scholarly journals Expansion of Myeloid-Derived Suppressor Cells in Patients with Acute Coronary Syndrome

2015 ◽  
Vol 35 (1) ◽  
pp. 292-304 ◽  
Author(s):  
Yan-ge Wang ◽  
Xin Xiong ◽  
Zhu-yue Chen ◽  
Kan-ling Liu ◽  
Jin-hua Yang ◽  
...  
Keyword(s):  
Acute Coronary Syndrome ◽  
Plasma Levels ◽  
Suppressor Cells ◽  
Myeloid Derived Suppressor Cells ◽  
Suppressive Function ◽  
Coronary Syndrome ◽  
Arginase 1 ◽  
Hla Dr ◽  
Tnf Α ◽  
And Function

Aim: The aim of this study was to explore whether the circulating frequency and function of myeloid-derived suppressor cells (MDSCs) are altered in patients with acute coronary syndrome (ACS). Methods: The frequency of MDSCs in peripheral blood was determined by flow cytometry, and mRNA expression in purified MDSCs was analyzed by real-time reverse transcription polymerase chain reaction (RT-PCR). The suppressive function of MDSCs isolated from different groups was also determined. The plasma levels of certain cytokines were determined using Bio-Plex Pro™ Human Cytokine Assays. Results: The frequency of circulating CD14+HLA-DR-/low MDSCs; arginase-1 (Arg-1) expression; and plasma levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and IL-33 were markedly increased in ACS patients compared to stable angina (SA) or control patients. Furthermore, MDSCs from ACS patients were more potent suppressors of T-cell proliferation and IFN-γ production than those from the SA or control groups at ratios of 1:4 and 1:2; this effect was partially mediated by Arg-1. In addition, the frequency of MDSCs was positively correlated with plasma levels of IL-6, IL-33, and TNF-α. Conclusions: We observed an increased frequency and suppressive function of MDSCs in ACS patients, a result that may provide insights into the mechanisms involved in ACS.

scholarly journals Increased Levels of Granulocytic Myeloid-Derived Suppressor Cells in Peripheral Blood and Tumour Tissue of Pancreatic Cancer Patients

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Yazan S. Khaled ◽  
Basil J. Ammori ◽  
Eyad Elkord
Keyword(s):  
Pancreatic Cancer ◽  
Suppressor Cells ◽  
Blood Levels ◽  
Myeloid Derived Suppressor Cells ◽  
Arginase 1 ◽  
Hla Dr ◽  
Healthy Donors ◽  
And Function ◽  
Immunosuppressive Cells

Pancreatic cancer (PC) often presents late with poor survival. While role of immunosuppressive cells in preclinical studies provided help to develop immunotherapeutic agents, these cells remain under investigation in PC. The aim of this study was to characterise the different subsets of myeloid-derived suppressor cells (MDSCs) and evaluate their level and function in the circulation and tissue of PC patients. Significant increases in circulating and tumour-infiltrating granulocytic (Lin-HLA-DR-CD33+CD11b+CD15+), but not monocytic (Lin-HLA-DR-CD14+), MDSCs were detected in PC patients when compared with healthy donors and patients with chronic pancreatitis. The circulating MDSCs from PC patients expressed arginase 1, which represents their functional state. Blood levels of MDSCs showed no association with PC stage or preoperative levels of tumour markers. These findings provide a first characterisation of the phenotype of different subsets of peripheral and local MDSCs in PC patients and suggest that the frequency and contribution of these cells are predominantly granulocytic. This information demonstrates that MDSCs play a role in pancreatic cancer and future large validation studies may help in the development of new immunotherapeutic strategies to inhibit or eliminate MDSC function.

Myeloid-Derived Suppressor Cells (MDSC) Are Effectors of Bone Marrow Suppression in Lower Risk Myelodysplastic Syndromes (MDS).

