Regulatory myeloid suppressor cells in health and disease

The Role of Myeloid-Derived Suppressor Cells in Multiple Sclerosis and Its Animal Model

Myeloid-derived suppressor cells (MDSCs), a heterogeneous cell population that consists of mostly immature myeloid cells, are immunoregulatory cells mainly characterized by their suppressive functions. Emerging findings have revealed the involvement of MDSCs in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). MS is an autoimmune and degenerative disease of the central nervous system characterized by demyelination, axon loss, and inflammation. Studies have reported accumulation of MDSCs in inflamed tissues and lymphoid organs of MS patients and EAE mice, and these cells display dual functions in EAE. However, the contribution of MDSCs to MS/EAE pathogenesis remains unclear. This review aims to summarize our current understanding of MDSC subsets and their possible roles in MS/EAE pathogenesis. We also discuss the potential utility and associated obstacles in employing MDSCs as biomarkers and cell-based therapies for MS.

Objective Activity Parameters Track Patient-specific Physical Recovery Trajectories After Surgery and Link With Individual Preoperative Immune States

OBJECTIVE

The longitudinal assessment of physical function with high temporal resolution at a scalable and objective level in patients recovering from surgery is highly desirable to understand the biological and clinical factors that drive the clinical outcome. However, physical recovery from surgery itself remains poorly defined and the utility of wearable technologies to study recovery after surgery has not been established.

BACKGROUND

Prolonged postoperative recovery is often associated with long-lasting impairment of physical, mental, and social functions. Although phenotypical and clinical patient characteristics account for some variation of individual recovery trajectories, biological differences likely play a major role. Specifically, patient-specific immune states have been linked to prolonged physical impairment after surgery. However, current methods of quantifying physical recovery lack patient specificity and objectivity.

METHODS

Here, a combined high-fidelity accelerometry and state-of-the-art deep immune profiling approach was studied in patients undergoing major joint replacement surgery. The aim was to determine whether objective physical parameters derived from accelerometry data can accurately track patient-specific physical recovery profiles (suggestive of a 'clock of postoperative recovery'), compare the performance of derived parameters with benchmark metrics including step count, and link individual recovery profiles with patients' preoperative immune state.

RESULTS

The results of our models indicate that patient-specific temporal patterns of physical function can be derived with a precision superior to benchmark metrics. Notably, 6 distinct domains of physical function and sleep are identified to represent the objective temporal patterns: ''activity capacity'' and ''moderate and overall activity (declined immediately after surgery); ''sleep disruption and sedentary activity (increased after surgery); ''overall sleep'', ''sleep onset'', and ''light activity'' (no clear changes were observed after surgery). These patterns can be linked to individual patients preopera-tive immune state using cross-validated canonical-correlation analysis. Importantly, the pSTAT3 signal activity in monocytic myeloid-derived suppressor cells predicted a slower recovery.

CONCLUSIONS

Accelerometry-based recovery trajectories are scalable and objective outcomes to study patient-specific factors that drive physical recovery.

Endoplasmic reticulum stress mediates the myeloid-derived immune suppression associated with cancer and infectious disease

Myeloid-derived suppressor cells (MDSCs), which are immature heterogeneous bone marrow cells, have been described as potent immune regulators in human and murine cancer models. The distribution of MDSCs varies across organs and is divided into three subpopulations: granulocytic MDSCs or polymorphonuclear MDSCs (G-MDSCs or PMN-MDSCs), monocytic MDSCs (M-MDSCs), as well as a recently identified early precursor MDSC (eMDSCs) in humans. Activated MDSCs induce the inactivation of NK cells, CD4+, and CD8+ T cells through a variety of mechanisms, thus promoting the formation of tumor immunosuppressive microenvironment. ER stress plays an important protecting role in the survival of MDSC, which aggravates the immunosuppression in tumors. In addition, ferroptosis can promote an anti-tumor immune response by reversing the immunosuppressive microenvironment. This review summarizes immune suppression by MDSCs with a focus on the role of endoplasmic reticulum stress-mediated immune suppression in cancer and infectious disease, in particular leprosy and tuberculosis.

Umbilical cord mesenchymal stromal cells transplantation delays the onset of hyperglycemia in the RIP-B7.1 mouse model of experimental autoimmune diabetes through multiple immunosuppressive and anti-inflammatory responses

Type 1 diabetes mellitus (T1DM) is an autoimmune disorder specifically targeting pancreatic islet beta cells. Despite many efforts focused on identifying new therapies able to counteract this autoimmune attack and/or stimulate beta cells regeneration, TD1M remains without effective clinical treatments providing no clear advantages over the conventional treatment with insulin. We previously postulated that both the inflammatory and immune responses and beta cell survival/regeneration must be simultaneously targeted to blunt the progression of disease. Umbilical cord-derived mesenchymal stromal cells (UC-MSC) exhibit anti-inflammatory, trophic, immunomodulatory and regenerative properties and have shown some beneficial yet controversial effects in clinical trials for T1DM. In order to clarify conflicting results, we herein dissected the cellular and molecular events derived from UC-MSC intraperitoneal administration (i.p.) in the RIP-B7.1 mouse model of experimental autoimmune diabetes. Intraperitoneal (i.p.) transplantation of heterologous mouse UC-MSC delayed the onset of diabetes in RIP-B7.1 mice. Importantly, UC-MSC i. p. transplantation led to a strong peritoneal recruitment of myeloid-derived suppressor cells (MDSC) followed by multiple T-, B- and myeloid cells immunosuppressive responses in peritoneal fluid cells, spleen, pancreatic lymph nodes and the pancreas, which displayed significantly reduced insulitis and pancreatic infiltration of T and B Cells and pro-inflammatory macrophages. Altogether, these results suggest that UC-MSC i. p. transplantation can block or delay the development of hyperglycemia through suppression of inflammation and the immune attack.

Olfactory ecto-mesenchymal stem cell-derived exosomes ameliorate murine Sjögren's syndrome by modulating the function of myeloid-derived suppressor cells

Sjögren’s syndrome (SS) is a systemic autoimmune disease characterized by progressive inflammation and tissue damage in salivary glands and lacrimal glands. Our previous studies showed that myeloid-derived suppressor cells (MDSCs) exhibited impaired immunosuppressive function during disease progression in patients with SS and mice with experimental Sjögren’s syndrome (ESS), but it remains unclear whether restoring the function of MDSCs can effectively ameliorate the development of ESS. In this study, we found that murine olfactory ecto-mesenchymal stem cell-derived exosomes (OE-MSC-Exos) significantly enhanced the suppressive function of MDSCs by upregulating arginase expression and increasing ROS and NO levels. Moreover, treatment with OE-MSC-Exos via intravenous injection markedly attenuated disease progression and restored MDSC function in ESS mice. Mechanistically, OE-MSC-Exo-secreted IL-6 activated the Jak2/Stat3 pathway in MDSCs. In addition, the abundant S100A4 in OE-MSC-Exos acted as a key factor in mediating the endogenous production of IL-6 by MDSCs via TLR4 signaling, indicating an autocrine pathway of MDSC functional modulation by IL-6. Taken together, our results demonstrated that OE-MSC-Exos possess therapeutic potential to attenuate ESS progression by enhancing the immunosuppressive function of MDSCs, possibly constituting a new strategy for the treatment of Sjögren’s syndrome and other autoimmune diseases.

Persistent lentivirus infection induces early myeloid suppressor cells expansion to subvert protective memory CD8 T cell response✰,✰✰

Background

Memory CD8⁺T cell responses play an essential role in protection against persistent infection. However, HIV-1 evades vaccine-induced memory CD8⁺T cell response by mechanisms that are not fully understood.

Methods

We analyzed the temporal dynamics of CD8⁺T cell recall activity and function during EcoHIV infection in a potent PD1-based vaccine immunized immunocompetent mice.

