Recruitment mechanisms of primary and malignant B cells to the human liver

Chronic liver diseases: From development to novel pharmacological therapies: IUPHAR Review 37

Chronic liver diseases comprise a broad spectrum of burdensome diseases that still lack effective pharmacological therapies. Our research group focuses on fibrosis, which is a major precursor of liver cirrhosis. Fibrosis consists in a progressive disturbance of liver sinusoidal architecture characterised by connective tissue deposition as a reparative response to tissue injury. Multifactorial events and several types of cells participate in fibrosis initiation and progression, and the process still needs to be completely understood. The development of experimental models of liver fibrosis alongside the identification of critical factors progressing fibrosis to cirrhosis will facilitate the development of more effective therapeutic approaches for such condition. This review provides an overlook of the main process leading to hepatic fibrosis and therapeutic approaches that have emerged from a deep knowledge of the molecular regulation of fibrogenesis in the liver. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Liver sinusoidal endothelial cells show reduced scavenger function and downregulation of Fc gamma receptor IIb, yet maintain a preserved fenestration in the Glmpgt/gt mouse model of slowly progressing liver fibrosis

Liver sinusoidal endothelial cells (LSECs) are fenestrated endothelial cells with a unique, high endocytic clearance capacity for blood-borne waste macromolecules and colloids. This LSEC scavenger function has been insufficiently characterized in liver disease. The Glmpgt/gt mouse lacks expression of a subunit of the MFSD1/GLMP lysosomal membrane protein transporter complex, is born normal, but soon develops chronic, mild hepatocyte injury, leading to slowly progressing periportal liver fibrosis, and splenomegaly. This study examined how LSEC scavenger function and morphology are affected in the Glmpgt/gt model. FITC-labelled formaldehyde-treated serum albumin (FITC-FSA), a model ligand for LSEC scavenger receptors was administered intravenously into Glmpgt/gt mice, aged 4 months (peak of liver inflammation), 9-10 month, and age-matched Glmpwt/wt mice. Organs were harvested for light and electron microscopy, quantitative image analysis of ligand uptake, collagen accumulation, LSEC ultrastructure, and endocytosis receptor expression (also examined by qPCR and western blot). In both age groups, the Glmpgt/gt mice showed multifocal liver injury and fibrosis. The uptake of FITC-FSA in LSECs was significantly reduced in Glmpgt/gt compared to wild-type mice. Expression of LSEC receptors stabilin-1 (Stab1), and mannose receptor (Mcr1) was almost similar in liver of Glmpgt/gt mice and age-matched controls. At the same time, immunostaining revealed differences in the stabilin-1 expression pattern in sinusoids and accumulation of stabilin-1-positive macrophages in Glmpgt/gt liver. FcγRIIb (Fcgr2b), which mediates LSEC endocytosis of soluble immune complexes was widely and significantly downregulated in Glmpgt/gt liver. Despite increased collagen in space of Disse, LSECs of Glmpgt/gt mice showed well-preserved fenestrae organized in sieve plates but the frequency of holes >400 nm in diameter was increased, especially in areas with hepatocyte damage. In both genotypes, FITC-FSA also distributed to endothelial cells of spleen and bone marrow sinusoids, suggesting that these locations may function as possible compensatory sites of clearance of blood-borne scavenger receptor ligands in liver fibrosis.

The senescent secretome drives PLVAP expression in cultured human hepatic endothelial cells to promote monocyte transmigration

Liver sinusoidal endothelial cells (LSEC) undergo significant phenotypic change in chronic liver disease (CLD), and yet the factors that drive this process and the impact on their function as a vascular barrier and gatekeeper for immune cell recruitment are poorly understood. Plasmalemma-vesicle-associated protein (PLVAP) has been characterized as a marker of LSEC in CLD; notably we found that PLVAP upregulation strongly correlated with markers of tissue senescence. Furthermore, exposure of human LSEC to the senescence-associated secretory phenotype (SASP) led to a significant upregulation of PLVAP. Flow-based assays demonstrated that SASP-driven leukocyte recruitment was characterized by paracellular transmigration of monocytes while the majority of lymphocytes migrated transcellularly. Knockdown studies confirmed that PLVAP selectively supported monocyte transmigration mediated through PLVAP's impact on LSEC permeability by regulating phospho-VE-cadherin expression and endothelial gap formation. PLVAP may therefore represent an endothelial target that selectively shapes the senescence-mediated immune microenvironment in liver disease.

Primary hepatopancreatobiliary lymphoma: Pathogenesis, diagnosis, and management

Primary hepatopancreatobiliary lymphoma (PHPBL) is extremely rare, which is defined as a lympho-proliferative disease confined to the hepatobiliary system and pancreas without any involvement of lymph nodes, bone marrow, or other organs. The clinical and imaging manifestations of PHPBL are variable and non-special, which are akin to those of tumors of the hepatobiliary and pancreatic systems. The overall prognosis and management of PHPBL differ from those of other tumors in the hepatobiliary system and pancreas. Proper diagnosis and prompt treatment are essential for improving clinical outcomes. Due to its rarity, the optimal treatment has not been issued. However, combination chemotherapy is considered as a standard treatment for them. This review provides an overview of the pathogenesis, diagnosis, pathology, and management of PHPBL and offers clinicians the diagnosis and management schedule for PHPBL.

Senescence-induced endothelial phenotypes underpin immune-mediated senescence surveillance

Senescence is a stress-responsive tumor suppressor mechanism associated with expression of the senescence-associated secretory phenotype (SASP). Through the SASP, senescent cells trigger their own immune-mediated elimination, which if evaded leads to tumorigenesis. Senescent parenchymal cells are separated from circulating immunocytes by the endothelium, which is targeted by microenvironmental signaling. Here we show that SASP induces endothelial cell NF-κB activity and that SASP-induced endothelial expression of the canonical NF-κB component Rela underpins senescence surveillance. Using human liver sinusoidal endothelial cells (LSECs), we show that SASP-induced endothelial NF-κB activity regulates a conserved transcriptional program supporting immunocyte recruitment. Furthermore, oncogenic hepatocyte senescence drives murine LSEC NF-κB activity in vivo. Critically, we show two distinct endothelial pathways in senescence surveillance. First, endothelial-specific loss of Rela prevents development of Stat1-expressing CD4+ T lymphocytes. Second, the SASP up-regulates ICOSLG on LSECs, with the ICOS-ICOSLG axis contributing to senescence cell clearance. Our results show that the endothelium is a nonautonomous SASP target and an organizing center for immune-mediated senescence surveillance.

