Lymphocyte trafficking across high endothelial venules: dogmas and enigmas

Tertiary Lymphoid Structure-Associated B Cells are Key Players in Anti-Tumor Immunity

It is now admitted that the immune system plays a major role in tumor control. Besides the existence of tumor-specific T cells and B cells, many studies have demonstrated that high numbers of tumor-infiltrating lymphocytes are associated with good clinical outcome. In addition, not only the density but also the organization of tumor-infiltrating immune cells has been shown to determine patient survival. Indeed, more and more studies describe the development within the tumor microenvironment of tertiary lymphoid structures (TLS), whose presence has a positive impact on tumor prognosis. TLS are transient ectopic lymphoid aggregates displaying the same organization and functionality as canonical secondary lymphoid organs, with T-cell-rich and B-cell-rich areas that are sites for the differentiation of effector and memory T cells and B cells. However, factors favoring the emergence of such structures within tumors still need to be fully characterized. In this review, we survey the state of the art of what is known about the general organization, induction, and functionality of TLS during chronic inflammation, and more especially in cancer, with a particular focus on the B-cell compartment. We detail the role played by TLS B cells in anti-tumor immunity, both as antigen-presenting cells and tumor antigen-specific antibody-secreting cells, and raise the question of the capacity of chemotherapeutic and immunotherapeutic agents to induce the development of TLS within tumors. Finally, we explore how to take advantage of our knowledge on TLS B cells to develop new therapeutic tools.

The HIV-1 Gp120/CXCR4 axis promotes CCR7 ligand-dependent CD4 T cell migration: CCR7 homo- and CCR7/CXCR4 hetero-oligomer formation as a possible mechanism for up-regulation of functional CCR7

During human immunodeficiency virus (HIV) infection, enhanced migration of infected cells to lymph nodes leads to efficient propagation of HIV-1. The selective chemokine receptors, including CXCR4 and CCR7, may play a role in this process, yet the viral factors regulating chemokine-dependent T cell migration remain relatively unclear. The functional cooperation between the CXCR4 ligand chemokine CXCL12 and the CCR7 ligand chemokines CCL19 and CCL21 enhances CCR7-dependent T cell motility in vitro as well as cell trafficking into the lymph nodes in vivo. In this study, we report that a recombinant form of a viral CXCR4 ligand, X4-tropic HIV-1 gp120, enhanced the CD4 T cell response to CCR7 ligands in a manner dependent on CXCR4 and CD4, and that this effect was recapitulated by HIV-1 virions. HIV-1 gp120 significantly enhanced CCR7-dependent CD4 T cell migration from the footpad of mice to the draining lymph nodes in in vivo transfer experiments. We also demonstrated that CXCR4 expression is required for stable CCR7 expression on the CD4 T cell surface, whereas CXCR4 signaling facilitated CCR7 ligand binding to the cell surface and increased the level of CCR7 homo- as well as CXCR4/CCR7 hetero-oligomers without affecting CCR7 expression levels. Our findings indicate that HIV-evoked CXCR4 signaling promotes CCR7-dependent CD4 T cell migration by up-regulating CCR7 function, which is likely to be induced by increased formation of CCR7 homo- and CXCR4/CCR7 hetero-oligomers on the surface of CD4 T cells.

Transcriptional programs of lymphoid tissue capillary and high endothelium reveal control mechanisms for lymphocyte homing

Lymphocytes are recruited from blood by high-endothelial venules (HEVs). We performed transcriptomic analyses and identified molecular signatures that distinguish HEVs from capillary endothelium and that define tissue-specific HEV specialization. Capillaries expressed gene programs for vascular development. HEV-expressed genes showed enrichment for genes encoding molecules involved in immunological defense and lymphocyte migration. We identify capillary and HEV markers and candidate mechanisms for regulated recruitment of lymphocytes, including a lymph node HEV-selective transmembrane mucin; transcriptional control of functionally specialized carbohydrate ligands for lymphocyte L-selectin; HEV expression of molecules for transendothelial migration; and metabolic programs for lipid mediators of lymphocyte motility and chemotaxis. We also elucidate a carbohydrate-recognition pathway that targets B cells to intestinal lymphoid tissues, defining CD22 as a lectin-homing receptor for mucosal HEVs.

Gut-Homing Conventional Plasmablasts and CD27(-) Plasmablasts Elicited after a Short Time of Exposure to an Oral Live-Attenuated Shigella Vaccine Candidate in Humans

Currently, there is no licensed Shigella vaccine; however, various promising live-attenuated vaccine candidates have emerged, including CVD1208S (ΔguaBA, Δset, Δsen S. flexneri 2a), which was shown to be safe and immunogenic in Phase 1 clinical trials. Here, we report the immune responses elicited in an outpatient Phase 2 clinical trial in which subjects were vaccinated with CVD 1208S. Oral immunization with CVD 1208S elicited high anti-S. flexneri 2a LPS and IpaB antibody responses as well as an acute plasmablast (PB) infiltration in peripheral blood 7 days after immunization. PB sorted based on their expression of homing molecules confirmed that cells expressing integrin α4β7 alone or in combination with CD62L were responsible for antibody production (as measured by ELISpot). Furthermore, using high-color flow-cytometry, on day 7 after immunization, we observed the appearance of conventional PB (CPB, CD19^dim CD20⁻ CD27^+high CD38^+high CD3⁻), as well as a PB population that did not express CD27 (CD27⁻ PB; pre-plasmablasts). The pattern of individual or simultaneous expression of homing markers (integrin α4β7, CD62L, CXCR3, and CXCR4) suggested that CPB cells homed preferentially to the inflamed gut mucosa. In contrast, ~50% CD27⁻ PB cells appear to home to yet to be identified peripheral lymphoid organs or were in a transition state preceding integrin α4β7 upregulation. In sum, these observations demonstrate that strong immune responses, including distinct PB subsets with the potential to home to the gut and other secondary lymphoid organs, can be elicited after a short time of exposure to a shigella oral vaccine.

The immune microenvironment: a major player in human cancers

Cancer is a major public health issue and figures among the leading causes of death in the world. Cancer development is a long process, involving the mutation, amplification or deletion of genes and chromosomal rearrangements. The transformed cells change morphologically, enlarge, become invasive and finally detach from the primary tumor to metastasize in other organs through the blood and/or lymph. During this process, the tumor cells interact with their microenvironment, which is complex and composed of stromal and immune cells that penetrate the tumor site via blood vessels and lymphoid capillaries. All subsets of immune cells can be found in tumors, but their respective density, functionality and organization vary from one type of tumor to another. Whereas inflammatory cells play a protumoral role, there is a large body of evidence of effector memory T cells controlling tumor invasion and metastasis. Thus, high densities of memory Th1/CD8 cytotoxic T cells in the primary tumors correlate with good prognosis in most tumor types. Tertiary lymphoid structures, which contain mature dendritic cells (DC) in a T cell zone, proliferating B cells and follicular DC, are found in the tumor stroma and they correlate with intratumoral Th1/CD8 T cell and B cell infiltration. Eventually, tumors undergo genetic and epigenetic modifications that allow them to escape being controlled by the immune system. This comprehensive review describes the immune contexture of human primary and metastatic tumors, how it impacts on patient outcomes and how it could be used as a predictive biomarker and guide immunotherapies.

