Search

Current evidence suggests that ontogeny may account for the functional heterogeneity of some tissue macrophages, but not others. Here, we asked whether developmental origin drives different functions of skin Langerhans cells (LCs), an embryo-derived mononuclear phagocyte with features of both tissue macrophages and dendritic cells. Using time-course analyses, bone marrow chimeras, and fate tracing models, we found that the complete elimination of embryo-derived LCs at steady state results in their repopulation from circulating monocytes. However, monocyte-derived LCs inefficiently replenished the epidermal niche. Instead, these cells preferentially migrated to skin-draining lymph nodes. Mechanistically, we show that the enhanced migratory capability of monocyte-derived LCs is associated with higher expression of CD207/Langerin, a C-type lectin involved in the capture of skin microbes. Our data demonstrate that ontogeny plays a role in the migratory behavior of epidermal LCs.

Air pollution is an exogenous stressor known to have a detrimental impact on skin health through the induction of inflammation; however, the direct effect of topical pollution exposure is still being elucidated. Human skin equivalents (HSE) aim to reproduce in vitro the structure and function of the native skin tissue. However, HSEs typically lack skin‐resident immune cells, which could play a key role in the inflammatory response induced by pollution exposure. We outline the development of a HSE‐containing MUTZ‐3‐derived Langerhans cells (MUTZ‐3‐LCs), which show dendritic morphology and Langerhans cell marker expression. We demonstrated that HSE‐containing MUTZ‐3‐LC have lower basal levels of proinflammatory cytokines, but topical stimulation with allergens and irritant compounds induced a greater inflammatory response in these models compared to HSE without immune cells. To study the effect of pollution, we created a technique to apply diesel particulate matter (DPM) to HSEs. Though our microscopic analysis demonstrated that DPM does not penetrate the stratum corneum, we showed that DPM did induce production of proinflammatory cytokines, but notably only in HSEs containing MUTZ‐3‐LCs. These data suggest that topical exposure to air pollution can induce cutaneous inflammation and that skin‐resident immune cells contribute to this response. This highlights the significance of immune‐competent HSEs to the study of exogenous stressors in vitro. [ABSTRACT FROM AUTHOR]

In the past decades studies investigating the dendritic cell (DC) activation have been conducted almost exclusively in animal models. However, due to species-specific differences in the DC subsets, there is an urgent need for alternative in vitro models allowing the investigation of Langerhans cell (LC) and dermal dendritic cell (DDC) activation in human tissue. We have engineered a full-thickness (FT) human skin tissue equivalent with incorporated LC surrogates derived from the human myeloid leukemia-derived cell line Mutz-3, and DDC surrogates generated from the human leukemia monocytic cell line THP-1. Topical treatment of the skin models encompassing Mutz-LCs only with nickel sulfate (NiSO4) or 1-chloro-2,4-dinitrobenzene (DNCB) for 24 h resulted in significant higher numbers of CD1a positive cells in the dermal compartment, suggesting a sensitizer-induced migration of LCs. Remarkably, exposure of the skin models encompassing both, LC and DDC surrogates, revealed an early sensitizer-induced response reflected by increased numbers of CD1a positive cells in the epidermis and dermis after 8 h of treatment. Our human skin tissue equivalent encompassing incorporated LC and DDC surrogates allows the investigation of DC activation, subsequent sensitizer identification and drug discovery according to the principles of 3R. [ABSTRACT FROM AUTHOR]

Background: Langerhans cell histiocytosis (LCH) is a rare malignant disorder of epidermal antigen presenting cells. It is characterized by infiltration of various tissues with dendritic cells (Langerhans cells, LC) that express CD1a or CD207 (langerin), often leading to organ dysfunction. A patient with LCH required liver transplantation (LT) for LCH‐associated biliary‐tract disease. Cholangiopathy developed after LT. The question arose: In this patient, did LC in damaged liver‐allograft biliary epithelium signify acute cellular rejection (ACR) or recurrent LCH? Methods: We evaluated immunohistochemical identification of LC (CD1a, CD207) in the proposita and in 14 ACR patient samples as distinguishing between ACR and recurrent LCH. Results: Among 15 patient samples, 3 (20%) marked with neither antibody. Among the remaining 12 samples (80%), 4 (26.7%)—including that from the proposita—had cells marking for both antigens within bile‐duct epithelium as well as in surrounding portal‐tract connective tissue, 2 (13.3%) had cells marking for both antigens in one region or the other, but not in both, and 6 (40%) had cells marking for only one antigen in one region or the other. Conclusions: Immunostaining for CD1a and CD207/langerin in the setting of ACR without suspicion of LCH identifies LC in damaged bile ducts. This biomarker pairing proved not to be LCH‐specific. Our findings indicate that the presence of these cells alone is insufficient to identify recurrent LCH in the allograft liver. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) irradiation of the skin causes mutations that can promote the development of melanoma and nonmelanoma skin cancer. High‐dose UVB exposure triggers a vigorous skin reaction characterized by inflammation resulting in acute sunburn. This response includes the formation of sunburn cells and keratinocytes (KC) undergoing programmed cell death (apoptosis) when repair mechanisms of DNA damage are inadequate. The primary objective of this research was to clarify the involvement of Langerhans cells (LC) in the development of acute sunburn following intense UVB skin irradiation. To address this, we subjected the dorsal skin of mice to a single high‐dose UVB exposure and analyzed the immediate immune response occurring within the skin tissue. Acute sunburn triggered an activation of LC, coinciding with a rapid influx of neutrophils that produced TNF‐α. Furthermore, our investigation unveiled a marked increase in DNA‐damaged KC and the subsequent induction of apoptosis in these cells. Importantly, we demonstrate a crucial link between the inflammatory cascade, the initiation of apoptosis in DNA‐damaged KC, and the presence of LC in the skin. LC were observed to modulate the chemokine response in the skin following exposure to UVB, thereby affecting the trafficking of neutrophils. Skin lacking LC revealed diminished inflammation, contained fewer TNF‐α‐producing neutrophils, and due to the prevention of apoptosis induction, a lingering population of DNA‐damaged KC, presumably carrying the risk of enduring genomic alterations. In summary, our results underscore the pivotal role of LC in preserving the homeostasis of UVB‐irradiated skin. These findings contribute to a deeper understanding of the intricate mechanisms underlying acute sunburn responses and their implications for UV‐induced skin cancer. [ABSTRACT FROM AUTHOR]

Introduction: Leprosy is a leading cause of physical disability due to weakness of muscles and loss of sensation. Due to the difference in immune response in the various forms of leprosy, Langerhans cells (antigen presenting cells) in the skin show a graded number in the various forms of leprosy patients. Materials and methods: a total of 44 cases were considered analysed by categorising according to Ridley and Joplin criteria. Paraffin blocks sections were stained with CD1A antibody using green coloured chromosen. Immuno - histochemistry studies where done using UltraVision LP detection system made by ThermoFisher Scientific. The number of epidermal, dermal and hair follicle Langerhans cells were counted. Result: There was no statistical significance between leprosy types on comparing with the dermal LC score. Whereas Mean value of epidermal LC score was significantly less in lepromatous leprosy (LL) (1.78) and was gradually increasing from borderline lepromatous type (BL) (2.44), borderline tuberculoid type(BT) (5.25) to tuberculoid leprosy (TT) (5.50). There was a statistically significant difference in number of Langerhan cells between BL and BT and between LL and TT (p=0.000). Conclusion: Progressive reduction in the number of Langerhans cells from tuberculoid subtype to lepromatous subtype was noted. Atrophy, epitheloid cells, giant cells, and nerve changes was seen more in tuberculoid pole than lepromatous pole. There is a statistically difference in the number of Langerhans cells between BL and BT and between LL and LT. [ABSTRACT FROM AUTHOR]

