Myeloid-derived Suppressor Cells In Patients Research Articles

The diversity of peripheral blood T cells and myeloid-derived suppressor cells in patients with idiopathic membranous nephropathy.

Membranous nephropathy is a leading cause of adult-onset nephrotic syndrome. Peripheral T cells and myeloid-derived suppressor cells (MDSCs) are closely associated with autoimmune diseases, while their exact roles and interaction in these processes are unclear. Here, we studied the roles of T cells, MDSCs, and their subsets in patients with idiopathic membranous nephropathy (IMN). 35 IMN patients and 30 healthy controls were included in this retrospective study. Flow cytometry was performed to determine the phenotype of human T cells and MDSCs in peripheral blood mononuclear cells (PBMCs). Anti-PLA2R was measured by ELISA. Values ≥ 20 RU/mL were defined as positive and < 14 RU/mL as negative. A higher ratio of CD4/CD8 T cells with a lower proportion of Tregs, a remarkably lower proportion of G-MDSCs (but not M-MDSCs), lower frequency of PD-L2+G-MDSCs, and higher frequency of PD-L1+M-MDSCs were found in IMN patients compared to healthy controls. The ratio of CD4/CD8 T cells was higher, and the frequencies of PD-1+CD4+ T cells, CTLA-4+CD4+ T cells, PD-1+Tregs, and CTLA-4+Tregs were lower in PBMCs of PLA2R-positive IMN patients compared to PLA2R-negative IMN patients. Tregs and G-MDSCs were reduced in the circulation of the IMN patients, which may promote understanding of the crucial functions that are mediated by these cells in the pathogenesis of IMN.

Targeting myeloid-derived suppressor cells by inhibiting hypoxia-inducible factor 1α could improve tumor progression.

Myeloid-derived suppressor cells (MDSCs) are a subset of immature myeloid cells that inhibit anti-tumor immunity and contribute to poor cancer outcomes. In this study, the authors used multi-color flow cytometry to detect changes in MDSCs in patients with cancer and tumor-bearing mice. Then the authors studied changes in MDSCs ratio and mouse tumors after administration of hypoxia-inducible factor 1α (HIF-1α) inhibitor. The results showed that the ratio of MDSCs, specifically polymorphonuclear MDSCs (PMN-MDSCs), was higher in patients with cancer, and both PMN-MDSCs and monocytic MDSCs (M-MDSCs) ratio were higher in tumor-bearing mice. When provided with the HIF-1α inhibitor LW-6, the ratio of MDSCs decreased in tumor-bearing mice, particularly PMN-MDSCs, and the volume of liver metastases also decreased. The authors' findings suggest that reducing MDSCs by inhibiting hypoxia-inducible factor 1α may slow tumor progression.

Evaluating Leukocyte Telomere Length and Myeloid-Derived Suppressor Cells as Biomarkers for Prostate Cancer.

Leukocyte telomere length (LTL) and myeloid-derived suppressor cells (MDSC) are associated with aging and the development and progression of cancer. However, the exact nature of this relationship remains unclear. Our study aimed to investigate the potential of LTL and MDSC as diagnostic biomarkers for prostate cancer while also seeking to deepen our understanding of the relationship of these potential biomarkers to each other. Our study involved patients undergoing a prostate biopsy. We analyzed the relative LTL in genomic DNA obtained from peripheral blood leukocytes as well as the percentage of MDSC and their subtypes in peripheral blood mononuclear cells (PBMC). Our evaluation focused on examining the relationship between LTL and MDSC and pathological diagnoses as well as investigating the correlation between LTL and MDSC levels. In our study of 102 participants, 56 were pathologically diagnosed with localized prostate cancer (cancer group), while 46 tested negative (control group). The cancer group exhibited significantly shorter LTL in comparison to the control group (p = 0.024). Additionally, the cancer group showed a tendency towards a higher percentage of monocytic MDSC (M-MDSC), although this difference did not reach statistical significance (p = 0.056). Our multivariate logistic regression analysis revealed that patients with shorter LTL and higher percentages of M-MDSC had a 2.98-fold (95% CI = 1.001-8.869, p = 0.049) and 3.03-fold (95% CI = 1.152-7.977, p = 0.025) increased risk of prostate cancer diagnosis, respectively. There was also a significant negative correlation between LTL and M-MDSC. (r = -0.347, p < 0.001). Our research has established a correlation between LTL and MDSC in patients undergoing biopsy for prostate cancer. Notably, we observed that individuals with localized prostate cancer tend to have shorter LTL and a higher percentage of M-MDSC prior to their diagnosis. These findings suggest that LTL and M-MDSC could potentially serve as adjunctive biomarkers for the early diagnosis of prostate cancer.

