatory immune responses and also are associated with many aspects of both regulation and progression of mentioned responses. Additionally, these immune mediators can interfere with the other tumor-related processes, including tumor proliferation, neovascularization, and metastases. Among these chemokines, CXC chemokines, including CXCL9, CXCL10, and CXCL11, are recognized as the main ligands of C-X-C motif chemokine receptor 3 (CXCR3) and contribute to related immune responses after therapeutic strategies for BC. Evidence suggests that the production of these chemokines can have two important implications. First, these mediators can trigger the accumulation of CD8+ T cells that can contribute to the elimination of the tumor. Secondly, the production of these chemokines by tumor tissue may trigger the migration and activation of immune cells including myeloid-derived suppressor cells and regulatory T cells, which act in favor of the tumor and its progress. Therefore, in this review, we describe the latest therapeutic approaches based on targeting this axis's components and subsequent immune phenomenon.

IFNγ-induced Chemokines Are Required for CXCR3-mediated T-Cell Recruitment and Antitumor Efficacy of Anti-HER2/CD3 Bispecific Antibody

PURPOSE

The response to cancer immune therapy is dependent on endogenous tumor-reactive T cells. To bypass this requirement, CD3-bispecific antibodies have been developed to induce a polyclonal T-cell response against the tumor. Anti-HER2/CD3 T-cell-dependent bispecific (TDB) antibody is highly efficacious in the treatment of HER2-overexpressing tumors in mice. Efficacy and immunologic effects of anti-HER2/CD3 TDB were investigated in mammary tumor model with very few T cells prior treatment. We further describe the mechanism for TDB-induced T-cell recruitment to tumors.

EXPERIMENTAL DESIGN

The immunologic effects and the mechanism of CD3-bispecific antibody-induced T-cell recruitment into spontaneous HER2-overexpressing mammary tumors was studied using human HER2 transgenic, immunocompetent mouse models.

RESULTS

Anti-HER2/CD3 TDB treatment induced an inflammatory response in tumors converting them from poorly infiltrated to an inflamed, T-cell abundant, phenotype. Multiple mechanisms accounted for the TDB-induced increase in T cells within tumors. TDB treatment induced CD8⁺ T-cell proliferation. T cells were also actively recruited post-TDB treatment by IFNγ-dependent T-cell chemokines mediated via CXCR3. This active T-cell recruitment by TDB-induced chemokine signaling was the dominant mechanism and necessary for the therapeutic activity of anti-HER2/CD3 TDB.

CONCLUSIONS

In summary, we demonstrate that the activity of anti-HER2/CD3 TDB was not dependent on high-level baseline T-cell infiltration. Our results suggest that anti-HER2/CD3 TDB may be efficacious in patients and indications that respond poorly to checkpoint inhibitors. An active T-cell recruitment mediated by TDB-induced chemokine signaling was the major mechanism for T-cell recruitment.

Co-encapsulation and co-transplantation of mesenchymal stem cells reduces pericapsular fibrosis and improves encapsulated islet survival and function when allografted

Pericapsular fibrotic overgrowth (PFO) is associated with poor survival of encapsulated islets. A strategy to combat PFO is the use of mesenchymal stem cells (MSC). MSC have anti-inflammatory properties and their potential can be enhanced by stimulation with proinflammatory cytokines. This study investigated whether co-encapsulation or co-transplantation of MSC with encapsulated islets would reduce PFO and improve graft survival. Stimulating MSC with a cytokine cocktail of IFN-γ and TNF-α enhanced their immunosuppressive potential by increasing nitric oxide production and secreting higher levels of immunomodulatory cytokines. In vitro, co-encapsulation with MSC did not affect islet viability but significantly enhanced glucose-induced insulin secretion. In vivo, normoglycemia was achieved in 100% mice receiving islets co-encapsulated with stimulated MSC as opposed to 71.4% receiving unstimulated MSC and only 9.1% receiving encapsulated islets alone. Microcapsules retrieved from both unstimulated and stimulated MSC groups had significantly less PFO with improved islet viability and function compared to encapsulated islets alone. Levels of peritoneal immunomodulatory cytokines IL-4, IL-6, IL-10 and G-CSF were significantly higher in MSC co-encapsulated groups. Similar results were obtained when encapsulated islets and MSC were co-transplanted. In summary, co-encapsulation or co-transplantation of MSC with encapsulated islets reduced PFO and improved the functional outcome of allotransplants.

Transcription Factor Networks derived from Breast Cancer Stem Cells control the immune response in the Basal subtype

Breast cancer is the most common cancer in women worldwide and metastatic dissemination is the principal factor related to death by this disease. Breast cancer stem cells (bCSC) are thought to be responsible for metastasis and chemoresistance. In this study, based on whole transcriptome analysis from putative bCSC and reverse engineering of transcription control networks, we identified two networks associated with this phenotype. One controlled by SNAI2, TWIST1, BNC2, PRRX1 and TBX5 drives a mesenchymal or CSC-like phenotype. The second network is controlled by the SCML4, ZNF831, SP140 and IKZF3 transcription factors which correspond to immune response modulators. Immune response network expression is correlated with pathological response to chemotherapy, and in the Basal subtype is related to better recurrence-free survival. In patient-derived xenografts, the expression of these networks in patient tumours is predictive of engraftment success. Our findings point out a potential molecular mechanism underlying the balance between immune surveillance and EMT activation in breast cancer. This molecular mechanism may be useful to the development of new target therapies.

Tissue-specific regulation of CXCL9/10/11 chemokines in keratinocytes: Implications for oral inflammatory disease

The IFN-γ-inducible chemokines CXCL9, CXCL10, and CXCL11 play a key role in many inflammatory conditions, particularly those mediated by T cells. Therefore, the production of these chemokines in peripheral tissues could be instrumental in the pathophysiology of tissue-specific immunological diseases such as oral lichen planus (OLP). In the present study, we assessed the production of keratinocyte-derived CXCL9/10/11 under basal and inflammatory conditions and investigated whether these chemokines were involved in the pathogenesis of OLP. We used semi-quantitative PCR, ELISA, chemotaxis assays, and fluorescence-activated cell sorting (FACS) to assess the expression and functional role of CXCL9/10/11 in oral keratinocytes (three strains of normal human oral keratinocytes (NHOK), and the H357 oral cancer cell line) in the presence or absence of IFN-γ. CXCL9/10/11 were also assessed in tissues from normal patients and those with oral lichen planus (OLP). The time course study in oral keratinocytes treated with IFN-γ showed that expression of CXCL9/10/11 chemokines was significantly enhanced by IFN-γ in a time-dependent manner. In particular, CXCL10, a prominent chemokine that was overexpressed by IFN-γ-stimulated NHOK, was able to effectively recruit CD4 lymphocytes, mainly CD4+CD45RA- cells. Significantly higher levels of CXCL9/10/11 were found in tissues from patients with OLP compared to normal oral mucosa. Taken together, the results demonstrate that normal oral keratinocytes produce chemotactic molecules that mediate T cell recruitment. This study furthers understanding of chemokine production in oral keratinocytes and their role in the pathophysiology of oral mucosa, with particular relevance to OLP.

