DC-SIGN promotes allergen uptake and activation of dendritic cells in patients with atopic dermatitis

The dual role of cannabidiol on monocyte-derived dendritic cell differentiation and maturation

Introduction

Extracts and compounds isolated from hemp (Cannabis sativa) are increasingly gaining popularity in the treatment of a number of diseases, with topical formulations for dermatological conditions leading the way. Phytocannabinoids such as ( )-cannabidiol, ( )-cannabinol and ( )-Δ9-tetrahydrocannabivarin (CBD, CBN, and THCV, respectively), are present in variable amounts in the plant, and have been shown to have mostly anti-inflammatory effects both in vitro and in vivo, albeit dominantly in murine models. The role of phytocannabinoids in regulating responses of dendritic cells (DCs) remains unclear.

Methods

Our research aimed to investigate the effects of CBD, CBN, and THCV on human DCs differentiated from monocytes (moDCs). moDCs were treated with up to 10 μM of each phytocannabinoid, and their effects on viability, differentiation, and maturation were assessed both alone, and in conjunction with TLR agonists. The effects of CBD on cytokine production, T cell activation and polarization as well as the transcriptome of moDCs was also determined.

Results

Phytocannabinoids did not influence the viability of moDCs up to 10 μM, and only CBD had effects on maturational markers of moDCs, and neither compound influenced LPS-induced activation at 10 μM. Since only CBD had measurable effects on moDCs, in our subsequent experiments we tested the effect only of that pCB. On moDCs differentiated in the presence of CBD subsequent activation by LPS induced a markedly different, much more tolerogenic response. CBD-treated moDCs also produced significantly more interleukin (IL)-6, TNFα and, importantly, IL-10 in response to LPS, which shows a shift toward anti-inflammatory signaling, as well as a more robust secretory response in general. To rule out the possibility that these effects of CBD are specific to TLR4 signaling, we determined the effect of CBD on TLR7/8-induced maturation as well, and saw similar, although less marked responses. CBD-treated moDCs were also less efficient at activating naïve T cells after LPS stimulation, further supporting the tolerogenic effect of this phytocannabinoid on moDCs. Reactome pathway analysis showed an inflammatory response to LPS in moDCs, and to a lesser extent to CBD as well. In contrast CBD-treated moDCs responded to LPS with a shift towards a more tolerogenic phenotype, as IL-10 signaling was the most prominently induced pathway in this group.

Discussion

Our results show that CBD achieves an anti-inflammatory effect on adaptive immune responses only in the presence of an activating stimuli on moDCs by reprogramming cells during long-term treatment, and not through acute, short-term effects.

Burden of Disease; the Current Status of the Diagnosis and Management of Atopic Dermatitis in China

Atopic dermatitis (AD) is now a global health problem and has been attracting extensive attention from both academic and public society in China. This review aimed to present the current status of the prevalence, disease burden, clinical features, diagnosis, and management of AD in China. The prevalence of AD has been increasing rapidly in China during the past decades, partially due to the increased recognition of the disease; there are still substantial amounts of over-diagnosed eczema and under-diagnosed AD. Chinese dermatologists see many AD patients with atypical manifestation, which poses a challenge to the diagnosis. The Chinese diagnostic criteria for adults and pediatric patients with AD have been proposed respectively and validated with high sensitivity and specificity. International and Chinese guidelines for management of AD have been popularized; however, there are still many practices that need verification through randomized case-control study. Dupilumab and JAK inhibitors have demonstrated favorable efficacy for AD patients in China, and a multidimensional approach is needed for selection of the patients and evaluation of the efficacy and safety. Patient education and long-term management for AD are just beginning in China, and need to be strengthened in the future.

C-Type Lectin Receptor Mediated Modulation of T2 Immune Responses to Allergens

PURPOSE OF REVIEW

Allergic diseases represent a major health problem of increasing prevalence worldwide. In allergy, dendritic cells (DCs) contribute to both the pathophysiology and the induction of healthy immune responses to the allergens. Different studies have reported that some common allergens contain glycans in their structure. C-type lectin receptors (CLRs) expressed by DCs recognize carbohydrate structures and are crucial in allergen uptake, presentation, and polarization of T cell responses. This review summarizes the recent literature regarding the role of CLRs in the regulation of type 2 immune responses to allergens.