Findings

Upon intraperitoneal EcoHIV infection, high levels of HIV-1 GAG-specific CD8⁺T lymphocytes recall response reduced EcoHIV-infected cells significantly. However, this protective effect diminished quickly after seven days, followed by a rapid reduction of GAG-specific CD8⁺T cell number and activity, and viral persistence. Mechanistically, EcoHIV activated dendritic cells (DCs) and myeloid cells. Myeloid cells were infected and rapidly expanded, exhibiting elevated PD-L1/-L2 expression and T cell suppressive function before day 7, and were resistant to CD8⁺T cell-mediated apoptosis. Depletion of myeloid-derived suppressor cells (MDSCs) reduced EcoHIV infection and boosted T cell responses.

Interpretation

This study provides an overview of the temporal interplay of persistent virus, DCs, MDSCs and antigen-specific CD8⁺T cells during acute infection. We identify MDSCs as critical gatekeepers that restrain antiviral T cell memory responses, and highlight MDSCs as an important target for developing effective vaccines against chronic human infections.

Funding

Hong Kong Research Grant Council (T11–709/18-N, HKU5/CRF/13G), General Research Fund (17122915 and 17114114), Hong Kong Health and Medical Research Fund (11100752, 14130582, 16150662), Grant RGC-ANR A-HKU709/14, the San-Ming Project of Medicine (SZSM201512029), University Development Fund of the University of Hong Kong and Li Ka Shing Faculty of Medicine Matching Fund to HKU AIDS Institute.

Airway Remodeling in Asthma

Asthma is an inflammatory disease of the airways that may result from exposure to allergens or other environmental irritants, resulting in bronchoconstriction, wheezing, and shortness of breath. The structural changes of the airways associated with asthma, broadly referred to as airway remodeling, is a pathological feature of chronic asthma that contributes to the clinical manifestations of the disease. Airway remodeling in asthma constitutes cellular and extracellular matrix changes in the large and small airways, epithelial cell apoptosis, airway smooth muscle cell proliferation, and fibroblast activation. These pathological changes in the airway are orchestrated by crosstalk of different cell types within the airway wall and submucosa. Environmental exposures to dust, chemicals, and cigarette smoke can initiate the cascade of pro-inflammatory responses that trigger airway remodeling through paracrine signaling and mechanostimulatory cues that drive airway remodeling. In this review, we explore three integrated and dynamic processes in airway remodeling: (1) initiation by epithelial cells; (2) amplification by immune cells; and (3) mesenchymal effector functions. Furthermore, we explore the role of inflammaging in the dysregulated and persistent inflammatory response that perpetuates airway remodeling in elderly asthmatics.

Membrane-associated mucins of the ocular surface: New genes, new protein functions and new biological roles in human and mouse

The mucosal glycocalyx of the ocular surface constitutes the point of interaction between the tear film and the apical epithelial cells. Membrane-associated mucins (MAMs) are the defining molecules of the glycocalyx in all mucosal epithelia. Long recognized for their biophysical properties of hydration, lubrication, anti-adhesion and repulsion, MAMs maintain the wet ocular surface, lubricate the blink, stabilize the tear film and create a physical barrier to the outside world. However, it is increasingly appreciated that MAMs also function as cell surface receptors that transduce information from the outside to the inside of the cell. A number of excellent review articles have provided perspective on the field as it has progressed since 1987, when molecular cloning of the first MAM was reported. The current article provides an update for the ocular surface, placing it into the broad context of findings made in other organ systems, and including new genes, new protein functions and new biological roles. We discuss the epithelial tissue-equivalent with mucosal differentiation, the key model system making these advances possible. In addition, we make the first systematic comparison of MAMs in human and mouse, establishing the basis for using knockout mice for investigations with the complexity of an in vivo system. Lastly, we discuss findings from human genetics/genomics, which are providing clues to new MAM roles previously unimagined. Taken together, this information allows us to generate hypotheses for the next stage of investigation to expand our knowledge of MAM function in intracellular signaling and roles unique to the ocular surface.

Natural killer cells and pigment epithelial-derived factor control the infiltrative and nodular growth of hepatic metastases in an Orthotopic murine model of ocular melanoma

Background

Metastases account for 90% of all cancer-related deaths, becoming a therapeutic problem. Approximately 50% of all uveal melanoma (UM) patients will develop metastases, mainly in the liver. Post-mortem analyses of livers from metastatic UM patients showed two different metastatic growth patterns: infiltrative and nodular. The infiltrative pattern exhibits tumor infiltration directly to the hepatic lobule and minimal angiogenesis. The nodular pattern shows clusters of tumor cells around the portal venules that efface the liver parenchyma. We recently demonstrated Natural Killer (NK) cells play a pivotal role in the control of hepatic metastases and the pigment epithelial-derived factor (PEDF) controls angiogenesis in the liver using our established ocular melanoma animal model. In this study we investigated the role of NK cells and PEDF in the development of metastatic growth patterns, as this can contribute to the development of novel therapeutics specific towards each growth pattern.

Methods

We utilize our established ocular melanoma animal model by inoculation of B16-LS9 melanoma cells into C57BL/6 J mice (WT), anti-asialo GM1-treated C57BL/6 J mice (NK-depleted), and PEDF^−/− C57BL/6 J mice. Three weeks after inoculation we evaluated the metastatic growth patterns and stratified them based of the numbers of tumor cells. To evaluate angiogenesis the mean vascular density (MVD) was calculated. The immune compartment of the liver was analyzed by flow cytometry.

Results

Our in vivo work showed two distinct metastatic growth patterns, the infiltrative and nodular, recapitulating the post-mortem analyses on human liver tissue. We discovered NK cells control the infiltrative growth. In contrast, PEDF controlled anti-angiogenic responses, showing higher MVD values compared to NK-depleted and WT animals. The myeloid lineage, comprised of monocytes, macrophages, and myeloid-derived suppressor cells, was reduced in the absence of NK cells or PEDF.

Conclusions

Our animal model recapitulates the metastatic growth patterns observed in the human disease. We demonstrated a role for NK cells in the development of the infiltrative growth pattern, and a role for PEDF in the development of the nodular pattern. The understanding of the complexity associated with the metastatic progression has profound clinical implications in the diagnostic and disease-management as we can develop and direct more effective therapies.

Nicotinamide Phosphoribosyltransferase Acts as a Metabolic Gate for Mobilization of Myeloid-Derived Suppressor Cells

Cancer induces alteration of hematopoiesis to fuel disease progression. We report that in tumor-bearing mice the macrophage colony-stimulating factor elevates the myeloid cell levels of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway, which acts as negative regulator of the CXCR4 retention axis of hematopoietic cells in the bone marrow. NAMPT inhibits CXCR4 through a NAD/Sirtuin 1-mediated inactivation of HIF1α-driven CXCR4 gene transcription, leading to mobilization of immature myeloid-derived suppressor cells (MDSC) and enhancing their production of suppressive nitric oxide. Pharmacologic inhibition or myeloid-specific ablation of NAMPT prevented MDSC mobilization, reactivated specific antitumor immunity, and enhanced the antitumor activity of immune checkpoint inhibitors. Our findings identify NAMPT as a metabolic gate of MDSC precursor function, providing new opportunities to reverse tumor immunosuppression and to restore clinical efficacy of immunotherapy in patients with cancer. SIGNIFICANCE: These findings identify NAMPT as a metabolic gate of MDSC precursor function, providing new opportunities to reverse tumor immunosuppression and to restore clinical efficacy of immunotherapy in cancer patients.

