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Summary: Immature CD4+CD8+ thymocytes, which are generated in the thymic cortex, are induced upon positive selection to differentiate into mature T lymphocytes and relocate to the thymic medulla. It was recently shown that a chemokine signal via CCR7 is essential for the cortex-to-medulla migration of positively selected thymocytes in the thymus. However, the role of the cortex-to-medulla migration in T cell development and selection has remained unclear. The present study shows that the developmental kinetics and the thymic export of mature thymocytes were undisturbed in adult mice lacking CCR7 or its ligands (CCR7L). The inhibition of sphingosine-1-phosphate-mediated lymphocyte egress from the thymus led to the accumulation of mature thymocytes in the cortex of CCR7- or CCR7L-deficient mice, unlike the accumulation in the medulla of normal mice, thereby suggesting that mature thymocytes may be exported directly from the cortex in the absence of CCR7 signals. However, the thymocytes that were generated in the absence of CCR7 or CCR7L were potent in causing autoimmune dacryoadenitis and sialadenitis in mice and were thus incapable of establishing central tolerance to organ-specific antigens. These results indicate that CCR7-mediated cortex-to-medulla migration of thymocytes is essential for establishing central tolerance rather than for supporting the maturation or export of thymocytes. [Copyright &y& Elsevier]

BCA-1/CXCL13 expression is associated with CXCR5-positive B-cell cluster formation in acute renal transplant rejection.Background. Recent studies showed a crucial role for B cells in acute renal allograft rejection. It remains largely unknown, however, which mechanisms lead to the B-cell recruitment into the allograft. The chemokine CXCL13 and its corresponding receptor CXCR5 play a central role in B-cell trafficking to secondary lymphatic tissue and ectopic B-cell clusters in rheumatoid arthritis. We therefore investigated the potential role of CXCL13 and CXCR5 in formation of B-cell clusters in renal transplant rejection.Methods.Serial immunohistochemical staining for CXCL13, CXCR5, and CD20 was carried out in protocol biopsies of 23 patients obtained between day 4 and day 9 after renal transplantation. Intragraft mRNA expression of CXCL13 was assessed by real-time polymerase chain reaction (PCR) analysis.Results. Of 23 kidney biopsies obtained between days 4 and 9 after renal transplantation, 13 revealed an acute rejection. Four of these patients showed a substantial infiltration of the transplant with cluster-forming B cells. By immunohistochemistry CXCL13 and the corresponding receptor CXCR5 were exclusively detected in areas of B-cell clusters. Intrarenal CXCL13 mRNA expression was 27-fold higher in transplants with B-cell clusters compared to rejecting allografts without B-cell accumulation (P= 0.011).Conclusion. We describe a striking colocalization of CXCL13 expression with CXCR5- and CD20-positive B cells in renal transplants undergoing rejection. This is the first study demonstrating a potential role of CXCL13 and its specific receptor CXCR5 in recruitment of B cells in renal allograft rejection. [ABSTRACT FROM AUTHOR]

The human cytomegalovirus-encoded G protein-coupled receptor homologue US28 binds inflammatory chemokines and sequesters them from the environment of infected cells. Low surface deposition and endocytosis are dependent on constitutive C-terminal phosphorylation, suggesting a requirement for β-arrestin binding in receptor internalization. In this report, a US28-dependent redistribution of β-arrestin into vesicular structures occurred, although internalization of US28 was independent of β-arrestin. Internalization of US28 was dynamin-dependent, and US28 partially partitioned into the detergent-resistant membrane fraction. Endocytosis was diminished by cholesterol depletion, yet sucrose inhibition was even stronger. The relevance of the clathrin-coated pit pathway was supported by colocalization of β2-adaptin and US28 in endocytic compartments. Exchange of the C-terminal dileucine endocytosis motif inhibited rapid endocytosis, indicating a direct interaction of US28 with the AP-2 adaptor complex. We suggest that the arrestin-independent, dynamin-dependent internalization of US28 reveals a differential sorting of β-arrestins and the virally encoded chemokine receptor homologue. [Copyright &y& Elsevier]

