Association of the CXCL9-CXCR3 and CXCL13-CXCR5 axes with B-cell trafficking in giant cell arteritis and polymyalgia rheumatica.

OBJECTIVE: B-cells are present in the inflamed arteries of giant cell arteritis (GCA) patients and a disturbed B-cell homeostasis is reported in peripheral blood of both GCA and the overlapping disease polymyalgia rheumatica (PMR). In this study, we aimed to investigate chemokine-chemokine receptor axes governing the migration of B-cells in GCA and PMR. METHODS: We performed Luminex screening assay for serum levels of B-cell related chemokines in treatment-naïve GCA (n = 41), PMR (n = 31) and age- and sex matched healthy controls (HC, n = 34). Expression of chemokine receptors on circulating B-cell subsets were investigated by flow cytometry. Immunohistochemistry was performed on GCA temporal artery (n = 14) and aorta (n = 10) and on atherosclerosis aorta (n = 10) tissue. RESULTS: The chemokines CXCL9 and CXCL13 were significantly increased in the circulation of treatment-naïve GCA and PMR patients. CXCL13 increased even further after three months of glucocorticoid treatment. At baseline CXCL13 correlated with disease activity markers. Peripheral CXCR3+ and CXCR5+ switched memory B-cells were significantly reduced in both patient groups and correlated inversely with their complementary chemokines CXCL9 and CXCL13. At the arterial lesions in GCA, CXCR3+ and CXCR5+ B-cells were observed in areas with high CXCL9 and CXCL13 expression. CONCLUSION: Changes in systemic and local chemokine and chemokine receptor pathways related to B-cell migration were observed in GCA and PMR mainly in the CXCL9-CXCR3 and CXCL13-CXCR5 axes. These changes can contribute to homing and organization of B-cells in the vessel wall and provide further evidence for an active involvement of B-cells in GCA and PMR.

Type 1 helper T cells generate CXCL9/10-producing T-bet+ effector B cells potentially involved in the pathogenesis of rheumatoid arthritis.

Efficacy of B-cell depletion therapy highlights the antibody-independent effector functions of B cells in rheumatoid arthritis (RA). Given type 1 helper T (Th1) cells abundant in synovial fluid (SF) of RA, we have determined whether Th1 cells could generate novel effector B cells. Microarray and qPCR analysis identified CXCL9/10 transcripts as highly expressed genes upon BCR/CD40/IFN-γ stimulation. Activated Th1 cells promoted the generation of CXCL9/10-producing T-bet+ B cells. Expression of CXCL9/10 was most pronounced in CXCR3+ switched memory B cells. Compared with peripheral blood, SFRA enriched highly activated Th1 cells that coexisted with abundant CXCL9/10-producing T-bet+ B cells. Intriguingly, anti-IFN-γ antibody and JAK inhibitors significantly abrogated the generation of CXCL9/10-producing T-bet+ B cells. B cell derived CXCL9/10 significantly facilitated the migration of CD4+ T cells. These findings suggest that Th1 cells generate the novel CXCL9/10-producing T-bet+ effector B cells that could be an ideal pathogenic B cell target for RA therapy.

The CC and CXC chemokines: major regulators of tumor progression and the tumor microenvironment.

Chemokines are a family of soluble cytokines that act as chemoattractants to guide the migration of cells, in particular of immune cells. However, chemokines are also involved in cell proliferation, differentiation, and survival. Chemokines are associated with a variety of human diseases including chronic inflammation, immune dysfunction, cancer, and metastasis. This review discusses the expression of CC and CXC chemokines in the tumor microenvironment and their supportive and inhibitory roles in tumor progression, angiogenesis, metastasis, and tumor immunity. We also specially focus on the diverse roles of CXC chemokines (CXCL9-11, CXCL4 and its variant CXCL4L1) and their two chemokine receptor CXCR3 isoforms, CXCR3-A and CXCR3-B. These two distinct isoforms have divergent roles in tumors, either promoting (CXCR3-A) or inhibiting (CXCR3-B) tumor progression. Their effects are mediated not only directly in tumor cells but also indirectly via the regulation of angiogenesis and tumor immunity. A full comprehension of their mechanisms of action is critical to further validate these chemokines and their receptors as biomarkers or therapeutic targets in cancer.