Every breath you take: the impact of environment on resident memory CD8 T cells in the lung

Resident memory T cells (T_RM) are broadly defined as a population of T cells, which persist in non-lymphoid sites long-term, do not re-enter the circulation, and are distinct from central memory T cells (T_CM) and circulating effector memory T cells (T_EM). Recent studies have described populations of T_RM cells in the skin, gut, lungs, and nervous tissue. However, it is becoming increasingly clear that the specific environment in which the T_RM reside can further refine their phenotypical and functional properties. Here, we focus on the T_RM cells that develop following respiratory infection and reside in the lungs and the lung airways. Specifically, we will review recent studies that have described some of the requirements for establishment of T_RM cells in these tissues, and the defining characteristics of T_RM in the lungs and lung airways. With continual bombardment of the respiratory tract by both pathogenic and environmental antigens, dynamic fluctuations in the local milieu including homeostatic resources and niche restrictions can impact T_RM longevity. Beyond a comprehensive characterization of lung T_RM cells, special attention will be placed on studies, which have defined how the microenvironment of the lung influences memory T cell survival at this site. As memory T cell populations in the lung airways are requisite for protection yet wane numerically over time, developing a comprehensive picture of factors which may influence T_RM development and persistence at these sites is important for improving T cell-based vaccine design.

Characterization of mouse mediastinal fat-associated lymphoid clusters

The association between adipose tissue and immunity has been established and fat-associated lymphoid clusters (FALCs) are considered as a source of immune cells. We discovered lymphoid clusters (LCs) in mouse mediastinal fat tissues (MFTs). In Th1-biased C57BL/6N (B6), Th2-biased DBA/2Cr (DBA) and autoimmune-prone MRL/MpJ (MRL) mice strains, LCs without a fibrous capsule and germinal center were observed in white-colored MFTs extending from the diaphragm to the heart. The number and size of the LCs were larger in 12-month-old mice than in 3-month-old mice in all of the examined strains. Moreover, B6 had an especially large number of LCs compared with DBA and MRL. The immune cells in the LCs consisted of mainly T-cells and some B-cells. The majority of T-cells were CD4+ helper T (Th) cells, rather than CD8+ cytotoxic T-cells and no obvious immune cell population difference was present among the strains. Furthermore, high endothelial venules and lymphatic vessels in the LCs were better developed in B6 mice than in the other strains. Interestingly, some CD133+ hematopoietic progenitor cells and some c-Kit+/CD127+ natural helper cells were detected in the LCs. BrdU+ proliferating cells were more abundant in the LCs of B6 mice than in the LCs of the other strains and the number of BrdU+ cells increased with age. This is the first report of LCs in mouse MFTs. We suggest that the mouse genetic background affects LC size and number. We term the LCs "mediastinal fat-associated lymphoid clusters". These clusters can be considered as niches for Th cell production.

Human immunity in vitro - solving immunogenicity and more

It has been widely recognised that the phylogenetic distance between laboratory animals and humans limits the former's predictive value for immunogenicity testing of biopharmaceuticals and nanostructure-based drug delivery and adjuvant systems. 2D in vitro assays have been established in conventional culture plates with little success so far. Here, we detail the status of various 3D approaches to emulate innate immunity in non-lymphoid organs and adaptive immune response in human professional lymphoid immune organs in vitro. We stress the tight relationship between the necessarily changing architecture of professional lymphoid organs at rest and when activated by pathogens, and match it with the immunity identified in vitro. Recommendations for further improvements of lymphoid tissue architecture relevant to the development of a sustainable adaptive immune response in vitro are summarized. In the end, we sketch a forecast of translational innovations in the field to model systemic innate and adaptive immunity in vitro.

Sphingosine-1-phosphate receptor 1 reporter mice reveal receptor activation sites in vivo

Activation of the GPCR sphingosine-1-phosphate receptor 1 (S1P1) by sphingosine-1-phosphate (S1P) regulates key physiological processes. S1P1 activation also has been implicated in pathologic processes, including autoimmunity and inflammation; however, the in vivo sites of S1P1 activation under normal and disease conditions are unclear. Here, we describe the development of a mouse model that allows in vivo evaluation of S1P1 activation. These mice, known as S1P1 GFP signaling mice, produce a S1P1 fusion protein containing a transcription factor linked by a protease cleavage site at the C terminus as well as a β-arrestin/protease fusion protein. Activated S1P1 recruits the β-arrestin/protease, resulting in the release of the transcription factor, which stimulates the expression of a GFP reporter gene. Under normal conditions, S1P1 was activated in endothelial cells of lymphoid tissues and in cells in the marginal zone of the spleen, while administration of an S1P1 agonist promoted S1P1 activation in endothelial cells and hepatocytes. In S1P1 GFP signaling mice, LPS-mediated systemic inflammation activated S1P1 in endothelial cells and hepatocytes via hematopoietically derived S1P. These data demonstrate that S1P1 GFP signaling mice can be used to evaluate S1P1 activation and S1P1-active compounds in vivo. Furthermore, this strategy could be potentially applied to any GPCR to identify sites of receptor activation during normal physiology and disease.

Emerging roles of lymphatic endothelium in regulating adaptive immunity

Emerging research on the roles of stromal cells in modulating adaptive immune responses has included a new focus on lymphatic endothelial cells (LECs). LECs are presumably the first cells that come into direct contact with peripheral antigens, cytokines, danger signals, and immune cells travelling from peripheral tissues to lymph nodes. LECs can modulate dendritic cell function, present antigens to T cells on MHC class I and MHC class II molecules, and express immunomodulatory cytokines and receptors, which suggests that their roles in adaptive immunity are far more extensive than previously realized. This Review summarizes the emergent evidence that LECs are important in maintaining peripheral tolerance, limiting and resolving effector T cell responses, and modulating leukocyte function.

Reactive oxygen species in inflammation and tissue injury

Abstract Reactive oxygen species (ROS) are key signaling molecules that play an important role in the progression of inflammatory disorders. An enhanced ROS generation by polymorphonuclear neutrophils (PMNs) at the site of inflammation causes endothelial dysfunction and tissue injury. The vascular endothelium plays an important role in passage of macromolecules and inflammatory cells from the blood to tissue. Under the inflammatory conditions, oxidative stress produced by PMNs leads to the opening of inter-endothelial junctions and promotes the migration of inflammatory cells across the endothelial barrier. The migrated inflammatory cells not only help in the clearance of pathogens and foreign particles but also lead to tissue injury. The current review compiles the past and current research in the area of inflammation with particular emphasis on oxidative stress-mediated signaling mechanisms that are involved in inflammation and tissue injury.

