Anti-tumor activity of chemokine is affected by both kinds of tumors and the activation state of the host’s immune system: implications for chemokine-based cancer immunotherapy

In this study, we screened the anti-tumor activity of murine chemokines including CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1, and CX3CL1 by inoculating murine B16BL6, CT26, or OV-HM tumor cells, all of which were transfected with chemokine-expressing fiber-mutant adenovirus vector, into immunocompetent mice. A tumor-suppressive effect was observed in mice inoculated with CCL19/B16BL6 and XCL1/B16BL6, and CCL22/OV-HM showed considerable retardation in tumor growth. In the cured mice inoculated with CCL22/OV-HM, a long-term specific immune protection against parental tumor was developed. However, we were unable to identify the chemokine that had a suppressive activity common to all three tumor models. Furthermore, an experiment using chemokine-transfected B16BL6 cells was also performed on mice sensitized with melanoma-associated antigen. A drastic enhancement of the frequency of complete rejection was observed in mice inoculated with CCL17-, CCL19-, CCL22-, and CCL27-transfected B16BL6. Altogether, our results suggest that the tumor-suppressive activity of chemokine-gene immunotherapy is greatly influenced by the kind of tumor and the activation state of the host's immune system.

Expression of CCL28 by Reed-Sternberg cells defines a major subtype of classical Hodgkin's disease with frequent infiltration of eosinophils and/or plasma cells

Classical Hodgkin's disease (HD) is characterized by rare neoplastic Hodgkin and Reed-Sternberg (H-RS) cells within abundant reactive cellular backgrounds. In most cases, H-RS cells originate from the B-cell lineage, but their immunophenotypes are unusual. Here we newly found frequent expression of chemokine receptors CXCR6 and CCR10 and their respective ligands CXCL16 and CCL28 in HD-derived cell lines. CCR10 is known to be selectively expressed by plasma cells, whereas CCL28 attracts eosinophils via CCR3 and plasma cells via CCR10 and CCR3. Therefore, we examined their expression in HD tissues by immunohistochemistry. We found that H-RS cells in 15 of 19 cases were positive for CCL28. Among them, seven cases were also positive for CCR10, suggesting a potential autocrine effect. In situ hybridization confirmed the expression of CCL28 mRNA in H-RS cells. The CCL28 positivity in H-RS cells did not significantly correlate with that of LMP-1, CCL17, CCL22, or CCL11. However, it significantly correlated with the background accumulation of eosinophils, plasma cells, and CCR10+ cells. Thus, the production of CCL28 by H-RS cells may play a major role in tissue accumulation of eosinophils and/or plasma cells in classical HD. The frequent expression of CCR10 in H-RS cells themselves also supports their close relationship to plasma cells.

Selective induction of Th2-attracting chemokines CCL17 and CCL22 in human B cells by latent membrane protein 1 of Epstein-Barr virus

Chemokines are likely to play important roles in the pathophysiology of diseases associated with Epstein-Barr virus (EBV). Here, we have analyzed the repertoire of chemokines expressed by EBV-infected B cells. EBV infection of B cells induced expression of TARC/CCL17 and MDC/CCL22, which are known to attract Th2 cells and regulatory T cells via CCR4, and also upregulated constitutive expression of MIP-1 alpha/CCL3, MIP-1 beta/CCL4, and RANTES/CCL5, which are known to attract Th1 cells and cytotoxic T cells via CCR5. Accordingly, EBV-immortalized B cells secreted these chemokines, especially CCL3, CCL4, and CCL22, in large quantities. EBV infection or stable expression of LMP1 also induced CCL17 and CCL22 in a B-cell line, BJAB. The inhibitors of the TRAF/NF-kappa B pathway (BAY11-7082) and the p38/ATF2 pathway (SB202190) selectively suppressed the expression of CCL17 and CCL22 in EBV-immortalized B cells and BJAB-LMP1. Consistently, transient-transfection assays using CCL22 promoter-reporter constructs demonstrated that two NF-kappa B sites and a single AP-1 site were involved in the activation of the CCL22 promoter by LMP1. Finally, serum CCL22 levels were significantly elevated in infectious mononucleosis. Collectively, LMP1 induces CCL17 and CCL22 in EBV-infected B cells via activation of NF-kappa B and probably ATF2. Production of CCL17 and CCL22, which attract Th2 and regulatory T cells, may help EBV-infected B cells evade immune surveillance by Th1 cells. However, the concomitant production of CCL3, CCL4, and CCL5 by EBV-infected B cells may eventually attract Th1 cells and cytotoxic T cells, leading to elimination of EBV-infected B cells at latency III and to selection of those with limited expression of latent genes.

