T lymphocyte-endothelial cell interactions

Neutrophil extracellular traps potentiate effector T cells via endothelial senescence in uveitis

Autoimmune uveitis (AU) is a sight-threatening ocular autoimmune disorder that often manifests as retinal vasculitis. Increased neutrophil infiltration around retinal vessels has been reported during the progression of AU, while how they function is not fully recognized. Neutrophil extracellular traps (NETs), produced by activated neutrophils, have been suggested to be detrimental in autoimmune diseases. Here, we found that NETs were elevated in patients with active AU, and this was verified in an experimental AU (EAU) mouse model. Depletion of neutrophils or degradation of NETs with deoxyribonuclease-I (DNase I) could decrease CD4+ effector T cell (Teff) infiltration in retina and spleen to alleviate EAU. Moreover, we found that the expression of adhesion molecules, selectin, and antigen-presenting molecules was elevated in EAU retina and in retinal microvascular endothelial cells (RMECs) cocultured with NETs. The stimulated RMECs further facilitated CD4+ T cell adhesion, activation, and differentiation into Teffs. Mechanistically, NETs trigger RMEC activation by hastening cell senescence through the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. Slowing down senescence or inhibiting the cGAS/STING pathway in RMECs reduces the activation and differentiation of CD4+ T cells. These results suggest a deleterious role of NETs in AU. Targeting NETs would offer an effective therapeutic method.

Unraveling Ferroptosis: A New Frontier in Combating Renal Fibrosis and CKD Progression

Chronic kidney disease (CKD) is a global health concern caused by conditions such as hypertension, diabetes, hyperlipidemia, and chronic nephritis, leading to structural and functional kidney injury. Kidney fibrosis is a common outcome of CKD progression, with abnormal fatty acid oxidation (FAO) disrupting renal energy homeostasis and leading to functional impairments. This results in maladaptive repair mechanisms and the secretion of profibrotic factors, and exacerbates renal fibrosis. Understanding the molecular mechanisms of renal fibrosis is crucial for delaying CKD progression. Ferroptosis is a type of discovered an iron-dependent lipid peroxidation-regulated cell death. Notably, Ferroptosis contributes to tissue and organ fibrosis, which is correlated with the degree of renal fibrosis. This study aims to clarify the complex mechanisms of ferroptosis in renal parenchymal cells and explore how ferroptosis intervention may help alleviate renal fibrosis, particularly by addressing the gap in CKD mechanisms related to abnormal lipid metabolism under the ferroptosis context. The goal is to provide a new theoretical basis for clinically delaying CKD progression.

Repeated CXCR4 Blockade by Plerixafor Attenuates Transplant Vasculopathy in Murine Aortic Allografts

Plerixafor, a hematopoietic stem cell mobilization agent, increases the peripheral blood content of effector and regulatory T cells and may have beneficial effects on cardiac allograft vasculopathy. The aim of the current study was to evaluate its effects in a murine aortic allograft model using different application procedures. Allogeneic donor aorta grafts (n = 8/group) from C57BL/6 mice(H2b) were abdominally transplanted into CBA mice (H2k). Plerixafor application was performed either continuously for 14 d using abdominally implanted osmotic pumps (1 mg/kg/d) or i.p. with a single dose (1 and 5 mg/kg) on day 0 or pulsed injections of 1 mg/kg on days 0, 7, 14, and 21. Cell distribution was monitored by FACS. Aortic grafts were evaluated for neointima development by Elastica-van-Gieson on day 30. Immunofluorescence and intragraft gene expression analysis were performed. On day 14, significantly fewer hematopoietic stem cells were found in the bone marrow of all plerixafor-treated mice. In the pulsed application group, significantly more hematopoietic stem cells were found in the peripheral blood on day 14 (0.045 ± 0.002%; p < 0.01 [pulsed]; versus 0.0068 ± 0.002% [control]) and also more regulatory T cells. PCR revealed lower inflammatory cytokines. The luminal occlusion was significantly reduced in the pulsed treated group (33.65 ± 8.84 versus 53.13 ± 12.41) going along with decreased neointimal CD4+ T cell and plasmacytoid dendritic cell infiltration, as well as less smooth muscle cell proliferation. The application of plerixafor attenuates chronic rejection in aortic allografts via immunomodulatory effects. Injection of repeated low-dose plerixafor is the most effective application form in the aortic transplant model.

Allogeneic HLA Humoral Immunogenicity and the Prediction of Donor-Specific HLA Antibody Development

The development of de novo donor-specific HLA antibodies (dnDSAs) following solid organ transplantation is considered a major risk factor for poor long-term allograft outcomes. The prediction of dnDSA development is a boon to transplant recipients, yet the assessment of allo-HLA immunogenicity remains imprecise. Despite the recent technological advances, a comprehensive evaluation of allo-HLA immunogenicity, which includes both B and T cell allorecognition, is still warranted. Recent studies have proposed using mismatched HLA epitopes (antibody and T cell) as a prognostic biomarker for humoral alloimmunity. However, the identification of immunogenic HLA mismatches has not progressed despite significant improvements in the identification of permissible mismatches. Certainly, the prediction of dnDSA development may benefit permissible HLA mismatched organ transplantations, personalized immunosuppression, and clinical trial design. However, characteristics that go beyond the listing of mismatched HLA antibody epitopes and T cell epitopes, such as the generation of HLA T cell epitope repertoires, recipient's HLA class II phenotype, and immunosuppressive regiments, are required for the precise assessment of allo-HLA immunogenicity.

Bibliometric analysis of T-cells immunity in pulmonary hypertension from 1992 to 2022

BACKGROUND

Adaptive immunity is an important disease mediator of pulmonary vascular remodeling during pulmonary hypertension (PH) development, especially T-cells lymphocytes. However, data for bibliometric analysis of T cell immunity in PH is currently vacant. This aimed to provide a comprehensive and visualized view of T-cells research in PH pathogenesis and to lay a solid foundation for further studies.

METHODS

The data was acquired from the Web of Science Core Collection database. Web of Science analytic tool was used to analysis the publication years, authors, journals, countries, and organizations. CiteSpace 6.2.R3, VOSviewer 1.6.16, and Scimago Graphica 1.0.35.0 were applied to conduct a visualization bibliometric analysis about authors, countries, institutions, journals, references, and keywords.

RESULTS

Nine hundred and eight publications from 1992 to 2022 were included in the analysis. The results showed that Humbert Marc was the most prolific author. American Journal of Physiology Lung Cellular and Molecular Physiology had the most related articles. The institution with the most articles was Udice French Research University. The United States was far ahead in the article output. Keywords analysis showed that "Pulmonary hypertension" was the most usually appeared keyword in the relevant literature, and included "T-cells", "Regulatory T cells", and "Activated T cell." "miRNA" of reference co-citation clustering analysis demonstrated the possible T-cell immunity activation mechanisms in PH. The most cited literature was published in the European Heart Journal by Galie N in 2016. The strongest citation burst of keyword is "gene expression" and terms such as "vascular remodeling," "growth," "proliferation," and "fibrosis" are among the list, indicating that T-cells interact with stromal vascular cells to induce pulmonary vascular remodeling. The strongest burst of cited reference is "Galie N, 2016."

CONCLUSIONS

T-cell immunity is an important pathogenesis mechanism for PH development, which may have interaction with miRNAs and stromal vascular cells, but the possible T-cell immunity activation mechanisms in PH need to be investigated further.