Keratinocyte-Derived Chemokines Orchestrate T-Cell Positioning in the Epidermis during Vitiligo and May Serve as Biomarkers of Disease.

Vitiligo is an autoimmune disease of the skin that results in the destruction of melanocytes and the clinical appearance of white spots. Disease pathogenesis depends on IFN-γ and IFN-γ-induced chemokines to promote T-cell recruitment to the epidermis where melanocytes reside. The skin is a complex organ, with a variety of resident cell types. We sought to better define the microenvironment and distinct cellular contributions during autoimmunity in vitiligo, and we found that the epidermis is a chemokine-high niche in both a mouse model and human vitiligo. Analysis of chemokine expression in mouse skin showed that CXCL9 and CXCL10 expression strongly correlate with disease activity, whereas CXCL10 alone correlates with severity, supporting them as potential biomarkers for following disease progression. Further studies in both our mouse model and human patients showed that keratinocytes were the major chemokine producers throughout the course of disease, and functional studies using a conditional signal transducer and activator of transcription (STAT)-1 knockout mouse showed that IFN-γ signaling in keratinocytes was critical for disease progression and proper autoreactive T-cell homing to the epidermis. In contrast, epidermal immune cell populations including endogenous T cells, Langerhans cells, and γδ T cells were not required. These results have important clinical implications, because topical therapies that target IFN-γ signaling in keratinocytes could be safe and effective new treatments, and skin expression of these chemokines could be used to monitor disease activity and treatment responses.

Osteoblasts secrete Cxcl9 to regulate angiogenesis in bone.

Communication between osteoblasts and endothelial cells (ECs) is essential for bone turnover, but the molecular mechanisms of such communication are not well defined. Here we identify Cxcl9 as an angiostatic factor secreted by osteoblasts in the bone marrow microenvironment. We show that Cxcl9 produced by osteoblasts interacts with vascular endothelial growth factor and prevents its binding to ECs and osteoblasts, thus abrogating angiogenesis and osteogenesis both in mouse bone and in vitro. The mechanistic target of rapamycin complex 1 activates Cxcl9 expression by transcriptional upregulation of STAT1 and increases binding of STAT1 to the Cxcl9 promoter in osteoblasts. These findings reveal the essential role of osteoblast-produced Cxcl9 in angiogenesis and osteogenesis in bone, and Cxcl9 can be targeted to elevate bone angiogenesis and prevent bone loss-related diseases.

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.

CXCL9 and CXCL10 predict survival and are regulated by cyclooxygenase inhibition in advanced serous ovarian cancer.

BACKGROUND: Tumour-infiltrating lymphocytes (TILs) are associated with improved survival in several epithelial cancers. The two chemokines CXCL9 and CXCL10 facilitate chemotactic recruitment of TILs, and their intratumoral accumulation is a conceivable way to improve TIL-dependent immune intervention in cancer. However, the prognostic impact of CXCL9 and CXCL10 in high-grade serous ovarian cancer (HGSC) is largely unknown. METHODS: One hundred and eighty four cases of HGSC were immunohistochemically analyzed for CXCL9, CXCL10. TILs were assessed using CD3, CD56 and FOXP3 staining. Chemokine regulation was investigated using the ovarian cancer cell lines OV-MZ-6 and SKOV-3. RESULTS: High expression of CXCL9 and CXCL10 was associated with an approximately doubled overall survival (n=70, CXCL9: HR 0.41; P=0.006; CXCL10: HR 0.46; P=0.010) which was confirmed in an independent validation set (n=114; CXCL9: HR 0.60; P=0.019; CXCL10: HR 0.52; P=0.005). Expression of CXCR3 ligands significantly correlated with TILs. In human ovarian cancer cell lines the cyclooxygenase (COX) metabolite Prostaglandin E2 was identified as negative regulator of chemokine secretion, whereas COX inhibition by indomethacin significantly upregulated CXCL9 and CXCL10. In contrast, celecoxib, the only COX inhibitor prospectively evaluated for therapy of ovarian cancer, suppressed NF-κB activation and inhibited chemokine release. CONCLUSION: Our results support the notion that CXCL9 and CXCL10 exert tumour-suppressive function by TIL recruitment in human ovarian cancer. COX inhibition by indomethacin, not by celecoxib, may be a promising approach to concomitantly improve immunotherapies.

