Immunophenotyping challenging tissue types using high-dimensional full spectrum flow cytometry.

Technological advancements in fluorescence flow cytometry and an ever-expanding understanding of the complexity of the immune system, have led to the development of large flow cytometry panels, reaching up to 40 markers at the single-cell level. Full spectrum flow cytometry, that measures the full emission range of all the fluorophores present in the panel instead of only the emission peaks is now routinely used in many laboratories internationally, and the demand for this technology is rapidly increasing. With the capacity to use larger and more complex staining panels, optimized protocols are required for the best panel design, panel validation and high-dimensional data analysis outcomes. In addition, for ex vivo experiments, tissue preparation methods for single-cell analysis should also be optimized to ensure that samples are of the highest quality and are truly representative of tissues in situ. Here we provide optimized step-by-step protocols for full spectrum flow cytometry panel design, tissue digestion and panel optimization to facilitate the analysis of challenging tissue types.

Autonomic nervous system responses in the intermediate band to cranial cutaneous stimulation.

Cardiovascular rhythms representing functional states of the autonomic nervous system (ANS) are insufficiently reflected by the current physiological model based on low and high frequency bands (LF, HF, resp.). An intermediate (IM) frequency band generated by a brainstem pacemaker was included in systemic physiological ANS analyses of forehead skin perfusion (SP), ECG, and respiration. Data of 38 healthy participants at T0 and T1 (+1 week) before, during, and following osteopathic cranial vault hold (CVH) stimulation were analyzed including momentary frequencies of highest amplitude, amplitudes in low (0.05-0.12 Hz), IM (0.12-0.18 Hz), and high (0.18-0.4 Hz) frequency bands, and established heart rate variability (HRV) metrics. During CVH, LF interval durations increased, whereas IM/HF band durations decreased significantly. Amplitudes increased significantly in all frequency bands. A cluster analysis found one response pattern dominated by IM activity (47% of participants) with highly stable 0.08 Hz oscillation to CVH, and one dominated by LF activity (0.10 Hz) at T0, increasing to IM activity at T1. Showing frequency ratios at ≈3:1, respiration was not responsible for oscillations in PPG during CVH. HRV revealed no significant responses. Rhythmic patterns in SP and respiration matched previous findings on a reticular "0.15 Hz rhythm". Involvement of baroreflex pathways is discussed as alternative explanation.

Skin-infiltrating T cells display distinct inflammatory signatures in lichen planus, bullous pemphigoid and pemphigus vulgaris.

Introduction: We here thought to dissect the inflammatory signature in lesions of three skin disorders, which show a common adaptive immune response against autoantigens of the skin but are characterized by diverging clinical phenotypes. Pemphigus vulgaris (PV) and bullous pemphigoid (BP) are type-2-dependent, IgG autoantibody-driven blistering disorders of mucous membranes and skin, which target desmoglein (Dsg)3 and bullous pemphigoid (BP)180, respectively. In contrast, lichen planus (LP) is a common chronic inflammatory disease of the skin and mucous membranes with a pronounced dermal T cell infiltrate. We previously identified peripheral type 1 and 17 T cell responses against Dsg3 and BP180 in a cohort of LP patients strongly suggesting that the underlying inflammatory T cell signature may drive the evolving phenotype. Methods: Paraffin-embedded skin biopsies from well-characterized patients with LP (n=31), BP (n=19), PV (n=9), and pemphigus foliaceus (PF) (n=2) were analysed. Areas with the most prominent inflammatory infiltrate were excised with punch biopsies and tissue microarrays (TMA) containing multiple biopsies were created. Using multicolor immunofluorescence, the inflammatory infiltrate was stained with antibodies against multiple cellular markers, i. e. CD3ϵ, CD4, CD15, TCR-δ, the cytokine IL-17A, and the transcription factors, T-bet and GATA-3. Results: In LP, there was a higher number of CD4+ T cells expressing T-bet compared to GATA-3. In contrast, CD4+ T cells in PV and BP skin lesions more frequently expressed GATA-3 than T-bet. IL-17A+ cells and IL-17A+ T cells were found to a similar extent in all the three disorders. IL-17A+ granulocytes were more predominant in BP than in LP or PV. Of note, the majority of IL-17A+ cells in LP were neither T cells nor granulocytes. Discussion: Our findings in inflammatory skin infiltrates clearly show a predominant type 1 signature in LP in contrast to a preponderance of type 2 T cells in PV and BP. In contrast to LP, granulocytes and to a much lesser extent CD3+ T cells were a cellular source of IL-17A in BP and PV. These data strongly suggest that different inflammatory cell signatures drive evolving clinically diverse phenotypes of LP, PV and BP despite common target antigens of the skin.