M10, a novel derivative of Myricetin, prevents ulcerative colitis and colorectal tumor through attenuating robust endoplasmic reticulum stress

Chronic gut inflammation disposes to an increased risk of colitis-associated cancer. Chemoprevention is an attractive complementary strategy. We aimed to evaluate the chemopreventive effects of M10, a novel derivative of Myricetin, in the murine azoxymethane/dextran sodium sulfate model. Oral administration of M10 at 50-100 mg/kg once a day for consecutive 12 weeks significantly prevented ulcerative colitis (UC) and colorectal tumor. Pathological analysis of intestines showed that M10 reduced the degree of chronic inflammation and prevented the progression of colorectal tumorigenesis. Flow cytometry analysis of the immunocytes isolated from intraepithelial and lamina propria showed that M10 prevented the infiltration of myeloid-derived suppressor cells and increased CD8+T and CD4+T cells in colorectal tissues. Enzyme-linked immunosorbent analysis revealed the reduction of pro-inflammatory mediators granulocyte-macrophage colony-stimulating factor/macrophage colony-stimulating factor, IL-6 and TNF-α in colonic mucosa. Western blot assay also showed M10 prevention of the NF-κB/IL-6/STAT3 pathways and the biomarkers of inflammation and colorectal tumorigenesis. Electron microscopy analysis revealed that M10 prevent robust endoplasmic reticulum (ER) stress-induced autophagy in inflamed colonic mucosal cells. In conclusion, oral administration of Myricetin derivative M10 exerts chemoprevention of UC and colorectal tumor in mice. The mechanism of chemoprevention is associated with the reduction of biomarkers of chronic inflammation and proliferation through attenuating robust ER stress in inflamed colonic mucosal cells. M10 exerts chemoprevention activity without evidence of toxicity in mice. These results justify further evaluation of M10 in clinical trials. M10 could develop a promising regimen in the chemoprevention of colitis and colorectal cancer.

In Vitro Suppression of CD4+ T-Cell Responses by Murine and Human Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are myeloid precursors of macrophages, dendritic cells, and neutrophils with a prominent role in the regulation of immune responses in cancer, infection, and autoimmunity. Herein, we describe a protocol for the isolation of murine and human MDSCs and the assessment of their ability to suppress CD4⁺ T-cell responses in vitro.

Roles of Myeloid-Derived Suppressor Cell Subpopulations in Autoimmune Arthritis

Emerging evidence suggests the promise of the use of myeloid-derived suppressor cells (MDSCs) in inflammatory disorders based on their unique immune-intervention properties. However, the roles of MDSCs in autoimmune arthritis are not completely understood. Indeed, their immunosuppressive functions in arthritic conditions remain controversial, with heterogeneity among MDSCs and differential effects among subpopulations receiving much attention. As a result, it is necessary to determine the roles of MDSC subpopulations in autoimmune arthritis to clarify their diagnostic and therapeutic potential. Interestingly, in the inflammation niche of autoimmune arthritis, each MDSC subpopulation can exhibit both alternatives of a given characteristic. Moreover, polymorphonuclear MDSCs (PMN-MDSCs) are likely to be more suppressive and stable compared with monocytic MDSCs (MO-MDSCs). Although various important cytokines associated with the differentiation of MDSCs or MDSC subpopulations from immature myeloid precursors, such as granulocyte colony-stimulating factor (G-CSF), have been largely applied in external inductive systems, their roles are not entirely clear. Moreover, MDSC-based clinical treatments in rheumatoid arthritis (RA) continue to represent a significant challenge, as also reported for other autoimmune diseases. In this review, we describe the effects and actions of MDSC subpopulations on the development of autoimmune arthritis and analyze several types of MDSC-based therapeutic strategies to provide comprehensive information regarding immune networks and a foundation for more effective protocols for autoimmune arthritis.

Myeloid-derived suppressor cells exacerbate Sjögren's syndrome by inhibiting Th2 immune responses

Myeloid-derived suppressor cells (MDSCs) can regulate various aspects of immune responses based on their potent immune-suppressive activity. Studies reported that MDSCs participated in many autoimmune diseases. However, the role of MDSCs in Sjögren's syndrome (SS) is unknown. In this study, we determined the frequencies and function of MDSCs in non-obese diabetic (NOD) mice and SS patients. The NOD mice were adoptively transferred with MDSCs or treated with anti-Gr1 antibody. Results showed that peripheral MDSCs increased significantly with the development of SS-like syndrome in NOD mice and the percentage of MDSCs was higher in SS patients than healthy controls. The SS-like syndrome aggravated after transfer of MDSCs in NOD mice. The deletion of MDSCs in NOD mice alleviated SS-like syndrome. Mechanistically, MDSCs down-regulated the percentages of Th2 cells in NOD mice and SS patients. In summary, our findings suggested that MDSCs exacerbated Sjögren's syndrome by inhibiting Th2 cells.

Prognostic value of lymphocyte-to-monocyte ratio and neutrophil-to-lymphocyte ratio in follicular lymphoma: a retrospective cohort study

OBJECTIVES

The clinical course and prognosis of follicular lymphoma (FL) are diverse and associated with the patient's immune response. We investigated the lymphocyte-to-monocyte ratio (LMR) and neutrophil-to-lymphocyte ratio (NLR) as prognostic factors in patients with FL, including those receiving radiotherapy.

DESIGN

A retrospective cohort study.

SETTING

Regional cancer centre in Hong Kong.

PARTICIPANTS

88 patients with histologically proven FL diagnosed between 2000 and 2014.

MATERIALS AND METHODS

The best LMR and NLR cut-off values were determined using cross-validated areas under the receiver operating characteristic curves. The extent to which progression-free survival (PFS) and overall survival differed by NLR and LMR cut-off values was assessed using Kaplan-Meier analysis and log-rank tests. A Cox proportional hazards model was fitted to adjust for confounders.

RESULTS

The best cut-off values for LMR and NLR were 3.20 and 2.18, respectively. The 5-year PFS was 73.6%. After multivariate adjustment, high LMR (>3.20) at diagnosis was associated with superior PFS, with a HR of 0.31 (95% CI 0.13 to 0.71), whereas high NLR at relapse was associated with poorer postprogression survival (HR 1.24, 95% CI 1.04 to 1.49).

CONCLUSIONS

Baseline LMR and NLR at relapse were shown to be independent prognostic factors in FL. LMR and NLR are cheap and widely available biomarkers that could be used in combination with the Follicular Lymphoma International Prognostic Index by clinicians to better predict prognosis.

Coexistence of sarcoidosis and metastatic lesions: A diagnostic and therapeutic dilemma

Sarcoidosis, a chronic, inflammatory disease that affects various different organs, is characterized by noncaseating epitheloid granulomas. This systemic inflammatory process is associated with an increased risk of cancer. Several cases of sarcoidosis that mimic metastatic tumor progression in radiological findings have been reported so far. However, there are also cases that have presented a coexistence of sarcoidosis and metastasis, which have caused a diagnostic and therapeutic dilemma. Due to inadequate current therapies, a reliable differentiation between benign and malignant lesions is crucial. This review focuses on the residual risk of the coexistence of metastases within radiological suspicious lesions in patients with a history of solid tumors and sarcoidosis, as well as immunological findings, in order to explain the potential associations. Sarcoidosis has the potential to promote metastasis as it includes tumor-promoting and immune-regulating cell subsets. Notably, myeloid derived suppressor cells may serve a pivotal role in metastatic progression in patients with sarcoidosis. In addition, the present review also evaluates the potential novel diagnostic approaches, which may be able to differentiate between metastatic lesions and sarcoidosis. The risk of coexistent metastasis in sarcoidosis lesions must be considered by clinical practitioners, and a multidisciplinary approach may be required to avoid misdiagnosis and the subsequent unnecessary surgery or insufficient treatments.

Pak2 regulates myeloid-derived suppressor cell development in mice

Myeloid-derived suppressor cells (MDSCs) are CD11b⁺Gr1⁺ cells that induce T-cell hyporesponsiveness, thus impairing antitumor immunity. We have previously reported that disruption of Pak2, a member of the p21-activated kinases (Paks), in hematopoietic stem/progenitor cells (HSPCs) induces myeloid lineage skewing and expansion of CD11b^highGr1^high cells in mice. In this study, we confirmed that Pak2-KO CD11b^highGr1^high cells suppressed T-cell proliferation, consistent with an MDSC phenotype. Loss of Pak2 function in HSPCs led to (1) increased hematopoietic progenitor cell sensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling, (2) increased MDSC proliferation, (3) decreased MDSC sensitivity to both intrinsic and Fas-Fas ligand-mediated apoptosis, and (4) promotion of MDSCs by Pak2-deficient CD4⁺ T cells that produced more interferon γ, tumor necrosis factor α, and GM-CSF. Pak2 disruption activated STAT5 while downregulating the expression of IRF8, a well-described myeloid transcription factor. Together, our data reveal a previously unrecognized role of Pak2 in regulating MDSC development via both cell-intrinsic and extrinsic mechanisms. Our findings have potential translational implications, as the efficacy of targeting Paks in cancer therapeutics may be undermined by tumor escape from immune control and/or acceleration of tumorigenesis through MDSC expansion.