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 597-597 ◽  
Author(s):  
Sheng Wei ◽  
Xianghong Chen ◽  
Kathy Rocha ◽  
Dahui Qi ◽  
Jianguo Tao ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Population ◽  
Lower Risk ◽  
Chromosomal Abnormalities ◽  
Adaptor Protein ◽  
Suppressor Cells ◽  
Myeloid Derived Suppressor Cells ◽  
Suppressive Function ◽  
Hla Dr ◽  
Facs Sorting

Abstract Abstract 597 The acquisition of genetic abnormalities that lead to ineffective hematopoiesis is a characteristic of MDS. This event is mediated in part by an interaction of inflammatory intermediates with the bone marrow (BM) microenvironment; however, the mechanism by which chromosomal damage occurs to the stem/progenitor compartment (HSC/HPC) is unknown. We have identified a unique population of myeloid derived suppressor cells (MDSC) bearing a LIN-HLA-DR-CD33+ surface phenotype. These MDSC elicit hematopoietic suppression through the elaboration of nitric oxide, arginase, and inflammatory cytokines. This study found that MDSCs accumulated in excess in the BM of patients with lower risk MDS (mean, 32.32% ± 13.3; n=12) compared to BM from healthy age matched controls (mean 2.1%±0.9; n=8) and non-MDS cancer patients (n=8 mean 2.06%±1.5 p<0.0001). Fluorescence in situ hybridization (FISH) was performed to determine whether MDSCs represent a distinct cell population from the abnormal MDS clone. MDSCs from BM of 5 patients having chromosomal abnormality were separated by FACS sorting based on LIN-HLA-DR-CD33+ phenotype and the presence of chromosomal abnormalities was determined in this population and compared to non-MDSCs. Monosomy 7 and deletion of 5q chromosomal abnormalities resided within the non-MDSC hematopoietic compartment. This indicates that MDSCs in low risk MDS patients may represent a unique cell population from the HPCs with clonal potential. Furthermore, the key cytokines involved in MDSC suppressive function, TGFβ, VEGF and IL-10, were higher in MDSCs isolated from MDS patients compared to controls. Using four-color immunostaining, we discovered that MDSCs are capable of direct cytotoxicity against autologous erythroid precursors (CD71+ and CD235a+), as evidenced by increased polarized granule mobilization toward the site of cellular contact. Moreover, it was observed that the accumulation of MDSC in the BM from MDS patients has an impact on hematopoietic differentiation. In the presence of MDSCs, the formation of BFU-E (burst forming unit erythroid) was significantly suppressed in all patients tested (n=6). In contrast depletion of the MDSC by FACS sorting reconstituted the formation of BFU-E (21± 4.2 in MDSC depleted bone marrow verse 0.8± 0.6 in unsorted BM cells, respectively). These data strongly suggest that the presence of MDSCs in the BM microenvironment of MDS patients contribute to suppression of HPC development. Based on these findings, a novel form of adaptive immunotherapy based on the induction of MDSC maturation can be envisioned. DAP12 (DNAX-activating protein of 12kDa) is an adaptor protein that mediates signaling of dentritic cell and monocyte maturation. In order to determine if DAP12 signaling induces MDSC maturation and reversal of suppressive function, a genetically modified, constitutively activated form was introduced into BM mononuclear cells (BM-MNC) using both recombinant adenoviral and lentiviral gene transduction. Infection of BM-MNC from MDS patients with constitutively active DAP12 increased expression of maturation surface markers CD14, CD15 and HLA-DR and increased BFU-E colony formation (31± 2.1 verse control 7±0.7) after 14 days. These results suggest that active signaling through DAP12 has potential therapeutic implications in MDS by driving maturation of immature myeloid cells reversing the inflammatory changes that contribute to malignant transformation. In conclusion, our previously unknown findings have begun to elucidate whether the presence of MDSCs in the BM microenvironment of MDS patients contributes to the pathogenesis of MDS by providing a suppressive microenvironment and repress BM maturation associated with impaired HSC/HPC development. Additionally, DAP12 may be a potential therapeutic pathway in which to stimulate MDSC maturation, reversing the suppressive effects on HSC/HPC development. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Interleukin-7 and interleukin-15 drive CD4+CD28null T lymphocyte expansion and function in patients with acute coronary syndrome

2020 ◽  
Author(s):  
Jessica Bullenkamp ◽  
Veronica Mengoni ◽  
Satdip Kaur ◽  
Ismita Chhetri ◽  
Paraskevi Dimou ◽  
...  
Keyword(s):  
T Cells ◽  
Acute Coronary Syndrome ◽  
T Cell ◽  
T Lymphocyte ◽  
Cell Expansion ◽  
Cell Subset ◽  
Coronary Syndrome ◽  
Tnf Α ◽  
T Cell Expansion ◽  
And Function

