Human Regulatory Dendritic Cells Develop From Monocytes in Response to Signals From Regulatory and Helper T Cells

IL-2, IL-17A and TNF-α hold potential as biomarkers for predicting acute mountain sickness prior to ascent

BACKGROUND

Acute mountain sickness (AMS) is the most prevalent condition resulting from hypobaric hypoxia (HH) at high altitudes. Although evidence suggests the involvement of inflammatory cytokines in AMS development, there is currently a lack of reports on variations in cytokine levels between individuals susceptible to AMS and those resistant to AMS prior to ascending to high altitude. Thus our current study aims to assess the predictive capability for AMS occurrence by evaluating differences in cytokine levels at low altitudes.

METHODS

The present study recruited 48 participants, who ascended from low altitude to middle high-altitude (3700 m) and further to extreme high-altitude (5000 m). Based on Lake Louise Score (LLS) at the two high altitudes, participants were categorized into severe AMS-susceptible (sAMS), moderate AMS-susceptible (mAMS), and non-AMS groups. The Bio-Plex MAGPIX System was employed to measure plasma levels of 11 inflammatory cytokines. Cytokines at low altitude and middle high-altitude were analyzed through receiver operating characteristic (ROC) analysis to obtain area under the ROC curve (AUROC), sensitivity, and specificity.

RESULTS

Based on LLS at 3700 m, we initially categorized the study subjects into the sAMS group (n = 8) and the Non-AMS group (n = 40). Among individuals in the non-AMS group (n = 40) at the altitude of 3700 m, those who developed AMS at the altitude of 5000 m were assigned to the mAMS group (n = 17), whereas those who did not experience AMS were included into the non-AMS group (n = 23). The concentration of TNF-α at low altitude exhibited robust predictive performance for predicting AMS occurrence at the altitude of 3700 m. Among the non-AMS group at the altitude of 3700 m, we identified that the concentration of IL-2 and IL-17A demonstrated high efficacy in predicting the onset of AMS following ascent to 5000 m. In addition, differentially expressed cytokines including IL-17A, TNF-α and IL-2 at low altitude possessed discriminatory potential among the three groups at 5000 m..

CONCLUSION

We posited that the levels of TNF-α, IL-2, IL-17A in serum of low altitude could be considered as potential biomarkers to predict the occurrence of AMS at high altitude.

NEW & NOTEWORTHY

Through the two comparisons at different two altitudes (baseline level and 3700 m), we provided a model to progressively screen individuals who are susceptible and resistant to different high altitudes (3700 m and 5000 m). TNF-α could firstly screen out the AMS susceptible individuals at the altitude of 3700 m. And through its combination with IL-2 and IL-17A, we could further screen out AMS susceptible individuals at the altitude of 5000 m.

CCL22 Induces the Polarization of Immature Dendritic Cells into Tolerogenic Dendritic Cells in Radiation-Induced Lung Injury through the CCR4-Dectin2-PLC-γ2-NFATC2-Nr4a2-PD-L1 Signaling Pathway

Recruitment of immune cells to the injury site plays a pivotal role in the pathology of radiation-associated diseases. In this study, we investigated the impact of the chemokine CCL22 released from alveolar type II epithelial (AT2) cells after irradiation on the recruitment and functional changes of dendritic cells (DCs) in the development of radiation-induced lung injury (RILI). By examining changes in CCL22 protein levels in lung tissue of C57BL/6N mice with RILI, we discovered that ionizing radiation increased CCL22 expression in irradiated alveolar AT2 cells, as did MLE-12 cells after irradiation. A transwell migration assay revealed that CCL22 promoted the migration of CCR4-positive DCs to the injury site, which explained the migration of pulmonary CCR4-positive DCs in RILI mice in vivo. Coculture experiments demonstrated that, consistent with the response of regulatory T cells in the lung tissue of RILI mice, exogenous CCL22-induced DCs promoted regulatory T cell proliferation. Mechanistically, we demonstrated that Dectin2 and Nr4a2 are key targets in the CCL22 signaling pathway, which was confirmed in pulmonary DCs of RILI mice. As a result, CCL22 upregulated the expression of PD-L1, IL-6, and IL-10 in DCs. Consequently, we identified a mechanism in which CCL22 induced DC tolerance through the CCR4-Dectin2-PLC-γ2-NFATC2-Nr4a2-PD-L1 pathway. Collectively, these findings demonstrated that ionizing radiation stimulates the expression of CCL22 in AT2 cells to recruit DCs to the injury site and further polarizes them into a tolerant subgroup of CCL22 DCs to regulate lung immunity, ultimately providing potential therapeutic targets for DC-mediated RILI.

