Myeloid - derived suppressor cells in Type 1 diabetes are an expanded population exhibiting diverse T-cell suppressor mechanisms

The role of notch signaling in regulating myeloid-derived suppressor cells: Implications in Cancer and autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) encompass monocytes and granulocytes, which are innate immune cells capable of suppressing T cells and NK cells. MDSCs exert numerous detrimental effects, as they facilitate tumor initiation, promote tumor growth and metastasis, suppress host immune responses, and evade immune surveillance, thereby hindering anticancer responses. Conversely, in autoimmune diseases, MDSCs exhibit dysfunctional immunosuppressive functions and often display pro-inflammatory effects, which can exacerbate immune disorders. We postulate that this discrepancy is attributable to the involvement of the Notch signaling pathway. The Notch signaling pathway is an evolutionarily conserved mechanism that plays a crucial role in maintaining normal mammalian physiological functions. The Notch receptor undergoes three cleavage events before being transported into the nucleus, where it regulates the transcription of target genes. The role of Notch or MDSCs in different diseases has been fully reported, but the regulatory role of Notch signaling pathway on MDSCs in different diseases has been rarely reported.In this review, we characterize the activation, expansion, and immune suppression mechanisms of MDSCs. We then introduce the Notch signaling pathway and finally discuss its role in colorectal cancer, breast cancer, lung cancer, as well as T-cell acute lymphoblastic leukemia, systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. The Notch signaling pathway regulates MDSCs through distinct mechanisms in these contexts. We hope this review will aid both beginners and experts in systematically understanding the regulation of MDSCs by the Notch signaling pathway in cancer and autoimmune diseases.

Myeloid-derived suppressor cells in metabolic and cardiovascular disorders

Dysregulation of immune homeostasis can precipitate chronic inflammation, thus significantly contributing to the onset and progression of metabolic and cardiovascular diseases. Myeloid-derived suppressor cells (MDSCs) constitute a heterogeneous population of immature myeloid cells that are mobilized in response to biological stressors such as tissue damage and inflammation. Although MDSCs have been extensively characterized in the contexts of cancer and infectious diseases, emerging evidence highlights their pivotal roles in the pathophysiology of metabolic and cardiovascular disorders. We discuss growing evidence for the involvement of MDSCs in the progression of metabolic and cardiovascular diseases, with the aim of deepening our understanding of MDSCs in cardiometabolic physiology and identifying the necessary steps for the development of innovative MDSC-targeted therapeutic strategies.

The role of myeloid-derived suppressor cells in children

Myeloid-derived suppressor cells (MDSC) were first recognized over twenty years ago as a key immunomodulatory cell population. Since their initial identification, a growing body of literature points to the importance of MDSC as a heterogeneous, immunosuppressive cell population and as a therapeutic target in adults with cancer. MDSC are potent suppressors of T cells and Natural Killer (NK) cells and can be helpful or harmful to the host depending on the pathophysiology. For example, MDSC are beneficial in pregnancy and prevent spontaneous abortion by promoting maternal-fetal tolerance. Increased MDSC are also associated with improved outcomes in patients with graft vs. host disease by decreasing T cell-driven inflammation. However, MDSC can also be harmful and are known to be pathologic in adults with cancer and chronic infections by promoting tumor escape and impairing pathogen clearance, respectively. Despite the widespread recognition of the importance of MDSC and their immune suppression effects in adults, much less is known regarding the role of MDSC in children. Research investigating MDSC in children lags significantly behind adult studies. In fact, while over 5,000 publications on PubMed discuss MDSC in immune regulation, fewer than 50 of these publications focus specifically on their role in children. This review aims to summarize the existing literature on the role of MDSC in children and identify important directions for future research, including targeting these cells in the pediatric population to improve clinical outcomes.

Polymorphonuclear myeloid-derived suppressor cells regulates immune recovery during HIV infection through PD-L1 and TGF-β pathways

Background

Although MDSCs are widely recognized for their immunoinhibitory effects in pathological conditions, their function during HIV infection particularly within the mechanisms underlying incomplete immune recovery remains elusive.

