Regulation of Dendritic Cell Function in Inflammation

Regulated cell death and DAMPs as biomarkers and therapeutic targets in normothermic perfusion of transplant organs. Part 1: their emergence from injuries to the donor organ

This Part 1 of a bipartite review commences with a succinct exposition of innate alloimmunity in light of the danger/injury hypothesis in Immunology. The model posits that an alloimmune response, along with the presentation of alloantigens, is driven by DAMPs released from various forms of regulated cell death (RCD) induced by any severe injury to the donor or the donor organ, respectively. To provide a strong foundation for this review, which examines RCD and DAMPs as biomarkers and therapeutic targets in normothermic regional perfusion (NRP) and normothermic machine perfusion (NMP) to improve outcomes in organ transplantation, key insights are presented on the nature, classification, and functions of DAMPs, as well as the signaling mechanisms of RCD pathways, including ferroptosis, necroptosis, pyroptosis, and NETosis. Subsequently, a comprehensive discussion is provided on major periods of injuries to the donor or donor organs that are associated with the induction of RCD and DAMPs and precede the onset of the innate alloimmune response in recipients. These periods of injury to donor organs include conditions associated with donation after brain death (DBD) and donation after circulatory death (DCD). Particular emphasis in this discussion is placed on the different origins of RCD-associated DAMPs in DBD and DCD and the different routes they use within the circulatory system to reach potential allografts. The review ends by addressing another particularly critical period of injury to donor organs: their postischemic reperfusion following implantation into the recipient-a decisive factor in determining transplantation outcome. Here, the discussion focuses on mechanisms of ischemia-induced oxidative injury that causes RCD and generates DAMPs, which initiate a robust innate alloimmune response.

Smoking negatively impacts ocular surface health and corneal nerve metrics

PURPOSE

To evaluate the effects of smoking on ocular surface through comprehensive analysis of corneal nerves, corneal epithelium, dendritic cells (DCs), and clinical assessments.

METHODS

This cross-sectional study included 250 healthy smokers and 272 healthy non-smokers. Patients' smoking status and duration were recorded. In vivo confocal microscopy was performed to assess 7 quantitative corneal nerves parameters, 3 corneal neuroma parameters, 3 DCs parameters, and 3 epithelial parameters. Ocular surface evaluations included tear break-up time (TBUT), ocular surface and corneal staining, corneal sensitivity, and Schirmer test. Ocular Surface Disease Index questionnaire was used for symptom assessment.

RESULTS

Compared to non-smokers, smokers exhibited significantly lower corneal nerve fiber density (CNFD), nerve branch density, nerve fiber length, nerve total branch density, corneal nerve fiber area (CNFA), and corneal nerve fractal dimension (CFracDim; all p < 0.001). Smokers also presented with a significantly swollen corneal nerve fiber (p < 0.001). Longer smoking duration was significantly associated with lower CNFD (β = -0.04, P = 0.010), lower CNFA (β = -0.00002, P = 0.033), and lower CFracDim (β = -0.0008, P = 0.016). Additionally, a significantly larger neuroma total area (p = 0.040), size (p < 0.001) and perimeter (p < 0.001), as well as a significantly higher DCs density (p < 0.001), DCs count (p = 0.003), and lower DCs elongation which suggested higher DCs maturity (p < 0.001), were observed in the smoking group. Smokers demonstrated significantly higher ocular surface staining scores (p < 0.001) and reduced TBUT (p = 0.001). Corneal epithelial circularity was borderline higher in the smoking subjects (p = 0.059).

CONCLUSIONS

Smoking is associated with significant alterations in corneal nerve morphology and quantity, increased immunological cells, and compromised ocular surface integrity.

Recent Advances in Our Understanding of Human Inflammatory Dendritic Cells in Human Immunodeficiency Virus Infection

Anogenital inflammation is a critical risk factor for HIV acquisition. The primary preventative HIV intervention, pre-exposure prophylaxis (PrEP), is ineffective in blocking transmission in anogenital inflammation. Pre-existing sexually transmitted diseases (STIs) and anogenital microbiota dysbiosis are the leading causes of inflammation, where inflammation is extensive and often asymptomatic and undiagnosed. Dendritic cells (DCs), as potent antigen-presenting cells, are among the first to capture HIV upon its entry into the mucosa, and they subsequently transport the virus to CD4 T cells, the primary HIV target cells. This increased HIV susceptibility in inflamed tissue likely stems from a disrupted epithelial barrier integrity, phenotypic changes in resident DCs and an influx of inflammatory HIV target cells, including DCs and CD4 T cells. Gaining insight into how HIV interacts with specific inflammatory DC subsets could inform the development of new therapeutic strategies to block HIV transmission. However, little is known about the early stages of HIV capture and transmission in inflammatory environments. Here, we review the currently characterised inflammatory-tissue DCs and their interactions with HIV.

RAD001-mediated mTOR targeting in human monocyte-derived dendritic cells shifts them toward an immunogenic phenotype

Dendritic cells (DCs) are essential for promoting T lymphocyte responses since they are specialist antigen-presenting cells. In order to maintain tolerance or initiate immune responses, DCs must be activated in a balanced and regulated manner via diverse signaling pathways. By using a variety of pharmacological components, we can interfere with their different signaling pathways such as the mammalian target of rapamycin (mTOR) to appropriately modulate DC activity. In the current study, we administered RAD001 to DCs to examine the impact of mTOR inhibition on both the maturation stage and the expression of inflammatory and anti-inflammatory molecules in DCs. Pure monocytes were cultivated and stimulated with GM-CSF and IL-4 to generate immature DCs, which were then treated with RAD001. The phenotype of the DCs was determined by labeling surface markers and analyzing them using flow cytometry. Afterward, real-time PCR was carried out to evaluate the expression of inflammatory and anti-inflammatory genes. The administration of RAD001 to DCs led to a significant upregulation in the gene expression of inflammatory molecules such as IL-12, IL-1β, tumor necrosis factor (TNF)-α, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-KB). Conversely, RAD001 treatment resulted in a decrease in the gene expression of anti-inflammatory factors IL-10 and indoleamine 2,3-dioxygenase (IDO). However, the expression of differentiation and antigen presentation-related markers CD11c and human leukocyte antigens (HLA)-DR in RAD001-treated DCs was lower and higher compared to the control group that did not receive the treatment, respectively. Taken together, our findings indicated that RAD001 treatment of DCs can be a promising therapeutic approach for the generation of immunogenic DCs in order to barricade tumor growth. However, there is a need for further investigation to evaluate the impacts of mTOR inhibition by RAD001 in DCs on cellular immune responses in vitro and in vivo.

Cytokine-overexpressing dendritic cells for cancer immunotherapy

Dendritic cells (DCs), the main type of antigen-presenting cells in the body, act as key mediators of adaptive immunity by sampling antigens from diseased cells for the subsequent priming of antigen-specific T and B cells. While DCs can secrete a diverse array of cytokines that profoundly shape the immune milieu, exogenous cytokines are often needed to maintain the survival, proliferation, and differentiation of DCs, T cells, and B cells. However, conventional cytokine therapies for cancer treatment are limited by their low therapeutic benefit and severe side effects. The overexpression of cytokines in DCs, followed by paracrine release or membrane display, has emerged as a viable approach for controlling the exposure of cytokines to interacting DCs and T/B cells. This approach can potentially reduce the necessary dose of cytokines and associated side effects to achieve comparable or enhanced antitumor efficacy. Various strategies have been developed to enable the overexpression or chemical conjugation of cytokines on DCs for the subsequent modulation of DC-T/B-cell interactions. This review provides a brief overview of strategies that enable the overexpression of cytokines in or on DCs via genetic engineering or chemical modification methods and discusses the promise of cytokine-overexpressing DCs for the development of new-generation cancer immunotherapy.

