Functional insights into human macrophage response against Scedosporium apiospermum and Scedosporium dehoogii

Fungal infections caused by Scedosporium species are rising among immunocompromised and immunocompetent patients. Within the immunocompetent group, patients with cystic fibrosis (pwCF) are at high risk of developing a chronic airway colonization by these molds. While S. apiospermum is one of the major species encountered in the lungs of pwCF, S. dehoogii has rarely been reported. The innate immune response is believed to be critical for host defense against fungal infections. However, its role has only recently been elucidated and the immune mechanisms against Scedosporium species are currently unknown. In this context, we undertook a comparative investigation of macrophage-mediated immune responses toward S. apiospermum and S. dehoogii conidia. Our data showed that S. apiospermum and S. dehoogii conidia strongly stimulated the expression of a set of pro-inflammatory cytokines and chemokines such as IL-1β, IL-8, IL-6 and TNFα. We demonstrated that S. dehoogii was more potent in stimulating the early release of pro-inflammatory cytokines and chemokines while S. apiospermum induced a late inflammatory response at a higher level. Flow cytometry analysis showed that M1-like macrophages were able to internalize both S. apiospermum and S. dehoogii conidia, with a similar intracellular killing rate for both species. In conclusion, these results suggest that M1-like macrophages can rapidly initiate a strong immune response against both S. apiospermum and S. dehoogii. This response is characterized by a similar killing of internalized conidia, but a different time course of cytokine production.

Kidney injury molecule 1 (KIM-1): a potential biomarker of acute kidney injury and tubulointerstitial injury in patients with ANCA-glomerulonephritis

Background

Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein expressed by proximal tubular cells, recognized as an early, sensitive and specific urinary biomarker for kidney injury. Blood KIM-1 was recently associated with the severity of acute and chronic kidney damage but its value in antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis with glomerulonephritis (ANCA-GN) has not been studied. Thus, we analyzed its expression at ANCA-GN diagnosis and its relationship with clinical presentation, kidney histopathology and early outcomes.

Methods

We assessed KIM-1 levels and other pro-inflammatory molecules (C-reactive protein, interleukin-6, tumor necrosis factor α, monocyte chemoattractant protein-1 and pentraxin 3) at ANCA-GN diagnosis and after 6 months in patients included in the Maine-Anjou registry, which gathers data patients from four French Nephrology Centers diagnosed since January 2000.

Results

Blood KIM-1 levels were assessed in 54 patients. Levels were elevated at diagnosis and decreased after induction remission therapy. KIM-1 was associated with the severity of renal injury at diagnosis and the need for kidney replacement therapy. In opposition to other pro-inflammatory molecules, KIM-1 correlated with the amount of acute tubular necrosis and interstitial fibrosis/tubular atrophy (IF/TA) on kidney biopsy, but not with interstitial infiltrate or with glomerular involvement. In multivariable analysis, elevated KIM-1 predicted initial estimated glomerular filtration rate (β = -19, 95% CI -31, -7.6, P = .002).

Conclusion

KIM-1 appears as a potential biomarker for acute kidney injury and for tubulointerstitial injury in ANCA-GN. Whether KIM-1 is only a surrogate marker or is a key immune player in ANCA-GN pathogenesis remain to be determined.

Clusterin Neutralizes the Inflammatory and Cytotoxic Properties of Extracellular Histones in Sepsis

Rationale: Extracellular histones, released into the surrounding environment during extensive cell death, promote inflammation and cell death, and these deleterious roles have been well documented in sepsis. Clusterin (CLU) is a ubiquitous extracellular protein that chaperones misfolded proteins and promotes their removal. Objectives: We investigated whether CLU could protect against the deleterious properties of histones. Methods: We assessed CLU and histone expression in patients with sepsis and evaluated the protective role of CLU against histones in in vitro assays and in vivo models of experimental sepsis. Measurements and Main Results: We show that CLU binds to circulating histones and reduces their inflammatory, thrombotic, and cytotoxic properties. We observed that plasma CLU levels decreased in patients with sepsis and that the decrease was greater and more durable in nonsurvivors than in survivors. Accordingly, CLU deficiency was associated with increased mortality in mouse models of sepsis and endotoxemia. Finally, CLU supplementation improved mouse survival in a sepsis model. Conclusions: This study identifies CLU as a central endogenous histone-neutralizing molecule and suggests that, in pathologies with extensive cell death, CLU supplementation may improve disease tolerance and host survival.

The neonatal Fc receptor expression during macrophage differentiation is related to autophagy

The neonatal Fc receptor (FcRn) plays a central role in recycling and biodistributing immunoglobulin G. FcRn is also involved in many physiological immune functions as well as pathological immune responses in cancer or autoimmune diseases. Low levels of FcRn in tumor cells and the microenvironment is associated with poor prognosis in non-small cell lung cancers. Among cells that are present in the tumor microenvironment, macrophages express high levels of FcRn. Macrophages are involved in these pathophysiological contexts by their dual differentiation states of pro- or anti-inflammatory macrophages. However, variations in FcRn protein expression have not been described in macrophage subtypes. In this work, we studied FcRn expression in an in vitro model of pro- and anti-inflammatory macrophage differentiation. We demonstrated an inverse relation between FcRn protein and mRNA expression in macrophage populations. Autophagy, which is involved in protein degradation and acquisition of phagocytic function in macrophages, participated in regulating FcRn levels. Intravenous immunoglobulin protected FcRn against autophagosome degradation in anti-inflammatory macrophages. Our data demonstrate that autophagy participates in regulating FcRn expression in pro- and anti-inflammatory macrophages. This finding raises new questions concerning the regulation of FcRn in immune functions.

Antitumor strategies targeting macrophages: the importance of considering the differences in differentiation/polarization processes between human and mouse macrophages

Macrophages are the immune cells that accumulate the most in the majority of established tumors and this accumulation is associated with a poor prognosis. Tumor-associated macrophages (TAMs) produce inflammatory cytokines and growth factors that promote tumor expansion and metastasis. TAMs have recently emerged as targets of choice to restore an efficient antitumor response and to limit tumor growth. Many molecules targeting TAMs are actually evaluated in clinical trials, alone or in combination. While these molecules induce tumor regression and stimulate cytotoxic responses in mouse models of tumor development, results from early clinical trials are less impressive. In this review, we list the biological differences between human and mouse macrophages that help explain the different efficacy of antitumor strategies targeting TAMs between human and animal studies. Differences in the impact of survival and polarization factors and in the cytokines produced and markers expressed as well as the limitations of extrapolations based on in vitro models of TAM-like generation should be considered in order to improve the design and efficacy of antitumor drugs targeting TAMs.