Antimicrobial activity and regulation of CXCL9 and CXCL10 in oral keratinocytes

Chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10 are dysregulated in oral inflammatory conditions, and it is not known if these chemokines target microorganisms that form oral biofilm. The aim of this study was to investigate the antimicrobial activity of CXCL9 and CXCL10 on oral microflora and their expression profiles in oral keratinocytes following exposure to inflammatory and infectious stimuli. Streptococcus sanguinis was used as a model and Escherichia coli as a positive control. The antimicrobial effect of CXCL9/CXCL10 was tested using a radial diffusion assay. mRNA transcripts were isolated from lipopolysaccharide (LPS)-treated and untreated (control) oral keratinocyte cell lines at 2-, 4-, 6-, and 8-h time-points of culture. The CXCL9/10 expression profile in the presence or absence of interferon-γ (IFN-γ) was assessed using semiquantitative PCR. Although both chemokines demonstrated antimicrobial activity, CXCL9 was the most effective chemokine against both S. sanguinis and E coli. mRNA for CXCL10 was expressed in control cells and its production was enhanced at all time-points following stimulation with LPS. Conversely, CXCL9 mRNA was not expressed in control or LPS-stimulated cells. Finally, stimulation with IFN-γ enhanced basal expression of both CXCL9 and CXCL10 in oral keratinocytes. Chemokines derived from oral epithelium, particularly CXCL9, demonstrate antimicrobial properties. Bacterial and inflammatory-stimulated up-regulation of CXCL9/10 could represent a key element in oral bacterial colonization homeostasis and host-defense mechanisms.

PRMT5-Mediated Methylation of NF-κB p65 at Arg174 Is Required for Endothelial CXCL11 Gene Induction in Response to TNF-α and IFN-γ Costimulation

Inflammatory agonists differentially activate gene expression of the chemokine family of proteins in endothelial cells (EC). TNF is a weak inducer of the chemokine CXCL11, while TNF and IFN-γ costimulation results in potent CXCL11 induction. The molecular mechanisms underlying TNF plus IFN-γ-mediated CXCL11 induction are not fully understood. We have previously reported that the protein arginine methyltransferase PRMT5 catalyzes symmetrical dimethylation of the NF-κB subunit p65 in EC at multiple arginine residues. Methylation of Arg30 and Arg35 on p65 is critical for TNF induction of CXCL10 in EC. Here we show that PRMT5-mediated methylation of p65 at Arg174 is required for induction of CXCL11 when EC are costimulated with TNF and IFN-γ. Knockdown of PRMT5 by RNAi reduced CXCL11 mRNA and protein levels in costimulated cells. Reconstitution of p65 Arg174Ala or Arg174Lys mutants into EC that were depleted of endogenous p65 blunted TNF plus IFN-γ-mediated CXCL11 induction. Mass spectrometric analyses showed that p65 Arg174 arginine methylation is enhanced by TNF plus IFN-γ costimulation, and is catalyzed by PRMT5. Chromatin immunoprecipitation assays (ChIP) demonstrated that PRMT5 is necessary for p65 association with the CXCL11 promoter in response to TNF plus IFN-γ. Further, reconstitution of p65 Arg174Lys mutant in EC abrogated this p65 association with the CXCL11 promoter. Finally, ChIP and Re-ChIP assays revealed that symmetrical dimethylarginine-containing proteins complexed with the CXCL11 promoter were diminished in p65 Arg174Lys-reconstituted EC stimulated with TNF and IFN-γ. In total, these results indicate that PRMT5-mediated p65 methylation at Arg174 is essential for TNF plus IFN-γ-mediated CXCL11 gene induction. We therefore suggest that the use of recently developed small molecule inhibitors of PRMT5 may present a therapeutic approach to moderating chronic inflammatory pathologies.

Emerging importance of chemokine receptor CXCR3 and its ligands in cardiovascular diseases

The CXC chemokines, CXCL4, -9, -10, -11, CXCL4L1, and the CC chemokine CCL21, activate CXC chemokine receptor 3 (CXCR3), a cell-surface G protein-coupled receptor expressed mainly by Th1 cells, cytotoxic T (Tc) cells and NK cells that have a key role in immunity and inflammation. However, CXCR3 is also expressed by vascular smooth muscle and endothelial cells, and appears to be important in controlling physiological vascular function. In the last decade, evidence from pre-clinical and clinical studies has revealed the participation of CXCR3 and its ligands in multiple cardiovascular diseases (CVDs) of different aetiologies including atherosclerosis, hypertension, cardiac hypertrophy and heart failure, as well as in heart transplant rejection and transplant coronary artery disease (CAD). CXCR3 ligands have also proven to be valid biomarkers for the development of heart failure and left ventricular dysfunction, suggesting an underlining pathophysiological relation between levels of these chemokines and the development of adverse cardiac remodelling. The observation that several of the above-mentioned chemokines exert biological actions independent of CXCR3 provides both opportunities and challenges for developing effective drug strategies. In this review, we provide evidence to support our contention that CXCR3 and its ligands actively participate in the development and progression of CVDs, and may additionally have utility as diagnostic and prognostic biomarkers.

Mouse genome annotation by the RefSeq project

Complete and accurate annotation of the mouse genome is critical to the advancement of research conducted on this important model organism. The National Center for Biotechnology Information (NCBI) develops and maintains many useful resources to assist the mouse research community. In particular, the reference sequence (RefSeq) database provides high-quality annotation of multiple mouse genome assemblies using a combinatorial approach that leverages computation, manual curation, and collaboration. Implementation of this conservative and rigorous approach, which focuses on representation of only full-length and non-redundant data, produces high-quality annotation products. RefSeq records explicitly link sequences to current knowledge in a timely manner, updating public records regularly and rapidly in response to nomenclature updates, addition of new relevant publications, collaborator discussion, and user feedback. Whole genome re-annotation is also conducted at least every 12-18 months, and often more frequently in response to assembly updates or availability of informative data. This article highlights key features and advantages of RefSeq genome annotation products and presents an overview of NCBI processes to generate these data. Further discussion of NCBI's resources highlights useful features and the best methods for accessing our data.

CXCL12-CXCR7 axis is important for tumor endothelial cell angiogenic property

We reported that tumor endothelial cells (TECs) differ from normal endothelial cells (NECs) in many aspects, such as gene expression profiles. Although CXCR7 is reportedly highly expressed in blood vessels of several tumors, its function in TECs is still unknown. To investigate this role, we isolated TECs from mouse tumor A375SM xenografts, and compared them with NECs from normal mouse dermis. After confirming CXCR7 upregulation in TECs, we analyzed its function using CXCR7 siRNA and CXCR7 inhibitor; CCX771. CXCR7 siRNA and CCX771 inhibited migration, tube formation and resistance to serum starvation in TECs but not in NECs. ERK1/2 phosphorylation was inhibited by CXCR7 knockdown in TECs. These results suggest that CXCR7 promotes angiogenesis in TECs via ERK1/2 phosphorylation. Using ELISA, we also detected CXCL12, a ligand of CXCR7, in conditioned medium from TECs, but not from NECs. CXCL12 neutralizing antibody significantly inhibited TEC random motility. VEGF stimulation upregulated CXCR7 expression in NECs, implying that VEGF mediates CXCR7 expression in endothelial cells. A CXCR7 inhibitor, CCX771 also inhibited tumor growth, lung metastasis and tumor angiogenesis in vivo. Taken together, the CXCL12-CXCR7 autocrine loop affects TEC proangiogenic properties, and could be the basis for an antiangiogenic therapy that specifically targets tumor blood vessels rather than normal vessels.