Endothelium and its alterations in cardiovascular diseases: life style intervention

The endothelium, which forms the inner cellular lining of blood vessels and lymphatics, is a highly metabolically active organ that is involved in many physiopathological processes, including the control of vasomotor tone, barrier function, leukocyte adhesion, and trafficking and inflammation. In this review, we summarized and described the following: (i) endothelial cell function in physiological conditions and (ii) endothelial cell activation and dysfunction in the main cardiovascular diseases (such as atherosclerosis, and hypertension) and to diabetes, cigarette smoking, and aging physiological process. Finally, we presented the currently available evidence that supports the beneficial effects of physical activity and various dietary compounds on endothelial functions.

Gene expression profiles of human adipose tissue-derived mesenchymal stem cells are modified by cell culture density

Previous studies conducted cell expansion ex vivo using low initial plating densities for optimal expansion and subsequent differentiation of mesenchymal stem cells (MSCs). However, MSC populations are heterogeneous and culture conditions can affect the characteristics of MSCs. In this study, differences in gene expression profiles of adipose tissue (AT)-derived MSCs were examined after harvesting cells cultured at different densities. AT-MSCs from three different donors were plated at a density of 200 or 5,000 cells/cm². After 7 days in culture, detailed gene expression profiles were investigated using a DNA chip microarray, and subsequently validated using a reverse transcription polymerase chain reaction (RT-PCR) analysis. Gene expression profiles were influenced primarily by the level of cell confluence at harvest. In MSCs harvested at ∼90% confluence, 177 genes were up-regulated and 102 genes down-regulated relative to cells harvested at ∼50% confluence (P<0.05, FC>2). Proliferation-related genes were highly expressed in MSCs harvested at low density, while genes that were highly expressed in MSCs harvested at high density (∼90% confluent) were linked to immunity and defense, cell communication, signal transduction and cell motility. Several cytokine, chemokine and growth factor genes involved in immunosuppression, migration, and reconstitution of damaged tissues were up-regulated in MSCs harvested at high density compared with MSCs harvested at low density. These results imply that cell density at harvest is a critical factor for modulating the specific gene-expression patterns of heterogeneous MSCs.

Innate immunity in myasthenia gravis thymus: pathogenic effects of Toll-like receptor 4 signaling on autoimmunity

The thymus is the main site of immune sensitization to AChR in myasthenia gravis (MG). In our previous studies we demonstrated that Toll-like receptor (TLR) 4 is over-expressed in MG thymuses, suggesting its involvement in altering the thymic microenvironment and favoring autosensitization and autoimmunity maintenance processes, via an effect on local chemokine/cytokine network. Here, we investigated whether TLR4 signaling may favor abnormal cell recruitment in MG thymus via CCL17 and CCL22, two chemokines known to dictate immune cell trafficking in inflamed organs by binding CCR4. We also investigated whether TLR4 activation may contribute to immunodysregulation, via the production of Th17-related cytokines, known to alter effector T cell (Teff)/regulatory T cell (Treg) balance. We found that CCL17, CCL22 and CCR4 were expressed at higher levels in MG compared to normal thymuses. The two chemokines were mainly detected around medullary Hassall's corpuscles (HCs), co-localizing with TLR4(+) thymic epithelial cells (TECs) and CCR4(+) dendritic cells (DCs), that were present in higher number in MG thymuses compared to controls. TLR4 stimulation in MG TECs increased CCL17 and CCL22 expression and induced the production of Th17-related cytokines. Then, to study the effect of TLR4-stimulated TECs on immune cell interactions and Teff activation, we generated an in-vitro imaging model by co-culturing CD4(+) Th1/Th17 AChR-specific T cells, naïve CD4(+)CD25(+) Tregs, DCs and TECs from Lewis rats. We observed that TLR4 stimulation led to a more pronounced Teff activatory status, suggesting that TLR4 signaling in MG thymic milieu may affect cell-to-cell interactions, favoring autoreactive T-cell activation. Altogether our findings suggest a role for TLR4 signaling in driving DC recruitment in MG thymus via CCL17 and CCL22, and in generating an inflammatory response that might compromise Treg function, favoring autoreactive T-cell pathogenic responses.

Dynamic changes in endothelial cell adhesion molecule nepmucin/CD300LG expression under physiological and pathological conditions

Vascular endothelial cells often change their phenotype to adapt to their local microenvironment. Here we report that the vascular endothelial adhesion molecule nepmucin/CD300LG, which is implicated in lymphocyte binding and transmigration, shows unique expression patterns in the microvascular endothelial cells of different tissues. Under physiological conditions, nepmucin/CD300LG was constitutively and selectively expressed at the luminal surface of the small arterioles, venules, and capillaries of most tissues, but it was only weakly expressed in the microvessels of the splenic red pulp and thymic medulla. Furthermore, it was barely detectable in immunologically privileged sites such as the brain, testis, and uterus. The nepmucin/CD300LG expression rapidly decreased in lymph nodes receiving acute inflammatory signals, and this loss was mediated at least in part by TNF-α. It was also down-regulated in tumors and tumor-draining lymph nodes, indicating that nepmucin/CD300LG expression is negatively regulated by locally produced signals under these circumstances. In contrast, nepmucin/CD300LG was induced in the high endothelial venule-like blood vessels of chronically inflamed pancreatic islets in an animal model of non-obese diabetes. Interestingly, the activated CD4⁺ T cells infiltrating the inflamed pancreas expressed high levels of the nepmucin/CD300LG ligand(s), supporting the idea that nepmucin/CD300LG and its ligand interactions are locally involved in pathological T cell trafficking. Taken together, these observations indicate that the nepmucin/CD300LG expression in microvascular endothelial cells is influenced by factor(s) that are locally produced in tissues, and that its expression is closely correlated with the level of leukocyte infiltration in certain tissues.

