BCG infection dose guides dendritic cell migration and T cell priming in the draining lymph node.

In contrast to delayed-type hypersensitivity (DTH) and other hallmark reactions of cell-mediated immunity that correlate with vaccine-mediated protection against Mycobacterium tuberculosis, the contribution of vaccine dose on responses that emerge early after infection in the skin with Bacille Calmette-Guérin (BCG) is not well understood. We used a mouse model of BCG skin infection to study the effect of BCG dose on the relocation of skin Dendritic cells (DCs) to draining lymph node (DLN). Mycobacterium antigen 85B-specific CD4+ P25 T cell-receptor transgenic (P25 TCRTg) cells were used to probe priming to BCG in DLN. DC migration and T cell priming were studied across BCG inocula that varied up to 100-fold (104 to 106 Colony-forming units-CFUs). In line with earlier results in guinea pigs, DTH reaction in our model correlated with BCG dose. Importantly, priming of P25 TCRTg cells in DLN also escalated in a dose-dependent manner, peaking at day 6 after infection. Similar dose-escalation effects were seen for DC migration from infected skin and the accompanying transport of BCG to the DLN. BCG-triggered upregulation of co-stimulatory molecules on migratory DCs was restricted to the first 24 hour after infection and was independent of BCG dose over a 10-fold range (105 to 106 CFUs). The dose seemed to be a determinant of the number of total skin DCs that move to the DLN. In summary, our results support the use of higher BCG doses to detect robust DC migration and T cell priming.

Integrin α5 regulates motility of human monocyte-derived Langerhans cells during immune response.

Langerhans cells (LCs) are mainly present in the epidermis and mucosa, and have important roles during skin infection. Migration of LCs to lymph nodes is essential for antigen presentation. However, due to the difficulties in isolating and culturing human LCs, it is not fully understood how LCs move and interact with the extracellular matrix (ECM) through their adhesion molecules such as integrin, during the immune responses. In this study, we aimed to investigate LC motility, cell shape and the role of integrin under inflammatory conditions using monocyte-derived Langerhans cells (moLCs) as a model. As a result, lipopolysaccharide (LPS) stimulation increased adhesion on fibronectin coated substrate and integrin α5 expression in moLCs. Time-lapse imaging of moLCs revealed that stimulation with LPS elongated cell shape, whilst decreasing their motility. Additionally, this decrease in motility was not observed when pre-treated with a neutralising antibody targeting integrin α5. Together, our data suggested that activation of LCs decreases their motility by promoting integrin α5 expression to enhance their affinity to the fibronectin, which may contribute to their migration during inflammation.

Immunohistochemical analysis of chronic and recurrent dermatophytosis.

BACKGROUND: Dermatophytosis has assumed epidemic proportions with rising resistance, recalcitrance and recurrence, especially in tropical regions. While various factors contribute to high prevalence worldwide, yet little is known about the interactions between host defence mechanisms and dermatophytes, particularly in chronic and recalcitrant dermatophytosis. OBJECTIVES: We aimed to compare the population of various immune cells in specimens of chronic recurrent dermatophytosis and those with acute superficial dermatophytosis. METHODS: We investigated the density of various immune cells-Langerhans cells (CD1a+), macrophages (CD68+), dermal dendrocytes (Factor XIIIa+) in the skin of chronic dermatophytosis patients and those with successfully resolved lesions (controls). RESULTS: Langerhans cells were significantly decreased in the epidermis of patients, both in affected and unaffected areas in comparison with controls. In the dermis, however, no differences in the density of immune cells (macrophages and fibroblasts) were observed. LIMITATIONS: The limited sample size and immune cells evaluated could be expanded further in future research. CONCLUSION: These results indicate that the decreased number of Langerhans cells could be a potential risk factor for the development of chronic and recurrent dermatophytosis.

CD112 Supports Lymphatic Migration of Human Dermal Dendritic Cells.