Combination therapy with probiotics and anti-PD-L1 antibody synergistically ameliorates sepsis in mouse model

The study investigated the protective effects and mechanisms of probiotics in conjunction with an anti-PD-L1 antibody on the immune functions of septic mice. Sixty-four mice were assigned to sepsis groups receiving vehicle, probiotics, and anti-PD-L1 antibody individually or in combination, with healthy mice as controls. Sepsis was induced by cecal ligation and puncture (CLP), followed by intraperitoneal Lipopolysaccharide (LPS) injection. Blood and tissues were collected one day post-injection for detecting inflammation-related cytokines, Treg, PI3K/Akt pathway-related protein expression, and lung tissue pathology. The survival time of the remaining ten mice was recorded over seven days. Compared to healthy mice, septic mice given PBS exhibited significantly different serum levels of IL-6, IL-8, IL-17, IL-10, and IFN-γ (all p < 0.001). Treatment with anti-PD-L1 antibody combined with probiotics significantly increased the 7-day survival rate in septic mice, accompanied by decreased pro-inflammatory cytokines, increased anti-inflammatory cytokines, improved oxidative stress, reduced lung injury, and enhanced Th17/Treg balance. This combined therapy demonstrated superior efficacy compared to antibodies or probiotics alone. Additionally, it facilitated peripheral blood polymorphonuclear neutrophil apoptosis, enhancing protection by blocking PD-L1 function and inhibiting PI3K-dependent AKT phosphorylation. In conclusion, combining probiotics with an anti-PD-L1 antibody enhances protective effects in septic mice by reducing serum inflammatory factors, promoting neutrophil apoptosis, regulating Th17/Treg balance, and inhibiting the PI3K/Akt pathway.

Dendritic Cells in Shaping Anti-Tumor T Cell Response

Among professional antigen-presenting cells, dendritic cells (DCs) orchestrate innate and adaptive immunity and play a pivotal role in anti-tumor immunity. DCs are a heterogeneous population with varying functions in the tumor microenvironment (TME). Tumor-associated DCs differentiate developmentally and functionally into three main subsets: conventional DCs (cDCs), plasmacytoid DCs (pDCs), and monocyte-derived DCs (MoDCs). There are two major subsets of cDCs in TME, cDC1 and cDC2. cDC1 is critical for cross-presenting tumor antigens to activate cytotoxic CD8+ T cells and is also required for priming earlier CD4+ T cells in certain solid tumors. cDC2 is vital for priming anti-tumor CD4+ T cells in multiple tumor models. pDC is a unique subset of DCs and produces type I IFN through TLR7 and TLR9. Studies have shown that pDCs are related to immunosuppression in the TME through the secretion of immunosuppressive cytokines and by promoting regulatory T cells. MoDCs differentiate separately from monocytes in response to inflammatory cues and infection. Also, MoDCs can cross-prime CD8+ T cells. In this review, we summarize the subsets and functions of DCs. We also discuss the role of different DC subsets in shaping T cell immunity in TME and targeting DCs for potential immunotherapeutic benefits against cancer.