Infiltration of CD8+ T cells containing RANTES/CCL5+ cytoplasmic granules in actively inflammatory lesions of human chronic gastritis

Chronic gastritis is frequently associated with infection of Helicobacter pylori and characterized by tissue infiltration of neutrophils, lymphocytes, and plasma cells. To address the mechanism of lymphocyte infiltration in chronic gastritis, we examined the expression of chemokines and their receptors using frozen sections of chronic gastritis, obtained from 23 patients who underwent gastrectomy for gastric cancer. By immunohistochemistry, lymphocytes in inflamed gastric mucosa expressed CCR5 abundantly, CXCR3 less frequently, and CCR4 sparsely. The numbers of CCR5(+) cells, which were composed of mainly CD8(+) and partly CD4(+) T cells, were positively correlated with the degree of neutrophil infiltration, and decreased in areas with intestinal metaplasia or mucosal atrophy. RANTES/CCL5, one of the ligands of CCR5, was localized mainly in CD8(+) and partly CD4(+) T cells with a characteristic dotted pattern, and such lymphocytes were most densely distributed around the neck region of gastric glands. In situ hybridization confirmed the expression of CCL5 mRNA in these cells, and immunoelectron microscopy revealed localization of CCL5 in the membrane-bound granules, which most probably corresponded to the cytolytic granules of cytotoxic T cells. The numbers of CCL5(+) lymphocytes showed a close correlation with the degree of neutrophil infiltration and markedly decreased in intestinal metaplasia. In conclusion, our data suggest that, together with neutrophils, CCL5(+) T cells, presumably activated cytotoxic T cells, would play important roles in the active inflammatory process of chronic gastritis. Our data also suggest a self-recruiting mechanism involving CCR5 and CCL5 for tissue accumulation of such T cells.

Tumor-suppressive activities by chemokines introduced into OV-HM cells using fiber-mutant adenovirus vectors

In this study, fiber-mutant adenovirus vectors encoding chemokines, Ad-RGD-mCCL17, Ad-RGD-mCCL21 and Ad-RGD-mCCL22 were constructed. The insertion of integrin-targeting RGD sequence into fiber knob of adenovirus vectors notably enhanced the infection efficiency into tumor cells. Among three chemokine-encoding vectors evaluated, Ad-RGD-mCCL22 showed significant tumor-suppressive activity via transduction into OV-HM cells.

Concerted expression of eotaxin-1, eotaxin-2, and eotaxin-3 in human bronchial epithelial cells

Eotaxin-1/CCL11, eotaxin-2/CCL24, and eotaxin-3/CCL26 bind specifically and exclusively to CC chemokine receptor (CCR) 3, which is a potential therapeutic target in treating the peribronchial eosinophilia associated with allergic airway diseases. Bronchial epithelial cells represent an important source of chemokines, and thus we investigated in vitro and in vivo expression of eotaxin-2 and eotaxin-3 in bronchial epithelial cells in comparison with that of eotaxin-1. Immunohistochemistry showed increased expression of both eotaxin-2 and eotaxin-3 in addition to eotaxin-1 in asthmatics. Considerable amounts of eotaxins were secreted by bronchial epithelial lineage. As with eotaxin-1 production, generation of eotaxin-2 and eotaxin-3 by bronchial epithelial cells was up-regulated by IL-4 and IL-13, and attenuated by IFN-gamma and glucocorticoids. In addition to eotaxin-1 expression, but also eotaxin-2 and eotaxin-3 expression in the bronchial epithelium should be taken into consideration when developing the therapeutic strategies to treat eosinophilic airway diseases.

