The autoinflammatory disorder, Neonatal-onset Multisystem Inflammatory Disease (NOMID) is the most severe phenotype of disorders caused by mutations in CIAS1 that result in increased production and ...secretion of active IL-1β. NOMID patients present with systemic and organ-specific inflammation of the skin, central nervous system and bone, and respond dramatically to treatment with IL-1 blocking agents. We compared the cellular infiltrates and transcriptome of skin biopsies from patients with NOMID (n = 14) before treatment (lesional (LS) and non-lesional (pre-NL) skin) and after treatment (post-NL) with the IL-1 blocker anakinra (recombinant IL-1 receptor antagonist, Kineret®, Swedish Orphan Biovitrum AB, SOBI), to normal skin (n = 5) to assess tissue responses in the context of untreated and treated disease. Abundant neutrophils distinguish LS skin from pre-NL and post-NL skin. CD11c(+) dermal dendritic cells and CD163(+) macrophages expressed activated caspase-1 and are a likely source of cutaneous IL-1 production. Treatment with anakinra led to the disappearance of neutrophils, but CD3(+) T cells and HLA-DR(+) cells remained elevated. Among the upregulated genes IL-6, IL-8, TNF, IL-17A, CCL20, and the neutrophil defensins DEFA1 and DEFA3 were differentially regulated in LS tissues (compared to normal skin). Important significantly downregulated pathways in LS skin included IL-1R/TLR signaling, type I and II cytokine receptor signaling, mitochondrial dysfunction, and antigen presentation. The differential expression and regulation of microRNAs and pathways involved in post-transcriptional modification were suggestive of epigenetic modification in the chronically inflamed tissue. Overall, the dysregulated genes and pathways suggest extensive "adaptive" mechanisms to control inflammation and maintain tissue homeostasis, likely triggered by chronic IL-1 release in the skin of patients with NOMID.
Introduction
The significant rise in incidence of Hepatitis C virus (HCV) infection among men‐who‐have‐sex‐with‐men (MSM) living with HIV‐1 suggests that HCV under specific circumstances is ...transmitted via sexual contact. During sexual transmission HCV has to cross the epithelial barrier to either directly enter the blood stream or indirectly via mucosal immune cells. However, the mechanisms of sexual transmission of HCV remain unclear. We investigated the role of Langerhans cells (LCs) in HCV susceptibility during sexual contact as LCs are among the first cells in mucosal tissues to encounter invading viruses.
Methods
We investigated the phenotype of primary LCs in anal biopsies from MSM living with HIV‐1. To investigate the role of primary LCs in HCV infection and transmission, we have used both isolated primary skin LCs and the ex vivo tissue transmission model.
Results
Our data identified an important role for mucosal LCs in facilitating HCV transmission after HIV‐1 exposure or immune activation. LCs were detected within mucosal anal tissues obtained from HIV‐1 positive MSM biopsies. In order to perform functional studies, we used primary LCs from skin, which have a similar phenotype as mucosal LCs. Immature LCs were neither infected nor transmitted HCV to hepatocytes. Notably, exposure to HIV‐1 significantly increased HCV transmission by LCs in the ex vivo transmission model. HIV‐1 replication was crucial for the increased HCV transmission as HIV‐1 inhibitors significantly reduced HIV‐1‐induced HCV transmission. Moreover, tissue immune activation of LCs also increased HCV transmission to target cells.
Conclusions
Thus, our data strongly indicate that HIV‐1 or immune activation in MSM leads to capture of HCV by mucosal LCs, which might facilitate transmission to other cells or allow entry of HCV into the blood. This novel transmission mechanism by LCs also implicates that the activation state of LCs is an important cellular determinant for HCV susceptibility after sexual contact.
New method to develop a human skin‐equivalent containing LC‐like cells in vitro, under conditions that mimic the natural tissue composition.