Effect of thymalfasin on myeloid-derived suppressor cells in patients with non-small cell lung cancer.

To observe the effect of thymalfasin on myeloid-derived suppressor cells (MDSCs) subsets in peripheral blood of patients with non-small cell lung cancer (NSCLC). 50 cases of NSCLC (NSCLC group) diagnosed in Chest Hospital of Jiangxi Province were selected as the research subjects, and 50 healthy subjects who underwent physical examination in our hospital during the same period were selected as the healthy control group. The expression of HLA-DR-CD14-CD33+ MDSCs in peripheral blood mononuclear cells and tumor tissue single cell suspension of NSCLC patients before and after thymalfasin treatment was explored by flow cytometry. The proportion of MDSCs in peripheral blood of NSCLC group was 1.70±0.52%, which was significantly higher than that in peripheral blood (0.51±0.15%) of healthy controls (P < 0.05). The proportion of HLA-DR-CD14-CD33+ MDSCs in the tissues of NSCLC group was 1.65±0.43% before treatment and 1.15±0.50% after treatment (P < 0.05). The proportion of MDSCs in peripheral blood of NSCLC patients before treatment was 1.70±0.52%, and that after treatment was 0.59±0.18% (P < 0.05). Thymalfasin can reduce the number of MDSCs in peripheral blood mononuclear cells. The application of thymalfasin in the treatment of NSCLC patients can help to enhance the anti-tumor effect.

MYELOID-DERIVED SUPPRESSOR CELLS TWO YEARS AFTER HEPATITIS C VIRUS ERADICATION USING DIRECTLY ACTING ANTIVIRALS.

Myeloid-derived suppressor cells (MDSCs) have immature morphology, relatively weak phagocytic activity, as well as some immunosuppressive functions. The capacity of MDSCs to inhibit T-cell-mediated immunological responses is their most notable functional characteristic. Down-regulating antitumor immune surveillance is one way that the expansion and activation of MDSCs contribute significantly to the occurrence and progression of tumors. Increased levels of MDSCs in patients with chronic hepatitis C virus (HCV) infection could suppress T-cell responses, promoting viral escape and hepatitis progression. This may make HCV-infected individuals more vulnerable to severe infections, hepatic and extra-hepatic tumors, and a diminished capacity to react to immunization. It is still unknown if effective HCV eradication with directly acting antivirals (DAAs) can restore immune functions and immune surveillance capacity. The purpose of this study was to observe the frequency of M-MDSCs (CD33+, CD11b+, and HLA-DR) in patients with a previous history of HCV, 2-3 years after virus eradication using DAA therapy. This study was conducted on 110 subjects: fifty-five subjects without liver cirrhosis who were treated with HCV using DAAs and attained SVR for a period of 2-3 years and 55 age- and gender-matched healthy controls. The study was conducted during the period from January to July 2022. Patients were recruited from the National Viral Hepatitis Treatment Unit, Alexandria University Hepatology outpatient clinic, and the Alexandria University Tropical Medicine outpatient clinic. The frequencies of MDSCs (CD33+CD11b + HLA-DR-) by flow cytometry were assessed. Even after the virus had been eradicated for longer than two years, MDSC levels in HCV-treated individuals were found to be considerably higher. In the HCV-treated group, the median number of MDSCs was 5, with an interquartile range (IQR) of 3.79-7.69. In contrast, the median for the control group was 3.1, with an IQR of 1.4-3.2 (P˂0.001). Successful DAA therapy leads to slow and partial immunological reconstitution, as demonstrated by the failure to attain normal levels of MDSC's 2 years after successful HCV eradication despite the normalization of laboratory parameters as well as the absence of liver fibrosis. The clinical implications of these findings should be thoroughly studied.

