Background. The chemokine receptor CCR7 plays a pivotal role in the homing of naïve T cells and regulatory T cells to secondary lymphoid organs and the migration of dendritic cells into afferent lymphatic vessels. Antigen presentation, T cell recruitment, and expansion of regulatory cells are crucial events in establishing and controlling chronic allograft dysfunction. In this study, we report an important role for chemokine receptor CCR7 in the development of transplant arteriosclerosis. Methods. Fully major histocompatibility complex-mismatched CBA (H2k) donor aortas were transplanted into BALB/c-CCR7−/− (H2d), BALB/c-CCR7+/− (H2d), or BALB/c-CCR7+/+ (H2d) recipients. Grafts were analyzed by histology, morphometry, and immunofluorescence on day 30 after transplantation. Intragraft cytokine mRNA production was analyzed by realtime polymerase chain reaction on day 14 after transplantation. Results. After implanting fully major histocompatibility complex-mismatched donor aortas into CCR7-deficient recipients, transplant arteriosclerosis was significantly elevated. CD4 depletion resulted in a reduction of intima proliferation in CCR7−/− recipients whereas CD8 depletion had no effect. Analysis of aortic grafts from CCR7−/− recipients revealed high numbers of infiltrating CD4+, F4/80+, and CD205+ cells. Furthermore, intragraft cytokine production showed higher levels of interleukin-4, interleukin-12, and eotaxin mRNA expression, whereas significantly lower Foxp3 mRNA expression was observed in CCR7−/− recipients. Conclusion. These data suggest that although alloantigen presentation in secondary lymphoid organs is hampered in CCR7-deficient recipients, this process may take place within the allograft itself, leading to increased formation of transplant arteriosclerosis. The decrease in Foxp3 expression despite increased in CD4+ T cell infiltration indicates a reduction in T regulatory cells possibly influencing the intensity of the graft rejection.

Chemokine receptors and their ligands are crucial for lymphocyte trafficking under both homeostatic and inflammatory conditions. The chemokine receptor CXCR5 controls B cell migration and the organization of B cell follicles. The aim of this study was to investigate the impact of CXCR5 on the development of transplant arteriosclerosis. Fully MHC mismatched BALB/c (H2d) donor aortas were transplanted into C57BL/6-CXCR5−/− (H2b), C57BL/6-CXCR5+/− (H2b) or C57BL/6-CXCR5+/+ (H2b) recipients. Grafts were analysed by morphometry and immunofluorescence and intra-graft cytokine mRNA production was analysed by RT-PCR. Transplant arteriosclerosis was evident in CXCR5+/+ and CXCR5+/− mice and only mildly reduced in CXCR5−/− recipients indicating that absence of CXCR5 had no substantial effect on the development of transplant arteriosclerosis. Analysis of the cellular infiltrate of aortic grafts implanted in CXCR5−/− recipients revealed no differences in the number of T-cells, macrophages and B cells as compared to controls. Intra-graft cytokine production showed no significant changes in Th1 (IL-12) and Th2 (IL-4) cytokines as well as in TGF-β and iNOS production. These data suggest that lack of CXCR5 expression by recipient T- and B-cells has little effect on the development of transplant arteriosclerosis.

Presence and extent of bronchus-associated lymphoid tissue (BALT) is subject to considerable variations between species and is only occasionally observed in lungs of mice. Here we demonstrate that mice deficient for the chemokine receptor CCR7 regularly develop highly organized BALT. These structures were not present at birth but were detectable from day 5 onwards. Analyzing CCR7(-/-)/wild-type bone marrow chimeras, we demonstrate that the development of BALT is caused by alterations of the hematopoietic system in CCR7-deficient mice. These observations together with the finding that CCR7-deficient mice possess dramatically reduced numbers of regulatory T cells (T reg cells) in the lung-draining bronchial lymph node suggest that BALT formation might be caused by disabled in situ function of T reg cells. Indeed, although adoptive transfer of wild-type T reg cells to CCR7-deficient recipients resulted in a profound reduction of BALT formation, neither naive wild-type T cells nor T reg cells from CCR7(-/-) donors impair BALT generation. Furthermore, we provide evidence that CCR7-deficient T reg cells, although strongly impaired in homing to peripheral lymph nodes, are fully effective in vitro. Thus our data reveal a CCR7-dependent homing of T reg cells to peripheral lymph nodes in conjunction with a role for these cells in controlling BALT formation.