Control of myeloid cell functions by nociceptors

The immune system has evolved to protect the host from infectious agents, parasites, and tumor growth, and to ensure the maintenance of homeostasis. Similarly, the primary function of the somatosensory branch of the peripheral nervous system is to collect and interpret sensory information about the environment, allowing the organism to react to or avoid situations that could otherwise have deleterious effects. Consequently, a teleological argument can be made that it is of advantage for the two systems to cooperate and form an “integrated defense system” that benefits from the unique strengths of both subsystems. Indeed, nociceptors, sensory neurons that detect noxious stimuli and elicit the sensation of pain or itch, exhibit potent immunomodulatory capabilities. Depending on the context and the cellular identity of their communication partners, nociceptors can play both pro- or anti-inflammatory roles, promote tissue repair or aggravate inflammatory damage, improve resistance to pathogens or impair their clearance. In light of such variability, it is not surprising that the full extent of interactions between nociceptors and the immune system remains to be established. Nonetheless, the field of peripheral neuroimmunology is advancing at a rapid pace, and general rules that appear to govern the outcomes of such neuroimmune interactions are beginning to emerge. Thus, in this review, we summarize our current understanding of the interaction between nociceptors and, specifically, the myeloid cells of the innate immune system, while pointing out some of the outstanding questions and unresolved controversies in the field. We focus on such interactions within the densely innervated barrier tissues, which can serve as points of entry for infectious agents and, where known, highlight the molecular mechanisms underlying these interactions.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

Evaluation of corneal nerves and dendritic cells by in vivo confocal microscopy after Descemet's membrane keratoplasty for bullous keratopathy

This study evaluated changes in corneal nerves and the number of dendritic cells (DCs) in corneal basal epithelium following Descemet membrane endothelial keratoplasty (DMEK) surgery for bullous keratopathy (BK). Twenty-three eyes from 16 consecutive patients that underwent DMEK for BK were included. Eyes of age-matched patients that underwent pre-cataract surgery (12 eyes) were used as controls. In vivo confocal microscopy was performed pre- and postoperatively at 6, 12, and 24 months. Corneal nerve length, corneal nerve trunks, number of branches, and the number of DCs were determined. The total corneal nerve length of 1634.7 ± 1389.1 μm/mm² before surgery was significantly increased in a time-dependent manner to 4485.8 ± 1403.7 μm/mm², 6949.5 ± 1477.1 μm/mm², and 9389.2 ± 2302.2 μm/mm² at 6, 12, and 24 months after DMEK surgery, respectively. The DC density in BK cornea pre- and postoperatively at 6 months was significantly higher than in the controls, and decreased postoperatively at 12 and 24 months and was significantly lower than that at 6 months postoperatively. Thus, our results suggest that DMEK can repair and normalize the corneal environment.

Sestrin2 protects dendrite cells against ferroptosis induced by sepsis

Ferroptosis is a nonapoptotic form of programmed cell death triggered by the accumulation of reactive oxygen species (ROS) depended on iron overload. Although most investigations focus on the relationship between ferroptosis and cancer, neurodegenerative diseases, and ischemia/reperfusion injury, research on ferroptosis induced by immune-related inflammatory diseases, especially sepsis, is scarce. Sestrin2 (Sesn2), a highly evolutionary and stress-responsive protein, is critically involved in defense against oxidative stress challenges. Upregulated expression of Sesn2 has been observed in preliminary experiments to have an antioxidative function in the context of an inflammatory response. Nevertheless, the underlying function of Sesn2 in inflammation-mediated ferroptosis in the immune system remains uncertain. The current study aimed to demonstrate the protective effect of Sesn2 on ferroptosis and even correlations with ferroptosis and the functions of ferroptotic-dendritic cells (DCs) stimulated with lipopolysaccharide (LPS). The mechanism underlying DCs protection from LPS-induced ferroptosis by Sesn2 was further explored in this study. We found that the immune response of DCs assessed by co-stimulatory phenotypes was gradually enhanced at the peak time of 12 h upon 1 μg/ml LPS stimulation while ferroptosis in DCs treated with LPS at 24 h was significantly detected. LPS-induced ferroptosis showed a suppressive impact on DCs in phenotypic maturation, which was conversely relieved by the ferroptotic inhibitor. Compared with wild-type (WT) mice, DCs in genetic defective mice of Sesn2 (Sesn2-/-) exhibited exacerbated ferroptosis. Furthermore, the protective effect of Sesn2 on ferroptosis was noticed to be associated with the ATF4-CHOP-CHAC1 pathway, eventually exacerbating ferroptosis by degrading of glutathione. These results indicate that Sesn2 can suppress the ferroptosis of DCs in sepsis by downregulating the ATF4-CHOP-CHAC1 signaling pathway, and it might play an antioxidative role.

Metabolomic and lipidomic signatures associated with activation of human cDC1 (BDCA3+ /CD141+ ) dendritic cells

Dendritic cells (DCs) bridge the connection between innate and adaptive immunity. DCs present antigens to T cells and stimulate potent cytotoxic T‐cell responses. Metabolic reprogramming is critical for DC development and activation; however, metabolic adaptations and regulation in DC subsets remains largely uncharacterized. Here, we mapped metabolomic and lipidomic signatures associated with the activation phenotype of human conventional DC type 1, a DC subset specialized in cross‐presentation and therefore of major importance for the stimulation of CD8⁺ T cells. Our metabolomics and lipidomic analyses showed that Toll‐like receptor (TLR) stimulation altered glycerolipids and amino acids in cDC1. Poly I:C or pRNA stimulation reduced triglycerides and cholesterol esters, as well as various amino acids. Moreover, TLR stimulation reduced expression of glycolysis‐regulating genes and did not induce glycolysis. Conversely, cDC1 exhibited increased mitochondrial content and oxidative phosphorylation (OXPHOS) upon TLR3 or TLR7/8 stimulation. Our findings highlight the metabolic adaptations required for cDC1 maturation.

Characterization and comparison of innate and adaptive immune responses at vaccine sites in melanoma vaccine clinical trials

The strength and durability of systemic anti-tumor immune responses induced by cancer vaccines depends on adjuvants to support an immunogenic vaccine site microenvironment (VSME). Adjuvants include water-in-oil emulsions with incomplete Freund's adjuvant (IFA) and combinations of toll-like receptor (TLR) agonists, including a preparation containing TLR4 and TLR9 agonists with QS-21 (AS15). IFA-containing vaccines can promote immune cell accumulation at the VSME, whereas effects of AS15 are largely unexplored. Therefore, we assessed innate and adaptive immune cell accumulation and gene expression at the VSME after vaccination with AS15 and compared to effects with IFA. We hypothesized that AS15 would promote less accumulation of innate and adaptive immune cells at the VSME than IFA vaccines. In two clinical trials, patients with resected high-risk melanoma received either a multipeptide vaccine with IFA or a recombinant MAGE-A3 protein vaccine with AS15. Vaccine site biopsies were obtained after one or multiple vaccines. T cells accumulated early after vaccines with AS15, but this was not durable or of the same magnitude as vaccination in IFA. Vaccines with AS15 increased durable expression of DC- and T cell-related genes, as well as PD-L1 and IDO1, suggesting complex activation and regulation of innate and adaptive immune function with AS15. These changes were generally greater with vaccines containing IFA, but IFA induced reduction in myeloid suppressor cells markers. Evidence of tertiary lymphoid structure (TLS) formation was observed with both adjuvants. Our findings highlight adjuvant-dependent changes in immune features at the VSME that may impact systemic immune responses.

