CC chemokine receptor 7-dependent and -independent pathways for lymphocyte homing: modulation by FTY720

Protective role of tissue-resident regulatory T cells in a murine model of beryllium-induced disease

CD4+ T cells drive the immunopathogenesis of chronic beryllium disease (CBD), and their recruitment to the lung heralds the onset of granulomatous inflammation. We have shown that regulatory CD4+ T cells (Tregs) control granuloma formation in an HLA-DP2 transgenic (Tg) model of CBD. In these mice, Be oxide (BeO) exposure resulted in the accumulation of three distinct CD4+ T cell subsets in the lung with the majority of tissue-resident memory cells expressing FoxP3. The amount of Be regulated the number of total and antigen-specific CD4+ T cells and Tregs in the lungs of HLA-DP2 Tg mice. Depletion of Tregs increased the number of IFN-γ-producing CD4+ T cells and enhanced lung injury while mice treated with IL2/αIL-2 complexes had increased Tregs and reduced inflammation and Be-responsive T cells in the lung. BeO-experienced resident Tregs suppressed anti-CD3-induced proliferation of CD4+ T cells in a contact-dependent manner. CLTLA-4 and ICOS blockade as well as addition of LPS to BeO-exposed mice increased the Teff/Treg ratio and enhanced lung injury. Collectively, these data show that the protective role of tissue-resident Tregs is dependent on quantity of Be exposure and is overcome by blocking immune regulatory molecules or additional environmental insults.

Blocking T cell egress with FTY720 extends DNA vaccine expression but reduces immunogenicity

Optimal immunogenicity from nucleic acid vaccines requires a balance of antigen expression that effectively engages the host immune system without generating a cellular response that rapidly destroys cells producing the antigen and thereby limiting vaccine antigen expression. We investigated the role of the cellular response on the expression and antigenicity of DNA vaccines using a plasmid DNA construct expressing luciferase. Repeated intramuscular administration led to diminished luciferase expression, suggesting a role for immune‐mediated clearance of expression. To investigate the role of cell trafficking, we used the sphingosine 1‐phosphate receptor (S1PR) modulator, FTY720 (Fingolimod), which traps lymphocytes within the lymphoid tissues. When lymphocyte trafficking was blocked with FTY720, DNA transgene expression was maintained at a constant level for a significantly extended time period. Both continuous and staggered administration of FTY720 prolonged transgene expression. However, blocking lymphocyte egress during primary transgene administration did not result in an increase of transgene expression during secondary administration. Interestingly, there was a disconnect between transgene expression and immunogenicity, as increasing expression by this approach did not enhance the overall immune response. Furthermore, when FTY720 was administered alongside a DNA vaccine expressing the HIV gp140 envelope antigen, there was a significant reduction in both antigen‐specific antibody and T‐cell responses. This indicates that the developing antigen‐specific cellular response clears DNA vaccine expression but requires access to the site of expression in order to develop an effective immune response.

DNA vaccine transgene expression in tissue can be extended through the co‐administration of the sphingosine 1‐phosphate receptor (S1PR) modulator, FTY720. Despite extending vaccine transgene expression, the administration of FTY720 can reduce vaccine elicited antibody and T‐cell responses.

FTY720 ameliorates GvHD by blocking T lymphocyte migration to target organs and by skin fibrosis inhibition

BACKGROUND

Fibrosis is the formation of excess connective tissue in an organ or tissue during a reparative or reactive process. Graft-versus-host disease (GvHD) is a medical complication of allogeneic tissue transplantation with transplanted donor T cell-mediated inflammatory response; it is characterized by a severe immune response with fibrosis in the final stage of the inflammatory process. T helper 17 cells play a critical role in the pathogenesis of GvHD. Fingolimod (FTY720), an analogue of sphingosine-1-phosphate (S1P), is an effective immunosuppressive agent in experimental transplantation models.

METHODS

In this study, we evaluated the effects of FTY720 as a treatment for an animal GvHD model with inflammation and fibrosis. The splenocytes, lymph nodes, blood, tissues from Syngeneic mice and GvHD-induced mice treated vehicle or FTY720 were compared using flow cytometry, hematological analyses, histologic analyses.

RESULTS

FTY720 reduced clinical scores based on the following five clinical parameters: weight loss, posture, activity, fur texture, and skin integrity. FACS data showed that T lymphocyte numbers increased in mesenteric lymph nodes and decreased in splenocytes of FTY720-treated mice. Tissue analysis showed that FTY720 reduced skin, intestinal inflammation, and fibrotic markers. FTY720 dramatically decreased α-smooth muscle actin, connective tissue growth factor, and fibronectin protein levels in keloid skin fibroblasts.

CONCLUSIONS

Thus, FTY720 suppressed migration of pathogenic T cells to target organs, reducing inflammation. FTY720 also inhibited fibrogenesis marker expression in vitro and in vivo. Together, these results suggest that FTY720 prevents GvHD progression via immunosuppression of TH17 and simultaneously acts an anti-fibrotic agent.

Age-Related Gliosis Promotes Central Nervous System Lymphoma through CCL19-Mediated Tumor Cell Retention

How lymphoma cells (LCs) invade the brain during the development of central nervous system lymphoma (CNSL) is unclear. We found that NF-κB-induced gliosis promotes CNSL in immunocompetent mice. Gliosis elevated cell-adhesion molecules, which increased LCs in the brain but was insufficient to induce CNSL. Astrocyte-derived CCL19 was required for gliosis-induced CNSL. Deleting CCL19 in mice or CCR7 from LCs abrogated CNSL development. Two-photon microscopy revealed LCs transiently entering normal brain parenchyma. Astrocytic CCL19 enhanced parenchymal CNS retention of LCs, thereby promoting CNSL formation. Aged, gliotic wild-type mice were more susceptible to forming CNSL than young wild-type mice, and astrocytic CCL19 was observed in both human gliosis and CNSL. Therefore, CCL19-CCR7 interactions may underlie an increased age-related risk for CNSL.

The intestinal barrier in multiple sclerosis: implications for pathophysiology and therapeutics

Biological barriers are essential for the maintenance of homeostasis in health and disease. Breakdown of the intestinal barrier is an essential aspect of the pathophysiology of gastrointestinal inflammatory diseases, such as inflammatory bowel disease. A wealth of recent studies has shown that the intestinal microbiome, part of the brain-gut axis, could play a role in the pathophysiology of multiple sclerosis. However, an essential component of this axis, the intestinal barrier, has received much less attention. In this review, we describe the intestinal barrier as the physical and functional zone of interaction between the luminal microbiome and the host. Besides its essential role in the regulation of homeostatic processes, the intestinal barrier contains the gut mucosal immune system, a guardian of the integrity of the intestinal tract and the whole organism. Gastrointestinal disorders with intestinal barrier breakdown show evidence of CNS demyelination, and content of the intestinal microbiome entering into the circulation can impact the functions of CNS microglia. We highlight currently available studies suggesting that there is intestinal barrier dysfunction in multiple sclerosis. Finally, we address the mechanisms by which commonly used disease-modifying drugs in multiple sclerosis could alter the intestinal barrier and the microbiome, and we discuss the potential of barrier-stabilizing strategies, including probiotics and stabilization of tight junctions, as novel therapeutic avenues in multiple sclerosis.