Blocking CXCL9 Decreases HIV-1 Replication and Enhances the Activity of Prophylactic Antiretrovirals in Human Cervical Tissues.

OBJECTIVES: The interferon-gamma-induced chemokine CXCL9 is expressed in a wide range of inflammatory conditions including those affecting the female genital tract. CXCL9 promotes immune cell recruitment, activation, and proliferation. The role of CXCL9 in modulating HIV-1 infection of cervicovaginal tissues, a main portal of viral entry, however, has not been established. We report a link between CXCL9 and HIV-1 replication in human cervical tissues and propose CXCL9 as a potential target to enhance the anti-HIV-1 activity of prophylactic antiretrovirals. DESIGN: Using ex vivo infection of human cervical tissues as a model of mucosal HIV-1 acquisition, we described the effect of CXCL9 neutralization on HIV-1 gene expression and mucosal CD4 T-cell activation. The anti-HIV-1 activity of tenofovir, the leading mucosal pre-exposure prophylactic microbicide, alone or in combination with CXCL9 neutralization was also studied. METHODS: HIV-1 replication was evaluated by p24 ELISA. HIV-1 DNA and RNA, and CD4, CCR5, and CD38 transcription were evaluated by quantitative real-time polymerase chain reaction. Frequency of activated cervical CD4 T cells was quantified using fluorescence-activated cell sorting. RESULTS: Antibody blocking of CXCL9 reduced HIV-1 replication by decreasing mucosal CD4 T-cell activation. CXCL9 neutralization in combination with suboptimal concentrations of tenofovir, possibly present in the cervicovaginal tissues of women using the drug inconsistently, demonstrated an earlier and greater decrease in HIV-1 replication compared with tissues treated with tenofovir alone. CONCLUSIONS: CXCL9 neutralization reduces HIV-1 replication and may be an effective target to enhance the efficacy of prophylactic antiretrovirals.

CXCR3 blockade protects against Listeria monocytogenes infection-induced fetal wastage.

Mammalian pregnancy requires protection against immunological rejection of the developing fetus bearing discordant paternal antigens. Immune evasion in this developmental context entails silenced expression of chemoattractant proteins (chemokines), thereby preventing harmful immune cells from penetrating the maternal-fetal interface. Here, we demonstrate that fetal wastage triggered by prenatal Listeria monocytogenes infection is driven by placental recruitment of CXCL9-producing inflammatory neutrophils and macrophages that promote infiltration of fetal-specific T cells into the decidua. Maternal CD8+ T cells with fetal specificity upregulated expression of the chemokine receptor CXCR3 and, together with neutrophils and macrophages, were essential for L. monocytogenes-induced fetal resorption. Conversely, decidual accumulation of maternal T cells with fetal specificity and fetal wastage were extinguished by CXCR3 blockade or in CXCR3-deficient mice. Remarkably, protection against fetal wastage and in utero L. monocytogenes invasion was maintained even when CXCR3 neutralization was initiated after infection, and this protective effect extended to fetal resorption triggered by partial ablation of immune-suppressive maternal Tregs, which expand during pregnancy to sustain fetal tolerance. Together, our results indicate that functionally overriding chemokine silencing at the maternal-fetal interface promotes the pathogenesis of prenatal infection and suggest that therapeutically reinforcing this pathway represents a universal approach for mitigating immune-mediated pregnancy complications.

The effect of CXCL9 on the invasion ability of hepatocellular carcinoma through up-regulation of PREX2.