The tumor immune microenvironment and T-cell-related immunotherapies in colorectal cancer

The tumor microenvironment includes a complex network of immune T-cell subsets that play important roles in colorectal cancer (CRC) progression and are key elements of CRC immunotherapy. T cells develop and migrate within tumors, recognizing tumor-specific antigens to regulate immune surveillance. Current immunotherapies are divided into the following main categories based on the regulatory role of T-cell subsets in the tumor immune microenvironment (TIME): cytokines, monoclonal antibodies, peptide vaccines, CAR-T cells and more. This review describes the composition of the tumor immune microenvironment in colorectal cancer and the involvement of T cells in the pathogenesis and progression of CRC as well as current T-cell-related immunotherapies. Further studies on CRC-specific tumor antigens, the gene regulation of T cells, and the regulation of immune activity are needed.

Single-cell transcriptomics reveals antigen-presenting capacity and therapeutic resistance potential of immunomodulatory endothelial cells in colorectal cancer

BACKGROUND

The heterogeneity of tumor endothelial cells (TECs) hinders the efficacy of antiangiogenic therapies (AATs). Only a small percentage of angiogenic TECs are considered effective targets for AATs. Immunomodulatory ECs (IMECs), as a newly focused functional subgroup of endothelial cells (ECs), are being evaluated for their ability to regulate tumor immune balance and influence existing AATs.

METHODS

Based on single-cell transcriptome data from colorectal cancer in a publicly available database, we conducted a wide array of bioinformatic approaches to study EC subsets that meet the IMECs definition. Our investigation encompassed the gene expression signatures of these subsets, cellular composition differences, cell-cell interactions.

RESULTS

Two subsets that meet the IMECs definition were found in tumors and para-cancerous tissues. Combined with the results of gene ontological analysis and interaction with CD4+ T cells, we found that IMECs can present MHC-II antigens to mature CD4+ T cells. There were differences in the level of interaction between IMECs and different types of mature CD4+ T cell subsets. In addition, IMEC subsets had different expression levels of angiogenesis related genes. The angiogenesis score of IMECs decreased after patients received immunotherapy. IMEC subsets do not depend on a single proangiogenic receptor and are involved in regulating angiogenesis, which may reduce the efficacy of AATs. The adverse effects of specific IMEC subsets on AATs were validated in the RNA-seq dataset of the bevacizumab treatment group.

CONCLUSION

Our study suggests the potential MHC-II antigen presentation capacity of IMECs and the enhanced angiogenesis characteristics within tumors. The function of IMECs in the vascular network may have a potentially adverse effect on AATs. Controlling the functional properties of IMECs may be a new angle for tumor therapy.

Angiopoietin-2 blockade suppresses growth of liver metastases from pancreatic neuroendocrine tumors by promoting T cell recruitment

Improving the management of metastasis in pancreatic neuroendocrine tumors (PanNETs) is critical, as nearly half of patients with PanNETs present with liver metastases, and this accounts for the majority of patient mortality. We identified angiopoietin-2 (ANGPT2) as one of the most upregulated angiogenic factors in RNA-Seq data from human PanNET liver metastases and found that higher ANGPT2 expression correlated with poor survival rates. Immunohistochemical staining revealed that ANGPT2 was localized to the endothelial cells of blood vessels in PanNET liver metastases. We observed an association between the upregulation of endothelial ANGPT2 and liver metastatic progression in both patients and transgenic mouse models of PanNETs. In human and mouse PanNET liver metastases, ANGPT2 upregulation coincided with poor T cell infiltration, indicative of an immunosuppressive tumor microenvironment. Notably, both pharmacologic inhibition and genetic deletion of ANGPT2 in PanNET mouse models slowed the growth of PanNET liver metastases. Furthermore, pharmacologic inhibition of ANGPT2 promoted T cell infiltration and activation in liver metastases, improving the survival of mice with metastatic PanNETs. These changes were accompanied by reduced plasma leakage and improved vascular integrity in metastases. Together, these findings suggest that ANGPT2 blockade may be an effective strategy for promoting T cell infiltration and immunostimulatory reprogramming to reduce the growth of liver metastases in PanNETs.

Modulation of T cell function and survival by the tumor microenvironment

Cancer immunotherapy is shifting paradigms in cancer care. T cells are an indispensable component of an effective antitumor immunity and durable clinical responses. However, the complexity of the tumor microenvironment (TME), which consists of a wide range of cells that exert positive and negative effects on T cell function and survival, makes achieving robust and durable T cell responses difficult. Additionally, tumor biology, structural and architectural features, intratumoral nutrients and soluble factors, and metabolism impact the quality of the T cell response. We discuss the factors and interactions that modulate T cell function and survive in the TME that affect the overall quality of the antitumor immune response.

Inflammation in kidney repair: Mechanism and therapeutic potential

The kidney has a remarkable ability of repair after acute kidney injury (AKI). However, when injury is severe or persistent, the repair is incomplete or maladaptive and may lead to chronic kidney disease (CKD). Maladaptive kidney repair involves multiple cell types and multifactorial processes, of which inflammation is a key component. In the process of inflammation, there is a bidirectional interplay between kidney parenchymal cells and the immune system. The extensive and complex crosstalk between renal tubular epithelial cells and interstitial cells, including immune cells, fibroblasts, and endothelial cells, governs the repair and recovery of the injured kidney. Further research in this field is imperative for the discovery of biomarkers and promising therapeutic targets for kidney repair. In this review, we summarize the latest progress in the immune response and inflammation during maladaptive kidney repair, analyzing the interaction between immune cells and intrinsic kidney cells, pointing out the potentialities of inflammation-related pathways as therapeutic targets, and discussing the challenges and future research prospects in this field.

Inducing vascular normalization: A promising strategy for immunotherapy

In solid tumors, the vasculature is highly abnormal in structure and function, resulting in the formation of an immunosuppressive tumor microenvironment by limiting immune cells infiltration into tumors. Vascular normalization is receiving much attention as an alternative strategy to anti-angiogenic therapy, and its potential therapeutic targets include signaling pathways, angiogenesis-related genes, and metabolic pathways. Endothelial cells play an important role in the formation of blood vessel structure and function, and their metabolic processes drive blood vessel sprouting in parallel with the control of genetic signals in cancer. The feedback loop between vascular normalization and immunotherapy has been discussed extensively in many reviews. In this review, we summarize the impact of aberrant tumor vascular structure and function on drug delivery, metastasis, and anti-tumor immune responses. In addition, we present evidences for the mutual regulation of immune vasculature. Based on the importance of endothelial metabolism in controlling angiogenesis, we elucidate the crosstalk between endothelial cells and immune cells from the perspective of metabolic pathways and propose that targeting abnormal endothelial metabolism to achieve vascular normalization can be an alternative strategy for cancer treatment, which provides a new theoretical basis for future research on the combination of vascular normalization and immunotherapy.