Peripheral infection is the natural route of transmission in most prion diseases. Peripheral prion infection is followed by rapid prion replication in lymphoid organs, neuroinvasion and progressive neurological disease. Both immune cells and nerves are involved in pathogenesis, but the mechanisms of prion transfer from the immune to the nervous system are unknown. Here we show that ablation of the chemokine receptor CXCR5 juxtaposes follicular dendritic cells (FDCs) to major splenic nerves, and accelerates the transfer of intraperitoneally administered prions into the spinal cord. Neuroinvasion velocity correlated exclusively with the relative locations of FDCs and nerves: transfer of CXCR5-/- bone marrow to wild-type mice induced perineural FDCs and enhanced neuroinvasion, whereas reciprocal transfer to CXCR5-/- mice abolished them and restored normal efficiency of neuroinvasion. Suppression of lymphotoxin signalling depleted FDCs, abolished splenic infectivity, and suppressed acceleration of pathogenesis in CXCR5-/- mice. This suggests that prion neuroimmune transition occurs between FDCs and sympathetic nerves, and relative positioning of FDCs and nerves controls the efficiency of peripheral prion infection. [ABSTRACT FROM AUTHOR]

Examines the balanced responsiveness to chemoattractants from adjacent zones determines B-cell position. Use of retroviral-mediated gene transfer; Sufficiency of the increased expression of CCR7 to direct B cells to the T zone; Mechanism of B cell relocalization in response to antigen.

Most T lymphocytes are generated within the thymus. It is unclear, however, how newly generated T cells relocate out of the thymus to the circulation. The present study shows that a CC chemokine CCL19 attracts mature T cells out of the fetal thymus organ culture. Another CC chemokine CCL21, which shares CCR7 with CCL19 but has a unique C-terminal extension containing positively charged amino acids, failed to show involvement in thymic emigration. Neonatal appearance of circulating T cells was defective in CCL19-neutralized mice as well as in CCR7-deficient mice but not in CCL21-neutralized mice. In the thymus, CCL19 is predominantly localized in the medulla including endothelial venules. These results indicate a CCL19- and CCR7-dependent pathway of thymic emigration, which represents a major pathway of neonatal T cell export. [Copyright &y& Elsevier]

Investigates the lineage differentiation of memory T cells in immunology. Analysis of cell division that the differentiation of antigen-specific CD8+ T cells is a two-step process characterized initially by a phase of proliferation largely restricted to the CCR7+CD8+ cell subsets, followed by a phase of functional maturation encompassing the CCR7-CD8+ cell subsets; How the results demonstrate a skewed maturation of HIV-specific memory CD8+ T cells during HIV infection.

Presents a study which shows that lymph nodes contain two types of B-cell-rich compartment, follicles containing follicular dendritic cells and areas lacking such cells. Necessity of B-lymphocyte chemoattractant (BLC/BCA1) and its receptor CXC chemokine receptor-5 (CXCR5) for B-cell homing to follicles in the lymph nodes; Requirement of BLC in the development of most lymph nodes and Peyer's patches; Role of BLC in establishing a positive feedback loop that is likely to be important in follicle development and hemeostasis.

Originally published as 401, 708?712; 1999Naive T lymphocytes travel to T-cell areas of secondary lymphoid organs in search of antigen presented by dendritic cells. Once activated, they proliferate vigorously, generating effector cells that can migrate to B-cell areas or to inflamed tissues. A fraction of primed T lymphocytes persists as circulating memory cells that can confer protection and give, upon secondary challenge, a qualitatively different and quantitatively enhanced response. The nature of the cells that mediate the different facets of immunological memory remains unresolved. Here we show that expression of CCR7, a chemokine receptor that controls homing to secondary lymphoid organs, divides human memory T cells into two functionally distinct subsets. CCR7- memory cells express receptors for migration to inflamed tissues and display immediate effector function. In contrast, CCR7+ memory cells express lymph-node homing receptors and lack immediate effector function, but efficiently stimulate dendritic cells and differentiate into CCR7- effector cells upon secondary stimulation. The CCR7+ and CCR7- T cells, which we have named central memory (TCM) and effector memory (TEM), differentiate in a step-wise fashion from naive T cells, persist for years after immunization and allow a division of labour in the memory response. [ABSTRACT FROM AUTHOR]

The Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded chemokine receptor vGPCR acts as an oncogene in Kaposi's sarcomagenesis. Until now, the molecular mechanisms by which the vGPCR contributes to tumor development remain incompletely understood. Here, we show that the KSHV-vGPCR contributes to tumor progression through microRNA (miR)-34a-mediated induction of genomic instability. Large-scale analyses on the DNA, gene and protein level of cell lines derived from a mouse model of vGPCR-driven tumorigenesis revealed that a vGPCR-induced upregulation of miR-34a resulted in a broad suppression of genome maintenance genes. A knockdown of either the vGPCR or miR-34a largely restored the expression of these genes and confirmed miR-34a as a downstream effector of the KSHV-vGPCR that compromises genome maintenance mechanisms. This novel, protumorigenic role of miR-34a questions the use of miR-34a mimetics in cancer therapy as they could impair genome stability.

Multiple myeloma (MM) is an aggressive incurable plasma cell malignancy with a median life expectancy of less than seven years. Antibody-based therapies have demonstrated substantial clinical benefit for patients with hematological malignancies, particular in B cell Non-Hodgkin's lymphoma. The lack of immunotherapies specifically targeting MM cells led us to develop a human-mouse chimeric antibody directed against the B cell maturation antigen (BCMA), which is almost exclusively expressed on plasma cells and multiple myeloma cells. The high affinity antibody blocks the binding of the native ligands APRIL and BAFF to BCMA. This finding is rationalized by the high resolution crystal structure of the Fab fragment in complex with the extracellular domain of BCMA. Most importantly, the antibody effectively depletes MM cells in vitro and in vivo and substantially prolongs tumor-free survival under therapeutic conditions in a xenograft mouse model. A BCMA-antibody-based therapy is therefore a promising option for the effective treatment of multiple myeloma and autoimmune diseases., (Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Unlabelled: In human chronic lymphocytic leukemia (CLL) pathogenesis, B-cell antigen receptor signaling seems important for leukemia B-cell ontogeny, whereas the microenvironment influences B-cell activation, tumor cell lodging, and provision of antigenic stimuli. Using the murine Eμ-Tcl1 CLL model, we demonstrate that CXCR5-controlled access to follicular dendritic cells confers proliferative stimuli to leukemia B cells. Intravital imaging revealed a marginal zone B cell-like leukemia cell trafficking route. Murine and human CLL cells reciprocally stimulated resident mesenchymal stromal cells through lymphotoxin-β-receptor activation, resulting in CXCL13 secretion and stromal compartment remodeling. Inhibition of lymphotoxin/lymphotoxin-β-receptor signaling or of CXCR5 signaling retards leukemia progression. Thus, CXCR5 activity links tumor cell homing, shaping a survival niche, and access to localized proliferation stimuli., Significance: CLL and other indolent lymphoma are not curable and usually relapse after treatment, a process in which the tumor microenvironment plays a pivotal role. We dissect the consecutive steps of CXCR5-dependent tumor cell lodging and LTβR-dependent stroma-leukemia cell interaction; moreover, we provide therapeutic solutions to interfere with this reciprocal tumor-stroma cross-talk., (©2014 American Association for Cancer Research.)

Bispecific antibodies are promising agents for immunotherapy. Here, we describe a quadroma-based trifunctional bispecific antibody binding the chemokine receptor CXCR5 and the T-cell antigen CD3 that efficiently prevents tumor growth in a mouse B-cell lymphoma model. CXCR5 regulates the tissue homeostasis of mature B cells and is highly expressed on B-cell non-Hodgkin and lymphocyte-predominant Hodgkin lymphoma, as well as on a subset of CD4(+) T cells known as follicular T-helper cells. In vitro, the bispecific CXCR5::CD3 antibody efficiently recruited effector T cells to CXCR5 expressing B cells and induced a co-stimulation-independent activation of CD8(+) and CD4(+) T cells as demonstrated by the de novo expression of CD25 and CD69, and secretion of the cytokines IFN-γ, TNF-α, IL-6 and IL-10 by peripheral blood mononuclear cells. Notably, at low antibody concentrations, CXCR5::CD3 displayed a significantly higher cytotoxic activity against autologous B cells than its parental antibodies or rituximab. In vivo imaging revealed that CXCR5::CD3 and its parental CXCR5 antibody efficiently prevent tumor growth in a xenograft model of B-cell lymphoma in mice and prolong their survival. Taken together, our results identify CXCR5 as a promising target for antibody-based therapies in the treatment of B-cell malignancies., (© 2014 UICC.)