Chemokines Modulate Immune Surveillance in Tumorigenesis, Metastasis, and Response to Immunotherapy

Chemokines are small secreted proteins that orchestrate migration and positioning of immune cells within the tissues. Chemokines are essential for the function of the immune system. Accumulating evidence suggest that chemokines play important roles in tumor microenvironment. In this review we discuss an association of chemokine expression and activity within the tumor microenvironment with cancer outcome. We summarize regulation of immune cell recruitment into the tumor by chemokine-chemokine receptor interactions and describe evidence implicating chemokines in promotion of the "inflamed" immune-cell enriched tumor microenvironment. We review both tumor-promoting function of chemokines, such as regulation of tumor metastasis, and beneficial chemokine roles, including stimulation of anti-tumor immunity and response to immunotherapy. Finally, we discuss the therapeutic strategies target tumor-promoting chemokines or induce/deliver beneficial chemokines within the tumor focusing on pre-clinical studies and clinical trials going forward. The goal of this review is to provide insight into comprehensive role of chemokines and their receptors in tumor pathobiology and treatment.

Fingolimod modulates T cell phenotype and regulatory T cell plasticity in vivo

Fingolimod is an approved therapeutic option for patients with relapsing-remitting multiple sclerosis that primarily functions by sequestering T cells in lymph nodes inhibiting their egress to the central nervous system. However, recent data suggests that Fingolimod may also directly affect the immune cell function. Here we examined the in vivo effects of Fingolimod in modulating the phenotype and function of T cell and Foxp3 regulatory T cell populations in patients with multiple sclerosis under Fingolimod treatment. Besides decreasing the cell numbers in peripheral blood and sera levels of pro-inflammatory cytokines, Fingolimod inhibited the expression of Th1 and Th17 cytokines on CD4⁺ T cells and increased the expression of exhaustion markers. Furthermore, treatment increased the frequency of regulatory T cells in blood and inhibited the Th1-like phenotype that is characteristic of patients with multiple sclerosis, augmenting the expression of markers associated with increased suppressive function. Overall, our data suggest that Fingolimod performs other important immunomodulatory functions besides altering T cell migratory capacities, with consequences for other autoimmune pathologies characterized by excessive Th1/Th17 responses and Th1-like regulatory T cell effector phenotypes.

FTY720 ameliorates renal fibrosis by simultaneously affecting leucocyte recruitment and TGF-β signalling in fibroblasts

Renal fibrosis is the common final manifestation of chronic kidney diseases and usually results in end-stage renal failure. In this study, we evaluated the effect of fingolimod (FTY720), an analogue of sphingosine 1-phosphate (S1P), as a treatment for the unilateral ureteral obstruction (UUO)-induced renal fibrosis animal model. We treated mice with FTY720 at a dosage of 1 mg/kg/day by intragastric administration from day 1 until day 7. The control group received the same amount of saline. FTY720 reduced significantly the urine albumin/creatinine ratio (UACR) in treated UUO mice. FTY720 treatment also caused a significant decrease in interstitial expansion and collagen deposition in the kidney, accompanied by reduced mononuclear cell recruitment and inflammatory cytokine expression. In addition, the expression levels of the endothelial cell adhesion molecules P-selectin and vascular cell adhesion protein 1 (VCAM-1) were suppressed in the ligated kidney by FTY720 administration, suggesting reduced renal endothelial cell activation. Furthermore, in renal interstitial fibroblast normal rat kidney (NRK)-49F cells, FTY720 significantly affected transforming growth factor (TGF)-β-induced α-smooth muscle actin (SMA) expression and collagen synthesis by inhibiting both the Mothers against decapentaplegic homologue (Smad)2/3 and phosphatidylinositol 3-kinase/protein kinase B/glycogen synthase kinase 3 beta (PI3K/AKT/GSK3β) signalling pathways. S1P1 knock-down by siRNA reversed this effect significantly in our fibroblast cell culture model. Therefore, FTY720 attenuates renal fibrosis via two different mechanisms: first, FTY720 suppresses the synthesis of extracellular matrix in interstitial fibroblasts by interfering with TGF-β signalling; and secondly, FTY720 affects endothelial cell activation and chemokine expression, thereby reducing immune cell recruitment into the kidney.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Virus-associated activation of innate immunity induces rapid disruption of Peyer's patches in mice

Early in the course of infection, detection of pathogen-associated molecular patterns by innate immune receptors can shape the subsequent adaptive immune response. Here we investigate the influence of virus-associated innate immune activation on lymphocyte distribution in secondary lymphoid organs. We show for the first time that virus infection of mice induces rapid disruption of the Peyer's patches but not of other secondary lymphoid organs. The observed effect was not dependent on an active infectious process, but due to innate immune activation and could be mimicked by virus-associated molecular patterns such as the synthetic double-stranded RNA poly(I:C). Profound histomorphologic changes in Peyer's patches were associated with depletion of organ cellularity, most prominent among the B-cell subset. We demonstrate that the disruption is entirely dependent on type I interferon (IFN). At the cellular level, we show that virus-associated immune activation by IFN-α blocks B-cell trafficking to the Peyer's patches by downregulating expression of the homing molecule α4β7-integrin. In summary, our data identify a mechanism that results in type I IFN-dependent rapid but reversible disruption of intestinal lymphoid organs during systemic viral immune activation. We propose that such rerouted lymphocyte trafficking may impact the development of B-cell immunity to systemic viral pathogens.

Immunoregulatory effects of intraepithelial lymphocytes in inflammatory bowel disease

Intraepithelial lymphocytes (IELs) are found in a wide variety of sites, especially in the mucosa of the intestine, respiratory tract, and genital tract. Intestinal IELs are located between intestinal epithelial cells (IECs) and the basement membrane. The ratio between IECs and IELs in the small intestine is 4-10:1, but is slightly lower in the large intestine. As the first guard of the intestine, IELs play a significant role in maintaining the integrity of the mucosa, immune surveillance and regulating the homeostasis on the intestinal mucosal surface. Recent studies have demonstrated that IELs are also involved in the pathogenesis of inflammatory bowel disease (IBD).