The Enhancing Effect of Fungal Immunomodulatory Protein-Volvariella Volvacea (FIP-vvo) on Maturation and Function of Mouse Dendritic Cells

Volvariella volvacea, also known as straw mushroom, is a common edible mushroom in Chinese cuisine. It contains many nutrients for human health. A fungal immunomodulatory protein (FIP) has been isolated from V. volvacea and named FIP-vvo. Although the regulatory effects of many FIPs on immunity have been identified, the impact of FIP-vvo in modulating dendritic cells (DCs), which play a key role to connect the innate and the adaptive immunity, is not known. In this study, we aim to study the effect of FIP-vvo on the DC maturation and function. We found that FIP-vvo slightly increased the generation of CD11c⁺ bone marrow-derived DC (BMDC). In addition, the surface expression of MHCII was promoted in BMDCs after the treatment of FIP-vvo, suggesting that FIP-vvo induces DC maturation. Furthermore, FIP-vvo enhanced the ability of BMDCs to activate antigen-specific T cell responses in vitro. In the in vivo study, the FIP-vvo treatment facilitated T cell response in lymph nodes. Therefore, for the first time, our data demonstrated that FIP-vvo promoted DC maturation and function and suggested that FIP-vvo could have benefits for human health by enhancing immunity.

Zymosan enhances in vitro phagocyte function and the immune response of mice infected with Paracoccidioides brasiliensis

Paracoccidioides brasiliensis is the major etiologic agent of Paracoccidioidomycosis (PCM), the most frequent human deep mycosis in Latin America. It is proposed that masking of β-glucan in P. brasiliensis cell wall is a critical virulence factor that contributes to the development of a chronic disease characterized by a long period of treatment, which is usually toxic. In this context, the search for immunomodulatory agents for therapeutic purposes is highly desirable. One strategy is to use pattern recognition receptors (PRRs) ligands to stimulate the immune response mediated by phagocytes. Here, we sought to evaluate if Zymosan, a β-glucan-containing ligand of the PRRs Dectin-1/TLR-2, would enhance phagocyte function and the immune response of mice challenged with P. brasiliensis. Dendritic cells (DCs) infected with P. brasiliensis and treated with Zymosan showed improved secretion of several proinflammatory cytokines and expression of maturation markers. In addition, when cocultured with splenic lymphocytes, these cells induced the production of a potential protective type 1 and 17 cytokine patterns. In macrophages, Zymosan ensued a significant fungicidal activity associated with nitric oxide production and phagolysosome acidification. Importantly, we observed a protective effect of Zymosan-primed DCs delivered intranasally in experimental pulmonary PCM. Overall, our findings support the potential use of β-glucan-containing compounds such as Zymosan as an alternative or complementary antifungal therapy.

LAY SUMMARY

We report for the first time that Paracoccidioides brasiliensis-infected phagocytes treated with Zymosan (cell wall extract from bakers' yeast) show enhanced cytokine production, maturation, and fungal killing. Also, Zymosan-primed phagocytes induce a protective immune response in infected mice.

Thyroid Hormone and Deiodination in Innate Immune Cells

Thyroid hormone has recently been recognized as an important determinant of innate immune cell function. Highly specialized cells of the innate immune system, including neutrophils, monocytes/macrophages, and dendritic cells, are capable of identifying pathogens and initiating an inflammatory response. They can either phagocytose and kill microbes, or recruit other innate or adaptive immune cells to the site of inflammation. Innate immune cells derive from the hematopoietic lineage and are generated in the bone marrow, from where they can be recruited into the blood and tissues in the case of infection. The link between the immune and endocrine systems is increasingly well established, and recent studies have shown that innate immune cells can be seen as important thyroid hormone target cells. Tight regulation of cellular thyroid hormone availability and action is performed by thyroid hormone transporters, receptors, and the deiodinase enzymes. Innate immune cells express all these molecular elements of intracellular thyroid hormone metabolism. Interestingly, there is recent evidence for a causal relationship between cellular thyroid hormone status and innate immune cell function. This review describes the effects of modulation of intracellular thyroid hormone metabolism on innate immune cell function, specifically neutrophils, macrophages, and dendritic cells, with a special focus on the deiodinase enzymes. Although there are insufficient data at this stage for conclusions on the clinical relevance of these findings, thyroid hormone metabolism may partially determine the innate immune response and, by inference, the clinical susceptibility to infections.

Murine hepatoma treatment with mature dendritic cells stimulated by Trichinella spiralis excretory/secretory products

Excretory/Secretory Products (ESPs) of the nematode Trichinella spiralis contain antitumor-active substances that inhibit tumor growth. Mature dendritic cells (DCs) play a critical role in the antitumor immunity of the organism. As pathogen-derived products, it ought to be discussed whether T. spiralis ESPs will reduce the antitumor effect of mature DCs from the host before it is applied to patients' tumors. Therefore, the aim of this work was to evaluate the immunological effect of DCs stimulated by T. spiralis ESPs in H22 tumor-bearing mice. H22 tumor model mice in this study were randomly divided into four groups according to the treatment: PBS control group, ESP group, DCs group, and DCs stimulated with T. spiralis ESP (ESP+DCs group). The antitumor effect was evaluated by tumor inhibition rate and cytokine detection using ELISA. The results showed significant inhibition in tumor growth in the ESP+DCs, DCs and ESP groups when compared with the PBS control group (p < 0.01, p < 0.01, and p < 0.05, respectively). However, no significant difference was observed on tumor inhibition rates between the ESP+DCs and DCs groups. The decrease in IL-4, IL-6, and IL-10, and the increase in IFN-γ between the DCs and ESP+DCs groups were also not significant. Therefore, DCs stimulated by ESP did not reduce the antitumor effect of mature DCs, which demonstrated that the T. spiralis ESP would not affect the antitumor effect of mature DCs by modulating the immune response of the host, and that ESPs are safe in antitumor immunology when applied in a tumor model mice.

Dendritic Cells Currently under the Spotlight; Classification and Subset Based upon New Markers

Dendritic cells (DCs) are considered as a subset of mononuclear phagocytes that composed of multiple subsets with distinct phenotypic features. DCs play crucial roles in the initiation and modulation of immune responses to both allo- and auto-antigens during pathogenic settings, encompassing infectious diseases, cancer, autoimmunity, transplantation, as well as vaccination. DCs play a role in preventing autoimmunity via inducing tolerance to self-antigens. This review focus on the most common subsets of DCs in human. Owing to the low frequencies of DC cells in blood and tissues and also the lack of specific DC markers, studies of DCs have been greatly hindered. Human DCs arise by a dedicated pathway of lympho-myeloid hematopoiesis and give rise into specialized subtypes under the influence of transcription factors that are specific for each linage. In humans, the classification of DCs has been generally separated into the blood and cutaneous subsets, mainly because these parts are more comfortable to examine in humans.