Deep Immune Profiling of an Arginine-Enriched Nutritional Intervention in Patients Undergoing Surgery

Application of high-content immune profiling technologies has enormous potential to advance medicine. Whether these technologies reveal pertinent biology when implemented in interventional clinical trials is an important question. The beneficial effects of preoperative arginine-enriched dietary supplements (AES) are highly context specific, as they reduce infection rates in elective surgery, but possibly increase morbidity in critically ill patients. This study combined single-cell mass cytometry with the multiplex analysis of relevant plasma cytokines to comprehensively profile the immune-modifying effects of this much-debated intervention in patients undergoing surgery. An elastic net algorithm applied to the high-dimensional mass cytometry dataset identified a cross-validated model consisting of 20 interrelated immune features that separated patients assigned to AES from controls. The model revealed wide-ranging effects of AES on innate and adaptive immune compartments. Notably, AES increased STAT1 and STAT3 signaling responses in lymphoid cell subsets after surgery, consistent with enhanced adaptive mechanisms that may protect against postsurgical infection. Unexpectedly, AES also increased ERK and P38 MAPK signaling responses in monocytic myeloid-derived suppressor cells, which was paired with their pronounced expansion. These results provide novel mechanistic arguments as to why AES may exert context-specific beneficial or adverse effects in patients with critical illness. This study lays out an analytical framework to distill high-dimensional datasets gathered in an interventional clinical trial into a fairly simple model that converges with known biology and provides insight into novel and clinically relevant cellular mechanisms.

Potential Contributions of Antioxidants to Cancer Therapy: Immunomodulation and Radiosensitization

Antioxidants play important roles in the maintenance of cellular integrity and thus are critical in maintaining the homeostasis of the host immune system. A balance between the levels of pro-oxidants and antioxidants defines the cellular fate of genomic integrity via maintaining the redox status of the cells. An aberration in this balance modulates host immunity that affects normal cellular signaling pathways resulting in uncontrolled proliferation of cells leading to neocarcinogenesis. For decades, there have been scientific debates on the use of antioxidants for the treatment of human cancers. This review is focused on current updates on the implications of antioxidant use as adjuncts in cancer therapy with an emphasis on immunomodulation and radiosensitization.

Aberrant function of myeloid-derived suppressor cells (MDSCs) in experimental colitis and in inflammatory bowel disease (IBD) immune responses

BACKGROUND AND AIMS

Myeloid-derived suppressor cells (MDSCs) encompass a novel population of suppressor cells and a potential candidate for cell-based therapies in inflammatory diseases. Herein, we investigated their immunomodulatory properties in experimental inflammatory colitis and T cell-mediated immune responses in inflammatory bowel disease (IBD) patients.

METHODS

MDSCs (defined as CD14^-HLA^-DR^-/lowCD33⁺CD15⁺) numbers were determined in peripheral blood (PB) from IBD patients. PB MDSC function was assessed in vitro. Experimental colitis was induced upon 2,4,6-trinitrobenzene sulfonic acid (TNBS) treatment and MDSCs were characterized by flow cytometry. The in vivo suppressive potential of bone marrow (BM)-derived MDSCs (BM-MDSCs) was tested by using both depleting and adoptive transfer strategies.

RESULTS

MDSCs were enriched in the periphery of IBD patients during active disease. TNBS colitis induced amplification of MDSCs, particularly of the granulocytic (Ly6G⁺) subset during the effector phase of disease. Of interest, BM-MDSCs potently suppressed CD4⁺T cell responses under steady state but failed to control colitis-associated immune responses in vivo. Mechanistically, under the colonic inflammatory milieu MDSCs switched phenotype (decreased proportion of Gr1^high and increased numbers of Gr1^low) and downregulated CCAAT/enhancer-binding protein beta (CEBPβ) expression, a critical transcription factor for the suppressive function of MDSCs. In accordance with the murine data, human CD33 ⁺ CD15⁺MDSCs from peripheral blood of IBD patients not only failed to suppress autologous T cell responses but instead enhanced T cell proliferation in vitro.

CONCLUSIONS

Our findings demonstrate an aberrant function of MDSCs in experimental inflammatory colitis and in IBD-associated immune responses in vitro. Delineation of the mechanisms that underlie the loss of MDSCs function in IBD may provide novel therapeutic targets.

Genetically engineered mucin mouse models for inflammation and cancer

Mucins are heavily O-glycosylated proteins primarily produced by glandular and ductal epithelial cells, either in membrane-tethered or secretory forms, for providing lubrication and protection from various exogenous and endogenous insults. However, recent studies have linked their aberrant overexpression with infection, inflammation, and cancer that underscores their importance in tissue homeostasis. In this review, we present current status of the existing mouse models that have been developed to gain insights into the functional role(s) of mucins under physiological and pathological conditions. Knockout mouse models for membrane-associated (Muc1 and Muc16) and secretory mucins (Muc2) have helped us to elucidate the role of mucins in providing effective and protective barrier functions against pathological threats, participation in disease progression, and improved our understanding of mucin interaction with biotic and abiotic environmental components. Emphasis is also given to available transgenic mouse models (MUC1 and MUC7), which has been exploited to understand the context-dependent regulation and therapeutic potential of human mucins during inflammation and cancer.

TGF- and VEGF cooperatively control the immunotolerant tumor environment and the efficacy of cancer immunotherapies

Tregs imprint an early immunotolerant tumor environment that prevents effective antitumor immune responses. Using transcriptomics of tumor tissues, we identified early upregulation of VEGF and TGF-β pathways compatible with tolerance imprinting. Silencing of VEGF or TGF-β in tumor cells induced early and pleiotropic modulation of immune-related transcriptome signatures in tumor tissues. These were surprisingly similar for both silenced tumors and related to common downstream effects on Tregs. Silencing of VEGF or TGF-β resulted in dramatically delayed tumor growth, associated with decreased Tregs and myeloid-derived suppressor cells and increased effector T cell activation in tumor infiltrates. Strikingly, co-silencing of TGF-β and VEGF led to a substantial spontaneous tumor eradication rate and the combination of their respective inhibitory drugs was synergistic. VEGF and/or TGF-β silencing also restored tumor sensitivity to tumor-specific cell therapies and markedly improved the efficacy of anti-PD-1/anti-CTLA-4 treatment. Thus, TGF-β and VEGF cooperatively control the tolerant environment of tumors and are targets for improved cancer immunotherapies.

Finasteride Enhances the Generation of Human Myeloid-Derived Suppressor Cells by Up-Regulating the COX2/PGE2 Pathway

Myeloid-derived suppressor cells (MDSCs) have been known to be a key factor in the regulation of the immune system under numerous conditions such as tumors, infections, autoimmune diseases, and transplantations. In contrast to the proposed deleterious role of MDSCs in tumors and infections, MDSCs with their suppressive function are now proved to have the beneficial potential of suppressing the autoimmune response and promoting tolerance to transplantation. Therefore, the expansion of MDSCs could be a promising therapeutic strategy for many diseases. In this study, we aimed to identify FDA-approved drugs that could aid in the expansion of functional MDSCs. We performed a high-throughput screening (HTS) of FDA-approved drugs based on the in vitro human MDSC-differentiation system and identified finasteride (FIN) to have the best potency to aid the generation of human MDSCs. The FIN-induced MDSCs were quite similar to monocytic MDSCs with regard to their surface phenotype, morphology, immunosuppressive function, and related gene expression. Next, we aimed to determine the mechanism of action of FIN and found that FIN induced the expansion of MDSCs through up-regulation of the COX2/PGE2 pathway by enhancing the activity of COX2 promoter. In addition, the administration of indomethacin (IND), a COX2 inhibitor, abrogated the effect of FIN. Based on these results, we suggested that FIN could find applications in the future in the expansion of MDSCs. Further development of FIN-like compounds could be a novel strategy for generating functional MDSCs for immunosuppressive therapies in various immune disorder conditions.