Chemokine Transfer by Liver Sinusoidal Endothelial Cells Contributes to the Recruitment of CD4+ T Cells into the Murine Liver

Leukocyte adhesion and transmigration are central features governing immune surveillance and inflammatory reactions in body tissues. Within the liver sinusoids, chemokines initiate the first crucial step of T-cell migration into the hepatic tissue. We studied molecular mechanisms involved in endothelial chemokine supply during hepatic immune surveillance and liver inflammation and their impact on the recruitment of CD4⁺ T cells into the liver. In the murine model of Concanavalin A-induced T cell-mediated hepatitis, we showed that hepatic expression of the inflammatory CXC chemokine ligands (CXCL)9 and CXCL10 strongly increased whereas homeostatic CXCL12 significantly decreased. Consistently, CD4⁺ T cells expressing the CXC chemokine receptor (CXCR)3 accumulated within the inflamed liver tissue. In histology, CXCL9 was associated with liver sinusoidal endothelial cells (LSEC) which represent the first contact site for T-cell immigration into the liver. LSEC actively transferred basolaterally internalized CXCL12, CXCL9 and CXCL10 via clathrin-coated vesicles to CD4⁺ T cells leading to enhanced transmigration of CXCR4⁺ total CD4⁺ T cells and CXCR3⁺ effector/memory CD4⁺ T cells, respectively in vitro. LSEC-expressed CXCR4 mediated CXCL12 transport and blockage of endothelial CXCR4 inhibited CXCL12-dependent CD4⁺ T-cell transmigration. In contrast, CXCR3 was not involved in the endothelial transport of its ligands CXCL9 and CXCL10. The clathrin-specific inhibitor chlorpromazine blocked endothelial chemokine internalization and CD4⁺ T-cell transmigration in vitro as well as migration of CD4⁺ T cells into the inflamed liver in vivo. Moreover, hepatic accumulation of CXCR3⁺ CD4⁺ T cells during T cell-mediated hepatitis was strongly reduced after administration of chlorpromazine. These data demonstrate that LSEC actively provide perivascularly expressed homeostatic and inflammatory chemokines by CXCR4- and clathrin-dependent intracellular transport mechanisms thereby contributing to the hepatic recruitment of CD4⁺ T-cell populations during immune surveillance and liver inflammation.

Listr1 locus regulates innate immunity against Listeria monocytogenes infection in the mouse liver possibly through Cxcl11 polymorphism

Inbred stains of mice display differential susceptibility to infection with the common foodborne pathogen Listeria monocytogenes (Lm). Previously, Listr1 and Listr2, two genetic loci that control differential sensitivity to Lm infection between BALB/cByJ and C57BL/6ByJ mice, were identified. To analyze the role of Listr1 in innate immune responses, we employed congenic mice (C.B6By-Listr1/Rag2 (-/-) ) bearing the C57BL/6ByJ-derived Listr1 locus on a BALB/c-Rag2 (-/-) background. Consistent with the results of a previous genetic analysis, the congenic mice showed increased susceptibility to Lm infection. The bacterial burden in the liver between the congenic and control lines was significantly different (P < 0.05) from 24 h postinfection with Lm. Analysis of genes within the Listr1 locus identified a frameshift mutation in the Cxcl11 gene of the C57BL/6 strain that prevents production of the mature chemokine CXCL11. No differences in inflammatory cell infiltration or cells expressing CXCR3 and CXCR7 which are the receptors of CXCL11 occurred because of CXCL11 deficiency in the congenic mice spleens. However, these mice lacked a distinct population of CD14(+) positive resident mononuclear cells that express intermediate levels of CXCR3 and CXCR7 in the liver. There were fewer microabscesses in the liver of CXCL11-deficient mice during the early stage of infection, which is consistent with their decreased ability to resist Lm. Our results, when taken together, show that the Listr1 locus plays an important role in early control of Lm infection in the mouse liver and that Cxcl11 is a candidate gene for disease severity within this locus.

International Union of Basic and Clinical Pharmacology. [corrected]. LXXXIX. Update on the extended family of chemokine receptors and introducing a new nomenclature for atypical chemokine receptors

Sixteen years ago, the Nomenclature Committee of the International Union of Pharmacology approved a system for naming human seven-transmembrane (7TM) G protein-coupled chemokine receptors, the large family of leukocyte chemoattractant receptors that regulates immune system development and function, in large part by mediating leukocyte trafficking. This was announced in Pharmacological Reviews in a major overview of the first decade of research in this field [Murphy PM, Baggiolini M, Charo IF, Hébert CA, Horuk R, Matsushima K, Miller LH, Oppenheim JJ, and Power CA (2000) Pharmacol Rev 52:145-176]. Since then, several new receptors have been discovered, and major advances have been made for the others in many areas, including structural biology, signal transduction mechanisms, biology, and pharmacology. New and diverse roles have been identified in infection, immunity, inflammation, development, cancer, and other areas. The first two drugs acting at chemokine receptors have been approved by the U.S. Food and Drug Administration (FDA), maraviroc targeting CCR5 in human immunodeficiency virus (HIV)/AIDS, and plerixafor targeting CXCR4 for stem cell mobilization for transplantation in cancer, and other candidates are now undergoing pivotal clinical trials for diverse disease indications. In addition, a subfamily of atypical chemokine receptors has emerged that may signal through arrestins instead of G proteins to act as chemokine scavengers, and many microbial and invertebrate G protein-coupled chemokine receptors and soluble chemokine-binding proteins have been described. Here, we review this extended family of chemokine receptors and chemokine-binding proteins at the basic, translational, and clinical levels, including an update on drug development. We also introduce a new nomenclature for atypical chemokine receptors with the stem ACKR (atypical chemokine receptor) approved by the Nomenclature Committee of the International Union of Pharmacology and the Human Genome Nomenclature Committee.

IP-10/CXCL10 and MIG/CXCL9 as novel markers for the diagnosis of lymphoma-associated hemophagocytic syndrome

Lymphoma-associated hemophagocytic syndrome (LAHS) is a serious disorder, and its early diagnosis and treatment with appropriate chemotherapy are very important. However, reliable markers for early diagnosis of LAHS have not been identified. We screened serum cytokines using a newly introduced assay system, cytometric bead array (CBA), and identified interferon-inducible protein 10 (IP-10)/CXCL10 and monokine induced by interferon gamma (MIG)/CXCL9 as useful markers. Serum concentrations of IP-10 and MIG at the time of LAHS diagnosis were greater than 500 and 5,000 pg/ml, respectively. The sensitivity and specificity for LAHS diagnosis were 100 and 95 %, respectively, when we set the above values as the cut-off levels. Serum levels of these two chemokines were already elevated at the time of admission and significantly decreased after successful treatment, indicating their usefulness for both the diagnosis and therapeutic outcomes for LAHS. IP-10 and MIG were also useful in distinguishing severe from moderate/mild LAHS, and B-cell-type LAHS from T-cell/natural killer cell-type LAHS. Furthermore, IP-10 and MIG were of use to distinguish LAHS from sepsis in patients with hematologic malignancies. Rapid measurement of IP-10 and MIG by CBA appeared to be important for early diagnosis and treatment of LAHS.

