The relative activity of CXCR3 and CCR5 ligands in T lymphocyte migration: concordant and disparate activities in vitro and in vivo

In chronic inflammatory reactions such as rheumatoid arthritis and multiple sclerosis, T cells in the inflamed tissue express the chemokine receptors CXCR3 and CCR5, and the chemokine ligands (CCL) of these receptors are present in the inflammatory lesions. However, the contribution of these chemokines to T cell recruitment to sites of inflammation is unclear. In addition, the relative roles of the chemokines that bind CXCR3 (CXCL9, CXCL10, CXCL11) and CCR5 (CCL3, CCL4, CCL5) in this process are unknown. The in vitro chemotaxis and in vivo migration of antigen-activated T lymphoblasts and unactivated spleen T cells to chemokines were examined. T lymphoblasts migrated in vitro to CXCR3 ligands with a relative potency of CXCL10 > CXCL11 > CXCL9, but these cells demonstrated much less chemotaxis to the CCR5 ligands. In vivo, T lymphocytes were recruited in large numbers with rapid kinetics to skin sites injected with CXCL10 and CCL5 and less to CCL3, CCL4, CXCL9, and CXCL11. The combination of CCL5 with CXCL10 but not the other chemokines markedly increased recruitment. Coinjection of interferon-gamma, tumor necrosis factor alpha, and interleukin-1alpha to up-regulate endothelial cell adhesion molecule expression with CXCL10 or CCL5 induced an additive increase in lymphoblast migration. Thus, CXCR3 ligands are more chemotactic than CCR5 ligands in vitro; however, in vivo, CXCL10 and CCL5 have comparable T cell-recruiting activities to cutaneous sites and are more potent than the other CXCR3 and CCR5 chemokines. Therefore, in vitro chemotaxis induced by these chemokines is not necessarily predictive of their in vivo lymphocyte-recruiting activity.     

Chemokine receptors that mediate B cell homing to secondary lymphoid tissues are highly expressed in B cell chronic lymphocytic leukemia and non-Hodgkin lymphomas with widespread nodular dissemination

B cell neoplasms present heterogeneous patterns of lymphoid organ involvement, which may be a result of the differential expression of chemokine receptors. We found that chemokine receptor (CCR)7, CXC chemokine receptor (CXCR)4, or CXCR5, the main chemokine receptors that mediate B cell entry into secondary lymphoid tissues and their homing to T cell and B cell zones therein, were highly expressed in B malignancies with widespread involvement of lymph nodes. Conversely, those pathologies with little or no nodular dissemination showed no expression to very low levels of CCR7 and CXCR5 and low to moderate levels of CXCR4. These findings provide evidence for the role of CCR7, CXCR4, and CXCR5 in determining the pattern of lymphoid organ involvement of B tumors. Functional studies were performed on B malignancies expressing different levels of CCR7, CXCR5, and CXCR4. Multiple myeloma (MM) cells did not express CCR7 nor CXCR5 and did not migrate in response to their ligands; a moderate expression of CXCR4 on MM cells was accompanied by a migratory response to its ligand, CXCL12. By contrast, cells from B cell chronic lymphocytic leukemia (B-CLL) expressed the highest levels of these chemokine receptors and efficiently migrated in response to all ligands of CCR7, CXCR4, and CXCR5. In addition, the migration index of B-CLL cells in response to both of the CCR7 ligands correlated with the presence of clinical lymphadenopathy, thus indicating that the high expression of functional chemokine receptors justifies the widespread character of B-CLL, representing a clinical target for the control of tumor cell dissemination.     

Chemokine Receptor CXCR4 Is a Novel Marker for the Progression of Cutaneous Malignant Melanomas

The CXCR4/CXCL12 pathway has recently been reported to be involved in stimulating the metastasis of many different neoplasms, in which CXCR4 activates various phenomena such as chemotaxis, invasion, angiogenesis and proliferation. The purpose of this study was to analyze a possible association between the expression of chemokine receptors CXCR4, CCR6 and CCR7 with the clinicopathological features of cutaneous malignant melanoma, and to assess the usefulness of these chemokine receptors for diagnosis and prognosis. In our study, a percentage of immunoexpression of both CXCR4 and its ligands CXCL12 was associated with high clinical risk. In contrast, the patients with a low immunoexpression of CXCR4 and CXCL12 had low clinical risk. CCR6 and CCR7 immunoexpressions were also correlated with some clinical parameters, but seemed no more useful than CXCR4. These data suggest that the assessment of CXCR4 immunoexpression is a novel tool for predicting tumor aggressiveness in malignant melanomas, and in particular, a high immunoexpression percentage of CXCR4 and CXCL12 might be a sign of a poor prognosis.     