Dendritic cell (DC) migration from peripheral tissues via afferent lymphatic vessels to draining lymph nodes (dLNs) is important for the organism's immune regulation and immune protection. Several lymphatic endothelial cell (LEC)-expressed adhesion molecules have thus far been found to support transmigration and movement within the lymphatic vasculature. In this study, we investigated the contribution of CD112, an adhesion molecule that we recently found to be highly expressed in murine LECs, to this process. Performing in vitro assays in the murine system, we found that transmigration of bone marrow-derived dendritic cells (BM-DCs) across or adhesion to murine LEC monolayers was reduced when CD112 was absent on LECs, DCs, or both cell types, suggesting the involvement of homophilic CD112-CD112 interactions. While CD112 was highly expressed in murine dermal LECs, CD112 levels were low in endogenous murine dermal DCs and BM-DCs. This might explain why we observed no defect in the in vivo lymphatic migration of adoptively transferred BM-DCs or endogenous DCs from the skin to dLNs. Compared to murine DCs, human monocyte-derived DCs expressed higher CD112 levels, and their migration across human CD112-expressing LECs was significantly reduced upon CD112 blockade. CD112 expression was also readily detected in endogenous human dermal DCs and LECs by flow cytometry and immunofluorescence. Upon incubating human skin punch biopsies in the presence of CD112-blocking antibodies, DC emigration from the tissue into the culture medium was significantly reduced, indicating impaired lymphatic migration. Overall, our data reveal a contribution of CD112 to human DC migration.

Yinxieling decoction ameliorates psoriasis by regulating the differentiation and functions of Langerhans cells via the TGF-ß1/PU.1/IL-23 signal axis.

Langerhans cells (LCs) play a critical role in skin immune responses and the development of psoriasis. Yinxieling (YXL) is a representative Chinese herbal medicine for the treatment of psoriasis in South China. It was found to improve psoriasis without obvious side effects in the clinic. Here we attempted to clarify whether and how YXL regulates the differentiation and functions of LCs in Imiquimod (IMQ)-induced psoriasis in vivo and induced LCs in vitro. The Psoriasis Area Severity Index (PASI) score was used to evaluate the efficacy of YXL for IMQ-induced psoriasis-like mice. Flow cytometry was utilized to analyze the effects of YXL, to regulate the differentiation, migration, maturation, and antigen presentation of LCs. The results show that YXL significantly alleviated skin inflammation, as reduced in PASI score and classic psoriasis characteristics in pathological sections. Although there was no effect on the proportion of total DCs in the skin-draining lymph nodes, the expression of epidermal LCs and its transcription factor PU.1 were both markedly inhibited. LCs were also prevented from migrating from epidermal to skin-draining lymph nodes and mature. In addition, the number of LCs carrying antigens in the epidermis increased, which suggested that YXL could effectively prevent LCs from presenting antigens. In vitro, YXL had a significant impact on inhibiting the differentiation of LCs. Further data showed that YXL decreased the relative expression of transforming growth factor-ß (TGFß) messenger RNA (mRNA) and interleukin-23 (IL-23) mRNAs. Thus, YXL alleviates psoriasis by regulating differentiation, migration, maturation, and antigen presentation via the TGFß/PU.1/IL-23 signal axis.

Epithelial dendritic cells vs. Langerhans cells: Implications for mucosal vaccines.

Next-generation vaccines may be delivered via the skin and mucosa. The stratified squamous epithelium (SSE) represents the outermost layer of the skin (epidermis) and type II mucosa (epithelium). Langerhans cells (LCs) have been considered the sole antigen-presenting cells (APCs) to inhabit the SSE; however, it is now clear that dendritic cells (DCs) are also present. Importantly, there are functional differences in how LCs and DCs take up and process pathogens as well as their ability to activate and polarize T cells, though whether DCs participate in neuroimmune interactions like LCs is yet to be elucidated. A correct definition and functional characterization of APCs in the skin and anogenital tissues are of utmost importance for the design of better vaccines and blocking pathogen transmission. Here, we provide a historical perspective on the evolution of our understanding of the APCs that inhabit the SSE, including a detailed review of the most recent literature.

Relation of Langerhans cell size to buccal carcinoma.

Oral cancer decreases quality of life despite timely medical management. The carcinogens in tobacco products and their role in tumorigenesis are well documented. Langerhans cells (LCs) are a subset of antigen-presenting cells (APCs) that monitor the tumor microenvironment and engulf carcinogens and foreign bodies. We investigated the distribution and size of LCs and their relation to the mode of tobacco consumption and clinical outcome in patients with buccal carcinoma. We recruited patients with oral cancer who were scheduled for tumor excision and men with urethral stricture undergoing substitution urethroplasty using buccal mucosa. Normal and tumor-adjacent tissues were stained with CD1a antibody. The distribution and mean diameter of 100 LCs/patient were determined. We found significantly smaller LCs in patients who chewed only tobacco compared to those who consumed tobacco by other means. The size of LCs decreased significantly with progressive stages of malignant disease. We found that patients with larger LCs survived longer than those with smaller LCs during an average follow-up of 24 months. We suggest a relation between the size of LCs and clinical outcomes in patients with buccal carcinoma.

CD1a and skin T cells: a pathway for therapeutic intervention.

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.