Dendritic cells in tumor-associated tertiary lymphoid structures signal a Th1 cytotoxic immune contexture and license the positive prognostic value of infiltrating CD8+ T cells

Tumor-infiltrating T cells, particularly CD45RO(+)CD8(+) memory T cells, confer a positive prognostic value in human cancers. However, the mechanisms that promote a protective T-cell response in the tumor microenvironment remain unclear. In chronic inflammatory settings such as the tumor microenvironment, lymphoid neogenesis can occur to create local lymph node-like structures known as tertiary lymphoid structures (TLS). These structures can exacerbate a local immune response, such that TLS formation in tumors may help promote an efficacious immune contexture. However, the role of TLS in tumors has yet to be investigated carefully. In lung tumors, mature dendritic cells (DC) present in tumor-associated TLS can provide a specific marker of these structures. In this study, we evaluated the influence of TLS on the characteristics of the immune infiltrate in cohorts of prospective and retrospective human primary lung tumors (n = 458). We found that a high density of mature DC correlated closely to a strong infiltration of T cells that are predominantly of the effector-memory phenotype. Moreover, mature DC density correlated with expression of genes related to T-cell activation, T-helper 1 (Th1) phenotype, and cytotoxic orientation. Lastly, a high density of TLS-associated DC correlated with long-term survival, which also allowed a distinction of patients with high CD8(+) T-cell infiltration but a high risk of death. Taken together, our results show how tumors infiltrated by TLS-associated mature DC generate a specific immune contexture characterized by a strong Th1 and cytotoxic orientation that confers the lowest risk of death. Furthermore, our findings highlight the pivotal function of TLS in shaping the immune character of the tumor microenvironment, in promoting a protective immune response mediated by T cells against cancer.

A mechanism for selective lymphocyte homing in bovine hemal nodes

The distribution and abundance of MECA-79(+) cells in bovine hemal nodes (HNs) was analyzed. In addition, T cell subsets which expressed the homing receptor l-selectin were analyzed by flow cytometry. The frequency of MECA-79(+) HNs varied depending on the location. There were 61, 33, and 17% MECA-79(+) HN in the subcutaneous region, along the abdominal aorta and in the mesenteric region, respectively. MECA-79(+) cells in mesenteric lymph nodes were mainly distributed in the paracortex. Many MECA-79(+) cells were distributed in the perifollicular area of HNs and a few positive cells were also located in the paracortical and interfollicular areas. CD4(+) and CD8(+)l-selectin(+) cells were significantly higher in MECA-79(+) HNs compared to MECA-79(-) HNs. The data suggest that a selective lymphocyte homing mechanism exists in bovine HNs, which could be related to functional differences between locations.

M1 macrophages act as LTβR-independent lymphoid tissue inducer cells during atherosclerosis-related lymphoid neogenesis

AIMS

The goal of this study was to characterize the role of inflammatory macrophages in the induction of the vascular smooth muscle cell (VSMC)-mediated formation of aortic tertiary lymphoid organs (TLOs).

METHODS AND RESULTS

Mouse bone marrow-derived M1 macrophages acted as lymphoid tissue inducer cells. Indeed, they expressed high levels of tumour necrosis factor (TNF)-α and membrane-bound lymphotoxin (LT)-α, two inducing cytokines that triggered expression of the chemokines CCL19, CCL20, and CXCL16, as did M1 supernatant. The blockade of LTβR signalling with LTβR-Ig had no effect, whereas that of TNFR1/2 signalling reduced chemokine expression by VSMCs in both wild-type (WT) and LTβR KO mice, demonstrating that LTβR signalling is dispensable for the M1-inducing effect. This effect was corroborated by the development of TLOs observed in LTβR KO->apolipoprotein E knockout (ApoE KO) aortic segments after orthotopic transplantation. Furthermore, treatment of ApoE KO mice with anti-TNF-α antibody decreased the number and incidence of aortic TLOs. Finally, lymphoid nodules composed of T and B cells formed in in vivo-implanted scaffolds seeded with VSMCs previously stimulated ex vivo by M1-conditioned medium.

CONCLUSIONS

These results are the first to identify M1 macrophages as inducer cells that trigger the expression of chemokines by VSMCs independently of LTβR signalling. We propose that the dialogue between macrophages and VSMCs-established across the vascular wall-contributes to the formation of aortic TLOs.

Oral Administration of EC-12 Increases the Baseline Gene Expression of Antiviral Cytokine Genes, IFN-γ and TNF-α, in Splenocytes and Mesenteric Lymph Node Cells of Weaning Piglets

Weaning piglets are continuously exposed to various viruses. The antiviral effects of lactic acid bacteria (LAB) have been confirmed mainly in humans and mice, while few studies have been conducted in livestock. In this study, we evaluated the effect of oral administration of Enterococcus faecalis strain EC-12 (EC-12) on the gene expressions of antiviral cytokines in weaning piglets. Piglets were allocated to the EC-12-administered group (E group) and the no-treatment control group (C group). The small intestinal tissue, the mesenteric lymph node (MLN) cells and the splenocytes were collected from the piglets. The tissue and cells were co-cultured with a live vaccine of porcine reproductive respiratory syndrome virus, porcine epidemic diarrhea virus or EC-12. After the incubation, the gene expressions of IFN-γ and TNF-α in the tissue and cells were evaluated. The gene expressions of IFN-γ in the MLN cells and TNF-α in the splenocytes were significantly higher in the E group than in the C group. However, the increase in the gene expression of antiviral cytokines was observed independently of the antigen treatments. The results of the present study suggest that oral administration of EC-12 did not increase the response of immune cells to specific viral antigens but increased the baseline gene expression of antiviral cytokines.

Characteristics of tertiary lymphoid structures in primary cancers

Tumors are sustained by complex networks of interactions between malignant cells, stromal cells and tumor-infiltrating immune cells. These networks differ from patient to patient in terms of nature, composition and organization as well as with regard to the precise localization of tumor-infiltrating cells. Of note, the heterogeneity of the immunological component of the tumor microenvironment, as opposed to its mere abundance, has been shown to influence disease outcome. However, a key question remains: where does the activation of tumor-specific T cells take place? The recently described, tumor-associated lymph node-like entities termed “tertiary lymphoid structures” exhibit a structural organization that is reminiscent of secondary lymphoid organs, and thus may imprint the local immune contexture. Here, we discuss how cancer-associated tertiary lymphoid structures impact on the tumor micro-architecture, immune microenvironment, and ultimately, patient survival.

Identification of a new stromal cell type involved in the regulation of inflamed B cell follicles

Identification of a new stromal cell type in mouse lymph nodes that can be activated by B cells to delineate the transient boundaries of B cell zones during inflammation

Lymph node (LN) stromal cells provide survival signals and adhesive substrata to lymphocytes. During an immune response, B cell follicles enlarge, questioning how LN stromal cells manage these cellular demands. Herein, we used a murine fate mapping system to describe a new stromal cell type that resides in the T cell zone of resting LNs. We demonstrated that upon inflammation, B cell follicles progressively trespassed into the adjacent T cell zone and surrounded and converted these stromal cells into CXCL13 secreting cells that in return delineated the new boundaries of the growing follicle. Acute B cell ablation in inflamed LNs abolished CXCL13 secretion in these cells, while LT-β deficiency in B cells drastically affected this conversion. Altogether, we reveal the existence of a dormant stromal cell subset that can be functionally awakened by B cells to delineate the transient boundaries of their expanding territories upon inflammation.