Methods

We conducted a cross-sectional study in which 30 healthy controls and 62 HIV-1-infected subjects [31 immunological non-responders (INRs) and 31 immunological responders (IRs)] were selected. The proportion of MDSCs was determined in each category of participants. Using flow cytometry and real-time PCR, immune regulatory molecules (including PD-L1, ARG1, iNOS, IL-10, TGF-β, and IDO) that are relevant for MDSCs activity were quantified. Furthermore, we investigated the impact of the blockade of PD-L1 and TGF-β pathways on MDSCs and their effects on CD4+ T-cells using in vitro functional experiments.

Results

PMN-MDSCs are more abundant and are negatively correlated to CD4 counts in HIV-infected individuals. In addition, PMN-MDSCs suppress CD4+ T-cell proliferation and IFN-γ production in INRs. Furthermore, correlations were found between PD-L1 expression on PMN-MDSCs and PD-1+ CD4+ T-cells. TGF-β expression on PMN-MDSCs was likewise enhanced in INRs. Importantly, inhibiting both PD-L1 and TGF-β pathways had a synergistic impact on restoring CD4+ T-cell activity in vitro.

Conclusions

PMN-MDSCs expansion inhibits CD4+ T-cell responses. We suggest that targeting PD-L1 and TGF-β pathways together may significantly improve immune recovery in INRs.

Myeloid-Derived Suppressor Cells (MDSCs) and Obesity-Induced Inflammation in Type 2 Diabetes

Type 2 diabetes mellitus is a complex metabolic disorder characterized by insulin resistance and, subsequently, decreased insulin secretion. This condition is closely linked to obesity, a major risk factor that boosts the development of chronic systemic inflammation, which, in turn, is recognized for its crucial role in the onset of insulin resistance. Under conditions of obesity, adipose tissue, particularly visceral fat, becomes an active endocrine organ that releases a wide range of pro-inflammatory mediators, including cytokines, chemokines, and adipokines. These mediators, along with cluster of differentiation (CD) markers, contribute to the maintenance of systemic low-grade inflammation, promote cellular signaling and facilitate the infiltration of inflammatory cells into tissues. Emerging studies have indicated the accumulation of a new cell population in the adipose tissue in these conditions, known as myeloid-derived suppressor cells (MDSCs). These cells possess the ability to suppress the immune system, impacting obesity-related chronic inflammation. Given the limited literature addressing the role of MDSCs in the context of type 2 diabetes, this article aims to explore the complex interaction between inflammation, obesity, and MDSC activity. Identifying and understanding the role of these immature cells is essential not only for improving the management of type 2 diabetes but also for the potential development of targeted therapeutic strategies aimed at both glycemic control and the reduction in associated inflammation.

Immune-Mediated Inflammatory Diseases and Cancer - a dangerous liaison

Patients with Immune-Mediated Inflammatory Diseases (IMIDs) are known to have an elevated risk of developing cancer, but the exact causative factors remain subject to ongoing debate. This narrative review aims to present the available evidence concerning the intricate relationship between these two conditions. Environmental influences and genetic predisposition lead to a dysregulated immune response resulting in chronic inflammation, which is crucial in the pathogenesis of IMIDs and oncogenic processes. Mechanisms such as the inflammatory microenvironment, aberrant intercellular communication due to abnormal cytokine levels, excessive reparative responses, and pathological angiogenesis are involved. The chronic immunosuppression resulting from IMIDs treatments further adds to the complexity of the pathogenic scenario. In conclusion, this review highlights critical gaps in the current literature, suggesting potential avenues for future research. The intricate interplay between IMIDs and cancer necessitates more investigation to deepen our understanding and improve patient management.