Infection with helminths and exposure to antigens induce a strong type 2 immune response resulting in the secretion of the cytokines IL-4 and IL-13 by CD4(+) T cells and several innate cell types. IL-4 and IL-13 promote class switch recombination to IgG1 and IgE while their role for germinal center (GC) formation is poorly understood. We found a dramatic reduction in the numbers of GC B cells when investigating different type 2 immune responses in IL-4/IL-13-deficient mice. IL-4/IL-13 from T cells located outside B-cell follicles was sufficient for GC formation. We further revealed that IL-4/IL-13 acts directly on B cells for the formation of a robust GC response. The frequency of apoptotic GC B cells was not altered in the absence of IL-4/IL-13 and proliferation was even enhanced. However, deficiency of signal transducer and activator of transcription 6 signaling in B cells resulted in failure to downregulate the chemotactic receptor Gpr183 (Ebi2) and downregulation of this receptor has been shown to be essential for proper GC B-cell differentiation. Thus, T-cell-derived extrafollicular IL-4/IL-13 and signal transducer and activator of transcription 6-regulated genes in B cells play a critical role for orchestration of the GC response in type 2 immunity., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Maturation of high-affinity B lymphocytes is precisely controlled during the germinal center reaction. This is dependent on CD4(+)CXCR5(+) follicular helper T cells (TFH) and inhibited by CD4(+)CXCR5(+)Foxp3(+) follicular regulatory T cells (TFR). Because NFAT2 was found to be highly expressed and activated in follicular T cells, we addressed its function herein. Unexpectedly, ablation of NFAT2 in T cells caused an augmented GC reaction upon immunization. Consistently, however, TFR cells were clearly reduced in the follicular T cell population due to impaired homing to B cell follicles. This was TFR-intrinsic because only in these cells NFAT2 was essential to up-regulate CXCR5. The physiological relevance for humoral (auto-)immunity was corroborated by exacerbated lupuslike disease in the presence of NFAT2-deficient TFR cells.

DNA vaccines are potential tools for the induction of immune responses against both infectious disease and cancer. The dermal application of DNA vaccines is of particular interest since the epidermal and dermal layers of the skin are characterized by an abundance of antigen-presenting cells (APCs). The aim of our study was to compare tumor protection as obtained by two different methods of intradermal DNA delivery (gene gun and jet injector) in a well-established HER2/neu mouse tumor model. BALB/c mice were immunized twice with a HER2/neu-coding plasmid by gene gun or jet injector. Mice were then subcutaneously challenged with HER2/neu(+) syngeneic D2F2/E2 tumor cells. Protection against subsequent challenges with tumor cells as well as humoral and T-cell immune responses induced by the vaccine were monitored. Gene gun immunization was far superior to jet injector both in terms of tumor protection and induction of HER2/neu-specific immune responses. After gene gun immunization, 60% of the mice remained tumor-free until day 140 as compared with 25% after jet injector immunization. Furthermore, gene gun vaccination was able to induce both a strong T(H)1-polarized T-cell response with detectable cytotoxic T-lymphocyte (CTL) activity and a humoral immune response against HER2/neu, whereas the jet injector was not. Although the disadvantages that were associated with the use of the jet injector in our model may be overcome with methodological modifications and/or in larger animals, which exhibit a thicker skin and/or subcutaneous muscle tissue, we conclude that gene gun delivery constitutes the method of choice for intradermal DNA delivery in preclinical mouse models and possibly also for the clinical development of DNA-based vaccines.