High salt diet accelerates the progression of murine lupus through dendritic cells via the p38 MAPK and STAT1 signaling pathways

The increased incidence of systemic lupus erythematosus (SLE) in recent decades might be related to changes in modern dietary habits. Since sodium chloride (NaCl) promotes pathogenic T cell responses, we hypothesize that excessive salt intake contributes to the increased incidence of autoimmune diseases, including SLE. Given the importance of dendritic cells (DCs) in the pathogenesis of SLE, we explored the influence of an excessive sodium chloride diet on DCs in a murine SLE model. We used an induced lupus model in which bone marrow-derived dendritic cells (BMDCs) were incubated with activated lymphocyte-derived DNA (ALD-DNA) and transferred into C57BL/6 recipient mice. We observed that a high-salt diet (HSD) markedly exacerbated lupus progression, which was accompanied by increased DC activation. NaCl treatment also stimulated the maturation, activation and antigen-presenting ability of DCs in vitro. Pretreatment of BMDCs with NaCl also exacerbated BMDC-ALD-DNA-induced lupus. These mice had increased production of autoantibodies and proinflammatory cytokines, more pronounced splenomegaly and lymphadenopathy, and enhanced pathological renal lesions. The p38 MAPK–STAT1 pathway played an important role in NaCl-induced DC immune activities. Taken together, our results demonstrate that HSD intake promotes immune activation of DCs through the p38 MAPK–STAT1 signaling pathway and exacerbates the features of SLE. Thus, changes in diet may provide a novel strategy for the prevention or amelioration of lupus or other autoimmune diseases.

Sestrin2 protects dendritic cells against endoplasmic reticulum stress-related apoptosis induced by high mobility group box-1 protein

Sestrin2 (SESN2) is a highly evolutionary conserved protein and involved in different cellular responses to various stresses. However, the potential function of SESN2 in immune system remains unclear. The present study was designed to test whether dendritic cells (DCs) could express SESN2, and investigate the underlying molecular mechanism as well as its potential significance. Herein, we firstly reported that SESN2 was expressed in DCs after high mobility group box-1 protein (HMGB1) stimulation and the apoptosis of DCs was obviously increased when SESN2 gene silenced by siRNA. Cells undergone SESN2-knockdown promoted endoplasmic reticulum (ER) stress (ERS)-related cell death, markedly exacerbated ER disruption as well as the formation of dilated and aggregated structures, and they significantly aggravated the extent of ERS response. Conversely, overexpressing SESN2 DCs markedly decreased apoptotic rates and attenuated HMGB1-induced ER morphology fragment together with inhibition of ERS-related protein translation. Furthermore, sesn2^−/−-deficient mice manifested increased DC apoptosis and aggravated ERS extent in septic model. These results indicate that SESN2 appears to be a potential regulator to inhibit apoptotic ERS signaling that exerts a protective effect on apoptosis of DCs in the setting of septic challenge.

Role of microRNAs in the Regulation of Dendritic Cell Generation and Function

Dendritic cells (DCs) are antigen-presenting cells with a key role in immune responses. They act as a link between the innate and adaptive systems and they can induce and maintain immunologic tolerance. DCs are subdivided into conventional and plasmacytoid DCs. These cell subsets originate from the same bone marrow precursors and their differentiation process is determined by several extrinsic and intrinsic factors, such as cytokines, transcription factors, and miRNAs. miRNAs are small non-coding RNAs that play a crucial role in modulating physiological and pathological processes mediated by DCs. miRNA deregulation affects many inflammatory conditions and diseases. The aim of this review was to underline the importance of miRNAs in inflammatory processes mediated by DCs in physiological and pathological conditions and to highlight their potential application for future therapies.

Activated γδ T Cells Promote Dendritic Cell Maturation and Exacerbate the Development of Experimental Autoimmune Uveitis (EAU) in Mice

Our previous study reveals that gamma delta (γδ) T cells were activated and dendritic cells (DCs) underwent maturation during the inflammation phase in experimental autoimmune uveitis (EAU) mice, and the interaction between DCs and γδ T cells may significantly exacerbate the development of EAU. However, the interactions between DCs and γδ T cells that can affect DCs maturation to influence EAU development must be further addressed. In this study we showed that mature DC numbers in TCR-δ^-/- (KO) EAU mice were lower than those in wild-type (WT) C57BL/6 (B6) mice. The γδ T cells harvested from WT EAU mice secreted more interferon-γ (IFN-γ), however, after blocking IFN-γ, the maturation of DCs was significantly downregulated. By contrast, the percentage of IFN-γ- and IL-17-producing CD4⁺ T cells in KO EAU mice decreased to a greater extent than that in WT EAU mice during the inflammatory phase. Additionally, the levels of IFN-γ/IL-17 in serum were in agreement with those of CD4⁺ T cells. Furthermore, after activated γδ T cells injection, the inflammatory symptoms of EAU mice were more aggravated. In vitro co-cultures of both cell types showed that activated γδ T cells may induce DCs to generate higher levels of intracellular cell adhesion molecule-1 (ICAM-1/CD54), CD80, CD83, and CD86. Moreover, co-culture of the two cells may induce the activation of CD4⁺ T cells. Taken together, our results demonstrated that activated γδ T cells may promote DCs maturation and further enhance the generation of Th1/Th17 cells in EAU mice, resulting in exacerbated EAU.

Extracellular Vesicles as Mediators of Cellular Crosstalk Between Immune System and Kidney Graft

Extracellular vesicles (EVs) are known immune-modulators exerting a critical role in kidney transplantation (KT). EV bioactive cargo includes graft antigens, costimulatory/inhibitory molecules, cytokines, growth factors, and functional microRNAs (miRNAs) that may modulate expression of recipient cell genes. As paracrine factors, neutrophil- and macrophage-derived EVs exert immunosuppressive and immune-stimulating effects on dendritic cells, respectively. Dendritic cell-derived EVs mediate alloantigen spreading and modulate antigen presentation to T lymphocytes. At systemic level, EVs exert pleiotropic effects on complement and coagulation. Depending on their biogenesis, they can amplify complement activation or shed complement inhibitors and prevent cell lysis. Likewise, endothelial- and platelet-derived EVs can exert procoagulant/prothrombotic effects and also promote endothelial survival and angiogenesis after ischemic injury. Kidney endothelial- and tubular-derived EVs play a key role in ischemia-reperfusion injury (IRI) and during the healing process; additionally, they can trigger rejection by inducing both alloimmune and autoimmune responses. Endothelial EVs have procoagulant/pro-inflammatory effects and can release sequestered self-antigens, generating a tissue-specific autoimmunity. Renal tubule-derived EVs shuttle pro-fibrotic mediators (TGF-β and miR-21) to interstitial fibroblasts and modulate neutrophil and T-lymphocyte influx. These processes can lead to peritubular capillary rarefaction and interstitial fibrosis-tubular atrophy. Different EVs, including those from mesenchymal stromal cells (MSCs), have been employed as a therapeutic tool in experimental models of rejection and IRI. These particles protect tubular and endothelial cells (by inhibition of apoptosis and inflammation-fibrogenesis or by inducing autophagy) and stimulate tissue regeneration (by triggering angiogenesis, cell proliferation, and migration). Finally, urinary and serum EVs represent potential biomarkers for delayed graft function (DGF) and acute rejection. In conclusion, EVs sustain an intricate crosstalk between graft tissue and innate/adaptive immune systems. EVs play a major role in allorecognition, IRI, autoimmunity, and alloimmunity and are promising as biomarkers and therapeutic tools in KT.