Major Histocompatibility Complex II Expression on Oral Langerhans Cells Differentially Regulates Mucosal CD4 and CD8 T Cells.

In murine periodontitis, the T helper (Th)17 response against Porphyromonas gingivalis in cervical lymph node is abrogated by diphtheria toxin-driven depletion of Langerhans cells (LCs). We determined the impact of major histocompatibility complex class II (MHC-II) presentation in LCs on Th17 cells in the oral mucosa of mice. Using an established human-Langerin promoter-Cre mouse model, we generated LC-specific deletion of the H2-Ab1 (MHC-II) gene. MHC-II expression was ablated in 81.2% of oral-resident LCs compared with >99% of skin-resident LCs. MHC-II (LCΔMHC-II) depletion did not reduce the number of CD4 T cells nor the frequency of Th17 cells compared with that in wild-type mice. However, the frequencies of Th1 cells decreased, and Helios+ T-regulatory cells increased. In ligature-induced periodontitis, the numbers of CD4 T cells and Th17 cells were similar in LCΔMHC-II and wild-type mice. Normal numbers of Th17 cells can therefore be sustained by as little as 18.8% of MHC-II-expressing LCs in oral mucosa. Unexpectedly, oral mucosa CD8 T cells increased >25-fold in LCΔMHC-II mice. Hence, these residual MHC-II-expressing LCs appear unable to suppress the local expansion of CD8 T cells while sufficient to sustain a homeostatic CD4 T-cell response. Reducing the expression of MHC-II on specific LC subpopulations may ultimately boost CD8-mediated intraepithelial surveillance at mucosal surfaces.

Transdermal Microneedles Alleviated Rheumatoid Arthritis by Inducing Immune Tolerance via Skin-Resident Antigen Presenting Cells.

Restoring immune tolerance is the ultimate goal for rheumatoid arthritis (RA) treatment. The most reported oral or intravenous injection routes for the immunization of autoantigens cause gastrointestinal side effects, low patient compliance, and unsatisfied immune tolerance induction. Herein, the use of a transdermal microneedle patch is for the first time investigated to codeliver CII peptide autoantigen and rapamycin for reversing immune disorders of RA. The immunized microneedles efficiently recruit antigen-presenting cells particularly Langerhans cells, and induce tolerogenic dendritic cells at the administration skin site. The tolerogenic dendritic cells further homing to lymph nodes to activate systemic Treg cell differentiation, which upregulates the expression of anti-inflammatory mediators while inhibiting the polarization of Th1/2 and Th17 T cell phenotypes and the expression of inflammatory profiles. As a result, the optimized microneedles nearly completely eliminate RA symptoms and inflammatory infiltrations. Furthermore, it is demonstrated that a low dose of rapamycin is crucial for the successful induction of immune tolerance. The results indicate that a rationally designed microneedle patch is a promising strategy for immune balance restoration with increased immune tolerance induction efficiency and patient compliance.

A Case of Uncommon S100-Negative CD1a-Positive Histiocytosis in a 9-Year-Old Boy: Clinical Presentation, Histopathologic Features, and Successful Treatment Approach.

ABSTRACT: Immunohistochemically, histiocytosis differentiating into Langerhans cells is typically characterized by the expression of CD1a, S100, and varying degrees of Langerin. However, CD1a-positive but S100-negative histiocytosis is extremely rare in clinical practice. We present a case of a 9-year-old boy with multiple erythematous to brown dome-shaped nodules. Histopathologic examination revealed dermal infiltrates of histiocytic cells, exhibiting a distinctive immunohistochemical profile of CD68+, S100-, CD1a+, and Langerin-. This exceptional case may contribute to our understanding of the etiology and differentiation processes of histiocytic proliferative disorders.

Chronic consumption of imbalance diets high in sucrose or fat induces abdominal obesity with different pattern of metabolic disturbances and lost in Langerhans cells population.