A tetraspanin-family protein, T-cell acute lymphoblastic leukemia-associated antigen 1, is induced by the Ewing's sarcoma-Wilms' tumor 1 fusion protein of desmoplastic small round-cell tumor

Recurrent chromosomal translocations in neoplasms often generate hybrid genes that play critical roles in tumorigenesis. Desmoplastic small round-cell tumor (DSRCT) is an aggressive malignancy associated with the chromosomal translocation t(11;22)(p13;q12). This translocation generates a chimeric transcription factor, EWS-WT1, which consists of the transcriptional activation domain of the Ewing's sarcoma (EWS) protein and the DNA binding domain of the Wilms' tumor 1 (WT1) protein. One of the splice variants, EWS-WT1(-KTS) lacks three amino acid residues (Lys-Thr-Ser) in the DNA binding domain and transforms NIH3T3 cells. Therefore, it is likely that aberrant gene expression caused by EWS-WT1(-KTS) is involved in the malignant phenotype of DSRCT. Microarray analysis of 9600 human genes revealed that a gene encoding a tetraspanin-family protein, T-cell acute lymphoblastic leukemia-associated antigen 1 (TALLA-1), was induced in EWS-WT1(-KTS)-expressing cell clones. This induction was EWS-WT1(-KTS)-specific, and more importantly, TALLA-1 protein was expressed in the three independent cases of DSRCT. Tetraspanin-family genes encode transmembrane proteins that regulate various cell processes such as cell adhesion, migration and metastasis. Our findings provide a novel insight into the malignant phenotype of DSRCT, suggesting that TALLA-1 is a useful marker for diagnosis and a potential target for the therapy of DSRCT.

Fractalkine in vascular biology: from basic research to clinical disease

Fractalkine (now also called CX3CL1) is a unique chemokine that functions not only as a chemoattractant but also as an adhesion molecule and is expressed on endothelial cells activated by proinflammatory cytokines, such as interferon-gamma and tumor necrosis factor-alpha. The fractalkine receptor, CX3CR1, is expressed on cytotoxic effector lymphocytes, including natural killer (NK) cells and cytotoxic T lymphocytes, which contain high levels of intracellular perforin and granzyme B, and on macrophages. Soluble fractalkine causes migration of NK cells, cytotoxic T lymphocytes, and macrophages, whereas the membrane-bound form captures and enhances the subsequent migration of these cells in response to secondary stimulation with other chemokines. Furthermore, stimulation through membrane-bound fractalkine activates NK cells, leading to increased cytotoxicity and interferon-gamma production. Recently, accumulating evidence has shown that fractalkine is involved in the pathogenesis of various clinical disease states or processes, such as atherosclerosis, glomerulonephritis, cardiac allograft rejection, and rheumatoid arthritis. In addition, polymorphisms in CX3CR1, which reduce its binding activity to fractalkine, have been reported to increase the risk of HIV disease and to reduce the risk of coronary artery disease. This review will examine new concepts underlying fractalkine-mediated leukocyte migration and tissue damage, focusing primarily on the pathophysiological roles of fractalkine in various clinical conditions, especially in atherosclerosis and vascular injury.

Cell surface-anchored SR-PSOX/CXC chemokine ligand 16 mediates firm adhesion of CXC chemokine receptor 6-expressing cells

Direct contacts between dendritic cells (DCs) and T cells or natural killer T (NKT) cells play important roles in primary and secondary immune responses. SR-PSOX/CXC chemokine ligand 16 (CXCL16), which is selectively expressed on DCs and macrophages, is a scavenger receptor for oxidized low-density lipoprotein and also the chemokine ligand for a G protein-coupled receptor CXC chemokine receptor 6 (CXCR6), expressed on activated T cells and NKT cells. SR-PSOX/CXCL16 is the second transmembrane-type chemokine with a chemokine domain fused to a mucin-like stalk, a structure very similar to that of fractalkine (FNK). Here, we demonstrate that SR-PSOX/CXCL16 functions as a cell adhesion molecule for cells expressing CXCR6 in the same manner that FNK functions as a cell adhesion molecule for cells expressing CX(3)C chemokine receptor 1 (CX(3)CR1) without requiring CX(3)CR1-mediated signal transduction or integrin activation. The chemokine domain of SR-PSOX/CXCL16 mediated the adhesion of CXCR6-expressing cells, which was not impaired by treatment with pertussis toxin, a Galphai protein blocker, which inhibited chemotaxis of CXCR6-expressing cells induced by SR-PSOX/CXCL16. Furthermore, the adhesion activity was up-regulated by treatment of SR-PSOX/CXCL16-expressing cells with a metalloprotease inhibitor, which increased surface expression levels of SR-PSOX/CXCL16. Thus, SR-PSOX/CXCL16 is a unique molecule that not only attracts T cells and NKT cells toward DCs but also supports their firm adhesion to DCs.