The role of lymphoid tissue in the attenuation of the postoperative ileus

Standardized intestinal manipulation (IM) leads to local bowel wall inflammation subsequently spreading over the entire gastrointestinal tract. Previously, we demonstrated that this so-called gastrointestinal field effect (FE) is immune-mediated. The aim of this study was to investigate the role of secondary lymphoid organs [mesenteric lymph nodes (MLN), gut-associated lymphoid tissue (GALT)] in IM-mediated FE by employing mice with deficient secondary lymphoid organs (aly/aly, MLN ex) or by administration of 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol (FTY720), an immunomodulating agent that inhibits emigration of lymphocytes out of lymphoid organs. Small bowel muscularis, and colonic muscularis from wild-type mice as control, from aly/aly mice, FTY720-treated mice (daily dose of 1.0 mg/kg mouse ip starting 3 days before surgical procedure), and wild-type mice that had undergone removal of mesenteric lymph nodes before IM (MLN ex mice) were obtained after selective IM of the jejunum or sham operation. FE was analyzed by measuring transit time of orally administered fluorescent dextran in the gastrointestinal tract [geometric center (GC) of fluorescent dextran], colonic transit time, infiltration of myeloperoxidase-positive cells, and circular smooth muscle contractility. Furthermore, mRNA levels of inflammatory cytokines [interleukin (IL)-6, tumor necrosis factor (TNF)-α, macrophage inflammatory protein (MIP)-1α] were determined by Taqman-PCR. We observed a significantly reduced upregulation of proinflammatory cytokines (IL-6, TNF-α, MIP-1α) in colonic muscularis of MLN ex mice, aly/aly mice, and FTY720-treated mice compared with wild-type mice. Contractility of circular muscularis strips of the colon but not the jejunum was significantly improved in aly/aly mice and FTY720-treated wild-type mice. Additionally, inflammation of the colon determined by the number of myeloperoxidase-positive cells and colonic transit time were significantly improved in aly/aly mice, FTY720-treated wild-type mice, and in MLN ex mice. In summary, lack of secondary lymphoid organs (MLN + GALT) in aly/aly mice or administration of FTY720 abrogated FE after IM as opposed to wild-type mice. These data demonstrate that secondary lymphoid organs are involved in the propagation of FE and postoperative ileus. FTY720 indirectly affects FE by inhibiting migration of activated T cells from the jejunum and adjacent secondary lymphoid organs to the colon. These findings support the crucial role of the adaptive immune system in FE, most likely by a sphyngosine 1-phosphate-dependent mechanism.

Effects of long-term administration of low-dose FTY720 on survival of murine cardiac allograft

This study examined the effect of long-term administration of low-dose FTY720 on survival of murine cardiac allograft and the possible mechanism. Murine models of abdominal heterotopic heart transplantation were established. Low-dose FTY720 (0.3 mg/kg) was administrated to the animals 4 days before the transplantation of cardiac allografts until the occurrence of rejection or the observation terminals. The animals without FTY720 treatment and those with syngeneic cardiac grafts transplanted served as controls. The mean survival time (MST) of grafts, and T lymphocyte subsets in grafts, peripheral blood and lymphoid organs were measured by histopathological examination or flow cytometry, and compared among groups. The results showed that the MST of allografts in FTY720-treated mice was more than 40 days, significantly longer than that in the untreated group (MST=8 days, P<0.01). After the long-term administration of FTY720, the proportion of CD4(+) and CD8(+) lymphocytes in peripheral blood was diminished significantly, but the proportion of CD4(+) lymphocytes was increased in mesenteric lymph nodes (MLNs) and spleen. Immunofluorescence staining revealed that the infiltration of CD4(+) and CD8(+) lymphocytes in allografts was significantly inhibited after long-term administration of low-dose FTY720. It was concluded that low-dose long-term administration of FTY720 could promote T lymphocytes in lymphatic organs and decrease their infiltration in allografts, resulting in the inhibition of rejection and the long-term survival of allografts.

A mechanistically novel, first oral therapy for multiple sclerosis: the development of fingolimod (FTY720, Gilenya)

Multiple sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system (CNS) through demyelination and neurodegeneration. Until recently, major therapeutic treatments have relied on agents requiring injection delivery. In September 2010, fingolimod/FTY720 (Gilenya, Novartis) was approved by the FDA as the first oral treatment for relapsing forms of MS. Fingolimod is a novel compound produced by chemical modification of a fungal precursor. Its active metabolite, formed by in vivo phosphorylation, modulates sphingosine 1-phosphate (S1P) receptors that are a subset of a larger family of cell-surface, G protein-coupled receptors (GPCRs) mediating the effects of bioactive lipids known as lysophospholipids. Fingolimod's mechanism of action in MS is not completely understood; however, its relevant biology indicates a fundamentally different mechanism compared to all previously approved MS therapies, with evolving research supporting both immunological and nervous system activities. This duality may herald a paradigm shift in the treatment of MS and other neurological disorders.

Targeting lymphangiogenesis after islet transplantation prolongs islet allograft survival

BACKGROUND

Lymphatics are important for their conduit functions of transporting antigen, immune cells, and inflammatory mediators to draining lymph nodes and to the general circulation. Lymphangiogenesis is involved in many pathologic processes; however, the roles for lymphatic responses in transplantation have not been thoroughly investigated.

METHODS

Mice were made diabetic by a single high dose of streptozotocin and then received islet allografts. Animals were treated with three different lymphatic inhibitors. FTY720, an analog of sphingosine 1-phosphate, inhibited lymphocyte migration into afferent and efferent lymphatics. Sunitinib, a kinase inhibitor, blocked several receptors, including vascular endothelial growth factor receptor 3 (VEGFR3), the major growth factor receptor for lymphatic endothelial cells. Anti-VEGFR3 monoclonal antibody specifically inhibited VEGFR3. Diabetes was determined by daily monitoring of blood glucose levels. Inflammation within islet grafts was assessed by immunohistochemistry for insulin, T cells (CD3), and lymphatics (LYVE-1).

RESULTS

After transplantation, lymphangiogenesis occurred in islet allografts and in draining lymph nodes. FTY720, sunitinib, and anti-VEGFR3 each inhibited lymphangiogenesis in the islets and significantly prolonged allograft survival. Immunofluorescent staining demonstrated that administration of each of the lymphatic inhibitors resulted in preservation of islets and β-cells along with a markedly reduced infiltration of T cells into the grafts.

CONCLUSION

Lymphangiogenesis occurs in islet allografts in response to inflammation and plays a key role in the islet inflammation in alloimmunity. Interfering with lymphatic function leads to inhibition of lymphangiogenesis and prolonged or indefinite allograft survival. These observations suggest new therapeutic targets for rejection and tolerance.

Effect of chemokine receptors CCR7 on disseminated behavior of human T cell lymphoma: clinical and experimental study

BACKGROUND

The expression of chemokine receptors CCR7 has been studied in relation to tumor dissemination and poor prognosis in a limited number of cancers. No such studies have been done on CCR7 expression in non-Hodgkin's lymphoma (T-NHL). Our aim in this paper is to investigate the association between CCR7 expression and progression and prognosis of T-NHL.

METHODS

1) Analysis of clinical data: The specimens were obtained from 41 patients with T-NHL and 19 patients with lymphoid hyperplasia. Their corresponding clinicopathologic data were also collected. The expression levels of CCR7, MMP-2, and MMP-9 were examined by immunohistochemical staining. 2) Human T-NHL cell lines Hut 78 (cutaneous T-cell lymphoma) and Jurkat (adult T-cell leukemia/lymphoma) were cultured. The invasiveness of the two cell lines were measured with a Transwell invasion assay, and then used to study the effects of chemokine receptors on T-NHL invasion and the underlying molecular mechanism. The transcript and expression of CCR7 were evaluated using RT-PCR and western blotting.