Acetoacetate protects macrophages from lactic acidosis-induced mitochondrial dysfunction by metabolic reprograming

Lactic acidosis, the extracellular accumulation of lactate and protons, is a consequence of increased glycolysis triggered by insufficient oxygen supply to tissues. Macrophages are able to differentiate from monocytes under such acidotic conditions, and remain active in order to resolve the underlying injury. Here we show that, in lactic acidosis, human monocytes differentiating into macrophages are characterized by depolarized mitochondria, transient reduction of mitochondrial mass due to mitophagy, and a significant decrease in nutrient absorption. These metabolic changes, resembling pseudostarvation, result from the low extracellular pH rather than from the lactosis component, and render these cells dependent on autophagy for survival. Meanwhile, acetoacetate, a natural metabolite produced by the liver, is utilized by monocytes/macrophages as an alternative fuel to mitigate lactic acidosis-induced pseudostarvation, as evidenced by retained mitochondrial integrity and function, retained nutrient uptake, and survival without the need of autophagy. Our results thus show that acetoacetate may increase tissue tolerance to sustained lactic acidosis.

Lactic acidosis is a metabolic state that occurs in injured tissues. Here the authors show that macrophages, in order to remain functional in acidosis, reduce their mitochondrial mass by mitophagy and rely on autophagy for survival, with mitochondrial integrity retained using acetoacetate as alternative fuel.

Age-Related Expression of IFN-λ1 Versus IFN-I and Beta-Defensins in the Nasopharynx of SARS-CoV-2-Infected Individuals

SARS-CoV-2 coronavirus infection induces heterogeneous symptoms, ranging from asymptomatic to lethal forms. Severe forms usually occur in the elderly and/or individuals with comorbidities. Children generally remain asymptomatic to primary infection, suggesting that they may have an effective local innate immune response. IFN-I and -III have non-redundant protective roles against SARS-CoV-2, although sometimes damaging the host. The expression and role of anti-viral peptides during SARS-CoV-2 infection have thus far been little studied. We aimed to identify the innate immune molecules present at the SARS-CoV-2 entry point. We analyzed the mRNA levels of type I (IFN-α and -β) and type III (IFN-λ1-3) interferons and selected antiviral peptides (i.e., β-defensins 1-3, α-defensins [HNP1-3, HD5] pentraxin-3, surfactant protein D, the cathelicidin LL-37 and interleukin-26) in nasopharyngeal swabs from 226 individuals of various ages, either infected with SARS-CoV-2 (symptomatic or asymptomatic) or negative for the virus. We observed that infection induced selective upregulation of IFN-λ1 expression in pediatric subjects (≤15 years), whereas IFN-α, IFN-β, IFN-λ2/λ3, and β-defensin 1-3 expression was unaffected. Conversely, infection triggered upregulation of IFN-α, IFN-β, IFN-λ2/λ3, and β-defensin 1-3 mRNA expression in adults (15-65 years) and the elderly (≥ 65 years), but without modulation of IFN-λ1. The expression of these innate molecules was not associated with gender or symptoms. Expression of the interferon-stimulated genes IFITM1 and IFITM3 was upregulated in SARS-CoV-2-positive subjects and reached similar levels in the three age groups. Finally, age-related differences in nasopharyngeal innate immunity were also observed in SARS-CoV-2-negative subjects. This study shows that the expression patterns of IFN-I/-III and certain anti-viral molecules in the nasopharyngeal mucosa of SARS-CoV-2-infected subjects differ with age and suggests that susceptibility to SARS-CoV-2 may be related to intrinsic differences in the nature of mucosal anti-viral innate immunity.

Insights into the ligand binding specificity of SREC-II (scavenger receptor expressed by endothelial cells)

SREC-II (scavenger receptor expressed by endothelial cells-II) is a membrane protein encoded by the SCARF2 gene, with high homology to class F scavenger receptor SR-F1, but no known scavenging function. We produced the extracellular domain of SREC-II in a recombinant form and investigated its capacity to interact with common scavenger receptor ligands, including acetylated low density lipoprotein (AcLDL) and maleylated or acetylated BSA (MalBSA or AcBSA). Whereas no binding was observed for AcLDL, SREC-II ectodomain interacted strongly with MalBSA and bound with high affinity to AcBSA, a property shared with the SR-F1 ectodomain. SREC-II ectodomain also interacted with two SR-F1 specific ligands, complement C1q and calreticulin, with affinities in the 100 nM range. We proceeded to generate a stable CHO cell line overexpressing full-length SREC-II; binding of MalBSA to these cells was significantly increased compared to non-transfected CHO cells. In contrast, no increase in binding could be detected for C1q and calreticulin. We show for the first time that SREC-II has the capacity to interact with the common scavenger receptor ligand MalBSA. In addition, our data highlight similarities and differences in the ligand binding properties of SREC-II in soluble form and at the cell surface, and show that endogenous protein ligands of the ectodomain of SREC-II, such as C1q and calreticulin, are shared with the corresponding domain of SR-F1.

The Glycosylphosphatidylinositol-Anchored Superoxide Dismutase of Scedosporium apiospermum Protects the Conidia from Oxidative Stress

Scedosporium species are common fungal pathogens in patients with cystic fibrosis (CF). To colonize the CF lungs, fungi must cope with the host immune response, especially the reactive oxygen species (ROS) released by phagocytic cells. To this aim, pathogens have developed various antioxidant systems, including superoxide dismutases (SODs) which constitute the first-line protection against oxidative stress. Interestingly, one of the S. apiospermum SOD-encoding genes (SODD gene) exhibits a glycosylphosphatidylinositol (GPI) anchor-binding site and encodes a conidial-specific surface SOD. In this study, a SODDΔ mutant was engineered from a non-homologous end joining-deficient strain (KU70Δ) of S. apiospermum. Compared to its parent strain, the double mutant KU70Δ/SODDΔ exhibited increased susceptibility to various oxidizing agents and triazole antifungals. In addition, the loss of SodD resulted in an increased intracellular killing of the conidia by M1 macrophages derived from human blood monocytes, suggesting the involvement of this superoxide dismutase in the evasion to the host defenses. Nevertheless, one cannot disregard an indirect role of the enzyme in the synthesis or assembly of the cell wall components since transmission electron microscopic analysis revealed a thickening of the inner cell wall layer of the conidia. Further studies are needed to confirm the role of this enzyme in the pathogenesis of Scedosporium infections, including the production of a recombinant protein and study of its protective effect against the infection in a mouse model of scedosporiosis.

Serum Interleukin-26 Is a New Biomarker for Disease Activity Assessment in Systemic Lupus Erythematosus

Objective

Interleukin-26 (IL-26) has a unique ability to activate innate immune cells due to its binding to circulating double-stranded DNA. High levels of IL-26 have been reported in patients with chronic inflammation. We aimed to investigate IL-26 levels in patients with systemic lupus erythematosus (SLE).

Methods

IL-26 serum levels were quantified by ELISA for 47 healthy controls and 109 SLE patients previously enrolled in the PLUS study. Performance of IL-26 levels and classical markers (autoantibodies or complement consumption) to identify an active SLE disease (SLE disease activity index (SLEDAI) score > 4) were compared.