Background The chemokine receptor CCR7 is a key organizer of the immune system. Gene targeting in mice revealed that Ccr7-deficient animals are severely impaired in the induction of central and peripheral tolerance. Due to these defects, Ccr7-deficient mice spontaneously develop multi-organ autoimmunity showing symptoms similar to those observed in humans suffering from connective tissue autoimmune diseases. However, it is unknown whether mutations of CCR7 are linked to autoimmunity in humans. Results DNA samples were collected from 160 patients suffering from connective tissue autoimmune disease (Sjogren's syndrome, n = 40; systemic lupus erythematosus, SLE, n = 20 and systemic sclerosis, n = 100) and 40 health subjects (n = 40). All participants in this study were of German descent. Samples were screened for single nucleotide polymorphisms (SNP) by sequencing the coding region of the CCR7 gene as well asthe exon flaking intron sites and parts of the regions encoding for the 5'- and 3'-UTR. CCR7 variants were rare. We identified six different sequence variants, which occurred in heterozygosis. The identified SNP were observed at position -60 C/T (observed 1x), +6,476 A/G (7x), +6,555 C/T (15x), +6,560 C/T (6x), +10,440 A/G (3x) and +11,475 C/A (1x). Four of these variants (+6,476 A/G, +6,555 C/T, +6,560 C/T and +10,440 A/G) display allelic frequencies between 1% and 5 % and were present in both patients and control groups. The variants +6,476 A/G, +6,555 C/T, +6,560 C/T are located in the intron 2, while the +10,440 A/G variant corresponds to a silent mutation in exon 3. The variants -60 C/T and +11,475 C/A which are located at the 5'-UTR and 3-UTR respectively, display allelic frequencies below 1%. No correlation between these variants and the autoimmune diseases investigated could be observed. However, reporter gene expression assay demonstrated that the mutation at the -60 C/T position in homozygosis leads to reduced luciferase activity. Conclusion These results suggest that variants of CCR7 gene occur at an extremely low frequency in the German population and that neither Sjogren's syndrome, systemic lupus erythematosus, nor systemic sclerosis are associated with these variants. Nevertheless, the decreased luciferase activity observed in cells transfected with the promoter region bearing the -60 C/T mutation suggests that this CCR7 variant could potentially lead to increased susceptibility to autoimmunity.

Efficient strategies for labelling and delivery of bone marrow derived stem cells (BMCs) are required to elucidate the cellular kinetics and therapeutic effects after BMC transfer for myocardial infarction (MI). Lineage negative (lin-) BMCs, labelled ex vivo in a simple procedure with the cell tracker dye tetramethyl-rhodamine (TAMRA), were reliably detected by fluorescence microscopy with higher specificity than retroviral enhanced green fluorescence protein (EGFP) marking and detection. Only few cells entered the ischemic myocardium after intravenous (i.v.) application, but this number increased more than 18-fold after transcoronary delivery. Time course and kinetic analysis over 12 h revealed that myocardial colonization seems to be a biphasic process of first order decay with different elimination half-lives. Most cells are eliminated rapidly during the first 2 h (t1/2 40 min), but the remaining cells are retained significantly longer in the ischemic heart (t1/2 5.2 h). In contrast, BMC colonization of the spleen increased rather in a linear fashion. Although transcoronary BMC transfusion did not alter infarct size, it increased capillary density in the infarct border zone and improved LV function 4 weeks after MI. In conclusion, BMCs delivered by transcoronary injection increase capillary density and improve LV function after MI although homing to the ischemic heart is only transient.

Introduction: The chemokine receptor CCR7 plays a pivotal role in the recruitment of native T cells and antigen-activated dendritic cells (DCs) to secondary lymphoid organs. As antigen presentation and T cell recruitment are crucial events in allograft rejection, the aim of this study was to investigate the impact of CCR7 on the development of transplant arteriosclerosis.