Immunomodulatory effects of Rhipicephalus haemaphysaloides serpin RHS2 on host immune responses

Background

Rhipicephalus haemaphysaloides is a widespread tick species in China and other South East Asian countries, where it is the vector of many pathogens. The objective of this study was to study the role of serpin (serine protease inhibitor) during the tick-host interaction.

Methods

The differentiation of bone marrow-derived dendritic cells (BMDC) was induced in vitro, and the effect of RHS2 on the maturation of DCs was evaluated. The effects of RHS2 on T cell activation and cytotoxic T lymphocytes’ (CTLs) activity were analyzed by flow cytometry. Antibody subtypes after immunization of mice with RHS2 and OVA were determined.

Results

RHS2 can inhibit the differentiation of bone marrow-derived cells into DCs and promote their differentiation into macrophages. RHS2 can inhibit the maturation of DCs and the expression of CD80, CD86 and MHCII. The number of CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells secreting IFN-γ, IL-2 and TNF-α was decreased, and the number of CD3⁺CD4⁺ T cells secreting IL-4 was increased, indicating that RHS2 can inhibit the activation of CD4 T cells and CD8 T cells, leading to inhibition of Th1 immune response. RHS2 inhibits the elimination of target cells by cytotoxic T lymphocytes. After immunization of mice with RHS2 and OVA, serum IgG2b was significantly reduced and IgM was increased.

Conclusions

The results show that RHS2 has an inhibitory effect on the host immune response. Ticks have evolved various ways to circumvent adaptive immunity. Their serpin inhibits BMDC differentiation to reduce immune responses.

Extracellular ATP activates P2X7R-NF-κB (p65) pathway to promote the maturation of bone marrow-derived dendritic cells of mice

The maturation state of dendritic cell (DC) plays an important role in immune activities. Previously we had found that NF-κB (p65) pathway could promote DC maturation and subsequent immune effects. But the upstream mechanism of this pathway was still unclear. Extracellular adenosine triphosphate (ATP) activating its receptor P2X7R has recently been considered as the fourth signal to activate T lymphocytes. Here we aimed to find out the connection between P2X7R and NF-κB (p65) pathway in DC maturation. Results showed that the expression of P2X7R and the intracellular ATP levels were increased along with the maturation of DC. P2X7R agonist stimulated the morphological changes of DCs into the appearance of mature DCs, and promoted the expression of NF-κB (p65), as well as the release of IFN-γ and IL-12. Whereas, P2X7R inhibitor had the opposite influences. Co-immunoprecipitation assay confirmed the binding of P2X7R and NF-κB (p65). Our study suggested that extracellular ATP could promote DC maturation and release of inflammatory cytokines through the binding of P2X7R and NF-κB (p65). This is the first study to show the P2X7R-NF-κB (p65) pathway in DC. Interference with this pathway may be able to regulate immune responses in areas like infectious diseases, inflammation, transplantation, tumor and autoimmune diseases. In addition, intracellular ATP level could be a new indicator of the maturation state of DC.

Leishmania infantum LeIF and its recombinant polypeptides induce the maturation of dendritic cells in vitro: An insight for dendritic cells based vaccine

We previously showed that recombinant Leishmania infantum eukaryotic initiation factor (LieIF) was able to induce the secretion of cytokines IL-12, IL-10 and TNF-α by human monocytes. In this study, we explored in vitro the potential of LieIF to induce phenotypic maturation and functional differentiation of murine bone-marrow derived dendritic cells (BM-DCs). Moreover, in order to identify potential immunnomodulatory regions of LieIF, eight recombinant overlapping protein fragments covering the whole amino acid sequence of protein, were constructed and assessed in vitro for their ability to induce maturation of BM-DCs. Our data showed that LieIF and some of its recombinant polypeptides were able to induce elevated expression of CD40, CD80 and CD86 co-stimulatory molecules with concurrent IL-12 production. Moreover, we used an in vivo experimental model of cutaneous leishmaniasis consisted of susceptible Leishmania major-infected BALB/c mice and we demonstrated that LieIF-pulsed-BM-DCs adoptively transferred in mice were capable to confer protection against a high dose parasite challenge. This study further describes the immunomodulatory properties of LieIF and its polypeptides bringing relevant information for their exploitation as candidate molecules for vaccine development against leishmaniasis.

Immune-Modulation by the Human Respiratory Syncytial Virus: Focus on Dendritic Cells

The human respiratory syncytial virus (hRSV) is the leading cause of pneumonia in infants and produces a significant burden in the elderly. It can also infect and produce disease in otherwise healthy adults and recurrently infect those previously exposed to the virus. Importantly, recurrent infections are not necessarily a consequence of antigenic variability, as described for other respiratory viruses, but most likely due to the capacity of this virus to interfere with the host's immune response and the establishment of a protective and long-lasting immunity. Although some genes encoded by hRSV are known to have a direct participation in immune evasion, it seems that repeated infection is mainly given by its capacity to modulate immune components in such a way to promote non-optimal antiviral responses in the host. Importantly, hRSV is known to interfere with dendritic cell (DC) function, which are key cells involved in establishing and regulating protective virus-specific immunity. Notably, hRSV infects DCs, alters their maturation, migration to lymph nodes and their capacity to activate virus-specific T cells, which likely impacts the host antiviral response against this virus. Here, we review and discuss the most important and recent findings related to DC modulation by hRSV, which might be at the basis of recurrent infections in previously infected individuals and hRSV-induced disease. A focus on the interaction between DCs and hRSV will likely contribute to the development of effective prophylactic and antiviral strategies against this virus.

The role of ocular dendritic cells in uveitis

Dendritic cells (DCs) act as a bridge between innate and adoptive immunity. They are widely distributed in various tissues and organs. Resident ocular DCs are found in the peripheral margins and juxtapapillary areas of the retina, usually in an immature state. During inflammation, DCs are activated and participate in the development of uveitis, an ocular inflammatory disease. Herein, the characteristics and status of DCs in uveitis, the possible factors affecting the status of DCs, and the clinical methods for detecting the DCs in patients are described.