Content of myeloid-derived suppressor cells in autoimmune diseases in children

Myeloid-derived suppressor cells (MDSCs) play an important role in regulation of immune response. An increase in their number in adult patients with autoimmune diseases has been reported. G-MDSCs, M-MDSCs, and MDSCs(M-G-) at different stages of autoimmune disease may both activate T cell proliferation, leading to disease progression, or inhibit it, thus promoting Treg differentiation. Arginase-1 (Arg- 1) is an enzyme in MDSCs that reduces the concentration of arginine required for T lymphocyte proliferation. Our aim was to evaluate the content of MDSCs populations and functional activity of MDSCs in children with autoimmune diseases. 75 children with inflammatory bowel diseases (IBD), 60 children with multiple sclerosis (MS), 69 children with psoriasis (PS), 62 healthy age-matched children were included into the study. The content of MDSCs ((CD3, CD19, CD56, HLA-DR)-, CD11b+ and CD33+), subpopulations of MDSCs (M-MDSCs, G-MDSCs expressing CD14 and CD15), assessment of Arg-1 activity were performed by flow cytometry techniques. The content of MDSCs in patients with IBD, MS and PS was significantly higher than in the comparison group and depended on the state of exacerbation/remission. In exacerbation and remission of IBD, MS and PS, a significant increase of MDSCs was revealed when compared with healthy children; the highest values were found in children in exacerbation of MS (Me-3.5 (2.5-5.6) % MNC against Me-1.6 (0.9-2.5) % MNC, p 0.001). In patients with MS, the content of G-MDSC, M-MDSC was significantly higher, and MDSC(M-G-) was lower than in healthy children. An increase in absolute amounts of G-MDSCs was shown in MS exacerbation compared to the disease remission state (p = 0.022). For patients with IBD, a significant increase in percentage of MDSCs and M-MDSCs (p = 0.014 and p = 0.045, respectively) was obtained in exacerbation of the disease relative to remission state. In patients with IBD, MS, and PS, a significant increase in Arg-1 activity in MDSCs was found, with a decreased number of MDSCs in patients in remission compared to exacerbation phase of the disease. In children with autoimmune diseases, an increase in the MDSC populations was found. The activity of arginase-1 in MDSCs is increased in remission, along with a decrease in their numbers.

Recruitment of myeloid‑derived suppressor cells and regulatory T‑cells is associated with the occurrence of acute myocardial infarction.

The roles of myeloid-derived suppressor cells (MDSCs) and regulatory T-cells (Tregs) in acute myocardial infarction (AMI) remain elusive. The present study aimed to analyze the proportions of the granulocytic and monocytic populations of MDSCs (G-MDSCs and M-MDSCs, respectively), and Tregs in the peripheral blood mononuclear cells (PBMCs) of patients with AMI. The present study recruited 34 patients with AMI and 37 healthy controls without clinical signs of myocardial ischemia. PBMCs were isolated from the peripheral blood samples of patients with AMI within 24 h following admission to the hospital and from those of the healthy controls during a physical examination. Two subsets of MDSCs, G-MDSCs (CD15+CD33+CD11b+CD14-HLA-DRlow) and M-MDSCs (CD14+CD15-CD11b+HLA-DRlow), and Tregs (CD3+CD4+CD25highCD127low T-cells) in the PBMCs derived from the patients with AMI and healthy controls were analyzed using flow cytometry. The effects of MDSCs derived from patients with AMI on naïve CD4+ T-cells were examined in the co-culture system. The results revealed that the proportions of G-MDSCs and M-MDSCs were higher in the peripheral blood of patients with AMI than in that of the healthy controls. The patients with AMI had significantly higher numbers of programmed death-ligand (PD-L)1- and PD-L2-positive G-MDSCs and M-MDSCs compared with the healthy controls (P<0.05). The MDSCs could acquire a granulocytic phenotype following AMI, and the G-MDSCs and M-MDSCs would be more likely to express PD-L2 and PD-L1, respectively. The ratios of Tregs to CD4+ T-cells and PD-1+ Tregs in the peripheral blood of patients with AMI were significantly higher than those in the healthy controls (P<0.05). The results of flow cytometry demonstrated an increase in the numbers of inducible Tregs in the co-culture system with the G-MDSCs derived from patients with AMI compared with the G-MDSCs derived from the healthy controls (P<0.01). On the whole, the findings presented herein demonstrate the accumulation of MDSCs, and the upregulation of PD-L1 and PD-L2 expression on the surface of MDSCs in patients with AMI. MDSCs can induce the expansion of Tregs by binding PD-1 on the surface of Tregs, thus playing a crucial role in AMI.

Sunitinib attenuates reactive MDSCs enhancing anti-tumor immunity in HNSCC

Enhancer of zeste homolog 2 (EZH2) is implicated in promoting HNSCC malignant progression. However, EZH2 inhibitors, when used alone, increase the number of myeloid-derived suppressor cells (MDSCs), which are responsible for enhancing tumor stemness and promoting tumor immune escape. We aimed to determine whether combining tazemetostat (an EZH2 inhibitor) and sunitinib (a MDSC inhibitor) can improve the response rate to an immune-checkpoint-blocking (ICB) therapy. We evaluated the efficacy of the above treatment strategies by bioinformatics analysis and animal experiments. EZH2 overexpression and abundant MDSCs in patients with HNSCC are associated with tumor progression. Tazemetostat treatment alone had limited inhibitory effect on HNSCC progression in the mouse models, accompanied by a surge in the number of MDSCs in the tumor microenvironment. Conversely, the combined use of tazemetostat and sunitinib reduced the number of MDSCs and regulatory T cell populations, promoting intratumoral infiltration of T cells and inhibiting of T cell exhausting, regulating of wnt/β-catenin signaling pathway and tumor stemness, promoting the intratumoral PD-L1 expression and improved the response rate to anti-PD-1 therapy. The combined use of EZH2 and MDSC inhibitors effectively reverses HNSCC-specific immunotherapeutic resistance and is a promising strategy for overcoming resistance to ICB therapy.