Exploring Immune Redox Modulation in Bacterial Infections: Insights into Thioredoxin-Mediated Interactions and Implications for Understanding Host-Pathogen Dynamics

Bacterial infections trigger a multifaceted interplay between inflammatory mediators and redox regulation. Recently, accumulating evidence has shown that redox signaling plays a significant role in immune initiation and subsequent immune cell functions. This review addresses the crucial role of the thioredoxin (Trx) system in the initiation of immune reactions and regulation of inflammatory responses during bacterial infections. Downstream signaling pathways in various immune cells involve thiol-dependent redox regulation, highlighting the pivotal roles of thiol redox systems in defense mechanisms. Conversely, the survival and virulence of pathogenic bacteria are enhanced by their ability to counteract oxidative stress and immune attacks. This is achieved through the reduction of oxidized proteins and the modulation of redox-sensitive signaling pathways, which are functions of the Trx system, thereby fortifying bacterial resistance. Moreover, some selenium/sulfur-containing compounds could potentially be developed into targeted therapeutic interventions for pathogenic bacteria. Taken together, the Trx system is a key player in redox regulation during bacterial infection, and contributes to host-pathogen interactions, offering valuable insights for future research and therapeutic development.

Revisiting regulatory T cells as modulators of innate immune response and inflammatory diseases

Regulatory T cells (Treg) are known to be critical for the maintenance of immune homeostasis by suppressing the activation of auto- or allo-reactive effector T cells through a diverse repertoire of molecular mechanisms. Accordingly, therapeutic strategies aimed at enhancing Treg numbers or potency in the setting of autoimmunity and allogeneic transplants have been energetically pursued and are beginning to yield some encouraging outcomes in early phase clinical trials. Less well recognized from a translational perspective, however, has been the mounting body of evidence that Treg directly modulate most aspects of innate immune response under a range of different acute and chronic disease conditions. Recognizing this aspect of Treg immune modulatory function provides a bridge for the application of Treg-based therapies to common medical conditions in which organ and tissue damage is mediated primarily by inflammation involving myeloid cells (mononuclear phagocytes, granulocytes) and innate lymphocytes (NK cells, NKT cells, γδ T cells and ILCs). In this review, we comprehensively summarize pre-clinical and human research that has revealed diverse modulatory effects of Treg and specific Treg subpopulations on the range of innate immune cell types. In each case, we emphasize the key mechanistic insights and the evidence that Treg interactions with innate immune effectors can have significant impacts on disease severity or treatment. Finally, we discuss the opportunities and challenges that exist for the application of Treg-based therapeutic interventions to three globally impactful, inflammatory conditions: type 2 diabetes and its end-organ complications, ischemia reperfusion injury and atherosclerosis.

Immunosuppressive Polymeric Nanoparticles Targeting Dendritic Cells Alleviate Lupus Disease in Fcgr2b-/- Mice by Mediating Antigen-Specific Immune Tolerance

Dendritic cells (DCs) are the most potent antigen-presenting cells that have multifaceted functions in the control of immune activation and tolerance. Hyperresponsiveness and altered tolerogenicity of DCs contribute to the development and pathogenesis of system lupus erythematosus (SLE); therefore, DC-targeted therapies aimed at inducing specific immune tolerance have become of great importance for the treatment of SLE. This study developed a new nanoparticle (NP) containing a biodegradable PDMAEMA-PLGA copolymer for target-oriented delivery to DCs in situ. PDMAEMA-PLGA NPs provided sustained drug release and exhibited immunosuppressive activity in FLT3L and GM-CSF-derived bone marrow in conventional DCs (BM-cDCs). PDMAEMA-PLGA NPs improved dexamethasone capability to convert wild-type and Fcgr2b^-/- BM-cDCs from an immunogenic to tolerogenic state, and BM-cDCs treated with dexamethasone-incorporated PDMAEMA-PLGA NPs (Dex-NPs) efficiently mediated regulatory T cell (Treg) expansion in vitro. Dex-NP therapy potentially alleviated lupus disease in Fcgr2b^-/- mice by mediating Foxp3⁺ Treg expansion in an antigen-specific manner. Our findings substantiate the superior efficacy of DC-targeted therapy using the PDMAEMA-PLGA NP delivery system and provide further support for clinical development as a potential therapy for SLE. Furthermore, PDMAEMA-PLGA NP may be a versatile platform for DC-targeted therapy to induce antigen-specific immune tolerance to unwanted immune responses that occur in autoimmune disease, allergy, and transplant rejection.