S1 Guideline onychomycosis.

Onychomycosis is a fungal infection of the fingernails and toenails. In Europe, tinea unguium is mainly caused by dermatophytes. The diagnostic workup comprises microscopic examination, culture and/or molecular testing (nail scrapings). Local treatment with antifungal nail polish is recommended for mild or moderate nail infections. In case of moderate to severe onychomycosis, oral treatment is recommended (in the absence of contraindications). Treatment should consist of topical and systemic agents. The aim of this update of the German S1 guideline is to simplify the selection and implementation of appropriate diagnostics and treatment. The guideline was based on current international guidelines and the results of a literature review conducted by the experts of the guideline committee. This multidisciplinary committee consisted of representatives from the German Society of Dermatology (DDG), the German-Speaking Mycological Society (DMykG), the Association of German Dermatologists (BVDD), the German Society for Hygiene and Microbiology (DGHM), the German Society of Pediatric and Adolescent Medicine (DGKJ), the Working Group for Pediatric Dermatology (APD) and the German Society for Pediatric Infectious Diseases (DGPI). The Division of Evidence-based Medicine (dEBM) provided methodological assistance. The guideline was approved by the participating medical societies following a comprehensive internal and external review.

Validation of subjective manual palpation using objective physiological recordings of the cranial rhythmic impulse during osteopathic manipulative intervention.

Intermediate (IM) band physiology in skin blood flow exhibits parallels with the primary respiratory mechanism (PRM) or cranial rhythmic impulse (CRI), controversial concepts of osteopathy in the cranial field (OCF). Owing to inconsistent manual palpation results, validity of evidence of PRM/CRI activity has been questionable. We therefore tried to validate manual palpation combining instrumented tracking and algorithmic objectivation of frequencies, amplitudes, and phases. Using a standard OCF intervention, cranial vault hold (CVH), two OCF experts palpated and digitally marked CRI frequencies in 25 healthy adults. Autonomic nervous system (ANS) activity in low frequency (LF) and IM band in photoplethysmographic (PPG) forehead skin recordings was probed with momentary frequency of highest amplitude (MFHA) and wavelet amplitude spectra (WAS) in examiners and participants. Palpation errors and frequency expectation bias during CVH were analyzed for phases of MFHA and CRI. Palpated CRI frequencies (0.05-0.08 Hz) correlated highly with mean MFHA frequencies with 1:1 ratio in 77% of participants (LF-responders; 0.072 Hz) and with 2:1 ratio in 23% of participants (IM-responders; 0.147 Hz). WAS analysis in both groups revealed integer number (harmonic) waves in (very) low and IM bands in > 98% of palpated intervals. Phase analyses in participants and examiners suggested synchronization between MFHA and CRI in a subset of LF-responders. IM band physiology in forehead PPG may offer a sensible physiological correlate of palpated CRI activity. Possible coordination or synchronization effects with additional physiological signals and between examiners and participants should be investigated in future studies.

Tissue-specific antigen-presenting cells contribute to distinct phenotypes of allergy.