Potential of Theranostics in Visualisation of the Tumour Microenvironment and Elimination of Its Immunosuppressive Components

Theranostics is a promising branch of nuclear medicine that uses radiopharmaceuticals for diagnosis and treatment of cancer, and immunotheranostics is a special area in it. The aim of the study was to summarise the potential of theranostics for visualisation of the tumour microenvironment and elimination of its immunosuppressive components. The article presents up-to-date information on the composition and interaction of various cell subpopulations in the tumour microenvironment, as well as on the role of cancer stem cells in its formation. It describes defects of signalling pathways and potential targets for theranostics of cancer stem cells. Also, the article provides a description of the mechanism of interaction between the tumour and the immune system in the process of carcinogenesis. The review offers a detailed analysis of approaches to assessing the type of tumour microenvironment in order to individualise treatment and develop a rational design of clinical studies of theranostic couples. The authors present their own data on the distribution of subpopulations of lymphocytes and myeloid-derived suppressor cells in patients with metastatic tumours. The authors have considered the nuances of creating and using various molecules for targeted delivery in the development of diagnostic and therapeutic radiopharmaceuticals. The most promising diagnostic and therapeutic isotopes are described from the point of view of assessing the microenvironment and the possibility of influencing it. The article highlights modern and promising methods of pre-targeting to reduce the toxicity and increase the effectiveness of theranostics. Furthermore, having compared the advantages and disadvantages of theranostics with those of other systemic treatment options for metastatic tumours, the authors outline possible ways to overcome the shortcomings of theranostics.

Tyrosine kinase inhibitors reduce myeloid-derived suppressor cells in patients with chronic myeloid leukemia with better outcome

Background and objectives Myeloid-derived suppressor cells (MDSCs) are increased in several hematologic malignancies. We looked at the effect of imatinib and nilotinib (tyrosine kinase inhibitors) on MDSCs in patients with chronic myeloid leukemia (CML) and how those cells could affect prognosis in CML. Patients and methods A randomized controlled trial was conducted that enrolled 103 patients with newly diagnosed chronic phase CML who were randomly subgrouped into group I, which included patients treated with oral imatinib (n=58) 400 mg/day, and group II, which included patients treated with oral nilotinib (n=45) 600 mg/day. Follow-up of BCR/ABL transcript was measured by quantitative PCR every 3 months. Moreover, detection of the percentages of granulocytic-MDSCs and monocytic (M-MDSCs) in the peripheral blood (HLA-DR/CD11b//CD33/CD14) by flow cytometry was done at baseline and during follow-up. Results Both groups had insignificant difference regarding baseline laboratory and clinical data. Both groups showed significant reduction in MDSCs but with insignificant differences between both of them. Patients did not achieve major molecular response (MMR) and had significantly higher M-MDSCs at baseline. Moreover, baseline M-MDSCs were a predictor for MMR (odds ratio=0.78, 95% confidence interval=0.66–0.93) and for loss of MRR (odds ratio=2.17, 95% confidence interval=1.22–3.87). For prediction of MMR, baseline M-MDSCs had 89.2% accuracy at cutoff point less than 8.9% and had 89.5% accuracy for prediction of loss of MMR at a cutoff point more than 8.5%. Conclusion Both imatinib and nilotinib are effective in reducing MDSCs in patients with CML. Baseline M-MDSCs are predictors of MMR and loss of response in patients with CML. The study was registered on clinicaltrials.gov with NCT03214718.

Myeloid-Derived Suppressor Cells in Patients With Acute Pancreatitis With Increased Inhibitory Function.

Acute pancreatitis (AP) is pancreatic or systemic inflammation without or with motion organ dysfunction. Severe acute pancreatitis (SAP) is the main cause of death for patients with AP. A pro-/anti-inflammatory imbalance is considered the key regulation of disease severity. However, the real mechanism of SAP remains unclear. This study aimed to identify the frequency and specific roll of myeloid-derived suppressor cell (MDSC) in AP. We evaluated MDSC frequency and disease severity by analyzing MDSCs in the peripheral blood of healthy controls (HCs) and patients with mild acute pancreatitis (MAP) and SAP by flow cytometry. We also compared the frequency and inhibitory ability of MDSCs from HCs and SAP, and finally detected the reason for the difference in inhibitory ability. AP was marked by expansion of MDSCs as well as its subsets, granulocytic MDSCs (G-MDSCs) and monocytic MDSCs (M-MDSCs). The proportion of MDSC in the peripheral blood mononuclear cells of patients with AP was increased and positively correlated with AP severity. The frequency of MDSC was decreased after treatment compared with pre-treatment. CD3+ T cells were remarkably inhibited by MDSC derived from the patients with SAP. In the expression of arginase-1 (Arg-1) and reactive oxygen species (ROS), the MDSCs from patients with SAP increased. These findings demonstrated that MDSCs expanded in the peripheral blood in patients with AP, especially in those with SAP. Moreover, the inhibitory ability of MDSCs was increased in the patients with SAP compared with that in the HCs. The enhanced suppressive function was possibly caused by an overexpression of Arg-1 and ROS.