AIM: Obesity is a worldwide health issue, associated with development of type 2 Diabetes Mellitus. The aim of this study is to analyze the effect of consumption of two hypercaloric diets on metabolic disturbance and beta cells damage. MAIN METHODS: Male Wistar rats were subjected to twelve months consumption of three diets: a Control balanced diet (CTD, carbohydrates 58 %, proteins 29 %, lipids 13 %) and two hypercaloric diets, high in sucrose (HSD, carbohydrates 68 %, proteins 22 %, lipids 10 %) or high in fat (HFD, carbohydrates 31 %, proteins 14 %, lipids 55 %). Serum levels of glucose, triglycerides and free fatty acids were measured after zoometric parameters determination. Antioxidant enzymes activity and oxidative stress-marker were measured in pancreas tissue among histological analysis of Langerhans islets. KEY FINDINGS: Although diets were hypercaloric, the amount of food consumed by rats decreased, resulting in an equal caloric consumption. The HSD induced hypertriglyceridemia and hyperglycemia with higher levels in free fatty acids (FFA, lipotoxicity); whereas HFD did not increased neither the triglycerides nor FFA, nevertheless the loss of islets' cell was larger. Both diets induced obesity with hyperglycemia and significant reduction in Langerhans islets size. SIGNIFICANCE: Our results demonstrate that consumption of HSD induces more significant metabolic disturbances that HFD, although both generated pancreas damage; as well hypercaloric diet consumption is not indispensable to becoming obese; the chronic consumption of unbalanced diets (rich in carbohydrates or lipids) may lead to abdominal obesity with metabolic and functional disturbances, although the total amount of calories are similar.

Concurrent Langerhans cell histiocytosis and acute myeloid leukemia: A rare presentation of a rare case.

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.

A human 3D immune competent full-thickness skin model mimicking dermal dendritic cell activation.

We have integrated dermal dendritic cell surrogates originally generated from the cell line THP-1 as central mediators of the immune reaction in a human full-thickness skin model. Accordingly, sensitizer treatment of THP-1-derived CD14-, CD11c+ immature dendritic cells (iDCs) resulted in the phosphorylation of p38 MAPK in the presence of 1-chloro-2,4-dinitrobenzene (DNCB) (2.6-fold) as well as in degradation of the inhibitor protein kappa B alpha (IκBα) upon incubation with NiSO4 (1.6-fold). Furthermore, NiSO4 led to an increase in mRNA levels of IL-6 (2.4-fold), TNF-α (2-fold) and of IL-8 (15-fold). These results were confirmed on the protein level, with even stronger effects on cytokine release in the presence of NiSO4: Cytokine secretion was significantly increased for IL-8 (147-fold), IL-6 (11.8-fold) and IL-1ß (28.8-fold). Notably, DNCB treatment revealed an increase for IL-8 (28.6-fold) and IL-1ß (5.6-fold). Importantly, NiSO4 treatment of isolated iDCs as well as of iDCs integrated as dermal dendritic cell surrogates into our full-thickness skin model (SM) induced the upregulation of the adhesion molecule clusters of differentiation (CD)54 (iDCs: 1.2-fold; SM: 1.3-fold) and the co-stimulatory molecule and DC maturation marker CD86 (iDCs ~1.4-fold; SM:~1.5-fold) surface marker expression. Noteworthy, the expression of CD54 and CD86 could be suppressed by dexamethasone treatment on isolated iDCs (CD54: 1.3-fold; CD86: 2.1-fold) as well as on the tissue-integrated iDCs (CD54: 1.4-fold; CD86: 1.6-fold). In conclusion, we were able to integrate THP-1-derived iDCs as functional dermal dendritic cell surrogates allowing the qualitative identification of potential sensitizers on the one hand, and drug candidates that potentially suppress sensitization on the other hand in a 3D human skin model corresponding to the 3R principles ("replace", "reduce" and "refine").

Non-Calcifying/Langerhans Cell-Rich Calcifying Epithelial Odontogenic Tumour: A Critical Review of the Rare and Distinctive Entity.

BACKGROUND: The study aims to analyse the non-calcifying/Langerhans cell rich (NCLC) subtype of calcifying epithelial odontogenic tumour (CEOT).  METHOD: The features of cases of the NCLC subtype of CEOT noted in the English literature by PubMed as well as 3 new cases were reviewed. RESULTS: Overall, twenty-one cases were noted. Many were women in the fourth to sixth decades (male-to-female ratio =1 to 2). Radiologically, the lesion is often unilocular with resorption of the affected teeth. Nineteen of the 21 cases occurred in the maxilla, especially the anterior portion. On pathological examination, epithelial cells are noted in non-calcifying amyloid-rich fibrous stroma. The main differential diagnosis is the amyloid subtype of central odontogenic fibroma. Immunohistochemical studies revealed the tumour epithelial cells were positive for cytokeratins and p63 and contained CD1a, S-100, and langerin-positive Langerhans cells. On a median follow-up of 2 years, one patient had a recurrence one year after curettage. CONCLUSION: The NCLC subtype of CEOT is unique as it contains significant numbers of Langerhans cells and has clinicopathological features distinctive from classic CEOT.