The Regulation of Immune Responses by DC Derived Type I IFN

Our immune system bears the tremendous task of mounting effective anti-microbial responses whilst maintaining immunoregulatory functions to avoid autoimmunity. In order to quickly respond to pathogens, Dendritic cells (DC) are armed with pattern recognition receptors (PRRs), allowing them to recognize highly conserved pathogen-associated molecular patterns (PAMPs) that are uniquely expressed by invading microbes. PRR activation can trigger DCs to release the pleiotropic cytokine, Type I interferons (IFN), which facilitates various biological functions in different immune cell types. In this review, we will discuss the classical PRR-induced Type I IFN response in DCs as well as describe a novel mechanism for Type I IFN induction by the tumor-necrosis factor receptor superfamily (TNFRSF) members, TNFR-1 and lymphotoxin-β receptor (LTβR). While PRR activation during viral infection, produces large amounts of Type I IFN in a relative short period of time, TNFRSF-induced Type I IFN expression is modest with gradual kinetics. Type I IFN can exert pro-inflammatory effects, but in some cases it also facilitates immune-regulatory functions. Therefore, DCs are important regulators of immune responses by carefully modulating Type I IFN expression.

Small molecule CXCR3 antagonist NIBR2130 has only a limited impact on type 1 diabetes in a virus-induced mouse model

CXCL10 is one of the key chemokines involved in trafficking of autoaggressive T cells to the islets of Langerhans during the autoimmune destruction of beta cells in type 1 diabetes (T1D). Blockade of CXCL10 or genetic deletion of its receptor CXCR3 results in a reduction of T1D in animal models. As an alternative to the use of neutralizing monoclonal antibodies to CXCL10 or CXCR3 we evaluated the small molecule CXCR3 antagonist NIBR2130 in a virus-induced mouse model for T1D. We found that the overall frequency of T1D was not reduced in mice administered with NIBR2130. An initial slight delay of diabetes onset was not stable over time, because the mice turned diabetic upon removal of the antagonist. Accordingly, no significant differences were found in the islet infiltration rate and the frequency and activity of islet antigen-specific T cells between protected mice administered with NIBR2130 and control mice. Our data indicate that in contrast to direct inhibition of CXCL10, blockade of CXCR3 with the small molecule antagonist NIBR2130 has no impact on trafficking and/or activation of autoaggressive T cells and is not sufficient to prevent T1D.

Interferons induce CXCR3-cognate chemokine production by human metastatic melanoma

Immune-mediated cancer regression requires tumor infiltration by antigen-specific effector T cells, but lymphocytes are commonly sparse in melanoma metastases. Activated T cells express CXCR3, whose cognate chemokines are CXCL9/MIG, CXCL10/IP-10, and CXCL11/I-TAC. Little is known about expression of these chemokines in lymph node (LN) metastases of melanoma. We evaluated whether metastatic melanoma induces these CXCR3-cognate chemokines in human LN-derived tissues. In addition, as these chemokines can be induced by interferon (IFN), we evaluated whether type I or II IFNs (IFN-α or IFN-γ, respectively) can modulate chemokine expression in an in vitro model of the human tumor microenvironment. Production of CXCL9-11 by melanoma-infiltrated nodes (MIN) was no different than tumor-free nodes; both produced less chemokine than activated LN (sentinel immunized nodes, SIN). These data suggest that melanoma infiltration into LN neither induces nor reduces CXCL9-11. Stimulation with IFN-α or IFN-γ increased production of CXCL10-11 from MIN, but not tumor-free node or SIN. IFN-γ also increased production of CXCL9 in MIN. In IFN-treated SIN, CD14+ cells were the primary source of CXCL9-11, whereas melanoma cells were the source of chemokine in MIN. Melanoma cells in MIN express IFN receptors. Consistent with these observations, multiple human melanoma lines expressed IFN receptors and produced CXCL9-11 in response to IFN treatment. Thus, melanoma infiltration of LN is insufficient to induce the production of CXCL9-11, but melanoma may be a significant source of IFN-induced chemokines. Collectively, these data suggest that IFN-α or IFN-γ may act in the tumor microenvironment to increase the chemotactic gradient for CXCR3+ T cells.

CXCR3 ligands: redundant, collaborative and antagonistic functions

CXCR3 is a chemokine receptor that is rapidly induced on naïve T cells following activation, and preferentially remains highly expressed on type-1 helper (Th1)-type CD4(+) T cells, effector CD8(+) T cells and innate-type lymphocytes, such as natural killer (NK) and NKT cells. CXCR3 is activated by three interferon (IFN)-γ-inducible ligands CXCL9 (monokine induced by gamma-interferon), CXCL10 (interferon-induced protein-10) and CXCL11 (interferon-inducible T-cell alpha chemoattractant). Although some studies have revealed that these ligands have redundant functions in vivo, other studies have demonstrated that the three CXCR3 ligands can also collaborate and even compete with each other. Differential regulation of the three ligands at specific times in defined anatomically restricted locations in vivo likely participates in the fine control of T-cell trafficking over the course of an immune response. Among the differences in regulation, CXCL10 is induced by a variety of innate stimuli that induce IFN-α/β as well as the adaptive immune cell cytokine IFN-γ, whereas CXCL9 induction is restricted to IFN-γ. In this review, we will discuss how the balance, timing and pattern of CXCR3 ligand expression appears to regulate the generation of effector T cells in the lymphoid compartment and subsequent migration into peripheral sites of Th1-type inflammation in which the CXCR3 ligands also then regulate the interactions and migratory behavior of effector T cells in an inflamed peripheral tissue.

Organization and promoter analysis of the zebrafish (Danio rerio) chemokine gene (CXC-64) promoter

Zebrafish CXC-64, a chemokine representing a superfamily of chemotactic cytokines present in fish, is involved in recruitment, activation, and response to inflammatory stimulation. We cloned and sequenced the genomic DNA of the zebrafish CXC-64 chemokine; it was most similar to CXCL11 from humans and CXCL10 from a catfish. The zebrafish CXC-64 gene is approximately 4.0 kb long and has a four-exon, three-intron structure common to the human CXCL11 gene. However, the promoter region includes a typical TATA box and multi-transcription factor-binding sequences. To understand the roles of lipopolysaccharide (LPS), poly I:poly C, and tumor necrosis factor (TNF)-alpha in regulating zebrafish CXC-64 expression, serial deletions were made in the promoter region of this clone. Different fragments of the zebrafish CXC-64 5'-flanking region were transfected into RAW264.7 (mouse macrophage; Abelson murine leukemia virus transformed) and zfl (zebrafish liver) cells and then treated with 0, 10, 50, 100, and 200 ng/ml LPS, poly I:poly C, or TNF-alpha. The results showed that the promoter activity presented dose-dependent effects in LPS-treated RAW264.7 cells, TNF-alpha-treated RAW264.7 cells, and LPS-treated zfl cells. These results reveal that the zebrafish CXC-64 chemokine gene promoter region can be induced by LPS in both human and fish cell lines, which suggests that it plays an important role in regulating LPS.

CXCR4 and CXCR7 regulate angiogenesis and CT26.WT tumor growth independent from SDF-1

Recent studies have shown that the chemokine stromal cell-derived factor (SDF)-1 and its receptor CXCR4 are involved in the metastatic process of colorectal cancer. The impact of SDF-1 on the stimulated metastatic growth during hepatectomy-associated liver regeneration is unknown. With the use of a heterotopic murine colon cancer model, we analyzed whether blockade of SDF-1 inhibits angiogenesis and extrahepatic growth of colorectal cancer after liver resection. Functional neutralization of SDF-1 by 1 mg/kg body weight anti-SDF-1 antibody only slightly delayed the initial tumor cell engraftment but also did not reduce the size of established extrahepatic tumors compared with controls. Tumor cell apoptosis was increased by anti-SDF-1 treatment only during the early 5-9-day period of tumor cell engraftment, but was found significantly decreased during the late phase of tumor growth. The initial delay of tumor cell engraftment was associated with an increase of tumor capillary density and microvascular permeability. This was associated with an increased vascular endothelial growth factor (VEGF) expression and an enhanced tumor cell invasion of the neighboring tissue. In contrast to the neutralization of SDF-1, blockade of the SDF-1 receptors CXCR4 and CXCR7 significantly reduced tumor capillary density and tumor growth. Thus, our study indicates that neutralization of SDF-1 after hepatectomy is not capable of inhibiting angiogenesis and growth of extrahepatic colorectal tumors, because it is counteracted by the compensatory actions through an alternative VEGF-dependent pathway.