Evaluation The Role of CD33+ CD11b+ myeloid-derived Suppressor Cells in Patients With AML

Acute myeloid leukemia is a genetically heterogeneous clonal disease defined by the accumulation of immature cells in bone marrow and blood. The aim of this study is to evaluate the CD33, CD11b, and HLA-DR expression in Iraqi AML patients and its role in evasion of malignant cells from the immune system. This study was conducted on 60 patients with AML and 20 healthy individuals as a control group to evaluate the expression of CD33 and CD11b using flow-cytometry in peripheral blood, and evaluate Interferons-γ (IFN-γ) and Transforming Growth Factor-β1 (TGF-β1) levels. A statistically non-significant difference (P < 0.005) between the AML patients and control group with regard to the expression of CD33, CD11b, and HLA-DR was observed. Analysis of CD33 expression in myeloid-derived suppressor cells (MDSCs) showed a significant decrease in the proportion of CD33 positive MDSC cells in isolated peripheral blood samples (88.078 ± 1.284). Also, the expression of CD11b in MDSC cells was high (98.841±1.935) in MDSC cells. The mean level of IFN-γ (pg/ml) increased in AML in compared to control group (9.202 ± 0.244), (7.906±1.22), respectively. While TGF- β1 (pg/ml) concentration was found to be elevated in AML patients (69.04 ± 9.92) compared to control group (33.884 ± 2.888). In conclusion, circulating MDSCs were significantly elevated in peripheral blood of patients with AML and characterized by the CD33+CD11b + phenotype; TGF-β1 and IFN-γ can be released in the presence of native human AML cells and affect AML cell proliferation and evasion from immune system.

Myeloid-derived suppressor cells cross-talk with B10 cells by BAFF/BAFF-R pathway to promote immunosuppression in cervical cancer

Immunosuppression induced by myeloid-derived suppressor cells (MDSCs) is one of the main obstacles to the efficacy of immunotherapy for cervical cancer. Recent studies on the immunosuppressive ability of MDSCs have primarily focused on T cells, but the effect of MDSCs on B cells function is still unclear. In a study of clinical specimens, we found that the accumulation of MDSCs in patients with cervical cancer was accompanied by high expression of B cell activating factor (BAFF) on the surface and high expression of interleukin (IL)-10-producing B cells (B10) in vivo. We found that the absence of BAFF could significantly inhibit tumor growth in a cervical cancer model using BAFF KO mice. Further studies showed that abundant MDSCs in cervical cancer induced B cells to differentiate into B10 cells by regulating BAFF which acted on the BAFF receptor (BAFF-R) of them. In this process, we found that a large amount of IL-10 secreted by B10 cells can activate STAT3 signaling pathway in MDSCs, and then form a positive feedback loop to promote the differentiation of B10 cells. Therefore, this study reveals a new mechanism of BAFF-mediated mutual immune regulation between MDSCs and B cells in the occurrence and development of cervical cancer.

Clinical and prognostic significance of CD14 (+) HLA-DR (-/low) myeloid-derived suppressor cells in patients with hepatocellular carcinoma received transarterial radioembolization with Yttrium-90.

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. For unresectable HCC, transarterial radioembolization (TARE) with Yttrium-90 is a widely used treatment. The aim of this study was to investigate whether monocytic myeloid-derived suppressor cells (M-MDSC) and CD39+ T cells can be non-invasive predictive biomarkers of radiological response and prognosis in patients with HCC treated with TARE. This study was conducted on 39 patients with HCC who were treated with TARE between August 2018 and December 2019 and the control group consisted of 23 healthy volunteers. CD4+, CD8+, CD39+ T cells, Natural killer (NK) cells, myeloid cells (MC) and M-MDSC parameters are examined in the course of TARE treatment with student t test and Kaplan-Meier method. There were statistically significant differences in M-MDSC, CD39+ T cells and MC values between healthy controls and HCC patients. A statistically significant difference was found in M-MDSC and CD4+ T cells values in the HCC patient group who responded to the treatment compared to those who did not. Survival analysis found that patients with lower frequencies (under 3.81%) of M-MDSC showed more prominent differences of overall survival (OS) compared to patients with all high groups. We found that M-MDSC in the peripheral blood might be a useful non-invasive biomarker to predict OS. We have shown for the first time that M-MDSC is correlated with treatment response in HCC patients treated with TARE. Additionally, we have found that the percentage of CD39+ T cells is high in HCC patients and these cells are positively correlated with M-MDSC.