Regulation of human neutrophil chemokine receptor expression and function by activation of Toll-like receptors 2 and 4

Neutrophil chemokine receptor expression can be altered by exposure to Toll-like receptor (TLR) agonists, a process that is thought to have the potential to localize neutrophils to sites of infection. In order to investigate this process in more detail, we examined the regulation of highly pure neutrophil CXCR1 and CXCR2 expression and function by selective agonists of TLR2 (Pam(3)CSK(4)) and TLR4 (lipopolysaccharide, LPS). CXCR1 and CXCR2 were down-regulated by TLR engagement. CXCR2 loss was more rapid and showed a dependence upon soluble helper molecules (LPS binding protein and CD14) that was not evident for CXCR1, suggesting differential coupling of LPS signalling to CXCR1 and CXCR2 loss. However, TLR engagement in highly pure neutrophils did not result in complete loss of chemokine receptors, and LPS-treated neutrophils remained able to mount a respiratory burst to CXCL8 and CXCL1, and were able to migrate towards CXCL8 in assays of under-agarose chemotaxis. Thus, although treatment of purified human neutrophils with TLR2 and TLR4 agonists modifies chemokine receptor expression, remaining receptors remain functionally competent.     

大疱性类天疱疮皮损中Th1/Th2趋化因子及其受体的表达

目的:研究Th1趋化因子CXCL9/MIG、CXCL10/IP-10、CXCL11/I-TAC和Th2型趋化因子CCL22/MDC及其受体CXCR3、CCR4在大疱性类天疱疮(BP)皮损中的表达。方法:应用免疫组化方法检测30例BP患者皮损及20例正常皮肤中CX-CL9、CXCL10、CXCL11、CCL22、CXCR3和CCR4的表达。结果:BP皮损中4种趋化因子及其受体的表达均高于正常皮肤。其中,Th1趋化因子CXCL9、CXCL10和CXCL11及其受体CXCR3的阳性率分别为50%(15/30)、46.7%(14/30)、46.7%(14/30)和53.3%(16/30),Th2趋化因子CCL22及其受体CCR4的阳性率分别为66.7%(20/30)、56.7%(17/30)。正常对照中CXCL9、CX-CL10、CXCL11及其受体CXCR3的阳性率分别为10.0%(2/20)、10.0%(2/20)、15.0%(3/20)和15.0%(3/20),CCL22及其受体CCR4的阳性率分别为20.0%(4/20)和25.0%(5/20)。结论:Th1趋化因子CXCL9、CXCL10、CXCL11和Th2趋化因子CCL22及其受体CXCR3和CCR4在BP皮损中表达升高,提示它们可能在BP的发病机制中起一定作用。     

The secretion of HMGB1 is required for the migration of maturing dendritic cells

Chemokines regulate the migration and the maturation of dendritic cells (DC) licensed by microbial constituents. We have recently found that the function of DC, including their ability to activate na?ve, allogeneic CD4+ T cells, requires the autocrine/paracrine release of the nuclear protein high mobility group box 1 (HMGB1). We show here that human myeloid DC, which rapidly secrete upon maturation induction their own HMGB1, remodel their actin-based cytoskeleton, up-regulate the CCR7 and the CXCR4 chemokine receptors, and acquire the ability to migrate in response to chemokine receptor ligands. The events are apparently causally related: DC challenged with LPS in the presence of HMGB1-specific antibodies fail to up-regulate the expression of the CCR7 and CXCR4 receptors and to rearrange actin-rich structures. Moreover, DC matured in the presence of anti-HMGB1 antibodies fail to migrate in response to the CCR7 ligand CCL19 and to the CXCR4 ligand CXCL12. The blockade of receptor for advanced glycation end products (RAGE), the best-characterized membrane receptor for HMGB1, impinges as well on the up-regulation of chemokine receptors and on responsiveness to CCL19 and CXCL12. Our data suggest that the autocrine/paracrine release of HMGB1 and the integrity of the HMGB1/RAGE pathway are required for the migratory function of DC.     