I-TAC is a dominant chemokine in controlling skin intragraft inflammation via recruiting CXCR3+ cells into the graft

Chemokines play a critical role in the acute transplant rejection. In order to provide an overview of the chemokine expression during the course of acute allograft rejection, the intragraft expression profile of 11 chemokines representative of all four chemokine subfamilies was analyzed in a murine skin transplantation model of acute rejection. It was found that RANTES/CCL5, TARC/CCL17 and FKN/CX(3)CL1 were expressed at equivalent levels in iso- and allografts. However, the other eight chemokines expression was up-regulated to some extent in allograft compared with that in isograft. The levels of MIP-1alpha/CCL3, MIP-3alpha/CCL20 and CTACK/CCL27 were progressively increased from early stage (day 3 post-transplantation) to late stage (day 11). Mig/CXCL9, IP-10/CXCL10, I-TAC/CXCL11, CXCL16 and LTN/XCL1 expression was elevated at middle stage (day 7), and peaked at late stage. Among the up-regulated chemokines, I-TAC was the most obviously elevated chemokine. Therefore, the effect of I-TAC on the skin acute allograft rejection was evaluated. Block of I-TAC by the intradermal injection of anti-I-TAC monoclonal antibody (mAb) reduced the number of CXCR3(+) cells in skin allograft and significantly prolonged the skin allograft survival. The mAb treatment did not influence the proliferation of the intragraft infiltrating cells in response to the allogeneic antigens, but significantly decreased the number of the infiltrating cells and consequently lowered the secretion of IFN-gamma and TNF-alpha. These data indicate I-TAC might be a dominant chemokine involved in the intradermal infiltration and I-TAC-targeted intervening strategies would have potential application for the alleviation of acute transplant rejection.

The chemokine receptor Cxcr3 is not essential for acute cardiac allograft rejection in mice and rats

Chemokine receptors have gained attention as potential targets for novel therapeutic strategies. We investigated the mechanisms of allograft rejection in chemokine receptor Cxcr3-deficient mice using a model of acute heart allograft rejection in the strain combination BALB/c to C57BL/6. Allograft survival was minimally prolonged in Cxcr3-deficient mice compared to wild-type (wt) animals (8 vs. 7 days) and treatment with a subtherapeutic dose of cyclosporine A (CsA) led to similar survival in Cxcr3-deficient and wt recipients (13 vs. 12 days). At rejection grafts were histologically indistinguishable. Microarray analysis revealed that besides Cxcr3 only few genes were differentially expressed in grafts or in spleens from transplanted or untransplanted animals. Transcript analysis by quantitative RT-PCR of selected cytokines, chemokines, or chemokine receptors or serum levels of selected cytokines and chemokines showed similar levels between the two groups. Furthermore, in a rat heart allograft transplantation model treatment with a small molecule CXCR3 antagonist did not prolong survival despite full blockade of Cxcr3 in vivo. In summary, Cxcr3 deficiency or pharmacologic blockade does not diminish graft infiltration, tempo and severity of rejection. Thus, Cxcr3 does not appear to play a pivotal role in the allograft rejection models described here.

Granulocyte-macrophage colony-stimulating factor is required for bronchial eosinophilia in a murine model of allergic airway inflammation

GM-CSF plays an important role in inflammation by promoting the production, activation, and survival of granulocytes and macrophages. In this study, GM-CSF knockout (GM-CSF(-/-)) mice were used to investigate the role of GM-CSF in a model of allergic airway inflammation. In allergic GM-CSF(-/-) mice, eosinophil recruitment to the airways showed a striking pattern, with eosinophils present in perivascular areas, but almost completely absent in peribronchial areas, whereas in wild-type mice, eosinophil infiltration appeared in both areas. In the GM-CSF(-/-) mice, mucus production in the airways was also reduced, and eosinophil numbers were markedly reduced in the bronchoalveolar lavage (BAL)(3) fluid. IL-5 production was reduced in the lung tissue and BAL fluid of GM-CSF(-/-) mice, but IL-4 and IL-13 production, airway hyperresponsiveness, and serum IgE levels were not affected. The presence of eosinophils in perivascular but not peribronchial regions was suggestive of a cell migration defect in the airways of GM-CSF(-/-) mice. The CCR3 agonists CCL5 (RANTES) and CCL11 (eotaxin-1) were expressed at similar levels in GM-CSF(-/-) and wild-type mice. However, IFN-gamma mRNA and protein were increased in the lung tissue and BAL fluid in GM-CSF(-/-) mice, as were mRNA levels of the IFN-gamma-inducible chemokines CXCL9 (Mig), CXCL10 (IP-10), and CXCL11 (I-Tac). Interestingly, these IFN-gamma-inducible chemokines are natural antagonists of CCR3, suggesting that their overproduction in GM-CSF(-/-) mice contributes to the lack of airway eosinophils. These findings demonstrate distinctive abnormalities to a model of allergic asthma in the absence of GM-CSF.

Mesenchymal stem cell-mediated immunosuppression occurs via concerted action of chemokines and nitric oxide

Mesenchymal stem cells (MSCs) can become potently immunosuppressive through unknown mechanisms. We found that the immunosuppressive function of MSCs is elicited by IFNgamma and the concomitant presence of any of three other proinflammatory cytokines, TNFalpha, IL-1alpha, or IL-1beta. These cytokine combinations provoke the expression of high levels of several chemokines and inducible nitric oxide synthase (iNOS) by MSCs. Chemokines drive T cell migration into proximity with MSCs, where T cell responsiveness is suppressed by nitric oxide (NO). This cytokine-induced immunosuppression was absent in MSCs derived from iNOS(-/-) or IFNgammaR1(-/-) mice. Blockade of chemokine receptors also abolished the immunosuppression. Administration of wild-type MSCs, but not IFNgammaR1(-/-) or iNOS(-/-) MSCs, prevented graft-versus-host disease in mice, an effect reversed by anti-IFNgamma or iNOS inhibitors. Wild-type MSCs also inhibited delayed-type hypersensitivity, while iNOS(-/-) MSCs aggravated it. Therefore, proinflammatory cytokines are required to induce immunosuppression by MSCs through the concerted action of chemokines and NO.

Gene signatures reflect the marked heterogeneity of tissue-resident macrophages

Tissue-resident macrophages play an important role in defense against pathogens and perform key functions in organ homeostasis, innate and adaptive immunity. Tissue macrophages originate from blood monocytes that infiltrate virtually every organ in the body. Macrophages in different tissues share many characteristics, including their ability to migrate, phagocytose particles, metabolize lipids and present antigens. Morphologically they are quite heterogeneous, and some distinct functions have been reported. The gene expression profile of macrophages is reflective of both their shared and distinct biological functions. Here, we show that macrophages from murine spleen, liver and peritoneum display dramatically different expression profiles. Clusters of genes were found to represent unique biological functions related to adhesion, antigen presentation, phagocytosis, lipid metabolism and signal transduction. Some gene families, such as integrins, are differentially expressed among the macrophages resident in different tissues, suggesting that the tissue of residence influences their biological function.