Antagonist of monocyte chemoattractant protein 1 ameliorates the initiation and progression of lupus nephritis and renal vasculitis in MRL/lpr mice

OBJECTIVE

To examine whether chemokine antagonists inhibit the initiation and progression of lupus nephritis in MRL/lpr mice.

METHODS

NH(2)-terminal-truncated monocyte chemoattractant protein 1 (MCP-1)/CCL2 or thymus and activation-regulated chemokine (TARC)/CCL17 analogs were inserted into the pCXN2 expression vector and transfected into a nonmetastatic fibroblastoid cell line, MRL/N-1, established from an MRL/gld mouse.

RESULTS

MCP-1 antagonist- or TARC antagonist-transfected MRL/N-1 cells were injected subcutaneously into MRL/lpr mice ages 7 weeks (before the onset of lupus nephritis) and 12 weeks (at the early stage of the disease). After 8 weeks, mice bearing the MCP-1 antagonist showed markedly diminished infiltration of macrophages and T cells, glomerular hypercellularity, glomerulosclerosis, crescent formation, and vasculitis compared with control mice. This seemed to be due to decreased production of interferon-gamma and interleukin-2 in the kidney. In contrast, there was no significant difference in renal damage between mice bearing TARC antagonist and control mice.

CONCLUSION

We established a new system using MRL/N-1 cells that allows long-term observation of the effects of chemokine antagonists on lupus nephritis in MRL/lpr mice. We also showed that the MCP-1 antagonist ameliorated the initiation and progression of lupus nephritis and of renal vasculitis, which might provide a new approach to the treatment of the disease.

Cutting edge: SR-PSOX/CXC chemokine ligand 16 mediates bacterial phagocytosis by APCs through its chemokine domain

SR-PSOX and CXC chemokine ligand (CXCL)16, which were originally identified as a scavenger receptor and a transmembrane-type chemokine, respectively, are indicated to be identical. In this study, we demonstrate that membrane-bound SR-PSOX/CXCL16 mediates adhesion and phagocytosis of both Gram-negative and Gram-positive bacteria. Importantly, our prepared anti-SR-PSOX mAb, which suppressed chemotactic activity of SR-PSOX, significantly inhibited bacterial phagocytosis by human APCs including dendritic cells. Various scavenger receptor ligands inhibited the bacterial phagocytosis of SR-PSOX. In addition, the recognition specificity for bacteria was determined by only the chemokine domain of SR-PSOX/CXCL16. Thus, SR-PSOX/CXCL16 may play an important role in facilitating uptake of various pathogens and chemotaxis of T and NKT cells by APCs through its chemokine domain.

Antitumor effect by interleukin-11 receptor alpha-locus chemokine/CCL27, introduced into tumor cells through a recombinant adenovirus vector

In this study, we examined antitumor activity of a mouse CC chemokine ILC/CCL27 and a mouse CX(3)C chemokine fractalkine/CX(3)CL1 in vivo. We generated recombinant adenovirus vectors with a fiber mutation, encoding mILC (Ad-RGD-mILC) and mFKN (Ad-RGD-mFKN). We confirmed tumor cells infected with Ad-RGD-mILC and Ad-RGD-mFKN to express and release these chemokines. Tumor rejection experiments in vivo were carried out by inoculating OV-HM cells infected with Ad-RGD-mILC or Ad-RGD-mFKN into immunocompetent mice. mILC significantly suppressed the tumor growth, whereas no such significant effect was observed by mFKN. The antitumor activity induced by mILC was T cell dependent, involving both CD4(+) and CD8(+) T cells. Immunohistochemical analysis revealed accumulation of both CD3(+) lymphocytes and NK cells in the tumor tissue transduced with mILC and mFKN. However, there was a significant difference in the distribution of infiltrating cells. Furthermore, mFKN appeared to have an angiogenic activity, which might have masked its tumor suppressive activity. Collectively, ILC/CCL27 may be a good candidate molecule for cancer gene therapy.