Results

IL-26 levels were significantly higher in SLE patients than in controls (4.04 ± 11.66 and 0.74 ± 2.02 ng/mL; p = 0.005). IL-26 levels were also significantly higher in patients with active disease than those with inactive disease (33.08 ± 21.06 vs 1.10 ± 3.80 ng/mL, p < 0.0001). IL-26 levels correlated with SLEDAI score and the urine protein to creatinine ratio (uPCR) (p < 0.001). Patients with high IL-26 levels had higher SLEDAI score, anti-DNA antibodies levels, and uPCR (p < 0.05). They presented more frequently with C3 or C4 complement consumption. Lastly, IL-26 showed stronger performance than classical markers (complement consumption or autoantibodies) for active disease identification.

Conclusions

Our results suggest that, in addition to classical SLE serological markers, the measurement of IL-26 levels may be a useful biomarker for active disease identification in SLE patients.

Predicting Bone Regeneration with a Simple Blood Test

Cheng and colleagues reported previously unexplored correlations between circulating levels of immune cells and biomarkers and bone regeneration, which served as support for the construction of a model ensemble that can predict bone regeneration. If validated in humans, this tool could be valuable in the management of non-union fractures.

Involvement of the M-CSF/IL-34/CSF-1R pathway in malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer related to asbestos exposure. The tumor microenvironment content, particularly the presence of macrophages, was described as crucial for the development of the disease. This work aimed at studying the involvement of the M-CSF (CSF-1)/IL-34/CSF-1R pathway in the formation of macrophages in MPM, using samples from patients.

Methods

Pleural effusions (PEs), frozen tumors, primary MPM cells and MPM cell lines used in this study belong to biocollections associated with clinical databases. Cytokine expressions were studied using real-time PCR and ELISA. The Cancer Genome Atlas database was used to confirm our results on an independent cohort. An original three-dimensional (3D) coculture model including MPM cells, monocytes from healthy donors and a tumor antigen-specific cytotoxic CD8 T cell clone was used.

Results

We observed that high interleukin (IL)-34 levels in PE were significantly associated with a shorter survival of patients. In tumors, expression of CSF1 was correlated with ‘M2-like macrophages’ markers, whereas this was not the case with IL34 expression, suggesting two distinct modes of action of these cytokines. Expression of IL34 was higher in MPM cells compared with primary mesothelial cells. Particularly, high expression of IL34 was observed in MPM cells with an alteration of CDKN2A. Finally, using 3D coculture model, we demonstrated the direct involvement of MPM cells in the formation of immunosuppressive macrophages, through activation of the colony stimulating factor-1 receptor (CSF1-R) pathway, causing the inhibition of cytotoxicity of tumor antigen-specific CD8⁺ T cells.

Conclusions

The M-CSF/IL-34/CSF-1R pathway seems strongly implicated in MPM and could constitute a therapeutic target to act on immunosuppression and to support immunotherapeutic strategies.

Fungal Polysaccharides Promote Protective Immunity

Fungal pathogens represent a rising threat against immunocompromised patients. By using Aspergillus fumigatus, Briard et al. showed that the cell wall galactosaminogalactan (GAG) triggers macrophage inflammasome activation, promoting protective immunity. This provides new insights into the role of GAG in host-pathogen interactions and also perspectives for developing GAG-based anti-inflammatory therapeutics.

Anti-Pentraxin Antibodies in Autoimmune Diseases: Bystanders or Pathophysiological Actors?

Pentraxins are soluble innate immunity receptors involved in sensing danger molecules. They are classified as short (CRP, SAP) and long pentraxin subfamilies, including the prototypic long pentraxin PTX3. Pentraxins act mainly as bridging molecules favoring the clearance of microbes and dead cells. They are also involved in many other biological processes, such as regulation of complement activation, inflammation and tissue homeostasis. Autoantibodies directed against pentraxins have been reported in various autoimmune diseases, especially in systemic lupus erythematosus and ANCA-associated vasculitis. In this review, we review the main biological characteristics and functions of pentraxins and summarize data concerning autoantibodies directed against pentraxins in the context of autoimmune diseases and discuss their potential pathological role.

Macrophages: Checking Toxicity of Fungal Metabolites in the Colon

It is well known that the intestine absorbs nutrients, electrolytes, and water. Chikina et al. recently demonstrated that it is also able to sense, recognize, and block the absorption of toxins through a very sophisticated interactive cellular cooperation between novel subpopulations of macrophages and epithelial cells.

Mycolactone toxin induces an inflammatory response by targeting the IL-1β pathway: Mechanistic insight into Buruli ulcer pathophysiology

Mycolactone, a lipid-like toxin, is the major virulence factor of Mycobacterium ulcerans, the etiological agent of Buruli ulcer. Its involvement in lesion development has been widely described in early stages of the disease, through its cytotoxic and immunosuppressive activities, but less is known about later stages. Here, we revisit the role of mycolactone in disease outcome and provide the first demonstration of the pro-inflammatory potential of this toxin. We found that the mycolactone-containing mycobacterial extracellular vesicles produced by M. ulcerans induced the production of IL-1β, a potent pro-inflammatory cytokine, in a TLR2-dependent manner, targeting NLRP3/1 inflammasomes. We show our data to be relevant in a physiological context. The in vivo injection of these mycolactone-containing vesicles induced a strong local inflammatory response and tissue damage, which were prevented by corticosteroids. Finally, several soluble pro-inflammatory factors, including IL-1β, were detected in infected tissues from mice and Buruli ulcer patients. Our results revisit Buruli ulcer pathophysiology by providing new insight, thus paving the way for the development of new therapeutic strategies taking the pro-inflammatory potential of mycolactone into account.

Buruli ulcer is a neglected tropical disease occurring mainly in poor rural areas of West and Central Africa. This cutaneous disease is caused by Mycobacterium ulcerans, a bacterium belonging to the same family as M. tuberculosis and M. leprae. The skin lesions are caused by a cytotoxic toxin named mycolactone, also known to act as an immunosuppressor and an anti-inflammatory molecule. However, Buruli ulcer lesions are characterized by a chronic cutaneous inflammation with a recruitment of cellular immune cells trying to counteract M. ulcerans. Our work allows for a reconcilitation of previous observations. We found by in vitro experiment on macrophages that the mycolactone-containing mycobacterial extracellular vesicles produced by M. ulcerans induced the production of IL-1β, a potent pro-inflammatory molecule, while other pro-inflammatory soluble factors are inhibited. We also detected IL-1β protein in a mouse model of M. ulcerans infection as well as in biopsies of Buruli ulcer patients. The pro-inflammatory potential of mycolacone has to be taken into account to understand the full pathophysiology of Buruli ulcer.

Targeting Tumor Associated Macrophages to Overcome Conventional Treatment Resistance in Glioblastoma

Glioblastoma (GB) is the most common and devastating form of brain cancer. Despite conventional treatments, progression or recurrences are systematic. In recent years, immunotherapies have emerged as an effective treatment in a number of cancers, leaving the question of their usefulness also faced with the particular case of brain tumors. The challenge here is major not only because the brain is the seat of our consciousness but also because of its isolation by the blood-brain barrier and the presence of a unique microenvironment that constitutes the central nervous system (CNS) with very specific constituent or patrolling cells. Much of the microenvironment is made up of immune cells or inflammation. Among these, tumor-associated macrophages (TAMs) are of significant interest as they are often involved in facilitating tumor progression as well as the development of resistance to standard therapies. In this review, the ubiquity of TAMs in GB will be discussed while the specific case of microglia resident in the brain will be also emphasized. In addition, the roles of TAMs as accomplices in the progression of GB and resistance to treatment will be presented. Finally, clinical trials targeting TAMs as a means of treating cancer will be discussed.