In this report, the construction of a functional, ...immunocompetent, full‐thickness skin equivalent (SE) is described, consisting of an epidermal compartment containing keratinocytes, melanocytes, and human LCs derived from the MUTZ‐3 cell line (MUTZ‐LC) and a fibroblast‐populated dermal compartment. The CD1a+Langerin+HLA‐DR+ MUTZ‐LCs populate the entire epidermis at a similar density to that found in native skin. Exposure of the SE to subtoxic concentrations of the allergens NiSO4 and resorcinol resulted in LC migration out of the epidermis toward the fibroblast‐populated dermal compartment. A significant dose‐dependent up‐regulation of the DC maturation‐related CCR7 and IL‐1β transcripts and of CD83 at the protein level upon epidermal exposure to both allergens was observed, indicative of maturation and migration of the epidermally incorporated LC. We have thus successfully developed a reproducible and functional full‐thickness SE model containing epidermal MUTZ‐LC. This model offers an alternative to animal testing for identifying potential chemical sensitizers and for skin‐based vaccination strategies and provides a unique research tool to study human LC biology in situ under controlled in vitro conditions.
To increase (tumor) vaccine efficacy, there is an urgent need for phenotypic and functional characterization of human dendritic cell (DC) subsets residing in lymphoid tissues. In this study we ...identified and functionally tested 4 human conventional DC (cDC) subsets within skin-draining sentinel lymph nodes (SLNs) from early-stage melanoma patients. These SLNs were all tumor negative and were removed on average 44 days after excision of the primary melanoma. As such, they were considered representative of steady-state conditions. On comparison with skin-migrated cDC, 2 CD1a+ subsets were identified as most likely skin-derived CD11cint Langerhans cells (LC) with intracellular langerin and E-cadherin expression or as CD11chi dermal DCs with variable expression of langerin. Two other CD1a− LN-residing cDC subsets were characterized as CD14−BDCA3hiCD103− and CD14+BDCA3loCD103+, respectively. Whereas the CD1a+ skin-derived subsets displayed greater levels of phenotypic maturation, they were associated with lower levels of inflammatory cytokine release and were inferior in terms of allogeneic T-cell priming and IFNγ induction. Thus, despite their higher maturation state, skin-derived cDCs (and LCs in particular) proved inferior T-cell activators compared with the CD1a− cDC subsets residing in melanoma-draining LNs. These observations should be considered in the design of DC-targeting immunotherapies.
Langerhans cells (LCs) are classically viewed as unique antigen-presenting cells (APCs) that originate from embryonic precursors and maintain themselves independently in the epidermis. However, ...recent studies have demonstrated that murine LCs in mucosal epithelia arise and are continuously replenished from circulating bone marrow (BM) precursors. This has led to the emergence of a novel perspective proposing that LCs can evolve from various origins. Because both embryonic and BM precursors differentiate into LCs only after entering the epithelium, this highlights its crucial role in nurturing LC development to perfectly comply with the physiological functions of the tissue. Thus, current evidence suggests plasticity of LC differentiation, revealing novel developmental mechanisms that are controlled by environmental cues.
Whereas mouse skin LCs originate from embryonic macrophages and fetal liver monocytes, mucosal LCs arise from adult bone marrow precursors – pre-dendritic cells and monocytes.
Despite their distinct ontogeny, mouse mucosal and skin LCs share a similar anatomic location, phenotype, transcriptomic signature, and function, which highlights the plasticity of the mononuclear phagocytic system. Indeed, under some conditions skin LCs can also develop from bone marrow precursors.
The epithelium holds the cues to instruct LC differentiation. Nevertheless, the mouse epithelium of the skin and the various mucosae (e.g., oral, vaginal, and corneal mucosa), can fine-tune LC differentiation to adjust their phenotype and frequencies to the physiological function and architecture of the tissue.
Differentiation of mouse mucosal LCs, unlike skin LCs, can be controlled by the microbiota via regulation of epithelial differentiation signals.