RESULTS

1) The higher CCR7 and MMP-9 expression ratios were significantly associated with multiple lesions and higher stage III/IV. Moreover, a positive correlation was observed between CCR7 and MMP-9 expression. 2) The Hut 78 cell line was more invasive than the Jurkat cells in the Transwell invasion assay. The transcript and expression levels of CCR7 were significantly higher in Hut78 than that of Jurkat cell line. The T-NHL cell lines were co-cultured with chemokine CCL21 which increased the invasiveness of T-NHL cell. The positive association between CCL21 concentration and invasiveness was found. 3) The stronger transcript and expression of PI(3)K, Akt and p- Akt were also observed in Hut78 than in Jurkat cell line.

CONCLUSIONS

High CCR7 expression in T-NHL cells is significantly associated with lymphatic and distant dissemination as well as with tumor cell migration and invasion in vitro. Its underlying mechanism probably involves the PI(3)K/Akt signal pathway.

Fingolimod (FTY720): discovery and development of an oral drug to treat multiple sclerosis

The discovery of fingolimod (FTY720/Gilenya; Novartis), an orally active immunomodulatory drug, has opened up new approaches to the treatment of multiple sclerosis, the most common inflammatory disorder of the central nervous system. Elucidation of the effects of fingolimod--mediated by the modulation of sphingosine 1-phosphate (S1P) receptors--has indicated that its therapeutic activity could be due to regulation of the migration of selected lymphocyte subsets into the central nervous system and direct effects on neural cells, particularly astrocytes. An improved understanding of the biology of S1P receptors has also been gained. This article describes the discovery and development of fingolimod, which was approved by the US Food and Drug Administration in September 2010 as a first-line treatment for relapsing forms of multiple sclerosis, thereby becoming the first oral disease-modifying therapy to be approved for multiple sclerosis in the United States.

Chemoattractant receptors and lymphocyte egress from extralymphoid tissue: changing requirements during the course of inflammation

Memory/effector T cells traffic efficiently through extralymphoid tissues, entering from the blood and leaving via the afferent lymph. During inflammation, T cell traffic into the affected tissue dramatically increases; however, the dynamics and mechanisms of T cell exit from inflamed tissues are poorly characterized. In this study, we show, using both a mouse and a sheep model, that large numbers of lymphocytes leave the chronically inflamed skin. Many T cells capable of producing IFN-γ and IL-17 also entered the draining afferent lymph, demonstrating that memory/effector T cells egress from sites of inflammation. Whereas efficient egress from acutely inflamed skin required lymphocyte-expressed CCR7, chronic inflammation promoted significant CCR7-independent exit as well. Lymphocyte exit at late time points of inflammation was sensitive to pertussis toxin but was only partially affected by the drug FTY720, implying the contribution of alternative chemoattractant receptors other than spingosine 1-phosphate receptor 1. Our data show that CCR7 is an important receptor for lymphocyte egress from both resting and inflamed extralymphoid tissues, but that alternative exit receptors come into play during chronic inflammation.

Altered expression of signaling genes in Jurkat cells upon FTY720 induced apoptosis

FTY720, a novel immunosuppressant, has a marked activity in decreasing peripheral blood T lymphocytes upon oral administration. Recent investigations suggest that the action of FTY720 on lymphocytes may result from its ability to induce cell apoptosis. However, the cell signaling mechanism involved in the FTY720-induced cell apoptosis remains unclear. Here we examined the apoptotic signal pathways mediated by FTY720 in Jurkat cells using microarray analysis. The results showed that FTY720 can induce Jurkat cell apoptosis in a dose and time dependent manner as assessed by cell viability, Hoechst 33258 staining, Annexin V binding and DNA fragmentation tests. cDNA microarray analysis showed that 10 μM of FTY720 up-regulated 54 and down-regulated 10 genes in Jurkat cells among the 458 apoptotic genes examined following the 6 h incubation period. At least five-fold increased expression of modulator of apoptosis-1 (MOAP-1), vascular endothelial growth factor (VEGF), tumor necrosis factor receptor-associated factors (TRAF 6), Caspase 2 (CASP 2), E2F transcription factor 1 (E2F 1) and Casapse 5 (CASP 5) genes was observed in microarray analyses; these results were confirmed with reverse transcription polymerase chain reaction (RT-PCR) examination. Our findings suggest that the mitochondria related signaling pathways are the key pathways involved in the FTY720-induced apoptosis in Jurkat cells. And our results provide a new insight into the mechanism of FTY720, which allows us to draw the first simple diagram showing the potential pathways mediated by FTY720.

Role of lymphatic vessels in tumor immunity: passive conduits or active participants?

Research in lymphatic biology and cancer immunology may soon intersect as emerging evidence implicates the lymphatics in the progression of chronic inflammation and autoimmunity as well as in tumor metastasis and immune escape. Like the blood vasculature, the lymphatic system comprises a highly dynamic conduit system that regulates fluid homeostasis, antigen transport and immune cell trafficking, which all play important roles in the progression and resolution of inflammation, autoimmune diseases, and cancer. This review presents emerging evidence that lymphatic vessels are active modulators of immunity, perhaps fine-tuning the response to adjust the balance between peripheral tolerance and immunity. This suggests that the tumor-associated lymphatic vessels and draining lymph node may be important in tumor immunity which in turn governs metastasis.

Fingolimod is a potential novel therapy for multiple sclerosis

Fingolimod (also known as FTY720) is an orally available sphingosine-1-phosphate (S1P) receptor modulator that has unique and potent immunoregulatory properties. Mechanistic studies indicate that on phosphorylation fingolimod can bind with high affinity to S1P(1) receptors. Persistent modulation of lymphocyte S1P(1) receptors by fingolimod and the subsequent internalization of these receptors inhibits lymphocyte egress from the lymph nodes, and prevents these cells from infiltrating inflammatory lesions in the CNS. Results of two phase III studies--FREEDOMS and TRANSFORMS--support previous phase II trial observations indicating that fingolimod exerts powerful anti-inflammatory effects in relapsing-remitting multiple sclerosis (MS). Fingolimod might, therefore, be one of the first orally active drug therapies available for the treatment of relapsing-remitting MS. Moreover, results from preclinical studies suggest that fingolimod might promote neural repair in vivo. In this article, we review the background to these findings, present the proposed immunological and neurobiological profile of fingolimod, discuss the data from the FREEDOMS and TRANSFORMS trials, and provide an expert opinion regarding the future of next-generation S1P receptor modulators for MS therapy.