Background: DNA vaccination is an attractive approach for tumor vaccination because plasmid DNA (pDNA) can be used as a 'general vaccine' across major histocompatibility complex barriers. Coexpression of immunomodulatory molecules can help to amplify the immunogenicity of DNA vaccines. CCL19 (ELC) is a CC chemokine with immunoregulatory properties, binding to the chemokine receptor CCR7 that is expressed on dendritic cells (DCs) and T cells. In vivo, CCL19 is a key regulator for the interactions between DCs and T cells in regional lymph nodes., Methods: pDNA encoding Her2/neu and CCL19 was used as an intramuscular vaccine. Vaccination was performed in BALB/c mice, which were subsequently challenged with syngeneic Her2/neu(+) tumor cells. Groups of mice were immunized with pDNA(Her2/neu) plus pDNA(CCL19), pDNA(Her2/neu) plus pDNA(CCL19) plus pDNA(GM-CSF), pDNA(Her2/neu) plus pDNA(GM-CSF), pDNA(Her2/neu), pDNA(CCL19), pDNA(GM-CSF) or mock vector. Tumor protection by the vaccine and immune responses were monitored., Results: Coadministration of pDNA(Her2/neu) and pDNA(CCL19) led to substantial improvement of tumor protection by the vaccine and induced a TH1-polarized, Her2/neu-specific immune response. Forty-seven days after the tumor challenge, 58% of the mice coinjected with pDNA(Her2/neu) and pDNA(CCL19) remained tumor-free compared to 22% after vaccination with pDNA(Her2/neu) alone. Additional administration of pDNA(GM-CSF) led to further improvement of tumor protection and an amplification of Her2/neu-specific immune responses., Conclusions: CCL19 is able to induce a TH-1 polarization of the anti-Her2/neu immune response, which can be further amplified by granulocyte macrophage-colony-stimulating factor (GM-CSF). Clinical use of a pDNA(Her2/neu-CCL19 ± GM-CSF) vaccine might be promising in Her2/neu + breast cancer in the clinical situation of minimal residual disease., (Copyright © 2012 John Wiley & Sons, Ltd.)