Antigen-presenting cells (APCs) are critical cells bridging innate and adaptive immune responses by taking up, processing, and presenting antigens to naïve T cells. At steady state, APCs thus control both tissue homeostasis and the induction of tolerance. In allergies however, APCs drive a Th2-biased immune response that is directed against otherwise harmless antigens from the environment. The main types of APCs involved in the induction of allergy are dendritic cells, monocytes, and macrophages. However, these cell types can be further divided into local, tissue-specific populations that differ in their phenotype, migratory capacity, T-cell activating potential, and production of effector molecules. Understanding if distinct populations of APCs contribute to either tissue-specific immune tolerance, allergen sensitization, or allergic inflammation will allow us to better understand disease pathology and develop targeted treatment options for different stages of allergic disease. Therefore, this review describes the main characteristics, phenotypes, and effector molecules of the APCs involved in the induction of allergen-specific Th2 responses in affected barrier sites, such as the skin, nose, lung, and gastrointestinal tract. Furthermore, we highlight open questions that remain to be addressed to fully understand the contribution of different APCs to allergic disease.

Distal Nerve Transfers in High Peroneal Nerve Lesions: An Anatomical Feasibility Study.

The peroneal nerve is one of the most commonly injured nerves of the lower extremity. Nerve grafting has been shown to result in poor functional outcomes. The aim of this study was to evaluate and compare anatomical feasibility as well as axon count of the tibial nerve motor branches and the tibialis anterior motor branch for a direct nerve transfer to reconstruct ankle dorsiflexion. In an anatomical study on 26 human body donors (52 extremities) the muscular branches to the lateral (GCL) and the medial head (GCM) of the gastrocnemius muscle, the soleus muscle (S) as well as the tibialis anterior muscle (TA) were dissected, and each nerve's external diameter was measured. Nerve transfers from each of the three donor nerves (GCL, GCM, S) to the recipient nerve (TA) were performed and the distance between the achievable coaptation site and anatomic landmarks was measured. Additionally, nerve samples were taken from eight extremities, and antibody as well immunofluorescence staining were performed, primarily evaluating axon count. The average diameter of the nerve branches to the GCL was 1.49 ± 0.37, to GCM 1.5 ± 0.32, to S 1.94 ± 0.37 and to TA 1.97 ± 0.32 mm, respectively. The distance from the coaptation site to the TA muscle was 43.75 ± 12.1 using the branch to the GCL, 48.31 ± 11.32 for GCM, and 19.12 ± 11.68 mm for S, respectively. The axon count for TA was 1597.14 ± 325.94, while the donor nerves showed 297.5 ± 106.82 (GCL), 418.5 ± 62.44 (GCM), and 1101.86 ± 135.92 (S). Diameter and axon count were significantly higher for S compared to GCL as well as GCM, while regeneration distance was significantly lower. The soleus muscle branch exhibited the most appropriate axon count and nerve diameter in our study, while also reaching closest to the tibialis anterior muscle. These results indicate the soleus nerve transfer to be the favorable option for the reconstruction of ankle dorsiflexion, in comparison to the gastrocnemius muscle branches. This surgical approach can be used to achieve a biomechanically appropriate reconstruction, in contrast to tendon transfers which generally only achieve weak active dorsiflexion.

General Population and Surgeon Preferences for Pollicization Versus Toe-To-Thumb Transfer for Reconstruction of Traumatic Thumb Loss in Adults: An International, Multi-Center Survey Study.

PURPOSE: Data objectively comparing outcomes following pollicization versus toe-to-thumb transfer for reconstruction after traumatic thumb amputation in adults remains sparse. Given that this decision is reliant on personal preference, it is important to understand the subjective nature of these preferences, particularly in the context of culture. The purpose of this study was to compare Eastern and Western societal and hand surgeon preferences for pollicization versus toe-to-thumb transfer for traumatic thumb reconstruction. METHODS: Investigators from 6 international locations recruited local hand surgeons and members of the general population. Austria, Germany, the United States, and Spain were grouped as "Western" nations. China and India separately represented "Eastern" nations. Participants completed a questionnaire evaluating their personal preferences for pollicization and toe-to-thumb transfer. The questions posed to the general population and hand surgeons were identical. Demographic data were also collected. RESULTS: When comparing the Western nations, China, and India, there was no difference in personal preferences within the general population for pollicization versus toe-to-thumb transfer. In contrast, most Indian hand surgeons favored toe-to-thumb transfer and most Western surgeons were uncertain about which procedure they would favor. Surgeons had more optimistic expectations regarding postoperative hand function, new thumb sensation, and hand appearance following pollicization than the general population. Similarly, for toe-to-thumb transfer, a greater proportion of surgeons predicted good-to-excellent function, sensation, and appearance. CONCLUSIONS: There was no clear, observed "East" versus "West" difference in the general population's personal preferences for pollicization versus toe-to-thumb transfer among study participants. The members of the general population and hand surgeons had different outcome expectations. CLINICAL RELEVANCE: Understanding how culture influences patient and hand surgeon preferences for pollicization versus toe-to-thumb transfer may help guide future decision-making for traumatic thumb reconstruction.