Differential Contribution of NF-κB Signaling Pathways to CD4+ Memory T Cell Induced Activation of Endothelial Cells

Endothelial cells (ECs) are important contributors to inflammation in immune-mediated inflammatory diseases (IMIDs). In this study, we examined whether CD4⁺ memory T (T_m) cells can drive EC inflammatory responses. Human T_m cells produced ligands that induced inflammatory responses in human umbilical vein EC as exemplified by increased expression of inflammatory mediators including chemokines and adhesion molecules. NF-κB, a key regulator of EC activation, was induced by T_m cell ligands. We dissected the relative contribution of canonical and non-canonical NF-κB signaling to T_m induced EC responses using pharmacological small molecule inhibitors of IKKβ (iIKKβ) or NF-κB inducing kinase (iNIK). RNA sequencing revealed substantial overlap in IKKβ and NIK regulated genes (n=549) that were involved in inflammatory and immune responses, including cytokines (IL-1β, IL-6, GM-CSF) and chemokines (CXCL5, CXCL1). NIK regulated genes were more restricted, as 332 genes were uniquely affected by iNIK versus 749 genes by iIKKβ, the latter including genes involved in metabolism, proliferation and leukocyte adhesion (VCAM-1, ICAM-1). The functional importance of NIK and IKKβ in EC activation was confirmed by transendothelial migration assays with neutrophils, demonstrating stronger inhibitory effects of iIKKβ compared to iNIK. Importantly, iIKKβ – and to some extent iNIK - potentiated the effects of currently employed therapies for IMIDs, like JAK inhibitors and anti-IL-17 antibodies, on EC inflammatory responses. These data demonstrate that inhibition of NF-κB signaling results in modulation of T_m cell-induced EC responses and highlight the potential of small molecule NF-κB inhibitors as a novel treatment strategy to target EC inflammatory responses in IMIDs.

Regulation of T Cells in Cancer by Nitric Oxide

The T cell-mediated immune response is primarily involved in the fight against infectious diseases and cancer and its underlying mechanisms are complex. The anti-tumor T cell response is regulated by various T cell subsets and other cells and tissues in the tumor microenvironment (TME). Various mechanisms are involved in the regulation of these various effector cells. One mechanism is the iNOS/.NO that has been reported to be intimately involved in the regulation and differentiation of the various cells that regulate the anti-tumor CD8 T cells. Both endogenous and exogenous .NO are implicated in this regulation. Importantly, the exposure of T cells to .NO had different effects on the immune response, depending on the .NO concentration and time of exposure. For instance, iNOS in T cells regulates activation-induced cell death and inhibits Treg induction. Effector CD8 T cells exposed to .NO result in the upregulation of death receptors and enhance their anti-tumor cytotoxic activity. .NO-Tregs suppress CD4 Th17 cells and their differentiation. Myeloid-derived suppressor cells (MDSCs) expressing iNOS inhibit T cell functions via .NO and inhibit anti-tumor CD8 T cells. Therefore, both .NO donors and .NO inhibitors are potential therapeutics tailored to specific target cells that regulate the T cell effector anti-tumor response.

Secretome and Tunneling Nanotubes: A Multilevel Network for Long Range Intercellular Communication between Endothelial Cells and Distant Cells

As a cellular interface between the blood and tissues, the endothelial cell (EC) monolayer is involved in the control of key functions including vascular tone, permeability and homeostasis, leucocyte trafficking and hemostasis. EC regulatory functions require long-distance communications between ECs, circulating hematopoietic cells and other vascular cells for efficient adjusting thrombosis, angiogenesis, inflammation, infection and immunity. This intercellular crosstalk operates through the extracellular space and is orchestrated in part by the secretory pathway and the exocytosis of Weibel Palade Bodies (WPBs), secretory granules and extracellular vesicles (EVs). WPBs and secretory granules allow both immediate release and regulated exocytosis of messengers such as cytokines, chemokines, extracellular membrane proteins, coagulation or growth factors. The ectodomain shedding of transmembrane protein further provide the release of both receptor and ligands with key regulatory activities on target cells. Thin tubular membranous channels termed tunneling nanotubes (TNTs) may also connect EC with distant cells. EVs, in particular exosomes, and TNTs may contain and transfer different biomolecules (e.g., signaling mediators, proteins, lipids, and microRNAs) or pathogens and have emerged as a major triggers of horizontal intercellular transfer of information.

Deficiency in CD4 T Cells Leads to Enhanced Postpartum Internal Carotid Artery Vasoconstriction in Mice: The Role of Nitric Oxide

The risk of postpartum (PP) stroke is increased in complicated pregnancies. Deficiency in CD4 T cell subsets is associated with preeclampsia and may contribute to PP vascular disease, including internal carotid artery (ICA) stenosis and stroke. We hypothesized that CD4 T cell deficiency in pregnancy would result in ICA dysregulation, including enhanced ICA vasoconstriction. We characterized the function, mechanical behavior, and structure of ICAs from C57BL/6 (WT) and CD4 deficient (CD4KO) mice, and assessed the role of NO in the control of ICA function at pre-conception and PP. WT and CD4KO mice were housed under pathogen-free conditions, mated to same-strain males, and allowed to litter or left virgin. At 3 days or 4 weeks PP, mice were euthanized. The responses to phenylephrine (PE), high K⁺ and acetylcholine (ACh) were assessed in pressurized ICAs before and after NOS inhibition. Passive lumen diameters were measured at 3–140 mmHg. eNOS and iNOS expression as well as the presence of T cells were evaluated by immunohistochemistry. Constriction of WT ICAs to PE was not modified PP. In contrast, responses to PE were significantly increased in ICAs from PP as compared to virgin CD4KO mice. Constriction to high K⁺ was not enhanced PP. ICAs from WT and CD4KO mice were equally sensitive to ACh with a significant rightward shift of dose-response curves after L-NNA treatment. NOS inhibition enhanced PE constriction of ICAs from WT virgin and PP mice. Although a similar effect was detected in ICAs of virgin CD4KO mice, no such changes were observed in vessels from PP CD4KO mice. Passive arterial distensibility at physiological levels of pressure was not modified at PP. ICA diameters were significantly increased in PP with no change in vascular wall thickness. Comparison of eNOS expression in virgin, 3 days and 4 weeks PP revealed a reduced expression in ICA from CD4 KO vs. WT PP vessels which reached significance at 4 weeks PP. iNos expression was similar and decreased over the PP period in vessels from WT and CD4KO mice. Dysregulation of the CD4 T cell population in pregnancy may make ICA vulnerable to vasospasm due to decreased NO-dependent control of ICA constriction. This may lead to cerebral hypoperfusion and increase the risk of maternal PP stroke.

Mechanistic Target of Rapamycin Inhibitors in Renal Cell Carcinoma: Potential, Limitations, and Perspectives

Several elements highlight the importance of the mechanistic target of rapamycin (mTOR) in the biology of renal cell carcinoma (RCC). mTOR signaling pathway is indeed frequently activated in RCC, inducing cancer cell proliferation and survival. In addition, mTOR promotes tumor angiogenesis and regulates the expression of hypoxia-inducible factors that play an important role in a subset of RCC. Despite mTOR protumorigenic effects, mTOR inhibitors have failed to provide long-lasting anticancer benefits in RCC patients, highlighting the need to readdress their role in the treatment of RCC. This review aims to present the rationale and limitations of targeting mTOR in RCC. Future roles of mTOR inhibitors in the treatment of RCC are also discussed, in particular in the context of immunotherapies.

Advanced in vitro Research Models to Study the Role of Endothelial Cells in Solid Organ Transplantation

The endothelium plays a key role in acute and chronic rejection of solid organ transplants. During both processes the endothelium is damaged often with major consequences for organ function. Also, endothelial cells (EC) have antigen-presenting properties and can in this manner initiate and enhance alloreactive immune responses. For decades, knowledge about these roles of EC have been obtained by studying both in vitro and in vivo models. These experimental models poorly imitate the immune response in patients and might explain why the discovery and development of agents that control EC responses is hampered. In recent years, various innovative human 3D in vitro models mimicking in vivo organ structure and function have been developed. These models will extend the knowledge about the diverse roles of EC in allograft rejection and will hopefully lead to discoveries of new targets that are involved in the interactions between the donor organ EC and the recipient's immune system. Moreover, these models can be used to gain a better insight in the mode of action of the currently prescribed immunosuppression and will enhance the development of novel therapeutics aiming to reduce allograft rejection and prolong graft survival.