Background & Aims: Antigen-presenting cells (APCs) are involved in the induction of liver inflammation. We investigated the roles of specific APCs in the pathogenesis of acute liver injury in mice., Methods: We used concanavalin A (con A) or carbon tetrachloride to induce acute liver inflammation in mice and studied the roles of macrophages that express CCR9., Results: After injection of con A, we detected CCR9(+)CD11b(+)CD11c(-) macrophages that express tumor necrosis factor (TNF)-α in livers of mice, whereas CCR9(+)Siglec-H(+)CD11b(-)CD11c(low) plasmacytoid DCs (pDCs), which are abundant in normal livers, disappeared. The CCR9(+) macrophages were also detected in the livers of RAG-2(-/-) mice, which lack lymphocytes and natural killer T cells, after injection of con A. Under inflammatory conditions, CCR9(+) macrophages induced naive CD4(+) T cells to become interferon gamma-producing Th1 cells in vivo and in vitro. CCR9(-/-) mice injected with con A did not develop hepatitis unless they also received CCR9(+) macrophages from mice that received con A; more CCR9(+) macrophages accumulated in their inflamed livers than CCR9(+) pDCs, CCR9(-) pDCs, or CCR9(-) macrophages isolated from mice that had received injections of con A. Levels of CCL25 messenger RNA increased in livers after injection of con A; neutralizing antibodies against CCL25 reduced the induction of hepatitis by con A by blocking the migration of CCR9(+) macrophages and their production of TNF-α. Peripheral blood samples from patients with acute hepatitis had greater numbers of TNF-α-producing CCR9(+)CD14(+)CD16(high) monocytes than controls., Conclusions: CCR9(+) macrophages contribute to the induction of acute liver inflammation in mouse models of hepatitis., (Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Forkhead box p3-positive (Foxp3(+)) regulatory T cells (T(reg) cells) participate in maintaining peripheral immune tolerance and suppressing autoimmunity. We recently reported that in situ patrolling by C-C-chemokine receptor 7 (CCR7)(+) T(reg) cells in target organs is essential for controlling autoimmune lesions in Sjögren's syndrome. In the present study, the molecular mechanism underlying CCR7-mediated T(reg) cell migration was investigated in a mouse model. The impaired migratory response of Ccr7(-/-) T(reg) cells to sphingosine 1-phosphate (S1P) occurred because of defective association of S1P receptor 1 (S1P(1)) with a G coupled-protein. In addition, T-cell receptor (TCR)- and S1P(1)-mediated Ras-related C3 botulinum toxin substrate 1 (Rac-1), extracellular signal-related kinase (ERK), and c-Jun phosphorylation required for activator protein 1 (AP-1) transcriptional activity were significantly impaired in Ccr7(-/-) T(reg) cells. Surprisingly, the abnormal nuclear localization of Foxp3 was detected after abrogation of the c-Jun and Foxp3 interaction in the nucleus of Ccr7(-/-) T(reg) cells. These results indicate that CCR7 essentially controls the migratory function of T(reg) cells through S1P(1)-mediated AP-1 signaling, which is regulated through its interaction with Foxp3 in the nucleus., (Copyright © 2012 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Background & Aims: The egress of memory T cells from peripheral tissues, such as lung and skin, into the draining lymph nodes requires their expression of CC chemokine receptor 7 (CCR7). In the intestine, resident memory T cells in the intestinal lamina propria (LP) do not express CCR7, indicating that they are tissue bound and do not exit the intestine., Methods: We developed a cell transfer system, using rectal administration of lymphocytes to C57BL/6 mice. Lymphotoxin α-deficient mice were crossed with RAG-2(-/-) (recombination-activating gene-2) mice to generate lymphotoxin α-deficient × RAG-2(-/-) mice., Results: Severe combined immunodeficient (SCID) or RAG-2(-/-) mice given rectal administration of splenic CD4(+) T cells from normal mice developed colitis; the cells proliferated not only in the LP but also in spleen. SCID or RAG-2(-/-) mice given rectal administrations of CD4(+) T cells that expressed green fluorescent protein (GFP(+)CD4(+) T cells) localized to the LP within 6 hours but were not found in the spleen until 24 hours after administration. Immunohistochemical and electron microscopic analyses detected CD4(+) T cells in the intraepithelial space just 3 hours after intrarectal administration. However, neither CCR7 deficiency nor the sphingosine-1-phosphate receptor agonist Fingolimod impaired the egress of CD4(+) T cells from LP to systemic circulation., Conclusions: CD4(+) T cells not only penetrate from the luminal side of the intestine to the LP but also actively egress from the LP into the circulation. We developed a rectal administration system that might be used to further investigate cell trafficking in intestinal mucosa and to develop enema-based therapeutics for intestinal diseases., (Copyright © 2011 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Although predominantly expressed on lymphocytic and hematopoietic cells, the role of sphingosine-1-phospate receptor 4 (S1P(4)) in immune homeostasis is still poorly understood. In this report, we used a S1P(4)-deficient murine model to characterize the biological role of S1P(4)-mediated S1P signaling in the immune system. S1p(4)(-/-) animals showed normal peripheral lymphocyte numbers and a regular architecture of secondary lymphoid organs. Interestingly, S1P(4) only marginally affects T-cell function in vivo. In contrast, dendritic cell (DC) migration and cytokine secretion are profoundly affected by S1P(4) deficiency. Lack of S1P(4) expression on DCs significantly reduces T(H)17 differentiation of T(H) cells. Furthermore, in various in vivo models of T(H)1- or T(H)2-dominated immune reactions, S1P(4) deficiency consistently increased the amplitude of T(H)2-dominated immune responses, while those depending on T(H)1-dominated mechanisms were diminished. Finally, S1p(4)(-/-) mice showed decreased pathology in a model of dextran sulfate sodium-induced colitis. In summary, for the first time, we show that S1P(4) signaling is involved in the regulation of DC function and T(H)17 T-cell differentiation. S1P(4)-mediated S1P signaling also modifies the course of various immune diseases in a murine model. We propose that S1P(4) may constitute an interesting target to influence the course of various autoimmune pathologies.