Elevated expression of CXCL9 has been shown to involve in the infiltration of inflammatory cells and liver damage after Hepatitis B virus (HBV) infection. However, whether and by what underlying mechanism does CXCL9 play a role in HBV infection associated hepatocellular carcinoma (HCC) invasion ability remain unclear. In this study, human HCC as well as adjacent noncancerous tissues, together with three kinds of liver cancer cell lines were investigated to clarify the possible involvement of CXCL9 in the regulation of HCC invasion and metastasis. Invasion ability of liver cancer cells were evaluated by transwell assays and it is enhanced after co-cultured with recombined human CXCL9 (rhCXCL9). As a trigger of Rac GTPase signaling after G protein-coupled receptors (GPCR) activated by CXCL9, Phosphatidylinositol-3, 4, 5-trisphosphate RAC Exchanger 2 (PREX2) mRNA expression of the liver cancer cell lines was elevated after co-cultured with rhCXCL9. Moreover, the mRNA level of PREX2 in HCC tissues was significantly higher than those in adjacent noncancerous tissues. Besides, the mRNA levels of PREX2 were positively correlated with the poor differentiation, portal vein invasion, metastasis and qualitative HbsAg results in 45 pairs of HCC specimens. Similarly, PREX2 mRNA was higher in three liver cancer cell lines when compared with the normal liver cell line whereas knocked down of PREX2 by small interference RNA (PREX2-siRNA) reduced the invasion ability of liver cancer cells in transwell assays. Overall, our results suggested CXCL9 was involved in the invasion ability of HCC possibly through up-regulation of its potential effector PREX2.

Chemokine-mediated tissue recruitment of CXCR3+ CD4+ T cells plays a major role in the pathogenesis of chronic GVHD.

Chemokines regulate the migration of hemopoietic cells and play an important role in the pathogenesis of many immune-mediated diseases. Intradermal recruitment of CD8(+) T cells by CXCL10 is a central feature of the pathogenesis of cutaneous acute GVHD (aGVHD), but very little is known about the pathogenesis of chronic GVHD (cGVHD). Serum concentrations of the 3 CXCR3-binding chemokines, CXCL9, CXCL10, and CXCL11, were found to be markedly increased in patients with active cGVHD of the skin (n = 8). An 80% decrease in CD4(+) cells expressing CXCR3 was seen in the blood of these patients (n = 5), whereas CD4(+) cells were increased in tissue biopsies and were clustered around the central arterioles of the dermis. The well-documented increase in expression of CXCL10 in aGVHD therefore diversifies in cGVHD to include additional members of the CXCR3-binding family and leads to preferential recruitment of CD4(+) T cells. These observations reveal a central role for chemokine-mediated recruitment of CXCR3(+) T cells in cGVHD.

Intragraft transcriptome level of CXCL9 as biomarker of acute cellular rejection after liver transplantation.

BACKGROUND: Liver transplantation has been a life-saving and well-established treatment for acute liver failure and various end-stage liver diseases. However, acute cellular rejection (ACR) is one of the key factors that determine long-term graft function and survival after liver transplantation, and there are still no specific biomarkers available to monitor the alloimmune response. The aim of the present study was to identify molecular biomarkers for ACR in liver allograft. METHODS: We analyzed the gene expression profile using an oligonucleotide microarray covering 44,000 human probes in 35 liver biopsy samples after living donor liver transplant, which consisted of 13 samples with ACR (ACR group; moderate/mild, 6/7), 13 samples with other dysfunctions (non-ACR group; recurrent hepatitis C / ischemia/reperfusion injury (IRI)/ nonspecific inflammation / small-for-size syndrome, 5/4/3/1), and 9 samples without liver dysfunction (protocol group). We selected 113 informative genes based on microarray results and adopted the network analysis to visualize key modulators in ACR. We selected 6 modulators (CXCL9, GZMB, CCL19, GBP2, LAIR1, and CDC25A) and confirmed the reproducibility in 23 independent biopsy samples and investigated the response to the rejection treatment in sequential samples. RESULTS: Network analysis revealed the top three subnetworks, which had NF-κB, MAPK, and IFNG as central hubs. Among selected modulators, intragraft expression levels of CXCL9 mRNA was most upregulated and sensitive to alloimmune status. CONCLUSION: Intragraft CXCL9 mRNA has a functionally important role in T-cell activation in liver allograft and serves as biomarker for ACR.