Opsin 3 expression in human Langerhans cell histiocytosis and its mediation of ELD-1 cellular function.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a type of -histiocytic disorder characterized by aberrant function, differentiation or proliferation of mononuclear phagocyte system cells, however, the pathogenesis is not fully understood. Opsin 3 (OPN3) plays an important role in regulating cell function. OBJECTIVES: We aimed to investigate OPN3 expression in LCH and Langerhans cells and evaluate its possible regulation of cellular function in a Langerhans cell-like cell line (ELD-1). MATERIALS & METHODS: Expression of OPN3 in LCH and paired adjacent healthy skin tissue was determined using microscopic tools (immunohistochemical and immunofluorescence staining) and RNA scope. OPN3 protein and mRNA levels in primary dendritic cells and ELD-1 were measured by real-time quantitative PCR and western blotting, respectively. The effects of reduced or over-expressed OPN3 mRNA level, via a lentiviral vector, were examined on ELD-1 proliferation, migration, cell cycle and apoptosis using the Cell Counting Kit 8, EdU-594 kit, Transwell assays and Cell Cycle Analysis Kit and Annexin V-PE apoptosis kit, respectively. Lastly, the signalling pathway mediating these functions was investigated via RNA sequencing and western blotting. RESULTS: OPN3 was highly expressed in human LCH tissue compared to healthy tissue, and was expressed in primary dendritic cells and ELD-1. Knockdown of OPN3 in ELD-1 inhibited cell proliferation, the cell cycle, and cell migration, while over-expression reversed these processes. These functions correlated with induction of the MAPK (p38/JNK/ERK) signalling pathway. CONCLUSION: Our results provide insight into the role of OPN3 in LCH which may become a molecular target for the clinical treatment of LCH.

Langerhans cells shape postnatal oral homeostasis in a mechanical-force-dependent but microbiota and IL17-independent manner.

The postnatal interaction between microbiota and the immune system establishes lifelong homeostasis at mucosal epithelial barriers, however, the barrier-specific physiological activities that drive the equilibrium are hardly known. During weaning, the oral epithelium, which is monitored by Langerhans cells (LC), is challenged by the development of a microbial plaque and the initiation of masticatory forces capable of damaging the epithelium. Here we show that microbial colonization following birth facilitates the differentiation of oral LCs, setting the stage for the weaning period, in which adaptive immunity develops. Despite the presence of the challenging microbial plaque, LCs mainly respond to masticatory mechanical forces, inducing adaptive immunity, to maintain epithelial integrity that is also associated with naturally occurring alveolar bone loss. Mechanistically, masticatory forces induce the migration of LCs to the lymph nodes, and in return, LCs support the development of immunity to maintain epithelial integrity in a microbiota-independent manner. Unlike in adult life, this bone loss is IL-17-independent, suggesting that the establishment of oral mucosal homeostasis after birth and its maintenance in adult life involve distinct mechanisms.

Histiocitosis combinada de tipo Langerhans (Histiocitosis de células de Langerhans y enfermedad de Erdheim-Chester) en varón de 64 años con mutaciones en BRAF y NRAS: a propósito de un caso / Combined histiocytosis of the Langerhans group (Langerhans cell histiocytosis and Erdheim-Chester disease) in a 64-year-old man with BRAF and NRAS mutations: a case report

Paciente varón de 64 años con antecedente de enfermedad de Crohn que en el contexto de un episodio de dolor abdominal agudo es ingresado en el hospital, siendo diagnosticado, tras el estudio histológico de una biopsia cutánea y otra pulmonar, de una histiocitosis combinada encuadrada dentro de las histiocitosis del grupo L (Langerhans). En la biopsia cutánea se evidenció proliferación de células histiocitarias con positividad inmunohistoquímica para Langerina, CD1a, S100, resultando el estudio molecular de la misma positivo para la mutación BRAF p.V600E. En la biopsia pulmonar se evidenció una proliferación de células histiocitarias con positividad inmunohistoquímica para CD68 y para S100 y negatividad para Langerina y CD1a, detectándose en la misma mutaciones en NRAS c.38G>A en el exón 2 (p.G13D).(AU)

We present a case of a 64-year-old male with a history of Crohn's disease who presented with an episode of acute abdominal pain. He was being investigated for a dermatological lesion. A skin and lung biopsy both revealed histiocytosis of the “L” (Langerhans) group. The skin biopsy showed a proliferation of histiocytic cells expressing Langerin, CD1a and S100 and the molecular study was positive for the BRAF p.V600E mutation. In the lung biopsy, a proliferation of histiocytic cells was found, which were positive for CD68 and S100 and negative for Langerin and CD1a; mutations in NRAS c.38G>A in exon 2 (p.G13D) were also detected.(AU)