Immune responses develop in lymphoid organs such as the tonsils and lymph nodes (LNs), which are composed of leukocytes (95%) and architectural stromal cells (5%). LNs involved in mounting an immune response recruit large numbers of lymphocytes and support the division of those that recognise the foreign antigen, raising the question of how LN stromal cells manage this tremendous remodeling. In this study, we focused on specific zones within the lymph node called germinal centres that comprise dense aggregates or follicles of B lymphocytes, and investigated how lymphoid stromal cells contribute to the reorganization of primary B cell follicles into large reactive secondary follicles. Using a fate mapping system in mice, we identified a new stromal cell type that resides in the T cell zone of noninflamed resting LNs. We demonstrate that upon inflammation, B cells usually contained within B cell follicles progressively trespass into the adjacent T cell zone and surround and convert resident stromal cells into cells that can secrete CXCL13, a B cell chemokine. These CXCL13-secreting cells in turn act to delineate the new transient boundaries of the growing follicle. Identification of this distinct versatile stromal cell type adds to our understanding of mechanisms underlying compartmentalization of lymphoid organs into their functional zones.

Lymphocyte recruitment via high endothelial venules in lymphoid stroma of Warthin's tumour

AIMS

Warthin's tumour is composed of bilayered oncocytic epithelium and organised lymphoid stroma, which resembles mucosa-associated lymphoid tissue (MALT); however, the histogenesis of the lymphoid stroma is not fully understood. We hypothesised that lymphocytes consisting of the stroma are recruited via high endothelial venules (HEVs) by the mechanism operating in normal lymphocyte homing in secondary lymphoid organs. The aim of this study was to determine immunohistochemically the molecules expressed on these HEVs.

METHODS

Tissue sections of Warthin's tumour (n = 10) were immunostained for vascular addressin-related antigens including peripheral lymph node addressin (PNAd) and mucosal addressin cell adhesion molecule 1 (MAdCAM-1). An L-selectin·IgM chimera in situ binding assay was also carried out. Triple immunostaining for PNAd, CD3, and CD20/CD79α was performed to determine which lymphocyte subsets are closely associated with these HEVs.

RESULTS

HEVs in the lymphoid stroma of Warthin's tumour express PNAd, which is detected by MECA-79 as well as recently developed monoclonal antibodies S1 and S2. These HEVs were bound by L-selectin·IgM chimeras in a calcium-dependent manner, and numbers of lymphocytes, particularly T cells, attached to these HEVs.

CONCLUSIONS

The lymphoid stroma of Warthin's tumour is most likely developed by lymphocytes recruited via HEVs.

Diffuse large B-cell lymphoma and mantle cell lymphoma of the ocular adnexal region, and lymphoma of the lacrimal gland: an investigation of clinical and histopathological features

Diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) constitute two distinct subtypes of non-Hodgkin lymphoma (NHL) associated with considerable morbidity and mortality. Marked diversities with regard to molecular biology and clinical features are recognized in different subsets of the two lymphomas. Because these differences could be related to the location of the lymphoma, it is of interest to investigate the clinical and histopathological features of DLBCL and MCL involving the ocular adnexal region (i.e. the orbit, eyelids, conjunctiva, lacrimal gland and lacrimal sac). Similarly, the lacrimal gland is the only glandular structure within the orbit. Because the lacrimal gland represents an important part of the immunological system, it is of interest to investigate lymphomas involving this location with regard to clinical and histological characteristics.

PURPOSE

  To characterize the clinical and histopathological features of Danish patients with DLBCL of the ocular adnexal region between 1980 and 2009 and of Danish ocular adnexal MCL patients from 1980 to 2005. Furthermore, the aim of this PhD was to review all specimens from patients with lymphoma of the lacrimal gland in Denmark between 1975 and 2009 to determine the distribution of lymphoma subtypes of the lacrimal gland and to describe the clinicopathological features of these patients.

RESULTS

  A total of 34 patients with DLBCL and 21 with MCL of the ocular adnexal region were identified. Twenty-seven patients had lacrimal gland lymphoma, including four DLBCLs and three MCLs from studies I and II. Elderly patients predominated in all three groups, with median ages of 78, 75 and 69 years in the DLBCL, the MCL and the lacrimal gland lymphoma groups, respectively. MCL patients had a preponderance of males, whereas females prevailed among lacrimal gland lymphoma patients. The orbit was the most common site of involvement in DLBCL and MCL. Most DLBCL patients had unilateral involvement, while MCL patients had a high frequency of bilateral involvement. Similarly, localized lymphoma was relatively frequently seen in DLBCL patients in contrast to the predominance of disseminated lymphoma in the MCL group. The majority of lacrimal gland lymphomas were low grade, and the distribution of subtypes was as follows: extranodal marginal zone lymphoma, 10 (37%); follicular lymphoma, 5 (19%); DLBCL, 4 (15%); MCL, 3 (11%); chronic lymphocytic leukaemia/small lymphatic lymphoma, 2 (7%); and unclassified B-cell lymphoma, 3 (11%). The overall survival rates at 3 and 5 years for the entire study group of DLBCL were 42% and 20%, whereas 58% and 22% of MCL patients were alive 3 and 5 years after the time of diagnosis. The 5-year overall survival rate of lacrimal gland lymphoma patients was 70%. Concordant bone marrow involvement and the International Prognostic Index score were predictive factors for the overall survival in the DLBCL group in Cox regression analysis. Rituximab-containing chemotherapy was associated with an improved survival rate in MCL patients.

CONCLUSIONS

  Diffuse large B-cell lymphoma and MCL involving the ocular adnexal region and lymphoma of the lacrimal gland are prevalent among elderly patients. The overall prognosis in DLBCL and MCL was poor, whereas the prognosis for lacrimal gland lymphoma patients was relatively good. Concordant bone marrow involvement and the International Prognostic Index score were independent predictive factors for mortality in the DLBCL group. Chemotherapy containing rituximab significantly improved survival in the MCL group.

Endothelial cell heterogeneity

The endothelial lining of blood vessels shows remarkable heterogeneity in structure and function, in time and space, and in health and disease. An understanding of the molecular basis for phenotypic heterogeneity may provide important insights into vascular bed-specific therapies. First, we review the scope of endothelial heterogeneity and discuss its proximate and evolutionary mechanisms. Second, we apply these principles, together with their therapeutic implications, to a representative vascular bed in disease, namely, tumor endothelium.

Dendritic cell-based tumor vaccinations in epithelial ovarian cancer: a systematic review

After decades of extensive research, epithelial ovarian cancer still remains a lethal disease. Multiple new studies have reported that the immune system plays a critical role in the growth and spread of ovarian carcinoma. This review summarizes the development of dendritic cell (DC) vaccinations specific for ovarian cancer. So far, DC-based vaccines have induced effective antitumor responses in animal models, but only limited results from human clinical trials are available. Although DC-based immunotherapy has proven to be clinically safe and efficient at inducing tumor-specific immune responses, its clear role in the therapy of ovarian cancer still needs to be clarified. The relatively disappointing low-response rates in early clinical trials point to the need for the development of more effective and personalized DC-based anticancer vaccines. This article reviews the basic mechanisms, limitations and future directions of DC-based anti-ovarian cancer vaccine development.