Restoring Anticancer Immune Response by Targeting Tumor-Derived Exosomes With a HSP70 Peptide Aptamer

BACKGROUND

Exosomes, via heat shock protein 70 (HSP70) expressed in their membrane, are able to interact with the toll-like receptor 2 (TLR2) on myeloid-derived suppressive cells (MDSCs), thereby activating them.

METHODS

We analyzed exosomes from mouse (C57Bl/6) and breast, lung, and ovarian cancer patient samples and cultured cancer cells with different approaches, including nanoparticle tracking analysis, biolayer interferometry, FACS, and electron microscopy. Data were analyzed with the Student's t and Mann-Whitney tests. All statistical tests were two-sided.

RESULTS

We showed that the A8 peptide aptamer binds to the extracellular domain of membrane HSP70 and used the aptamer to capture HSP70 exosomes from cancer patient samples. The number of HSP70 exosomes was higher in cancer patients than in healthy donors (mean, ng/mL ± SD = 3.5 ± 1.7 vs 0.17 ± 0.11, respectively, P = .004). Accordingly, all cancer cell lines examined abundantly released HSP70 exosomes, whereas "normal" cells did not. HSP70 had higher affinity for A8 than for TLR2; thus, A8 blocked HSP70/TLR2 association and the ability of tumor-derived exosomes to activate MDSCs. Treatment of tumor-bearing C57Bl/6 mice with A8 induced a decrease in the number of MDSCs in the spleen and inhibited tumor progression (n = 6 mice per group). Chemotherapeutic agents such as cisplatin or 5FU increase the amount of HSP70 exosomes, favoring the activation of MDSCs and hampering the development of an antitumor immune response. In contrast, this MDSC activation was not observed if cisplatin or 5FU was combined with A8. As a result, the antitumor effect of the drugs was strongly potentiated.

CONCLUSIONS

A8 might be useful for quantifying tumor-derived exosomes and for cancer therapy through MDSC inhibition.

Myeloid-derived suppressor cells are essential for maintaining feto-maternal immunotolerance via STAT3 signaling in mice

Maternal immune system tolerance to the semiallogeneic fetus is essential for a successful pregnancy; however, the mechanisms underlying this immunotolerance have not been fully elucidated. Here, we demonstrate that myeloid-derived suppressor cells play an important role in maintaining feto-maternal tolerance. A significant expansion of granulocytic myeloid-derived suppressor cells was observed in multiple immune organs and decidual tissues from pregnant mice. Pregnancy-derived granulocytic myeloid-derived suppressor cells suppressed T cell responses in a reactive oxygen species-dependent manner and required direct cell-cell contact. Mechanistic studies showed that progesterone facilitated differentiation and activation of granulocytic myeloid-derived suppressor cells, mediated through STAT3 signaling. The STAT3 inhibitor JSI-124 and a specific short hairpin RNA completely abrogated the effects of progesterone on granulocytic myeloid-derived suppressor cells. More importantly, granulocytic myeloid-derived suppressor cell depletion dramatically enhanced the abortion rate in normal pregnant mice, whereas adoptive transfer of granulocytic myeloid-derived suppressor cells clearly reduced the abortion rate in the CBA/J X DBA/2J mouse model of spontaneous abortion. These observations collectively demonstrate that granulocytic myeloid-derived suppressor cells play an essential role in the maintenance of fetal immunotolerance in mice. Furthermore, our study supports the notion that in addition to their well-recognized roles under pathologic conditions, myeloid-derived suppressor cells perform important functions under certain physiologic circumstances.

Effects of Adoptive Transferring Different Sources of Myeloid-Derived Suppressor Cells in Mice Corneal Transplant Survival

BACKGROUND

Adoptively transferring different sources of myeloid-derived suppressor cells (MDSCs) may assist in mice corneal transplant survival.

METHODS

Allogeneic full thickness corneal transplantation (donor C57BL/6 to recipient Balb/c mice) was performed. Naive myeloid cells, inflammation-induced MDSCs (iMDSCs), and tumor-induced MDSCs (tMDSCs) were purified from bone marrow of naive, cecal ligation and puncture, or tumor-bearing Balb/c mice, respectively. The inhibitory abilities of myeloid cells toward CD4(+) T cell proliferation were accessed by in vitro carboxyfluorescein diacetate, succinimidyl ester (CFSE) assays. Myeloid cells were adoptively transferred to corneal recipients by retroorbital injection after corneal transplantation. Corneal grafts were examined and photographed for a period of 45 days. The growth of corneal graft neovascularization was quantitatively measured by image editing software. Histopathology was performed to evaluate corneal graft inflammation.

RESULTS

The iMDSCs and tMDSCs significantly inhibited T cell proliferation in vitro and significantly prolonged corneal allograft survival in vivo. Strikingly, iMDSC transferring significantly reduced neovascularization that was comparable to transferring of tMDSCs, without additional immunosuppression. However, additional adoptive transfer of MDSCs did not further ameliorate corneal survival in these allogeneic corneal transplantation mice.

CONCLUSIONS

Inflammation-induced MDSC transfer could reduce corneal neovascularization and prolong corneal allograft survival.

CD11b+Ly6G+ cells inhibit tumor growth by suppressing IL-17 production at early stages of tumorigenesis

Neutrophils are important innate immune cells involved in microbial clearance at the sites of infection. However, their role in cancer development is unclear. We hypothesized that neutrophils mediate antitumor effects in early tumorigenesis. To test this, we first studied the cytotoxic effects of neutrophils in vitro. Neutrophils were cytotoxic against tumor cells, with neutrophils isolated from tumor-bearing mice trending to have increased cytotoxic activities. We then injected an ELR+ CXC chemokine-producing tumor cell line into C57BL/6 and Cxcr2−/− mice, the latter lacking the receptors for neutrophil chemokines. We observed increased tumor growth in Cxcr2−/− mice. As expected, tumors from Cxcr2−/− mice contained fewer neutrophils. Surprisingly, these tumors also contained fewer CD8⁺ T cells, but more IL-17-producing cells. Replenishment of functional neutrophils was correlated with decreased IL-17-producing cells, increased CD8⁺ T cells, and decreased tumor size in Cxcr2−/− mice, while depletion of neutrophils in C57BL/6 mice showed the opposite effects. Results from a non-ELR+ CXC chemokine producing tumor further supported that functional neutrophils indirectly mediate tumor control by suppressing IL-17A production. We further studied the correlation of IL-17A and CD8⁺ T cells in vitro. IL-17A suppressed proliferation and IFNγ production of CD8⁺ T cells, while CD11b+Ly6G+ neutrophils did not suppress CD8⁺ T cell function. Taken together, these data demonstrate that, while neutrophils could control tumor growth by direct cytotoxic effects, the primary mechanism by which neutrophils exert antitumor effects is to regulate IL-17 production, through which they indirectly promote CD8⁺ T cell responses.

Clinical significance of myeloid-derived suppressor cells in human renal transplantation with acute T cell-mediated rejection

Myeloid-derived suppressor cells (MDSCs) are negative regulators of the immune response and are in part responsible for the inhibition of the T cell-mediated immune response. A recent paper indicated that MDSCs were involved in prolonged allograft survival in animal models of transplantation, but the significance of MDSCs in human renal transplantation is still unknown. In our study, 50 patients with biopsy-proven acute T cell-mediated rejection (ATCMR) were included. The ratio of MDSCs in peripheral blood mononuclear cell (PBMC) was evaluated with FACS, and the patients were divided into the MDSCs high group (MDSCs, >10 %) or the MDSCs low group (MDSCs, <10 %). We compared the allograft function, severity of tissue injury, and long-time survival between the two groups. In the MDSCs high group, allograft function was significantly increased compared with the MDSCs low group. Furthermore, we found that isolated MDSCs from transplant recipients are capable of expanding regulatory T cell (Treg), meanwhile, inhibiting production of IL-17 in vitro. We also found that the ratio between Foxp3(+) and IL-17-producing CD4(+) T cells positively correlated with MDSCs frequency in PBMC. In conclusion, we demonstrated a potential role for MDSCs in prolonging allograft survival after ATCMR, and this was associated with higher CD4(+)Foxp3(+)/CD4(+)IL-17(+) ratio in PBMC.