Strong expression of CXCL12 is associated with a favorable outcome in osteosarcoma

Hematogenous spread determines the outcome of osteosarcoma (OS) patients, but the pathogenesis of developing metastatic disease is still unclear. Chemokines are critical regulators of cell trafficking and adhesion, and have been reported to be aberrantly expressed and to correlate with an unfavorable prognosis and metastatic spread in several malignant tumors. The chemokine receptors CXCR4 and CXCR7 together with their common ligand CXCL12 form one of the most important chemokine axes in this context. To investigate a potential role of these chemokines in OSs, we analyzed their expression in a series of 223 well-characterized and pretherapeutic OS samples. Interestingly, we found the expression of CXCL12 and CXCR4 to correlate with a better long-term outcome and with a lower prevalence of metastases. These findings suggest a distinct role of CXCR4/CXCR7/CXCL12 signaling in the tumors of bone, as has also been previously described in acute leukemia. As many malignant tumors metastasize to bone, and tumor cells are thought to be directed to bone in response to CXCL12, OS cells expressing both CXCL12 and the corresponding receptors might be detained at their site of origin. The disruption of CXCR4/CXCR7/CXCL12 signaling could therefore be crucial in OSs for the migration of tumor cells from bone into circulation and for developing systemic disease.     

CCL27-CCR10 and CXCL12-CXCR4 chemokine ligand-receptor mRNA expression ratio: new predictive factors of tumor progression in cutaneous malignant melanoma

CXCR4, CCR7 and CCR10 chemokine receptors are known to be involved in melanoma metastasis. Our goal was to compare the relative intratumoral mRNA expression of these receptors with that of their corresponding chemokine ligands, CXCL12, CCL19, CCL21, and CCL27 across the full spectrum of human melanoma progression: thin and thick primary melanomas, as well as "in transit", lymph node, and distant metastases. Expression was quantified by real-time RT-PCR in 103 melanoma samples: 51 primary tumors and 52 metastases. Particular emphasis was focused on chemokine ligand-receptor expression ratios. Immunohistochemistry was performed to identify the cell types expressing these molecules. CXCL12-CXCR4 and CCL27-CCR10 ratios were higher in thin than in thick primary melanomas, and all four chemokine-receptor ratios were higher in primary tumors than in melanoma metastases. CCL27-CCR10 and CXCL12-CXCR4 expression ratios in primary tumors were inversely associated with the development of distant metastases, and improved the predictive value of tumor thickness for distant metastasis, which is important since chemokine ligand-receptor ratios are not affected by the endogenous gene employed for normalizing mRNA expression. Both receptor and ligand immunolabeling were detected in neoplastic cells suggesting autocrine mechanisms. Our results support the concept that low CCL27/CCR10 and CXCL12/CXCR4 intratumoral mRNA ratios are associated with melanoma progression, and in combination with Breslow thickness, are the best predictive factors for the development of distant metastases in primary cutaneous melanoma.     

Synergistic induction of CXCL9 and CXCL11 by Toll-like receptor ligands and interferon-gamma in fibroblasts correlates with elevated levels of CXCR3 ligands in septic arthritis synovial fluids