Herpes simplex virus (HSV) is sexually transmitted via the anogenital mucosa where it initially infects epidermal keratinocytes and mononuclear phagocytes (MNPs). It then spreads to the dorsal root ganglion via sensory nerve endings, to remain latent for life with periodic reactivation. Currently, there is no cure or vaccine. Initial or recurrent HSV infection can produce serious complications and mediate acquisition of HIV. This review outlines the initial events after the HSV infection of human anogenital mucosa to determine the optimal window to target the virus before it becomes latent. After infection, HSV spreads rapidly within the mid-layers of epidermal keratinocytes in the explanted human inner foreskin. Infected cells produce chemokines, which modulate nectin-1 distribution on the surface of adjacent keratinocytes, facilitating viral spread. Epidermal Langerhans cells and dendritic cells become infected with HSV followed by a "viral relay" to dermal MNPs, which then present viral antigen to T cells in the dermis or lymph nodes. These data indicate the need for interruption of spread within 24 h by diffusible vaccine-induced mediators such as antiviral cytokines from resident immune cells or antibodies. Intradermal/mucosal vaccines would need to target the relevant dermal MNPs to induce HSV-specific CD4+ and CD8+ T cells. [ABSTRACT FROM AUTHOR]

Langerhans cell histiocytosis (LCH) is a heterogeneous histiocytosis characterized by proliferation of Langerhans cells. While less common, manifestations of digestive tract involvement in LCH remain largely unrevealed. We conducted a retrospective analysis of demographics, clinical, endoscopic, genetic and follow-up data from 13 adult patients with pathologically confirmed gastrointestinal involvement of LCH (LCH-GI), in a single-center cohort of 465 patients. Digestive tract involvement was observed in 2.80% of LCH patients. At LCH-GI diagnosis, 7 patients (53.8%) had unifocal lesions, and 6 patients (46.2%) had multisystem disease. 6 patients (46.2%) experienced no gastrointestinal symptoms at LCH-GI onset, while others were symptomatic. Stomach was most commonly affected (61.5%), followed by esophagus (23.1%), colon (7.7%) and anus (7.7%). Endoscopic findings varied among 12 patients, including submucosal bulge (8 patients, 66.7%) and non-bulging lesions (4 patients, 33.3%) such as erosions, coarse granular mucosa, and regional abnormal coloration. Among 8 patients with genetic analysis, BRAFV600E mutation was detected in 5 patients (62.5%). The estimated 1-year overall survival rate was 91.7%. Progression-free survival of patients with submucosal bulges under endoscopy was significantly better than those with non-bulging lesions. This study presents 13 cases of LCH with digestive tract involvement. We emphasize the importance of endoscopy and biopsy for pathological examination of lesions such as submucosal bulges and erosions under endoscopy to assist in early detection of LCH. Comprehensive systemic assessment and regular endoscopic monitoring are essential in patient management. Treatment should be individualized with dynamic adjustments during follow-up. [ABSTRACT FROM AUTHOR]

Allergy is a complex array of diseases influenced by innate and adaptive immunity, genetic polymorphisms, and environmental triggers. Atopic dermatitis is a chronic inflammatory skin disease characterized by barrier defects and immune dysregulation, sometimes leading to asthma and food allergies because of the atopic march. During atopic skin inflammation, Langerhans cells and dendritic cells (DCs) in the skin capture and deliver allergen information to local lymph nodes. DCs are essential immune sensors coordinating immune reactions by capturing and presenting antigens to T cells. In the context of allergic responses, DCs play a crucial role in instructing two types of helper T cells—type 2 helper T (Th2) cells and follicular helper T (TFH) cells—in allergic responses and IgE antibody responses. In skin sensitization, the differentiation and function of Th2 cells and TFH cells are influenced by skin-derived factors, including epithelial cytokines, chemokines, and signalling pathways to modify the function of migratory DCs and conventional DCs. In this review, we aim to understand the specific mechanisms involving DCs in allergic responses to provide insights into the pathogenesis of allergic diseases and potential therapeutic strategies. [ABSTRACT FROM AUTHOR]

Background Sex hormone changes during menopausal transition contribute to declining skin health. However, how menopause and its treatment by hormone replacement therapy (HRT) impact the skin barrier and immune system is unclear. Objectives To examine how menopause and HRT affect the skin barrier and immune cell composition in postmenopausal women following irritant challenge. Methods Two cohorts of postmenopausal women were recruited to the study. The first cohort consisted of 10 untreated women [HRT–; mean (SEM) age 56.5 (1.6) years (range 48–63)] and the second was composed of 8 women receiving HRT [HRT+; mean (SEM) age 54.0 (2.1) years (range 48–63)]. Skin irritation was induced by applying topical sodium lauryl sulfate (SLS) 1.25% to occluded buttock skin for 48 h. Clinical assessment was conducted after 24 h, followed by biopsy of both SLS-challenged and unchallenged skin for analysis of skin barrier proteins and immune cell distribution using immunofluorescence. Results Clinically, there were no significant differences in skin irritant responses between those taking or not taking HRT (including increased skin redness and blood flow). In response to SLS challenge a significant increase in transepidermal water loss (P < 0.05), filaggrin deposition and cytokeratin 10 (K10)+ cell layers (P < 0.01) was observed in individuals receiving HRT compared with the HRT– group. Following SLS challenge in individuals taking HRT, a significant (P < 0.01) reduction in CD207+ cells in the epidermis was observed, accompanied by an increase of CD207+ cells in the dermis, indicative of migrating Langerhans cells (LCs). Significantly fewer migrating LCs were found in those who were not receiving HRT (P < 0.01). Furthermore, the numbers of dermal dendritic cells (DCs), macrophages, and CD11c+CD206– and CD68+CD206– subsets were found to be significantly (P < 0.05) higher in those taking HRT following SLS challenge. Conclusions Individuals receiving HRT displayed enhanced skin barrier response to SLS challenge with thicker filaggrin and increased K10+ epidermal cell layers. Following challenge, HRT users exhibited elevated LC, inflammatory DC and macrophage counts in the dermis. These may render skin both more prone to inflammation and more capable of resolving it, while also promoting skin repair. [ABSTRACT FROM AUTHOR]

Due to its capacity to drive osteoclast differentiation, the receptor activator of nuclear factor kappa-β ligand (RANKL) is believed to exert a pathological influence in periodontitis. However, RANKL was initially identified as an activator of dendritic cells (DCs), expressed by T cells, and exhibits diverse effects on the immune system. Hence, it is probable that RANKL, acting as a bridge between the bone and immune systems, plays a more intricate role in periodontitis. Using ligature-induced periodontitis (LIP), rapid alveolar bone loss was detected that was later halted even though the ligature was still present. This late phase of LIP was also linked with immunosuppressive conditions in the gingiva. Further investigation revealed that the ligature prompted an immediate migration of RANK-expressing Langerhans cells (LCs) and EpCAM+ DCs, the antigen-presenting cells (APCs) of the gingival epithelium, to the lymph nodes, followed by an expansion of T regulatory (Treg) cells in the gingiva. Subsequently, the ligatured gingiva was repopulated by monocyte-derived RANK-expressing EpCAM+ DCs, while gingival epithelial cells upregulated RANKL expression. Blocking RANKL signaling with monoclonal antibodies significantly reduced the frequencies of Treg cells in the gingiva and prevented gingival immunosuppression. In addition, RANKL signaling facilitated the differentiation of LCs from bone marrow precursors. To further investigate the role of RANKL, we used K14-RANKL mice, in which RANKL is overexpressed by gingival epithelial cells. The elevated RANKL expression shifted the steady-state frequencies of LCs and EpCAM+ DCs within the epithelium, favoring LCs over EpCAM+ DCs. Following ligature placement, heightened levels of Treg cells were observed in the gingiva of K14-RANKL mice, and alveolar bone loss was significantly reduced. These findings suggest that RANKL-RANK interactions between gingival epithelial cells and APCs are crucial for suppressing gingival inflammation, highlighting a protective immunological role for RANKL in periodontitis that was overlooked due to its osteoclastogenic activity. [ABSTRACT FROM AUTHOR]