Allergic airway diseases such as asthma are caused by a failure of the immune system to induce tolerance against environmental Ags. The underlying molecular and cellular mechanisms that initiate tolerance are only partly understood. In this study, we demonstrated that a CCR7-dependent migration of both CD103+ and CD103− lung dendritic cells (DC) to the bronchial lymph node (brLN) is indispensable for this process. Although inhaled Ag is amply present in the brLN of CCR7-deficient mice, T cells cannot be tolerized because of the impaired migration of Ag-carrying DC and subsequent transport of Ag from the lung to the draining lymph node. Consequently, the repeated inhalation of Ag protects wild-type but not CCR7-deficient mice from developing allergic airway diseases. Thus, the continuous DC-mediated transport of inhaled Ag to the brLN is critical for the induction of tolerance to innocuous Ags.

Allergic airway diseases such as asthma are caused by a failure of the immune system to induce tolerance against environmental Ags. The underlying molecular and cellular mechanisms that initiate tolerance are only partly understood. In this study, we demonstrated that a CCR7-dependent migration of both CD103+ and CD103- lung dendritic cells (DC) to the bronchial lymph node (brLN) is indispensable for this process. Although inhaled Ag is amply present in the brLN of CCR7-deficient mice, T cells cannot be tolerized because of the impaired migration of Ag-carrying DC and subsequent transport of Ag from the lung to the draining lymph node. Consequently, the repeated inhalation of Ag protects wild-type but not CCR7-deficient mice from developing allergic airway diseases. Thus, the continuous DC-mediated transport of inhaled Ag to the brLN is critical for the induction of tolerance to innocuous Ags.

Introduction: The chemokine receptor CCR7 plays a pivotal role in the recruitment of T cells and dendritic cells to secondary lymphoid organs. In contrast, CXCR5 controls B cell migration and the organization of B cell follicles. The aim of this study was to investigate the impact of CCR7 and CXCR5 on the development of transplant arteriosclerosis (TxA).

The production of high-affinity antibodies to T-dependent antigens requires the interaction of B cells and T helper cells expressing receptors specific for the same antigen. Although several mechanisms have been elucidated that regulate B-cell trafficking within lymphoid organs, less is known about molecular cues that guide the small subpopulation of CD4+ follicular T helper cells to B-cell follicles. Using adoptive transfer of transgenic T cells in mice, we demonstrate that antigen-induced activation leads to a finely tuned positioning of T cells either to the T-cell area or the B-cell follicle. We show that expression of CXCR5 is indispensable for T cells to enter B-cell follicles, whereas expression of CCR7 provides a counteracting signal to retain activated T cells in the T-cell area. Although only few T cells transiently migrate from the T-cell area to the B-cell follicle of peripheral lymph nodes following antigenic challenge, this step is essential to provide the help B cells require to produce antibodies efficiently. Thus, we demonstrate that the balanced expression of CCR7 and CXCR5 determines the positioning and proper function of follicular T helper cells.

T cell differentiation in the adult thymus depends on sequential interactions between lymphoid progenitors and stromal cells found in distinct regions of the cortex and medulla. Therefore, migration of T cell progenitors through distinct stromal environments seems to be a crucial process regulating differentiation and homeostasis inside the thymus. Here we show that CCR7-deficient mice are distinguished by a disturbed thymic architecture, impaired T cell development, and decreased numbers of the thymocytes. Analysis of developing double negative (CD4−CD8−) pool of wild-type thymus reveals that CCR7 expression is restricted to a CD25intCD44+ subpopulation. Correspondingly, CCR7 deficiency results in an accumulation of this population in mutant thymus. Furthermore, immunohistology shows that in CCR7-deficient mice CD25+CD44+ cells accumulate at the cortico-medullary junction, suggesting that CCR7 signaling regulates the migration of early progenitors toward the outer thymic cortex, thereby continuing differentiation. Results obtained from mixed bone marrow chimeras support this view, since the development of CCR7-deficient thymocytes is also disturbed in a morphologically intact thymus. Thus, our findings establish an essential role for CCR7 in intrathymic migration and proper T cell development.