Elevated Levels of PD-L1 on MDSCs in Patients with Ph(-) Myeloproliferative Neoplasm

Introduction. We previously reported that PD-1 and PD-L1 were increased in patients with Ph(-) myeloproliferative neoplasm (MPN) ( Wang et al., Leuk Res 2019). The PD-1 inhibitor therapy or immune checkpoint inhibitor therapy (ICI) trial in MPN by Hobbs et al. reported a negative result (Blood, 2020 (supplement )). Resistance to ICI therapy has been reported to be related to myeloid-derived suppressor cells (MDSCs) in melanoma and breast carcinoma. We also previously reported that MDSCs were increased in patients with Ph(-) MPN (Wang et al., Leu Res 2016). Regulation of immune suppression by MDSCs has been reported to be related to PD-1and PD-L1 expression on the MDSC. Therefore, the current study measured PD-1 and PD-L1 expression in MDSCs in patients with Ph(-) MPN.Materials and Methods. Twenty-six patients, including 11 essential thrombocythemias (ETs), six polycythemia vera (PV), and nine myelofibrosis (six primary MF, one post-ET-MF, two post-PVMF) were compared with ten normal volunteer controls. MDSCs were measured as follows: the pelleted PBMNCs were used for Magnetic-assisted cell separation (MACS, Miltenyi Biotech, Inc.). PBMNCs are sequentially selected for HLA-DR - cells, from which we further selected for CD14 + and CD14 - cells using Miltenyic magnetic microbeads kits, respectively, according to the manufacturer's protocol. The resulting HLA-DR -CD14 + and HLA-DR -CD14 - cells were stored at -80°C until use. Flow cytometric assay:HLA-DR -CD14 + and HLA-DR -CD14 - cells were stained with both anti-human CD274 (PD-L1) FITC and human CD279 (PD-1) PE (BD Biosceinces, Inc.), together with anti-human CD14 APC or anti-human CD33 APC (BD Biosceinces, Inc.), respectively. Flow cytometric assessment was done using the BD Accuri C6 flow cytometer. While HLA-DR -CD14 +Monocytic MDCS cells were gated and assayed for surface expression of PD-1 (CD274) and PDL-1 (CD279), G-MDSC (granulocytic MDSC), and M-NDSC (Monocytic MDSC) were assayed as HLA-DR -CD14 - , CD33 + and HLA-DR -CD14 +, respectively. These MDSCs were then assayed for surface expression of PD-1 (CD274) and PDL-1 (CD279). The flow data were analyzed using FlowJo V8 (Flowjo, LLC), and the mean fluorescent intensity (MFI) was calculated.Results. PD-L1 on the m-MDSCs was significantly elevated in patients with MPN (grouping patients with ET, PV, and MF) and MF than controls. PD-1 on the M-MDSCs was not different between ET, PV, MF, or MPN compared with normal controls. Compared to controls, PD-L1 on the G-MDSC was significantly elevated in patients when ET, PV, and MF were grouped as MPN. PD-1 on the G-MDSC were not different between ET, PV, MF, or MPN and controls.Conclusion. Ph(-) MPN was found to have significantly elevated PD-L1 on the M-MDSCs and G-MDSCs, but PD-1 levels were not significantly elevated. Further studies to employ drugs, such as a combination of IMiDs (e.g., lenalidomide) and anti-MDSC drugs in combination with ICI in vitro and clinical trials, may be warranted. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Correlation of myeloid-derived suppressor cells with C-reactive protein, ferritin and lactate dehydrogenase levels in patients with severe COVID-19.