Abstract Aims Inflammation has important roles in atherosclerosis. CD4+CD28null (CD28null) T cells are a specialized T lymphocyte subset that produce inflammatory cytokines and cytotoxic molecules. CD28null T cells expand preferentially in patients with acute coronary syndrome (ACS) rather than stable angina and are barely detectable in healthy subjects. Importantly, ACS patients with CD28null T-cell expansion have increased risk for recurrent acute coronary events and poor prognosis, compared to ACS patients in whom this cell subset does not expand. The mechanisms regulating CD28null T-cell expansion in ACS remain elusive. We therefore investigated the role of cytokines in CD28null T-cell expansion in ACS. Methods and results High-purity sorted CD4+ T cells from ACS patients were treated with a panel of cytokines (TNF-α, IL-1β, IL-6, IL-7, and IL-15), and effects on the number, phenotype, and function of CD28null T cells were analysed and compared to the control counterpart CD28+ T-cell subset. IL-7- and IL-15-induced expansion of CD28null T cells from ACS patients, while inflammatory cytokines TNF-α, IL-1β, and IL-6 did not. The mechanisms underlying CD28null T-cell expansion by IL-7/IL-15 were preferential activation and proliferation of CD28null T cells compared to control CD28+ T cells. Additionally, IL-7/IL-15 markedly augmented CD28null T-cell cytotoxic function and interferon-γ production. Further mechanistic analyses revealed differences in baseline expression of component chains of IL-7/IL-15 receptors (CD127 and CD122) and increased baseline STAT5 phosphorylation in CD28null T cells from ACS patients compared to the control CD28+ T-cell subset. Notably, we demonstrate that CD28null T-cell expansion was significantly inhibited by Tofacitinib, a selective JAK1/JAK3 inhibitor that blocks IL-7/IL-15 signalling. Conclusion Our novel data show that IL-7 and IL-15 drive the expansion and function of CD28null T cells from ACS patients suggesting that IL-7/IL-15 blockade may prevent expansion of these cells and improve patient outcomes.

scholarly journals Stroke-Induced Modulation of Myeloid-Derived Suppressor Cells (MDSCs) and IL-10-Producing Regulatory Monocytes

2020 ◽  
Vol 11 ◽  
Author(s):  
Lennart Achmus ◽  
Johanna Ruhnau ◽  
Sascha Grothe ◽  
Bettina von Sarnowski ◽  
Barbara M. Bröker ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Geometric Mean ◽  
Suppressor Cells ◽  
Interleukin 10 ◽  
Experimental Stroke ◽  
Myeloid Derived Suppressor Cells ◽  
Stroke Patients ◽  
Post Stroke ◽  
Arginase 1 ◽  
Hla Dr

Background: Stroke patients are at risk of acquiring secondary infections due to stroke-induced immune suppression (SIIS). Immunosuppressive cells comprise myeloid-derived suppressor cells (MDSCs) and immunosuppressive interleukin 10 (IL-10)-producing monocytes. MDSCs represent a small but heterogeneous population of monocytic, polymorphonuclear (or granulocytic), and early progenitor cells (“early” MDSC), which can expand extensively in pathophysiological conditions. MDSCs have been shown to exert strong immune-suppressive effects. The role of IL-10-producing immunosuppressive monocytes after stroke has not been investigated, but monocytes are impaired in oxidative burst and downregulate human leukocyte antigen—DR isotype (HLA-DR) on the cell surface.Objectives: The objective of this work was to investigate the regulation and function of MDSCs as well as the immunosuppressive IL-10-producing monocytes in experimental and human stroke.Methods: This longitudinal, monocentric, non-interventional prospective explorative study used multicolor flow cytometry to identify MDSC subpopulations and IL-10 expression in monocytes in the peripheral blood of 19 healthy controls and 27 patients on days 1, 3, and 5 post-stroke. Quantification of intracellular STAT3p and Arginase-1 by geometric mean fluorescence intensity was used to assess the functionality of MDSCs. In experimental stroke induced by electrocoagulation in middle-aged mice, monocytic (CD11b+Ly6G−Ly6Chigh) and polymorphonuclear (CD11b+Ly6G+Ly6Clow) MDSCs in the spleen were analyzed by flow cytometry.Results: Compared to the controls, stroke patients showed a relative increase in monocytic MDSCs (percentage of CD11b+ cells) in whole blood without evidence for an altered function. The other MDSC subgroups did not differ from the control. Also, in experimental stroke, monocytic, and in addition, polymorphonuclear MDSCs were increased. The numbers of IL-10-positive monocytes did not differ between the patients and controls. However, we provide a new insight into monocytic function post-stroke since we can report that a differential regulation of HLA-DR and PD-L1 was found depending on the IL-10 production of monocytes. IL-10-positive monocytes are more activated post-stroke, as indicated by their increased HLA-DR expression.Conclusions: MDSC and IL-10+ monocytes can induce immunosuppression within days after stroke.