Molecular and Cellular Interactions of Scavenger Receptor SR-F1 With Complement C1q Provide Insights Into Its Role in the Clearance of Apoptotic Cells

The scavenger receptor SR-F1 binds to and mediates the internalization of a wide range of ligands, and is involved in several immunological processes. We produced recombinant SR-F1 ectodomain and fragments deleted from the last 2 or 5 C-terminal epidermal growth factor-like modules and investigated their role in the binding of acetylated low density lipoprotein (AcLDL), complement C1q, and calreticulin (CRT). C1q measured affinity was in the 100 nM range and C1q interaction occurs via its collagen-like region. We identified two different binding regions on SR-F1: the N-terminal moiety interacts with C1q and CRT whereas the C-terminal moiety binds AcLDL. The role of SR-F1 N-linked glycans was also tested by mutating each of the three glycosylated asparagines. The three mutants retained binding activities for both AcLDL and C1q. A stable THP-1 cell line overexpressing SR-F1 was generated and C1q was shown to bind more strongly to the surface of SR-F1 overexpressing macrophages, with C1q/SR-F1 colocalization observed in some membrane areas. We also observed a higher level of CRT internalization for THP-1 SR-F1 cells. Increasing SR-F1 negatively modulated the uptake of apoptotic cells. Indeed, THP-1 cells overexpressing SR-F1 displayed a lower phagocytic capacity as compared with mock-transfected cells, which could be partially restored by addition of C1q in the extracellular milieu. Our data shed some light on the role of SR-F1 in efferocytosis, through its capacity to bind C1q and CRT, two proteins involved in this process.

Skin-specific antibodies neutralizing mycolactone toxin during the spontaneous healing of Mycobacterium ulcerans infection

Buruli ulcer, a neglected tropical infectious disease, is caused by Mycobacterium ulcerans. Without treatment, its lesions can progress to chronic skin ulcers, but spontaneous healing is observed in 5% of cases, suggesting the possible establishment of a host strategy counteracting the effects of M. ulcerans. We reveal here a skin-specific local humoral signature of the spontaneous healing process, associated with a rise in antibody-producing cells and specific recognition of mycolactone by the mouse IgG2a immunoglobulin subclass. We demonstrate the production of skin-specific antibodies neutralizing the immunomodulatory activity of the mycolactone toxin, and confirm the role of human host machinery in triggering effective local immune responses by the detection of anti-mycolactone antibodies in patients with Buruli ulcer. Our findings pave the way for substantial advances in both the diagnosis and treatment of Buruli ulcer in accordance with the most recent challenges issued by the World Health Organization.

Lactic Acidosis Together with GM-CSF and M-CSF Induces Human Macrophages toward an Inflammatory Protumor Phenotype

In established tumors, tumor-associated macrophages (TAM) orchestrate nonresolving cancer-related inflammation and produce mediators favoring tumor growth, metastasis, and angiogenesis. However, the factors conferring inflammatory and protumor properties on human macrophages remain largely unknown. Most solid tumors have high lactate content. We therefore analyzed the impact of lactate on human monocyte differentiation. We report that prolonged lactic acidosis induces the differentiation of monocytes into macrophages with a phenotype including protumor and inflammatory characteristics. These cells produce tumor growth factors, inflammatory cytokines, and chemokines as well as low amounts of IL10. These effects of lactate require its metabolism and are associated with hypoxia-inducible factor-1α stabilization. The expression of some lactate-induced genes is dependent on autocrine M-CSF consumption. Finally, TAMs with protumor and inflammatory characteristics (VEGF^high CXCL8⁺ IL1β⁺) are found in solid ovarian tumors. These results show that tumor-derived lactate links the protumor features of TAMs with their inflammatory properties. Treatments that reduce tumor glycolysis or tumor-associated acidosis may help combat cancer.

Quantitative chimerism in CD3-negative mononuclear cells predicts prognosis in acute myeloid leukemia patients after hematopoietic stem cell transplantation

Relapse is a major complication of acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (SCT). The objective of our study was to evaluate chimerism monitoring on the CD3-negative mononuclear cells by RQ-PCR to predict relapse of patients allografted for AML and to compare its performance with WT1 quantification. A cohort of 100 patients undergoing allogenic SCT for AML was retrospectively analyzed in a single institution. Patients without complete chimerism, defined as less than 0.01% of recipient's DNA in CD3-negative cells, had a significantly higher risk of relapse and a lower overall survival (p < 0.001). An increase in the percentage of recipient DNA in CD3-negative cells was associated with an increased risk of relapse (p < 0.001) but not with overall survival. Comparable performances between monitoring of CD3-negative cell chimerism and WT1 expression to predict relapse was observed up to more than 90 days before hematological relapse, with sensitivity of 82% and 78%, respectively, and specificity of 100% for both approaches. Quantitative specific chimerism of the CD3-negative mononuclear fraction, enriched in blastic cells, is a new and powerful tool for monitoring measurable residual disease and could be used for AML patients without available molecular markers.

Transcriptional profiling of Scedosporium apiospermum enzymatic antioxidant gene battery unravels the involvement of thioredoxin reductases against chemical and phagocytic cells oxidative stress

Scedosporium species rank the second, after Aspergillus fumigatus, among the filamentous fungi colonizing the airways of patients with cystic fibrosis (CF). Development of microorganisms in the respiratory tract depends on their capacity to evade killing by the host immune system, particularly through the oxidative response of macrophages and neutrophils, with the release of reactive oxygen species (ROS) and reactive nitrogen species (RNS). This is particularly true in the airways of CF patients which display an exacerbated inflammatory reaction. To protect themselves, pathogens have developed various enzymatic antioxidant systems implicated in ROS degradation, including superoxide dismutases, catalases, cytochrome C peroxidases, chloroperoxidases and enzymes of the glutathione and thioredoxin systems, or in RNS degradation, that is, flavohemoglobins, nitrate reductases, and nitrite reductases. Here we investigated the transcriptional regulation of the enzymatic antioxidant gene battery in 24-h-old hyphae of Scedosporium apiospermum in response to oxidative stress induced chemically or by exposure to activated phagocytic cells. We showed that 21 out of the 33 genes potentially implicated in the oxidative or nitrosative stress response were overexpressed upon exposure of the fungus to various chemical oxidants, while they were only 13 in co-cultures with macrophages or neutrophils. Among them, genes encoding two thioredoxin reductases and to a lesser extent, a peroxiredoxin and one catalase were found to be overexpressed after chemical oxidative stress as well as in co-cultures. These results suggest that thioredoxin reductases, which are known to be virulence factors in other pathogenic fungi, play a key role in pathogenesis of scedosporiosis, and may be new drug targets.