The novel coronavirus disease 2019 (COVID‐19) remains a global health emergency, and understanding the interactions between the virus and host immune responses is crucial to preventing its lethal effects. The expansion of myeloid‐derived suppressor cells (MDSCs) in COVID‐19, thereby suppressing immune responses, has been described as responsible for the severity of the disease, but the correlation between MDSC subsets and COVID‐19 severity remains elusive. Therefore, we classified patients according to clinical and laboratory findings—aiming to investigate the relationship between MDSC subsets and laboratory findings such as high C‐reactive protein, ferritin and lactate dehydrogenase levels, which indicate the severity of the disease. Forty‐one patients with COVID‐19 (26 mild and 15 severe; mean age of 49.7 ± 15 years) and 26 healthy controls were included in this study. MDSCs were grouped into two major subsets—polymorphonuclear MDSCs (PMN‐MDSCs) and monocytic MDSCs—by flow cytometric immunophenotyping, and PMN‐MDSCs were defined as mature and immature, according to CD16 expressions, for the first time in COVID‐19. Total MDSCs, PMN‐MDSCs, mature PMN‐MDSCs and monocytic MDSCs were significantly higher in patients with COVID‐19 compared with the healthy controls (P < .05). Only PMN‐MDSCs and their immature PMN‐MDSC subsets were higher in the severe subgroup than in the mild subgroup. In addition, a significant correlation was found between C‐reactive protein, ferritin and lactate dehydrogenase levels and MDSCs in patients with COVID‐19. These findings suggest that MDSCs play a role in the pathogenesis of COVID‐19, while PMN‐MDSCs, especially immature PMN‐MDSCs, are associated with the severity of the disease.

CD33/CD3-Bispecific T-Cell Engaging (BiTE®) Antibody Constructs Efficiently Target Monocytic CD14+ hla-DRlow IDO+ aml-MDSCs

Acute Myeloid Leukemia (AML) is the most common acute leukemia amongst adults with a 5-year overall survival lower than 25%. Emerging evidence suggest that immune alterations favor leukemogenesis and/or AML relapse thereby negatively impacting disease outcome. Over the last years myeloid derived suppressor cells (MDSCs) have been gaining momentum in the field of cancer research. MDSCs are a heterogeneous cell population morphologically resembling either monocytes or granulocytes and sharing some key features including myeloid origin, aberrant (immature) phenotype, and immunosuppressive activity. Increasing evidence suggests that accumulating MDSCs are involved in hampering anti-tumor immune responses and immune-based therapies. In this study we sought to investigate whether the CD33/CD3-bispecific BiTE® antibody construct (AMG 330) with documented pre-clinical activity against AML blasts can also target CD33+ AML-MDSCs by redirecting and activating T-cells and thereby enhance AMG 330 mediated anti-leukemic activity.First, we assessed the presence of circulating CD14+ cells that co-express CD33 but lack HLA-DR expression (HLA-DRlo) in patients with newly diagnosed AML. These monocytic cells represent one of the best-defined human MDSC subsets. Frequency of CD14+HLA-DRlo cells was significantly increased in untreated AML patients as compared to healthy controls (28,98±4,19%, n=13 versus 3,28±0,75%, n=37) but did not correlate with the number of AML blasts. Purified CD14+HLA-DRlo cells suppressed in vitro T-cell proliferation in a concentration-dependent manner allowing us their denomination as MDSCs.Interestingly, we also observed that primary AML blasts and human AML cell lines (THP, OCI-AML, and HL-60) induced HLA-DRlo cells from healthy donor-derived monocytes that were T-cell suppressive and expressed the immune regulatory indoleamine-2,3-dioxygenase (IDO). Functional and phenotypic reprogramming of monocytes was cell-contact independent.Using ex vivo co-culturing models of primary AML blasts/AML cell lines (=target cells) and T-cells (=effector cells) we observed AMG 330-triggered antibody construct-dependent cell-mediated cytotoxicity/ADCC. Short-term (three to six days) treatment of AML patient-derived peripheral blood mononuclear cells (PBMCs) with 10 or 100 pM AMG 330 led to T-cell activation based on proliferation and on increased expression/production of CD25, CD69, CD137, CD154, IL-2, and IFN-g. The initial T-cell frequency ranging from 0,16 to 14,30% had no impact on their responsiveness. Moreover, we observed a bystander activation of NK-cells. The addition of AML-MDSCs into these co-cultures did not negatively impact ADCC activity. On the contrary, T-cells formed immunological synapses with AML-MDSCs and triggered their elimination (also in presence of AML blasts) overcoming their T-cell suppressive effect. MDSC levels in AML-PBMCs had no effect on AMG 330-mediated T-cell (and bystander cell) activation, which was further corroborated in experiments where the total CD14+ cell compartment (comprising AML-MDSCs) was removed prior AMG 330 application.However, we did observe an impact of MDSCs on BiTE® mediated T-cell proliferation, which has been shown as highly relevant for clinical activity of BiTE® antibody constructs (Zugmaier et al. Blood 2015). Here we found a 1,68-fold enhanced (p=0.001) T-cell expansion in AML-PBMCs treated with 100 pM AMG 330 following CD14+ cell depletion. Given the importance of T-cell proliferation for clinical activity this finding warrants further exploration.Taken together, our results suggest that anti-CD33/CD3 bispecific BiTE® antibody constructs may achieve anti-leukemic efficacy not only through direct T cell mediated cytotoxicity against AML blasts but also through circumventing immune evasion via MDSCs targeting. Although therapeutic targeting of MDSCs in patients has not yet been successfully accomplished, bystander killing of CD33+ MDSCs via anti-CD33/CD3-bispecific BiTE® antibody constructs could represent a very promising approach to increase the anti-leukemic T-cell response in AML patients and to reverse immune evasion. DisclosuresMougiakakos:AMGEN: Research Funding. Kischel:AMGEN: Employment. Michael:AMGEN: Employment. Dos Santos:Amgen Inc.: Employment. Jitschin:AMGEN: Research Funding. Mackensen:AMGEN: Research Funding.