Concurrent visualization of trafficking, expansion, and activation of T lymphocytes and T-cell precursors in vivo

We have developed a dual bioluminescent reporter system allowing noninvasive, concomitant imaging of T-cell trafficking, expansion, and activation of nuclear factor of activated T cells (NFAT) in vivo. NFAT activation plays an important role in T-cell activation and T-cell development. Therefore we used this system to determine spatial-temporal activation patterns of (1) proliferating T lymphocytes during graft-versus-host disease (GVHD) and (2) T-cell precursors during T-cell development after allogeneic hematopoietic stem cell transplantation (HSCT). In the first days after HSCT, donor T cells migrated to the peripheral lymph nodes and the intestines, whereas the NFAT activation was dominant in the intestines, suggesting an important role for the intestines in the early stages of alloactivation during development of GVHD. After adoptive transfer of in vitro-derived T-cell receptor (TCR) H-Y transgenic T-cell precursors into B6 (H-2(b)) hosts of both sexes, NFAT signaling and development into CD4(+) or CD8(+) single-positive cells could only be detected in the thymus of female recipients indicating either absence of positive selection or prompt depletion of double-positive thymocytes in the male recipients. Because NFAT plays an important role in a wide range of cell types, our system could provide new insights into a variety of biologic processes.

A functional role for CCR6 on proallergic T cells in the gastrointestinal tract

BACKGROUND & AIMS

CCL20 is a chemokine that regulates the homeostatic and inflammatory trafficking of leukocytes to the small intestine and regulates the development of the gastrointestinal lymphoid architecture. T cells expressing T helper cell (Th) 2 cytokines are critical for experimental food allergy, and we hypothesized that CCL20 is involved in the localization of these cells to the gut.

METHODS

We evaluated the role of CCR6 in allergic diarrhea induced by sensitization and oral challenge with ovalbumin (OVA) using CCR6(+/+) and CCR6(-/-) mice.

RESULTS

CCR6(-/-) mice were protected from OVA-induced diarrhea but surprisingly were not impaired in mastocytosis or allergen-specific immunoglobulin E. CCR6(-/-) mice were also protected from T cell-mediated diarrhea induced by anti-CD3 antibody. Allergic diarrhea was associated with an increased expression of Th2 cytokines within the intestinal mucosa that was significantly reduced in CCR6(-/-) mice. Inhibition of lymphocyte homing by treatment with FTY720 did not impair allergic diarrhea, indicating that reactivation of T cells could occur locally within the small intestine. Finally, T-cell transfer studies demonstrated that CCR6 was required both on the transferred T cells and in the recipient mouse to manifest allergic disease in the gastrointestinal tract.

CONCLUSIONS

These studies highlight a mast cell- and immunoglobulin E-independent role for CCR6-bearing T cells in the pathogenesis of gastrointestinal allergic disease.

CCR7 regulates lymphocyte egress and recirculation through body cavities

T and B lymphocytes recirculate among blood, lymph, and extralymphoid tissues to ensure immune surveillance and the establishment of self-tolerance. The underlying mechanisms regulating homeostatic lymphocyte recirculation through body cavities are not fully understood. Here, we demonstrate that the homeostatic chemokine receptor CCR7 regulates homeostatic recirculation of lymphocytes through body cavities. CCR7 deficiency results in massive accumulation of CD4(+) and CD8(+) T cells and B-2 B cells in the peritoneal and pleural cavities. The increase in B-2 B and T lymphocytes is not associated with an altered maturation and/or activation status of these cells. Mechanistically, an increase in peritoneal lymphocyte numbers is caused by impaired egress of CCR7-deficient lymphocytes from body cavities. These results establish that CCR7 plays a crucial role in lymphocyte exit from the PerC.

The influence of sphingosine-1-phosphate receptor signaling on lymphocyte trafficking: how a bioactive lipid mediator grew up from an "immature" vascular maturation factor to a "mature" mediator of lymphocyte behavior and function

Since the initial observations that highlighted the importance of lymphocyte trafficking for immune responses, the pathways utilized by B and T lymphocytes to recirculate and properly position themselves have been intensely studied. Most of the chemoattractants along with their cognate receptors that affect lymphocyte trafficking have been identified. Some of their functions are promotion of lymphocyte ingress into immune organs, localization of cells to specific regions within those organs, maintenance of lymphocyte basal motility in immune organs, facilitation of lymphocyte egress from these organs, and control of migration and homing of lymphocytes in the periphery. Since the seminal discovery that agonism of sphingosine-1-phosphate receptors evokes changes in lymphocyte homing and trafficking, considerable effort has been undertaken to characterize the mechanism utilized by these receptors to influence lymphocyte behavior. This review will focus on the influence of sphingosine-1-phosphate signaling system on lymphocyte localization, egress from lymph organs, and its effects on the lymphatic vasculature.

Thymic emigration: sphingosine-1-phosphate receptor-1-dependent models and beyond

The thymus is a primary lymphoid organ supporting the development of self-tolerant T cells. Key events in T-cell development in the thymus include lineage commitment, selection events, and thymic emigration. This review discusses the proposed role of sphingosine-1-phosphate and its receptors in the emigration of both conventional and unconventional T-cell subsets from the thymus, and the molecular machinery currently understood to regulate this process. Furthermore, we highlight a role for chemokines and actin-associated proteins in T-cell motility as recent data suggest that T-cell emigration is regulated by more than just a sphingosine-1-phosphate receptor-1-dependent chemotactic axis.

Lymphocyte homing and its role in the pathogenesis of IBD

Inflammatory bowel disease (IBD) is an idiopathic disorder of chronic inflammation of the gastrointestinal tract. Experimental models of IBD and results from human genomewide linkage studies suggest that the primary defect that leads to IBD is an inappropriate mucosal immune response to normal intestinal microbes. Genetic alterations not only confer increased susceptibility to IBD but also appear to determine the nature and location of the intestinal inflammation, as is evident in patients with genetic alterations of NOD2 and their susceptibility for ileal Crohn's disease. IBD has traditionally been classified into 2 subtypes, namely, ulcerative colitis (UC) and Crohn's disease (CD), based on histological appearance and anatomical distribution. However, an increasing body of data supports the concept that IBD is an umbrella diagnosis encompassing a variety of disorders with distinct genetic, microbial, and environmental determinants that cluster either into a UC or CD phenotype. The shared common pathway is uncontrolled intestinal inflammation. A key element in the pathogenesis of intestinal inflammation in both UC and CD is increased leukocyte recruitment from the circulation, and this provides a potential target for pharmaceutical inhibition. In this article we review the current understanding of the molecules that determine leukocyte trafficking to the gut and highlight opportunities where their inhibition could be exploited to treat IBD.(Inflamm Bowel Dis 2008).