Scavenger Receptors: Novel Roles in the Pathogenesis of Liver Inflammation and Cancer

The scavenger receptor superfamily represents a highly diverse collection of evolutionarily-conserved receptors which are known to play key roles in host homeostasis, the most prominent of which is the clearance of unwanted endogenous macromolecules, such as oxidized low-density lipoproteins, from the systemic circulation. Members of this family have also been well characterized in their binding and internalization of a vast range of exogenous antigens and, consequently, are generally considered to be pattern recognition receptors, thus contributing to innate immunity. Several studies have implicated scavenger receptors in the pathophysiology of several inflammatory diseases, such as Alzheimer's and atherosclerosis. Hepatic resident cellular populations express a diverse complement of scavenger receptors in keeping with the liver's homeostatic functions, but there is gathering interest in the contribution of these receptors to hepatic inflammation and its complications. Here, we review the expression of scavenger receptors in the liver, their functionality in liver homeostasis, and their role in inflammatory liver disease and cancer.

The Hepatic Sinusoid in Chronic Liver Disease: The Optimal Milieu for Cancer

Simple Summary

During the development of chronic liver disease, the hepatic sinusoid undergoes major changes that further compromise the hepatic function, inducing persistent inflammation and the formation of scar tissue, together with alterations in liver hemodynamics. This diseased background may induce the formation and development of hepatocellular carcinoma (HCC), which is the most common form of primary liver cancer and a major cause of mortality. In this review, we describe the ways in which the dysregulation of hepatic sinusoidal cells—including liver sinusoidal cells, Kupffer cells, and hepatic stellate cells—may have an important role in the development of HCC. Our review summarizes all of the known sinusoidal processes in both health and disease, and possible treatments focusing on the dysregulation of the sinusoid; finally, we discuss how some of these alterations occurring during chronic injury are shared with the pathology of HCC and may contribute to its development.

Abstract

The liver sinusoids are a unique type of microvascular beds. The specialized phenotype of sinusoidal cells is essential for their communication, and for the function of all hepatic cell types, including hepatocytes. Liver sinusoidal endothelial cells (LSECs) conform the inner layer of the sinusoids, which is permeable due to the fenestrae across the cytoplasm; hepatic stellate cells (HSCs) surround LSECs, regulate the vascular tone, and synthetize the extracellular matrix, and Kupffer cells (KCs) are the liver-resident macrophages. Upon injury, the harmonic equilibrium in sinusoidal communication is disrupted, leading to phenotypic alterations that may affect the function of the whole liver if the damage persists. Understanding how the specialized sinusoidal cells work in coordination with each other in healthy livers and chronic liver disease is of the utmost importance for the discovery of new therapeutic targets and the design of novel pharmacological strategies. In this manuscript, we summarize the current knowledge on the role of sinusoidal cells and their communication both in health and chronic liver diseases, and their potential pharmacologic modulation. Finally, we discuss how alterations occurring during chronic injury may contribute to the development of hepatocellular carcinoma, which is usually developed in the background of chronic liver disease.

Enhanced IL-9 secretion by p66Shc-deficient CLL cells modulates the chemokine landscape of the stromal microenvironment

The stromal microenvironment is central to chronic lymphocytic leukemia (CLL) pathogenesis. How leukemic cells condition the stroma to enhance its chemoattractant properties remains elusive. Here, we show that mouse and human CLL cells promote the contact-independent stromal expression of homing chemokines. This function was strongly enhanced in leukemic cells from Eμ-TCL1 mice lacking the pro-oxidant p66Shc adaptor, which develop an aggressive disease with organ infiltration. We identified interleukin-9 (IL-9) as the soluble factor, negatively modulated by p66Shc, that is responsible for the chemokine-elevating activity of leukemic cells on stromal cells. IL-9 blockade in Eμ-TCL1/p66Shc-/- mice resulted in a decrease in the nodal expression of homing chemokines, which correlated with decreased leukemic cell invasiveness. IL-9 levels were found to correlate inversely with residual p66Shc in p66Shc-deficient human CLL cells (n = 52 patients). p66Shc reconstitution in CLL cells normalized IL-9 expression and neutralized their chemokine-elevating activity. Notably, high IL-9 expression in CLL cells directly correlates with lymphadenopathy, liver infiltration, disease severity, and overall survival, emerging as an independent predictor of disease outcome. Our results demonstrate that IL-9 modulates the chemokine landscape in the stroma and that p66Shc, by regulating IL-9 expression, fine tunes the ability of leukemic cells to shape the microenvironment, thereby contributing to CLL pathogenesis.

Primary Hepatic Lymphoma After Lung Transplantation: A Report of 2 Cases

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma in the posttransplant setting. Treatment is based on chemotherapy; surgery is still debated and should be performed in very select cases.

METHODS

We observed 2 patients out of 300 who underwent lung transplantation in the Nouvel Hopital Civil between 2013 and 2019 with primary hepatic lymphoma. Chemotherapy with a rituximab-cyclophosphamide, hydroxydaunorubicin, vincristine, prednisone protocol was performed in all patients. Mycophenolate mofetil was interrupted before treatment, and everolimus was introduced after chemotherapy by associating tacrolimus withdrawal.

RESULTS

One patient showed complete remission; after 7 years, no recurrence has been noticed. The second is still undergoing chemotherapy with no signs of disease progression.

CONCLUSIONS

DLBCL risk is higher in solid organ transplant recipients than in the general population. Primary hepatic lymphoma diagnosis is often difficult and based on histologic findings after initial clinical and radiological suspicion of primary or secondary liver neoplasia. Diagnosis is challenging because no clinical, radiological, or biological features exist. Biopsy is always indicated for histologic confirmation. Chemotherapy is the mainstay of therapy, but surgery may be indicated in very select patients.

Prognosis of primary hepatic lymphoma: A US population-based analysis

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Primary hepatic lymphoma (PHL) is a rare form of extranodal lymphomas, mainly invading the liver and local tissues.

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The incidence, clinical characteristics and survival of patients with PHL in the United States.

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An applicable PHL model can forecast the dynamic survival rate of patients with PHL.

Objective

Primary hepatic lymphoma (PHL) is a rare malignancy with lesions confined to the liver. It is characterized by a large number of monomorphic, medium-sized lymphocytic infiltrates in the hepatic sinusoid. Due to the rarity of this malignancy, our current understanding of PHL is limited.

Methods

We collected incidence, mortality, and clinical data of PHL patients diagnosed between 1975 and 2016 using the Surveillance, Epidemiology, and End Results (SEER) database. The annual percentage changes (APCs) and prognoses were analyzed using the Joinpoint and R package.