The emerging role of CXC chemokines in epithelial ovarian cancer.

In recent years, chemokines have generated intense investigations due to their involvement in both physiological and pathological processes of inflammation, particularly in ovarian biology. The physiological process of ovulation in the normal ovary involves various chemokines that mediate the healing of the ruptured endometrium. It is now being reported that many of these chemokines are also associated with the cancer of the ovary. Chronic inflammation underlies the progression of ovarian cancer; therefore, it raises the possibility that chemokines are involved in the inflammatory process and mediate immune responses that may favour or inhibit tumour progression. Ovarian cancer is a gynaecological cancer responsible for highest rate of mortality in women. Although there have been several investigations and advances in surgery and chemotherapy, the survival rate for this disease remains low. This is mainly because of a lack of specific symptoms and biomarkers for detection. In this review, we have discussed the emerging role of the CXC chemokines in epithelial ovarian cancer (EOC). The CXC group of chemokines is gaining importance in the field of ovarian cancer for being angiostatic and angiogenic in function. While there have been several studies on the angiogenesis function, emerging research shows that ELR(-) CXC chemokines, CXCL9 and CXCL10, are angiostatic. Importantly, the angiostatic chemokines can inhibit the progression of EOC. Given that there are currently no biomarkers or specific therapeutic targets for the disease, these chemokines are emerging as promising targets for therapy.

Chemotherapy induces intratumoral expression of chemokines in cutaneous melanoma, favoring T-cell infiltration and tumor control.

T-cell infiltration is known to impact tumor growth and is associated with cancer patient survival. However, the molecular cues that favor T-cell infiltration remain largely undefined. Here, using a genetically engineered mouse model of melanoma, we show that CXCR3 ligands and CCL5 synergize to attract effector T cells into cutaneous metastases, and their expression inhibits tumor growth. Treatment of tumor-bearing mice with chemotherapy induced intratumoral expression of these chemokines and favored T-cell infiltration into cutaneous tumors. In patients with melanoma, these chemokines were also upregulated in chemotherapy-sensitive lesions following chemotherapy, and correlated with T-cell infiltration, tumor control, and patient survival. We found that dacarbazine, temozolomide, and cisplatin induced expression of T-cell-attracting chemokines in several human melanoma cell lines in vitro. These data identify the induction of intratumoral expression of chemokines as a novel cell-extrinsic mechanism of action of chemotherapy that results in the recruitment of immune cells with antitumor activity. Therefore, identifying chemotherapeutic drugs able to induce the expression of T-cell-attracting chemokines in cancer cells may represent a novel strategy to improve the efficacy of cancer immunotherapy.

Identification of the bacterial protein FtsX as a unique target of chemokine-mediated antimicrobial activity against Bacillus anthracis.

Chemokines are a family of chemotactic cytokines that function in host defense by orchestrating cellular movement during infection. In addition to this function, many chemokines have also been found to mediate the direct killing of a range of pathogenic microorganisms through an as-yet-undefined mechanism. As an understanding of the molecular mechanism and microbial targets of chemokine-mediated antimicrobial activity is likely to lead to the identification of unique, broad-spectrum therapeutic targets for effectively treating infection, we sought to investigate the mechanism by which the chemokine CXCL10 mediates bactericidal activity against the Gram-positive bacterium Bacillus anthracis, the causative agent of anthrax. Here, we report that disruption of the gene ftsX, which encodes the transmembrane domain of a putative ATP-binding cassette transporter, affords resistance to CXCL10-mediated antimicrobial effects against vegetative B. anthracis bacilli. Furthermore, we demonstrate that in the absence of FtsX, CXCL10 is unable to localize to its presumed site of action at the bacterial cell membrane, suggesting that chemokines interact with specific, identifiable bacterial components to mediate direct microbial killing. These findings provide unique insight into the mechanism of CXCL10-mediated bactericidal activity and establish, to our knowledge, the first description of a bacterial component critically involved in the ability of host chemokines to target and kill a bacterial pathogen. These observations also support the notion of chemokine-mediated antimicrobial activity as an important foundation for the development of innovative therapeutic strategies for treating infections caused by pathogenic, potentially multidrug-resistant microorganisms.