Pre-transplant CD45RC expression on blood T cells differentiates patients with cancer and rejection after kidney transplantation

Background

Biological biomarkers to stratify cancer risk before kidney transplantation are lacking. Several data support that tumor development and growth is associated with a tolerant immune profile. T cells expressing low levels of CD45RC preferentially secrete regulatory cytokines and contain regulatory T cell subset. In contrast, T cells expressing high levels of CD45RC have been shown to secrete proinflammatory cytokines, to drive alloreactivity and to predict acute rejection (AR) in kidney transplant patients. In the present work, we evaluated whether pre-transplant CD45RC^low T cell subset was predictive of post-transplant cancer occurrence.

Methods

We performed an observational cohort study of 89 consecutive first time kidney transplant patients whose CD45RC T cell expression was determined by flow cytometry before transplantation. Post-transplant events including cancer, AR, and death were assessed retrospectively.

Results

After a mean follow-up of 11.1±4.1 years, cancer occurred in 25 patients (28.1%) and was associated with a decreased pre-transplant proportion of CD4⁺CD45RC^high T cells, with a frequency below 51.9% conferring a 3.7-fold increased risk of post-transplant malignancy (HR 3.71 [1.24–11.1], p = 0.019). The sensibility, specificity, negative predictive and positive predictive values of CD4⁺CD45RC^high<51.9% were 84.0, 54.7, 89.8 and 42.0% respectively. Confirming our previous results, frequency of CD8⁺CD45RC^high T cells above 52.1% was associated with AR, conferring a 20-fold increased risk (HR 21.7 [2.67–176.2], p = 0.0004). The sensibility, specificity, negative predictive and positive predictive values of CD8⁺CD45RC^high>52.1% were 94.5, 68.0, 34.7 and 98.6% respectively. Frequency of CD4⁺CD45RC^high T cells was positively correlated with those of CD8⁺CD45RC^high (p<0.0001), suggesting that recipients with high AR risk display a low cancer risk.

Conclusion

High frequency of CD45RC^high T cells was associated with AR, while low frequency was associated with cancer. Thus, CD45RC expression on T cells appears as a double-edged sword biomarker of promising interest to assess both cancer and AR risk before kidney transplantation.

IL-26, a Cytokine With Roles in Extracellular DNA-Induced Inflammation and Microbial Defense

Interleukin 26 (IL-26) is the most recently identified member of the IL-20 cytokine subfamily, and is a novel mediator of inflammation overexpressed in activated or transformed T cells. Novel properties have recently been assigned to IL-26, owing to its non-conventional cationic, and amphipathic features. IL-26 binds to DNA released from damaged cells and, as a carrier molecule for extracellular DNA, links DNA to inflammation. This observation suggests that IL-26 may act both as a driver and an effector of inflammation, leading to the establishment of a deleterious amplification loop and, ultimately, sustained inflammation. Thus, IL-26 emerges as an important mediator in local immunity/inflammation. The dysregulated expression and extracellular DNA carrier capacity of IL-26 may have profound consequences for the chronicity of inflammation. IL-26 also exhibits direct antimicrobial properties. This review summarizes recent advances on the biology of IL-26 and discusses its roles as a novel kinocidin.

The roles of CSFs on the functional polarization of tumor-associated macrophages

Macrophages have a central role in numerous physiological processes, such as immune defense, maintenance of tissue homeostasis, wound healing, and inflammation. Moreover, in numerous severe disorders, such as cancer or chronic inflammation, their functions can be profoundly affected. Macrophages continuously sense their environment and adapt their phenotypes and functions to the local requirements; this process is called plasticity. In addition to stress signals, metabolites, and direct cell-contact interactions with surrounding cells, numerous cytokines play a central role in controlling macrophage polarization. In this review, we will focus on three human macrophage differentiation factors: macrophage colony-stimulating factor (M-CSF), IL-34, and granulocyte M-CSF. These CSFs allow human monocyte survival, promote their differentiation into macrophages, and control macrophage polarization as they give rise to cells with different phenotype and functions. Based on recent observations, the role of granulocyte CSF on macrophage polarization is also addressed. Finally, our current knowledge on the expression of these growth factors in tumor microenvironment and their impact on the generation and polarization of tumor-associated macrophages are summarized.

Loss of vascular expression of nucleoside triphosphate diphosphohydrolase-1/CD39 in hypertension

Ectonucleoside triphosphate diphosphohydrolase-1, the major vascular/immune ectonucleotidase, exerts anti-thrombotic and immunomodulatory actions by hydrolyzing extracellular nucleotides (danger signals). Hypertension is characterized by vascular wall remodeling, endothelial dysfunction, and immune infiltration. Here our aim was to investigate the impact of arterial hypertension on CD39 expression and activity in mice. Arterial expression of CD39 was determined by reverse transcription quantitative real-time PCR in experimental models of hypertension, including angiotensin II (AngII)-treated mice (1 mg/kg/day, 21 days), deoxycorticosterone acetate-salt mice (1% salt and uninephrectomy, 21 days), and spontaneously hypertensive rats. A decrease in CD39 expression occurred in the resistance and conductance arteries of hypertensive animals with no effect on lymphoid organs. In AngII-treated mice, a decrease in CD39 protein levels (Western blot) was corroborated by reduced arterial nucleotidase activity, as evaluated by fluorescent (etheno)-ADP hydrolysis. Moreover, serum-soluble ADPase activity, supported by CD39, was significantly decreased in AngII-treated mice. Experiments were conducted in vitro on vascular cells to determine the elements underlying this downregulation. We found that CD39 transcription was reduced by proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor alpha on vascular smooth muscle cells and by IL-6 and anti-inflammatory and profibrotic cytokine transforming growth factor beta 1 on endothelial cells. In addition, CD39 expression was downregulated by mechanical stretch on vascular cells. Arterial expression and activity of CD39 were decreased in hypertension as a result of both a proinflammatory environment and mechanical strain exerted on vascular cells. Reduced ectonucleotidase activity may alter the vascular condition, thus enhancing arterial damage, remodeling, or thrombotic events.

CD40L confers helper functions to human intra-melanoma class-I-restricted CD4+CD8+ double positive T cells

Although CD4⁺CD8⁺ double positive (DP) T cells represent a small fraction of peripheral T lymphocytes in healthy human donors, their frequency is often increased under pathological conditions (in blood and targeted tissues). In solid cancers such as melanoma, we previously demonstrated an enrichment of tumor reactive CD4^lowCD8^highαβ DP T cells among tumor-infiltrating lymphocytes of unknown function. Similarly to their single positive (SP) CD8⁺ counterparts, intra-melanoma DP T cells recognized melanoma cell lines in an HLA-class-I restricted context. However, they presented a poor cytotoxic activity but a strong production of diverse Th1 and Th2 cytokines. The aim of this study was to clearly define the role of intra-melanoma CD4^lowCD8^highαβ DP T cells in the antitumor immune response. Based on a comparative transcriptome analysis between intra-melanoma SP CD4⁺, SP CD8⁺ and DP autologous melanoma-infiltrating T-cell compartments, we evidenced an overexpression of the CD40L co-stimulatory molecule on activated DP T cells. We showed that, like SP CD4⁺ T cells, and through CD40L involvement, DP T cells are able to induce both proliferation and differentiation of B lymphocytes and maturation of functional DCs able to efficiently prime cytotoxic melanoma-specific CD8 T-cell responses. Taken together, these results highlight the helper potential of atypical DP T cells and their role in potentiating antitumor response.