TRAF6 Regulates the Immunosuppressive Effects of Myeloid-Derived Suppressor Cells in Tumor-Bearing Host.

Myeloid-derived suppressor cells (MDSCs) are immature heterogeneous cells derived from the bone marrow and they are the major component of the tumor-induced immunosuppressive environment. Tumor necrosis factor receptor-associated factor 6 (TRAF6), an E3 ubiquitin ligase, catalyzes the polyubiquitination of target proteins. TRAF6 plays a critical role in modulating the immune system. However, whether TRAF6 is involved in the regulation of MDSCs has not been thoroughly elucidated to date. In this study, we found that the expression of TRAF6 in MDSCs derived from tumor tissue was significantly upregulated compared with that of MDSCs from spleen of tumor-bearing mice. Knockdown of TRAF6 remarkably attenuated the immunosuppressive effects of MDSCs. Mechanistically, TRAF6 might improve the immunosuppression of MDSCs by mediating K63-linked polyubiquitination and phosphorylation of signal transducer and activator of transcription 3 (STAT3). Additionally, it was discovered that the accumulation of MDSCs was abnormal in peripheral blood of lung cancer patients. TRAF6 and arginase 1 were highly expressed in MDSCs of patients with lung cancer. Taken together, our study demonstrated that TRAF6 participates in promoting the immunosuppressive function of MDSCs and provided a potential target for antitumor immunotherapy.

Blood Dendritic Cells, Monocytes and Myeloid-derived Suppressor Cells in Patients with COVID-19 Associated Pneumonia

Blood Dendritic Cells, Monocytes and Myeloid-derived Suppressor Cells in Patients with COVID-19 Associated Pneumonia

Expansion of Monocytic Myeloid-Derived Suppressor Cells in Patients Under Hemodialysis Might Lead to Cardiovascular and Cerebrovascular Events

BackgroundThe specific mechanism of cardiovascular and cerebrovascular vasculopathy in the context of end-stage renal disease has not been elucidated. In the present study, we investigated the clinical impact of myeloid-derived suppressor cells (MDSCs) on hemodialysis patients and their mechanism of action.MethodsMDSCs were tested among 104 patients undergoing hemodialysis and their association with overall survival (OS) and cardiovascular and cerebrovascular events was determined.ResultsHemodialysis patients presented a significantly higher level of monocytic MDSCs (M-MDSCs) compared to healthy controls. M-MDSC were tested 3 months after first testing among 103 hemodialysis patients, with one patient not retested due to early death. The repeated results of M-MDSC levels were consistent with the initial results. Patients with persistent high level of M-MDSCs presented decreased OS, as well as increased stroke and acute heart failure events. As illustrated by multivariate Cox regression, M-MDSC was an independent predictor for OS and stroke events of hemodialysis patients. T cell proliferations were significantly abrogated by hemodialysis-related M-MDSCs in a dose-dependent manner. Besides, M-MDSCs presented higher levels of CXCR4 and VLA-4 compared to monocytes, which indicated their enhanced capability to be recruited to atherosclerotic lesions. The expression of arginase I and activity of arginase was also significantly raised in hemodialysis-related M-MDSCs. Human coronary arterial endothelial cells (HCAECs) presented increased capability to migration by coculture with M-MDSCs, compared with monocyte group. Arginase inhibitor and L-arginine abrogated the immune suppressive function and induction of HCAECs migration of hemodialysis related M-MDSC. Plasma IFN-γ, TNF-α and IL-6 were elevated in hemodialysis patients compared with healthy control. M-MDSC level was positively related to IL-6 level among hemodialysis patients. The plasma of hemodialysis patients induced M-MDSCs significantly compared with plasma from health donors. Besides, IL-6 neutralizing antibody significantly abrogated the induction. Neutralizing antibody of IFN-γ and TNF-α partially decreased the generation of arginase of the induced M-MDSC.ConclusionsM-MDSCs were elevated in ESRD patients under hemodialysis, and they exhibited a strong association with the risk of cardiovascular and cerebrovascular diseases. Hemodialysis related M-MDSC presented enhanced recruitment to atherosclerotic lesions, promoted the migration of endothelial cells through exhaustion of local L-arginine.