RECENT FINDINGS

In this review, we highlight the capacity of CLRs to recognize carbohydrates in common allergens triggering different signaling pathways involved in the polarization of CD4⁺ T cells towards specific Th2 responses. Under certain conditions, specific CLRs could also promote tolerogenic responses to allergens, which might well be exploited to develop novel therapeutic approaches of allergen-specific immunotherapy (AIT), the single treatment with potential disease-modifying capacity for allergic disease. At this regard, polymerized allergens conjugated to non-oxidized mannan (allergoid-mannan conjugated) are next-generation vaccines targeting DCs via CLRs that promote regulatory T cells, thus favoring allergen tolerance both in preclinical models and clinical trials. A better understanding of the role of CLRs in the development of allergy and in the induction of allergen tolerance might well pave the way for the design of novel strategies for allergic diseases.

Identification, expression patterns, evolutionary characteristics and recombinant protein activities analysis of CD209 gene from Megalobrama amblycephala

CD209 is a type II transmembrane protein in the C-type lectin family, which is involved in the regulation of innate and adaptive immune system. Although it has been widely studied in mammals, but little has been reported about fish CD209 genes. In the present study, Megalobrama amblycephala CD209 (MaCD209) gene was cloned and characterized, its expression patterns, evolutionary characteristics, agglutinative and bacteriostatic activities were analyzed. These results showed that the open reading frame (ORF) of MaCD209 gene was 795 bp, encoding 264 aa, and the calculated molecular weight of the encoded protein was 29.7 kDa. MaCD209 was predicted to contain 2 N-glycosylation sites, 1 functional domain (C-LECT-DC-SIGN-like) and 1 transmembrane domain. Multiple sequence alignment showed that the amino acid sequence of MaCD209 was highly homologous with that of partial fishes, especially the highly conserved C-LECT-DC-SIGN-like domain and functional sites of CD209. Phylogenetic analysis showed that the CD209 genes from M. amblycephala and other cypriniformes fishes were clustered into one group, which was reliable and could be used for evolutionary analysis. Then, adaptive evolutionary analysis of teleost CD209 was conducted, and several positively selected sites were identified using site and branch-site models. Quantitative real-time PCR analysis showed that MaCD209 gene was highly expressed in the liver and heart. Moreover, the expression of MaCD209 was significantly induced upon Aeromonas hydrophila infection, with the peak levels at 4 h or 12 h post infection. The immunohistochemical analysis also revealed increased distribution of MaCD209 protein post bacterial infection. In addition, recombinant MaCD209 (rMaCD209) protein was prepared using a pET32a expression system, which showed excellent bacterial binding and agglutinative activities in a Ca²⁺-independent manner. However, rMaCD209 could only inhibit the proliferation of Escherichia coli rather than A. hydrophila. In conclusion, this study identified the MaCD209 gene, detected its expression and evolutionary characteristics, and evaluated the biological activities of rMaCD209 protein, which would provide a theoretical basis for understanding the evolution and functions of fish CD209 genes.

Current Advances in Structure-Function Relationships and Dose-Dependent Effects of Human Milk Oligosaccharides

HMOs (human milk oligosaccharides) are the third most important nutrient in breast milk. As complex glycans, HMOs play an important role in regulating neonatal intestinal immunity, resisting viral and bacterial infections, displaying anti-inflammatory characteristics, and promoting brain development. Although there have been some previous reports of HMOs, a detailed literature review summarizing the structure-activity relationships and dose-dependent effects of HMOs is lacking. Hence, after introducing the structures and synthetic pathways of HMOs, this review summarizes and categorizes identified structure-function relationships of HMOs. Differential mechanisms of different structural HMOs utilization by microorganisms are summarized. This review also emphasizes the recent advances in the interactions between different health benefits and the variance of dosage effect based on in vitro cell tests, animal experiments, and human intervention studies. The potential relationships between the chemical structure, the dosage selection, and the physiological properties of HMOs as functional foods are vital for further understanding of HMOs and their future applications.

miR-155: An Important Role in Inflammation Response

MicroRNAs (miRNAs) are a class of small, mature, noncoding RNA that lead to posttranscriptional gene silencing to regulate gene expression. miRNAs are instrumental in biological processes such as cell development, cell differentiation, cell proliferation, and cell apoptosis. The miRNA-mediated gene silencing is an important part of the regulation of gene expression in many kinds of diseases. miR-155, one of the best-characterized miRNAs, has been found to be closely related to physiological and pathological processes. What is more, miR-155 can be used as a potential therapeutic target for inflammatory diseases. We analyze the articles about miR-155 for nearly five years, review the advanced study on the function of miR-155 in different inflammatory cells like T cells, B cells, DCs, and macrophages, and then summarize the biological functions of miR-155 in different inflammatory cells. The widespread involvement of miR-155 in human diseases has led to a novel therapeutic approach between Chinese and Western medicine.