Results

Among the 1,372 patients, white males were prevalent, and the most common histological subtype was diffuse large B-cell lymphoma (DLBCL). The incidence and mortality rate of PHL was 0.075/100,000 person-years and 0.055/100,000 person-years, respectively. The annual incidence rate of PHL increased significantly, with an APC of 2.74% (P < 0.001). The 3- and 5-year overall survival (OS) rates of patients with PHL were 43.553% and 39.242%, respectively. The 3- and 5-year relative survival (RS) rates were 46.925% and 45.300%, respectively. Multivariate Cox regression analysis revealed that older age, black, DLBCL, and advanced-stage disease were independent predictors of unfavorable OS and RS. The C-index and receiver operating characteristic (ROC) analysis confirmed the prognostic value of the nomograms established in this study.

Conclusion

The nomogram established in this study is a robust tool to predict the prognosis of PHL patients.

The Role of Sinusoidal Endothelial Cells in the Axis of Inflammation and Cancer Within the Liver

Liver sinusoidal endothelial cells (LSEC) form a unique barrier between the liver sinusoids and the underlying parenchyma, and thus play a crucial role in maintaining metabolic and immune homeostasis, as well as actively contributing to disease pathophysiology. Whilst their endocytic and scavenging function is integral for nutrient exchange and clearance of waste products, their capillarisation and dysfunction precedes fibrogenesis. Furthermore, their ability to promote immune tolerance and recruit distinct immunosuppressive leukocyte subsets can allow persistence of chronic viral infections and facilitate tumour development. In this review, we present the immunological and barrier functions of LSEC, along with their role in orchestrating fibrotic processes which precede tumourigenesis. We also summarise the role of LSEC in modulating the tumour microenvironment, and promoting development of a pre-metastatic niche, which can drive formation of secondary liver tumours. Finally, we summarise closely inter-linked disease pathways which collectively perpetuate pathogenesis, highlighting LSEC as novel targets for therapeutic intervention.

New tools to prevent cancer growth and spread: a 'Clever' approach

Clever-1 (also known as Stabilin-1 and FEEL-1) is a scavenger receptor expressed on lymphatic endothelial cells, sinusoidal endothelial cells and immunosuppressive monocytes and macrophages. Its role in cancer growth and spread first became evident in Stab1^–/– knockout mice, which have smaller primary tumours and metastases. Subsequent studies in mice and humans have shown that immunotherapeutic blockade of Clever-1 can activate T-cell responses, and that this response is mainly mediated by a phenotypic change in macrophages and monocytes from immunosuppressive to pro-inflammatory following Clever-1 inhibition. Analyses of human cancer cohorts have revealed marked associations between the number of Clever-1-positive macrophages and patient outcome. As hardly any reports to date have addressed the role of Clever-1 in immunotherapy resistance and T-cell dysfunction, we performed data mining using several published cancer cohorts, and observed a remarkable correlation between Clever-1 positivity and resistance to immune checkpoint therapies. This result provides impetus and potential for the ongoing clinical trial targeting Clever-1 in solid tumours, which has so far shown a shift towards immune activation when a particular epitope of Clever-1 is blocked.

Fluorescent Multiplex Cell Rolling Assay: Simultaneous Capturing up to Seven Samples in Real-Time Using Spectral Confocal Microscopy

The parallel plate flow chamber assay is widely utilized to study physiological cell-cell adhesive interactions under dynamic flow that mimics the bloodstream. In this technique, the cells are perfused under defined shear stresses over a monolayer of endothelial cells (expressing homing molecules, e.g., selectins) or a surface (expressing recombinant homing molecules). However, with the need to study multiple samples and multiple parameters per sample, using a traditional bright-field microscope-based flow assay allows only one sample at a time to be analyzed, resulting in high interexperiment variability, the need for normalization, waste of materials, and significant consumption of time. We developed a multiplexing approach using a three-color fluorescence staining method, which allowed for up to seven different combination signatures to be run at one time. Using this fluorescent multiplex cell rolling (FMCR) assay, each sample is labeled with a different signature of emission wavelengths and mixed with other samples just minutes before the flow run. Subsequently, real-time images are acquired in a single pass using a line-scanning spectral confocal microscope. To illustrate the glycan-dependent binding of E-selectin, a central molecule in cell migration, to its glycosylated ligands expressed on myeloid-leukemic cells in flow, the FMCR assay was used to analyze E-selectin-ligand interactions following the addition (fucosyltransferase-treatment) or removal (deglycosylation) of key glycans on the flowing cells. The FMCR assay allowed us to analyze the cell-adhesion events from these different treatment conditions simultaneously in a competitive manner and to calculate differences in rolling frequency, velocity, and tethering capability of cells under study.

P66Shc: A Pleiotropic Regulator of B Cell Trafficking and a Gatekeeper in Chronic Lymphocytic Leukemia

Neoplastic B cells from chronic lymphocytic leukemia patients (CLL) have a profound deficiency in the expression of p66Shc, an adaptor protein with pro-apoptotic and pro-oxidant activities. This defect results in leukemic B cell resistance to apoptosis and additionally impinges on the balance between chemokine receptors that control B cell homing to secondary lymphoid organs and the sphingosine phosphate receptor S1PR1 that controls their egress therefrom, thereby favoring leukemic B cell accumulation in the pro-survival lymphoid niche. Ablation of the gene encoding p66Shc in the Eµ-TCL1 mouse model of human CLL enhances leukemogenesis and promotes leukemic cell invasiveness in both nodal and extranodal organs, providing in vivo evidence of the pathogenic role of the p66Shc defect in CLL pathogenesis. Here we present an overview of the functions of p66Shc in B lymphocytes, with a specific focus on the multiple mechanisms exploited by p66Shc to control B cell trafficking and the abnormalities in this process caused by p66Shc deficiency in CLL.

The Endothelium as a Driver of Liver Fibrosis and Regeneration

Liver fibrosis is a common feature of sustained liver injury and represents a major public health problem worldwide. Fibrosis is an active research field and discoveries in the last years have contributed to the development of new antifibrotic drugs, although none of them have been approved yet. Liver sinusoidal endothelial cells (LSEC) are highly specialized endothelial cells localized at the interface between the blood and other liver cell types. They lack a basement membrane and display open channels (fenestrae), making them exceptionally permeable. LSEC are the first cells affected by any kind of liver injury orchestrating the liver response to damage. LSEC govern the regenerative process initiation, but aberrant LSEC activation in chronic liver injury induces fibrosis. LSEC are also main players in fibrosis resolution. They maintain liver homeostasis and keep hepatic stellate cell and Kupffer cell quiescence. After sustained hepatic injury, they lose their phenotype and protective properties, promoting angiogenesis and vasoconstriction and contributing to inflammation and fibrosis. Therefore, improving LSEC phenotype is a promising strategy to prevent liver injury progression and complications. This review focuses on changes occurring in LSEC after liver injury and their consequences on fibrosis progression, liver regeneration, and resolution. Finally, a synopsis of the available strategies for LSEC-specific targeting is provided.