Shifting phenotype and differentiation of CD11b+Gr.1+ immature heterogeneous myeloid derived adjuster cells support inflammation and induce regulators of IL17A in imiquimod induced psoriasis

OBJECTIVE AND DESIGN

The exact immunological mechanism of widespread chronic inflammatory skin disorder psoriasis has not been fully established. CD11b+Gr.1+ myeloid-derived cells are immature heterogeneous cells with T-cell suppressive property in neoplasia; however, influence of these cells on adaptive immunity is highly contextual; therefore, we dubbed these cells as myeloid-derived adjuster cells (MDAC). We studied imiquimod induced psoriasis in mouse model and evaluated for the first time the RORγt-NFAT1 axis in MDACs and the function, differentiation and interaction of these cells with T cells.

MATERIALS AND METHODS

The status of T cells and MDACs; their functionality and differentiation properties, and the roles of RORγt and NFAT1 in MDACs were evaluated using flow cytometry, qRT-PCR and confocal imaging.

RESULTS

We found gradual increase in T cells and MDACs and an increase in the number of IL17 -secreting MDACs and T cells in the skin of psoriatic animals. We also noted that MDAC differentiation is biased toward M1 macrophages and DCs which perpetuate inflammation. We found that psoriatic MDACs were unable to suppress T-cell proliferation or activation but seemingly helped these T cells produce more IL17. Inhibition of the RORγt/NFAT1 axis in MDACs increased the suppressive nature of MDACs, allowing these cells to suppress the activity of psoriatic T-cells.

CONCLUSION

Our results indicate that altered MDAC properties in psoriatic condition sustains pathological inflammation and RORγt and NFAT1 as promising intervention target for psoriasis management.

Dual roles of myeloid-derived suppressor cells in various diseases: a review

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that originate from bone marrow stem cells. In pathological conditions, such as autoimmune disorders, allergies, infections, and cancer, normal myelopoiesis is altered to facilitate the formation of MDSCs. MDSCs were first shown to promote cancer initiation and progression by immunosuppression with the assistance of various chemokines and cytokines. Recently, various studies have demonstrated that MDSCs play two distinct roles depending on the physiological and pathological conditions. MDSCs have protective roles in autoimmune disorders (such as uveoretinitis, multiple sclerosis, rheumatoid arthritis, ankylosing spondylitis, type 1 diabetes, autoimmune hepatitis, inflammatory bowel disease, alopecia areata, and systemic lupus erythematosus), allergies, and organ transplantation. However, they play negative roles in infections and various cancers. Several immunosuppressive functions and mechanisms of MDSCs have been determined in different disease conditions. This review comprehensively discusses the associations between MDSCs and various pathological conditions and briefly describes therapeutic approaches.

Increased monocytic myeloid-derived suppressor cells in type 2 diabetes correlate with hyperglycemic and was a risk factor of infection and tumor occurrence

To investigate the frequency of monocytic myeloid-derived suppressor cells (M-MDSCs) in type 2 diabetes mellitus (T2DM) patients and explore the potential associations between M-MDSCs, glycemic control, and the occurrence of infections and tumor. 102 healthy and 77 T2DM individuals were enrolled. We assessed the M-MDSCs frequency, levels of fasting plasma glucose (FPG), haemoglobin A1c (HbA1c), and other relevant indicators. Each patient underwent a follow-up of at least 6 months after M-MDSCs detection. The M-MDSCs frequency was significantly higher in patients with poor glycemic control (PGC) compared to the healthy population (P < 0.001), whereas there was no significant difference between patients with good glycemic control and the healthy (P > 0.05). There was a positive correlation between the M-MDSCs frequency and FPG, HbA1c (R = 0.517 and 0.315, P < 0.001, respectively). T2DM patients with abnormally increased M-MDSCs have a higher incidence of infection and tumor (48.57% and 11.43% respectively). Our results shed new light on the pathogenesis of T2DM, help to understand why T2DM patients are susceptible to infection and tumor and providing novel insights for future prevention and treatment of T2DM.