Outcome After Reconstruction of 43 Digital Nerve Defects With Muscle-in-Vein Conduits.

PURPOSE: Muscle-in-vein conduits provide an alternative for bridging digital nerve defects when tension-free suture is not possible. Low donor site morbidity and absence of additional costs are favorable advantages compared with autografts or conduits. METHODS: We retrospectively reviewed 37 patients with 43 defects of proper palmar digital nerves. Primary repair by muscle-in-vein conduits was performed in 22 cases, whereas 21 cases underwent secondary reconstruction. Recovery of sensibility was assessed using static and moving 2-point discrimination and Semmes-Weinstein monofilament testing. Results were compared with the contralateral side serving as a control. Outcome data were stratified according to international guidelines and evaluated for differences in terms of age, gap length, time of reconstruction, and concomitant injuries. RESULTS: The median gap length was 20 mm (range, 9-60 mm). After a median follow-up of 25.0 months (interquartile range, 29.0 months), the median static and moving 2-point discrimination were 7.0 mm and 5.0 mm (interquartile range, 3.0 mm), respectively. The evaluation with Semmes-Weinstein monofilament revealed a median reduction of sensibility of 2 levels compared with the contralateral side. According to the American Society for Surgery of the Hand guidelines, 81.4% of the results were classified as excellent or good, whereas fair and poor results were noted in 9.3% of the cases each. The modified Highet and Sander's criteria rated complete clinical recovery in 13 cases; 23 results were regarded as S3+. CONCLUSIONS: Muscle-in-vein conduits can be considered for primary and secondary reconstruction of digital nerves. Successful sensory recovery in terms of measurable 2-point discrimination was achieved in 91% of all cases. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

The regional distribution of resident immune cells shapes distinct immunological environments along the murine epididymis.

The epididymis functions as transition zone for post-testicular sperm maturation and storage and faces contrasting immunological challenges, i.e. tolerance towards spermatozoa vs. reactivity against pathogens. Thus, normal organ function and integrity relies heavily on a tightly controlled immune balance. Previous studies described inflammation-associated tissue damage solely in the distal regions (corpus, cauda), but not in the proximal regions (initial segment, caput). To understand the observed region-specific immunity along the epididymal duct, we have used an acute bacterial epididymitis mouse model and analyzed the disease progression. Whole transcriptome analysis using RNAseq 10 days post infection showed a pro-inflammatory environment within the cauda, while the caput exhibited only minor transcriptional changes. High-dimensional flow cytometry analyses revealed drastic changes in the immune cell composition upon infection with uropathogenic Escherichia coli. A massive influx of neutrophils and monocytes was observed exclusively in distal regions and was associated with bacterial appearance and tissue alterations. In order to clarify the reasons for the region-specific differences in the intensity of immune responses, we investigated the heterogeneity of resident immune cell populations under physiological conditions by scRNASeq analysis of extravascular CD45+ cells. Twelve distinct immune cell subsets were identified, displaying substantial differences in distribution along the epididymis as further assessed by flow cytometry and immunofluorescence staining. Macrophages constituted the majority of resident immune cells and were further separated in distinct subgroups based on their transcriptional profile, tissue location and monocyte-dependence. Crucially, the proximal and distal regions showed striking differences in their immunological landscapes. These findings indicate that resident immune cells are strategically positioned along the epididymal duct, potentially providing different immunological environments required for addressing the contrasting immunological challenges and thus, preserving tissue integrity and organ function.