Infiltrating CD8+ T cells in oral lichen planus predominantly express CCR5 and CXCR3 and carry respective chemokine ligands RANTES/CCL5 and IP-10/CXCL10 in their cytolytic granules: a potential self-recruiting mechanism

Lichen planus is a chronic inflammatory disease of the skin and oral mucosa in which the cell-mediated cytotoxicity is regarded as a major mechanism of pathogenesis. To understand its pathophysiology further, the present study examined the in situ expression of chemokines and chemokine receptors in oral lichen planus. Immunohistochemical analysis of 15 cases has consistently revealed that infiltrating CD4(+) and CD8(+) T cells in the submucosa predominantly expressed CCR5 and CXCR3. Furthermore, infiltrating T cells, particularly CD8(+) T cells, were positive for RANTES/CCL5 and IP-10/CXCL10, the ligands of CCR5 and CXCR3, respectively. By immunoelectron microscopy, these chemokines were localized in the cytolytic granules of CD8(+) T cells. Lesional keratinocytes also overexpressed the ligands of CXCR3, namely, MIG/CXCL9, CXCL10, and I-TAC/CXCL11. Our data suggest that the chemokines signaling via CCR5 and CXCR3, which are known to be selectively expressed by type 1 T cells, are predominantly involved in T-cell infiltration of oral lichen planus. Furthermore, the presence of CCL5 and CXCL10 in the cytolytic granules of tissue-infiltrating CD8(+) T cells expressing CCR5 and CXCR3 reveals a potential self-recruiting mechanism involving activated effector cytotoxic T cells.

Rap1 translates chemokine signals to integrin activation, cell polarization, and motility across vascular endothelium under flow

Chemokines arrest circulating lymphocytes within the vasculature through the rapid up-regulation of leukocyte integrin adhesive activity, promoting subsequent lymphocyte transmigration. However, the key regulatory molecules regulating this process have remained elusive. Here, we demonstrate that Rap1 plays a pivotal role in chemokine-induced integrin activation and migration. Rap1 was activated by secondary lymphoid tissue chemokine (SLC; CCL21) and stromal-derived factor 1 (CXCL4) treatment in lymphocytes within seconds. Inhibition of Rap1 by Spa1, a Rap1-specific GTPase-activating protein, abrogated chemokine-stimulated lymphocyte rapid adhesion to endothelial cells under flow via intercellular adhesion molecule 1. Expression of a dominant active Rap1V12 in lymphocytes stimulated shear-resistant adhesion, robust cell migration on immobilized intercellular adhesion molecule 1 and vascular cell adhesion molecule 1, and transendothelial migration under flow. We also demonstrated that Rap1V12 expression in lymphocytes induced a polarized morphology, accompanied by the redistribution of CXCR4 and CD44 to the leading edge and uropod, respectively. Spa1 effectively suppressed this polarization after SLC treatment. This unique characteristic of Rap1 may control chemokine-induced lymphocyte extravasation.

Cutting edge: profile of chemokine receptor expression on human plasma cells accounts for their efficient recruitment to target tissues

We systematically examined the repertoire of chemokine receptors expressed by human plasma cells. Fresh bone marrow plasma cells and myeloma cells consistently expressed CXCR4, CXCR6, CCR10, and CCR3. Accordingly, plasma cells responded to their respective ligands in chemotaxis and very late Ag-4-dependent cell adhesion to fibronectin. Immobilized CXC chemokine ligand (CXCL)16, a novel transmembrane-type chemokine and CXCR6 ligand, also directly induced adhesion of plasma cells without requiring G(alpha i) signaling or divalent cations. Furthermore, we revealed consistent expression of CXCL12 (CXCR4 ligand), CXCL16 (CXCR6 ligand), and CC chemokine ligand 28 (CCR10 and CCR3 ligand) in tissues enriched with plasma cells including bone marrow, and constitutive expression of CXCL12, CXCL16, and CC chemokine ligand 28 by cultured human bone marrow stromal cells. Collectively, plasma cells are likely to be recruited to bone marrow and other target tissues via CXCR4, CXCR6, CCR10, and CCR3. CXCR6 may also contribute to tissue localization of plasma cells through its direct binding to membrane-anchored CXCL16.