Involvement of autotaxin/lysophospholipase D expression in intestinal vessels in aggravation of intestinal damage through lymphocyte migration

Lysophosphatidic acid (LPA) has a critical role in lymphocyte migration to secondary lymphoid organs. Autotaxin (ATX)/lysophospholipase D, in the vascular endothelium, is the main enzyme involved in LPA production. Whether ATX is involved in pathological lymphocyte migration to the inflamed mucosa has not been studied. We investigated the involvement of ATX in inflammatory bowel disease patients and two murine models of colitis. Tissue samples were obtained by intestinal biopsies from patients with Crohn's disease and those with ulcerative colitis with informed consent. ATX immunoreactivity was colocalized with MAdCAM-1-positive high-endothelial-like vessels, close to sites of lymphocyte infiltration. Enhanced expression of ATX mRNA was observed in the inflamed mucosa from Crohn's disease and ulcerative colitis patients. ATX mRNA expression level was remarkably higher in the actively inflamed mucosa than in the quiescent mucosa in the same patient. In the T-cell-transferred mouse model, ATX mRNA expression level gradually increased as colitis developed. In the dextran sodium sulfate mouse model, the expression level was considerably higher in colonic mucosa of chronically developed colitis than in colonic mucosa of acute colitis. Administration of an ATX inhibitor, bithionol, remarkably decreased lymphocyte migration to the intestine and ameliorated both dextran sodium sulfate-induced colitis and CD4-induced ileocolitis. In transwell assays, administration of bithionol or 1-bromo-3(s)-hydroxy-4-(palmitoyloxy) butylphosphonate (BrP-LPA) significantly decreased transmigration of splenocytes through high-endothelial-like vessels induced by TNF-α. We conclude that enhanced expression of ATX in the active mucosa has been implicated in the pathophysiology of inflammatory bowel disease through enhancing aberrant lymphocyte migration to the inflamed mucosa.

CBAP functions as a novel component in chemokine-induced ZAP70-mediated T-cell adhesion and migration

Activated chemokine receptor initiates inside-out signaling to transiently trigger activation of integrins, a process involving multiple components that have not been fully characterized. Here we report that GM-CSF/IL-3/IL-5 receptor common beta-chain-associated protein (CBAP) is required to optimize this inside-out signaling and activation of integrins. First, knockdown of CBAP expression in human Jurkat T cells caused attenuated CXC chemokine ligand-12 (CXCL12)-induced cell migration and integrin α4β1- and αLβ2-mediated cell adhesion in vitro, which could be rescued sufficiently upon expression of murine CBAP proteins. Freshly isolated CBAP-deficient primary T cells also exhibited diminution of chemotaxis toward CC chemokine ligand-21 (CCL21) and CXCL12, and these chemokines-induced T-cell adhesions in vitro. Adoptive transfer of isolated naive T cells demonstrated that CBAP deficiency significantly reduced lymph node homing ability in vivo. Finally, migration of T cell-receptor-activated T cells induced by inflammatory chemokines was also attenuated in CBAP-deficient cells. Further analyses revealed that CBAP constitutively associated with both integrin β1 and ZAP70 and that CBAP is required for chemokine-induced initial binding of the talin-Vav1 complex to integrin β1 and to facilitate subsequent ZAP70-mediated dissociation of the talin-Vav1 complex and Vav1 phosphorylation. Within such an integrin signaling complex, CBAP likely functions as an adaptor and ultimately leads to activation of both integrin α4β1 and Rac1. Taken together, our data suggest that CBAP indeed can function as a novel signaling component within the ZAP70/Vav1/talin complex and plays an important role in regulating chemokine-promoted T-cell trafficking.

Recent advance in lymph dynamic analysis in lymphatics and lymph nodes

Lymphatics are a unidirectional transport system that carries fluid from the interstitial space and back into the blood stream. Initial lymphatics take up not only fluid but also high-molecular-weight substances, such as plasma proteins and hyaluronan; immune cells, such as lymphocytes, macrophages, and dendritic cells; and colloidal particles, such as carbon particles, bacteria, and tattoo dye. Interstitially injected colloidal particles are known to accumulate in the regional lymph nodes. This phenomenon is applied to find sentinel lymph nodes in cancer patients. Lymph flow rate and composition are influenced by interstitial fluid, lymphatic pump activity, and intra-lymphatic pressure. Lymph composition is changed during its flow downstream. In this review, the main focus is on the mechanisms of lymph formation at the initial lymphatics and lymph transport through the collecting lymphatics and lymph nodes. (*English Translation of J Jpn Coll Angiol, 2008, 48: 113-123.).

Endothelial junction regulation: a prerequisite for leukocytes crossing the vessel wall

The leukocytes of the innate immune system, especially neutrophils and monocytes, exit the circulation early in the response to local inflammation and infection. This is necessary to control and prevent the spread of infections before an adaptive immune response can be raised. The endothelial cells and the intercellular junctions that connect them form a barrier that leukocytes need to pass in order to get to the site of inflammation. The junctions are tightly regulated which ensures that leukocytes only exit when and where they are needed. This regulation is disturbed in many chronic inflammatory diseases which are characterized by ongoing recruitment and interstitial accumulation of leukocytes. In this review, we summarize the molecular mechanisms that regulate endothelial cell-cell junctions and prevent or permit leukocyte transendothelial migration.

Nitric oxide and TNFα are critical regulators of reversible lymph node vascular remodeling and adaptive immune response

Lymph node (LN) vascular growth, at the level of the main arteriole, was recently characterized for the first time during infection. Arteriole diameter was shown to increase for at least seven days and to occur via a CD4⁺ T cell dependent mechanism, with vascular expansion playing a critical role in regulating induction of adaptive immune response. Here, using intravital microscopy of the inguinal LN during herpes simplex type II (HSV-2) infection, the data provides the first studies that demonstrate arteriole expansion during infection is a reversible vascular event that occurs via eutrophic outward remodeling. Furthermore, using genetic ablation models, and pharmacological blockade, we reveal arteriole remodeling and LN hypertrophy to be dependent upon both endothelial nitric oxide synthase (eNOS) and TNFα expression. Additionally, we reveal transient changes in nitric oxide (NO) levels to be a notable feature of response to viral infection and LN vascular remodeling and provide evidence that mast cells are the critical source of TNFα required to drive arteriole remodeling. Overall, this study is the first to fully characterize LN arteriole vascular changes throughout the course of infection. It effectively reveals a novel role for NO and TNFα in LN cellularity and changes in LN vascularity, which represent key advances in understanding LN vascular physiology and adaptive immune response.