Sphingosine 1-phosphate receptor agonism impairs skin dendritic cell migration and homing to secondary lymphoid tissue: association with prolonged allograft survival

The novel immunomodulator FTY720 is a prototypic sphingosine-1-phosphate (S1P) receptor agonist that regulates lymphocyte migration and prolongs allograft survival. Skin dendritic cells (DC) play important roles in cutaneous immunity. We investigated the migration and function of skin DC exposed to FTY720 in vivo, or to its metabolite FTY720 phosphate (P) in vitro. C57BL/10 (H2(b)) recipient (but not donor) FTY720 treatment prolonged median skin C3H (H2(k)) allograft survival significantly, from 12 to 34.5 days. Non-transplanted, FTY720-treated mice revealed a marked increase in skin DC, although total DC in skin-draining lymph nodes (DLN) were unchanged compared with controls. Fewer allogeneic donor DC migrated to DLN of FTY720-treated graft recipients. DC that migrated from the skin of FTY720-treated mice showed reduced MHC class II, CD86 and CCR7 expression, suggesting impaired migratory potential to secondary lymphoid tissue, that correlated with DC retention in skin, and reduced T cell stimulatory activity. Fewer DC migrated from normal skin explants exposed to the FTY720 metabolite, FTY720P than to control medium. DC that did migrate expressed lower levels of MHC class II, CD86 and CCR7, and inferior T cell stimulatory ability. These data demonstrate S1P signaling regulates skin DC trafficking and modulates MHC class II, costimulatory, and homing receptor molecule expression that impairs their ability to elicit allogeneic T cell responses.

The thymus is required for the ability of FTY720 to prolong skin allograft survival across different histocompatibility MHC barriers

The immunosuppressive effect of FTY720 is associated with the reversible sequestration of lymphocytes from the blood and the spleen into secondary lymphoid organs and reduced egress of mature thymocytes from the thymus. This work was designed to dissect the differential effect of FTY720 on CD4 and CD8 T cell-mediated mechanisms of skin graft rejection in the presence (euthymic) or absence (thymectomized) of thymic output. To that end, untreated and FTY720-treated euthymic (Euthy) and thymectomized (ATX) mice received skin allografts across a full, class II or class I major histocompatibility complex (MHC) mismatched (MM) barriers and graft survival was monitored. We demonstrate that a short course of FTY720 treatment significantly augments the survival of full, class I and class II MHC MM skin grafts compared to the nontreated controls. Interestingly, FTY720-treated Euthy recipients showed a significantly prolonged skin allograft survival compared to FTY720-treated ATX mice. These results together show that FTY720 impairs both CD4 and CD8 T cell-mediated mechanisms of rejection and, more importantly, the presence of the thymus is necessary for the ability of FTY720 to modulate skin allograft rejection across different histocompatibility MHC barriers.

Experimental scrapie in 'plt' mice: an assessment of the role of dendritic-cell migration in the pathogenesis of prion diseases

Peripherally acquired transmissible spongiform encephalopathies display strikingly long incubation periods, during which increasing amounts of prions can be detected in lymphoid tissues. While precise sites of peripheral accumulation have been described, the mechanisms of prion transport from mucosa and skin to lymphoid and nervous tissues remain unknown. Because of unique functional abilities, dendritic cells (DCs) have been suspected to participate in prion pathogenesis. In mice inoculated subcutaneously with scrapie-infected DCs, the incubation was shorter when cells were alive as compared with killed cells, suggesting that DC functions may facilitate prion neuroinvasion. However, early propagation in lymphoid tissues seemed not importantly affected by DC vitality. Mutant (plt) mice that have deficient CCL19/CCL21 expression and DC migration displayed similar infection of secondary lymphoid organs as normal mice, regardless of the route of inoculation and scrapie strain. Under certain conditions of transcutaneous inoculation, the incubation and duration of disease were moderately prolonged in plt mice. This was not related to a milder neuropathogenesis, since plt and normal mice were equally susceptible to intracerebral prion challenge. We conclude that peripheral spreading of prions appears poorly dependent on cell migration through the chemokine/receptor system CCL19/CCL21/CCR7, although DCs might be able to help prions reach sites of neuroinvasion.

FTY720 (fingolimod) in renal transplantation

FTY720 (Fingolimod) is a novel immunomodulator with a mode of action that is completely different from classical immunosuppressants. FTY is a structural and functional analogue of the natural serum lipid, sphingosine, and is the first in a new class of drugs called sphingosine 1-phosphate receptor (S1P-R) modulators. This review discusses the recent findings on the mechanism of action, preclinical models and outlines the results of the ongoing clinical development program. FTY is highly effective in prolonging allograft survival in preclinical models of transplantation and in experimental models of autoimmune diseases. In clinical trials, this novel compound was investigated in de novo renal transplantation and in multiple sclerosis. Pharmacokinetics are characterized by a prolonged absorption phase, a large volume of distribution, and a long elimination half-life. FTY induces a rapid and transient decrease in lymphocyte counts, which supports the modulatory effects of the drug on lymphocyte sequestration. The most common adverse event was asymptomatic transient bradycardia, a pharmacodynamic effect modulated by atrial S1 P-R. FTY failed to show an improvement in efficacy for the prevention of renal allograft rejection in two large phase III studies. FTY treatment regimens were associated with impaired renal function and the development of macula edema. Consequently, the further development in renal transplantation was stopped. Because initial clinical studies strongly suggest that FTY is highly effective in multiple sclerosis FTY is now being explored in phase III studies for the treatment of demyelinating diseases, Ongoing studies in multiple sclerosis are eagerly awaited because they may provide novel therapeutic options for patients with autoimmune diseases.

Intraepithelial lymphocytes: their shared and divergent immunological behaviors in the small and large intestine

At the front line of the body's immunological defense system, the gastrointestinal tract faces a large number of food-derived antigens, allergens, and nutrients, as well as commensal and pathogenic microorganisms. To maintain intestinal homeostasis, the gut immune system regulates two opposite immunological reactions: immune activation and quiescence. With their versatile immunological features, intraepithelial lymphocytes (IELs) play an important role in this regulation. IELs are mainly composed of T cells, but these T cells are immunologically distinct from peripheral T cells. Not only do IELs differ immunologically from peripheral T cells but they are also comprised of heterogeneous populations showing different phenotypes and immunological functions, as well as trafficking and developmental pathways. Though IELs in the small and large intestine share common features, they have also developed differences as they adjust to the two different environments. This review seeks to shed light on the immunological diversity of small and large intestinal IELs.

CCR7 is required for the in vivo function of CD4+ CD25+ regulatory T cells

CCR7-mediated migration of naive T cells into the secondary lymphoid organs is a prerequisite for their encounter with mature dendritic cells, the productive presentation of cognate antigen, and consequent T cell proliferation and effector differentiation. Therefore, CCR7 was suggested to play an important role in the initiation of adaptive immune responses. In this study, we show that primary immunity can also develop in the absence of CCR7. Moreover, CCR7-deficient knockout (KO) mice display augmented immune responses. Our data cumulatively suggest that enhanced immunity in CCR7 KO mice is caused by the defective lymph node (LN) positioning of FoxP3⁺ CD4⁺ CD25⁺ regulatory T cells (T reg cells) and the consequent impediment of their function. The FoxP3⁺ T reg cells express CCR7 and, after their adoptive transfer, migrate into the LNs of wild-type mice. Here, they proliferate in situ upon antigen stimulation and inhibit the generation of antigen-specific T cells. Conversely, transferred CCR7-deficient T reg cells fail to migrate into the LNs and suppress antigen-induced T cell responses. The transfer of combinations of naive and T reg cells from wild-type and CCR7 KO mice into syngeneic severe combined immunodeficient mice directly demonstrates that CCR7-deficient T reg cells are less effective than their wild-type counterparts in preventing the development of inflammatory bowel disease.