Vessel co-option in cancer

All solid tumours require a vascular supply in order to progress. Although the ability to induce angiogenesis (new blood vessel growth) has long been regarded as essential to this purpose, thus far, anti-angiogenic therapies have shown only modest efficacy in patients. Importantly, overshadowed by the literature on tumour angiogenesis is a long-standing, but continually emerging, body of research indicating that tumours can grow instead by hijacking pre-existing blood vessels of the surrounding nonmalignant tissue. This process, termed vessel co-option, is a frequently overlooked mechanism of tumour vascularization that can influence disease progression, metastasis and response to treatment. In this Review, we describe the evidence that tumours located at numerous anatomical sites can exploit vessel co-option. We also discuss the proposed molecular mechanisms involved and the multifaceted implications of vessel co-option for patient outcomes.

Abnormalities in chemokine receptor recycling in chronic lymphocytic leukemia

In addition to their modulation through de novo expression and degradation, surface levels of chemokine receptors are tuned by their ligand-dependent recycling to the plasma membrane, which ensures that engaged receptors become rapidly available for further rounds of signaling. Dysregulation of this process contributes to the pathogenesis of chronic lymphocytic leukemia (CLL) by enhancing surface expression of chemokine receptors, thereby favoring leukemic cell accumulation in the protective niche of lymphoid organs. In this review, we summarize our current understanding of the process of chemokine receptor recycling, focusing on the impact of its dysregulation in CLL.

The Role of Stabilin-1 in Lymphocyte Trafficking and Macrophage Scavenging in the Liver Microenvironment

Chronic liver diseases are a major global health burden, and cases of these conditions continue to rise in many countries. A diverse range of insults can lead to chronic liver disease, but they are all characterised by the infiltration and accumulation of immune cells within liver tissue and, if progressive, can lead to tissue fibrosis and cirrhosis. In this review, we focus on the role of stabilin-1 in two key processes that contribute to liver disease, namely, the recruitment of lymphocytes into liver tissue and the response of macrophages to tissue injury. Stabilin-1 is constitutively expressed on the sinusoidal endothelium of the liver and contributes to the homeostatic scavenging function of these cells. Epithelial damage in the context of chronic liver disease leads to the upregulation of stabilin-1 at sites of tissue injury, specifically at sites of immune cell recruitment and on subpopulations of hepatic macrophages. Functionally, stabilin-1 has been shown to mediate transendothelial migration of lymphocyte subsets in the setting of pro-inflammatory-activated human liver endothelium. In experimental models of liver fibrosis, stabilin-1 promotes the uptake of products of chronic oxidative stress by a subset of hepatic macrophages and suppresses their release of pro-inflammatory mediators that regulate tissue remodelling. These studies highlight the active contribution that scavenger receptors such as stabilin-1 can make in regulating chronic inflammation and tissue fibrosis, and their potential as novel therapeutic targets for these conditions.

p66Shc deficiency in the Eμ-TCL1 mouse model of chronic lymphocytic leukemia enhances leukemogenesis by altering the chemokine receptor landscape

The Shc family adaptor p66Shc acts as a negative regulator of proliferative and survival signals triggered by the B-cell receptor and, by enhancing the production of reactive oxygen species, promotes oxidative stress-dependent apoptosis. Additionally, p66Shc controls the expression and function of chemokine receptors that regulate lymphocyte traffic. Chronic lymphocytic leukemia cells have a p66Shc expression defect which contributes to their extended survival and correlates with poor prognosis. We analyzed the impact of p66Shc ablation on disease severity and progression in the Eμ-TCL1 mouse model of chronic lymphocytic leukemia. We showed that Eμ-TCL1/p66Shc^-/- mice developed an aggressive disease that had an earlier onset, occurred at a higher incidence and led to earlier death compared to that in Eμ-TCL1 mice. Eμ-TCL1/p66Shc^-/- mice displayed substantial leukemic cell accumulation in both nodal and extranodal sites. The target organ selectivity correlated with upregulation of chemokine receptors whose ligands are expressed therein. This also applied to chronic lymphocytic leukemia cells, where chemokine receptor expression and extent of organ infiltration were found to correlate inversely with these cells' level of p66Shc expression. p66Shc expression declined with disease progression in Eμ-TCL1 mice and could be restored by treatment with the Bruton tyrosine kinase inhibitor ibrutinib. Our results highlight p66Shc deficiency as an important factor in the progression and severity of chronic lymphocytic leukemia and underscore p66Shc expression as a relevant therapeutic target.

Follicular helper T cell and memory B cell immunity in CHC patients

Chronic hepatitis C (CHC) is associated with biological activity of T follicular helper (Tfh) cells and memory B cells (MBCs). However, the nature of Tfh cell subsets that are responsible for MBCs in CHC patients has not been evaluated. This study aimed to investigate Tfh and MBC immunity before and after direct-acting antiviral (DAA) therapy in patients with CHC. A total of 31 CHC patients and 15 healthy controls (HCs) were recruited. Individual patients were treated with sofosbuvir/ribavirin (SOF/RBV) or in combination with pegylated interferon alpha-2a (PEG-IFN-α-2a) for 12 weeks. Immunofluorescence revealed the frequency of ICOS⁺CD4⁺CXCR5⁺ active Tfh cells in liver tissue of CHC patients was higher than that of healthy control. Tfh and B cell co-culture experiments showed that Tfh2 cells from CHC patients have potential ability to induce B cell differentiation and IgG production. Flow cytometry showed that the frequencies of CD21^-CD27⁺IgD^- activated MBCs, ICOS⁺CD4⁺CXCR5⁺ activated Tfh cells, Tfh1 (IFN-γ⁺CD4⁺CXCR5⁺) cells, and Tfh2 (IL-4⁺CD4⁺CXCR5⁺) cells, but not of Tfh17 (IL-17⁺CD4⁺CXCR5⁺) cells, increased in CHC patients before and after DAA therapy. Collectively, ICOS⁺ Tfh, Tfh1, Tfh2 cells, and MBCs participated in the antiviral treatment process of SOF/RBV with or without PEG-IFN-α-2a in CHC patients, and their activity was further enhanced during the treatment. KEY MESSAGES: This study aimed to investigate Tfh cells and MBC immunity in CHC patients. CD21^-CD27⁺IgD^- activated MBCs increased in CHC patients before and after treatment. Tfh1 and Tfh2 cells increased in CHC patients before and after antiviral treatment. Intrahepatic activated Tfh cells increased in CHC patients before treatment. Tfh2 cells from CHC patients have a stronger ability to induce B cell differentiation.