Polysaccharide-protein conjugate vaccination induces antibody production but not sustained B-cell memory in the human nasopharyngeal mucosa

Colonization of the nasopharyngeal mucosa by meningococcus and other polysaccharide (PS)-encapsulated bacteria precedes invasion. PS-conjugate vaccines induce PS-specific B-cell memory (B(MEM)) and also prevent colonization, thus blocking person-to-person transmission, generating herd protection. However, in isolation the B(MEM) are unable to sustain immunity. Furthermore, the duration of herd protection the vaccines induce appears limited. We demonstrate that, despite the persistence of PS-specific B(MEM), the population is not maintained within the nasopharynx. Although booster immunization results in the transient appearance of PS-specific B(MEM) within the mucosa, this reflects the re-circulation of systemic B(MEM) through the site rather than the generation of resident mucosal B(MEM). The induction of sustained PS-specific B(MEM) in the nasopharynx would allow the population to be activated by colonization, thus inhibiting subsequent invasion. It would also be expected to boost local mucosal immunity, thus extending herd protection. Strategies to generate PS-specific B(MEM) in the mucosa warrant further investigation.

Constitutive lymphocyte transmigration across the basal lamina of high endothelial venules is regulated by the autotaxin/lysophosphatidic acid axis

Lymphocyte extravasation from the high endothelial venules (HEVs) of lymph nodes is crucial for the maintenance of immune homeostasis, but its molecular mechanism remains largely unknown. In this article, we report that lymphocyte transmigration across the basal lamina of the HEVs is regulated, at least in part, by autotaxin (ATX) and its end-product, lysophosphatidic acid (LPA). ATX is an HEV-associated ectoenzyme that produces LPA from lysophosphatidylcholine (LPC), which is abundant in the systemic circulation. In agreement with selective expression of ATX in HEVs, LPA was constitutively and specifically detected on HEVs. In vivo, inhibition of ATX impaired the lymphocyte extravasation from HEVs, inducing lymphocyte accumulation within the endothelial cells (ECs) and sub-EC compartment; this impairment was abrogated by LPA. In vitro, both LPA and LPC induced a marked increase in the motility of HEV ECs; LPC's effect was abrogated by ATX inhibition, whereas LPA's effect was abrogated by ATX/LPA receptor inhibition. In an in vitro transmigration assay, ATX inhibition impaired the release of lymphocytes that had migrated underneath HEV ECs, and these defects were abrogated by LPA. This effect of LPA was dependent on myosin II activity in the HEV ECs. Collectively, these results strongly suggest that HEV-associated ATX generates LPA locally; LPA, in turn, acts on HEV ECs to increase their motility, promoting dynamic lymphocyte-HEV interactions and subsequent lymphocyte transmigration across the basal lamina of HEVs at steady state.

Prions and lymphoid organs: solved and remaining mysteries

Prion colonization of secondary lymphoid organs (SLOs) is a critical step preceding neuroinvasion in prion pathogenesis. Follicular dendritic cells (FDCs), which depend on both tumor necrosis factor receptor 1 (TNFR1) and lymphotoxin β receptor (LTβR) signaling for maintenance, are thought to be the primary sites of prion accumulation in SLOs. However, prion titers in RML-infected TNFR1 (-/-) lymph nodes and rates of neuroinvasion in TNFR1 (-/-) mice remain high despite the absence of mature FDCs. Recently, we discovered that TNFR1-independent prion accumulation in lymph nodes relies on LTβR signaling. Loss of LTβR signaling in TNFR1 (-/-) lymph nodes coincided with the de-differentiation of high endothelial venules (HEVs)-the primary sites of lymphocyte entry into lymph nodes. These findings suggest that HEVs are the sites through which prions initially invade lymph nodes from the bloodstream. Identification of HEVs as entry portals for prions clarifies a number of previous observations concerning peripheral prion pathogenesis. However, a number of questions still remain: What is the mechanism by which prions are taken up by HEVs? Which cells are responsible for delivering prions to lymph nodes? Are HEVs the main entry site for prions into lymph nodes or do alternative routes also exist? These questions and others are considered in this article.

Endothelial cells derived from nuclear reprogramming

The endothelium plays a pivotal role in vascular homeostasis, regulating the tone of the vascular wall, and its interaction with circulating blood elements. Alterations in endothelial functions facilitate the infiltration of inflammatory cells and permit vascular smooth muscle proliferation and platelet aggregation. Therefore, endothelial dysfunction is an early event in disease processes including atherosclerosis, and because of its critical role in vascular health, the endothelium is worthy of the intense focus it has received. However, there are limitations to studying human endothelial function in vivo, or human vascular segments ex vivo. Thus, methods for endothelial cell (EC) culture have been developed and refined. Recently, methods to derive ECs from pluripotent cells have extended the scientific range of human EC studies. Pluripotent stem cells may be generated, expanded, and then differentiated into ECs for in vitro studies. Constructs for molecular imaging can also be employed to facilitate tracking these cells in vivo. Furthermore, one can generate patient-specific ECs to study the effects of genetic or epigenetic alterations on endothelial behavior. Finally, there is the opportunity to apply these cells for vascular therapy. This review focuses on the generation of ECs from stem cells; their characterization by genetic, histological, and functional studies; and their translational applications.

Inflammatory chemokines direct and restrict leukocyte migration within live tissues as glycan-bound gradients

Chemokines are essential in many cell migration processes, including the recruitment of leukocytes to sites of infection. In the latter context, chemokines promote leukocyte extravasation into the relevant tissue through a well-studied cascade of events. It is widely believed that chemokines further guide leukocytes within tissues via chemotaxis, the directed migration along gradients of soluble ligands. However, the basic mechanism of chemokine action within tissues has yet to be formally addressed in vivo. We identified a chemokine (zCxcl8) that recruits zebrafish neutrophils to infection loci and analyzed its function directly within interstitial tissues of living larvae. Using noninvasive imaging and a controlled cellular source of zCxcl8, we found that zCxcl8 guides neutrophils in a 2-fold manner: by biasing cell speed according to direction (orthotaxis) and by restricting cell motility near the source. We further show that zCxcl8 establishes tissue-bound gradients in vivo by binding to heparan sulfate proteoglycans (HSPGs). Inhibition of this interaction compromised both directional guidance and restriction of neutrophil motility. Thus, by interacting with extracellular HSPGs, chemokines establish robust surface-bound (haptotactic) gradients that mediate both recruitment and retention of leukocytes at sites of infection.