Pleural Effusions from Patients with Mesothelioma Induce Recruitment of Monocytes and Their Differentiation into M2 Macrophages

INTRODUCTION

Mesothelioma is a rare and aggressive cancer related to asbestos exposure. We recently showed that pleural effusions (PEs) from patients with mesothelioma contain high levels of the C-C motif chemokine ligand 2 (CCL2) inflammatory chemokine. In the present work, we studied the effect of CCL2 contained in mesothelioma samples, particularly on monocyte recruitment. Then, we studied the fate of these monocytes in malignant pleural mesothelioma (MPM) PEs and their impact on tumor cells' properties.

METHODS

The implication of CCL2 in monocyte recruitment was evaluated using transmigration assays and a CCL2 blocking antibody. The phenotype of macrophages was determined by flow cytometry and enzyme-linked immunosorbent assay. Immunohistochemical analysis was used to support the results. Cocultures of macrophages with mesothelioma cells were performed to study cancer cell proliferation and resistance to treatment.

RESULTS

We showed that CCL2 is a major factor of monocyte recruitment induced by MPM samples. Macrophages obtained in MPM samples were M2 macrophages (high CD14, high CD163, and interleukin-10 secretion after activation). The colony-stimulating factor 1 receptor/macrophage colony-stimulating factor (M-CSF) pathway is implicated in M2 polarization, and high levels of M-CSF were measured in MPM samples compared with benign PE (4.17 ± 2.75 ng/mL and 1.94 ± 1.47 ng/mL, respectively). Immunohistochemical analysis confirmed the presence of M2 macrophages in pleural and peritoneal mesothelioma. Finally, we showed that M2 macrophages increased mesothelioma cell proliferation and resistance to treatment.

CONCLUSIONS

These results demonstrate the implication of CCL2 in MPM pathogenesis and designate M-CSF as a new potential biomarker of MPM. This study also identifies CCL2 and colony-stimulating factor 1 receptor/M-CSF as interesting new targets to modulate pro-tumorigenic properties of the tumor microenvironment.

The angiotensin II type 2 receptor activates flow-mediated outward remodelling through T cells-dependent interleukin-17 production

AIMS

The angiotensin II type 1 receptor (AT1R) through the activation of immune cells plays a key role in arterial inward remodelling and reduced blood flow in cardiovascular disorders. On the other side, flow (shear stress)-mediated outward remodelling (FMR), involved in collateral arteries growth in ischaemic diseases, allows revascularization. We hypothesized that the type 2 receptor (AT2R), described as opposing the effects of AT1R, could be involved in FMR.

METHODS AND RESULTS

We studied FMR using a model of ligation of feed arteries supplying collateral pathways in the mouse mesenteric arterial bed in vivo. Seven days after ligation, diameter increased by 30% in high flow (HF) arteries compared with normal flow vessels. FMR was absent in mice lacking AT2R. At Day 2, T lymphocytes expressing AT2R were present preferentially around HF arteries. FMR did not occur in athymic (nude) mice lacking T cells and in mice treated with anti-CD3ε antibodies. AT2R activation induced interleukin-17 production by memory T cells. Treatment of nude mice or AT2R-deficient mice with interleukin-17 restored diameter enlargement in HF arteries. Interleukin-17 increased NO-dependent relaxation and matrix metalloproteinases activity, both important in FMR. Remodelling of feeding arteries in the skin flap model of ischaemia was also absent in AT2R-deficient mice and in anti-interleukin-17-treated mice. Finally, remodelling, absent in 12-month-old mice, was restored by a treatment with the AT2R non-peptidic agonist C21.

CONCLUSION

AT2R-dependent interleukin-17 production by T lymphocyte is necessary for collateral artery growth and could represent a new therapeutic target in ischaemic disorders.

The ecto-ATPDase CD39 is involved in the acquisition of the immunoregulatory phenotype by M-CSF-macrophages and ovarian cancer tumor-associated macrophages: Regulatory role of IL-27

Tumor-associated macrophages (TAM) are immunosuppressive cells that can massively accumulate in the tumor microenvironment. In patients with ovarian cancer, their density is correlated with poor prognosis. Targeting mediators that control the generation or the differentiation of immunoregulatory macrophages represents a therapeutic challenge to overcome tumor-associated immunosuppression. The ectonucleotidase CD39 hydrolyzes ATP into extracellular adenosine that exhibits potent immunosuppressive properties when signaling through the A2A adenosine receptor. We report here that CD14(+) CD163(+) TAM isolated from ovarian cancer patients and macrophages generated in vitro with M-CSF, express high levels of the membrane ectonucleotidase CD39 compared to classically activated macrophages. The CD39 inhibitor POM-1 and adenosine deaminase (ADA) diminished some of the immunosuppressive functions of CD14(high) CD163(high) CD39(high) macrophages, such as IL-10 secretion. We identified the cytokine IL-27, secreted by tumor-infiltrating neutrophils, located close to infiltrating CD163(+) macrophages, as a major rheostat of CD39 expression and consequently, on the acquisition of immunoregulatory properties by macrophages. Accordingly, the depletion of IL-27 downregulated CD39 and PD-L1 expression as well as IL-10 secretion by M-CSF-macrophages. Collectively, these data suggest that CD39, drived by IL-27 and CD115 ligands in ovarian cancer, maintains the immunosuppressive phenotype of TAM. This work brings new information on the acquisition of immunosuppressive properties by tumor-infiltrating macrophages.

Clinical Features of Spontaneous Partial Healing During Mycobacterium ulcerans Infection

Background.  Buruli ulcer, caused by Mycobacterium ulcerans, is a necrotizing skin disease leading to extensive cutaneous and subcutaneous destruction and functional limitations. Spontaneous healing in the absence of medical treatment occurs in rare cases, but this has not been well described in the literature. Methods.  In a retrospective case study in an area of Benin where this disease is highly endemic, we selected 26 Buruli ulcer patients presenting features of spontaneous healing from a cohort of 545 Buruli ulcer patients treated between 2010 and 2013. Results.  The 26 patients studied had a median age of 13.5 years and were predominantly male (1.4:1). Three groups of patients were defined on the basis of their spontaneous healing characteristics. The first group (12 patients) consisted of patients with an ulcer of more than 1 year's duration showing signs of healing. The second (13 patients) group contained patients with an active Buruli ulcer lesion some distance away from a first lesion that had healed spontaneously. Finally, the third group contained a single patient displaying complete healing of lesions from a nodule, without treatment and with no relapse. Conclusions.  We defined several features of spontaneous healing in Buruli ulcer patients and highlighted the difficulties associated with diagnosis and medical management. Delays in consultation contributed to the high proportion of patients with permanent sequelae and a risk of squamous cell carcinoma. Early detection and antibiotic treatment are the best ways to reduce impairments.