Tolerance to self-antigens expressed in peripheral organs is maintained by CD4(+) CD25(+) Foxp3(+) Treg cells, which are generated as a result of thymic selection or peripheral induction. Here, we demonstrate that steady-state migratory DCs from the skin mediated Treg conversion in draining lymph nodes of mice. These DCs displayed a partially mature MHC II(int) CD86(int) CD40(hi) CCR7(+) phenotype, used endogenous TGF-β for conversion and showed nuclear RelB translocation. Deficiency of the alternative NF-κB signaling pathway (RelB/p52) reduced steady-state migration of DCs. These DCs transported and directly presented soluble OVA provided by s.c. implanted osmotic minipumps, as well as cell-associated epidermal OVA in transgenic K5-mOVA mice to CD4(+) OVA-specific TCR-transgenic OT-II T cells. The langerin(+) dermal DC subset, but not epidermal Langerhans cells, mediated conversion of naive OT-II×RAG-1(-/-) T cells into proliferating CD4(+) CD25(+) Foxp3(+) Tregs. Thus, our data suggest that steady-state migratory RelB(+) TGF-β(+) langerin(+) dermal DCs mediate peripheral Treg conversion in response to epidermal antigen in skin-draining lymph nodes., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mediastinal large B-cell lymphomas (MLBCLs) are considered as a subtype of diffuse large B-cell lymphoma; however, they exhibit completely different patterns of dissemination. Since they share a number of surface markers with thymic B cells, a close relationship was assumed. MLBCLs arise extranodally within the anterior mediastinum and have a low propensity to metastasize. To address the preferential positioning of MLBCL, we focused on homeostatic chemokines involved in B-cell compartmental homing in secondary lymphoid organs, which are also capable of shaping lymphoid niches in ectopic sites. Here, we applied immunohistochemistry to assess chemokine receptor and ligand expression in situ. Flow cytometry was used to identify the chemokine receptor profile on an MLBCL-derived cell line, Karpas1106 and on thymic B cells. Migration assays were performed to examine functionality of chemokine receptors. Electrophoretic mobility shift assay was applied to score for NF-kappaB activity. Using immunohistochemistry, we obtained an unexpectedly low-expression frequency for the chemokine receptors CXCR5 and CCR7 in primary lesions. Although the mature B-cell marker CCR6 was absent in most cases, the lineage aberrant marker CCR9 emerged in the majority of MLBCL cases. Given the role of NF-kappaB in the transcriptional activation of CCR7, we identified the involvement of the noncanonical activation pathway in MLBCLs. MLBCLs exhibit a diagnostic chemokine receptor profile that is instrumental in the discrimination from diffuse large B-cell lymphoma not otherwise specified and classical Hodgkin lymphoma. Furthermore, we suggest that low-abundance expression of CCR7 and CXCR5 may hinder lymphoma cells from nodal dissemination.

CCL19 and CCL21 are thought to be critical for experimental autoimmune encephalomyelitis (EAE) induction, but their precise role is unknown. We examined the role of these chemokines in inducing EAE. C57BL/6 mice lacking expression of these chemokines (plt/plt mice) or their receptor CCR7 were resistant to EAE induced with myelin oligodendrocyte glycoprotein peptide 35-55 (MOG(35-55)) and pertussis toxin. However, passive transfer of pathogenic T cells from wild-type mice induced EAE in plt/plt mice, suggesting a defect independent of the role of CCR7 ligands in the migration of immune cells. Examination of draining lymph node (DLN) cells from MOG(35-55)-immunized plt/plt mice found decreased IL-23 and IL-12 production by plt/plt dendritic cells (DCs) and a concomitant defect in Th17 cell and Th1 cell generation. In contrast, production of the Th17 lineage commitment factors IL-6 and TGF-beta were unaffected by loss of CCR7 ligands. The adoptive transfer of in vitro-generated Th17 cells from DLN cells of MOG(35-55)-immunized plt/plt mice developed EAE in wild-type recipient mice, whereas that of Th1 cells did not. Pathogenic Th17 cell generation was restored in plt/plt DLNs with the addition of exogenous IL-23 or CCL19/CCL21 and could be reversed by inclusion of anti-IL-23 mAb in cultures. Exogenous CCL19/CCL21 induced IL-23p19 expression and IL-23 production by plt/plt or wild-type DCs. Therefore, CCR7 ligands have a novel function in stimulating DCs to produce IL-23 and are important in the IL-23-dependent generation of pathogenic Th17 cells in EAE induction.