Circadian rhythms, the internal timekeeping systems governing physiological processes, significantly influence skin health, particularly in response to ultraviolet radiation (UVR). Disruptions in circadian rhythms can exacerbate UVR-induced skin damage and increase the risk of skin aging and cancer. This review explores how circadian rhythms affect various aspects of skin physiology and pathology, with a special focus on DNA repair. Circadian regulation ensures optimal DNA repair following UVR-induced damage, reducing mutation accumulation, and enhancing genomic stability. The circadian control over cell proliferation and apoptosis further contributes to skin regeneration and response to UVR. Oxidative stress management is another critical area where circadian rhythms exert influence. Key circadian genes like brain and muscle ARNT-like 1 (BMAL1) and circadian locomotor output cycles kaput (CLOCK) modulate the activity of antioxidant enzymes and signaling pathways to protect cells from oxidative stress. Circadian rhythms also affect inflammatory and immune responses by modulating the inflammatory response and the activity of Langerhans cells and other immune cells in the skin. In summary, circadian rhythms form a complex defense network that manages UVR-induced damage through the precise regulation of DNA damage repair, cell proliferation, apoptosis, inflammatory response, oxidative stress, and hormonal signaling. Understanding these mechanisms provides insights into developing targeted skin protection and improving skin cancer prevention. [ABSTRACT FROM AUTHOR]

Oral squamous cell carcinoma (OSCC) arises in the oral epithelium, a tissue in which immune surveillance is mediated by its primary resident leukocytes, Langerhans cells (LCs), and γδT cells. Under steady‐state conditions, LCs and γδT cells play a critical role in maintaining oral mucosal homeostasis. As antigen‐presenting cells of stratified epithelia, LCs respond to various challenges faced by the epithelium, orchestrating innate, and adaptive immune responses in order to resolve them. γδT cells also sense diverse epithelial insults and react rapidly through cytokine production and cytolytic activity. These epithelial sentinels are also considered to be the first leukocytes in the oral epithelium to encounter early carcinogenic events that have the potential of becoming OSCC. As evident in many malignancies, leukocyte populations help prevent cancer development although they also promote tumor progression. OSCC is no exception, as studies have reported both anti‐ and pro‐tumor roles of LCs and γδT cells. In this review, we summarize the ontogeny of LCs and γδT cells in the oral epithelium and discuss their role in OSCC. [ABSTRACT FROM AUTHOR]

Objective: Dandruff is characterised by the presence of perivascular leukocytes and mild inflammation; however, the immune microenvironment of dandruff‐affected scalp skin and the potential changes to the hair follicle's (HF) physiological immune privilege (HF IP) remain unknown. Here, we characterised the HF immune microenvironment and immune privilege status in dandruff‐affected scalp skin. Methods: We assessed relevant key parameters in healthy versus dandruff‐affected human scalp biopsies using quantitative immunohistomorphometry, laser capture microdissection, and RNA sequencing. Results: The number of epidermal CD4+ and CD8+ T cells was increased in lesional dandruff scalp skin, while the number of MHC class II+/CD1a+ Langerhans cells was decreased in the infundibulum. The number of intrafollicular and perifollicular CD4+ T cells and CD8+ T cells, perifollicular CD68+ macrophages, and tryptase+ mast cells remained unchanged. Interestingly, MHC class Ia and ß2‐microglobulin protein expression were significantly increased specifically in the suprabulbar outer root sheath (ORS) compartment of dandruff‐associated HFs. RNAseq analysis of laser capture micro‐dissected suprabulbar ORS compartment revealed antigen presentation pathway as the top regulated canonical pathway, along with the upregulation of HF‐IP genes such as HLA‐C, HLA‐DP, and TAP1, which are normally down‐regulated in healthy HFs. Intrafollicular protein expression of known HF IP guardians (CD200 and α‐MSH) and 'danger signals' (MICA and CXCL10) remained unaltered at the IP sites of dandruff lesional HFs compared to non‐lesional and healthy HFs. Instead, the expression of macrophage migration inhibiting factor (MIF), another HF IP guardian, was reduced. Conclusion: Together, this work shows that dandruff is associated with epidermal T‐cell infiltration and a weakened HF IP in the suprabulbar ORS of HFs in dandruff lesional scalp. [ABSTRACT FROM AUTHOR]

Langerhans cells (LCs) are the key antigen‐presenting cells in the epidermis in normal conditions and respond differentially to environmental and/or endogenous stimuli, exerting either proinflammatory or anti‐inflammatory effects. Current knowledge about LCs mainly originates from studies utilizing mouse models, whereas with the development of single‐cell techniques, there has been significant progress for human LCs, which has updated our understanding of the phenotype, ontogeny, differentiation regulation, and function of LCs. In this review, we delineated the progress of human LCs and summarized LCs' function in inflammatory skin diseases, providing new ideas for precise regulation of LC function in the prevention and treatment of skin diseases. [ABSTRACT FROM AUTHOR]

Abstract In the past decades studies investigating the dendritic cell (DC) activation have been conducted almost exclusively in animal models. However, due to species-specific differences in the DC subsets, there is an urgent need for alternative in vitro models allowing the investigation of Langerhans cell (LC) and dermal dendritic cell (DDC) activation in human tissue. We have engineered a full-thickness (FT) human skin tissue equivalent with incorporated LC surrogates derived from the human myeloid leukemia-derived cell line Mutz-3, and DDC surrogates generated from the human leukemia monocytic cell line THP-1. Topical treatment of the skin models encompassing Mutz-LCs only with nickel sulfate (NiSO4) or 1-chloro-2,4-dinitrobenzene (DNCB) for 24 h resulted in significant higher numbers of CD1a positive cells in the dermal compartment, suggesting a sensitizer-induced migration of LCs. Remarkably, exposure of the skin models encompassing both, LC and DDC surrogates, revealed an early sensitizer-induced response reflected by increased numbers of CD1a positive cells in the epidermis and dermis after 8 h of treatment. Our human skin tissue equivalent encompassing incorporated LC and DDC surrogates allows the investigation of DC activation, subsequent sensitizer identification and drug discovery according to the principles of 3R.