Homing of human B cells to lymphoid organs and B-cell lymphoma engraftment are controlled by cell adhesion molecule JAM-C

Junctional adhesion molecule C (JAM-C) is expressed by vascular endothelium and human but not mouse B lymphocytes. The level of JAM-C expression defines B-cell differentiation stages and allows the classification of marginal zone-derived (JAM-C-positive) and germinal center-derived (JAM-C-negative) B-cell lymphomas. In the present study, we investigated the role of JAM-C in homing of human B cells, using a xenogeneic nonobese diabetic/severe combined immunodeficient mouse model. Treatment with anti-JAM-C antibodies in short-term experiments reduced migration of normal and malignant JAM-C-expressing B cells to bone marrow, lymph nodes, and spleen. Blocking homing to the spleen is remarkable, as most other antiadhesion antibodies reduce homing of B cells only to bone marrow and lymph nodes. Long-term administration of anti-JAM-C antibodies prevented engraftment of JAM-Cpos lymphoma cells in bone marrow, spleen, and lymph nodes of mice. Plasmon resonance studies identified JAM-B as the major ligand for JAM-C, whereas homotypic JAM-C interactions remained at background levels. Accordingly, anti-JAM-C antibodies blocked adhesion of JAM-C-expressing B cells to their ligand JAM-B, and immunofluorescence analysis showed the expression of JAM-B on murine and human lymphatic endothelial cells. Targeting JAM-C could thus constitute a new therapeutic strategy to prevent lymphoma cells from reaching supportive microenvironments not only in the bone marrow and lymph nodes but also in the spleen.

Application of tissue engineering to the immune system: development of artificial lymph nodes

The goal of tissue engineering and regenerative medicine is to develop synthetic versions of human organs for transplantation, in vitro toxicology testing and to understand basic mechanisms of organ function. A variety of different approaches have been utilized to replicate the microenvironments found in lymph nodes including the use of a variety of different bio-materials, culture systems, and the application of different cell types to replicate stromal networks found in vivo. Although no system engineered so far can fully replicate lymph node function, progress has been made in the development of microenvironments that can promote the initiation of protective immune responses. In this review we will explore the different approaches utilized to recreate lymph node microenvironments and the technical challenges required to recreate a fully functional immune system in vitro.

Endothelial endoglin is involved in inflammation: role in leukocyte adhesion and transmigration

Human endoglin is an RGD-containing transmembrane glycoprotein identified in vascular endothelial cells. Although endoglin is essential for angiogenesis and its expression is up-regulated in inflammation and at sites of leukocyte extravasation, its role in leukocyte trafficking is unknown. This function was tested in endoglin heterozygous mice (Eng(+/-)) and their wild-type siblings Eng(+/+) treated with carrageenan or LPS as inflammatory agents. Both stimuli showed that inflammation-induced leukocyte transendothelial migration to peritoneum or lungs was significantly lower in Eng(+/-) than in Eng(+/+) mice. Leukocyte transmigration through cell monolayers of endoglin transfectants was clearly enhanced in the presence of endoglin. Coating transwells with the RGD-containing extracellular domain of endoglin, enhanced leukocyte transmigration, and this increased motility was inhibited by soluble endoglin. Leukocytes stimulated with CXCL12, a chemokine involved in inflammation, strongly adhered to endoglin-coated plates and to endoglin-expressing endothelial cells. This endoglin-dependent adhesion was abolished by soluble endoglin, RGD peptides, the anti-integrin α5β1 inhibitory antibody LIA1/2 and the chemokine receptor inhibitor AMD3100. These results demonstrate for the first time that endothelial endoglin interacts with leukocyte integrin α5β1 via its RGD motif, and this adhesion process is stimulated by the inflammatory chemokine CXCL12, suggesting a regulatory role for endoglin in transendothelial leukocyte trafficking.

In vivo imaging of therapy-induced anti-cancer immune responses in humans

Immunotherapy aims to re-engage and revitalize the immune system in the fight against cancer. Research over the past decades has shown that the relationship between the immune system and human cancer is complex, highly dynamic, and variable between individuals. Considering the complexity, enormous effort and costs involved in optimizing immunotherapeutic approaches, clinically applicable tools to monitor therapy-induced immune responses in vivo are most warranted. However, the development of such tools is complicated by the fact that a developing immune response encompasses several body compartments, e.g., peripheral tissues, lymph nodes, lymphatic and vascular systems, as well as the tumor site itself. Moreover, the cells that comprise the immune system are not static but constantly circulate through the vascular and lymphatic system. Molecular imaging is considered the favorite candidate to fulfill this task. The progress in imaging technologies and modalities has provided a versatile toolbox to address these issues. This review focuses on the detection of therapy-induced anticancer immune responses in vivo and provides a comprehensive overview of clinically available imaging techniques as well as perspectives on future developments. In the discussion, we will focus on issues that specifically relate to imaging of the immune system and we will discuss the strengths and limitations of the current clinical imaging techniques. The last section provides future directions that we envision to be crucial for further development.

Changes in specialized blood vessels in lymph nodes and their role in cancer metastasis

Background

High endothelial venules (HEV) have been recognized to play a role in metastasis by its changes seen in the cancer microenvironment of lymph nodes (LN) and solid cancers. Squamous cell carcinoma (SCC) of the tongue is a prevalent tumor of the head and neck region with high propensity for LN metastasis. The extent of LN metastasis is the most reliable adverse prognostic factor. Primary tumors can induce vasculature reorganization within sentinel LN before the arrival of tumor cells and HEV represents these remodelled vessels. This study aims to evaluate the cancer induced vascular changes in regional lymph nodes (LN) of patients by studying the morphological and functional alterations of HEV and its correlation with clinical outcome and pathological features.

Methods

This study was based on 65 patients with SCC tongue who underwent primary surgical treatment including neck dissection. The patients were categorized into 2 groups based on the presence of malignancy in their cervical lymph nodes. A review of the patients' pathological and clinical data was performed from a prospective database. Immunohistochemical staining of the tissue blocks for HEV and high-power-field image analysis were performed and analyzed with correlation to the patients' clinical and pathological features.

Results

The total number of HEV was found to be significantly associated to disease-free interval. There was a similar association comparing the HEV parameters to overall survival. The density of abnormal HEV was significantly higher in patients with established metastases in their lymph nodes and HEV was shown to be a better prognosis factor than conventional tumor staging. The HEV morphological metamorphosis demonstrates a spectrum that correlates well with disease progression and clinical outcome.

Conclusions

The results suggest that the HEV displays a spectrum of morphological changes in the presence of cancer and LN metastasis, and that HEV is possibly involved in the process of cancer metastasis. We revealed the relationship of HEV and their metamorphosis in pre-metastatic and metastatic environments in regional lymph nodes of tongue cancer patients in relation to clinical outcomes. The significant observation of modified dilated HEV containing red blood cells in lymph nodal basin of a cancer suggests the shifting of its function from one primarily of immune response to that of a blood carrying vessel. It also demonstrated potential prognostic value. More studies are needed to elucidate its potential role in cancer immunotherapy and as a potential novel therapeutic approach to preventing metastasis by manipulating the remodelling processes of HEV.