Clinical Impact of the Immunome in Lymphoid Malignancies: The Role of Myeloid-Derived Suppressor Cells

The better definition of the mutual sustainment between neoplastic cells and immune system has been translated from the bench to the bedside acquiring value as prognostic factor. Additionally, it represents a promising tool for improving therapeutic strategies. In this context, myeloid-derived suppressor cells (MDSCs) have gained a central role in tumor developing with consequent therapeutic implications. In this review, we will focus on the biological and clinical impact of the study of MDSCs in the settings of lymphoid malignancies.

Subsets of airway myeloid-derived regulatory cells distinguish mild asthma from chronic obstructive pulmonary disease

BACKGROUND

Subsets of myeloid-derived regulatory cells (MDRCs), which are phenotypically similar to the myeloid-derived suppressor cells found in patients with cancer, have recently been appreciated as critical regulators of airway inflammation in mouse models of asthma.

OBJECTIVE

We test the hypothesis that subsets of airway MDRCs contribute differentially to the inflammatory milieu in human asthma and chronic obstructive pulmonary disease (COPD).

METHODS

We used bronchoalveolar lavage to identify and characterize human airway MDRCs from 10 healthy subjects, 9 patients with mild asthma, and 8 patients with COPD, none of whom were treated with inhaled or systemic corticosteroids. We defined subsets of airway MDRCs using flow cytometry, the molecular mediators they produce, and their abilities to regulate proliferation of polyclonally activated autologous T lymphocytes.

RESULTS

We found substantial differences in the functional potential of MDRC subsets in healthy subjects, patients with asthma, and patients with COPD, with these differences regulated by the nitrosative and oxidative free radicals and cytokines they produced. Nitric oxide-producing MDRCs suppressed and superoxide-producing MDRCs enhanced proliferation of polyclonally activated autologous CD4 T cells. HLA-DR(+)CD11b(+)CD11c(+)CD163(-) superoxide-producing MDRCs, which stimulated proliferation of autologous T cells, comprised a high fraction of MDRCs in the airways of patients with mild asthma or COPD but not those of healthy control subjects. CD11b(+)CD14(+)CD16(-)HLA-DR(-) nitric oxide-producing MDRCs, which suppressed T-cell proliferation, were present in high numbers in airways of patients with mild asthma but not patients with COPD or healthy control subjects.

CONCLUSION

Subsets of airway MDRCs conclusively discriminate patients with mild asthma, patients with COPD, and healthy subjects from each other. The distinctive activities of these MDRCs in patients with asthma or COPD might provide novel targets for new therapeutics for these common disorders. [Corrected]

Cell-based modulation of autoimmune responses in multiple sclerosis and experimental autoimmmune encephalomyelitis: therapeutic implications

Multiple sclerosis (MS) is a prototypic autoimmune inflammatory disorder of the central nervous system (CNS). MS pathogenesis is a complex phenomenon that is influenced by genetic and environmental factors that lead to the dysregulation of immune homeostasis and tolerance. It has been shown that pathogenic T lymphocyte subsets, such as T helper 1 (Th1) and Th17 cells, play a crucial role in the autoimmune cascade influencing disease initiation, progression and subsequent tissue damage during MS. On the other hand, several mechanisms have been described in both patients and animal models of MS with the potential to modulate myelin-specific autoimmune responses and to facilitate amelioration of disease pathology. To this end, regulatory T cells (Tregs) are considered to be a powerful cell subset not only in the maintenance of homeostasis but also in the re-establishment of tolerance. Along these lines, other cell subsets such as dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), γδ T cells and natural killer (NK) cells have been shown to regulate the autoimmune response in the CNS under certain circumstances. This review will attempt to summarize the relevant knowledge of the regulatory mechanisms exerted by immune cells in MS that could hold the promise for the design of novel therapeutic strategies.

Exposure to cigarette smoke impacts myeloid-derived regulatory cell function and exacerbates airway hyper-responsiveness

Cigarette smoking enhances oxidative stress and airway inflammation in asthma, the mechanisms of which are largely unknown. Myeloid-derived regulatory cells (MDRC) are free radical producing immature myeloid cells with immunoregulatory properties that have recently been demonstrated as critical regulators of allergic airway inflammation. NO (nitric oxide)-producing immunosuppressive MDRC suppress T-cell proliferation and airway-hyper responsiveness (AHR), while the O2(•-) (superoxide)-producing MDRC are proinflammatory. We hypothesized that cigarette smoke (CS) exposure may impact MDRC function and contribute to exacerbations in asthma. Exposure of bone marrow (BM)-derived NO-producing MDRC to CS reduced the production of NO and its metabolites and inhibited their potential to suppress T-cell proliferation. Production of immunoregulatory cytokine IL-10 was significantly inhibited, while proinflammatory cytokines IL-6, IL-1β, TNF-α and IL-33 were enhanced in CS-exposed BM-MDRC. Additionally, CS exposure increased NF-κB activation and induced BM-MDRC-mediated production of O2(•-), via NF-κB-dependent pathway. Intratracheal transfer of smoke-exposed MDRC-producing proinflammatory cytokines increased NF-κB activation, reactive oxygen species and mucin production in vivo and exacerbated AHR in C57BL/6 mice, mice deficient in Type I IFNR and MyD88, both with reduced numbers of endogenous MDRC. Thus CS exposure modulates MDRC function and contributes to asthma exacerbation and identifies MDRC as potential targets for asthma therapy.

Circulating myeloid-derived suppressor cells correlate with clinical outcome in Hodgkin Lymphoma patients treated up-front with a risk-adapted strategy

In the attempt to find a peripheral blood biological marker that could mirror the dysregulated microenvironment of Hodgkin Lymphoma (HL), we analysed the amount of myeloid-derived suppressor cells (MDSC), including the three main sub-types (monocytic, granulocytic and CD34 + fraction). The absolute MDSC count was investigated in 60 consecutive newly diagnosed HL patients and correlated with clinical variables at diagnosis and outcome. Patients received standard-of-care chemotherapy with the exception of interim fluorodeoxyglucose positron emission tomography (PET-2)-positive patients, who were switched early to a salvage regimen. All MDSC subsets were increased in HL patients compared to normal subjects (P < 0·0001) and were higher in non-responders. However, a strong prognostic significance was limited to immature (CD34(+) ) MDSC. A cut-off level of 0·0045 × 10(9) /l for CD34(+) MDSC resulted in 89% (95% confidence interval [CI] 52-99%) sensitivity and 92% (95% CI 81-98%) specificity. The positive predictive value to predict progression-free survival was 0·90 for PET-2 and 0·98 for CD34(+) MDSC count; the negative predictive value was 0·57 for PET-2 and 0·73 for CD34(+) MDSC. PFS was significantly shorter in patients with more than 0·0045 × 10(9) CD34(+) MDSC cells/l at diagnosis and/or PET-2 positivity (P < 0·0001). In conclusion, all circulating MDSC subsets are increased in HL; CD34(+) MDSC predict short PFS, similarly to PET-2 but with the advantage of being available at diagnosis.

Immunological dysregulation in multiple myeloma microenvironment

Multiple Myeloma (MM) is a systemic hematologic disease due to uncontrolled proliferation of monoclonal plasma cells (PC) in bone marrow (BM). Emerging in other solid and liquid cancers, the host immune system and the microenvironment have a pivotal role for PC growth, proliferation, survival, migration, and resistance to drugs and are responsible for some clinical manifestations of MM. In MM, microenvironment is represented by the cellular component of a normal bone marrow together with extracellular matrix proteins, adhesion molecules, cytokines, and growth factors produced by both stromal cells and PC themselves. All these components are able to protect PC from cytotoxic effect of chemo- and radiotherapy. This review is focused on the role of immunome to sustain MM progression, the emerging role of myeloid derived suppressor cells, and their potential clinical implications as novel therapeutic target.