Detection of Anti-Pentraxin-3 Autoantibodies in ANCA-Associated Vasculitis

OBJECTIVES

Pentraxin 3 (PTX3), in common with myeloperoxidase and proteinase 3, is stored in human neutrophil granules and is expressed on apoptotic neutrophil surface. We therefore investigated the presence of anti-PTX3 autoantibodies (aAbs) in the sera of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) patients.

METHODS

Presence of anti-PTX3 autoantibodies was analysed by a specific enzyme-linked immunosorbent assay in sera from 150 patients with microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA), and in sera of 227 healthy subjects (HS), 40 systemic sclerosis (SSc) patients, and 25 giant cell arteritis patients (GCA). Using indirect immunofluorescence on fixed human neutrophils, we also analyzed the staining pattern associated with the presence of anti-PTX3 aAbs.

RESULTS

Anti-PTX3 aAbs were detected in 56 of 150 (37.3%) of the AAV patients (versus 12 of 227 (5.3%) of HS, p<0.001) and, interestingly, in 7 of 14 MPO and PR3 ANCA negative AAV patients. Moreover, by indirect immunofluorescence on fixed neutrophils, anti-PTX3 aAbs gave rise to a specific cytoplasmic fluorescence pattern distinct from the classical cytoplasmic (c-ANCA), perinuclear (p-ANCA), and atypical (a-ANCA) pattern. Anti-PTX3 aAbs levels were higher in patients with active AAV as compared to patients with inactive disease.

CONCLUSION

Our work suggests that PTX3 is as a novel ANCA antigen. Anti-PTX3 aAbs appear thus as a promising novel biomarker in the diagnosis of AAV, including in patients without detectable MPO and PR3 ANCA.

A staggered decameric assembly of human C-reactive protein stabilized by zinc ions revealed by X-ray crystallography

Human C-reactive protein (CRP) is an acute phase protein, which harbours both host defence and scavenging properties. In this study, we obtained two new crystal forms of CRP, where CRP forms a symmetric, staggered dimer of pentamers. In one of these structures, obtained in the presence of HIV-1 Tat protein, this dimer of pentamers is stabilized by two zinc ions trapped within a cleft of the effector face of CRP. These two decameric interfaces involve complementary surfaces of CRP pentamers and bury a large area of ~2000 Å(2) per pentamer, suggesting a biological role of this interface. These two novel decameric interfaces and the involvement of zinc might have important consequences in the understanding of CRP biological functions.

Identification of Scedosporium boydii catalase A1 gene, a reactive oxygen species detoxification factor highly expressed in response to oxidative stress and phagocytic cells

Scedosporium boydii is an opportunistic filamentous fungus which may be responsible for a large variety of infections in both immunocompetent and immunocompromised individuals. This fungus belongs to the Scedosporium apiospermum species complex which usually ranks second among the filamentous fungi colonizing the airways of patients with cystic fibrosis (CF). Species of the S. apiospermum complex are able to chronically colonize the CF airways suggesting pathogenic mechanisms allowing persistence and growth of these fungi in the respiratory tract. Few putative virulence factors have been purified and characterized so far in the S. apiospermum complex including a cytosolic Cu,Zn-superoxide dismutase (SOD) and a monofunctional catalase (catalase A1). Upon microbial infection, host phagocytes release reactive oxygen species (ROS), such as hydrogen peroxide, as part of the antimicrobial response. Catalases are known to protect pathogens against ROS by degradation of the hydrogen peroxide. Here, we identified the S. boydii catalase A1 gene (CATA1) and investigated its expression in response to the environmental conditions encountered in the CF airways and to the oxidative stress. Results showed that S. boydii CATA1 gene expression is not affected by hypoxia, hypercapnia or pH changes. In contrast, CATA1 gene was overexpressed in response to a chemically induced oxidative stress with a relative gene expression 37-fold higher in the presence of 250 μM H(2)O(2), 20-fold higher with 250 μM menadione and 5-fold higher with 2 mM paraquat. Moreover, S. boydii CATA1 gene expression progressively increased upon exposure to activated THP-1-derived macrophages, reaching a maximum after 12 h (26 fold). Activated HL60-derived neutrophils and activated human peripheral blood neutrophils more rapidly induced S. boydii CATA1 gene overexpression, a maximum gene expression level being reached at 75 min (17 fold) and 60 min (15 fold), respectively. In contrast expression of the gene encoding the Cu,Zn-SOD (SODC gene) was not affected by H(2)O(2), menadione, paraquat or in co-culture with phagocytic cells. These results suggest that S. boydii CATA1 gene is highly stimulated by the oxidative burst response whereas SODC gene is constitutively expressed.

IL-26 is overexpressed in chronically HCV-infected patients and enhances TRAIL-mediated cytotoxicity and interferon production by human NK cells

OBJECTIVE

Interleukin-26 (IL-26) is a member of the IL-10 cytokine family, first discovered based on its peculiar expression by virus-transformed T cells. IL-26 is overexpressed in chronic inflammation (rheumatoid arthritis and Crohn's disease) and induces proinflammatory cytokines by myeloid cells and some epithelial cells. We thus investigated the expression and potential role of IL-26 in chronic HCV infection, a pathology associated with chronic inflammation.

DESIGN

IL-26 was quantified in a cohort of chronically HCV-infected patients, naive of treatment and its expression in the liver biopsies investigated by immunohistochemistry. We also analysed the ability of IL-26 to modulate the activity of natural killer (NK) cells, which control HCV infection.

RESULTS

The serum levels of IL-26 are enhanced in chronically HCV-infected patients, mainly in those with severe liver inflammation. Immunohistochemistry reveals an intense IL-26 staining in liver lesions, mainly in infiltrating CD3+ cells. We also show that NK cells from healthy subjects and from HCV-infected patients are sensitive to IL-26. IL-26 upregulates membrane tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) expression on CD16- CD56(bright) NK cells, enabling them to kill HCV-infected hepatoma cells, with the same efficacy as interferon (IFN)-α-treated NK cells. IL-26 also induces the expression of the antiviral cytokines IFN-β and IFN-γ, and of the proinflammatory cytokines IL-1β and TNF-α by NK cells.

CONCLUSIONS

This study highlights IL-26 as a new player in the inflammatory and antiviral immune responses associated with chronic HCV infection.