Pulmonary endothelium-derived PD-L1 induced by the H9N2 avian influenza virus inhibits the immune response of T cells

BACKGROUND

The PD-1/PD-L1 pathway is an inhibitory signaling pathway that maintains the balance between the immune response and immunotolerance, and its overactivation in cancer and viral infections inhibits T cell function. The target cells of various viruses, microvascular endothelial cells (MECs) have been shown to be key regulatory points in immune regulation and virion diffusion in vivo during infection with multiple influenza virus subtypes. Furthermore, avian influenza virus (AIV) infection can induce immunosuppression by causing imbalances in immune responses and immune organ damage. Thus, the aim of this study was to investigate whether the H9N2 virus inhibited the immune function of T cells that migrated across MECs by upregulating PD-L1 expression on MECs.

METHODS

The susceptibility of rat pulmonary microvascular endothelial cells (RPMECs) to the H9N2 virus was evaluated by a plaque-forming assay and immunofluorescence staining. Then, we quantified the mRNA and protein levels of PD-L1 in RPMECs induced by H9N2 virus infection using quantitative real-time PCR and flow cytometry. The interaction between the activated T cells and RPMECs infected with the H9N2 virus was revealed using a coculture system. The effect of endothelial-derived PD-L1 on T cell function was investigated by using ELISA and flow cytometry with or without a PD-L1-specific antibody.

RESULTS

Surface staining and the plaque-forming assay showed that the H9N2 virus infected and replicated in RPMECs. Both the PD-L1 mRNA level and PD-L1 protein level were upregulated in RPMECs infected with the H9N2 virus. H9N2 virus-induced PD-L1 expression significantly reduced the secretions of IL-2, IFN-γ and granzyme B and perforin expression in T cells. The above data were significantly increased after treatment with an anti-PD-L1 antibody, confirming the above mentioned findings. In addition, the induction of PD-L1 expression decreased the proliferative capacity of the cocultured T cells but did not affect the apoptosis rate of T cells.

CONCLUSIONS

Taken together, the results suggest that the H9N2 virus is able to inhibit the T cell immune response by upregulating PD-L1 expression in pulmonary microvascular endothelial cells.

Unexpected enhancement of FVIII immunogenicity by endothelial expression in lentivirus-transduced and transgenic mice

Factor VIII (FVIII) replacement therapy for hemophilia A is complicated by development of inhibitory antibodies (inhibitors) in ∼30% of patients. Because endothelial cells (ECs) are the primary physiologic expression site, we probed the therapeutic potential of genetically restoring FVIII expression selectively in ECs in hemophilia A mice (FVIIInull). Expression of FVIII was driven by the Tie2 promoter in the context of lentivirus (LV)-mediated in situ transduction (T2F8LV) or embryonic stem cell-mediated transgenesis (T2F8Tg). Both endothelial expression approaches were associated with a strikingly robust immune response. Following in situ T2F8LV-mediated EC transduction, all FVIIInull mice developed inhibitors but had no detectable plasma FVIII. In the transgenic approach, the T2F8Tg mice had normalized plasma FVIII levels, but showed strong sensitivity to developing an FVIII immune response upon FVIII immunization. A single injection of FVIII with incomplete Freund adjuvant led to high titers of inhibitors and reduction of plasma FVIII to undetectable levels. Because ECs are putative major histocompatibility complex class II (MHCII)-expressing nonhematopoietic, "semiprofessional" antigen-presenting cells (APCs), we asked whether they might directly influence the FVIII immune responses. Imaging and flow cytometric studies confirmed that both murine and human ECs express MHCII and efficiently bind and take up FVIII protein in vitro. Moreover, microvascular ECs preconditioned ex vivo with inflammatory cytokines could functionally present exogenously taken-up FVIII to previously primed CD4+/CXCR5+ T follicular helper (Tfh) cells to drive FVIII-specific proliferation. Our results show an unanticipated immunogenicity of EC-expressed FVIII and suggest a context-dependent role for ECs in the regulation of inhibitors as auxiliary APCs for Tfh cells.

Circulating mitochondria in organ donors promote allograft rejection

The innate immune system is a critical regulator of the adaptive immune responses that lead to allograft rejection. It is increasingly recognized that endogenous molecules released from tissue injury and cell death are potent activators of innate immunity. Mitochondria, ancestrally related to bacteria, possess an array of endogenous innate immune-activating molecules. We have recently demonstrated that extracellular mitochondria are abundant in the circulation of deceased organ donors and that their presence correlates with early allograft dysfunction. Here we demonstrate the ability of mitochondria to activate endothelial cells (ECs), the initial barrier between a solid organ allograft and its host. We find that mitochondria exposure leads to the upregulation of EC adhesion molecules and their production of inflammatory cytokines and chemokines. Additionally, mitochondrial exposure causes dendritic cells to upregulate costimulatory molecules. Infusion of isolated mitochondria into heart donors leads to significant increase in allograft rejection in a murine heterotopic heart transplantation model. Finally, co-incubation of human peripheral blood mononuclear cells with mitochondria-treated ECs results in increased numbers of effector (IFN-γ⁺ , TNF-α⁺ ) CD8⁺ T cells. These data indicate that circulating extracellular mitochondria in deceased organ donors may directly activate allograft ECs and promote graft rejection in transplant recipients.

Inflammation research sails through the sea of immunology to reach immunometabolism

Inflammation occurs as a result of acute trauma, invasion of the host by different pathogens, pathogen-associated molecular patterns (PAMPs) or chronic cellular stress generating damage-associated molecular patterns (DAMPs). Thus inflammation may occur under both sterile inflammatory conditions including certain cancers, autoimmune or autoinflammatory diseases (Rheumatic arthritis (RA)) and infectious diseases including sepsis, pneumonia-associated acute lung inflammation (ALI) or acute respiratory distress syndrome (ARDS). The pathogenesis of inflammation involves dysregulation of an otherwise protective immune response comprising of various innate and adaptive immune cells and humoral (cytokines and chemokines) mediators secreted by these immune cells upon the activation of signaling mechanisms regulated by the activation of different pattern recognition receptors (PRRs). However, the pro-inflammatory and anti-inflammatory action of these immune cells is determined by the metabolic stage of the immune cells. The metabolic process of immune cells is called immunometabolism and its shift determined by inflammatory stimuli is called immunometabolic reprogramming. The article focuses on the involvement of various immune cells generating the inflammation, their interaction, immunometabolic reprogramming, and the therapeutic targeting of the immunometabolism to manage inflammation.