AIM: To observe the changes in corneal subepithelial nerve fibers (CNFs) and Langerhans cells (LCs) in patients with type 2 diabetes using corneal laser confocal microscopy (CLCM). METHODS: A total of 60 patients (64 eyes), including 40 patients with type 2 diabetes (DM group) and 20 subjects without diabetes (control group) were included with CLCM. Neuron J plugin of Image J software were used for quantitative analysis of CNF length (CNFL), CNF density (CNFD), corneal nerve branch fiber density (CNBD), main branch length density, branch length density, corneal nerve fiber tortuosity (NT) score, and LCs density. An independent samples t-test to analyze the variability between the two groups was performed, and Pearson correlation analysis was used to analyze the relationships between CNF and multiple biochemical indicators in the DM group. The predictive power of CNF for type 2 diabetes was assessed using the receiver operating characteristic (ROC) curve. RESULTS: There were significant differences in the CNFL, CNFD, and main branch length density between two groups. The results of Pearson correlation analysis showed a significant negative correlation between CNFD and the duration of diabetes as well as triglyceride levels and total cholesterol, and a significant positive correlation between CNFD and serum albumin. In addition, the NT score showed a positive correlation and urea nitrogen, similar to the positive correlation observed between LC density and glycosylated hemoglobin (HbA1c) levels. CNFD showed the highest area under the curve (AUC of ROC) value, followed by main branch length density and CNFL. The AUC of the ROC curve under the logistic regression model also demonstrated good predictive values. The cut-off values of CNFD, CNFL, and main branch length density for diabetes showed 31.25, 18.85, and 12.56, respectively. CONCLUSION: In patients with type 2 diabetes, there is a notable reduction in both CNFL and CNFD. These measurements can be influenced by various blood biochemical factors. However, the compromised nerve fibers can serve as valuable indicators for predicting the onset of type 2 diabetes and also as biomarkers for detecting diabetic neuropathy and its related complications.

Langerhans cell histiocytosis comprises a heterogeneous range of clinical manifestations secondary to clonal proliferation of histiocytes, characterized by the accumulation of these cells in various organs and tissues. The ophthalmological component commonly involved is the orbit. Herein, we report a rare case of Langerhans cell histiocytosis with eyelid involvement, which resulted in severe ocular surface complications, which subsequently significantly impacted the patient’s quality of life. This case report highlights the fact that despite being rare, Langerhans cell histiocytosis should be included in the differential diagnosis of eyelid lesions. Furthermore, a multidisciplinary approach with a systemic overview is crucial for managing the ocular complications. [ABSTRACT FROM AUTHOR]

A calcifying epithelial odontogenic tumor (CEOT) is a rare benign epithelial odontogenic tumor. Histologically, CEOTs are commonly composed of polygonal epithelial cells, eosinophilic amyloid deposits, and calcifications. The non-calcifying/Langerhans cell-rich variant, one of the three variants of CEOTs according to the 2022 World Health Organization classification of head and neck tumors, is rare with few cases reported to date. We present an additional case of a non-calcifying/Langerhans cell-rich CEOT. A 76-year-old woman was referred to our department for painless swelling of the mandibular incisor. Computed tomography showed a 33 × 10 × 18 mm well-defined bone resorption lesion without distention, radiopaque spots, or unerupted teeth in the mandible. Tissue biopsy showed that the tumor was composed of atypical cells with oval nuclei and eosinophilic cytoplasm and many amorphous eosinophilic amyloid-like deposits, which led to the diagnosis of CEOT. Marginal mandibulectomy was performed under general anesthesia from the right mandibular first premolar to the left mandibular canine. The tumor was composed of small nests and strands of odontogenic epithelial cells and many amorphous eosinophilic amyloid-like deposits; however, there was no area of calcification in any tissue section. Immunohistochemical examination showed that the tumor epithelial cells were positive for S-100 protein. Based on these histopathological and immunohistochemical findings, the tumor was diagnosed as a non-calcifying/Langerhans cell-rich CEOT. No local recurrence was detected over the 4 years of follow up. [ABSTRACT FROM AUTHOR]

Abstract\nPLAIN LANGUAGE SUMMARYThe occurrence of incidents involving radiation-combined burn injuries (RCBI) poses a significant risk to public health. Understanding the immunological and physiological responses associated with such injuries is crucial for developing care triage to counter the mortality that occurs due to the synergistic effects of radiation and burn injuries. The core focus of this narrative review lies in unraveling the immune response against RCBI. Langerhans cells, mast cells, keratinocytes, and fibroblasts, which induce innate immunity, have been explored for their response to radiation, burns, and combined injuries. In the case of adaptive immune response, exploring behavioral changes in T regulatory (Treg) cells, T helper cells (Th1, Th2, and Th17), and immunoglobulin results in delayed healing compared to burn and radiation injury. The review also includes the function of complement system components such as neutrophils, acute phase proteins (CRP, C3, and C5), and cytokines for their role in RCBI. Combined insults resulting in a reduction in the cell population of immune cells display variation in response based on radiation doses, burn injury types, and their intrinsic radiosensitivity. The lack of approved countermeasures against RCBI poses a significant challenge. Drug repurposing might help to balance immune cell alteration, resulting in fast recovery and decreasing mortality, which gives it clinical significance for its implication on the site of such incidence. However, the exact immune response in RCBI remains insufficiently explored in pre-clinical and clinical stages, which might be due to the non-availability of in vitro models, standard animal models, or human subjects, warranting further research.In the realm of public health, RCBI presents significant risks and obstacles. This hazard is quite serious, and it might get worse in the future as evidenced by incidents like nuclear meltdowns and medical mistakes. Diagnosis and treatment become more challenging when serious injuries, particularly burns, are combined with radiation exposure. Features like early shock, poor wound healing, and hematopoietic instability call for advancements in both diagnosis and therapy. Furthermore, the immune system’s response to RCBI is complicated and involves changes in cytokine concentrations, immune cell activity, and adaptive immune responses compared to single injuries. Immune cell radiosensitivity varies depending on the type of cell, radiation dose, and length of exposure, so it’s important to understand. Repurposing drugs is one of the potential techniques to reduce mortality and speed up healing which are discussed in the manuscript. Still, more research is needed. To effectively tackle RCBI, more investigation into molecular processes, treatment strategy optimization, and information gap closure are essential. [ABSTRACT FROM AUTHOR]

Langerhans cells (LCs) are distinct among phagocytes, functioning both as embryo-derived, tissue-resident macrophages in skin innervation and repair and as migrating professional antigen-presenting cells, a function classically assigned to dendritic cells (DCs). Here, we demonstrate that both intrinsic and extrinsic factors imprint this dual identity. Using ablation of embryo-derived LCs in the murine adult skin and tracking differentiation of incoming monocyte-derived replacements, we found intrinsic intraepidermal heterogeneity. We observed that ontogenically distinct monocytes give rise to LCs. Within the epidermis, Jagged-dependent activation of Notch signaling, likely within the hair follicle niche, provided an initial site of LC commitment before metabolic adaptation and survival of monocyte-derived LCs. In the human skin, embryo-derived LCs in newborns retained transcriptional evidence of their macrophage origin, but this was superseded by DC-like immune modules after postnatal expansion. Thus, adaptation to adult skin niches replicates conditioning of LC at birth, permitting repair of the embryo-derived LC network. Editor's summary: Langerhans cells (LCs) are specialized skin-resident antigen-presenting cells that not only share developmental origins with tissue-resident macrophages but also acquire the dendritic cell–like ability to migrate to draining lymph nodes. How this dual LC identity is imprinted and maintained is not completely understood. Using a mouse model of adult LC repopulation, Appios et al. found that both the developmental origin of repopulating monocytes and epidermal niche signaling imprint LC identity. A subset of infiltrating monocytes underwent stepwise differentiation involving loss of Zeb2-regulated macrophage identity, Jagged/Notch-dependent imprinting of LC fate, and survival signals in the epidermis. Similar developmental programs were detected among human embryo–derived LCs in postnatal skin. Together, these findings identify intrinsic and extrinsic factors guiding LC specification in the skin. —Claire Olingy [ABSTRACT FROM AUTHOR]