IL-34- and M-CSF-induced macrophages switch memory T cells into Th17 cells via membrane IL-1α

Macrophages orchestrate the immune response via the polarization of CD4(+) T helper (Th) cells. Different subsets of macrophages with distinct phenotypes, and sometimes opposite functions, have been described. M-CSF and IL-34 induce the differentiation of monocytes into IL-10(high) IL-12(low) immunoregulatory macrophages, which are similar to tumor-associated macrophages (TAMs) in ovarian cancer. In this study, we evaluated the capacity of human macrophages induced in the presence of M-CSF (M-CSF macrophages) or IL-34 (IL-34 macrophages) and ovarian cancer TAMs to modulate the phenotype of human CD4(+) T cells. Taken together, our results show that M-CSF-, IL-34 macrophages, and TAMs switch non-Th17 committed memory CD4(+) T cells into conventional CCR4(+) CCR6(+) CD161(+) Th17 cells, expressing or not IFN-gamma. Contrary, the pro-inflammatory GM-CSF macrophages promote Th1 cells. The polarization of memory T cells into Th17 cells is mediated via membrane IL-1α (mIL-1α), which is constitutively expressed by M-CSF-, IL-34 macrophages, and TAMs. This study elucidates a new mechanism that allows macrophages to maintain locally restrained and smoldering inflammation, which is required in angiogenesis and metastasis.

IL-34 and macrophage colony-stimulating factor are overexpressed in hepatitis C virus fibrosis and induce profibrotic macrophages that promote collagen synthesis by hepatic stellate cells

Chronic hepatitis C virus (HCV) infection is characterized by progressive hepatic fibrosis, a process dependent on monocyte recruitment and accumulation into the liver. The mediators expressed in chronically injured liver that control the differentiation of human monocytes into profibrotic macrophages (Mφ) remain poorly defined. We report that chronically HCV-infected patients with high fibrosis stages have higher serum levels of macrophage colony-stimulating factor (M-CSF) and interleukin (IL)-34 than HCV-infected patients with lower fibrosis stages and healthy subjects. Immunohistochemistry reveals an intense expression of IL-34 and M-CSF by hepatocytes around liver lesions. In addition, HCV infection and inflammatory cytokines enhance the in vitro production of IL-34 and M-CSF by hepatocytes. We next analyzed the acquisition of profibrotic properties by Mφ generated with M-CSF (M-CSF-Mφ) or IL-34 (IL-34-Mφ). M-CSF and IL-34 up-regulate the expression, by differentiating monocytes, of chemokine (C-C motif) ligand (CCL)2, CCL4, C-C chemokine receptor (CCR)1, and CCR5, which are involved in monocyte recruitment/Mφ accumulation in liver lesions. M-CSF-Mφ and IL-34-Mφ also express the hepatic stellate cell (HSC) activators, platelet-derived growth factor, transforming growth factor beta, and galectin-3. IL-34-Mφ and M-CSF-Mφ induce type I collagen synthesis by HSCs, the main collagen-producing cells in liver fibrosis. IL-13, whose expression correlates with the fibrosis stage in HCV-infected patients, decreases the expression of the collagenase, matrix metalloproteinase 1, by IL-34-Mφ and M-CSF-Mφ, thereby enhancing collagen synthesis. By inhibiting the production of interferon-gamma (IFN-γ) by activated natural killer cells, IL-34-Mφ and M-CSF-Mφ prevent the IFN-γ-induced killing of HSCs.

CONCLUSION

These results identify M-CSF and IL-34 as potent profibrotic factors in HCV liver fibrosis.

Evaluation of the therapeutic potential of bone marrow-derived myeloid suppressor cell (MDSC) adoptive transfer in mouse models of autoimmunity and allograft rejection

Therapeutic use of immunoregulatory cells represents a promising approach for the treatment of uncontrolled immunity. During the last decade, myeloid-derived suppressor cells (MDSC) have emerged as novel key regulatory players in the context of tumor growth, inflammation, transplantation or autoimmunity. Recently, MDSC have been successfully generated in vitro from naive mouse bone marrow cells or healthy human PBMCs using minimal cytokine combinations. In this study, we aimed to evaluate the potential of adoptive transfer of such cells to control auto- and allo-immunity in the mouse. Culture of bone marrow cells with GM-CSF and IL-6 consistently yielded a majority of CD11b⁺Gr1^hi/lo cells exhibiting strong inhibition of CD8⁺ T cell proliferation in vitro. However, adoptive transfer of these cells failed to alter antigen-specific CD8⁺ T cell proliferation and cytotoxicity in vivo. Furthermore, MDSC could not prevent the development of autoimmunity in a stringent model of type 1 diabetes. Rather, loading the cells prior to injection with a pancreatic neo-antigen peptide accelerated the development of the disease. Contrastingly, in a model of skin transplantation, repeated injection of MDSC or single injection of LPS-activated MDSC resulted in a significant prolongation of allograft survival. The beneficial effect of MDSC infusions on skin graft survival was paradoxically not explained by a decrease of donor-specific T cell response but associated with a systemic over-activation of T cells and antigen presenting cells, prominently in the spleen. Taken together, our results indicate that in vitro generated MDSC bear therapeutic potential but will require additional in vitro factors or adjunct immunosuppressive treatments to achieve safe and more robust immunomodulation upon adoptive transfer.

Abstract 238: Interleukin 17 Production Induced by Angiotensin Ii Type 2 Receptor Activation in T Cells Drives Flow-mediated Outward Remodeling of Mouse Resistance Arteries

Objective: Flow (shear stress)-mediated outward remodeling of resistance arteries is involved in collateral growth during postischemic revascularization. Besides the NO pathway the involvement of inflammatory factors and reactive oxygen species has been suggested in this remodeling although the mechanism and the sequence remains unknown. As T cells drive the inflammatory response, we investigated their role in flow-mediated remodeling. Mouse mesenteric resistance arteries (250μm internal diameter) were submitted in vivo to a chronic increase (144±18 to 239±25 μl/min) in blood flow. Arteries were collected for in vitro analysis after 1 to 7 days.

Results: After 1 week, remodeling occurred in high flow (HF) arteries (diameter increased from 242±21μm to 324±20μm, n=9 per group, P<00.1) in control mice. No remodeling occurred in nude mice and in mice treated with anti-CD3 antibodies. In control arteries lymphocyte T cells accumulate around HF arteries at day 1 (shown using both immunohistology and flow cytometry) and they expressed angiotensin II type 2 receptor (AT2R). In isolated T cells AT2R stimulation induced preferentially IL-17 production (20±6pg/ml to 50±5pg/ml, n=7 per group, P<00.1). We then tested the occurrence of remodeling in mice lacking AT2R or IL-17. In both AT2R-/- and IL-17-/- mice diameter expansion did not occur whereas T cells and myeloid cells accumulation around the HF artery was not affected. IL-17 infusion (5ng/h, Alzet osmotic minipump) to nude mice and to AT2R-/- mice restored HF remodeling to control level. In order to confirm the role of AT2R in flow-mediated remodeling in another vascular territory, neovascularization was examined using an ischemic skin flap model in AT2R-/- mice. As in mesenteric arteries, the absence of AT2R prevented diameter expansion in the arteries feeding the skin flap.

Conclusion: we demonstrate for the first time the involvement of lymphocytes T cells polarization into TH17 by angiotensin II type 2 receptor in flow-mediated outward remodeling of resistance arteries.