Chemokine receptor CXCR3 promotes growth of glioma.

Human glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. The poor prognosis and minimally successful treatments of GBM indicates a need to identify new therapeutic targets. In this study, we examined the role of CXCR3 in glioma progression using the GL261 murine model of malignant glioma. Intracranial GL261 tumors express CXCL9 and CXCL10 in vivo. Glioma-bearing CXCR3-deficient mice had significantly shorter median survival time and reduced numbers of tumor-infiltrated natural killer and natural killer T cells as compared with tumor-bearing wild-type (WT) mice. In contrast, pharmacological antagonism of CXCR3 with NBI-74330 prolonged median survival times of both tumor-bearing WT and CXCR3-deficient mice when compared with vehicle-treated groups. NBI-74330 treatment did not impact tumor infiltration of lymphocytes and microglia. A small percentage of GL261 cells were identified as CXCR3(+), which was similar to the expression of CXCR3 in several grade IV human glioma cell lines (A172, T98G, U87, U118 and U138). When cultured as gliomaspheres (GS), the human and murine lines increased CXCR3 expression; CXCR3 expression was also found in a primary human GBM-derived GS. Additionally, CXCR3 isoform A was expressed by all lines, whereas CXCR3-B was detected in T98G-, U118- and U138-GS cells. CXCL9 or CXCL10 induced in vitro glioma cell growth in GL261- and U87-GS as well as inhibited cell loss in U138-GS cells and this effect was antagonized by NBI-74330. The results suggest that CXCR3 antagonism exerts a direct anti-glioma effect and this receptor may be a potential therapeutic target for treating human GBM.

ESAT6-induced IFNgamma and CXCL9 can differentiate severity of tuberculosis.

BACKGROUND: Protective responses against Mycobacterium tuberculosis are dependent on appropriate T cell and macrophage activation. Mycobacterial antigen six kDa early secreted antigenic target (ESAT6) and culture filtrate protein 10 (CFP10) can detect M. tuberculosis specific IFNgamma responses. However, most studies have been performed in non-endemic regions and to study pulmonary tuberculosis (PTB). We have studied ESAT6 and CFP10 induced cytokine and chemokines responses in PTB and extrapulmonary (EPul) TB. METHODOLOGY: IFNgamma, IL10, CXCL9 and CCL2 responses were determined using an ex vivo whole blood assay system in PTB (n = 30) and EPulTB patients with limited (LNTB, n = 24) or severe (SevTB, n = 22) disease, and in healthy endemic controls (ECs). Responses to bacterial LPS were also determined. PRINCIPAL FINDINGS: ESAT6- and CFP10-induced IFNgamma was comparable between ECs and TB patients. Both ESAT6- and CFP10-induced IFNgamma secretion was greater in LNTB than PTB. ESAT6-induced CXCL9 was greater in EPulTB as compared with PTB, with an increase in SevTB as compared with LNTB. CFP10-induced CCL2 was higher in PTB than LNTB patients. LPS-stimulated CXCL9 was greatest in SevTB and LPS-induced CCL2 was increased in PTB as compared with LNTB patients. A positive correlation between ESAT6-induced IFNgamma and CXCL9 was present in all TB patients, but IFNgamma and CCL2 was only correlated in LNTB. ESAT-induced CCL2 and CXCL9 were significantly associated in LNTB while correlation in response to LPS was only present in SevTB. CONCLUSIONS: ESAT6 induced IFNgamma and CXCL9 can differentiate between limited and severe TB infections.

Insertion of the CXC chemokine ligand 9 (CXCL9) into the mouse hepatitis virus genome results in protection from viral-induced encephalitis and hepatitis.