CCL28 has dual roles in mucosal immunity as a chemokine with broad-spectrum antimicrobial activity

CCL28 is a CC chemokine signaling via CCR10 and CCR3 that is selectively expressed in certain mucosal tissues such as exocrine glands, trachea, and colon. Notably, these tissues commonly secrete low-salt fluids. RT-PCR analysis demonstrated that salivary glands expressed CCL28 mRNA at the highest levels among various mouse tissues. Single cells prepared from mouse parotid glands indeed contained a major fraction of CD3(-)B220(low) cells that expressed CCR10 at high levels and CCR3 at low levels and responded to CCL28 in chemotaxis assays. Morphologically, these cells are typical plasma cells. By immunohistochemistry, acinar epithelial cells in human and mouse salivary glands were strongly positive for CCL28. Furthermore, human saliva and milk were found to contain CCL28 at high concentrations. Moreover, the C terminus of human CCL28 has a significant sequence similarity to histatin-5, a histidine-rich candidacidal peptide in human saliva. Subsequently, we demonstrated that human and mouse CCL28 had a potent antimicrobial activity against Candida albicans, Gram-negative bacteria, and Gram-positive bacteria. The C-terminal 28-aa peptide of human CCL28 also displayed a selective candidacidal activity. In contrast, CCL27, which is most similar to CCL28 and shares CCR10, showed no such potent antimicrobial activity. Like most other antimicrobial peptides, CCL28 exerted its antimicrobial activity in low-salt conditions and rapidly induced membrane permeability in target microbes. Collectively, CCL28 may play dual roles in mucosal immunity as a chemoattractant for cells expressing CCR10 and/or CCR3 such as plasma cells and also as a broad-spectrum antimicrobial protein secreted into low-salt body fluids.

Variations in the human Th2-specific chemokine TARC gene

Th2-specific chemokine thymus and activation-regulated chemokine (TARC)/CC chemokine ligand (CCL)17 is highly implicated in the pathogenesis of Th-2-dominated allergic diseases such as bronchial asthma (BA) and atopic dermatitis (AD). We performed polymorphism screening of the coding and promoter regions of the TARC gene. We found two rare variations in the coding region of exon 3 (2134C>T and 2037G>A) and a single nucleotide polymorphism (SNP) in the 5'-flanking region (-431C>T). Individuals carrying the 431T allele showed significantly increased serum levels of TARC compared with those not carrying the 431T allele, suggesting that this SNP has functional significance. However, when the genotypes at the SNP site were determined for 158 healthy individuals, 105 patients with BA and 148 patients with AD, we observed no significant association of the SNP with susceptibility to BA or AD.

Differential expression of CCL19 by DC-Lamp+ mature dendritic cells in human lymph node versus chronically inflamed skin

De novo formation of lymphoid tissue is one of the characteristic features of chronic inflammation. The formation of T cell-mature dendritic cell (DC) clusters has been previously demonstrated in chronically inflamed skin infected with Candida albicans. A functional similarity was also found between chronic inflammation and the T-cell zone of lymph nodes (LNs), since a substantial fraction of phenotypically mature DCs in both tissues expressed CCL22 (macrophage-derived chemokine; MDC) and were closely surrounded by memory-type T cells expressing its receptor, CCR4. To analyse the nature of T cell-mature DC interactions further in chronically inflamed skin and LNs, the present study focuses on another chemokine system, namely CCL19 (EBI1 ligand chemokine; ELC), CCL21 (secondary lymphoid tissue chemokine; SLC) and their shared receptor, CCR7. RT-PCR analysis revealed expression of CCL19, CCL21, and CCR7 at high levels in LNs and at low levels in inflamed skin. Using immunohistochemistry, the majority of DC-Lamp(+) mature DCs in the T-cell area of LNs expressed CCL19 and were surrounded by CCR7(+) naïve-type lymphocytes, while CCL21 was expressed in reticular stromal cells and vascular endothelial cells. Very few mature DCs in LNs were found to express CCR7. In contrast, the majority of DC-Lamp(+) mature DCs in inflamed skin were totally negative for CCL19 and were surrounded by CCR7(-) memory-type T cells. Furthermore, CCL21 expression in the inflamed skin was detected in dermal lymphatic endothelial cells and rare CCR7(+) mature DCs were mostly seen within the lymphatic vessels. In normal skin, on the other hand, no cells immunoreactive for CCL19, CCL21, or CCR7 were found. The present study thus reveals a striking difference in the function of mature DCs between LNs and chronically inflamed skin.