The article explores the impact of E‐cadherin deficiency on the dendrite morphology of Langerhans cells (LC) in the epidermis. While E‐cadherin expression is not necessary for LC maintenance in the epidermis or their maturation, it does influence dendrite morphology. E‐Cad deficiency in LC results in fewer upreaching dendrites, reduced CCR7 expression, and diminished antigen uptake after tape stripping, suggesting a role in LC migration and antigen capture. Further research is needed to understand the implications of these findings on percutaneous sensitization and tolerance induction. [Extracted from the article]

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease worldwide. AD is a highly complex disease with different subtypes. Many elements of AD pathophysiology have been described, but if/how they interact with each other or which mechanisms are important in which patients is still unclear. Langerhans cells (LCs) are antigen‐presenting cells (APCs) in the epidermis. Depending on the context, they can act either pro‐ or anti‐inflammatory. Many different studies have investigated LCs in the context of AD and found them to be connected to all major mechanisms of AD pathophysiology. As APCs, LCs recruit other immune cells and shape the immune response, especially adaptive immunity via polarization of T cells. As sentinel cells, LCs are primary sensors of the skin microbiome and are important for the decision of immunity versus tolerance. LCs are also involved with the integrity of the skin barrier by influencing tight junctions. Finally, LCs are important cells in the neuro‐immune crosstalk in the skin. In this review, we provide an overview about the many different roles of LCs in AD. Understanding LCs might bring us closer to a more complete understanding of this highly complex disease. Potentially, modulating LCs might offer new options for targeted therapies for AD patients. [ABSTRACT FROM AUTHOR]

Langerhans cell histiocytosis (LCH) is a rare disorder characterized by the abnormal proliferation of Langerhans cells, a type of immune cell that is normally present in the skin and various other tissues. LCH can affect people of any age but is most commonly diagnosed in children. We report a case of a patient with LCH who developed ipsilateral axillary lymphadenopathology post-COVID-19 vaccination. Lymph node biopsy showed diffuse Langerhans cell hyperplasia which mimicked LCH. Clinically and radiologically, it looked to be a reactive lymph node. The patient was kept on follow up only and after 1 year of follow up the size of lymph nodes regressed confirming to be reactive in nature rather than neoplastic. To the best of our knowledge, this is the second case of Langerhans cell hyperplasia post-COVID-19 vaccination being reported in the literature. [ABSTRACT FROM AUTHOR]

Canine cutaneous histiocytoma (CCH) represents a significant proportion of dog skin tumours, often manifesting as the most common neoplastic skin condition in young animals. Predominantly affecting dogs under four, these tumours appear primarily as solitary lesions that may regress spontaneously. This study, conducted over five years at the University of Trás-os-Montes e Alto Douro, involved a detailed histopathological and ultrastructural examination of 93 CCH cases. Histologically, these tumours showed distinct patterns of lymphoid infiltration, which contributed to their classification into four groups based on the inflammatory response and histological architecture. Most tumours displayed signs of epidermal invasion and frequent mitotic figures, with necrosis present in over half of the cases. Ultrastructurally, the neoplastic cells were characterised by pleomorphism, abundant organelles, and adherens-type junctions. This study offers significant insights into the pathophysiology and morphological characteristics of CCH, underscoring the importance of detailed histological and ultrastructural analysis in accurately diagnosing and understanding this common canine tumour. [ABSTRACT FROM AUTHOR]

Key Clinical Message: A comprehensive diagnostic approach, including immunohistochemistry, is crucial for confirming pulmonary Langerhans cell histiocytosis in adults. Individualized treatment with dynamically adjusted chemotherapy based on therapeutic response leads to significant absorption of lesions and symptom alleviation. Regular follow‐up and timely treatment adjustments according to the patient's condition are essential in managing this rare disease. [ABSTRACT FROM AUTHOR]

Skin is the forestage for a series of many-sided functions of tumor necrosis factor-alpha (TNF-α), a proinflammatory cytokine with staggering versatility and sizable implications for tissue homeostasis, immune responses, angiogenesis, apoptosis, local and systemic inflammation. An aberrant TNF-α-mediated crosstalk has been linked to the pathogenesis of acute and chronic skin inflammatory diseases, and indeed, TNF-α dysregulation can contribute to the development and progression of psoriasis, vitiligo, local damage following exposition to ultraviolet light radiations, cutaneous lupus erythematosus, and acne vulgaris. Therapies that target TNF-α are conspicuously used in the treatment of different skin disorders, aiming to modulate the in vivo immune functions triggered by many cutaneous cells, including keratinocytes, mast cells, or Langerhans cells, and reduce inflammation taking place within the skin. Herein, we focus on the key relationships between TNF-α and distinct skin non-neoplastic inflammatory or physiologic conditions, showing that a natural induction of TNF-α may have a protective significance but that TNF-α overproduction may be harmful or even lethal. Many questions remain unraveled in the therapeutic practice, and caution should be exercised due to eventual backlashes exerted by TNF-α in maintaining skin health or in provoking skin disease. [ABSTRACT FROM AUTHOR]

Background: Pulmonary Langerhans cell histiocytosis (PLCH) is a rare disorder characterized by the proliferation of Langerhans cells along the small airways, which causes nodular and cystic changes in the lung parenchyma. Lung transplantation can be a life-saving option for patients with severe respiratory failure or pulmonary hypertension. Herein, we present a case of successful lung transplantation in a patient with PLCH who developed unusually large thrombi in the central pulmonary artery. Case presentation: A 47-year-old woman with 16-year history of PLCH with rapidly developing respiratory failure was admitted to our hospital for the evaluation of a lung transplant. Enhanced computed tomography revealed large thrombi in dilated central pulmonary arteries. Right heart catheterization revealed severe pulmonary hypertension, with a mean pulmonary artery pressure of 48 mmHg. The thrombi shrank markedly after 3 months of anticoagulation therapy. However, the respiratory status of the patient did not improve. We performed bilateral living-donor lobar lung transplantation with thrombectomy under extracorporeal membrane oxygenation for the remaining thrombi in the main pulmonary arteries. The dilated main pulmonary arteries of the recipient required direct plication for size mismatch. The patient survived in good condition for more than 2 years with no recurrence of thrombosis. Conclusion: Preoperative anticoagulation therapy for massive thrombi in the pulmonary arteries was effective and led to safe lung transplantation. [ABSTRACT FROM AUTHOR]

Background: Langerhans cell histiocytosis (LCH) is a category of poorly understood disorders characterized by the abnormal growth and accumulation of Langerhans cells (LC) and eosinophils in various organs. The exact cause of LCH remains unknown, but it can result from alteration to the immune system, modifications in genetics, or an infectious process. LCH can be present in localized and systemic forms, affecting different organs depending on the patient's age, disease extent, and systemic involvement. Treatment modalities for LCH could be used individually or in combination, such as surgery, chemotherapy, radiotherapy, or even steroid injections. Also, a few reported cases of the localized subtype showed a spontaneous recovery. Objective: We aimed to delineate the diagnostic approach and treatment modalities for cases with Mandibular (LCH) that might have airway compromise. Subjects and methods: A 4-year-old girl, previously healthy, presented to the Emergency Department (ED) with a history of swelling over the mandible for the last 3 weeks. Results: Results: Symptoms started as toothache that was not interfering with eating or limiting her activity. No swelling or change in color over the jaw were observed. Jaw swelling started to appear, increased in size and interfered with eating. She was diagnosed provisionally as dental abscess formation and received other antibiotics for 5 days, but unfortunately her condition was complicated with bleeding from the swelling and drooling of saliva and yellowish discharge as well so visited our ED. She lost one kilogram during this time. LCH was confirmed with transoral tissue biopsy. Conclusion: Mandibular Lngerhans Cell Histocytosis is one of the differential diagnosis of Osteolytic lesions that need diagnostic approaches and modalities of treatment with paying attention to upper airy way involvement. [ABSTRACT FROM AUTHOR]