Diverse functions of myeloid-derived suppressor cells in autoimmune diseases

Since myeloid-derived suppressor cells (MDSCs) were found suppressing immune responses in cancer and other pathological conditions, subsequent researchers have pinned their hopes on the suppressive function against immune damage in autoimmune diseases. However, recent studies have found key distinctions of MDSC immune effects in cancer and autoimmunity. These include not only suppression and immune tolerance, but MDSCs also possess pro-inflammatory effects and exacerbate immune disorders during autoimmunity, while promoting T cell proliferation, inducing Th17 cell differentiation, releasing pro-inflammatory cytokines, and causing direct tissue damage. Additionally, MDSCs could interact with surrounding cells to directly cause tissue damage or repair, sometimes even as an inflammatory indicator in line with disease severity. These diverse manifestations could be partially attributed to the heterogeneity of MDSCs, but not all. The different disease types, disease states, and cytokine profiles alter the diverse phenotypes and functions of MDSCs, thus leading to the impairment or obversion of MDSC suppression. In this review, we summarize the functions of MDSCs in several autoimmune diseases and attempt to elucidate the mechanisms behind their actions.

Myeloid-derived suppressor cells in the therapy of autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) are well recognized as critical factors in the pathology of tumors. However, their roles in autoimmune diseases are still unclear, which hampers the development of efficient immunotherapies. The role of different MDSCs subsets in multiple sclerosis, inflammatory bowel diseases, rheumatoid arthritis, type 1 diabetes, and systemic lupus erythematosus displayed different mechanisms of immune suppression, and several studies pointed to MDSCs' capacity to induce T-helper (Th)17 cells and tissue damage. These results also suggested that MDSCs could be present in different functional states and utilize different mechanisms for controlling the activity of T and B cells. Therefore, various therapeutic strategies should be employed to restore homeostasis in autoimmune diseases. The therapies harnessing MDSCs could be designed either as cell therapy or rely on the expansion and activation of MDSCs in vivo, or their depletion. Cumulatively, MDSCs are inevitable players in autoimmunity, and rational approaches in developing therapies are required to avoid the adverse effects of MDSCs and harness their suppressive mechanisms to improve the overall efficacy of autoimmunity therapy.

Decreased programmed cell death ligand 2-positive monocytic myeloid-derived suppressor cells and programmed cell death protein 1-positive T-regulatory cells in patients with type 2 diabetes: implications for immunopathogenesis

Objectives

The activation of immune cells plays a significant role in the progression of type 2 diabetes. This study aimed to investigate the potential role of myeloid-derived suppressor cells (MDSCs) and T-regulatory cells (Tregs) in type 2 diabetes.

Methods

A total of 61 patients diagnosed with type 2 diabetes were recruited. Clinical characteristics were reviewed and peripheral blood samples were collected. We calculated the percentage of different cells. Frequencies of MDSC subsets refered to the percentage of G-MDSCs (CD15+CD33+CD11b+CD14-HLA-DR-/low) in CD45 positive cells and the percentage of M-MDSCs (CD14+CD15-CD11b+CD33+HLA-DR-/low) in lymphocytes plus monocytes.

Results

Frequencies of programmed cell death ligand 1-positive granulocytic MDSCs (PD-L1+ G-MDSCs), programmed cell death ligand 2-positive monocytic MDSCs (PD-L2+ M-MDSCs), PD-L2+ G-MDSC, and programmed cell death protein 1-positive Tregs (PD-1+Tregs) were decreased in patients with type 2 diabetes. The frequency of PD-1+ Tregs was positively related to PD-L2+ M-MDSCs (r= 0.357, P = 0.009) and negatively related to HbA1c (r = -0.265, P = 0.042), fasting insulin level (r = -0.260, P = 0.047), and waist circumference (r = -0.373, P = 0.005).

Conclusions

Decreased PD-L2+ M-MDSCs and PD-1+ Tregs may promote effector T cell activation, leading to chronic low-grade inflammation in type 2 diabetes. These findings highlight the contribution of MDSCs and Tregs to the immunopathogenesis of type 2 diabetes and suggest their potential as targets for new therapeutic approaches.

Myeloid-derived suppressor cells: Are they involved in gestational diabetes mellitus?