Reduced mRNA and Protein Expression Levels of Tet Methylcytosine Dioxygenase 3 in Endothelial Progenitor Cells of Patients of Type 2 Diabetes With Peripheral Artery Disease

Endothelial progenitor cells (EPCs) with immunological properties repair microvasculature to prevent the complications in patients with diabetes. Epigenetic changes such as DNA methylation alter the functions of cells. Tet methylcytosine dioxygenases (TETs) are enzymes responsible for the demethylation of cytosine on genomic DNA in cells. We hypothesized that EPCs of diabetic patients with peripheral artery disease (D-PAD) might have altered expression levels of TETs. Subjects who were non-diabetic (ND, n = 22), with diabetes only (D, n = 29) and with D-PAD (n = 22) were recruited for the collection of EPCs, which were isolated and subjected to analysis. The mRNA and protein expression levels of TET1, TET2, and TET3 were determined using real-time PCR and immunoblot, respectively. The TET1 mRNA expression level in ND group was lower than that in the D and D-PAD groups. The TET3 mRNA level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group. The TET1 protein level in the D-PAD group, but not the D group, was higher than that in the ND group. The TET2 protein level in the D-PAD group, but not the D group, was lower than that in the ND group. The TET3 protein level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group, which is the lowest among the three groups. The changes of TETs protein levels were due to the alterations of their transcripts. These probably lead to epigenetic changes, which may be responsible for the reductions of EPCs numbers and functions in patients with the D-PAD. The expression pattern of TET3 mRNA and TET3 protein in EPCs may be a biomarker of angiopathy in diabetic patients.

Association between angiogenesis and cytotoxic signatures in the tumor microenvironment of gastric cancer

Background

A suppressive immune microenvironment and pathological angiogenesis are hallmarks of gastric cancer. Theoretically, immune checkpoint inhibitors (ICIs) stimulate pre-primed neoantigen-specific T cells, and antiangiogenic agents then facilitate their infiltration into the tumor niche by promoting vascular normalization. Currently, the interconnections of these two phenotypes and their relevance to the tumor microenvironment (TME) have not been fully characterized in gastric cancer.

Materials and methods

Transcriptome profiling data retrieved from The Cancer Genome Atlas (TCGA) database were used to deconvolute the feature of TME for gastric cancer (N = 375). Machine learning, correlation, and prognosis analysis were applied to elucidate the correlations between angiogenesis, cytotoxic T lymphocyte infiltration, and patient survival.

Results

Substantial heterogeneous infiltration of immune cell populations among cases was observed. Furthermore, among targetable pathways, angiogenesis was identified as the dominant factor in discriminating different infiltration statuses. Most importantly, the angiogenesis pathway was negatively correlated with the amount of activated CD8⁺ T cells only for patients with a higher infiltration, and the concomitance of low angiogenesis signaling and highly activated CD8⁺ T-cell infiltration was associated with a significant survival benefit.

Conclusion

Our findings demonstrated a negative correlation between angiogenesis signaling and cytotoxic function in gastric cancer patients with a highly infiltrated immune niche. These data provided a rationale for potential combination strategy and further clinical investigations of ICIs plus antiangiogenesis agents for patients with gastric cancer with an inflamed TME.

Evolving Significance and Future Relevance of Anti-Angiogenic Activity of mTOR Inhibitors in Cancer Therapy

mTOR inhibitors have demonstrated remarkable anti-tumor activity in experimental models, mainly by reducing cancer cell growth and tumor angiogenesis. Their use in cancer patients as monotherapy has, however, generated only limited benefits, increasing median overall survival by only a few months. Likewise, in other targeted therapies, cancer cells develop resistance mechanisms to overcome mTOR inhibition. Hence, novel therapeutic strategies have to be designed to increase the efficacy of mTOR inhibitors in cancer. In this review, we discuss the present and future relevance of mTOR inhibitors in cancer therapy by focusing on their effects on tumor angiogenesis.

Angiogenesis on coronary angiography is a marker for accelerated cardiac allograft vasculopathy as assessed by intravascular ultrasound

BACKGROUND

Errant neovascularization and coronary artery fistulae (CAF) are frequently observed after cardiac transplantation. The relationship between angiographic neovascularization/CAF and coronary plaque progression is unknown.

METHODS

Angiography and intravascular ultrasound were routinely performed at 4-6 weeks and 1-year post-transplant. Pts were divided into three groups: no angiographic angiogenesis (Group 1), neovascularization only (Group 2), and CAF (Group 3). First-year changes in maximal intimal thickness (MIT), maximal intimal area (MIA), and percent atheroma volume (PAV) were compared between groups.

RESULTS

The 106 pts were included, 40/106 in Group 1, 42/106 in Group 2, and 24/106 in Group 3. Respectively, first-year ΔMIT was 0.14 ± 0.13 mm, 0.32 ± 0.26 mm, and 0.50 ± 0.34 mm, P < .001. ΔMIA was 0.6 ± 0.6 mm² , 1.7 ± 1.8 mm² , and 3.0 ± 2.6 mm² , P < .001. ΔPAV was 2.3 ± 2.5%, 6.0 ± 5.1%, and 9.6 ± 9.0%, P < .001. Rapid plaque progression occurred in 1/40 (2.5%) pts in Group 1, 12/42 (28.6%) in Group 2, and 12/24 (50%) in Group 3, P < .001. Multivariate analysis identified both antithymocyte globulin and presence of CAF as independently associated with rapid plaque progression: OR 0.29 (P = .038) and 4.04 (P = .014).

CONCLUSION

Neovascularization and CAF are commonly present on surveillance angiography after cardiac transplantation and may signify amplified angiogenesis. Their presence is associated with accelerated coronary plaque progression by IVUS.

Fine-Tuning Tumor Endothelial Cells to Selectively Kill Cancer

Tumor endothelial cells regulate several aspects of tumor biology, from delivering oxygen and nutrients to shaping the immune response against a tumor and providing a barrier against tumor cell dissemination. Accordingly, targeting tumor endothelial cells represents an important modality in cancer therapy. Whereas initial anti-angiogenic treatments focused mainly on blocking the formation of new blood vessels in cancer, emerging strategies are specifically influencing certain aspects of tumor endothelial cells. For instance, efforts are generated to normalize tumor blood vessels in order to improve tumor perfusion and ameliorate the outcome of chemo-, radio-, and immunotherapy. In addition, treatment options that enhance the properties of tumor blood vessels that support a host’s anti-tumor immune response are being explored. Hence, upcoming anti-angiogenic strategies will shape some specific aspects of the tumor blood vessels that are no longer limited to abrogating angiogenesis. In this review, we enumerate approaches that target tumor endothelial cells to provide anti-cancer benefits and discuss their therapeutic potential.

Dual angiopoietin-2 and VEGFA inhibition elicits antitumor immunity that is enhanced by PD-1 checkpoint blockade

Pathological angiogenesis is a hallmark of cancer and a therapeutic target. Vascular endothelial growth factor A (VEGFA) and angiopoietin-2 (ANGPT2; also known as ANG2) are proangiogenic cytokines that sustain tumor angiogenesis and limit antitumor immunity. We show that combined ANGPT2 and VEGFA blockade by a bispecific antibody (A2V) provided superior therapeutic benefits, as compared to the single agents, in both genetically engineered and transplant tumor models, including metastatic breast cancer (MMTV-PyMT), pancreatic neuroendocrine tumor (RIP1-Tag2), and melanoma. Mechanistically, A2V promoted vascular regression, tumor necrosis, and antigen presentation by intratumoral phagocytes. A2V also normalized the remaining blood vessels and facilitated the extravasation and perivascular accumulation of activated, interferon-γ (IFNγ)-expressing CD8⁺ cytotoxic T lymphocytes (CTLs). Whereas the antitumoral activity of A2V was, at least partly, CTL-dependent, perivascular T cells concurrently up-regulated the expression of the immune checkpoint ligand programmed cell death ligand 1 (PD-L1) in tumor endothelial cells. IFNγ neutralization blunted this adaptive response, and PD-1 blockade improved tumor control by A2V in different cancer models. These findings position immune cells as key effectors of antiangiogenic therapy and support the rationale for cotargeting angiogenesis and immune checkpoints in cancer therapy.