ROS fine-tunes the function and fate of immune cells

The redox state is essential to the process of cell life, which determines cell fate. As an important signaling molecule of the redox state, reactive oxygen species (ROS) are crucial for the homeostasis of immune cells and participate in the pathological processes of different diseases. We discuss the underlying mechanisms and possible signaling pathways of ROS to fine-tune the proliferation, differentiation, polarization and function of immune cells, including T cells, B cells, neutrophils, macrophages, myeloid-derived inhibitory cells (MDSCs) and dendritic cells (DCs). We further emphasize how excessive ROS lead to programmed immune cell death such as apoptosis, ferroptosis, pyroptosis, NETosis and necroptosis, providing valuable insights for future therapeutic strategies in human diseases.

Crosstalk between dendritic cells and regulatory T cells: Protective effect and therapeutic potential in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system related to autoimmunity and is characterized by demyelination, neuroinflammation, and neurodegeneration. Cell therapies mediated by dendritic cells (DCs) and regulatory T cells (Tregs) have gradually become accumulating focusing in MS, and the protective crosstalk mechanisms between DCs and Tregs provide the basis for the efficacy of treatment regimens. In MS and its animal model experimental autoimmune encephalomyelitis, DCs communicate with Tregs to form immune synapses and complete a variety of complex interactions to counteract the unbalanced immune tolerance. Through different co-stimulatory/inhibitory molecules, cytokines, and metabolic enzymes, DCs regulate the proliferation, differentiation and function of Tregs. On the other hand, Tregs inhibit the mature state and antigen presentation ability of DCs, ultimately improving immune tolerance. In this review, we summarized the pivotal immune targets in the interaction between DCs and Tregs, and elucidated the protective mechanisms of DC-Treg cell crosstalk in MS, finally interpreted the complex cell interplay in the manner of inhibitory feedback loops to explore novel therapeutic directions for MS.

Inhibition of miR-let-7i Induces DC Immature Cells and Improves Skin Graft Tolerance

Dendritic cells (DC) initiate the immune response in the body. They can stimulate T cell activation, proliferation, and differentiation and ultimately participate in the immune response and the immune tolerance response. The purpose of this study was to coculture DCs and T cells and subcutaneously inject DCs transfected with miR-let-7i into rhesus monkey transplantations to verify the role of miR-let-7i in allograft immune tolerance. In vitro studies found that the expression of miR-let-7i was upregulated after inducing the maturation of DCs. The low expression of miR-let-7i inhibited the maturation of DCs, promoted the differentiation of T cells into T helper T cells 2 (Th2), and inhibited T helper T cell 1- (Th1-) driven rejection. In vivo studies also obtained similar results, and subcutaneous injection of DCs transfected with miR-let-7i inhibitor prolonged the survival time of allogeneic skin transplantation. Therefore, we conclude that inhibition of miR-let-7i inhibits DC maturation and improves the tolerance of grafted skin.

The Imbalance of Cytokines and Lower Levels of Tregs in Elderly Male Primary Osteoporosis

INTRODUCTION

Osteoporosis (OP) is a debilitating disease that brings a heavy burden to individuals and society with reduced quality of life and lifespan. However, it's frequently overlooked and poorly studied in elderly male patients. Worse still, few anti-osteoporosis drugs are effective at the prevention and treatment of osteoporosis in men. It has been reported that the cells of bone and the immune system share common progenitors, cytokines and growth factors, and that reciprocal interactions occur during health and disease. Nevertheless, the role of immune system in OP is not fully understood, especially in male patients. Therefore, this study aimed to investigate molecular alterations in immune cells in men with OP and to identify immunomodulatory strategies with potential therapeutic value.