Proanthocyanidins: novel treatment for psoriasis that reduces oxidative stress and modulates Th17 and Treg cells

Psoriasis is a common, chronic, inflammatory skin disease that affects 2%-4% of the global population. Recent studies have shown that increased oxidative stress (OS) and T-cell abnormalities are central to the pathogenesis of this disease. The resulting reactive oxygen species (ROS) induces proliferation and differentiation of Th17/Th1/Th22 cells and inhibits the anti-inflammatory activities of regulatory T lymphocytes (Treg). Subsequent secretions of inflammatory cytokines, such as interleukin (IL)-17, IL-22, tumor necrosis factor alpha (TNF-α), and interferon-gamma (IFN-γ), and vascular endothelial growth factor (VEGF), stimulate keratinocyte proliferation and angiogenesis. Proanthocyanidins are a class of flavonoids from plants and fruits, and have various antioxidant, anti-inflammatory, and anti-angiogenic properties. Numerous reports have demonstrated therapeutic effects of proanthocyanidins for various diseases. Among clinical activities, proanthocyanidins suppress cell proliferation, prevent OS, and regulate Th17/Treg cells. Because the pathogenesis of psoriasis involves OS and T cells dysregulation, we reviewed the effects of proanthocyanidins on OS, Th17 and Treg cell activities, and keratinocyte proliferation and angiogenesis. Data from multiple previous studies warrant consideration of proanthocyanidins as a promising strategy for the treatment of psoriasis.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Severity of Sjögren's Syndrome Keratoconjunctivitis Sicca Increases with Increased Percentage of Conjunctival Antigen-Presenting Cells

This study investigated the relationship between clinical severity and percentage of conjunctival antigen-presenting cells (APCs) in Sjögren’s syndrome (SS)-associated keratoconjunctivitis sicca (KCS). KCS clinical severity was based on symptom severity, tear volume, tear break-up time, and ocular surface dye staining. Conjunctival goblet cell density (GCD) was measured in periodic acid Schiff (PAS)-stained membranes. Conjunctival cells obtained by impression cytology were used for flow cytometry to measure percentages of CD45⁺HLA-DR⁺ APCs and mature CD11c⁺CD86⁺ dendritic cells (DCs). Compared to normal conjunctiva, the percentages of HLA-DR⁺ and CD11c⁺CD86⁺ cells were higher in the conjunctiva of the KCS group (p < 0.05). The percentage of CD45⁺HLA-DR⁺ cells positively correlated with clinical severity (r = 0.71, p < 0.05) and negatively correlated with GCD (r = −0.61, p < 0.05). Clinical severity also negatively correlated with GCD (r = −0.54, p < 0.05). These findings indicate that a higher percentage of APCs and mature DCs in the conjunctiva is associated with more severe KCS in SS. These APCs may contribute to the generation of the pathogenic Th1 cells that cause goblet cell loss in KCS.

The role of extracellular vesicles when innate meets adaptive

Innate immune cells are recognized for their rapid and critical contribution to the body's first line of defense against invading pathogens and harmful agents. These actions can be further amplified by specific adaptive immune responses adapted to the activating stimulus. Recently, the awareness has grown that virtually all innate immune cells, i.e., mast cells, neutrophils, macrophages, eosinophils, basophils, and NK cells, are able to communicate with dendritic cells (DCs) and/or T and B cells, and thereby significantly contribute to the orchestration of adaptive immune responses. The means of communication that are thus far primarily associated with this function are cell-cell contacts and the release of a broad range of soluble mediators. Moreover, the possible contribution of innate immune cell-derived extracellular vesicles (EVs) to the modulation of adaptive immunity will be outlined in this review. EVs are submicron particles composed of a lipid bilayer, proteins, and nucleic acids released by cells in a regulated fashion. EVs are involved in intercellular communication between multiple cell types, including those of the immune system. A good understanding of the mechanisms by which innate immune cell-derived EVs influence adaptive immune responses, or vice versa, may reveal novel insights in the regulation of the immune system and can open up new possibilities for EVs (or their components) in controlling immune responses, either as a therapy, target, or as an adjuvant in future immune modulating treatments.

Characterization of reconstructed human skin containing Langerhans cells to monitor molecular events in skin sensitization

Human cell-based approaches to assess defined key events in allergic contact dermatitis (ACD) are well-established, but lack cutaneous penetration and biotransformation as well as cellular cross-talk. Herein, we integrated in vitro-generated immature MUTZ-3-derived Langerhans-like cells (MUTZ-LCs) or monocyte-derived LC-like cells (MoLCs) into reconstructed human skin (RHS), consistent of a stratified epidermis formed by primary keratinocytes on a dermal compartment with collagen-embedded primary fibroblasts. LC-like cells were mainly localized in the epidermal compartment and distributed homogenously in accordance with native human skin. Topical application of the strong contact sensitizer 2,4-dinitrochlorobenzene (DNCB) induced IL-6 and IL-8 secretion in RHS with LC-like cells, whereas no change was observed in reference models. Increased gene expression of CD83, PD-L1, and CXCR4 in the dermal compartment indicated LC maturation. Importantly, exposure to DNCB enhanced mobility of the LC-like cells from epidermal to dermal compartments. In response to the moderate sensitizer isoeugenol and irritant sodium dodecyl sulphate, the obtained response was less pronounced. In summary, we integrated immature and functional MUTZ-LCs and MoLCs into RHS and provide a unique comparative experimental setting to monitor early events during skin sensitization.

Synergistic effects of dendritic cell targeting and laser-microporation on enhancing epicutaneous skin vaccination efficacy

Due to its unique immunological properties, the skin is an attractive target tissue for allergen-specific immunotherapy. In our current work, we combined a dendritic cell targeting approach with epicutaneous immunization using an ablative fractional laser to generate defined micropores in the upper layers of the skin. By coupling the major birch pollen allergen Bet v 1 to mannan from S. cerevisiae via mild periodate oxidation we generated hypoallergenic Bet-mannan neoglycoconjugates, which efficiently targeted CD14⁺ dendritic cells and Langerhans cells in human skin explants. Mannan conjugation resulted in sustained release from the skin and retention in secondary lymphoid organs, whereas unconjugated antigen showed fast renal clearance. In a mouse model, Bet-mannan neoglycoconjugates applied via laser-microporated skin synergistically elicited potent humoral and cellular immune responses, superior to intradermal injection. The induced antibody responses displayed IgE-blocking capacity, highlighting the therapeutic potential of the approach. Moreover, application via micropores, but not by intradermal injection, resulted in a mixed TH1/TH17-biased immune response. Our data clearly show that applying mannan-neoglycoconjugates to an organ rich in dendritic cells using laser-microporation is superior to intradermal injection. Due to their low IgE binding capacity and biodegradability, mannan neoglycoconjugates therefore represent an attractive formulation for allergen-specific epicutaneous immunotherapy.

In silico analysis and in vitro evaluation of immunogenic and immunomodulatory properties of promiscuous peptides derived from Leishmania infantum eukaryotic initiation factor

It is generally considered as imperative the ability to control leishmaniasis through the development of a protective vaccine capable of inducing long-lasting and protective cell-mediated immune responses. In this current study, we demonstrated potential epitopes that bind to H2 MHC class I and II molecules by conducting the in silico analysis of Leishmania infantum eukaryotic Initiation Factor (LieIF) protein, using online available algorithms. Moreover, we synthesized five peptides (16-18 amino acids long) which are part of the N-terminal portion of LieIF and contain promising MHC class I and II-restricted epitopes and afterwards, their predicted immunogenicity was evaluated in vitro by monitoring peptide-specific T-cell responses. Additionally, the immunomodulatory properties of these peptides were investigated in vitro by exploring their potential of inducing phenotypic maturation and functional differentiation of murine Bone-Marrow derived Dendritic Cells (BM-DCs). It was revealed by our data that all the synthetic peptides predicted for H2 alleles; present the property of immunogenicity. Among the synthetic peptides which contained T-cell epitopes, the peptide 52-68 aa (LieIF_2) exhibited immunomodulatory properties with the larger potential. LieIF_2-pulsed BM-DCs up-regulated the expression of the co-stimulatory surface molecules CD80 and CD86, as well as the production of the proinflammatory cytokine TNF-α and of the Th1-polarizing cytokines IL-12 and IFN-γ. The aforementioned data suggest that selected parts of LieIF could be used to develop innovative subunit protective vaccines able to induce effective immunity mediated by MHC class I-restricted as well as class II-restricted T-cell responses.