Background: The regulation of divalent metal transporter-1 (DMT1) by insulin has been previously described in Langerhans cells and significant neuroprotection was found by insulin and insulin-like growth factor 1 treatment during experimental cerebral ischemia in acute ischemic stroke patients and in a rat 6-OHDA model of Parkinson's disease, where DMT1 involvement is described. According to the regulation of DMT1, previously described as a target gene of NF-kB in the early phase of post-ischemic neurodegeneration, both in vitro and in vivo, and because insulin controls the NFkB signaling with protection from ischemic cell death in rat cardiomyocytes, we evaluated the role of insulin in relation to DMT1 expression and function during ischemic neurodegeneration. Methods: Insulin neuroprotection is evaluated in differentiated human neuroblastoma cells, SK-N-SH, and in primary mouse cortical neurons exposed to oxygen glucose deprivation (OGD) for 8 h or 3 h, respectively, with or without 300 nM insulin. The insulin neuroprotection during OGD was evaluated in both cellular models in terms of cell death, and in SK-N-SH for DMT1 protein expression and acute ferrous iron treatment, performed in acidic conditions, known to promote the maximum DMT1 uptake as a proton co-transporter; and the transactivation of 1B/DMT1 mouse promoter, already known to be responsive to NF-kB, was analyzed in primary mouse cortical neurons. Results: Insulin neuroprotection during OGD was concomitant to the down-regulation of both DMT1 protein expression and 1B/DMT1 mouse promoter transactivation. We also showed the insulin-dependent protection from cell death after acute ferrous iron treatment. In conclusion, although preliminary, this evaluation highlights the peculiar role of DMT1 as a possible pharmacological target, involved in neuroprotection by insulin during in vitro neuronal ischemia and acute ferrous iron uptake. [ABSTRACT FROM AUTHOR]

Introduction: Canine cutaneous histiocytoma (CCH) is a benign tumor frequently occurring in young dogs which is derived from Langerhans cells (LC). Distinguishing features of this tumor are its spontaneous regression following a rapid tumor growth. Impaired control of immune checkpoints during tumor development and progression is a widespread phenomenon which may result in an absent or ineffective immune response. The interaction between the inflammatory response and the expression of immune checkpoint molecules is only partially described in this tumor type. The aim of this study was to identify immune checkpoint molecules and molecules from the interferon-mediated immune response that are involved in the regression of CCH. Methods: Forty-eight CCH derived from dogs = 4 years of age were assigned to one of four groups according to the severity and distribution of lymphocyte infiltration. Using immunohistochemistry and whole-slide image scans of consecutive sections the expression of programmed death protein ligand 1 (PDL1), CD80, CD86, Survivin, forkhead box protein 3, Ki-67, cleaved caspase-3, CD3, and mx1 were investigated. RNA in-situ hybridization was performed for transcripts of mx1 and interferon-γ. Results: Neoplastic cells showed an expression of PD-L1, CD80, CD86, and Survivin. The density of CD80 expressing cells was negatively correlated with regression while the density of cleaved caspase-3 positive cells increased with regression. Mx1 transcripts and protein were predominantly localized in neoplastic cells while interferon-γ transcripts were most frequently detected in T-cells. Conclusion: The expression of the immune checkpoint molecules CD86 and PD-L1 and particularly the reduced expression of CD80 in groups 3 and 4 indicate an influence of the investigated immune checkpoints on tumor regression. In parallel an activation of the apoptotic cascade during regression is suggested. Finally, the detection of mx1 within the neoplasm pinpoints to a yet undisclosed role of anti-cellular signaling in tumor immunity. [ABSTRACT FROM AUTHOR]

Primary cilia (PC) are essential signaling hubs for proper epithelial formation and the maintenance of skin homeostasis. Found on most cells in the human body, including skin cells, PC facilitate signal transduction that allows ciliated cells to interact with the immune system via multiple pathways, helping to maintain immune system homeostasis. PC can be altered by various microenvironmental stimuli to develop corresponding regulatory functions. Both PC and ciliary signaling pathways have been shown to be involved in the immune processes of various skin lesions. However, the mechanisms by which PC regulate cellular functions and maintain immune homeostasis in tissues are highly complex, and our understanding of them in the skin remains limited. In this paper, we discuss key ciliary signaling pathways and ciliated cells in the skin, with a focus on their immunomodulatory functions. We have compiled evidence from various cells, tissues and disease models to help explore the potential immunomodulatory effects of PC in the skin and their molecular mechanisms.

The document is a correction notice for a study by Mahmoud et al. on the effects of coriander oil on dexamethasone-induced insulin resistance in rats. The correction addresses mistakes in Figures 7 and 8 of the original publication. The study found that coriander oil may reverse insulin resistance in rats, with no impact on the scientific conclusions. [Extracted from the article]

Langerhans histiocytosis or histiocytosis X is an oligo-clonal proliferation of Langerhans cells. We report the case of an 11-month-old infant who had presented with a parieto-occipital swelling since birth, which progressively increased in volume without any other presenting signs. The radiological work-up initially suspected osteitis of the vault, which was removed in its entirety. The anatomopathological study concluded that it was histiocytosis X. The extension work-up was negative. Follow-up of this patient showed no local recurrence or appearance of other localizations.A review of the literature shows that little is known about its pathophysiology. It mainly affects children and young adults. There are several possible sites of involvement, and cranial vault involvement is a fairly frequent form among the bony sites of this pathology. The diagnosis is confirmed histologically or cytologically, and extension workup is required to confirm the diagnosis. Therapeutic management has not been standardized, and sometimes requires chemotherapy in addition to surgery. The prognosis depends on whether vital organs are affected or not.

The autoimmune disease lupus erythematosus (lupus) is characterized by photosensitivity, where even ambient ultraviolet radiation (UVR) exposure can lead to development of inflammatory skin lesions. We have previously shown that Langerhans cells (LCs) limit keratinocyte apoptosis and photosensitivity via a disintegrin and metalloprotease 17 (ADAM17)-mediated release of epidermal growth factor receptor (EGFR) ligands and that LC ADAM17 sheddase activity is reduced in lupus. Here, we sought to understand how the lupus skin environment contributes to LC ADAM17 dysfunction and, in the process, differentiate between effects on LC ADAM17 sheddase function, LC ADAM17 expression, and LC numbers. We show through transcriptomic analysis a shared IFN-rich environment in non-lesional skin across human lupus and three murine models: MRL/lpr, B6.Sle1yaa, and imiquimod (IMQ) mice. IFN-I inhibits LC ADAM17 sheddase activity in murine and human LCs, and IFNAR blockade in lupus model mice restores LC ADAM17 sheddase activity, all without consistent effects on LC ADAM17 protein expression or LC numbers. Anti-IFNAR- mediated LC ADAM17 sheddase function restoration is associated with reduced photosensitive responses that are dependent on EGFR signaling and LC ADAM17. Reactive oxygen species (ROS) is a known mediator of ADAM17 activity; we show that UVR-induced LC ROS production is reduced in lupus model mice, restored by anti-IFNAR, and is cytoplasmic in origin. Our findings suggest that IFN-I promotes photosensitivity at least in part by inhibiting UVR-induced LC ADAM17 sheddase function and raise the possibility that anifrolumab ameliorates lupus skin disease in part by restoring this function. This work provides insight into IFN-I- mediated disease mechanisms, LC regulation, and a potential mechanism of action for anifrolumab in lupus. [ABSTRACT FROM AUTHOR]