The synovial cavity constitutes the ideal stage to study the interplay between microbial Toll-like receptor (TLR) ligands and cytokines. Infiltrated leukocytes and synovial fibroblasts produce cytokine- and chemokine-induced proteases for remodeling the extracellular matrix. The regulation of chemokine function for attraction and activation of leukocytes constitutes a key feature in host immunity and resolution of inflammation after infection. Enhanced levels of the CXC chemokine ligand (CXCL9)/monokine induced by interferon-gamma (IFN-gamma) and CXCL11/IFN-inducible T cell alpha chemoattractant, two chemoattractants for activated T cells and natural killer cells, and ligands for CXC chemokine receptor 3 (CXCR3) were detected in the synovial fluid of septic arthritis compared with osteo- and crystal arthritis patients. In vitro, IFN-gamma and TLR3 ligation by double-stranded RNA (dsRNA) induced the expression of CXCL9 and CXCL11 in leukocytes and skin-muscle fibroblasts, whereas ligation of TLR2, TLR4, TLR5, and TLR9 by peptidoglycan (PGN), lipopolysaccharide (LPS), flagellin, and unmethylated CpG oligonucleotides, respectively, did not. PGN and LPS, but not unmethylated CpG oligonucleotides, even inhibited IFN-gamma-induced CXCL9 and CXCL11 expression in leukocytes. In sharp contrast, in fibroblasts, the TLR ligands PGN, dsRNA, LPS, and flagellin synergized with IFN-gamma for the production of CXCL9 and CXCL11. Although TLR ligands stimulate leukocytes to produce CXCL8/interleukin-8 during the early innate defense, they contribute less to the production of CXCR3 ligands, whereas fibroblasts are important sources of CXCR3 ligands. These results illustrate the complex interaction between cytokines and TLR ligands in infection.     

Ligand stabilization of CXCR4/delta-opioid receptor heterodimers reveals a mechanism for immune response regulation

The CXCR4 chemokine receptor and the delta opioid receptor (DOR) are pertussis toxin-sensitive G protein-coupled receptors (GPCR). Both are widely distributed in brain tissues and immune cells, and have key roles in inflammation processes and in pain sensation on proximal nerve endings. We show that in immune cells expressing CXCR4 and DOR, simultaneous addition of their ligands CXCL12 and [D-Pen2, D-Pen5]enkephalin does not trigger receptor function. This treatment does not affect ligand binding or receptor expression, nor does it promote heterologous desensitization. Our data indicate that CXCR4 and DOR form heterodimeric complexes that are dynamically regulated by the ligands. This is compatible with a model in which GPCR oligomerization leads to suppression of signaling, promoting a dominant negative effect. Knockdown of CXCR4 and DOR signaling by heterodimerization might have repercussions on physiological and pathological processes such as inflammation, pain sensation and HIV-1 infection.     

CXCL4-induced migration of activated T lymphocytes is mediated by the chemokine receptor CXCR3

The chemokine CXCL4/platelet factor-4 is released by activated platelets in micromolar concentrations and is a chemoattractant for leukocytes via an unidentified receptor. Recently, a variant of the human chemokine receptor CXCR3 (CXCR3-B) was described, which transduced apoptotic but not chemotactic signals in microvascular endothelial cells following exposure to high concentrations of CXCL4. Here, we show that CXCL4 can induce intracellular calcium release and the migration of activated human T lymphocytes. CXCL4-induced chemotaxis of T lymphocytes was inhibited by a CXCR3 antagonist and pretreatment of cells with pertussis toxin (PTX), suggestive of CXCR3-mediated G-protein signaling via Galphai-sensitive subunits. Specific binding by T lymphocytes of the CXCR3 ligand CXCL10 was not effectively competed by CXCL4, suggesting that the two are allotopic ligands. We subsequently used expression systems to dissect the potential roles of each CXCR3 isoform in mediating CXCL4 function. Transient expression of the CXCR3-A and CXCR3-B isoforms in the murine pre-B cell L1.2 produced cells that migrated in response to CXCL4 in a manner sensitive to PTX and a CXCR3 antagonist. Binding of radiolabeled CXCL4 to L1.2 CXCR3 transfectants was of low affinity and appeared to be mediated chiefly by glycosaminoglycans (GAGs), as no specific CXCL4 binding was observed in GAG-deficient 745-Chinese hamster ovary cells stably expressing CXCR3. We suggest that following platelet activation, the CXCR3/CXCL4 axis may play a role in T lymphocyte recruitment and the subsequent amplification of inflammation observed in diseases such as atherosclerosis. In such a setting, antagonism of the CXCR3/CXCL4 axis may represent a useful, therapeutic intervention.     