Summary
Background
Psoriasis is a common skin condition driven by increased expression of interleukin (IL)‐17. Langerhans cells (LCs) are epidermal dendritic cells that regulate cutaneous immune ...responses. Within the uninvolved skin of patients with psoriasis, LCs display impaired migration from the epidermis.
Objectives
To investigate the role of keratinocytes (KCs) in the regulation of LC function and the response of KCs to IL‐17.
Methods
KCs were cultured from the uninvolved skin of patients with psoriasis and healthy individuals with or without IL‐17 treatment and the conditioned medium examined for its ability to alter LC function in an ex vivo human skin explant model. Furthermore, we examined the effect of IL‐17 on LC mobilization in psoriasis by neutralizing IL‐17 in the same skin explant model.
Results
Conditioned medium from psoriasis KCs inhibited LC migration in healthy skin. Moreover, conditioned medium from healthy KCs treated with IL‐17 also inhibited healthy LC migration. Finally, neutralizing IL‐17 in psoriasis skin resulted in enhanced LC migration.
Conclusions
Collectively, these data suggest that an altered KC secretome, driven by increased expression of IL‐17, is responsible for impaired LC migration in the uninvolved skin of patients with psoriasis.
What's already known about this topic?
Langerhans cells (LCs) are the dendritic cells of the epidermis and regulate the cutaneous immune response.
LC migration is impaired in the uninvolved skin of patients with early‐onset chronic plaque psoriasis.
Interleukin (IL)‐17 is a cytokine that is involved in the pathogenesis of psoriasis.
We have recently shown that IL‐17 inhibits LC migration in a healthy human ex vivo epidermal explant model.
What does this study add?
Conditioned media generated from psoriasis, but not healthy, keratinocytes (KCs), inhibits LC migration.
Conditioned media generated from healthy KCs treated with IL‐17 also inhibits LC migration.
This suggests that KCs, in response to increased expression of IL‐17, are responsible for secreting a factor that alters LC function.
In an ex vivo psoriasis explant model addition of neutralizing anti‐IL‐17 antibody restores LC migration.
What is the translational message?
This study provides further evidence that IL‐17 is a key cytokine driving the epidermal changes in psoriasis and is thus an attractive target for therapy.
The inhibitory factor produced by KCs under IL‐17 control, once identified, is also a potential druggable target.
Linked Comment: Kirby. Br J Dermatol 2018; 178:1240.
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Langerhans cell histiocytosis (LCH) is a potentially fatal condition characterized by granulomatous lesions with characteristic clonal mononuclear phagocytes (MNPs) harboring activating somatic ...mutations in mitogen-activated protein kinase (MAPK) pathway genes, most notably BRAF
. We recently discovered that the BRAF
mutation can also affect multipotent hematopoietic progenitor cells (HPCs) in multisystem LCH disease. How the BRAF
mutation in HPCs leads to LCH is not known. Here we show that enforced expression of the BRAF
mutation in early mouse and human multipotent HPCs induced a senescence program that led to HPC growth arrest, apoptosis resistance and a senescence-associated secretory phenotype (SASP). SASP, in turn, promoted HPC skewing toward the MNP lineage, leading to the accumulation of senescent MNPs in tissue and the formation of LCH lesions. Accordingly, elimination of senescent cells using INK-ATTAC transgenic mice, as well as pharmacologic blockade of SASP, improved LCH disease in mice. These results identify senescent cells as a new target for the treatment of LCH.