Differential uptake of three clinically relevant allergens by human plasmacytoid dendritic cells

Background

Human plasmacytoid dendritic cells (pDC) have a dual role as interferon-producing and antigen-presenting cells. Their relevance for allergic diseases is controversial. and the impact of pDC on allergic immune responses is poorly understood.

Methods

This in vitro study on human pDC isolated from peripheral blood was designed to compare side by side the uptake of three clinically relevant representative allergens: fluorochrome-labeled house dust mite Der p 1, Bee venom extract from Apis mellifera (Api) and the food allergen OVA analyzed flow cytometry and confocal microscopy.

Results

We found that the internalization and its regulation by TLR9 ligation was significantly different between allergens in terms of time course and strength of uptake. Api and OVA uptake in pDC of healthy subjects was faster and reached higher levels than Der p 1 uptake. CpG ODN 2006 suppressed OVA uptake and to a lesser extent Der p 1, while Api internalization was not affected. All allergens colocalized with LAMP1 and EEA1, with Api being internalized particularly fast and reaching highest intracellular levels in pDC. Of note, we could not determine any specific differences in antigen uptake in allergic compared with healthy subjects.

Conclusions

To our knowledge this is the first study that directly compares uptake regulation of clinically relevant inhalative, injective and food allergens in pDC. Our findings may help to explain differences in the onset and severity of allergic reactions as well as in the efficiency of AIT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12948-021-00163-8.

Carbohydrates in allergy: from disease to novel immunotherapies

Respiratory allergic disorders are a global public health problem that are responsible for substantial morbidity and healthcare expenditure. Despite the availability of allergen immunotherapy (AIT), its efficacy is suboptimal and regimens are lengthy, with a significant risk of potentially severe side effects. Studies on the recognition of allergens by immune cells through carbohydrate-lectin interactions, which play a crucial role in immune modulation and pathogenesis of allergy, have paved the way for improvements in AIT. We highlight innovative approaches for more effective and safer AIT, including the use of allergens conjugated to specific carbohydrates that bind to C-type lectins (CLRs) and sialic acid-binding immunoglobulin-type lectins (Siglecs) on immune cells to induce suppressive responses.

Characterization of Innate Immune Responses to House Dust Mite Allergens: Pitfalls and Limitations

Whereas house dust mite (HDM) allergy results from a dysregulated Th2-biased adaptive immune response, activation of innate immune signaling pathways is a critical prerequisite for the initiation of HDM sensitizations. Such innate sensing is mainly controlled by the airway epithelium and the skin. The resulting release of epithelial-derived proinflammatory cytokines and innate alarmins such as GM-CSF, IL-25, IL-33 and TSLP mediates the activation of ILC2 cells and cDCs to promote Th2-biased inflammation. Significant progress in the elucidation of HDM innate immune activation has been made in the past decade and highlighted key roles of the LPS/TLR4 axis, chitin-dependent pathways together with HDM protease allergens. However, the precise mechanisms by which HDM allergens are sensed by the innate immune system remain largely unknown. Such investigations are made difficult for several reasons. Among these are (1) the natural association of HDM allergens with immunostimulators from the mite exoskeleton as well as from environmental microorganisms/pollutants or endosymbiotic bacteria; (2) the purification of individual HDM allergens from extracts in sufficient amounts and devoid of any microbial and protein impurities; (3) the production of correctly folded recombinant HDM allergens which could display the same biological activity than their natural counterparts; (4) the accessibility to human epithelial samples with cellular heterogeneities and inter-donor variations; (5) the translation of experimental data from mouse models to humans is almost missing. The goal of the present mini-review is to emphasize some important limitations and pitfalls in the elucidation of innate immunostimulatory properties of HDM allergens.

Thymic Stromal Lymphopoietin Is Implicated in the Pathogenesis of Bullous Pemphigoid by Dendritic Cells

Objectives

Both thymic stromal lymphopoietin (TSLP) and dendritic cells (DCs) are involved in many autoimmune diseases, but the potential roles of TSLP and DCs in bullous pemphigoid (BP) have not been clarified. We sought to explore the contributions of TSLP and DCs in patients with BP.

Methods

TSLP levels in sera and blister fluids were measured by enzyme-linked immunosorbent assay. The TSLP expression in the BP lesional skin was detected by immunohistochemical staining. Infiltration of DCs, marked by DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), and its relationship with TSLP and TSLP receptors was evaluated by immunofluorescence staining.