Naive T cells are stimulated by antigen-presenting dendritic cells (DCs) in secondary lymphoid organs, but whether other types of cell participate in T cell priming is unclear. Here we show in mice that natural killer (NK) cells, which are normally excluded from lymph nodes, are rapidly recruited in a CCR7-independent, CXCR3-dependent manner to lymph nodes on stimulation by the injection of mature DCs. Recruitment of NK cells is also induced by some, but not all, adjuvants and correlates with the induction of T helper cell type 1 (T(H)1) responses. NK cell depletion and reconstitution experiments show that NK cells provide an early source of interferon-gamma (IFN-gamma) that is necessary for T(H)1 polarization. Taken together, our results identify an induced pathway of NK cell migration in antigen-stimulated lymph nodes and a mechanism by which some adjuvants may facilitate T(H)1 responses.

Sphingosine 1-phosphate (S1P) receptors represent a novel subfamily of G-protein-coupled receptors binding S1P specifically and with high affinity. Although their in vivo functions remain largely unknown, in vitro extracellular application of S1P induces distinct S1P receptor-dependent cellular responses including proliferation, differentiation, and migration. We have analyzed signaling pathways engaged by S1P(4), which is highly expressed in the lymphoid system. Here we show that S1P(4) couples directly to Galpha(i) and even more effectively to Galpha(12/13)-subunits of trimeric G-proteins, but not to Galpha(q) unlike other S1P receptors. Consequently, CHO-K1 cells ectopically expressing S1P(4) potently activate the small GTPase Rho and undergo cytoskeletal rearrangements, inducing peripheral stress fiber formation and cell rounding, upon S1P stimulation. Overexpression of S1P(4) in Jurkat T cells induces pertussis toxin-sensitive cell motility even in the absence of exogenously added S1P. In addition, S1P(4) is internalized upon binding of S1P. The capacity of S1P(4) to mediate cellular responses, such as motility and shape change through Galpha(i)- and Galpha(12/13)-coupled signaling pathways may be important for its in vivo function which is currently under investigation., (Copyright 2003 Wiley-Liss, Inc.)

Chemokines are essential regulators of lymphocyte migration throughout the body. The chemokine system controls lymphocyte recirculation in immune-system homeostasis, as well as the activation-dependent and tissue-selective trafficking of effector and memory lymphocytes during immune responses. In addition, there is now substantial evidence that chemokines are critical factors for the development and organization of secondary lymphoid organs and that they are involved in all stages of lymphoid organogenesis.

To defend the host from malignancies, the immune system can spontaneously raise CD8(+) T-cell responses against tumor antigens. Investigating the functional state of tumor-reactive cytolytic T cells in cancer patients is a key step for understanding the role of these cells in tumor immunosurveillance and for evaluating the potential of immunotherapeutic approaches of vaccination against cancer. In this study we identified a subset of circulating tumor-reactive CD8(+) T lymphocytes, which specifically secreted IFN-gamma after exposition to autologous tumor cell lines in stage IV metastatic melanoma patients. Additional phenotypic characterization using multicolor flow cytometry revealed that a significant fraction of these cells were CD45RA(+)CCR7(-), a phenotype that has been proposed recently to characterize cytolytic effectors potentially able to home into inflamed tissues. In the case of an HLA-A2-expressing patient, the antigen specificity of this population was identified by using HLA-A2/peptide multimers incorporating a tyrosinase-derived peptide. Consistently with their phenotypic characteristics, A2/tyrosinase peptide multimer(+) CD8(+) T cells, isolated by cell sorting, were directly lytic ex vivo and able to specifically recognize tyrosinase-expressing tumor cells. Overall, these results provide the first evidence that a proportion of melanoma patients have circulating tumor-reactive T cells, which are lytic effectors cells.