Valproic Acid and Lithium Meditate Anti-Inflammatory Effects by Differentially Modulating Dendritic Cell Differentiation and Function

Valproic acid (VPA), with inhibition activity mainly toward histone deacetylase (HDAC) and Glycogen Synthase Kinase (GSK)-3, and lithium, with inhibition activity mainly toward GSK-3, are both prescribed in clinical as mood-stabilizers and anticonvulsants for the control of bipolar disorder. This study aims to compare the immuno-modulation activities of VPA and lithium, especially on the differentiation and functions of dendritic cells (DC). Our data show that treatment with VPA or lithium effectively alleviated the severity of collagen-induced arthritis triggered by LPS in mice. Both agents reduced the serum level of IL-6 and IL-10 after LPS challenge in mice. VPA and lithium both induce significant down-regulation of group I CD1 expression and secretion of IL-6 during differentiation of human monocyte-derived immature DC, while they differ in the induction of CD83 and CD86 expression, secretion of IL-8, IL-10, and TNF-α. Upon stimulation of immature DC with LPS, VPA, and lithium both reduced the secretion of IL-6 and TNF-α. However, only lithium significantly increased the production of IL-10, while VPA increased the production of IL-8 but substantially reduce the secretion of IL-10 and IL-23. Treatment with VPA resulted in a reduced capacity of LPS-stimulated DC to promote the differentiation of T helper 17 cells that are critical in the promotion of inflammatory responses. Taken together, our results suggest that VPA and lithium may differentially modulate inflammation through regulating the capacity of DC to mediate distinct T cell responses, and they may provide a complementary immunomodulatory effects for the treatment of inflammation-related diseases. J. Cell. Physiol. 232: 1176-1186, 2017. © 2016 Wiley Periodicals, Inc.

Reduction of facial wrinkles by hydrolyzed water-soluble egg membrane associated with reduction of free radical stress and support of matrix production by dermal fibroblasts

Objective

The aim of this study was to evaluate the effects of water-soluble egg membrane (WSEM) on wrinkle reduction in a clinical pilot study and to elucidate specific mechanisms of action using primary human immune and dermal cell-based bioassays.

Methods

To evaluate the effects of topical application of WSEM (8%) on human skin, an open-label 8-week study was performed involving 20 healthy females between the age of 45 years and 65 years. High-resolution photography and digital analysis were used to evaluate the wrinkle depth in the facial skin areas beside the eye (crow’s feet). WSEM was tested for total antioxidant capacity and effects on the formation of reactive oxygen species by human polymorphonuclear cells. Human keratinocytes (HaCaT cells) were used for quantitative polymerase chain reaction analysis of the antioxidant response element genes Nqo1, Gclm, Gclc, and Hmox1. Evaluation of effects on human primary dermal fibroblasts in vitro included cellular viability and production of the matrix components collagen and elastin.

Results

Topical use of a WSEM-containing facial cream for 8 weeks resulted in a significant reduction of wrinkle depth (P<0.05). WSEM contained antioxidants and reduced the formation of reactive oxygen species by inflammatory cells in vitro. Despite lack of a quantifiable effect on Nrf2, WSEM induced the gene expression of downstream Nqo1, Gclm, Gclc, and Hmox1 in human keratinocytes. Human dermal fibroblasts treated with WSEM produced more collagen and elastin than untreated cells or cells treated with dbcAMP control. The increase in collagen production was statistically significant (P<0.05).

Conclusion

The topical use of WSEM on facial skin significantly reduced the wrinkle depth. The underlying mechanisms of this effect may be related to protection from free radical damage at the cellular level and induction of several antioxidant response elements, combined with stimulation of human dermal fibroblasts to secrete high levels of matrix components.

Functionally aberrant dendritic cell subsets and expression of DC-SIGN differentiate acute from chronic HBV infection

BACKGROUND

Dendritic cells (DCs) promote pathogen recognition, uptake and presentation of antigen through DC-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) and toll-like receptors (TLRs).

AIMS AND OBJECTIVES

We aimed to study temporal changes in DCs, TLRs and DC-SIGN during acute viral hepatitis B (AVHB) infection and compare them to chronic (CHB) and to investigate the earliest time point of activated pathogen recognition receptors in hepatitis B viral infection.

METHODS

We measured the frequencies of circulating myeloid (mDC) and plasmacytoid (pDC) dendritic cells and IFN-α production along with the expression of DC-SIGN and Toll Like Receptors (TLR's) in HBV patients at different time points. Also investigated in healthy volunteers, the dynamic changes in TLRs expression after receiving hepatitis B vaccine.

RESULTS

On follow-up of AVHB patients, we found the mDC population was significantly higher at week 4 and 6 (p < 0.02, 0.01), whereas the pDC population was unchanged at week 6 compared with week 0. Whereas frequencies of mDCs and pDCs were found to be elevated in AVHB and CHB patients than HC (p < 0.00 and 0.01, respectively) but was comparable among AVHB vs CHB. The DCs in CHB patients were functionally impaired with significantly low IFN-α production and low DCSIGN expression (p < 0.04 and 0.00, respectively). Even after stimulation by TLR agonists, no change was found in IFN-α production in CHB patients. MyD88 and IL-6, IFN-α mRNA levels were also found down-regulated. Interestingly, on follow-up after HBV vaccine, TLRs expression was found high at day 3 after vaccination.

DISCUSSION

The initial events of immune activation might be responsible for modulating immune response. These novel observations would pave the way for the development of antiviral strategies for chronic HBV infection.

Haptoglobin protein and mRNA expression in psoriasis and its clinical significance

The present study aimed to explore the association between haptoglobin protein and mRNA expression and psoriasis. A total of 138 patients with psoriasis that were undergoing therapy at Linyi People's Hospital (Linyi, China) between January 2011 and January 2015 were enrolled in the present study. The mRNA expression levels of haptoglobin were detected by in situ hybridization; immunohistochemistry was used to detect haptoglobin protein expression; and double‑labeling immunofluorescence was used to count Langerhans cells; western blotting was also conducted to determine protein expression. A receiver operating characteristic (ROC) curve was generated to assess the diagnostic value of haptoglobin for psoriasis. Compared with the normal and negative control (NC) groups, the mRNA expression levels of haptoglobin were markedly increased in the experimental group (P<0.05). Haptoglobin protein expression was also markedly increased in the experimental group compared with in the normal and NC groups (P<0.05). Conversely, there was no significant difference in haptoglobin expression between the NC group and the normal group (P>0.05). The critical value of haptoglobin mRNA in the diagnosis of psoriasis was 2.93, and sensitivity and specificity were 91.3 and 73.6%, respectively. The area under the ROC curve was 0.883 [95% confidence interval (CI)=0.837‑0.929]. The critical value of haptoglobin protein in the diagnosis of psoriasis was 0.995, and sensitivity and specificity were 76.1 and 99.9%, respectively. The area under the ROC curve was 0.926 (95% CI=0.837‑0.929). The present study demonstrated that the mRNA and protein expression levels of haptoglobin were increased in patients with psoriasis. Haptoglobin mRNA and protein expression were closely associated with the occurrence of psoriasis; therefore, haptoglobin may be considered a promising novel clinical indicator for the diagnosis of psoriasis.