Results

We found that TSLP levels in sera and in blister fluids of patients with BP were higher compared to the control groups. In patients with BP, TSLP levels in sera correlated with TSLP levels in blisters. The expression of TSLP in the BP lesional skin was higher compared to the healthy controls' skin. Greater numbers of TSLP-positive cells were observed in the epidermis of patients with BP compared to the healthy controls. Greater numbers of DC-SIGN-positive cells were present in the BP lesional skin compared to the skin of controls. The expression of TSLP was highly upregulated in DC-SIGN-positive cells, and most DC-SIGN-positive cells expressed TSLP receptors.

Conclusions

We conclude that TSLP may activate DC-SIGN-positive DCs directly, which may be involved in the pathogenesis of BP.

Immunomodulation by Human Milk Oligosaccharides: The Potential Role in Prevention of Allergic Diseases

The prevalence and incidence of allergic diseases is rising and these diseases have become the most common chronic diseases during childhood in Westernized countries. Early life forms a critical window predisposing for health or disease. Therefore, this can also be a window of opportunity for allergy prevention. Postnatally the gut needs to mature, and the microbiome is built which further drives the training of infant's immune system. Immunomodulatory components in breastmilk protect the infant in this crucial period by; providing nutrients that contain substrates for the microbiome, supporting intestinal barrier function, protecting against pathogenic infections, enhancing immune development and facilitating immune tolerance. The presence of a diverse human milk oligosaccharide (HMOS) mixture, containing several types of functional groups, points to engagement in several mechanisms related to immune and microbiome maturation in the infant's gastrointestinal tract. In recent years, several pathways impacted by HMOS have been elucidated, including their capacity to; fortify the microbiome composition, enhance production of short chain fatty acids, bind directly to pathogens and interact directly with the intestinal epithelium and immune cells. The exact mechanisms underlying the immune protective effects have not been fully elucidated yet. We hypothesize that HMOS may be involved in and can be utilized to provide protection from developing allergic diseases at a young age. In this review, we highlight several pathways involved in the immunomodulatory effects of HMOS and the potential role in prevention of allergic diseases. Recent studies have proposed possible mechanisms through which HMOS may contribute, either directly or indirectly, via microbiome modification, to induce oral tolerance. Future research should focus on the identification of specific pathways by which individual HMOS structures exert protective actions and thereby contribute to the capacity of the authentic HMOS mixture in early life allergy prevention.

Langerhans cells mediate the skin-induced tolerance to ovalbumin via Langerin in a murine model

BACKGROUND

Epicutaneous sensitization is an important route of immunization for allergens in atopic diseases; however, studies have also shown that application with protein on the intact skin induces antigen-specific tolerance. Langerhans cells (LCs) play an immunosuppressive role in several inflammatory skin diseases and mouse models, and the role of LCs in the skin-induced tolerance is not fully understood.

METHODS

Langerin-DTA mice that were deficient in LCs were utilized to produce the model of skin-induced tolerance to ovalbumin (OVA). Binding of Langerin to OVA was analyzed by enzyme-linked immunosorbent assay, flow cytometry, and immunofluorescence. Homozygous Langerin-DTR mice that were deficient in Langerin were introduced to assess the role of Langerin in the skin-induced tolerance.

RESULTS

Application with OVA onto the intact, but not tape-stripped, skin attenuated the production of OVA-specific IgE, IgG1, and IgG2a induced by subsequent subcutaneous immunization with OVA, and the inhibitory effects were abolished in Langerin-DTA mice. In contrast to the tape-stripped skin, the intact skin induced the production of IL-10 by LCs in draining lymph node after application with OVA. Langerin could bind OVA, and homozygous Langerin-DTR mice demonstrated similar humoral and cellular immune responses in the model of skin-induced tolerance compared to wide-type mice.

CONCLUSION

Our data suggested that LCs were critical in the intact skin-induced tolerance to protein antigen via Langerin, and LCs might be targeted via Langerin to regulate the immune responses in systemic and (or) skin inflammatory diseases.