Cardio-respiratory motion-corrected 3D cardiac water-fat MRI using model-based image reconstruction.

PURPOSE: Myocardial fat infiltrations are associated with a range of cardiomyopathies. The purpose of this study was to perform cardio-respiratory motion-correction for model-based water-fat separation to image fatty infiltrations of the heart in a free-breathing, non-cardiac-triggered high-resolution 3D MRI acquisition. METHODS: Data were acquired in nine patients using a free-breathing, non-cardiac-triggered high-resolution 3D Dixon gradient-echo sequence and radial phase encoding trajectory. Motion correction was combined with a model-based water-fat reconstruction approach. Respiratory and cardiac motion models were estimated using a dual-mode registration algorithm incorporating both motion-resolved water and fat information. Qualitative comparisons of fat structures were made between 2D clinical routine reference scans and reformatted 3D motion-corrected images. To evaluate the effect of motion correction the local sharpness of epicardial fat structures was analyzed for motion-averaged and motion-corrected fat images. RESULTS: The reformatted 3D motion-corrected reconstructions yielded qualitatively comparable fat structures and fat structure sharpness in the heart as the standard 2D breath-hold. Respiratory motion correction improved the local sharpness on average by 32% ± 24% with maximum improvements of 81% and cardiac motion correction increased the sharpness further by another 15% ± 11% with maximum increases of 31%. One patient showed a fat infiltration in the myocardium and cardio-respiratory motion correction was able to improve its visualization in 3D. CONCLUSION: The 3D water-fat separated cardiac images were acquired during free-breathing and in a clinically feasible and predictable scan time. Compared to a motion-averaged reconstruction an increase in sharpness of fat structures by 51% ± 27% using the presented motion correction approach was observed for nine patients.

Intratumoural administration of an NKT cell agonist with CpG promotes NKT cell infiltration associated with an enhanced antitumour response and abscopal effect.

Intratumoural administration of unmethylated cytosine-phosphate-guanine motifs (CpG) to stimulate toll-like receptor (TLR)-9 has been shown to induce tumour regression in preclinical studies and some efficacy in the clinic. Because activated natural killer T (NKT) cells can cooperate with pattern-recognition via TLRs to improve adaptive immune responses, we assessed the impact of combining a repeated dosing regimen of intratumoural CpG with a single intratumoural dose of the NKT cell agonist α-galactosylceramide (α-GalCer). The combination was superior to CpG alone at inducing regression of established tumours in several murine tumour models, primarily mediated by CD8+ T cells. An antitumour effect on distant untreated tumours (abscopal effect) was reliant on sustained activity of NKT cells and was associated with infiltration of KLRG1+ NKT cells in tumours and draining lymph nodes at both injected and untreated distant sites. Cytometric analysis pointed to increased exposure to type I interferon (IFN) affecting many immune cell types in the tumour and lymphoid organs. Accordingly, antitumour activity was lost in animals in which dendritic cells (DCs) were incapable of signaling through the type I IFN receptor. Studies in conditional ablation models showed that conventional type 1 DCs and plasmacytoid DCs were required for the response. In tumour models where the combined treatment was less effective, the addition of tumour-antigen derived peptide, preferably conjugated to α-GalCer, significantly enhanced the antitumour response. The combination of TLR ligation, NKT cell agonism, and peptide delivery could therefore be adapted to induce responses to both known and unknown antigens.

Actual prosthetic usage in relation to functional outcomes and wearing time in individuals with below-elbow amputation.