Sphingosine 1-phosphate regulates peritoneal B-cell trafficking for subsequent intestinal IgA production

Sphingosine 1-phosphate (S1P) is known to play a pivotal role in the regulation of lymphocyte emigration from organized lymphoid tissues such as the peripheral lymph nodes and thymus, but its immunologic role in unorganized and diffused tissues remains to be elucidated. Here we show that the trafficking of peritoneal B cells is principally regulated by S1P. All peritoneal B cells including B1a, B1b, and B2 B cells express comparable levels of the type 1 S1P receptor. Thus, treatment with FTY720, an S1P receptor modulator, caused the rapid disappearance of peritoneal B cells by inhibiting both their emigration from parathymic lymph nodes and their recirculation from the blood into the peritoneal cavity without affecting their progenitor populations. These changes did not affect natural plasma antibody production or phosphorylcholine (PC)–specific antibody production in serum after peritoneal immunization with heat-killed Streptococcal pneumoniae (R36A). However, FTY720 dramatically reduced peritoneal B cell-derived natural intestinal secretory IgA production without affecting the expression of J-chain and polyimmunoglobulin receptors. Additionally, FTY720 impaired the generation of PC-specific fecal IgA responses after oral immunization with R36A. These findings point to a pivotal role for S1P in connecting peritoneal B cells with intestinal B-cell immunity.

The immunomodulator FTY720 and its phosphorylated derivative activate the Smad signalling cascade and upregulate connective tissue growth factor and collagen type IV expression in renal mesangial cells

1.--The immunomodulating agent FTY720 is a substrate for the sphingosine kinase and the phosphorylated form is able to bind to sphingosine 1-phosphate (S1P) receptors. In this study, we show that exposure of renal mesangial cells to phospho-FTY720 leads to a rapid and transient activation of several protein kinase cascades, including the mitogen- and stress-activated protein kinases. The nonphosphorylated FTY720 also increased MAPK phosphorylation, but with a reduced potency and a more delayed time course. In addition, phospho-FTY720 and FTY720 are able to increase phosphorylation of Smad proteins which are classical members of the transforming growth factor-beta (TGF-beta) signalling device, thus suggesting a crosstalk between FTY720 and TGF-beta signalling. 2.--Pretreatment with the S1P(3) receptor antagonist suramin inhibits FTY720 and phospho-FTY720-induced Smad phosphorylation, whereas pertussis toxin pretreatment, which blocks G(i/0) proteins, has no effect on Smad phosphorylation. 3.--Since TGF-beta is a potent profibrotic cytokine in mesangial cells and upregulates the connective tissue growth factor (CTGF) and collagen as important hallmarks in the fibrotic sequelae, we investigated whether FTY720 and phospho-FTY720 are able to mimic these effects of TGF-beta. Indeed, FTY720 and phospho-FTY720 markedly upregulate CTGF and collagen type IV protein expressions. In addition, the tissue inhibitor of metalloproteinase-1 is transcriptionally activated by FTY720, whereas cytokine-induced matrix metalloproteinase-9 is down-regulated by FTY720. 4.--Depletion of the TGF-beta receptor type II by the siRNA transfection technique blocks not only Smad phosphorylation but also CTGF upregulation. Similarly, Smad-4 depletion by siRNA transfection also abrogates CTGF upregulation induced by FTY720 and phospho-FTY720. 5.--In summary, our data show that FTY720 and phospho-FTY720 not only activate the Smad signalling cascade in mesangial cells, but also upregulate the expression of CTGF and collagen. These findings suggest that FTY720 may have additional effects besides the established immunomodulatory action and, importantly, a profibrotic activity has to be considered in future experimental approaches.

Inhibition of donor-derived T cells trafficking into target organs by FTY720 during acute graft-versus-host disease in small bowel transplantation

In small bowel transplantation (SBTx), graft-versus-host disease (GVHD) is mediated by donor-derived T cells recognizing host major histocompatibility complex (MHC) alloantigens, and represents an important immunological event influencing life in experimental and clinical situations. We evaluated the possibility that a new sphingosine 1-phosphate receptor agonist, FTY720, could diminish GVHD in a rat SBTx model through traffic alteration of donor-derived T cells in target organs. Heterotopic SBTx was performed using a parent (WF)-into-F(1) (WF x ACI) rat combination. Recipient survival, body weight, histopathology, donor-derived T cell subpopulation and cytokine production were compared with untreated controls. FTY720 inhibited lethality and histopathological changes in target organs when administered at 0.5 mg/kg, possibly due to sequestration of donor-derived T cells in the intestinal graft. FTY720 caused a significant reduction in donor T cell numbers in target organs by promoting these cells to home into donor, but not recipient, secondary lymphoid tissues. FTY720 significantly decreased production of interferon (IFN)-gamma in target organs. These findings indicate that FTY720 effectively reduced recirculation of activated donor-derived T cells and recruitment to target organs in GVHD, and was also associated with down-regulated IFN-gamma production. These properties may offer the potential to treat ongoing GVHD in SBTx.

The sphingosine-1-phosphate analogue FTY720 reduces atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

The sphingosine-1-phosphate (S1P) analogue FTY720 is a potent immunosuppressive agent currently in Phase III clinical trials for kidney transplantation. FTY720 traps lymphocytes in secondary lymphoid organs thereby preventing their migration to inflammatory sites. Previously, we have identified FTY720 as a potent activator of eNOS. As both inhibition of immune responses and stimulation of eNOS may attenuate atherosclerosis, we administered FTY720 to apolipoprotein E-/- mice fed a high-cholesterol diet.

METHODS AND RESULTS

FTY720 dramatically reduced atherosclerotic lesion volume (62.5%), macrophage (41.8%), and collagen content (63.5%) after 20 weeks of high-cholesterol diet. In isolated aortic segments and cultured vascular smooth muscle cell, FTY720 potently inhibited thrombin-induced release of monocyte chemoattractant protein-1. This effect was mediated by the S1P3 sphingolipid receptor as FTY720 had no effect on thrombin-induced monocyte chemoattractant protein-1 release in S1P3-/- mice. In contrast to S1P receptors on lymphocytes, FTY720 did not desensitize vascular S1P receptors as arteries from FTY720-treated mice retained their vasodilator response to FTY720-phosphate.

CONCLUSIONS

We suggest that FTY720 inhibits atherosclerosis by suppressing the machinery involved in monocyte/macrophage emigration to atherosclerotic lesions. As vascular S1P receptors remained functional under FTY720 treatment, S1P agonists that selectively target the vasculature and not the immune system may be promising new drugs against atherosclerosis.