Rat chemokine CXCL11: structure, tissue distribution, function and expression in cardiac transplantation models

CXCL11 is thought to play a critical role in allograft rejection. To clarify the role of CXCL11 in the rat transplantation model, we cloned CXCL11 cDNA from rat liver tissue and used it to study CXCL11 structure, function and expression. The rat CXCL11 gene encodes a protein of 100 amino acids and spans approximately a 2.8 kb DNA segment containing 4 exons in the protein coding region. Tissue distribution of rat CXCL11 was analyzed by quantitative RT-PCR and showed that rat CXCL11 mRNA is expressed in various tissues and, in particular, at high levels in the spleen and lymph nodes. COS-1 cells were transfected with a plasmid vector encoding rat CXCL11 and used to study CXCL11 effects on cell migration and internalization of CXCR3, the CXCL11 receptor. The recombinant CXCL11 showed chemotactic properties and induced CXCR3 internalization in CD4(+) T cells. Expression of CXCL11 mRNA also was measured in rat acute (ACI to LEW) and chronic (LEW to F344) heart transplant rejection models. CXCL11 mRNA expression in allografts increased in both models, compared with controls, and was primarily observed in infiltrating macrophages and donor endothelial cells. These results indicate that, like the other CXCR3 chemokines, rat CXCL11 seems to have a role in the homing of CD4(+) T cells in both acute and chronic rejection models of heart allotransplantation.

Vaccination with IFN-inducible T cell alpha chemoattractant (ITAC) gene-modified tumor cell attenuates disseminated metastases of circulating tumor cells

Immunotherapeutic strategies for metastatic diseases are being developed. IFN-inducible T cell alpha chemoattractant (ITAC) has been demonstrated to be able to induce Th1-type immune response. However, the effects of ITAC on the tumor metastasis have not been fully understood. In the present study, the ITAC-modified tumor cell vaccine in inhibiting the disseminated pulmonary metastasis was evaluated. ITAC-modified tumor cell vaccine 4T1-ITAC was developed by stably transfecting 4T1 cells with pcDNA3-ITAC plasmid. Mice were vaccinated with 4T1-ITAC. Mice vaccinated with 4T1-pcDNA3 and 4T1 were used as controls. Specific cellular immune responses against 4T1 were tested by in vitro proliferation, cytokine production and cytotoxic assay. The number of clonogenic metastatic tumor cells and metastatic forci on the surface of lung were counted by histological examination. Results showed that a significant enhancement of proliferative and cytotoxic activities accompanied with increased IFN-gamma and TNF-alpha production as well as decreased IL-4 production were obtained from the mice vaccinated with 4T1-ITAC. The number of clonogenic metastatic tumor cells in the mice vaccinated with 4T1-ITAC cells reduced markedly and no visible metastasis was found in the lungs of the 4T1-ITAC vaccinated mice. Consequently, the survival rate was dramatically increased in these mice. Taken together, our results demonstrated that ITAC-modified tumor cell vaccine can enhance the anti-tumor immunity and reduce the incidence of disseminated metastasis.

CXCR 3 activation promotes lymphocyte transendothelial migration across human hepatic endothelium under fluid flow

T cells infiltrating the inflamed liver express high levels of CXCR 3 and show enhanced migration to CXCR 3 ligands in chemotactic assays. Moreover, CXCR 3 ligands are up-regulated on hepatic endothelium at sites of T-cell infiltration in chronic hepatitis, and their presence correlates with outcome of inflammatory liver disease. We used a flow-based adhesion assay with human hepatic endothelium to investigate the function of CXCR 3 on lymphocyte adhesion to and transmigration through hepatic endothelium under physiological conditions of blood flow. To more accurately model the function of in vivo activated CXCR 3(high) lymphocytes, we isolated T cells from human liver tissue and studied their behavior in flow-based adhesion assays. We demonstrate that CXCR 3 not only promoted the adhesion of effector T cells to endothelium from flow but also drove transendothelial migration. Moreover, these responses could be stimulated either by endogenous CXCR 3 ligands secreted by the endothelium or by exogenous CXCR 3 ligands derived from other cell types and presented by the endothelium. This study thus demonstrates that activation of CXCR 3 promotes lymphocyte adhesion and transendothelial migration under flow and that human hepatic endothelium can present functionally active chemokines secreted by other cell types within the liver.

The CXCR3 targeting chemokine CXCL11 has potent antitumor activity in vivo involving attraction of CD8+ T lymphocytes but not inhibition of angiogenesis

The IFN-gamma-inducible and CXCR3-targeting human CXC chemokines CXCL9 (Mig) and CXCL10 (IP10) have potent antitumor activity through attraction of cytotoxic T lymphocytes and inhibition of angiogenesis. The more recently identified CXCR3-targeting chemokine CXCL11 (I-TAC/IP9) proved to be a more potent chemokine than CXCL9 and CXCL10 in vitro, both in chemotaxis assays with CXCR3+ T lymphocytes and in calcium mobilization experiments. However, its antitumor activity in vivo has not been shown so far. To investigate this, mice were challenged with EL4 T-cell lymphoma cells, genetically modified to produce murine CXCL11. Tumor growth curves showed complete rejection of CXCL11-producing tumors but not of control tumors. Tumor infiltrate analysis by flow cytometry showed a clear correlation between rejection of CXCL11-producing tumors and an increase of tumor-infiltrating CD8+CXCR3+ as well as CD8+CXCR3- T lymphocytes. In vivo CD8 T-cell depletion completely abrogated the antitumor effect. No difference in angiogenesis between control and CXCL11-producing tumors was observed. In survivors, rechallenge experiments with wild-type tumor cells suggested development of protective antitumor immunity involving tumor-specific IFN-gamma production by CD8+ T lymphocytes. These experiments show, for the first time, antitumor activity of CXCL11 in vivo, which warrants exploration for its potential role in anticancer immunotherapy.

NMR structure of CXCR3 binding chemokine CXCL11 (ITAC)

CXCL11 (ITAC) is one of three chemokines known to bind the receptor CXCR3, the two others being CXCL9 (Mig) and CXCL10 (IP-10). CXCL11 differs from the other CXCR3 ligands in both the strength and the particularities of its receptor interactions: It has a higher affinity, is a stronger agonist, and behaves differently when critical N-terminal residues are deleted. The structure of CXCL11 was determined using solution NMR to allow comparison with that of CXCL10 and help elucidate the source of the differences. CXCL11 takes on the canonical chemokine fold but exhibits greater conformational flexibility than has been observed for related chemokines under the same sample conditions. Unlike related chemokines such as IP-10 and IL-8, ITAC does not appear to form dimers at millimolar concentrations. The origin for this behavior can be found in the solution structure, which indicates a beta-bulge in beta-strand 1 that distorts the dimerization interface used by other CXC chemokines.