Novel role for tumor-induced expansion of myeloid-derived cells in cancer cachexia

Cancer progression is associated with inflammation, increased metabolic demand, infection, cachexia, and eventually death. Myeloid-derived suppressor cells (MDSCs) commonly expand during cancer and are associated with adaptive immune suppression and inflammatory metabolite production. We propose that cancer-induced cachexia is driven at least in part by the expansion of MDSCs. MDSC expansion in 4T1 mammary carcinoma-bearing hosts is associated with induction of a hepatic acute-phase protein response and altered host energy and fat metabolism, and eventually reduced survival to polymicrobial sepsis and endotoxemia. Similar results are also seen in mice bearing a Lewis lung carcinoma and a C26 colon adenocarcinoma. However, a similar cachexia response is not seen with equivalent growth of the 66C4 subclone of 4T1, in which MDSC expansion does not occur. Importantly, reducing MDSC numbers in 4T1-bearing animals can ameliorate some of these late responses and reduce susceptibility to inflammation-induced organ injury and death. In addition, administering MDSCs from both tumor- and nontumor-bearing mice can produce an acute-phase response. Thus, we propose a previously undescribed mechanism for the development of cancer cachexia, whereby progressive MDSC expansion contributes to changes in host protein and energy metabolism and reduced resistance to infection.

Rapid tolerance induction by hematopoietic progenitor cells in the absence of donor-matched lymphoid cells

BACKGROUND

Donor specific hematopoietic cell transplantation has long been recognized for its potential in tolerance induction for subsequently transplanted organs. We have recently published that co-administration of Myeloid Progenitor (MP) and third party Hematopoietic Stem Cells (HSC) can induce MP-specific tolerance for subsequently transplanted organs [1].

METHODS

Mice received an allogeneic HSC and third party MP transplantation simultaneous with placement of a MP-matched skin graft. Variants tested include time of graft placement, MP genotype and source of cells.

RESULTS

Using B10;B6-Rag2(-/-)Il2rg(-/-) mice, we demonstrate that specific tolerance can be induced by MP given simultaneous with the skin graft in the complete absence of MP-donor-matched lymphoid cells. Ex vivo expanded MP function as well as sorted cells in inducing tolerance. In addition we demonstrate that tolerance can be induced by MP in the context of autologous HSC transplantation.

CONCLUSIONS

Our results demonstrate that the previously observed expansion of organ donor matched Treg is not essential for tolerance, and that MP tolerance protocols can be envisioned in most clinical settings, including those involving deceased donor organs.

Differential ability of surface and endosomal TLRs to induce CD8 T cell responses in vivo

TLR activation on dendritic cells (DCs) induces DC maturation and secretion of proinflammatory cytokines, both of which are important for activation and differentiation of CD4 T cells. The importance of TLR activation on DCs for CD8 T cell responses is less clear. In this study, we tested the ability of different TLRs to regulate CD8 T cell responses to pathogens. We found that although all TLRs are able to induce CD8 T cell activation in vitro, there are profound differences in their ability to activate CD8 T cells in vivo. The nucleic acid recognizing endosomal TLRs, TLR3 and TLR9, had a potent ability to induce CD8 T cell activation. However, the surface TLRs, TLR2 and TLR4, that recognize bacterial ligands were not only incapable of inducing CD8 T cell priming, but they had a dominant effect of inhibiting CD8 T cell expansion induced by activation of endosomal TLRs. We found that TLR2 and TLR4, acting in a MyD88-dependent manner, influenced CD8 T cell priming by altering the composition of DCs in the draining lymph nodes. Our results have important implications for combined bacterial and viral infections and suggest that bacterial infections could constrain the ability of the host to mount effective antiviral CD8 T cell immunity.

A phase II multicenter rabbit anti-thymocyte globulin trial in patients with myelodysplastic syndromes identifying a novel model for response prediction

Immune dysregulation is a mechanism contributing to ineffective hematopoiesis in a subset of myelodysplastic syndrome patients. We report the first US multicenter non-randomized, phase II trial examining the efficacy of rabbit(r)-anti-thymocyte globulin using 2.5 mg/kg/day administered daily for 4 doses. The primary end point was hematologic response; secondary end points included duration of response, time to response, time to progression, and tolerance. Nine (33%;95% confidence interval=17%-54%) of the 27 patients treated experienced durable hematologic improvement in an intent-to-treat analysis with a median time to response and median response duration of 75 and 245 days, respectively. While younger age is the most significant factor favoring equine(e)-anti-thymocyte globulin response, treatment outcome on this study was independent of age (P=0.499). A shorter duration between diagnosis and treatment showed a positive trend (P=0.18), but International Prognostic Scoring System score (P=0.150), karyotype (P=0.319), and age-adjusted bone marrow cellularity (P=0.369) were not associated with response classification. Since activated T-lymphocytes are the primary cellular target of anti-thymocyte globulin, a T-cell expression profiling was conducted in a cohort of 38 patients consisting of rabbit and equine-antithymocyte globulin-treated patients. A model containing disease duration, CD8 terminal memory T cells and T-cell proliferation-associated-antigen expression predicted response with the greatest accuracy using a leave-one-out cross validation approach. This profile categorized patients independent of other covariates, including treatment type and age using a leave-one-out-cross-validation approach (75.7%). Therefore, rabbit-anti-thymocyte globulin has hematologic remitting activity in myelodysplastic syndrome and a T-cell activation profile has potential utility classifying those who are more likely to respond (NCT00466843 clinicaltrials.gov).

Silibinin inhibits accumulation of myeloid-derived suppressor cells and tumor growth of murine breast cancer

Myeloid-derived suppressor cells (MDSC)s increase in blood and accumulate in the tumor microenvironment of tumor-bearing animals, contributing to immune suppression in cancer. Silibinin, a natural flavonoid from the seeds of milk thistle, has been developed as an anti-inflammatory agent and supportive care agent to reduce the toxicity of cancer chemotherapy. The goals of this study were to evaluate the effect of silibinin on MDSCs in tumor-bearing mice and antitumor activity of silibinin in a mouse model of breast cancer. 4T1 luciferase-transfected mammary carcinoma cells were injected into in the mammary fat pad female BALB/c mice, and female CB17-Prkdc Scid/J mice. Silibinin treatment started on day 4 or day 14 after tumor inoculation continued every other day. Tumor growth was monitored by bioluminescent imaging (BLI) measuring total photon flux. Flow cytometry measured total leukocytes, CD11b⁺ Gr-1⁺ MDSC, and T cells in the blood and tumors of tumor-bearing mice. The effects of silibinin on 4T1 cell viability in vitro were measured by BLI. Treatment with silibinin increased overall survival in mice harboring tumors derived from the 4T1-luciferase breast cancer cell line, and reduced tumor volumes and numbers of CD11b⁺Gr-1⁺ MDSCs in the blood and tumor, and increased the content of T cells in the tumor microenvironment. Silibinin failed to inhibit tumor growth in immunocompromised severe combined immunodeficiency mice, supporting the hypothesis that anticancer effect of silibinin is immune-mediated. The antitumor activity of silibinin requires an intact host immune system and is associated with decreased accumulation of blood and tumor-associated MDSCs.

Mycobacterium bovis BCG infection severely delays Trichuris muris expulsion and co-infection suppresses immune responsiveness to both pathogens

BACKGROUND

The global epidemiology of parasitic helminths and mycobacterial infections display extensive geographical overlap, especially in the rural and urban communities of developing countries. We investigated whether co-infection with the gastrointestinal tract-restricted helminth, Trichuris muris, and the intracellular bacterium, Mycobacterium bovis (M. bovis) BCG, would alter host immune responses to, or the pathological effect of, either infection.