HSV infects keratinocytes in the epidermis of skin via nectin-1. We established a human foreskin explant infection model to investigate HSV entry and spread. HSV1 entry could only be achieved by the topical application of virus via high density microarray projections (HD-MAPs) to the epidermis, which penetrated beyond one third of its thickness, simulating in vivo microtrauma. Rapid lateral spread of HSV1 to a mean of 13 keratinocytes wide occurred after 24 hours and free virus particles were observed between keratinocytes, consistent with an intercellular route of spread. Nectin-1 staining was markedly decreased in foci of infection in the epidermis and in the human keratinocyte HaCaT cell line. Nectin-1 was redistributed, at the protein level, in adjacent uninfected cells surrounding infection, inducible by CCL3, IL-8 (or CXCL8), and possibly CXCL10 and IL-6, thus facilitating spread. These findings provide the first insights into HSV1 entry and spread in human inner foreskin in situ. Author summary: Herpes Simplex Virus (HSV) infects 3.7 billion people globally, leading, in some, to lifelong recurrent disease and co-infection with viruses such as HIV. There is no cure or vaccine. Animal models and in vitro cell lines do not accurately represent the initial events that take place during HSV infection in human genital mucosa. We have successfully established a model of acute HSV-1 infection within explants of human inner foreskin, a common site for sexual transmission. Topical microtrauma penetrating a third of the way into the epidermis was essential for HSV infection, indicating that the two most superficial strata were refractory. There was rapid spread of HSV1 particles through and around epidermal keratinocytes over 24 hours. HSV1 particles also interacted with and were taken up by epidermal Langerhans Cells (LCs) and Dendritic Cells (Epi DCs). Focal HSV1 infection of keratinocytes induced a redistribution of nectin-1, the HSV entry receptor, in a collar surrounding the foci via specific chemokines which further facilitated viral spread. These results provide an insight into the initial events that lead to HSV1 infection and spread within human genital mucosa and defines a time window of opportunity to target the virus before it enters epidermal nerves and becomes latent. [ABSTRACT FROM AUTHOR]

Background: Skin tape‐strips and biopsies are widely used methods for investigating the skin in atopic dermatitis (AD). Biopsies are more commonly used but can cause scarring and pain, whereas tape‐strips are noninvasive but sample less tissue. The study evaluated the performance of skin tape‐strips and biopsies for studying AD. Methods: Whole‐transcriptome RNA‐sequencing was performed on paired tape‐strips and biopsies collected from lesional and non‐lesional skin from AD patients (n = 7) and non‐AD controls (n = 5). RNA yield, mapping efficiency, and differentially expressed genes (DEGs) for the two methods (tape‐strip/biopsy) and presence of AD (AD/non‐AD) were compared. Results: Tape‐strips demonstrated a lower RNA yield (22 vs. 4596 ng) and mapping efficiency to known genes (28% vs. 93%) than biopsies. Gene‐expression profiles of paired tape‐strips and biopsies demonstrated a medium correlation (R2 = 0.431). Tape‐strips and biopsies demonstrated systematic differences in measured expression levels of 6483 genes across both AD and non‐AD samples. Tape‐strips preferentially detected many itch (CCL3/CCL4/OSM) and immune‐response (CXCL8/IL4/IL5/IL22) genes as well as markers of epidermal dendritic cells (CD1a/CD207), while certain cytokines (IL18/IL37), skin‐barrier genes (KRT2/FLG2), and dermal fibroblasts markers (COL1A/COL3A) were preferentially detected by biopsies. Tape‐strips identified more DEGs between AD and non‐AD (3157 DEGs) then biopsies (44 DEGs). Tape‐strips also detected higher levels of bacterial mRNA than biopsies. Conclusions: This study concludes that tape‐strips and biopsies each demonstrate respective advantages for measuring gene‐expression changes in AD. Thus, the specific skin layers and genes of interest should be considered before selecting either method. [ABSTRACT FROM AUTHOR]

Transformation of follicular lymphoma (FL) to a Langerhans cell (LC) neoplasm is extremely uncommon. The shared IGH::BCL2 rearrangement is a robust finding in most transformed tumors underscoring that the cell of origin is perhaps a pre-B cell harboring IGH::BCL2 with the propensity to undergo further genetic alterations in the germinal centers of lymph nodes: does IGH::BCL2 in pre-B cells set off a plasticity cell state? Do FL and LC neoplasms develop separately through a common progenitor or via a multistep process of transdifferentiation or dedifferentiation/redifferentiation? Here, we review the literature and relevant cases presented in the Society for Hematopathology/European Association of Haematopathology 2021 Workshop to better understand this rare and complex phenomenon. We discuss clinical data, clonal relationship, and the mutational profile of these tumors and review proposed mechanisms of B/myeloid conversion based on in vitro and in vivo models. [ABSTRACT FROM AUTHOR]

Psoriasis is a systemic autoimmune/autoinflammatory disease that can be well studied in established mouse models. Skin-resident macrophages are classified into epidermal Langerhans cells and dermal macrophages and are involved in innate immunity, orchestration of adaptive immunity, and maintenance of tissue homeostasis due to their ability to constantly shift their phenotype and adapt to the current microenvironment. Consequently, both macrophage populations play dual roles in psoriasis. In some circumstances, pro-inflammatory activated macrophages and Langerhans cells trigger psoriatic inflammation, while in other cases their anti-inflammatory stimulation results in amelioration of the disease. These features make macrophages interesting candidates for modern therapeutic strategies. Owing to the significant progress in knowledge, our review article summarizes current achievements and indicates future research directions to better understand the function of macrophages in psoriasis. [ABSTRACT FROM AUTHOR]

Dengue virus (DENV) is a continuing global threat that puts half of the world's population at risk for infection. This mosquito-transmitted virus is endemic in over 100 countries. When a mosquito takes a bloodmeal, virus is deposited into the epidermal and dermal layers of human skin, infecting a variety of permissive cells, including keratinocytes, Langerhans cells, macrophages, dermal dendritic cells, fibroblasts, and mast cells. In response to infection, the skin deploys an array of defense mechanisms to inhibit viral replication and prevent dissemination. Antimicrobial peptides, pattern recognition receptors, and cytokines induce a signaling cascade to increase transcription and translation of pro-inflammatory and antiviral genes. Paradoxically, this inflammatory environment recruits skin-resident mononuclear cells that become infected and migrate out of the skin, spreading virus throughout the host. The details of the viral–host interactions in the cutaneous microenvironment remain unclear, partly due to the limited body of research focusing on DENV in human skin. This review will summarize the functional role of human skin, the cutaneous innate immune response to DENV, the contribution of the arthropod vector, and the models used to study DENV interactions in the cutaneous environment. [ABSTRACT FROM AUTHOR]

The CD1 and MR1 protein families present lipid antigens and small molecules to T cells, complementing well-studied major histocompatibility complex–peptide mechanisms. The CD1a subtype is highly and continuously expressed within the skin, most notably on Langerhans cells, and has been demonstrated to present self and foreign lipids to T cells, highlighting its cutaneous sentinel role. Alteration of CD1a-dependent T-cell responses has recently been discovered to contribute to the pathogenesis of several inflammatory skin diseases. In this review, we overview the structure and role of CD1a and outline the current evidence implicating CD1a in the development of psoriasis, atopic dermatitis and allergic contact dermatitis. [ABSTRACT FROM AUTHOR]