CXCR3 and its ligands participate in the host response to Bordetella bronchiseptica infection of the mouse respiratory tract but are not required for clearance of bacteria from the lung

Intranasal inoculation of mice with Bordetella bronchiseptica produces a transient pneumonia that is cleared over several weeks in a process known to require both neutrophils and lymphocytes. In this study, we evaluated the roles of the chemokines MIG (CXCL9), IP-10 (CXCL10), and I-TAC (CXCL11) and their common receptor, CXCR3. Following bacterial inoculation, message expression of interleukin-1 (IL-1), IL-6, and the neutrophil-attracting chemokines KC, LIX, and MIP-2 was rapidly induced, with maximal expression found at 6 h. In contrast, message expression of gamma interferon, MIG, IP-10, and I-TAC peaked at 2 days. Expression of all of these chemokines and cytokines returned to near baseline by 5 days, despite the persistence of high levels of live bacteria at this time. Induced MIG, IP-10, and I-TAC protein expression was localized in areas of inflammation at 2 to 3 days and was temporally associated with increased levels of CXCR3(+) lymphocytes in bronchoalveolar lavage fluid. There was no increase in mortality in mice lacking CXCR3. However, the clearance of bacteria from the lung and trachea was delayed, and the recruitment of lymphocytes and NK cells was slightly decreased, for CXCR3(-/-) mice relative to CXCR3(+/+) mice. We conclude that the CXCR3 receptor-ligand system contributes to pulmonary host defense in B. bronchiseptica infection by recruiting lymphocytes and NK cells into the lung.

CXC Chemokine Ligand 10 Neutralization Suppresses the Occurrence of Diabetes in Nonobese Diabetic Mice through Enhanced β Cell Proliferation without Affecting Insulitis

We have shown that neutralization of IFN-inducible protein 10/CXCL10, a chemokine for Th1 cells, breaks Th1 retention in the draining lymph nodes, resulting in exacerbation in Th1-dominant autoimmune disease models induced by immunization with external Ags. However, there have been no studies on the role of CXCL10 neutralization in Th1-dominant disease models induced by constitutive intrinsic self Ags. So, we have examined the effect of CXCL10 neutralization using a type 1 diabetes model initiated by developmentally regulated presentation of beta cell Ags. CXCL10 neutralization suppressed the occurrence of diabetes after administration with cyclophosphamide in NOD mice, although CXCL10 neutralization did not significantly inhibit insulitis and gave no influence on the trafficking of effector T cells into the islets. Because both CXCL10 and CXCR3 were, unexpectedly, coexpressed on insulin-producing cells, CXCL10 was considered to affect mature and premature beta cells in an autocrine and/or paracrine fashion. In fact, CXCL10 neutralization enhanced proliferative response of beta cells and resultantly increased beta cell mass without inhibiting insulitis. Thus, CXCL10 neutralization can be a new therapeutic target for beta cell survival, not only during the early stage of type 1 diabetes, but also after islet transplantation.

Rabies virus stimulates nitric oxide production and CXC chemokine ligand 10 expression in macrophages through activation of extracellular signal-regulated kinases 1 and 2

Macrophages represent an essential part of innate immunity, and the viral infection of macrophages results in the release of multiple proinflammatory mediators, such as nitric oxide (NO), cytokines, and chemokines. This study was undertaken to define the molecular mechanism of macrophage activation in response to rabies virus (RV) infection. In RAW264 murine macrophage cells, a well-characterized macrophage model, RV replication was strictly restricted, whereas cell proliferation was significantly enhanced upon RV inoculation. Transcriptional analyses for the expression of inducible forms of NO synthase (iNOS), cytokines, and chemokines revealed that RV virions potentiate the gene expression of iNOS and CXC chemokine ligand 10 (CXCL10), a major chemoattractant of T helper cell type 1. However, RV stimulation had little or no effect on the expression profiles of proinflammatory cytokines and other types of chemokines. In macrophages stimulated with UV-inactivated RV virions, as well as infectious viruses, the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, members of the mitogen-activated protein kinase family, was significantly induced. Specific inhibitors of MAPK/ERK kinase reduced the RV-induced production of NO and CXCL10. Furthermore, the RV-induced activation of the ERK1/2 pathway was severely impaired by the neutralization of the endosomal and lysosomal pH environment with lysosomotropic agents, indicating that endocytosis is a key step leading to the activation of ERK1/2 signaling. Taken together, these results suggest that the ERK1/2-mediated signaling pathway plays a cardinal role in the selective activation of macrophages in response to RV virions, thereby regulating cellular functions during virus infection.

Innate immune discrimination of apoptotic cells: repression of proinflammatory macrophage transcription is coupled directly to specific recognition

Physiological cell death is a process the purpose of which is the elimination of functionally inappropriate cells in a manner that does not elicit an inflammatory response. We have shown previously that the ability of apoptotic corpses to be recognized by macrophages and to modulate the proinflammatory responses of those cells represents paradoxically a gain-of-function acquired during the physiological cell death process. Cells that die pathologically (that is, necrotic vs apoptotic corpses) also are recognized by macrophages but do not down-regulate macrophage inflammatory responses; the recognition of these two classes of native dying cells occurs via distinct and noncompeting mechanisms. We have examined the apoptotic modulation of proinflammatory cytokine gene transcription in macrophages (by real-time RT-PCR analysis) and the corresponding modulation of transcriptional activators (by transcriptional reporter analyses). Our data demonstrate that apoptotic cells target the proinflammatory transcriptional machinery of macrophages with which they interact, without apparent effect on proximal steps of Toll-like receptor signaling. The modulatory activity of the corpse is manifest as an immediate-early inhibition of proinflammatory cytokine gene transcription, and is exerted directly upon binding to the macrophage, independent of subsequent engulfment and soluble factor involvement. Recognition and inflammatory modulation represent key elements of an innate immune response that discriminates live from effete cells, and without regard to self.

Furin is a chemokine-modifying enzyme: in vitro and in vivo processing of CXCL10 generates a C-terminally truncated chemokine retaining full activity

Chemokines comprise a class of structurally related proteins that are involved in many aspects of leukocyte migration under basal and inflammatory conditions. In addition to the large number of genes, limited processing of these proteins by a variety of enzymes enhances the complexity of the total spectrum of chemokine variants. We have recently shown that the native chemokine CXCL10 is processed at the C terminus, thereby shedding the last four amino acids. The present study was performed to elucidate the mechanism in vivo and in vitro and to study the biological activity of this novel isoform of CXCL10. Using a combination of protein purification and mass spectrometric techniques, we show that the production of C-terminally truncated CXCL10 by primary keratinocytes is inhibited in vivo by a specific inhibitor of pro-protein convertases (e.g. furin) but not by inhibition of matrix metalloproteinases. Moreover, CXCL10 is processed by furin in vitro, which is abrogated by a mutation in the furin recognition site. Using GTPgammaS binding, Ca(2+) mobilization, and chemotaxis assays, we demonstrate that the C-terminally truncated CXCL10 variant is a potent ligand for CXCR3. Moreover, the inverse agonist activity on the virally encoded receptor ORF74 and the direct antibacterial activity of CXCL10 are fully retained. Hence, we have identified furin as a novel chemokine-modifying enzyme in vitro and most probably also in vivo, generating a C-terminally truncated CXCL10, which fully retains its (inverse) agonistic properties.