Long-term exposure of chemokine CXCL10 causes bronchiolitis-like inflammation

Chemokines and chemokine receptors have been implicated in the pathogenesis of bronchiolitis. CXCR3 ligands (CXCL10, CXCL9, and CXCL11) were elevated in patients with bronchiolitis obliterans syndrome (BOS) and chronic allorejection. Studies also suggested that blockage of CXCR3 or its ligands changed the outcome of T-cell recruitment and airway obliteration. We wanted to determine the role of the chemokine CXCL10 in the pathogenesis of bronchiolitis and BOS. In this study, we found that CXCL10 mRNA levels were significantly increased in patients with BOS. We generated transgenic mice expressing a mouse CXCL10 cDNA under control of the rat CC10 promoter. Six-month-old CC10-CXCL10 transgenic mice developed bronchiolitis characterized by airway epithelial hyperplasia and developed peribronchiolar and perivascular lymphocyte infiltration. The airway hyperplasia and T-cell inflammation were dependent on the presence of CXCR3. Therefore, long-term exposure of the chemokine CXCL10 in the lung causes bronchiolitis-like inflammation in mice.     

The expression of the chemokine receptor CXCR3 and its ligand, CXCL10, in human breast adenocarcinoma cell lines

The acquisition of a metastatic phenotype in breast epithelial cells is a progressive process, influenced by a large variety of cellular and soluble factors. Of these, members of the chemokine superfamily, such as CCL2, CCL5, CXCL8 and CXCL12 have been recently suggested to promote breast cancer progression. A pre-requisite for elucidation of the role of other chemokines in breast cancer progression is the characterization of chemokine and chemokine receptor expression by breast tumor cells. The present study focuses on CXCL10, a CXC chemokine that was recently suggested to have anti-malignant properties, and its corresponding receptor CXCR3. CXCR3 expression was detected in three human breast adenocarcinoma cell lines, MDA-MB-231, MCF-7 and T47D. CXCR3 expression was potently up-regulated by growing the cells under stress conditions, imposed by serum starvation. Unlike many other chemokine receptors, CXCR3 expression was not down-regulated by exposure to high concentrations (500ng/ml) of its ligand, CXCL10, but rather was promoted. CXCL10-induced up-regulation of CXCR3 expression in the three cell lines was inhibited by cycloheximide, indicating that de novo protein synthesis is required for this process. In addition to CXCR3, the secretion of CXCL10 was noted in the MDA-MB-231, MCF-7 and T47D cells. CXCL10 secretion was found to be down-regulated by IL-6, a potentially pro-malignant cytokine in breast cancer. The concomitant expression of CXCR3 and CXCL10 in breast tumor cells suggests that a CXCR3-CXCL10 axis may function in these cells, and paves the way for an in depth analysis of CXCL10-CXCR3 interactions in breast tumor cells.     

Chemokines in the systemic organization of immunity

Summary: Directed cellular migrations underlie immune system organization. Chemokines and their receptors (along with surface‐adhesion molecules) are central to these migrations, targeting developing and mature leukocytes to tissues and microenvironments suitable for their differentiation and function. The chemokine CXCL12 and its receptor CXCR4 play a central role in the migration of hematopoietic stem cells, and several chemokine receptors are transiently expressed during distinct stages of B‐ and T‐cell development. In the periphery, mature naïve B and T cells utilize the receptors CCR7, CXCR4, and CXCR5 to recirculate through specialized microenvironments within the secondary lymphoid tissues, while effector and memory lymphocytes express bewildering patterns of adhesion molecules and chemokine receptors that allow them to function within microenvironments and non‐lymphoid tissues inaccessible to naïve cells. Here, we summarize the role of chemokines and their receptors in the spatial organization of the immune system and consider the implications for immune function.     

Development of a novel chemokine-mediated in vivo T cell recruitment assay

Trafficking of leukocytes to sites of inflammation is an important step in the establishment of an immune response. Chemokines are critical regulators of leukocyte trafficking and are widely studied molecules for their important role in disease and for their potential as new therapeutic targets. The ability of chemokines to induce leukocyte recruitment has been mainly measured by in vitro chemotaxis assays, which lack many components of the complex biological process of leukocyte migration and therefore provide incomplete information about chemokine function in vivo. In vivo assays to study the activity of chemokines to induce leukocyte recruitment have been difficult to establish. We describe here the development of a robust in vivo recruitment assay for CD8(+) and CD4(+) T lymphocytes induced by the CXCR3 ligands IP-10 (CXCL10) and I-TAC (CXCL11). For this assay, in vitro activated T lymphocytes were adoptively transferred into the peritoneum of na?ve mice. Homing of these transferred T lymphocytes into the airways was measured following intratracheal instillation of chemokines. High recruitment indices were achieved that were dependent on chemokine concentration and CXCR3 expression on the transferred lymphocytes. Recruitment was also inhibited by antibodies to the chemokine. The assay models the natural condition of chemokine-mediated lymphocyte migration into the airways as chemokines are expressed in the airways during inflammation. The nature of this model allows flexibility to study wildtype and mutant chemokines and chemokine receptors and the ability to evaluate chemokine antagonists and antibodies in vivo. This assay will therefore help elucidate a deeper understanding of the chemokine system in vivo.     