Gestational diabetes mellitus (GDM) is currently the most common metabolic complication during pregnancy, with an increasing prevalence worldwide. Maternal immune dysregulation might be partly responsible for the pathophysiology of GDM. Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of cells, emerging as a new immune regulator with potent immunosuppressive capacity. Although the fate and function of these cells were primarily described in pathological conditions such as cancer and infection, accumulating evidences have spotlighted their beneficial roles in homeostasis and physiological conditions. Recently, several studies have explored the roles of MDSCs in the diabetic microenvironment. However, the fate and function of these cells in GDM are still unknown. The current review summarized the existing knowledges about MDSCs and their potential roles in diabetes during pregnancy in an attempt to highlight our current understanding of GDM-related immune dysregulation and identify areas where further study is required.

Autoimmunity and Cancer-Two Sides of the Same Coin

Autoimmune disease results from the immune response against self-antigens, while cancer develops when the immune system does not respond to malignant cells. Thus, for years, autoimmunity and cancer have been considered as two separate fields of research that do not have a lot in common. However, the discovery of immune checkpoints and the development of anti-cancer drugs targeting PD-1 (programmed cell death receptor 1) and CTLA-4 (cytotoxic T lymphocyte antigen 4) pathways proved that studying autoimmune diseases can be extremely helpful in the development of novel anti-cancer drugs. Therefore, autoimmunity and cancer seem to be just two sides of the same coin. In the current review, we broadly discuss how various regulatory cell populations, effector molecules, genetic predisposition, and environmental factors contribute to the loss of self-tolerance in autoimmunity or tolerance induction to cancer. With the current paper, we also aim to convince the readers that the pathways involved in cancer and autoimmune disease development consist of similar molecular players working in opposite directions. Therefore, a deep understanding of the two sides of immune tolerance is crucial for the proper designing of novel and selective immunotherapies.

Myeloid-Derived Suppressor Cells and Clinical Outcomes in Children With COVID-19

BACKGROUND

Although children with COVID-19 account for fewer hospitalizations than adults, many develop severe disease requiring intensive care treatment. Critical illness due to COVID-19 has been associated with lymphopenia and functional immune suppression. Myeloid-derived suppressor cells (MDSCs) potently suppress T cells and are significantly increased in adults with severe COVID-19. The role of MDSCs in the immune response of children with COVID-19 is unknown.

AIMS

We hypothesized that children with severe COVID-19 will have expansion of MDSC populations compared to those with milder disease, and that higher proportions of MDSCs will correlate with clinical outcomes.

METHODS

We conducted a prospective, observational study on a convenience sample of children hospitalized with PCR-confirmed COVID-19 and pre-pandemic, uninfected healthy controls (HC). Blood samples were obtained within 48 h of admission and analyzed for MDSCs, T cells, and natural killer (NK) cells by flow cytometry. Demographic information and clinical outcomes were obtained from the electronic medical record and a dedicated survey built for this study.

RESULTS

Fifty children admitted to the hospital were enrolled; 28 diagnosed with symptomatic COVID-19 (10 requiring ICU admission) and 22 detected by universal screening (6 requiring ICU admission). We found that children with severe COVID-19 had a significantly higher percentage of MDSCs than those admitted to the ward and uninfected healthy controls. Increased percentages of MDSCs in peripheral blood mononuclear cells (PBMC) were associated with CD4+ T cell lymphopenia. MDSC expansion was associated with longer hospitalizations and need for respiratory support in children admitted with acute COVID-19.

CONCLUSION

These findings suggest that MDSCs are part of the dysregulated immune responses observed in children with severe COVID-19 and may play a role in disease pathogenesis. Future mechanistic studies are required to further understand the function of MDSCs in the setting of SARS-CoV-2 infection in children.