In recent years, transdermal protein delivery has emerged as a promising approach for immunization purposes. This study presents a novel system for transdermal delivery of diphtheria-tetanus vaccine ...using an electrothermal-activated interface. The technology involves applying layers of a solution containing the vaccine and a polymer on top of Kapton heaters, which are remotely connected to a computer that measures the temperature of the skin and adjusts the heat output accordingly to avoid hyperthermia. In vivo experiments were conducted on mice to compare the immune responses induced by electrothermal delivery with intraperitoneal injection and with passive transfer through micro-needling. Our results demonstrate that the antibody produced by the electrothermal method is more efficient than transdermal immunization by micro-needling. The level of immune response shows a dose dependence on immunogen and heating time. Despite the higher efficiency of intraperitoneal injection, electrothermal delivery offers remarkable benefits such as long-lasting immunogen matrix and low-cost immunogen administration. Although our study provides important insights into the potential of the electrothermal transdermal vaccination as a safe and effective alternative to traditional needle-based immunization methods, further research is needed to evaluate the level of immunization induced by this method against the actual induction of the disease and to optimize the efficiency of antibody production.
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Background: Chronic alcoholics experience increased incidence and severity of infections, the mechanism of which is incompletely understood. Dendritic cells (DC) migrate from peripheral locations to ...lymph nodes (LN) to initiate adaptive immunity against infection. Little is known about how chronic alcohol exposure affects skin DC numbers or migration.
Methods: Mice received 20% EtOH in the drinking water for up to 35 weeks. Baseline Langerhans cell (LC) and dermal DC (dDC) numbers were enumerated by immunofluorescence (IF). LC repopulation after inflammation was determined following congenic bone marrow (BM) transplant and ultraviolet (UV) irradiation. Net LC loss from epidermis was determined by IF following TNF‐α or CpG stimulation. LC and dDC migration into LN was assessed by flow cytometry following epicutaneous FITC administration.
Results: Chronic EtOH consumption caused a baseline reduction in LC but not dDC numbers. The deficit was not corrected following transplantation with non‐EtOH‐exposed BM and UV irradiation, supporting the hypothesis that the defect is intrinsic to the skin environment rather than LC precursors. Net loss of LC from epidermis following inflammation was greatly reduced in EtOH‐fed mice versus controls. Ethanol consumption for at least 4 weeks led to delayed LC migration into LN, and consumption for at least 8 weeks led to delayed dDC migration into LN following epicutaneous FITC application.
Conclusions: Chronic EtOH consumption causes decreased density of epidermal LC, which likely results in decreased epidermal immunosurveillance. It also results in altered migratory responsiveness and delayed LC and dDC migration into LN, which likely delays activation of adaptive immunity. Decreased LC density at baseline appears to be the result of an alteration in the skin environment rather than an intrinsic LC defect. These findings provide novel mechanisms to at least partially explain why chronic alcoholics are more susceptible to infections, especially those following skin penetration.
High-risk human papillomaviruses (HPVs) are sexually transmitted viruses causally associated with several cancers. During its natural life cycle, HPV16, the most common high-risk genotype, infects ...the epithelial basal cells in a process facilitated through a recently identified receptor, the annexin A2 heterotetramer (A2t). During infection, HPV16 also interacts with Langerhans cells (LC), the APC of the epithelium, inducing immune suppression, which is mediated by the HPV16 L2 minor capsid protein. Despite the importance of these virus-immune cell interactions, the specific mechanisms of HPV16 entry into LC and HPV16-induced immune suppression remain undefined. An N-terminal peptide of HPV16 L2 (aa 108-126) has been shown to specifically interact with A2t. In this study, we show that incubation of human LC with this peptide blocks binding of HPV16. Inhibiting this interaction with an A2t ligand or by small interfering RNA downregulation of A2t significantly decreases HPV16 internalization into LC in an L2-dependent manner. A2t is associated with suppression of LC maturation as demonstrated through attenuated secretion of Th1-associated cytokines and decreased surface expression of MHC class II on LC exposed to A2t. Conversely, small molecule inhibition of A2t prevents HPV16-induced suppression of LC immune function as indicated by significantly increased secretion of inflammatory cytokines and surface expression of CD86 in HPV16 treated LC pre-exposed to A2t inhibitors. These results demonstrate that HPV16 suppresses LC maturation through an interaction with A2t, revealing a novel role for this protein.
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