Inflammatory chemokines and their receptors in human visceral leishmaniasis: Gene expression profile in peripheral blood,splenic cellular sources and their impact on trafficking of inflammatory cells

Chemokines play an important role in determining cellular composition at inflammatory sites, and as such, influence disease outcome. In this study, we investigated the expression profile and splenic cellular source of various inflammatory chemokines and their receptors in human visceral leishmaniasis (VL). The expression of chemokines or their receptors was measured at the gene and protein level by employing real time qPCR and a cytometric bead array assay, respectively. In addition, the cellular source of chemokines and their receptors in the spleen was identified employing gene expression analyses in sequentially selected cell subsets. We identified elevated expression of CXCL10, CXCL9, CXCL8, and decreased CCL2 from VL patients. Further, we found reduced expression of the chemokine receptors CXCR1, CXCR2, CXCR3 and CCR2, but increased expression of CCR7 on VL PBMC, compared to endemic healthy controls. Additionally, splenic monocytes were found to be the major source of CXCL10, CXCL9 and CCR2, whereas T cells were the main source of CXCR3 and CCR7. We also report a strong association between plasma IFN-γ and CXCL-10, CXCL-9 levels. Enhanced parasite burden positively correlates with increased expression of CXCL10, CXCL9, IFN-γ and IL-10. Overall our result indicates that VL patients have an elevated inflammatory chemokine milieu which correlated with disease severity. However, expression of their chemokine receptors was significantly impaired, which may have contributed to reduced frequencies of blood monocytes and neutrophils in peripheral blood. In contrast, enhanced expression of CCR7 was associated with increased numbers of activated T cells in circulation. These findings highlight the importance of chemokines for recruitment of various cell populations in VL, and the knowledge gained may help in global understandings of the complex interaction between chemokines and pathological processes, and therefore will contribute towards the design of novel chemokine based immunological therapies against VL.     

Chemokines and other GPCR ligands synergize in receptor-mediated migration of monocyte-derived immature and mature dendritic cells

Dendritic cells (DCs) are potent antigen presenting cells, described as the initiators of adaptive immune responses. Immature monocyte-derived DCs (MDDC) showed decreased CD14 expression, increased cell surface markers DC-SIGN and CD1a and enhanced levels of receptors for the chemokines CCL3 (CCR1/CCR5) and CXCL8 (CXCR1/CXCR2) compared with human CD14⁺ monocytes. After further MDDC maturation by LPS, the markers CD80 and CD83 and the chemokine receptors CXCR4 and CCR7 were upregulated, whereas CCR1, CCR2 and CCR5 expression was reduced. CCL3 dose-dependently synergized with CXCL8 or CXCL12 in chemotaxis of immature MDDC. CXCL12 augmented the CCL3-induced ERK1/2 and Akt phosphorylation in immature MDDC, although the synergy between CCL3 and CXCL12 in chemotaxis of immature MDDC was dependent on the Akt signaling pathway but not on ERK1/2 phosphorylation. CCL2 also synergized with CXCL12 in immature MDDC migration. Moreover, two CXC chemokines not sharing receptors (CXCL12 and CXCL8) cooperated in immature MDDC chemotaxis, whereas two CC chemokines (CCL3 and CCL7) sharing CCR1 did not. Further, the non-chemokine G protein-coupled receptor ligands chemerin and fMLP synergized with respectively CCL7 and CCL3 in immature MDDC signaling and migration. Finally, CXCL12 and CCL3 did not cooperate, but CXCL12 synergized with CCL21 in mature MDDC chemotaxis. Thus, chemokine synergy in immature and mature MDDC migration is dose-dependently regulated by chemokines via alterations in their chemokine receptor expression pattern according to their role in immune responses.     