Endothelial damage is aggravated in acute GvHD and could predict its development

The aim of the present study was to explore whether there is enhanced endothelial dysfunction in patients developing acute GvHD (aGvHD) after allogeneic hematopoietic cell transplantation (allo-HCT) and to identify biomarkers with predictive and/or diagnostic value. In in vitro experiments, endothelial cells (ECs) were exposed to serum from patients with (aGvHD, n=31) and without (NoGvHD, n=13) aGvHD, to evaluate changes in surface adhesion receptors, the reactivity of the extracellular matrix by measuring the presence of Von Willebrand factor (VWF) and platelet adhesion, and the activation of intracellular signaling proteins. Plasma levels of VWF, ADAMTS-13, TNF receptor 1 (TNFR1), soluble vascular cell adhesion molecule 1 and soluble intercellular adhesion molecule 1 were also measured. In vitro results showed a more marked proinflammatory and prothrombotic phenotype in ECs in association with aGvHD. Regarding circulating biomarkers, levels of VWF and TNFR1 above an optimal cutoff score, taken independently or combined, at day 7 after allo-HCT, would be able to positively predict that around 90% of patients will develop aGvHD. Our results demonstrate that endothelial damage is aggravated in those allo-HCT recipients developing aGvHD, and that VWF and TNFR1 are promising predictive aGvHD biomarkers. These findings could contribute to improve the understanding of the pathophysiology of aGvHD.

Inflammasomes and IL-1 biology in the pathogenesis of allograft dysfunction

Inflammasomes are high-molecular-weight cytosolic complexes that mediate the activation of caspases. There are many inflammasomes, and each is influenced by a unique pattern-recognition receptor response. Two signals are typically involved in the inflammasome pathways. Signal one involves recognition of pathogen-associated molecular patterns (PAMPs), such as LPS or other colonizing/invading microbes, that interact with TLRs, which induce the downstream production of pro-IL-1β. This is followed by signal two, which involves recognition of PAMPs or damage-associated molecular patterns (DAMPs), such as uric acid or ATP, via NLRP3, which leads to caspase-1-dependent cleavage of pro-IL-1β to active IL-1β and pyroptosis. Ultimately, these two signals cause the release of multiple proinflammatory cytokines. Both PAMPs and DAMPs can be liberated by early insults to the allograft, including ischemia/reperfusion injury, infections, and rejection. The consequence of inflammasome activation and IL-1 expression is the upregulation of adhesion molecules and chemokines, which leads to allograft neutrophil sequestration, mononuclear phagocyte recruitment, and T cell activation, all of which are key steps in the continuum from allograft insult to chronic allograft dysfunction.

The Role of the Tumor Vasculature in the Host Immune Response: Implications for Therapeutic Strategies Targeting the Tumor Microenvironment

Recently developed cancer immunotherapy approaches including immune checkpoint inhibitors and chimeric antigen receptor T cell transfer are showing promising results both in trials and in clinical practice. These approaches reflect increasing recognition of the crucial role of the tumor microenvironment in cancer development and progression. Cancer cells do not act alone, but develop a complex relationship with the environment in which they reside. The host immune response to tumors is critical to the success of immunotherapy; however, the determinants of this response are incompletely understood. The immune cell infiltrate in tumors varies widely in density, composition, and clinical significance. The tumor vasculature is a key component of the microenvironment that can influence tumor behavior and treatment response and can be targeted through the use of antiangiogenic drugs. Blood vascular and lymphatic endothelial cells have important roles in the trafficking of immune cells, controlling the microenvironment, and modulating the immune response. Improving access to the tumor through vascular alteration with antiangiogenic drugs may prove an effective combinatorial strategy with immunotherapy approaches and might be applicable to many tumor types. In this review, we briefly discuss the host's immune response to cancer and the treatment strategies utilizing this response, before focusing on the pathological features of tumor blood and lymphatic vessels and the contribution these might make to tumor immune evasion.

An In Vitro Model of the Blood-brain Barrier Using Impedance Spectroscopy: A Focus on T Cell-endothelial Cell Interaction

Breakdown of the blood-brain barrier (BBB) is a critical step in the development of autoimmune diseases such as multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). This process is characterized by the transmigration of activated T cells across brain endothelial cells (ECs), the main constituents of the BBB. However, the consequences on brain EC function upon interaction with such T cells are largely unknown. Here we describe an assay that allows for the evaluation of primary mouse brain microvascular EC (MBMEC) function and barrier integrity during the interaction with T cells over time. The assay makes use of impedance cell spectroscopy, a powerful tool for studying EC monolayer integrity and permeability, by measuring changes in transendothelial electrical resistance (TEER) and cell layer capacitance (Ccl). In direct contact with ECs, stimulated but not naïve T cells are capable of inducing EC monolayer dysfunction, as visualized by a decrease in TEER and an increase in Ccl. The assay records changes in EC monolayer integrity in a continuous and automated fashion. It is sensitive enough to distinguish between different strengths of stimuli and levels of T cell activation and it enables the investigation of the consequences of a targeted modulation of T cell-EC interaction using a wide range of substances such as antibodies, pharmacological reagents and cytokines. The technique can also be used as a quality control for EC integrity in in vitro T-cell transmigration assays. These applications make it a versatile tool for studying BBB properties under physiological and pathophysiological conditions.

Prenylated Polyphenols from Clusiaceae and Calophyllaceae with Immunomodulatory Activity on Endothelial Cells

Endothelial cells (ECs) are key players in inflammation and immune responses involved in numerous pathologies. Although attempts were experimentally undertaken to prevent and control EC activation, drug leads and probes still remain necessary. Natural products (NPs) from Clusiaceous and Calophyllaceous plants were previously reported as potential candidates to prevent endothelial dysfunction. The present study aimed to identify more precisely the molecular scaffolds that could limit EC activation. Here, 13 polyphenols belonging to 5 different chemical types of secondary metabolites (i.e., mammea coumarins, a biflavonoid, a pyranochromanone acid, a polyprenylated polycyclic acylphloroglucinol (PPAP) and two xanthones) were tested on resting and cytokine-activated EC cultures. Quantitative and qualitative changes in the expression of both adhesion molecules (VCAM-1, ICAM-1, E-selectin) and major histocompatibility complex (MHC) molecules have been used to measure their pharmaceutical potential. As a result, we identified 3 mammea coumarins that efficiently reduce (up to >90% at 10 μM) both basal and cytokine-regulated levels of MHC class I, class II, MICA and HLA-E on EC surface. They also prevented VCAM-1 induction upon inflammation. From a structural point of view, our results associate the loss of the free prenyl group substituting mammea coumarins with a reduced cellular cytotoxicity but also an abrogation of their anti-inflammatory potential and a reduction of their immunosuppressive effects. A PPAP, guttiferone J, also triggers a strong immunomodulation but restricted to HLA-E and MHC class II molecules. In conclusion, mammea coumarins with a free prenyl group and the PPAP guttiferone J emerge as NPs able to drastically decrease both VCAM-1 and a set of MHC molecules and to potentially reduce the immunogenicity of the endothelium.