Comparative DNA sequence analysis of mouse and human CC chemokine gene clusters

The CC chemokines are a closely related subfamily of the chemokine superfamily. Most of the CC chemokine genes form a cluster on chromosome 11 in mice and chromosome 17 in humans. To date, 11 and 16 functional genes have been localized within the mouse and human clusters, respectively. Notably, some of the genes within these clusters appear to have no counterparts between the two species, and the orthologous relationships of some of the genes are difficult to establish solely on the basis of amino acid similarity. In this study, we have taken a comparative genomic approach to reveal some of the features that may be involved in the dynamic evolution of these gene clusters. We sequenced a 122-kb region containing five chemokine genes of the mouse CC cluster. This mouse sequence was combined with those determined by the Mouse Genome Sequencing Project, and the entire sequence of the mouse CC cluster was compared with that of the corresponding cluster in the human genome by percent identity plot and dot-plot analyses. Although no additional chemokine genes have been found in these clusters, our analysis has revealed that numerous gene rearrangements have occurred even after the diversification of rodents and primates, resulting in several species-specific chemokine genes and pseudogenes. In addition, phylogenetic analysis and comparison of the genomic sequences unambiguously identified the orthologous relationships of some of the chemokine genes in the mouse and human CC gene clusters.

Migration of CX3CR1-positive T cells producing type 1 cytokines and cytotoxic molecules into the synovium of patients with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by chronic inflammation of multiple joints. Large numbers of T cells, which produce type 1 cytokines, infiltrate into RA synovium. Chemokines and chemokine receptors are considered to contribute to the T cell infiltration. In this study, we examined the role of CX3CL1/fractalkine and its receptor CX3C chemokine receptor 1 (CX3CR1) in the T cell migration into RA synovium.

METHODS

Using flow cytometry, immunohistochemistry, and reverse transcription-polymerase chain reaction, we analyzed CX3CR1 expression by peripheral blood and synovial T cells, and CX3CL1 expression in synovium from patients with RA. Cytokine and cytotoxic molecule expression by CX3CR1-positive T cells was analyzed by flow cytometry.

RESULTS

CX3CR1 expression by peripheral CD4+ and CD8+ T cells was up-regulated in RA patients. The peripheral CD4+ and CD8+ T cells expressing CX3CR1 predominantly produced interferon-gamma and tumor necrosis factor alpha, and expressed cytotoxic molecules such as granzyme A and perforin. Furthermore, CX3CR1+,CD3+ T cells infiltrated into RA synovium. CX3CL1, the unique ligand of CX3CR1, was expressed by endothelial cells and synoviocytes in RA synovium, but not in osteoarthritis synovium.

CONCLUSION

Our findings suggest that the interactions of CX3CL1 and CX3CR1 might contribute to the accumulation of CX3CR1+ T cells expressing type 1 cytokines and possessing cytotoxic granules in RA synovium.

Frequent low level expression in Ewing sarcoma family tumors and widespread absence of the metastasis suppressor KAI1/CD82 in neuroblastoma

The transmembrane 4 superfamily member KAI1/CD82, a metastasis suppressor, is correlated inversely with the progression and invasion of several tumors. It is capable of inhibiting metastasis without affecting tumorigenicity per se. KAI1/CD82 expression is down-regulated in the progression of common solid epithelial tumors of adulthood. Mutation of p53 is suggested to be involved in the modulation of KAI1. As little is known about its expression and possible prognostic impact in pediatric tumors, we investigated KAI1/CD82 expression in cell lines and primary tumor samples from pediatric tumors of neuroectodermal origin, neuroblastoma and Ewing's sarcoma family tumor. Twenty-four of 29 Ewing's sarcoma family tumor cell lines, independent of p53 status, showed KAI1 mRNA positivity by reverse transcription-PCR analysis in contrast to zero of eight neuroblastoma cell lines. Among 13 primary Ewing's sarcoma family tumor samples from patients with different disease extension, KAI1 mRNA expression was low as detected by reverse transcription-PCR. Twenty of 30 primary neuroblastoma specimens were KAI1-negative by immunofluorescence analysis whereas the remaining 10 gave weak to moderate staining patterns. There was no apparent correlation of KAI1 expression with any clinical or genetic features of the patients whose tumor samples were studied. Consequently, KAI1 may not be of prognostic relevance in this group of tumors although there may be some role for KAI1 modulation in the biology of these neuroectodermal tumors.