Expression of rat I-TAC/CXCL11/SCYA11 during central nervous system inflammation: comparison with other CXCR3 ligands

The chemokines are a large gene superfamily with critical roles in development and immunity. The chemokine receptor CXCR3 appears to play a major role in the trafficking of activated Th1 lymphocytes. There are at least three major ligands for CXCR3: mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11, and of these three ligands, CXCL11 is the least well-characterized. In this study, we have cloned a rat ortholog of CXCL11, evaluated its function, and examined its expression in the Th-1-mediated disease, experimental autoimmune encephalomyelitis (EAE) in the rat. Based on its predicted primary amino-acid sequence, rat I-TAC/CXCL11 was synthesized and shown to induce chemotaxis of activated rat T lymphocytes in vitro and the in vivo migration of T lymphocytes when injected into the skin. I-TAC/CXCL11 expression, as determined by RT-PCR, increased in lymph node and spinal cord tissue collected from rats in which EAE had been actively induced, and in spinal cord tissue from rats in which EAE had been passively induced. The kinetics of expression were similar to that of CXCR3 and IP-10/CXCL10, although expression of both CXCR3 and IP-10/CXCL10 was more intense than that of I-TAC/CXCL11 and increased more rapidly in both lymph nodes and the spinal cord. Only minor levels of expression of the related chemokine mig/CXCL9 were observed. Immunohistochemistry revealed that the major cellular source of I-TAC/CXCL11 in the central nervous system (CNS) during EAE is likely to be the astrocyte. Together, these data indicate that I-TAC/CXCL11 is expressed in the CNS during the clinical phase of EAE. However, the observation that I-TAC/CXCL11 is expressed after receptor expression is detected suggests that it is not essential for the initial migration of CXCR3-bearing cells into the CNS.     

Pleiotropic effects of CXC chemokines in gastric carcinoma: differences in CXCL8 and CXCL1 expression between diffuse and intestinal types of gastric carcinoma

CXC chemokines modulate host immunity, neovascularization, growth and invasive behaviour of tumours. Despite their relevance in tumour biology, chemokine expression in intestinal- and diffuse-type gastric carcinoma, which exhibit a completely different growth pattern, has not been investigated in detail. In this study, expression of the CXC chemokines CXCL8 [interleukin (IL)-8], CXCL1 [growth-related oncogene alpha (Gro alpha)], CXCL9 [monokine induced by interferon (IFN)-gamma] and CXCL10 [IFN-gamma-inducible protein-10 (IP-10)] and the corresponding chemokine receptors CXCR1-3 was investigated by immunohistochemistry in intestinal- and diffuse-type gastric carcinoma. Tumour cells of all patients expressed CXCL8. CXCL8 expression was significantly stronger in tumour cells of diffuse- rather than intestinal-type gastric carcinoma (P < 0.01) as determined by a semiquantitative score. CXCL1 was expressed almost exclusively by diffuse- but not intestinal-type carcinoma cells. The corresponding chemokine receptors, CXCR1 and CXCR2, were found on carcinoma cells. Furthermore, CXCL8 expression correlated with number of tumour vessels (P < 0.01), suggesting an angiogenetic function in gastric carcinoma not only in vitro but also in vivo. CXCL10 and CXCL9, attractants for T cells, were expressed by peritumorous macrophages in close proximity to IFN-gamma-producing CXCR3-positive T cells in both tumour types. These chemokines may attract gastric carcinoma-infiltrating T cells via an IFN-gamma-mediated pathway and enhance host immunity against the tumour. In gastric carcinoma a complex interplay between CXC-chemokine signals derived from both tumour cells and tumour-infiltrating immune cells may exhibit pleiotropic effects in tumour biology that go far beyond their originally described functions as leucocyte chemoattractants. Because CXCL8 and CXCL1, which are known to increase growth and invasive behaviour of malignant tumours, are significantly stronger expressed in diffuse- than intestinal-type gastric carcinoma, one may speculate that these chemokines influence the different growth pattern of gastric carcinoma types.