Importance of the interaction between immune cells and tumor vasculature mediated by thalidomide in cancer treatment (Review)

Over the past 60 years, thalidomide has metamorphosized from a drug prescribed to treat morning sickness in pregnant women, which was subsequently found to induce birth defects, into a highly effective therapy for treating leprosy and multiple myeloma. Several mechanisms have been proposed to explain the anticancer effects of thalidomide, including antiangiogenic and immunomodulatory activities. At present, evidence suggests that thalidomide may induce vessel maturation. Vascular normalization may be an effective strategy to enhance cancer immunotherapy. Numerous studies have shown that the tumor infiltrating immune cell subsets are important in regulating the process of tumor angiogenesis. The mechanisms associated with antiangiogenesis and the potent immunomodulatory effects of thalidomide obtained the most support. The studies of the antiangiogenic activity of thalidomide were guided in a novel direction by a hypothesis regarding the vascular normalization of tumors. Hence, thalidomide is effective in cancer treatment due to the interaction between immune cells and tumor vasculature. This mechanism provides new avenues to explore for the treatment of cancer.

T-Lymphocyte Subset Absolute Counts in the Peripheral Blood of Mediterranean Spotted Fever Patients: Relations to Disease Severity

INTRODUCTION

Mediterranean spotted fever (MSF) in Bulgaria is caused by Rickettsia conorii conorii.

AIM

This study aims at investigating the absolute counts of T-lymphocyte subsets in the peripheral blood of patients with MSF in order to establish relationships with disease severity.

MATERIALS AND METHODS

The absolute counts of T-lymphocyte subsets were tested in the blood of 62 patients in the acute stage of MSF. They were assigned into three age and sex matched groups, based on the severity of disease - with mild, moderate or severe forms. Controls were 32 age and sex matched healthy individuals. The diagnosis was confirmed by an immunofluorescence assay. Immunophenotyping was performed using Epics XL-MCL Coulter, USA flow-cytometer.

RESULTS

The absolute counts of immune competent (CD3+) cells, as well as the counts of helper/inducer (CD3+ CD4+) and suppressor/ cytotoxic (CD3+ CD8+) T-cell subsets decreased in parallel with disease severity. Naïve (CD4+ CD45RA+) and activated memory (CD4+ CD45RO+) T-cell subsets were reduced, particularly in severe MSF. Taken as a whole, the counts of activated (CD3+ HLA-DR+) and that of presenting accessory (CD28+) or stimulatory (CD38+) molecules Т-cell subsets was increased, but in the first two subsets the trend from mild to severe forms of the disease was descending.

CONCLUSION

Reduced T-lymphocyte subset counts are likely related to trans-migration into perivascular inflammatory foci. The increased number of T-lymphocytes bearing activation molecules reflects a mobilization of the cell-mediated immune response. An important issue of this study is the possible prognostic value of T-cell subsets counting, predicting the evolution of a clinical condition to clinical forms, according to the disease severity.

Induction Therapy With Antithymocyte Globulin in Patients Undergoing Cardiac Transplantation Is Associated With Decreased Coronary Plaque Progression as Assessed by Intravascular Ultrasound

BACKGROUND

Antithymocyte globulin (ATG) is used as induction therapy after cardiac transplant for enhancing immunosuppression and delaying the initiation of nephrotoxic drugs. It is unknown if ATG induction is associated with decreased coronary plaque progression by intravascular ultrasound (IVUS).

METHODS AND RESULTS

Patients transplanted between March 2010 and December 2012 with baseline and 1-year IVUS were included. All patients transplanted were included in a secondary analysis. Change in plaque progression was measured in a blinded fashion on matched coronary segments and contrasted between patients induced with ATG and those who were not. One hundred and three patients were included in IVUS arms. Mean age at transplant was 55.8 ± 12.6 years, and 33.0% were female. Patients induced with ATG were more sensitized (54.3% versus 14.3%). Plaque progression was attenuated in patients who received ATG by changes in maximal intimal area (1.0 ± 1.2 versus 2.3 ± 2.6 mm(2); P = 0.001), maximal percent stenosis (6.3 ± 7.9 versus 12.8 ± 12.3%; = 0.003), maximal intimal thickness (0.2 ± 0.2 versus 0.3 ± 0.3 mm; P = 0.035), and plaque volume (0.5 ± 0.7 versus 1.0 ± 1.3 mm(3)/mm; P = 0.016). Rapid plaque progression by maximal percent stenosis (≥ 20%) occurred less frequently in the ATG arm (4.3% versus 26.3; P = 0.003). Survival (P = 0.242) and any treated rejection (P = 0.166) were not statistically different between groups. Patients receiving ATG had a higher rate of first-year infection (P = 0.003), perhaps related to increased intravenous antibiotic use immediately postoperatively, and a trend toward more biopsy-proven rejection (P = 0.073).

CONCLUSIONS

Induction therapy with ATG is associated with reduced first-year coronary plaque progression as assessed by IVUS, despite an increased prevalence of sensitized patients with a trend toward more rejection.

Elevated immune monitoring as measured by increased adenosine triphosphate production in activated lymphocytes is associated with accelerated development of cardiac allograft vasculopathy after cardiac transplantation

BACKGROUND

Elevated immune monitoring (IM), as measured by adenosine triphosphate (ATP) release from activated lymphocytes, has been suggested to represent an under-immunosuppressed state. Its association with the development of angiographic cardiac allograft vasculopathy (CAV) is unknown.

METHODS

Patients transplanted between January 2007 and December 2011 with annual angiograms and at least 1 IM assay were included in the analysis. Peak IM scores were determined for each patient. Patients with peak IM in the highest quartile (Group 2) were compared with those with scores in the lower quartiles (Group 1). Mild disease was scored as Grade 1 (CAV1) and moderate or severe disease was scored as Grades 2 or 3 (CAV2/3).

RESULTS

Two hundred forty patients were included. The mean age at transplant was 54.2 ± 12.1 years. Time to peak IM assay was 105.9 ± 44.1 days and average number of assays obtained per patient was 3.1 ± 1.8. Patients in the highest quartile (Group 2) had peak IM ≥446 ng ATP/ml. Mean clinical follow-up was 4.6 ± 1.7 years. CAV1 was observed in 86 of 180 (47.8%) patients in Group 1 and 39 of 60 (65.0%) in Group 2. Freedom from CAV1 was significantly lower in patients in Group 2 (log rank, p = 0.012). CAV2/3 occurred in 7 of 180 (3.7%) patients in Group 1 and 9 of 60 (15.0%) patients in Group 2. Freedom from CAV2/3 was significantly lower in patients in Group 2 (p = 0.003). In multivariate analysis elevated peak IM assay was still found to be associated with angiographic CAV (hazard ratio 1.647, confidence interval 1.020 to 2.661, p = 0.041).

CONCLUSION

Elevated peak IM, as measured by increased ATP production, in activated lymphocytes is associated with decreased freedom from angiographic CAV.

An Endothelial Planar Cell Model for Imaging Immunological Synapse Dynamics

Adaptive immunity is regulated by dynamic interactions between T cells and antigen presenting cells ('APCs') referred to as 'immunological synapses'. Within these intimate cell-cell interfaces discrete sub-cellular clusters of MHC/Ag-TCR, F-actin, adhesion and signaling molecules form and remodel rapidly. These dynamics are thought to be critical determinants of both the efficiency and quality of the immune responses that develop and therefore of protective versus pathologic immunity. Current understanding of immunological synapses with physiologic APCs is limited by the inadequacy of the obtainable imaging resolution. Though artificial substrate models (e.g., planar lipid bilayers) offer excellent resolution and have been extremely valuable tools, they are inherently non-physiologic and oversimplified. Vascular and lymphatic endothelial cells have emerged as an important peripheral tissue (or stromal) compartment of 'semi-professional APCs'. These APCs (which express most of the molecular machinery of professional APCs) have the unique feature of forming virtually planar cell surface and are readily transfectable (e.g., with fluorescent protein reporters). Herein a basic approach to implement endothelial cells as a novel and physiologic 'planar cellular APC model' for improved imaging and interrogation of fundamental antigenic signaling processes will be described.