The role of the CXC chemokine ligand 9 (CXCL9) in host defense following infection with mouse hepatitis virus (MHV) was determined. Inoculation of the central nervous system (CNS) of CXCL9-/- mice with MHV resulted in accelerated and increased mortality compared to wild type mice supporting an important role for CXCL9 in anti-viral defense. In addition, infection of RAG1-/- or CXCL9-/- mice with a recombinant MHV expressing CXCL9 (MHV-CXCL9) resulted in protection from disease that correlated with reduced viral titers within the brain and NK cell-mediated protection in the liver. Survival in MHV-CXCL9-infected CXCL9-/- mice was associated with reduced viral burden within the brain that coincided with increased T cell infiltration. Similarly, viral clearance from the livers of MHV-CXCL9-infected mice was accelerated but independent of increased T cell or NK cell infiltration. These observations indicate that CXCL9 promotes protection from coronavirus-induced neurological and liver disease.

CXCL9, but not CXCL10, promotes CXCR3-dependent immune-mediated kidney disease.

Chemokines are instrumental in macrophage- and T cell-dependent diseases. The chemokine CCL2 promotes kidney disease in two models of immune-mediated nephritis (MRL-Fas(lpr) mice and the nephrotoxic serum nephritis model), but evidence suggests that multiple chemokines are involved. For identification of additional therapeutic targets for immune-mediated nephritis, chemokine ligands and receptors in CCL2-/- and wild-type (WT) MRL-Fas(lpr) kidneys were profiled. The focus was on intrarenal chemokine ligand/receptor pairs that were highly upregulated downstream of CCL2; the chemokine CXCL10 and its cognate receptor, CXCR3, stood out as potential therapeutic targets. However, renal disease was not suppressed in CXCL10-/- MRL-Fas(lpr) mice, and CXCL10-/- C57BL/6 mice were not protected from nephrotoxic serum nephritis compared with WT mice. Because CXCR3 engages with the ligand CXCL9, CXCR3-/- , CXCL9-/- , and CXCL10-/- B6 mice were compared with WT mice with nephrotoxic serum nephritis. Kidney disease, measured by loss of renal function and histopathology, was suppressed in both CXCR3-/- and CXCL9-/- mice but not in CXCL10-/- mice. With nephrotoxic serum nephritis, CXCR3-/- and CXCL9-/- mice had fewer intrarenal activated T cells and activated macrophages. Both IgG glomerular deposits and antigen-specific IgG in serum were reduced in these mice, suggesting that although CXCR3 and CXCL9 initiate nephritis through cell-mediated events, renal inflammation may be sustained by their regulation of IgG. It is concluded that specific blockade of CXCL9

RhoA is involved in LFA-1 extension triggered by CXCL12 but not in a novel outside-in LFA-1 activation facilitated by CXCL9.

Chemokines presented on endothelial tissues instantaneously trigger LFA-1-mediated arrest on ICAM-1 via rapid inside-out and outside-in (ligand-driven) LFA-1 activation. The GTPase RhoA was previously implicated in CCL21-triggered LFA-1 affinity triggering in murine T lymphocytes and in LFA-1-dependent adhesion strengthening to ICAM-1 on Peyer's patch high endothelial venules stabilized over periods of at least 10 s. In this study, we show that a specific RhoA 23/40 effector region is vital for the initial LFA-1-dependent adhesions of lymphocytes on high endothelial venules lasting 1-3 s. Blocking the RhoA 23/40 region in human T lymphocytes in vitro also impaired the subsecond CXCL12-triggered LFA-1-mediated T cell arrest on ICAM-1 by eliminating the rapid induction of an extended LFA-1 conformational state. However, the inflammatory chemokine CXCL9 triggered robust LFA-1-mediated T lymphocyte adhesion to ICAM-1 at subsecond contacts independently of the RhoA 23/40 region. CXCL9 did not induce conformational changes in the LFA-1 ectodomain, suggesting that particular chemokines can activate LFA-1 through outside-in post ligand binding stabilization changes. Like CXCL9, the potent diacylglycerol-dependent protein kinase C agonist PMA was found to trigger LFA-1 adhesiveness to ICAM-1 also without inducing integrin extension or an a priori clustering and independently of the RhoA 23/40 region. Our results collectively suggest that the 23/40 region of RhoA regulates chemokine-induced inside-out LFA-1 extension before ligand binding, but is not required for a variety of chemokine and non-chemokine signals that rapidly strengthen LFA-1-ICAM-1 bonds without an a priori induction of high-affinity extended LFA-1 conformations.