RESULTS

We demonstrate that both pathogens are capable of negatively affecting local and systemic immune responses towards each other by modifying cytokine phenotypes and by inducing general immune suppression. T. muris infection influenced non-specific and pathogen-specific immunity to M. bovis BCG by down-regulating pulmonary TH1 and Treg responses and inducing systemic TH2 responses. However, co-infection did not alter mycobacterial multiplication or dissemination and host pulmonary histopathology remained unaffected compared to BCG-only infected mice. Interestingly, prior M. bovis BCG infection significantly delayed helminth clearance and increased intestinal crypt cell proliferation in BALB/c mice. This was accompanied by a significant reduction in systemic helminth-specific TH1 and TH2 cytokine responses and significantly reduced local TH1 and TH2 responses in comparison to T. muris-only infected mice.

CONCLUSION

Our data demonstrate that co-infection with pathogens inducing opposing immune phenotypes, can have differential effects on compartmentalized host immune protection to either pathogen. In spite of local and systemic decreases in TH1 and increases in TH2 responses co-infected mice clear M. bovis BCG at the same rate as BCG only infected animals, whereas prior mycobacterial infection initiates prolonged worm infestation in parallel to decreased pathogen-specific TH2 cytokine production.

Monocytic myeloid-derived suppressor cells accumulate in renal transplant patients and mediate CD4(+) Foxp3(+) Treg expansion

Myeloid-derived suppressor cells (MDSC) are negative regulators of the immune response and are in part responsible for the inhibition of the T cell-mediated immune responses. While MDSC have been demonstrated to participate in the induction of prolonged allograft survival in animal models of transplantation, little is known about their immune regulatory function in human transplant recipients. Here, we report that two subsets of human MDSC expressing CD11b(+), CD33(+) and HLA-DR(-) develop in renal patients posttransplantation. We found that CD14(+) expressing monocytic MDSC isolated from transplant recipients were highly efficient in suppressing the proliferation of CD4(+) T cells in mixed leukocyte reactions. In addition, we observed that CD11b(+) CD33(+) HLA-DR(-) MDSC are capable of expanding Treg in vitro, and their accumulation overtime after transplantation linearly correlated with an increase in Treg in vivo. This is the first study to link the presence of MDSC with the emergence of Treg in vivo in transplant recipients, and to define the subpopulation of MDSC derived from transplant recipients responsible for generation of Treg. Further studies are necessary to determine the alloimmune regulatory function of MDSC in human transplant recipients.

Properties of immature myeloid progenitors with nitric-oxide-dependent immunosuppressive activity isolated from bone marrow of tumor-free mice

Myeloid derived suppressor cells (MDSCs) from tumor-bearing mice are important negative regulators of anti-cancer immune responses, but the role for immature myeloid cells (IMCs) in non-tumor-bearing mice in the regulation of immune responses are poorly described. We studied the immune-suppressive activity of IMCs from the bone marrow (BM) of C57Bl/6 mice and the mechanism(s) by which they inhibit T-cell activation and proliferation. IMCs, isolated from BM by high-speed FACS, inhibited mitogen-induced proliferation of CD4(+) and CD8(+) T-cells in vitro. Cell-to-cell contact of T-cells with viable IMCs was required for suppression. Neither neutralizing antibodies to TGFβ1, nor genetic disruption of indolamine 2,3-dioxygenase, abrogated IMC-mediated suppressive activity. In contrast, suppression of T-cell proliferation was absent in cultures containing IMCs from interferon-γ (IFN-γ) receptor KO mice or T-cells from IFN-γ KO mice (on the C57Bl/6 background). The addition of NO inhibitors to co-cultures of T-cells and IMC significantly reduced the suppressive activity of IMCs. IFN-γ signaling between T-cells and IMCs induced paracrine Nitric Oxide (NO) release in culture, and the degree of inhibition of T-cell proliferation was proportional to NO levels. The suppressive activity of IMCs from the bone marrow of tumor-free mice was comparable with MDSCs from BALB/c bearing mice 4T1 mammary tumors. These results indicate that IMCs have a role in regulating T-cell activation and proliferation in the BM microenvironment.

T Cell Stimulatory Effects of Korean Red Ginseng through Modulation of Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) actively suppress immune cells and have been considered as an impediment to successful cancer immunotherapy. Many approaches have been made to overcome such immunosuppressive factors and to exert effective anti-tumor effects, but the possibility of using medicinal plants for this purpose has been overlooked. Korean red ginseng (KRG) is widely known to possess a variety of pharmacological properties, including immunoboosting and anti-tumor activities. However, little has been done to assess the anti-tumor activity of KRG on MDSCs. Therefore, we examined the effects of KRG on MDSCs in tumor-bearing mice and evaluated immunostimulatory and anti-tumor activities of KRG through MDSC modulation. The data show that intraperitoneal administration of KRG compromises MDSC function and induces T cell proliferation and the secretion of IL-2 and IFN-γ, while it does not exhibit direct cytotoxicity on tumor cells and reduced MDSC accumulation. MDSCs isolated from KRG-treated mice also express significantly lower levels of inducible nitric oxide synthase and IL-10 accompanied by a decrease in nitric oxide production compared with control. Taken together, the present study demonstrates that KRG enhances T cell function by inhibiting the immunosuppressive activity of MDSCs and suggests that although KRG alone does not exhibit direct anti-tumor effects, the use of KRG together with conventional chemo- or immunotherapy may provide better outcomes to cancer patients through MDSC modulation.

Immune heterogeneity in neuroinflammation: dendritic cells in the brain

Dendritic cells (DC) are critical to an integrated immune response and serve as the key link between the innate and adaptive arms of the immune system. Under steady state conditions, brain DC’s act as sentinels, continually sampling their local environment. They share this function with macrophages derived from the same basic hemopoietic (bone marrow-derived) precursor and with parenchymal microglia that arise from a unique non-hemopoietic origin. While multiple cells may serve as antigen presenting cells (APCs), dendritic cells present both foreign and self-proteins to naïve T cells that, in turn, carry out effector functions that serve to protect or destroy. The resulting activation of the adaptive response is a critical step to resolution of injury or infection and is key to survival. In this review we will explore the critical roles that DCs play in the brain’s response to neuroinflammatory disease with emphasis on how the brain’s microenvironment impacts these actions.

Immunotherapy of cancer: reprogramming tumor-immune crosstalk

The advancement of cancer immunotherapy faces barriers which limit its efficacy. These include weak immunogenicity of the tumor, as well as immunosuppressive mechanisms which prevent effective antitumor immune responses. Recent studies suggest that aberrant expression of cancer testis antigens (CTAs) can generate robust antitumor immune responses, which implicates CTAs as potential targets for immunotherapy. However, the heterogeneity of tumor cells in the presence and quantity of CTA expression results in tumor escape from CTA-specific immune responses. Thus, the ability to modulate the tumor cell epigenome to homogenously induce expression of such antigens will likely render the tumor more immunogenic. Additionally, emerging studies suggest that suppression of antitumor immune responses may be overcome by reprogramming innate and adaptive immune cells. Therefore, this paper discusses recent studies which address barriers to successful cancer immunotherapy and proposes a strategy of modulation of tumor-immune cell crosstalk to improve responses in carcinoma patients.

Targeting myeloid-derived suppressor cells augments antitumor activity against lung cancer

Lung cancer evades host immune surveillance by dysregulating inflammation. Tumors and their surrounding stromata produce growth factors, cytokines, and chemokines that recruit, expand, and/or activate myeloid-derived suppressor cells (MDSCs). MDSCs regulate immune responses and are frequently found in malignancy. In this review the authors discuss tumor-MDSC interactions that suppress host antitumor activities and the authors’ recent findings regarding MDSC depletion that led to improved therapeutic vaccination responses against lung cancer. Despite the identification of a repertoire of tumor antigens, hurdles persist for immune-based anticancer therapies. It is likely that combined therapies that address the multiple immune deficits in cancer patients will be required for effective therapy. MDSCs play a major role in the suppression of T-cell activation and they sustain tumor growth, proliferation, and metastases. Regulation of MDSC recruitment, differentiation or expansion, and inhibition of the MDSC suppressive function with pharmacologic agents will be useful in the control of cancer growth and progression. Pharmacologic agents that regulate MDSCs may be more effective when combined with immunotherapies. Optimization of combined approaches that simultaneously downregulate MDSC suppressor pathways, restore APC immune-stimulating activity, and expand tumor-reactive T cells will be useful in improving therapy.