Dendritic Cell Vaccination in Acute Leukemia Patients Induces Reduction of Myeloid-Derived Suppressor Cells : Immunological Analysis of a Pilot Study

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1113-1113 ◽  
Author(s):  
Masahiro Ogasawara ◽  
Shuichi Ota
Keyword(s):  
T Cells ◽  
Acute Leukemia ◽  
Suppressor Cells ◽  
Absolute Number ◽  
The Other ◽  
Myeloid Derived Suppressor Cells ◽  
Arginase 1 ◽  
Hla Dr ◽  
Healthy Donors ◽  
Before And After

Abstract Background and Purpose: Myeloid-derived suppressor cells (MDSC) are a heterogeneous cell population that have an immunesuppresive function and play an important role in tumor immunology and self tolerance. Elevated levels of MDSCs in peripheral blood (PB) are reported in various cancers and hematological malignancies such as MDS, NHL and MM. We reported that vaccination with Wilms’ tumor 1 (WT1) peptide-pulsed dendritic cells (DC) in NHL patients induced not only WT1 specific immune responses but also innate immunity which correlated with clinical efficacy (ASH 2013). In the present study, we focused on MDSCs and investigated the effects of DC vaccination on the alteration of MDSCs which have negative influence on disease progression. Patients and Methods: 8 patients with acute leukemia (6 AML and 2ALL patients; aged 16-77) who were treated with WT1 peptide-loaded DC vaccination were enrolled in the present study. MDSCs were analyzed by FACS. Linage negative, CD11b+CD33+HLA-DR- cells were defined as MDSC. Monocytic and granulocytic MDSC were defined as CD14+HLA-DRlow/- and CD15+CD11b+CD33+HLA-DR-, respectively. For proliferation assay, CD14+DR- cells and CD3+ T cells were isolated by magnetic beads method. CFSE-labeled CD3+ T cells were stimulated with anti-CD3 and anti-CD28 moAb together with IL-2 in the presence or absence of CD14+DR-cells for 4 days and cell division was analyzed by FACS. Cytoplasmic staining of indoleamine 2,3-deoxygenase (IDO) and arginase 1 were performed by permeabilization using saponin followed by moAb staining. Arginase 1 protein levels in plasma was assessed using a commercially available ELISA kit. Results: 3 patients were in complete remission (responder) and 5 others were in disease progression (non-responder) following one course of vaccination. WT1 specific T cell responses evaluated by a HLA-tetramer assay and a delayed type hypersensitivity (DTH) test were observed in all the responders and 2 non-responders. Mean percentage of MDSCs, monocytic and granulocytic MDSCs in PB was higher in acute leukemia patients than in healthy donors (1.60±0.72%, 16.56±6.07%, 1.34±0.69%, respectively in patients; 0.60±0.31%, 13.1±4.1%, 0.37±0.1%, respectively in healthy donors). Absolute number of circulating monocytic and granulocytic MDSCs before and after vaccination in responders was 359.4±117.8/μl and 35.2±14.8/μl, 282.8±119.2 /μl and 14.4±12.0/μl, respectively. On the other hand, those in non-responders were 126.3±60.2/μl and 36.3±21.7/μl, 181.3±124.0/μl and 65.1±12.0/μl, respectively. While DC vaccination resulted in reduction of both monocytic and granulocytic MDSCs by 21.3% and 59.1%, respectively in responders, it induced augmentation of these MDSCs by 43.5% and 79.3%, respectively in non-responders. A portion of MDSCs expressed IDO and arginase 1 in cytoplasm. While the percentage of IDO positive cells in monocytic MDSCs increased by 2.2 and 2.3 times in responders and non-responders, respectively following vaccination, the positivity of arginase 1 decreased by 59% in responders. On the other hand, the positivity of IDO and arginase 1 in granulocytic MDSCs decreased at the same level in both responders and non-responders following vaccination. CD14+DR-cells inhibited the proliferation of CD3+ T cells in a dose dependent manner, indicating that these cells share characteristics of MDSCs. The inhibition of the proliferation of CD3+T cells was partially restored by the addition of 1-methyl-DL-tryptophan (IDO inhibitor) and Nω-hydroxy-nor-arginine (arginase 1 inhibitor), suggesting that the inhibition was mediated at least in part by IDO and arginase 1. Amount of arginase 1 in the plasma before and after vaccination decreased by 25% in responders, not in non-responders. Conclusions: These results demonstrated that DC vaccination resulted in the reduction of the absolute number of MDSCs which seems to be correlated with clinical efficacy. DC vaccination may have inhibitory effects on several functions of MDSCs that can suppress immune surveillance against leukemia, which is favorable for regression of leukemia cells. Disclosures No relevant conflicts of interest to declare.