More Than Just a Removal Service: Scavenger Receptors in Leukocyte Trafficking

Scavenger receptors are a highly diverse superfamily of proteins which are grouped by their inherent ability to bind and internalize a wide array of structurally diverse ligands which can be either endogenous or exogenous in nature. Consequently, scavenger receptors are known to play important roles in host homeostasis, with common endogenous ligands including apoptotic cells, and modified low density lipoproteins (LDLs); additionally, scavenger receptors are key regulators of inflammatory diseases, such as atherosclerosis. Also, as a consequence of their affinity for a wide range of microbial products, their role in innate immunity is also being increasingly studied. However, in this review, a secondary function of a number of endothelial-expressed scavenger receptors is discussed. There is increasing evidence that some endothelial-expressed scavenger receptors are able to directly bind leukocyte-expressed ligands and subsequently act as adhesion molecules in the trafficking of leukocytes in lymphatic and vascular tissues. Here, we cover the current literature on this alternative role for endothelial-expressed scavenger receptors and also speculate on their therapeutic potential.

Enhanced Antibody Production in Clever-1/Stabilin-1-Deficient Mice

Clever-1, encoded by the Stab1 gene, is a scavenger and leukocyte trafficking receptor expressed by subsets of vascular and lymphatic endothelial cells and immunosuppressive macrophages. Monocyte Clever-1 also modulates T cell activation. However, nothing is known about the possible links between B cell function and Clever-1. Here, we found that Stab1 knockout mice (Stab1^−/−) lacking the Clever-1 protein from all cells present with abnormally high antibody levels under resting conditions and show enhanced humoral immune responses after immunization with protein and carbohydrate antigens. Removal of the spleen does not abolish the augmented basal and post-immunization antibody levels in Clever-1–deficient mice. The increased IgG production is also present in mice in which Clever-1 is selectively ablated from macrophages. When compared to wildtype macrophages, Clever-1–deficient macrophages show increased TNF-α synthesis. In co-culture experiments, monocytes/macrophages deficient of Clever-1 support higher IgM production by B cells, which is blocked by TNF-α depletion. Collectively, our data show that the excessive inflammatory activity of monocytes/macrophages in the absence of Clever-1 results in augmented humoral immune responses in vivo.

Vascular adhesion protein-1 is elevated in primary sclerosing cholangitis, is predictive of clinical outcome and facilitates recruitment of gut-tropic lymphocytes to liver in a substrate-dependent manner

OBJECTIVE

Primary sclerosing cholangitis (PSC) is the classical hepatobiliary manifestation of IBD. This clinical association is linked pathologically to the recruitment of mucosal T cells to the liver, via vascular adhesion protein (VAP)-1-dependent enzyme activity. Our aim was to examine the expression, function and enzymatic activation of the ectoenzyme VAP-1 in patients with PSC.

DESIGN

We examined VAP-1 expression in patients with PSC, correlated levels with clinical characteristics and determined the functional consequences of enzyme activation by specific enzyme substrates on hepatic endothelium.

RESULTS

The intrahepatic enzyme activity of VAP-1 was elevated in PSC versus immune-mediated disease controls and non-diseased liver (p<0.001). The adhesion of gut-tropic α4β7⁺lymphocytes to hepatic endothelial cells in vitro under flow was attenuated by 50% following administration of the VAP-1 inhibitor semicarbazide (p<0.01). Of a number of natural VAP-1 substrates tested, cysteamine-which can be secreted by inflamed colonic epithelium and gut bacteria-was the most efficient (yielded the highest enzymatic rate) and efficacious in its ability to induce expression of functional mucosal addressin cell adhesion molecule-1 on hepatic endothelium. In a prospectively evaluated patient cohort with PSC, elevated serum soluble (s)VAP-1 levels predicted poorer transplant-free survival for patients, independently (HR: 3.85, p=0.003) and additively (HR: 2.02, p=0.012) of the presence of liver cirrhosis.

CONCLUSIONS

VAP-1 expression is increased in PSC, facilitates adhesion of gut-tropic lymphocytes to liver endothelium in a substrate-dependent manner, and elevated levels of its circulating form predict clinical outcome in patients.

SCARF1: a multifaceted, yet largely understudied, scavenger receptor

BACKGROUND

As is a prerequisite of belonging to the scavenger receptor super family, SCARF1 (scavenger receptor class F, member 1) is known to play a key role in the binding and endocytosis of a wide range of endogenous and exogenous ligands.

FINDINGS

Unlike most scavenger receptors, SCARF1 is an essential protein, as SCARF1-deficient mice exhibit a severe resting phenotype in which they develop systemic lupus erythematosus (SLE)-like disease, thus highlighting the importance of SCARF1-mediated clearance of apoptotic host cells in homeostasis. In addition, a number of other roles in homeostasis and disease pathology have also been suggested, including roles in both innate and adaptive immunity; however, the majority of these studies have utilised transfected cell lines engineered to ectopically express SCARF1 and very few have utilised in vivo or ex vivo approaches.

CONCLUSION

This review summarises our current knowledge on SCARF1 biology and reflects on future directions for research on this multifaceted, yet largely understudied, scavenger receptor.

Changes in natural killer cells and exhausted memory regulatory T Cells with corticosteroid therapy in acute autoimmune hepatitis

Autoimmune hepatitis (AIH) is an immune-mediated liver disease currently treated by immunosuppressive medications with significant side effects. Thus, novel mechanistic treatments are greatly needed. We performed prospective deep immunophenotyping of blood immune cells in patients with acute AIH before and after corticosteroid therapy. Blood samples from 26 patients with acute AIH (United Kingdom-AIH Consortium) were phenotyped by flow cytometry at baseline and 4 months after starting corticosteroids. Pretreatment liver tissues were stained for forkhead box P3-positive (FOXP3POS) regulatory T cells (Tregs), clusters of differentiation (CD)56POS natural killer (NK) cells, and chemokine (C-X-C motif) ligand 10. Chemokine secretion by cultured primary hepatocyte and biliary epithelial cells was measured by enzyme-linked immunosorbent assay. Functional coculture assays with stimulated NK cells and Tregs were performed. CD161 ligand, lectin-like transcript-1 expression by intrahepatic immune cells was demonstrated with flow cytometry. Frequencies of NKbright cells declined with therapy (P < 0.001) and correlated with levels of alanine aminotransferase (P = 0.023). The Treg:NKbright ratio was lower pretreatment, and Tregs had an activated memory phenotype with high levels of CD39, cytotoxic T lymphocyte antigen 4, and FOXP3 but also high programmed death ligand 1, indicating exhaustion. Coculture experiments suggested the Tregs could not efficiently suppress interferon-γ secretion by NK cells. Both Tregs and NK cells had high expression of liver infiltration and T helper 17 plasticity-associated marker CD161 (P = 0.04). Pretreatment and CD161pos NK cells expressed high levels of perforin and granzyme B, consistent with an activated effector phenotype (P < 0.05). Lectin-like transcript 1, a ligand for CD161, is expressed on intrahepatic B cells, monocytes, and neutrophils. Conclusion: Activated effector NK cells, which correlate with biochemical measurements of hepatitis, and exhausted memory Tregs are increased in the blood of patients with treatment-naive AIH and decline with corticosteroid therapy. Inadequate regulation of NK cells by exhausted FOXP3pos Tregs may play a role in AIH pathogenesis and contribute to liver injury. (Hepatology Communications 2018;2:421-436).