Glyco-Dendrimers as Intradermal Anti-Tumor Vaccine Targeting Multiple Skin DC Subsets

The human skin is an attractive anti-tumor vaccination site due to the vast network of dendritic cell (DC) subsets that carry antigens to the draining lymph nodes and stimulate tumor specific CD4⁺ and CD8⁺ T cells in. Specific vaccine delivery to skin DC can be accomplished by targeting glycan coated antigens to C-type lectin receptors (CLRs) such as DC-SIGN expressed by human dermal DCs and Langerin expressed by Langerhans cells (LCs), which facilitate endocytosis and processing for antigen presentation and T cell activation. Although there are multiple human skin DC subsets, targeting individual DC subsets and receptors has been a focus in the past. However, the simultaneous targeting of multiple human skin DC subsets that mobilize the majority of the skin antigen presenting cells (APC) is preferred to accomplish more robust and efficient T cell stimulation. Dual CLR targeting using a single tumor vaccine has been difficult, as we previously showed Langerin to favor binding and uptake of monovalent glyco-peptides whereas DC-SIGN favors binding of larger multivalent glyco-particles such as glyco-liposomes. Methods: We used branched polyamidoamine (PAMAM) dendrimers as scaffold for melanoma specific gp100 synthetic long peptides and the common DC-SIGN and Langerin ligand Lewis Y (Le^Y), to create multivalent glyco-dendrimers with varying molecular weights for investigating dual DC-SIGN and Langerin targeting. Using DC-SIGN⁺ monocyte derived DC (moDC) and Langerin⁺ primary LC we investigated glyco-dendrimer CLR targeting properties and subsequent gp100 specific CD8⁺ T cell activation in vitro. In situ targeting ability to human dermal DC and LC through intradermal injection in a human skin explant model was elucidated. Results: Dual DC-SIGN and Langerin binding was achieved using glyco-dendrimers of approximately 100kD, thereby fulfilling our criteria to simultaneously target LCs and CD1a⁺ and CD14⁺ dermal DC in situ. Both DC-SIGN and Langerin targeting by glyco-dendrimers resulted in enhanced internalization and gp100 specific CD8⁺ T cell activation. Conclusion: We designed the first glyco-vaccine with dual CLR targeting properties, thereby reaching multiple human skin DC subsets in situ for improved anti-tumor CD8⁺ T cell responses.

Myeloid C-type lectin receptors in skin/mucoepithelial diseases and tumors

Myeloid C‐type lectin receptors (CLRs), which consist of an extracellular carbohydrate recognition domain and intracellular signal transducing motif such as the immunoreceptor tyrosine‐based activation motif (ITAM) or immunoreceptor tyrosine‐based inhibitory motif (ITIM), are innate immune receptors primarily expressed on myeloid lineage cells such as dendritic cells (DCs) and Mϕs. CLRs play important roles in host defense against infection by fungi and bacteria by recognizing specific carbohydrate components of these pathogens. However, these immune receptors also make important contributions to immune homeostasis of mucosa and skin in mammals by recognizing components of microbiota, as well as by recognizing self‐components such as alarmins from dead cells and noncanonical non‐carbohydrate ligands. CLR deficiency not only induces hypersensitivity to infection, but also causes dysregulation of muco‐cutaneous immune homeostasis, resulting in the development of allergy, inflammation, autoimmunity, and tumors. In this review, we introduce recent discoveries regarding the roles of myeloid CLRs in the immune system exposed to the environment, and discuss the roles of these lectin receptors in the development of colitis, asthma, psoriasis, atopic dermatitis, and cancer. Although some CLRs are suggested to be involved in the development of these diseases, the function of CLRs and their ligands still largely remain to be elucidated.

The Long Noncoding RNA MALAT1 Induces Tolerogenic Dendritic Cells and Regulatory T Cells via miR155/Dendritic Cell-Specific Intercellular Adhesion Molecule-3 Grabbing Nonintegrin/IL10 Axis

By shaping T cell immunity, tolerogenic dendritic cells (tDCs) play critical roles in the induction of immune tolerance after transplantation. However, the role of long noncoding RNAs (lncRNAs) in the function and immune tolerance of dendritic cells (DCs) is largely unknown. Here, we found that the lncRNA MALAT1 is upregulated in the infiltrating cells of tolerized mice with cardiac allografts and activated DCs. Functionally, MALAT1 overexpression favored a switch in DCs toward a tolerant phenotype. Mechanistically, ectopic MALAT1 promoted dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) expression by functioning as an miR155 sponge, which is essential for the tolerogenic maintenance of DCs and the DC-SIGN-positive subset with more potent tolerogenic ability. The adoptive transfer of MALAT1-overexpressing DCs promoted cardiac allograft survival and protected from the development of experimental autoimmune myocarditis, accompanied with increasing antigen-specific regulatory T cells. Therefore, overexpressed MALAT1 induces tDCs and immune tolerance in heart transplantation and autoimmune disease by the miRNA-155/DC-SIGH/IL10 axis. This study highlights that the lncRNA MALAT1 is a novel tolerance regulator in immunity that has important implications in settings in which tDCs are preferred.