Initiation of an antitumour immune response is characterized by a complex process of chemokine-mediated cell migration and cell-cell interactions. Overexpression of chemokine CCL19 in tumour cells has been shown to result in accelerated tumour rejection under certain experimental conditions, suggesting a novel approach in the therapy of neoplastic malignancies. To investigate CCL19-mediated modulations of cellular immune responses in vivo, we generated a chimeric CCL19-immunoglobulin G2b (IgG2b) Fc fusion protein, which binds to the chemokine receptor CCR7 comparable to native CCL19. CCL19-IgG2b possesses a long-lasting potent chemotactic activity as a result of the extended half-life of Fc fusion proteins. Stable overexpression of CCL19-IgG2b in BALB/c-derived J558L tumour cells fails to support tumour cell rejection following transplantation in syngeneic mice. Moreover, overexpression of CCL19-IgG2b hinders tumour rejection in allogeneic C57BL/6 mice. This phenomenon was accompanied by a six-fold increase of dendritic cells (DCs) isolated from CCL19-IgG2b-secreting tumours when compared to the number of DCs isolated from control parental J558L tumours. While mice bearing the allogeneic parental tumour showed an intense hypercellularity in the draining lymph nodes, no such response could be observed in the draining lymph nodes of mice carrying the CCL19-IgG2b-secreting tumour. We could demonstrate that overexpression of CCL19-IgG2b in tumour cells retains antigen-presenting cells in the tumour mass and prevents DCs from migrating into draining lymph nodes to present antigens and to activate T cells, resulting in an impaired immune response against the tumour.

Introduction: The chemokine receptor CCR7 has been shown to play a pivotal role in the recruitment of native T cells and antigen-activated dendritic cells (DCs) to secondary lymphoid organs. As antigen presentation and T cell recruitment are both crucial events in allograft rejection, the aim of this study was to investigate the impact of CCR7 on the development of transplant arteriosclerosis, the hallmark feature of chronic rejection.

The CC chemokine receptor CCR7 has been identified as a key regulator of homeostatic B and T cell trafficking to secondary lymphoid organs. Data presented here demonstrate that CCR7 is also an essential mediator for entry of both dermal and epidermal dendritic cells (DC) into the lymphatic vessels within the dermis while this receptor is dispensable for the mobilization of Langerhans cells from the epidermis to the dermis. Moreover, a distinct population of CD11c(+)MHCII(high) DC showing low expression of the costimulatory molecules CD40, CD80, and CD86 in wild-type animals was virtually absent in skin-draining lymph nodes of CCR7-deficient mice under steady-state conditions. We provide evidence that these cells represent a semimature population of DC that is capable of initiating T cell proliferation under conditions known to induce tolerance. Thus, our data identify CCR7 as a key regulator that governs trafficking of skin DC under both inflammatory and steady-state conditions.

Humoral immunity in the gut-associated lymphoid tissue is characterized by the production of immunoglobulin A (IgA) by antibody-secreting plasma cells (PCs) in the lamina propria. The chemokine CCL25 is expressed by intestinal epithelial cells and is capable of inducing chemotaxis of IgA+ PCs in vitro. Using a newly generated monoclonal antibody against murine CCR9, we show that IgA+ PCs express high levels of CCR9 in the mesenteric lymph node (MLN) and Peyer's patches (PPs), but down-regulate CCR9 once they are located in the small intestine. In CCR9-deficient mice, IgA+ PCs are substantially reduced in number in the lamina propria of the small intestine. In adoptive transfer experiments, CCR9-deficient IgA+ PCs show reduced migration into the small intestine compared with wild-type controls. Furthermore, CCR9 mutants fail to mount a regular IgA response to an orally administered antigen, although the architecture and cell type composition of PPs and MLN are unaffected and are functional for the generation of IgA PCs. These findings provide profound in vivo evidence that CCL25/CCR9 guides PCs into the small intestine.

Lymphoid organs represent highly specialized tissues enabling the development and activation of B and T lymphocytes. Contact between lymphoid and parenchymal cells in bone marrow and thymus is a prerequisite for proper development of B and T cells, respectively, while secondary lymphoid organs, such as spleen and lymph nodes are the places where B and T cells get into contact with antigen presenting cells in order to initiate an adaptive immune response. Recent evidence suggests that few constitutively produced chemokines are essentially required to allow for the correct positioning and interaction of lymphoid and non-lymphoid cells thus creating microenvironments for efficient development and activation of the immune system at multiple stages.