Liver sinusoidal endothelial cells - gatekeepers of hepatic immunity

Liver sinusoidal endothelial cells (LSECs) line the low shear, sinusoidal capillary channels of the liver and are the most abundant non-parenchymal hepatic cell population. LSECs do not simply form a barrier within the hepatic sinusoids but have vital physiological and immunological functions, including filtration, endocytosis, antigen presentation and leukocyte recruitment. Reflecting these multifunctional properties, LSECs display unique structural and phenotypic features that differentiate them from the capillary endothelium present within other organs. It is now clear that LSECs have a critical role in maintaining immune homeostasis within the liver and in mediating the immune response during acute and chronic liver injury. In this Review, we outline how LSECs influence the immune microenvironment within the liver and discuss their contribution to immune-mediated liver diseases and the complications of fibrosis and carcinogenesis.

SCARF-1 promotes adhesion of CD4+ T cells to human hepatic sinusoidal endothelium under conditions of shear stress

Liver-resident cells are constantly exposed to gut-derived antigens via portal blood and, as a consequence, they express a unique repertoire of scavenger receptors. Whilst there is increasing evidence that the gut contributes to chronic inflammatory liver disease, the role of scavenger receptors in regulating liver inflammation remains limited. Here, we describe for the first time the expression of scavenger receptor class F, member 1 (SCARF-1) on hepatic sinusoidal endothelial cells (HSEC). We report that SCARF-1 shows a highly localised expression pattern and co-localised with endothelial markers on sinusoidal endothelium. Analysis of chronically inflamed liver tissue demonstrated accumulation of SCARF-1 at sites of CD4⁺ T cell aggregation. We then studied the regulation and functional role of SCARF-1 in HSEC and showed that SCARF-1 expression by HSEC is regulated by proinflammatory cytokines and bacterial lipopolysaccharide (LPS). Furthermore, SCARF-1 expression by HSEC, induced by proinflammatory and gut-derived factors acts as a novel adhesion molecule, present in adhesive cup structures, that specifically supports CD4⁺ T cells under conditions of physiological shear stress. In conclusion, we show that SCARF-1 contributes to lymphocyte subset adhesion to primary human HSEC and could play an important role in regulating the inflammatory response during chronic liver disease.

Liver dysfunction in chronic lymphocytic leukemia: Prevalence, outcomes, and pathological findings

The prevalence of liver dysfunction and its association with outcomes in patients with previously untreated chronic lymphocytic leukemia (CLL) is unknown. Newly diagnosed (<12 months) previously untreated CLL patients seen at Mayo Clinic, Rochester, MN between 9/1993 and 4/2016 who had baseline assessment of at least one liver function test (LFT) were included in this analysis. The prevalence of liver dysfunction at baseline, proportion of patients who acquired LFT abnormalities, time to first therapy (TTFT) and overall survival (OS) were assessed. An abnormal LFT was present in 82/2336 (3.5%) patients at diagnosis and was associated with advanced Rai stage (Rai III-IV) (21% vs. 6%; P < .001), lower hemoglobin (13.1 g/dL vs. 13.9 g/dL; P < .001), and lower platelet count (187 × 109/L vs. 200 × 109/L; P = .03). Additionally, 236 patients with normal LFTs at diagnosis developed acquired liver dysfunction during follow-up. Patients with abnormal LFTs at diagnosis had a shorter OS compared to those with normal LFTs (HR 1.80 95% CI 1.13-2.87; P = .014, adjusted for age, sex, Rai stage, and treatment), although TTFT was not different. Of 52 patients who underwent a liver biopsy, CLL was present in liver tissue in 39/52 (73%) patients, with the portal tracts the most common region involved. Histopathology findings of liver involvement by CLL had limited correlation with choice of CLL therapy. In conclusion, approximately 1 of 25 newly diagnosed CLL patients has abnormal LFTs at diagnosis. Although the TTFT was not different among patients with abnormal LFTs, these patients have a shorter OS compared to those with normal LFTs.

Cell-Specific Variation in E-Selectin Ligand Expression among Human Peripheral Blood Mononuclear Cells: Implications for Immunosurveillance and Pathobiology

Both host defense and immunopathology are shaped by the ordered recruitment of circulating leukocytes to affected sites, a process initiated by binding of blood-borne cells to E-selectin displayed at target endothelial beds. Accordingly, knowledge of the expression and function of leukocyte E-selectin ligands is key to understanding the tempo and specificity of immunoreactivity. In this study, we performed E-selectin adherence assays under hemodynamic flow conditions coupled with flow cytometry and Western blot analysis to elucidate the function and structural biology of glycoprotein E-selectin ligands expressed on human PBMCs. Circulating monocytes uniformly express high levels of the canonical E-selectin binding determinant sialyl Lewis X (sLe^X) and display markedly greater adhesive interactions with E-selectin than do circulating lymphocytes, which exhibit variable E-selectin binding among CD4⁺ and CD8⁺ T cells but no binding by B cells. Monocytes prominently present sLe^X decorations on an array of protein scaffolds, including P-selectin glycoprotein ligand-1, CD43, and CD44 (rendering the E-selectin ligands cutaneous lymphocyte Ag, CD43E, and hematopoietic cell E-selectin/L-selectin ligand, respectively), and B cells altogether lack E-selectin ligands. Quantitative PCR gene expression studies of glycosyltransferases that regulate display of sLe^X reveal high transcript levels among circulating monocytes and low levels among circulating B cells, and, commensurately, cell surface α(1,3)-fucosylation reveals that acceptor sialyllactosaminyl glycans convertible into sLe^X are abundantly expressed on human monocytes yet are relatively deficient on B cells. Collectively, these findings unveil distinct cell-specific patterns of E-selectin ligand expression among human PBMCs, indicating that circulating monocytes are specialized to engage E-selectin and providing key insights into the molecular effectors mediating recruitment of these cells at inflammatory sites.