Blocking the immune response in ischemic acute kidney injury: the role of adenosine 2A agonists

Acute kidney injury (AKI) is associated with a high degree of morbidity and mortality and its incidence is increasing. These factors, together with a lack of successful clinical trials, necessitate a comprehensive evaluation of the pathogenesis of AKI and trial design. The progress that has been made in elucidating the pathogenesis of AKI has defined inflammation as an early event and therefore a potential target for therapeutic intervention. This Review summarizes recent advances in our understanding of the role of inflammation in AKI as well as our approach to limiting inflammation using compounds that stimulate adenosine 2A receptors (A(2A)Rs). A(2A)Rs are members of a family of guanine nucleotide-binding proteins that have become a focus of interest primarily because of their ability to broadly inactivate the inflammatory cascade. An A(2A) agonist-ATL146 ester (ATL146e)-is currently being tested in a phase III clinical trial as a pharmacological stress agent in cardiac perfusion imaging studies. This study, together with extensively published preclinical data, will facilitate testing of ATL146e in human trials of AKI.

Differential effects of single dose FTY720 on CD62L+ B-cells in stable renal allograft recipients

FTY720, a sphingosine-1-phosphate receptor agonist, is the archeotype of a new class of immune modulators, which redirects lymphocytes from the peripheral blood into secondary lymphatic tissue. Previously, it was shown that FTY720 differentially decreases peripheral T-cells, expressing specific chemokine and adhesion receptors. Here, we investigated the effect of single doses FTY720 on peripheral B-cells expressing CD62L, CD11a, CD49d and CXCR4 in stable human renal allograft recipients. Peripheral blood lymphocytes were isolated by Ficoll density centrifugation and stained with monoclonal antibodies against CD3 or CD19 and CD62L, CD11a, CD49d, CXCR4 to determine the percentage of these T- and B-cell subpopulations. Total lymphocyte counts were measured by routine laboratory diagnostics to calculate absolute lymphocyte subset counts. In FTY720 treated patients, total lymphocyte counts decreased by 31.8% (0.25-2 mg) and 60.4% (3.5 mg), and total T-cell counts by 38.8% (0.25-2 mg) and 70.9% (3.5 mg). In comparison, total B-cell counts decreased by 32.2% (0.25-2 mg) and 61.1% (3.5 mg). The reduction of CD62L+ B-cells was less pronounced as compared to CD62L+ T-cells (0.25-2 mg: 15.7% vs. 57.3%; 3.5 mg: 57.2% vs. 86.9%). CD11a+ B-cells decreased by 15.4% (0.25-2 mg) and 57.1% (3.5 mg), and CD49d+ B-cells by 15.0% (0.25-2 mg) and 56.7% (3.5 mg). CXCR4+ B-cells decreased by 19.9% (0.25-2 mg) and 57.2% (3.5 mg). In vitro experiments showed that FTY720 did not change the mean expression of CD62L, CD11a, CD49d and CXCR4 on CD19+ B-cells. In conclusion FTY720 treatment reduces B-cells expressing CD62L to a significant lesser degree than T-cells expressing CD62L.

Evidence that a significant number of naive T cells enter non-lymphoid organs as part of a normal migratory pathway

Only activated and effector memory T cells are thought to access non-lymphoid tissues. In contrast, naive T cells are thought to circulate only between the blood, lymph and secondary lymphoid organs. We examined the phenotype of endogenous T cells in various non-lymphoid organs and showed that a subset of cells exhibited an apparently naive phenotype and were functionally inactive. FTY720 treatment selectively depleted this population from the non-lymphoid tissues. In addition, RAG-deficient TCR transgenic CD4 and CD8 T cells were present in non-lymphoid tissues in bone marrow chimeric mice and in situ imaging analysis revealed their location in the parenchymal tissues. Moreover, migration of TCR transgenic T cells to non-lymphoid tissues after adoptive transfer was pertussis-toxin resistant. Overall, the results suggest that naive T cells may circulate through non-lymphoid tissues as part of their normal migratory pathway.

FTY720 suppresses CD4+CD44highCD62L- effector memory T cell-mediated colitis

FTY720, a sphingosine-derived immunomodulator, causes immunosuppression via enhancement of lymphocyte sequestration into secondary lymphoid organs, thereby preventing their antigen-activated T cell egress to sites of inflammation. FTY720 is highly effective in inhibiting autoimmunity in various animal models. However, there is little known about how FTY720 controls the migration property of memory T cells. Here, we demonstrated that FTY720 prevents the development of colitis induced by the adoptive transfer of lamina propria (LP) colitogenic effector memory CD4+ T cells (TEM cells; CD45RB(low)CD44(high)CD62L-) into severe combined immunodeficiency (SCID) mice and suppresses interferon-gamma, interleukin-2, and tumor necrosis factor-alpha production by LP CD4+ T cells. The numbers of spleen, peripheral blood, mesenteric lymph node, and LP CD4+ T cells in FTY720-treated mice were significantly reduced compared with those in control mice. Notably, LP CD4+ TEM cells as well as splenic CD4+CD45RBhigh T cells expressed several spingosine-1-phosphate receptors that are targets for FTY720. Furthermore, FTY720 also prevented the development of colitis induced by the adoptive transfer of splenic CD4+CD45RBhigh T cells into SCID mice. Collectively, the present data indicate that FTY720 treatment may offer the potential not only to prevent the onset of disease but also to treat memory T cell-mediated autoimmune diseases including inflammatory bowel diseases.

Transient T cell accumulation in lymph nodes and sustained lymphopenia in mice treated with FTY720

FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride) is an orally available immunomodulatory agent that induces severe peripheral blood lymphopenia. Most studies of these lymphopenic effects have been limited to short-term exposure to FTY720. FTY720 alters the ability of lymphocytes to respond to sphingosine-1-phosphate (S1P) through S1P receptors, particularly S1P1. FTY720 affects different leukocyte populations and their trafficking through major lymphoid organs. We show the dynamics of CD4 T, CD8 T, and B lymphocyte recirculation in all major lymphoid compartments during 21-day FTY720 treatment of normal C57BL/6 mice. Following a transient increase in peripheral lymph nodes and Peyer's patches, lymphocyte recirculation reaches a new steady state. Other lymphoid organs show transient changes in lymphocyte composition with various patterns. At 21 days of FTY720 treatment, total body lymphocyte content is reduced by 20% and blood lymphocytes by 80%. Modeling suggests that the new steady state is due to a combination of reduced naive lymphocyte release from the thymus and a transient reduction of lymphocyte egress from lymph nodes. Our data indicate that the commonly held belief that FTY720 blocks lymphocyte egress from lymph nodes cannot fully explain the lymphocyte dynamics observed with prolonged treatment.

Sphingosine kinase: biochemical and cellular regulation and role in disease

Sphingolipids have emerged as molecules whose metabolism is regulated leading to generation of bioactive products including ceramide, sphingosine, and sphingosine-1-phosphate. The balance between cellular levels of these bioactive products is increasingly recognized to be critical to cell regulation; whereby, ceramide and sphingosine cause apoptosis and growth arrest phenotypes, and sphingosine-1-phosphate mediates proliferative and angiogenic responses. Sphingosine kinase is a key enzyme in modulating the levels of these lipids and is emerging as an important and regulated enzyme. This review is geared at mechanisms of regulation of sphingosine kinase and the coming to light of its role in disease.