Emerging Roles of Myeloid-Derived Suppressor Cells in Diabetes

Diabetes is a syndrome characterized by hyperglycemia with or without insulin resistance. Its etiology is attributed to the combined action of genes, environment and immune cells. Myeloid-derived suppressor cell (MDSC) is a heterogeneous population of immature cells with immunosuppressive ability. In recent years, different studies have debated the quantity, activity changes and roles of MDSC in the diabetic microenvironment. However, the emerging roles of MDSC have not been fully documented with regard to their interactions with diabetes. Here, the manifestations of MDSC and their subsets are reviewed with regard to the incidence of diabetes and diabetic complications. The possible drugs targeting MDSC are discussed with regard to their potential of treating diabetes. We believe that understanding MDSC will offer opportunities to explain pathological characteristics of different diabetes. MDSC also will be used for personalized immunotherapy of diabetes.

Syngeneic bone marrow transplantation in combination with PI3K inhibitor reversed hyperglycemia in later-stage streptozotocin-induced diabetes

Background

Type 1 diabetes (T1D) is a multiple factor autoimmune disease characterized by T cell-mediated immune destruction of islet β cells. Autologous hematopoietic stem cell transplantation (AHSCT) has been a novel strategy for patients with new-onset T1D, but not for those with a later diagnosis. Disturbance of regulatory T cells (Tregs) likely contributes to poor response after transplantation in later-stage T1D. Inhibition of phosphoinositide 3-kinases (PI3K)/Akt signaling maintains Tregs’ homeostasis.

Methods

We built a later-stage streptozotocin (STZ)-induced T1D mouse model. Syngeneic bone marrow transplantation (syn-BMT) was performed 20 days after the onset of diabetes in combination with BKM120 (a PI3K inhibitor). Meanwhile, another group of STZ-diabetic mice were transplanted with bone marrow cells cocultured with BKM120 in vitro for 24 h. Fasting glucose and glucose tolerance were recorded during the entire experimental observation after syn-BMT. Samples were collected 126 days after syn-BMT. Hematoxylin and eosin (H&E) staining was used to detect the effect of PI3K inhibitor combined with syn-BMT on morphology of the T1D pancreas. CD4⁺CD25⁻ T cells and CD4⁺CD25⁺ T cells were sorted by magnetic cell sorting (MACS), then fluorescence activated cell sorting (FACS) and quantitative real-time PCR (qPCR) were used to detect the effect of PI3K inhibitor on modulating immune disorder and restoring the function of Treg cells.

Results

Our investigation showed syn-BMT in combination with BKM120 effectively maintained normoglycemia in later-stage T1D. The disease remission effects may be induced by the rebalance of Th17/Tregs dysregulation and restoration of Tregs’ immunosuppressive function by BKM120 after syn-BMT.

Conclusions

These results may reveal important connections for PI3K/Akt inhibition and Tregs’ homeostasis in T1D after transplantation. AHSCT combining immunoregulatory strategies such as PI3K inhibition may be a promising therapeutic approach in later-stage T1D.

Three distinct tolerogenic CD14+ myeloid cell types to actively manage autoimmune disease: Opportunities and challenges

Current treatment for patients with autoimmune disorders including rheumatoid arthritis, multiple sclerosis and type 1 diabetes, often consists of long-term drug regimens that broadly dampen immune responses. These non-specific treatments are frequently associated with severe side effects creating an urgent need for safer and more effective therapy to promote peripheral tolerance in autoimmune diseases. Cell-based immunotherapy may offer an encouraging alternative, where tolerogenic CD14⁺ myeloid cells are infused to inhibit autoreactive effector cells. In this review, we compared in depth three promising tolerogenic CD14⁺ candidates for the treatment of autoimmune disease: 1) tolerogenic dendritic cells, 2) monocytic myeloid-derived suppressor cells and 3) CD14⁺ type 2 conventional dendritic cells. TolDC-based therapy has entered clinical testing whereas evidence from the latter two cell types m-MDSCs and CD14⁺ cDC2s is predominantly coming from cancer immunology research. These three cell types have distinct cellular properties and immunosuppressive mechanisms offering unique opportunities to be explored. However, these cells differ in stage of development towards immunotherapy each facing additional hurdles. Therefore, we speculate on the potential benefits and risks of these cell types as novel cell-based immunotherapies to control autoimmune disease in patients.