Canine Nervous System Lymphoma Subtypes Display Characteristic Neuroanatomical Patterns

Primary and secondary nervous system involvement occurs in 4% and 5%–12%, respectively, of all canine non-Hodgkin lymphomas. The recent new classification of canine malignant lymphomas, based on the human World Health Organization classification, has been endorsed with international acceptance. This histological and immunocytochemical classification provides a unique opportunity to study the histologic anatomic distribution patterns in the central and peripheral nervous system of these defined lymphoma subtypes. In this study, we studied a cohort of 37 dogs with lymphoma, which at necropsy had either primary (n = 1, 2.7%) or secondary (n = 36; 97.3%) neural involvement. These T- (n = 16; 43.2%) or B-cell (n = 21; 56.8%) lymphomas were further classified into 12 lymphoma subtypes, with predominant subtypes including peripheral T-cell lymphoma (PTCL) or diffuse large B-cell lymphoma (DLBCL), respectively. This systematic study identified 6 different anatomically based histologically defined patterns of lymphoma infiltration in the nervous system of dogs. Different and distinct combinations of anatomical patterns correlated with specific lymphoma subtypes. Lymphoma infiltration within the meningeal, perivascular, and periventricular compartments were characteristic of DLBCL, whereas peripheral nerve involvement was a frequent feature of PTCL. Similarly cell counts above 64 cells/μL in cerebrospinal samples correlated best with marked meningeal and periventricular lymphoma infiltration histologically. Prospective studies are needed in order to confirm the hypothesis that these combinations of histological neuroanatomic patterns reflect targeting of receptors specific for the lymphoma subtypes at these various sites.

Integrated Bioinformatics Approach Reveals Crosstalk Between Tumor Stroma and Peripheral Blood Mononuclear Cells in Breast Cancer

Breast cancer is now the leading cause of cancer death in women worldwide. Cancer progression is driven not only by cancer cell intrinsic alterations and interactions with tumor microenvironment, but also by systemic effects. Integration of multiple profiling data may provide insights into the underlying molecular mechanisms of complex systemic processes. We performed a bioinformatic analysis of two public available microarray datasets for breast tumor stroma and peripheral blood mononuclear cells, featuring integrated transcriptomics data, protein-protein interactions (PPIs) and protein subcellular localization, to identify genes and biological pathways that contribute to dialogue between tumor stroma and the peripheral circulation. Genes of the integrin family as well as CXCR4 proved to be hub nodes of the crosstalk network and may play an important role in response to stroma-derived chemoattractants. This study pointed to potential for development of therapeutic strategies that target systemic signals travelling through the circulation and interdict tumor cell recruitment.

Crossing the Vascular Wall: Common and Unique Mechanisms Exploited by Different Leukocyte Subsets during Extravasation

Leukocyte extravasation is one of the essential and first steps during the initiation of inflammation. Therefore, a better understanding of the key molecules that regulate this process may help to develop novel therapeutics for treatment of inflammation-based diseases such as atherosclerosis or rheumatoid arthritis. The endothelial adhesion molecules ICAM-1 and VCAM-1 are known as the central mediators of leukocyte adhesion to and transmigration across the endothelium. Engagement of these molecules by their leukocyte integrin receptors initiates the activation of several signaling pathways within both leukocytes and endothelium. Several of such events have been described to occur during transendothelial migration of all leukocyte subsets, whereas other mechanisms are known only for a single leukocyte subset. Here, we summarize current knowledge on regulatory mechanisms of leukocyte extravasation from a leukocyte and endothelial point of view, respectively. Specifically, we will focus on highlighting common and unique mechanisms that specific leukocyte subsets exploit to succeed in crossing endothelial monolayers.

Rapid activation and hepatic recruitment of innate-like regulatory B cells after invariant NKT cell stimulation in mice

BACKGROUND & AIMS

Invariant natural killer T (iNKT) cells are present within the liver and have been implicated in the development of many liver diseases. Upon activation by glycolipid ligands (including α-galactosylceramide; αGalCer), hepatic iNKT cells produce numerous cytokines and recruit both pro-inflammatory and regulatory immune cells. However, the involvement of B cells in this process is poorly defined.

METHODS

Wild-type (male, C57BL/6), B cell deficient, or B cell depleted mice were injected with αGalCer or vehicle, hepatic B cell phenotype and liver injury was subsequently determined.

RESULTS

iNKT cell activation resulted in liver injury and the rapid activation and hepatic recruitment of B cells (mainly innate-like B1 and MZ-like B cells) from the spleen and peritoneal cavity. B cells recruited to the liver produce IL-10 and TGFβ, and express cell surface CD73 (ectoenzyme which generates adenosine). B cell deficient mice developed augmented αGalCer-induced hepatitis, enhanced neutrophil recruitment and striking alterations in the hepatic cytokine milieu. αGalCer-induced hepatitis was unaltered in IL-10(-/-) mice, or after TGFβ neutralization, but was significantly worsened in mice treated with a CD73 inhibitor.

CONCLUSIONS

iNKT cell stimulation recruits innate-like regulatory B cells to the liver which suppress hepatic inflammation through IL-10 and TGFβ1 independent mechanisms, but involve CD73 activity. These findings highlight an important inflammation suppressing role for B cells at early time points during the development of an innate immune response within the liver, and represent a potential therapeutic target for the treatment of liver disease.

CMV infection of human sinusoidal endothelium regulates hepatic T cell recruitment and activation

BACKGROUND & AIMS

Human cytomegalovirus infection (HCMV) is associated with an increased morbidity after liver transplantation, by facilitating allograft rejection and accelerating underlying hepatic inflammation. We hypothesized that human hepatic sinusoidal endothelial cells infected with HCMV possess the capacity to modulate allogeneic T cell recruitment and activation, thereby providing a plausible mechanism of how HCMV infection is able to enhance hepatic immune activation.

METHODS

Human hepatic sinusoidal endothelial cells were isolated from explanted livers and infected with recombinant endotheliotropic HCMV. We used static and flow-based models to quantify adhesion and transendothelial migration of allogeneic T cell subsets and determine their post-migratory phenotype and function.

RESULTS

HCMV infection of primary human hepatic sinusoidal endothelial cells facilitated ICAM-1 and CXCL10-dependent CD4 T cell transendothelial migration under physiological levels of shear stress. Recruited T cells were primarily non-virus-specific CXCR3(hi) effector memory T cells, which demonstrated features of LFA3-dependent Th1 activation after migration, and activated regulatory T cells, which retained a suppressive phenotype following transmigration.

CONCLUSIONS

The ability of infected hepatic endothelium to recruit distinct functional CD4 T cell subsets shows how HCMV facilitates hepatic inflammation and immune activation and may simultaneously favor virus persistence.