The immunological effect of hyaluronan in tumor angiogenesis

The relationship between the immune system and angiogenesis has been described in several contexts, both in physiological and pathological conditions, as pregnancy and cancer. In fact, different types of immune cells, such as myeloid, macrophages and denditric cells, are able to modulate tumor neovascularization. On the other hand, tumor microenvironment also includes extracellular matrix components like hyaluronan, which has a deregulated synthesis in different tumors. Hyaluronan is a glycosaminoglycan, normally present in the extracellular matrix of tissues in continuous remodeling (embryogenesis or wound healing processes) and acts as an important modulator of cell behavior by different mechanisms, including angiogenesis. In this review, we discuss hyaluronan as a modulator of tumor angiogenesis, focusing in intracellular signaling mediated by its receptors expressed on different immune cells. Recent observations suggest that the immune system is an important component in tumoural angiogenesis. Therefore, immune modulation could have an impact in anti-angiogenic therapy as a new therapeutic strategy, which in turn might improve effectiveness of treatment in cancer patients.

T Lymphocyte-Endothelial Interactions: Emerging Understanding of Trafficking and Antigen-Specific Immunity

Antigen-specific immunity requires regulated trafficking of T cells in and out of diverse tissues in order to orchestrate lymphocyte development, immune surveillance, responses, and memory. The endothelium serves as a unique barrier, as well as a sentinel, between the blood and the tissues, and as such it plays an essential locally tuned role in regulating T cell migration and information exchange. While it is well established that chemoattractants and adhesion molecules are major determinants of T cell trafficking, emerging studies have now enumerated a large number of molecular players as well as a range of discrete cellular remodeling activities (e.g., transmigratory cups and invadosome-like protrusions) that participate in directed migration and pathfinding by T cells. In addition to providing trafficking cues, intimate cell-cell interaction between lymphocytes and endothelial cells provide instruction to T cells that influence their activation and differentiation states. Perhaps the most intriguing and underappreciated of these "sentinel" roles is the ability of the endothelium to act as a non-hematopoietic "semiprofessional" antigen-presenting cell. Close contacts between circulating T cells and antigen-presenting endothelium may play unique non-redundant roles in shaping adaptive immune responses within the periphery. A better understanding of the mechanisms directing T cell trafficking and the antigen-presenting role of the endothelium may not only increase our knowledge of the adaptive immune response but also empower the utility of emerging immunomodulatory therapeutics.

Activated endothelial cells limit inflammatory response, but increase chemoattractant potential and bacterial clearance by human monocytes

Inflammation is the normal immune response of vascularized tissues to damage and bacterial products, for which leukocyte transendothelial migration (TEM) is critical. The effects of cell-to-cell contact seen in both leukocyte and endothelial cells include cytoskeleton rearrangement, and dynamic expression of adhesion molecules and metalloproteinases. TEM induces expression of anti-apoptotic molecules, costimulatory molecules associated with antigen presentation, and pattern recognition receptors (PRR), such as TLR-4, in monocytes. However, little is known about how TLR-4 increment operates in monocytes during an inflammatory response. To understand it better, we used an in vitro model in which monocytes crossed a layer of IL-1β stimulated Human Umbilical Vein Endothelial Cells (HUVEC). After TEM, monocytes were tested for the secretion of inflammatory cytokines and chemokines, their phenotype (CD14, CD16, TLR-4 expression), and TLR-4 canonical [Nuclear Factor kappa B, (NF-κB) pathway] and non-canonical [p38, extracellular signal-regulated kinases (ERK) 1/2 pathway] signal transduction induced by lipopolysaccharide (LPS). Phagocytosis and bacterial clearance were also measured. There was diminished secretion of LPS-induced inflammatory cytokines (IL-1β, IL-6, and TNF-α) and higher secretion of chemokines (CXCL8/IL-8 and CCL2/MCP-1) in supernatant of TEM monocytes. These changes were accompanied by increases in TLR-4, CD14 (surfaces expression), p38, and ERK1/2 phosphorylated cytoplasmic forms, without affecting NF-κB activation. It also increased bacterial clearance after TEM by an O2 -independent mechanism. The data suggest that interaction between endothelial cells and monocytes fine-tunes the inflammatory response and promotes bacterial elimination.

Myeloid-derived suppressor cells are involved in lysosomal acid lipase deficiency-induced endothelial cell dysfunctions

The underlying mechanisms that lysosomal acid lipase (LAL) deficiency causes infiltration of myeloid-derived suppressor cells (MDSCs) in multiple organs and subsequent inflammation remain incompletely understood. Endothelial cells (ECs), lining the inner layer of blood vessels, constitute barriers regulating leukocytes transmigration to the site of inflammation. Therefore, we hypothesized that ECs are dysfunctional in LAL-deficient (lal(-/-)) mice. We found that Ly6G(+) cells transmigrated more efficiently across lal(-/-) ECs than wild-type (lal(+/+)) ECs, which were associated with increased levels of PECAM-1 and MCP-1 in lal(-/-) ECs. In addition, lal(-/-) ECs showed enhanced migration and proliferation, decreased apoptosis, but impaired tube formation and angiogenesis. lal(-/-) ECs also suppressed T cell proliferation in vitro. Interestingly, lal(-/-) Ly6G(+) cells promoted in vivo angiogenesis (including a tumor model), EC tube formation, and proliferation. Finally, the mammalian target of rapamycin (mTOR) pathway was activated in lal(-/-) ECs, and inhibition of mTOR reversed EC dysfunctions, including decreasing Ly6G(+) cell transmigration, delaying migration, and relieving suppression of T cell proliferation, which was mediated by decreasing production of reactive oxygen species. Our results indicate that LAL regulates EC functions through interaction with MDSCs and modulation of the mTOR pathway, which may provide a mechanistic basis for targeting MDSCs or mTOR to rejuvenate EC functions in LAL deficiency-related diseases.

CD47-dependent immunomodulatory and angiogenic activities of extracellular vesicles produced by T cells

Intercellular communication is critical for integrating complex signals in multicellular eukaryotes. Vascular endothelial cells and T lymphocytes closely interact during the recirculation and trans-endothelial migration of T cells. In addition to direct cell-cell contact, we show that T cell derived extracellular vesicles can interact with endothelial cells and modulate their cellular functions. Thrombospondin-1 and its receptor CD47 are expressed on exosomes/ectosomes derived from T cells, and these extracellular vesicles are internalized and modulate signaling in both T cells and endothelial cells. Extracellular vesicles released from cells expressing or lacking CD47 differentially regulate activation of T cells induced by engaging the T cell receptor. Similarly, T cell-derived extracellular vesicles modulate endothelial cell responses to vascular endothelial growth factor and tube formation in a CD47-dependent manner. Uptake of T cell derived extracellular vesicles by recipient endothelial cells globally alters gene expression in a CD47-dependent manner. CD47 also regulates the mRNA content of extracellular vesicles in a manner consistent with some of the resulting alterations in target endothelial cell gene expression. Therefore, the thrombospondin-1 receptor CD47 directly or indirectly regulates intercellular communication mediated by the transfer of extracellular vesicles between vascular cells.