Viral IL-10 gene transfer inhibits the expression of multiple chemokine and chemokine receptor genes induced by inflammatory or adaptive immune stimuli

Previously we have shown that adenovirus-mediated gene transfer and expression of vIL-10 are able to prolong cardiac allograft survival, through the inhibition of the immune response to both alloantigen and adenoviral antigens. In the current study, we have defined further mechanisms of Ad.vIL-10-mediated prolongation of cardiac allograft survival. E1- and E3-deleted adenoviral vectors encoding beta-galactosidase or vIL-10 were transferred into grafts at the time of transplantation, chemokine and chemokine receptor expression were evaluated by a pathway-specific cDNA array, and the results were confirmed with real time RT-PCR on selected genes. Ischemic injury, alloantigen and adenovirus vector induced the expression of multiple pro-inflammatory chemokines in the grafts, which likely amplify allograft rejection. Most of these Th1-related chemokine genes were inhibited or down-regulated by Ad.vIL-10 administration, which may help to decrease leukocytic infiltration and improve graft survival. Among the potent Th1 type chemokines inhibited were the CXCR3 ligands CXCL9 and CXCL10, which could directly inhibit vector-mediated gene expression in myoblasts, although targeting CXCR3 or its ligands did not prolong allograft survival with vIL-10 gene transfer. Ad.vIL-10 administration also induced the expression of the Th2-associated chemokines eotaxin-2 and MIP-1 gamma, suggesting Th1 to Th2 immune deviation. These results demonstrated that the vIL-10 gene transfer inhibits chemokine expression, preventing stimulation of innate and adaptive immunity.

Differential chemokine and chemokine receptor gene induction by ischemia, alloantigen, and gene transfer in cardiac grafts

Transplantation of allogeneic grafts presents several challenges to the innate and adaptive immune systems including chemokine leukocyte recruitment, activation, and effector function. We defined the chemokines and receptors induced by the transplant procedure/ischemia injury, alloantigen and gene transfer vector administration in murine cardiac grafts. E1, E3 deleted AdRSVbetagal was transferred into grafts at the time of transplantation, grafts were harvested after 1-14 days, and a pathway-specific cDNA array was used to evaluate the levels of 67 chemokine and chemokine receptor genes. Transplantation resulted in ischemic injury and induction of a number of similar genes in both the syngeneic and allogeneic grafts, such as CXCL1 and CXCL5, which increased dramatically on day 1 and returned rapidly to baseline in the syngeneic grafts. Alloantigen stimulated the adaptive immune response and induced the presence of more inflammatory genes within the grafts, particularly at later time points. The adenovirus vector induced a broader panel of genes, among them potent inflammatory chemokines CXCL9 and CXCL10, that are induced earlier or more strongly compared with alloantigen stimulation alone. As alloantigen and adenovirus vectors both induce similar sets of genes, targeting these molecules may not only inhibit alloimmunity, but also enhance the utility of the gene transfer vector.

Peptide nucleic acid antisense prolongs skin allograft survival by means of blockade of CXCR3 expression directing T cells into graft

CXCR3, predominantly expressed on memory/activated T cells, is a receptor for both IFN-gamma-inducible protein 10/CXC chemokine ligand (CXCL)10 and monokine induced by IFN-gamma/CXCL9. It was reported that CXC chemokines IFN-gamma-inducible protein 10/CXCL10 and monokine induced by IFN-gamma/CXCL9 play a critical role in the allograft rejection. We report that CXCR3 is a dominant factor directing T cells into mouse skin allograft, and that peptide nucleic acid (PNA) CXCR3 antisense significantly prolongs skin allograft survival by means of blockade of CXCR3 expression directing T cells into allografts in mice. We found that CXCR3 is highly up-regulated in spleen T cells and allografts from BALB/c recipients by day 7 of receiving transplantation, whereas CCR5 expression is moderately increased. We designed PNA CCR5 and PNA CXCR3 antisenses, and i.v. treated mice that received skin allograft transplantations. The PNA CXCR3 at a dosage of 10 mg/kg/day significantly prolonged mouse skin allograft survival (17.1 +/- 2.4 days) compared with physiological saline treatment (7.5 +/- 0.7 days), whereas PNA CCR5 (10 mg/kg/day) marginally prolonged skin allograft survival (10.7 +/- 1.1 days). The mechanism of prolongation of skin allograft survival is that PNA CXCR3 directly blocks the CXCR3 expression in T cells, which is responsible for directing T cells into skin allograft to induce acute rejection, without interfering with other functions of the T cells. These results were obtained at mRNA and protein levels by flow cytometry and real-time quantitative RT-PCR technique, and confirmed by chemotaxis, Northern and Western blot assays, and histological evaluation of skin grafts. The present study indicates the therapeutic potential of PNA CXCR3 to prevent acute transplantation rejection.

Endothelial injury: cause and effect of alloimmune inflammation

This review discusses the concept that endothelial cells may facilitate inflammation, but are also targets of the inflammatory response. Endothelial cells express several molecules that promote leukocyte recruitment, and other molecules, such as MHC class I that enable endothelial injury. Circulating alloantibodies produced following transplantation may also target the endothelium for injury. It has been shown that the expression of select protective genes within endothelial cells, including anti-apoptotic genes, may provide resistance to immune-mediated injury. Thus, an understanding of the mechanisms by which endothelial cells are injured and by which endothelial cells are protected is important for our understanding of allograft rejection.

The CXCR3 binding chemokine IP-10/CXCL10: structure and receptor interactions

The structure of IP-10 was solved by NMR spectroscopy and represents the first structure from the class of agonists toward the receptor CXCR3. CXCR3 binding chemokines are unique in their ability to bind receptors from both the CC and CXC classes of chemokine receptors. An unusual structural feature of IP-10 was identified that may provide the basis for the ability of IP-10 to bind both CXCR3 and CCR3. The surface of IP-10 that interacts with the N-terminus of CXCR3 was defined by monitoring changes in the NMR spectrum of IP-10 upon addition of a CXCR3 N-terminal peptide. These studies indicated that the interaction involves a hydrophobic cleft, formed by the N-loop and 40s-loop region of IP-10, similar to the interaction surface observed for other chemokines such as IL-8. An additional region of interaction was observed that consists of a hydrophobic cleft formed by the N-terminus of IP-10 and 30s-loop of IP-10.

Processing of natural and recombinant CXCR3-targeting chemokines and implications for biological activity

Chemokines comprise a class of peptides with chemotactic activity towards leukocytes. The potency of different chemokines for the same receptor often varies as a result of differences in primary structure. In addition, post-translational modifications have been shown to affect the effectiveness of chemokines. Although in several studies, natural CXCR3-targeting chemokines have been isolated, detailed information about the proteins and their possible modifications is lacking. Using a combination of liquid chromatography and mass spectrometry we studied the protein profile of CXCR3-targeting chemokines expressed by interferon-gamma-stimulated human keratinocytes. The biological implications of one of the identified modifications was studied in more detail using calcium mobilization and chemotaxis assays. We found that the primary structure of human CXCL10 is different from the generally accepted sequence. In addition we identified a C-terminally truncated CXCL10, lacking the last four amino acids. Native CXCL11 was primarily found in its intact mature form but we also found a mass corresponding to an N-terminally truncated human CXCL11, lacking the first two amino acids FP, indicating that this chemokine is a substrate for dipeptidylpeptidase IV. Interestingly, this same truncation was found when we expressed human CXCL11 in Drosophila S2 cells. The biological activity of this truncated form of CXCL11 was greatly reduced, both in calcium mobilization (using CXCR3 expressing CHO cells) as well as its chemotactic activity for CXCR3-expressing T-cells. It is concluded that detailed information on chemokines at the protein level is important to characterize the exact profile of these chemotactic peptides as modifications can severely alter their biological activity.