MATERIALS AND METHODS

A population of 121 men aged between 51 and 80 years old was recruited. Bone mineral density (BMD) was measured at the lumbar spine L1-4 and femoral neck using dual-energy X-ray absorptiometry (DXA). Twenty people were healthy, 66 people had osteopenia and 35 people had OP. Bone metabolic markers, Th1, Th2, Tregs and immune molecules were evaluated at the time of enrollment.

RESULTS

Smoking was a risk factor for OP. C-terminal crosslinking of type I collagen (β-CTX) and the ratio of receptor activator of nuclear factor-κB ligand (RANKL) to osteoprotegerin (OPG) were higher in OP group, which had lower 25-hydroxyvitamin D [25(OH)D] levels. OP had the higher levels of IL-6 and TNF-α and lower levels of IFN-γ and IL-10. CD4⁺CD25⁺CD127^-/low Tregs were significantly lower in the OP group. The imbalance of Th1/Th2 cells may play an important role in the development of OP. 25(OH)D may play essential roles in maintaining bone health. The low level of Tregs is also one of the underlying immune mechanism that leads to male primary OP.

CONCLUSION

The active function of osteoclasts and the decline in osteoblasts were characteristics of OP, and the imbalance in cytokines and lower levels of Tregs were observed in elderly male patients with primary OP.

Dendritic Cell-Based Immunotherapies and their Potential use in Colorectal Cancer Immunotherapy

Dendritic cells (DCs) are professional antigen-presenting cells, which are resident or proliferating in organs. Major histocompatibility complex (MHC) Class I and II on DCs in normal steady conditions process and present antigens including cancer antigens. Many approaches are used to enhance antigen presentation process of DCs and capture cancer cells. DCs are harvested from cancer patients and manipulated ex vivo in DC-based cancer immunotherapy. In addition, DCs' vaccines and other anticancer therapy combinations were discussed to optimize DCs' efficiency for cancer immunotherapy. This review addressed the use of the human conventional type-1 DCs, OX40⁺ plasmacytoid DCs, and DCs-derived exosomes. In addition, different combinations with DCs therapy such as combination with the monoclonal antibody, cytokine-induced killer cells, adjuvants, chemotherapy (DCs-based chemoimmunotherapy), and nanoparticles were listed and explored for their effectiveness against cancer, and mainly against colorectal cancer.

The role of dendritic cells in cancer and anti-tumor immunity

Dendritic cells (DC) are key sentinels of the host immune response with an important role in linking innate and adaptive immunity and maintaining tolerance. There is increasing recognition that DC are critical determinants of initiating and sustaining effective T-cell-mediated anti-tumor immune responses. Recent progress in immuno-oncology has led to the evolving insight that the presence and function of DC within the tumor microenvironment (TME) may dictate efficacy of cancer immunotherapies as well as conventional cancer therapies, including immune checkpoint blockade, radiotherapy and chemotherapy. As such, improved understanding of dendritic cell immunobiology specifically focusing on their role in T-cell priming, migration into tissues and TME, and the coordinated in vivo responses of functionally specialized DC subsets will facilitate a better mechanistic understanding of how tumor-immune surveillance can be leveraged to improve patient outcomes and to develop novel DC-targeted therapeutic approaches.

Hyaluronan synthesis inhibition impairs antigen presentation and delays transplantation rejection

A coat of pericellular hyaluronan surrounds mature dendritic cells (DC) and contributes to cell-cell interactions. We asked whether 4-methylumbelliferone (4MU), an oral inhibitor of HA synthesis, could inhibit antigen presentation. We find that 4MU treatment reduces pericellular hyaluronan, destabilizes interactions between DC and T-cells, and prevents T-cell proliferation in vitro and in vivo. These effects were observed only when 4MU was added prior to initial antigen presentation but not later, consistent with 4MU-mediated inhibition of de novo antigenic responses. Building on these findings, we find that 4MU delays rejection of allogeneic pancreatic islet transplant and allogeneic cardiac transplants in mice and suppresses allogeneic T-cell activation in human mixed lymphocyte reactions. We conclude that 4MU, an approved drug, may have benefit as an adjunctive agent to delay transplantation rejection.