Dynamic Change and Impact of Circulating Myeloid-Derived Suppressor Cells in Patients Following Allogeneic Hematopoietic Stem Cell Transplantation

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5472-5472
Author(s):  
Jin Yin ◽  
Yicheng Zhang
Keyword(s):  
Stem Cell ◽  
Hematopoietic Stem Cell Transplantation ◽  
Suppressor Cells ◽  
Myeloid Derived Suppressor Cells ◽  
Dynamic Changes ◽  
Hematopoietic Stem ◽  
Hla Dr ◽  
Tnf Α ◽  
Normal Controls

Abstract Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population involved in tumor-associated immunosuppression and played immune regulatory roles in malignancies, infectious disease, autoimmune disease, trauma and inflammatory disease. Based on the significant suppressive functions, MDSCs raises great interests in the field of allogenetic hematopoietic stem cell transplantation (allo-HSCT) and graft-versus-host disease (GVHD). In recent years, studies described the immunosuppressive functions of CD14+HLA-DR-/low MDSCs, one of the few well-characterized MDSC subsets in human. However, the studies in patients with allo-HSCT are still scanty. This study identified the phenotype of CD14+HLA-DR-/low MDSCs and systematically monitored the dynamic changes of MDSCs accumulation in patients during the first 100 days after allo-HSCT in order to evaluate possible effects of MDSCs on aGVHD development and clinical outcomes. We also detected the frequencies of other cell types and concentrations of relative cytokines during MDSCs accumulation. Results showed that accumulation of MDSCs in the graft and in peripheral blood when engraftment might contribute to patients' overall immune suppression and result in the successful control of severe aGVHD and long-term survival without influence on risk of recurrence after allo-HSCT. However, the level of MDSCs in the graft had more favorable predictive abilities compared with that in PBMCs when engraftment. Furthermore, MDSCs frequencies were significantly increased in patients developing aGVHD after allo-HSCT. In the patients with mild aGVHD (0-2), MDSCs accumulated at the time of engraftment after allo-HSCT and decreased to basal levels at about 4 weeks. MDSCs frequencies would keep in stable levels with slight fluctuations in the following weeks. But, in patients with severe aGVHD (3-4), MDSCs elevated slightly when engraftment. When aGVHD occurred, MDSCs frequencies would significantly increase. And a synchronized reduction of the levels of MDSCs was observed after effective management of aGVHD with immunosuppressive therapy. Besides, the levels of IL-10, IL-6, TNF-α, Arg-1, iNOS and HO-1 increased greatly both in patients with aGVHD and in high MDSCs group. It is speculated that MDSC accumulation at the onset of aGVHD might be caused by secondary inflammatory response, especially related to high concentrations of IL-6 and TNF-α. But the accumulation would not be able to counterbalance the aggravation of aGVHD and would not have influence on clinical outcomes and risk of relapse in future. Overall, we suggested that MDSCs might be considered as a potential new approaches to regulate transplant rejection and achieve the recipient host long-term acceptance and survival. Figure 1. Frequencies of cell subsets in the graft. Frequencies of MDSCs in the graft were compared between normal controls and patients grouped by aGVHD (i) and aGVHD scores Figure 1. Frequencies of cell subsets in the graft. Frequencies of MDSCs in the graft were compared between normal controls and patients grouped by aGVHD (i) and aGVHD scores Figure 2. Increased frequencies of MDSCs in PBMCs of patients after allo-HSCT. (A) At the time of engraftment, the levels of MDSCs in PBMCs were compared between patients and normal controls (i), and were further analyzed according to aGVHD scores (ii). (B) After allo-HSCT, comparisons of MDSCs frequencies were performed between patients and normal controls grouped by aGVHD (i) and aGVHD severity (ii). (C) The dynamic changes of MDSCs frequencies after allo-HSCT were monitored in patients with aGVHD (i) and were analyzed based on aGVHD scores (ii). (D) The systematic monitoring of MDSCs frequencies was performed in all patients during the first 100 days after allo-HSCT grouped by aGVHD scores (i) and aGVHD severity (ii). Figure 2. Increased frequencies of MDSCs in PBMCs of patients after allo-HSCT. (A) At the time of engraftment, the levels of MDSCs in PBMCs were compared between patients and normal controls (i), and were further analyzed according to aGVHD scores (ii). (B) After allo-HSCT, comparisons of MDSCs frequencies were performed between patients and normal controls grouped by aGVHD (i) and aGVHD severity (ii). (C) The dynamic changes of MDSCs frequencies after allo-HSCT were monitored in patients with aGVHD (i) and were analyzed based on aGVHD scores (ii). (D) The systematic monitoring of MDSCs frequencies was performed in all patients during the first 100 days after allo-HSCT grouped by aGVHD scores (i) and aGVHD severity (ii). Disclosures No relevant conflicts of interest to declare.