Oncogenic c-Myc-induced lymphomagenesis is inhibited non-redundantly by the p19Arf-Mdm2-p53 and RP-Mdm2-p53 pathways

The multifaceted oncogene c-Myc plays important roles in the development and progression of human cancer. Recent in vitro and in vivo studies have shown that the p19Arf-Mdm2-p53 and the ribosomal protein (RP)-Mdm2-p53 pathways are both essential in preventing oncogenic c-Myc-induced tumorigenesis. Disruption of each pathway individually by p19Arf deletion or by Mdm2(C305F) mutation, which disrupts RP-Mdm2 binding, accelerates Eμ-myc transgene-induced pre-B/B-cell lymphoma in mice at seemingly similar paces with median survival around 10 and 11 weeks, respectively, compared to 20 weeks for Eμ-myc transgenic mice. Because p19Arf can inhibit ribosomal biogenesis through its interaction with nucleophosmin (NPM/B23), RNA helicase DDX5 and RNA polymerase I transcription termination factor (TTF-I), it has been speculated that the p19Arf-Mdm2-p53 and the RP-Mdm2-p53 pathways might be a single p19Arf-RP-Mdm2-p53 pathway, in which p19Arf activates p53 by inhibiting RP biosynthesis; thus, p19Arf deletion or Mdm2(C305F) mutation would result in similar consequences. Here, we generated mice with concurrent p19Arf deletion and Mdm2(C305F) mutation and investigated the compound mice for tumorigenesis in the absence and the presence of oncogenic c-Myc overexpression. In the absence of Eμ-myc transgene, the Mdm2(C305F) mutation did not elicit spontaneous tumors in mice, nor did it accelerate spontaneous tumors in mice with p19Arf deletion. In the presence of Eμ-myc transgene, however, Mdm2(C305F) mutation significantly accelerated p19Arf deletion-induced lymphomagenesis and promoted rapid metastasis. We found that when p19Arf-Mdm2-p53 and RP-Mdm2-p53 pathways are independently disrupted, oncogenic c-Myc-induced p53 stabilization and activation is only partially attenuated. When both pathways are concurrently disrupted, however, c-Myc-induced p53 stabilization and activation are essentially obliterated. Thus, the p19Arf-Mdm2-p53 and the RP-Mdm2-p53 are non-redundant pathways possessing similar capabilities to activate p53 upon c-Myc overexpression.

Inhibition of lymphoma vascularization and dissemination by estrogen receptor β agonists

Most lymphomas show an increased incidence and poorer prognosis in males vs females, suggesting endocrine regulation. We have previously shown that tumor growth in vivo of a murine T-cell-derived lymphoma is repressed following activation of estrogen receptor β (ERβ, ESR2). By using ERβ-deficient mice, we now demonstrate that this inhibition is mediated via a direct effect on the tumor cells and not on the microenvironment. Furthermore, we show that the growth-suppressing effects of ERβ agonist are also valid for human B-cell lymphomas as demonstrated in tumors derived from Granta-519 mantle cell lymphoma (MCL) and Raji Burkitt lymphoma (BL) cells. In Granta-519 MCL tumors, activation of ERβ reduced expression of BAFF and GRB7, 2 important molecules involved in B-cell proliferation and survival. Importantly, activation of ERβ inhibited angiogenesis and lymphangiogenesis, possibly mediated by impaired vascular endothelial growth factor C expression. Furthermore, using disseminating Raji BL cells, we show that ERβ activation reduces dissemination of grafted Raji BL tumors. We also show by immunohistochemistry that ERβ is expressed in primary MCL tissue. These results suggest that targeting ERβ with agonists may be valuable in the treatment of some lymphomas, affecting several aspects of the malignant process, including proliferation, vascularization, and dissemination.

Update on primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) remains one of the most challenging conditions of clinical hepatology. There has been a steady growth in research to overcome this fact and the present review aims at summarizing the most recently published literature. The main emphasis will be put on the link of recent pathogenetic insights to clinical characteristics and patient management. With regard to pathogenesis, there is no consensus yet as to whether immune mediated injury or factors related to bile acid physiology are the most important. It also remains to be clarified whether PSC is a mixed bag of various secondary etiologies yet to be defined, or a disease entity predominantly represented by sclerosing cholangitis in the context of inflammatory bowel disease. Most important, there is no available medical therapy with proven influence on clinical end points, and timing of liver transplantation and patient follow-up are challenging due to the unpredictable and high risk of cholangiocarcinoma.

VCAM-1 and VAP-1 recruit myeloid cells that promote pulmonary metastasis in mice

Pulmonary metastasis is a frequent cause of poor outcome in cancer patients. The formation of pulmonary metastasis is greatly facilitated by recruitment of myeloid cells, which are crucial for tumor cell survival and extravasation. During inflammation, homing of myeloid cells is mediated by endothelial activation, raising the question of a potential role for endothelial activation in myeloid cell recruitment during pulmonary metastasis. Here, we show that metastatic tumor cell attachment causes the induction of the endothelial activation markers vascular cell adhesion molecule-1 (VCAM-1) and vascular adhesion protein-1 (VAP-1). Induction of VCAM-1 is dependent on tumor cell-clot formation, decreasing upon induction of tissue factor pathway inhibitor or treatment with hirudin. Furthermore, inhibition of endothelial activation with a VCAM-1 blocking antibody or a VAP-1 small molecule inhibitor leads to reduced myeloid cell recruitment and diminished tumor cell survival and metastasis without affecting tumor cell adhesion. Simultaneous inhibition of VCAM-1 and VAP-1 does not result in further reduction in myeloid cell recruitment and tumor cell survival, suggesting that both act through closely related mechanisms. These results establish VCAM-1 and VAP-1 as mediators of myeloid cell recruitment in metastasis and identify VAP-1 as a potential target for therapeutic intervention to combat early metastasis.

IL-10-producing regulatory B cells in the pathogenesis of chronic hepatitis B virus infection

A regulatory subset of B cells has been found to modulate immune responses in autoimmunity, infection, and cancer, but it has not been investigated in the setting of human persistent viral infection. IL-10 is elevated in patients with chronic hepatitis B virus infection (CHB), but its cellular sources and impact on antiviral T cells have not been addressed. We investigated the role of IL-10 and regulatory B cells in the pathogenesis of CHB. Serum IL-10 levels were studied longitudinally in patients with CHB undergoing spontaneous disease flares. There was a close temporal correlation between IL-10 levels and fluctuations in viral load or liver inflammation. Blockade of IL-10 in vitro rescued polyfunctional virus-specific CD8 T cell responses. To investigate the potential contribution of regulatory B cells, their frequency was measured directly ex vivo and after exposure to stimuli relevant to hepatitis B virus (HBV) (CpG or HBV Ags). IL-10-producing B cells were enriched in patients, and their frequency correlated temporally with hepatic flares, both after stimulation and directly ex vivo. Phenotypically, these cells were predominantly immature (CD19(+)CD24(hi)CD38(hi)) ex vivo; sorted CD19(+)CD24(hi)CD38(hi) cells suppressed HBV-specific CD8 T cell responses in an IL-10-dependent manner. In summary, these data reveal a novel IL-10-producing subset of B cells able to regulate T cell immunity in CHB.