Skin is the body's largest organ and serves as a protective barrier from physical, thermal, and mechanical environmental challenges. Alongside, the skin hosts key immune system players, such as the professional antigen-presenting cells (APCs) like the Langerhans cells in the epidermis and circulating macrophages in the blood. Further, the literature supports that the APCs can be activated by antigen or vaccine delivery via multiple routes of administration through the skin. Once activated, the stimulated APCs drain to the associated lymph nodes and gain access to the lymphatic system. This further allows the APCs to engage with the adaptive immune system and activate cellular and humoral immune responses. Thus, vaccine delivery via skin offers advantages such as reliable antigen delivery, superior immunogenicity, and convenient delivery. Several preclinical and clinical studies have demonstrated the significance of vaccine delivery using various routes of administration via skin. However, such vaccines often employ adjuvant/(s), along with the antigen of interest. Adjuvants augment the immune response to a vaccine antigen and improve the therapeutic efficacy. Due to these reasons, adjuvants have been successfully used with infectious disease vaccines, cancer immunotherapy, and immune-mediated diseases. To capture these developments, this review will summarize preclinical and clinical study results of vaccine delivery via skin in the presence of adjuvants. A focused discussion regarding the FDA-approved adjuvants will address the experiences of using such adjuvant-containing vaccines. In addition, the challenges and regulatory concerns with these adjuvants will be discussed. Finally, the review will share the prospects of adjuvant-containing vaccines delivered via skin. [Display omitted] • Role of various routes of vaccine administration via skin. • Skin offers reliable antigen delivery and yields superior immune responses. • Adjuvants as immune response enhancers for infectious disease, cancer vaccines. • Preclinical and clinical studies with FDA-approved adjuvants and cutaneous vaccines. • Regulatory considerations for adjuvanted vaccines delivered via skin. [ABSTRACT FROM AUTHOR]

Simple Summary: Amphibians are classified into three orders with different morphological characteristics: Anura, Apoda, and Caudata. In this article, the importance of skin for amphibians is discussed as it represents a physical, chemical, immunological, and microbiological barrier to pathogen insult is discussed. Langerhans cells (LCs) are antigen-presenting cells constituting an important component of the immune system in the skin. This study aims to characterize Langerhans cells in the skin of Lithobates catesbeianus (Shaw, 1802), Amphiuma means (Garden, 1821), and Typhlonectes natans (Fischer, 1880) with several antibodies previously used to mark the same cells in other vertebrates. The results showed that the distribution of LCs is very similar in the three amphibian species examined, despite their different habitats. In conclusion, the amphibian dendritic cells are morphologically and immunohistochemically homologous to the LCs of all vertebrates so they can be considered as starting points to better understand the phylogeny of the vertebrate immune system. The amphibian taxon includes three orders that present different morphological characteristics: Anura, Caudata, and Apoda. Their skin has a crucial role: it acts as an immune organ constituting a physical, chemical, immunological, and microbiological barrier to pathogen insult and conducts essential physiological processes. Amphibians have developed specialized features to protect the vulnerable skin barrier, including a glandular network beneath the skin surface that can produce antimicrobial and toxic substances, thus contributing to the defense against pathogens and predators. This study aims to characterize Langerhans cells in the skin of Lithobates catesbeianus (order: Anura; Shaw, 1802), Amphiuma means (order: Caudata; Garden, 1821), and Typhlonectes natans (order: Apoda; Fischer, 1880) with the following antibodies: Langerin/CD207 (c-type lectin), Major Histocompatibility Complex (MHC)II, and Toll-like receptor (TLR)2 (expressed by different types of DCs). Our results showed Langerhans cells positive for Langerin CD/207 in the epidermis of the three species; moreover, some antigen-presenting cells (APCs) in the connective tissue expressed TLR2 and MHCII. The distribution of the Langerhans cells is very similar in the three amphibians examined, despite their different habitats. A greater knowledge of the amphibian immune system could be useful to better understand the phylogeny of vertebrates and to safeguard amphibians from population declines. Furthermore, the similarities between amphibians' and human skin concerning immunological features may be useful in both biology and translational medicine. [ABSTRACT FROM AUTHOR]

A 72‐year‐old woman with no significant past medical history was admitted to the hospital for new‐onset of leukocytosis with neutropenia, anemia, and thrombocytopenia, as well as a pruritic skin eruption. She was found to have acute myeloid leukemia (AML) with myelomonocytic differentiation. Her skin eruption consisted of widespread hemorrhagic crusted papules on the scalp and trunk. A skin biopsy was performed, which revealed a proliferation of mononuclear cells in the dermis with prominent epidermotropism and positive expression of CD1a and langerin (CD207), supporting a diagnosis of Langerhans cell histiocytosis (LCH). LCH is an uncommon proliferative disorder of activated Langerhans cells, which generally presents in children. In adults, it is exceptionally infrequent. Associated malignancies and rare reports of AML developing in subsequent years after an initial presentation of LCH have been described. Here we present an unusual concurrent presentation of LCH and AML in an adult. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is an abnormal inflammatory response in the skin to food, environmental IgE, or non-IgE allergens. This disease belongs to a group of inflammatory diseases that affect both children and adults. In highly developed countries, AD is diagnosed twice as often in children than in adults, which may possibly be connected to increased urbanization. The immune system's pathomechanisms of AD involve humoral mechanisms with IgE, cellular T lymphocytes, dendritic cells occurring in the dermis, Langerhans cells occurring in the epidermis, and other cells infiltrating the site of inflammation (eosinophils, macrophages, mast cells, neutrophils, and basophils). Cytokines are small proteins that affect the interaction and communication between cells. This review characterizes cytokines and potential aspects of the treatment of atopic dermatitis, as well as new strategies that are currently being developed, including targeting cytokines and their receptors. [ABSTRACT FROM AUTHOR]

Key Clinical Message A comprehensive diagnostic approach, including immunohistochemistry, is crucial for confirming pulmonary Langerhans cell histiocytosis in adults. Individualized treatment with dynamically adjusted chemotherapy based on therapeutic response leads to significant absorption of lesions and symptom alleviation. Regular follow‐up and timely treatment adjustments according to the patient's condition are essential in managing this rare disease.

Langerhans cell histiocytosis (LCH) is a histiocytic neoplasm characterized by the abnormal proliferation of Langerhans cells. Bone marrow (BM) involvement is associated with high-risk disease and poor survival. Although BM involvement is particularly uncommon, no reported cases of LCH with BM infiltration have been documented in Latin America until now. The aim of this report is to highlight the clinical, hematological, and BM findings of two cases of LCH with BM infiltration, providing insights that may aid in detecting suspected patients. We present two cases of LCH with BM infiltration. One case involved a 23-month-old male patient, and the other a 16-month-old female patient. Common clinical findings in both cases included hepatosplenomegaly and fever. Hematological findings revealed anemia in both cases. The key diagnostic tool was the BM biopsy, which revealed histiocyte nests with characteristic morphology, CD1a-positive cells, increased eosinophils, and reactive paratrabecular lymphocytes. This report underscores the significance of clinical profiles in predicting BM infiltration in LCH. The presence of histiocyte nests displaying the characteristic morphology of Langerhans cells, accompanied by an elevation in eosinophils, indicates bone marrow involvement. Furthermore, the demonstration of CD1a-positive cells through immunohistochemistry serves as a crucial diagnostic tool.