501 VISTA regulates the differentiation and suppressive function of myeloid-derived suppressor cells

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A536-A536
Author(s):  
Juan Dong ◽  
Cassandra Gilmore ◽  
Hieu Ta ◽  
Keman Zhang ◽  
Sarah Stone ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Signaling Pathways ◽  
Immune Checkpoint ◽  
Suppressor Cells ◽  
Myeloid Cell ◽  
Myeloid Derived Suppressor Cells ◽  
Checkpoint Protein ◽  
Suppressive Function

BackgroundV-domain immunoglobulin suppressor of T cell activation (VISTA) is a B7 family inhibitory immune checkpoint protein and is highly expressed on myeloid cells and T cells.1 VISTA acts as both an inhibitory ligand when expressed on antigen-presenting cells and a receptor when expressed on T cells. Our recent study has shown that VISTA is a myeloid cell-specific immune checkpoint and that blocking VISTA can reprogram suppressive myeloid cells and promote a T cell-stimulatory tumor microenvironment.2 In this study, we further demonstrate that VISTA blockade directly alters the differentiation and the suppressive function of myeloid-derived suppressor cells (MDSC).MethodsFlow cytometry was performed to examine VISTA expression on MDSCs in multiple murine tumor models including the B16BL6 melanoma model, MC38 colon cancer model, and the KPC pancreatic cancer models. To examine the role of VISTA in controlling the differentiation and suppressive function of MDSCs, we cultured wild type (WT) and VISTA.KO bone marrow progenitor cells with GM-CSF and IL-6 to induce BM -derived MDSCs.ResultsOur preliminary results show that VISTA is highly expressed on M-MDSCs in B16BL6, MC38 and KPC tumors. In BM-derived MDSCs, VISTA deletion significantly altered the signaling pathways and the differentiation of MDSCs. Multiple inflammatory signaling pathways were downregulated in VISTA KO MDSCs, resulting in decreased production of cytokines such as IL1 and chemokines such as CCL2/4/9, as well as significantly impaired their ability to suppress the activation of CD8+ T cells. The loss of suppressive function in VISTA KO MDSCs is correlated with significantly reduced expression of iNOS. To validate the results from BM-MDSCs, we sorted CD11b+CD11c-Ly6C+Ly6G- M-MDSCs and CD11b+CD11c-Ly6G+ G-MDSCs from B16BL6 tumor tissues and tested the ability of a VISTA-blocking mAb to reverse the suppressive effects of tumor-derived MDSCs. Our results show that blocking VISTA impaired the suppressive function of tumor-derived M-MDSC but not G-MDSCs.ConclusionsTaken together, these results demonstrate a crucial role of VISTA in regulating the differentiation and function of MDSCs, and that blocking VISTA abolishes MDSC-mediated T cell suppression, thereby boosting.Ethics ApprovalAll in vivo studies were reviewed and approved by Institutional Animal Care and Use Committee (Approval number 2019-2142).ReferencesXu W, Hire T, Malarkannan, S. et al. The structure, expression, and multifaceted role of immune-checkpoint protein VISTA as a critical regulator of anti-tumor immunity, autoimmunity, and inflammation. Cell Mol Immunol 2018;15:438–446.Xu W, Dong J, Zheng Y, et al. Immune-checkpoint protein VISTA regulates antitumor immunity by controlling myeloid cell-mediated inflammation and immunosuppression. Cancer Immunol Res 2019;7:1497–510.

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