Synthetic antimicrobial and LPS-neutralising peptides suppress inflammatory and immune responses in skin cells and promote keratinocyte migration

The stagnation in the development of new antibiotics and the concomitant high increase of resistant bacteria emphasize the urgent need for new therapeutic options. Antimicrobial peptides are promising agents for the treatment of bacterial infections and recent studies indicate that Pep19-2.5, a synthetic anti-lipopolysaccharide (LPS) peptide (SALP), efficiently neutralises pathogenicity factors of Gram-negative (LPS) and Gram-positive (lipoprotein/-peptide, LP) bacteria and protects against sepsis. Here, we investigated the potential of Pep19-2.5 and the structurally related compound Pep19-4LF for their therapeutic application in bacterial skin infections. SALPs inhibited LP-induced phosphorylation of NF-κB p65 and p38 MAPK and reduced cytokine release and gene expression in primary human keratinocytes and dermal fibroblasts. In LPS-stimulated human monocyte-derived dendritic cells and Langerhans-like cells, the peptides blocked IL-6 secretion, downregulated expression of maturation markers and inhibited dendritic cell migration. Both SALPs showed a low cytotoxicity in all investigated cell types. Furthermore, SALPs markedly promoted cell migration via EGFR transactivation and ERK1/2 phosphorylation and accelerated artificial wound closure in keratinocytes. Peptide-induced keratinocyte migration was mediated by purinergic receptors and metalloproteases. In contrast, SALPs did not affect proliferation of keratinocytes. Conclusively, our data suggest a novel therapeutic target for the treatment of patients with acute and chronic skin infections.

The impact of langerin (CD207)+ dendritic cells and FOXP3+ Treg cells in the small bowel mucosa of children with celiac disease and atopic dermatitis in comparison to children with functional gastrointestinal disorders

In the present study we aimed to evaluate the impact of langerin (CD207)+ dendritic cells (DCs) and FOXP3+ Treg cells in the intestinal mucosa of children with celiac disease (CD) and atopic dermatitis (AD) in comparison to children with functional gastrointestinal disorders (FGD). Seventy-five children (37 male, mean age 8.4 ± 4.8 years), who randomly underwent small bowel biopsy, were studied. The CD was diagnosed in 14 children, including five persons with concomitant AD (all positive for anti-tissue transglutaminase IgA antibodies and with small bowel atrophy). Normal small bowel mucosa was found in eight patients with AD and in 53 patients with FGD. The sera of all patients were tested for total and specific IgE antibodies to food allergen panels. Staining for CD11c+, langerin (CD207+) DCs, CD4+, and FOXP3+ Treg cells was performed on paraffin-embedded sections of bioptates using immunohistochemistry. The density of CD11c+ DCs, CD4+, and FOXP3+ Treg cells was higher in the CD patients compared to the AD and FGD patients (p = 0.02; p = 0.001). In AD, significantly higher density of CD11c+ DCs was detected in patients positive for specific IgE to food allergen panels (p = 0.02). The FGD patients with elevated total IgE had increased density of langerin (CD207)+ DCs compared to the patients with normal total IgE levels (p = 0.01). The increased density of FOXP3+ Treg cells, CD4+, cells and CD11c+ DCs was associated with CD but not with AD. The elevated level of total IgE or specific IgE to food allergens was associated with more pronounced expression of DCs, indicating a possible link between the presence of these cells in small bowel mucosa with elevated level of serum IgE.

State-of-the-art of regulatory dendritic cells in cancer

Dendritic cells (DCs) with robust immunosuppressive activity are commonly found in the microenvironment of advanced solid tumors. These innate immune cells are generically termed regulatory DCs and include various subsets such as plasmacytoid, conventional and monocyte-derived/inflammatory populations whose normal function is subverted by tumor-derived signals. This review summarizes recent findings on the nature and function of regulatory DCs, their relationship with other myeloid subsets and unique therapeutic opportunities to abrogate malignant progression through their targeting.

Decidual soluble factors, through modulation of dendritic cells functions, determine the immune response patterns at the feto-maternal interface

Dendritic cells (DCs) can acquire immunogenic or tolerogenic properties depending on intrinsic and tissue environmental factors. We aimed to determine the immunomodulatory effects of decidual soluble factors from abortion- and non-abortion-prone mice on DC functions. The decidual cell supernatants (DS) were obtained from abortion-prone and non-abortion-prone mice. Splenic DCs were treated with DS and conalbumin (as an antigen) and injected into the palms of the mice. After five days, regional lymph node cells were collected and cultured in the presence and absence of conalbumin. The proliferation of lymphocyte cells, the frequency of regulatory T cells (Tregs), and the production of IL-4 and IFN-γ were measured by [(3)H]thymidine incorporation, flow cytometry, and ELISA respectively. Our results indicated that DS from both abortion- and non-abortion-prone mice decreased the ability of DCs to induce lymphocyte proliferation and IFN-γ production, while enhanced their capacity to induce Tregs compared with non-treated DCs. Another important finding was that the immunosuppressive effects of DS from abortion-prone mice on DCs for inducing proliferative responses, developing Tregs, and producing IFN-γ by primed lymphocytes was less than DS from non-abortion-prone mice. We also found that only DS from non-abortion-prone mice could enhance the capacity of DCs to induce IL-4 production by primed lymphocytes. It can be concluded that decidua-secreted factors, by altering DC functions, can determine the pattern of immune responses at the fetomaternal interface and, subsequently, pregnancy outcome.

Immunity to Pathogens Taught by Specialized Human Dendritic Cell Subsets

Dendritic cells (DCs) are specialized antigen-presenting cells (APCs) that have a key role in immune responses because they bridge the innate and adaptive arms of the immune system. They mature upon recognition of pathogens and upregulate MHC molecules and costimulatory receptors to activate antigen-specific CD4⁺ and CD8⁺ T cells. It is now well established that DCs are not a homogeneous population but are composed of different subsets with specialized functions in immune responses to specific pathogens. Upon viral infections, plasmacytoid DCs (pDCs) rapidly produce large amounts of IFN-α, which has potent antiviral functions and activates several other immune cells. However, pDCs are not particularly potent APCs and induce the tolerogenic cytokine IL-10 in CD4⁺ T cells. In contrast, myeloid DCs (mDCs) are very potent APCs and possess the unique capacity to prime naive T cells and consequently to initiate a primary adaptive immune response. Different subsets of mDCs with specialized functions have been identified. In mice, CD8α⁺ mDCs capture antigenic material from necrotic cells, secrete high levels of IL-12, and prime Th1 and cytotoxic T-cell responses to control intracellular pathogens. Conversely, CD8α⁻ mDCs preferentially prime CD4⁺ T cells and promote Th2 or Th17 differentiation. BDCA-3⁺ mDC2 are the human homologue of CD8α⁺ mDCs, since they share the expression of several key molecules, the capacity to cross-present antigens to CD8⁺ T-cells and to produce IFN-λ. However, although several features of the DC network are conserved between humans and mice, the expression of several toll-like receptors as well as the production of cytokines that regulate T-cell differentiation are different. Intriguingly, recent data suggest specific roles for human DC subsets in immune responses against individual pathogens. The biology of human DC subsets holds the promise to be exploitable in translational medicine, in particular for the development of vaccines against persistent infections or cancer.