BACKGROUND: Wearing time of a prosthesis is regarded as an indicator for success of prosthetic rehabilitation. However, prostheses are frequently worn for esthetic purposes only. Although different supervised measurements to assess prosthetic dexterity are used, it is not clear how performance in such tests translates into actual use in everyday life. OBJECTIVES: To evaluate the actual daily use of the prosthetic device in patients with below-elbow amputations by recording the number of grasping motions. STUDY DESIGN: Observational study. METHODS: Upper extremity function was evaluated using different objective and timed assessments in five unilateral patients with below-elbow amputations. In addition, patients reported daily wearing time, and the number of performed prosthetic movements over a period of at least three months was recorded. RESULTS: The patients achieved a mean Southampton Hand Assessment Procedure score of 66.60 ± 18.64 points. The average blocks moved in the Box and Block Test were 20.80 ± 7.46, and the mean score in the Action Research Arm Test was 37.20 ± 5.45. The mean time for the Clothespin-Relocation Test was 26.90 ± 11.61 seconds. The patients reported a wearing time of an average of 12.80 ± 3.11 hours per day. The mean number of prosthetic motions performed each day was 257.23 ± 192.95 with a range from 23.07 to 489.13. CONCLUSIONS: Neither high functionality nor long wearing times necessitated frequent use of a prosthesis in daily life. However, frequent daily motions did translate into good functional scores, indicating that regular device use in different real-life settings relates to functionality.

Motion-compensated fat-water imaging for 3D cardiac MRI at ultra-high fields.

PURPOSE: Respiratory motion-compensated (MC) 3D cardiac fat-water imaging at 7T. METHODS: Free-breathing bipolar 3D triple-echo gradient-recalled-echo (GRE) data with radial phase-encoding (RPE) trajectory were acquired in 11 healthy volunteers (7M\4F, 21-35 years, mean: 30 years) with a wide range of body mass index (BMI; 19.9-34.0 kg/m2 ) and volunteer tailored B1+ shimming. The bipolar-corrected triple-echo GRE-RPE data were binned into different respiratory phases (self-navigation) and were used for the estimation of non-rigid motion vector fields (MF) and respiratory resolved (RR) maps of the main magnetic field deviations (ΔB0 ). RR ΔB0 maps and MC ΔB0 maps were compared to a reference respiratory phase to assess respiration-induced changes. Subsequently, cardiac binned fat-water images were obtained using a model-based, respiratory motion-corrected image reconstruction. RESULTS: The 3D cardiac fat-water imaging at 7T was successfully demonstrated. Local respiration-induced frequency shifts in MC ΔB0 maps are small compared to the chemical shifts used in the multi-peak model. Compared to the reference exhale ΔB0 map these changes are in the order of 10 Hz on average. Cardiac binned MC fat-water reconstruction reduced respiration induced blurring in the fat-water images, and flow artifacts are reduced in the end-diastolic fat-water separated images. CONCLUSION: This work demonstrates the feasibility of 3D fat-water imaging at UHF for the entire human heart despite spatial and temporal B1+ and B0 variations, as well as respiratory and cardiac motion.

Current rates of prosthetic usage in upper-limb amputees - have innovations had an impact on device acceptance?

PURPOSE: There is a large body of evidence demonstrating high rates of prosthesis abandonment in the upper extremity. However, these surveys were conducted years ago, thus the influence of recent refinements in prosthetic technology on acceptance is unknown. This study aims to gather current data on prosthetic usage, to assess the effects of these advancements. MATERIALS AND METHODS: A questionnaire was sent to 68 traumatic upper limb amputees treated within the Austrian Trauma Insurance Agency between the years 1996 and 2016. Responses were grouped by the year of amputation to assess the effect of time. RESULTS: The rejection rate at all levels of amputation was 44%. There was no significant difference in acceptance between responders amputated before or after 2006 (p = 0.939). Among users, 92.86% (n = 13) used a myoelectric, while only one amputee (7.14%, n = 1) used a body-powered device. Most responders complained about the comfort (60.87%, n = 14) as well as the weight of the device (52.17%, n = 12). CONCLUSIONS: The advancements of the last decade in the arena of upper limb prosthetics have not yet achieved a significant change in prosthetic abandonment within this study cohort. Although academic solutions have been presented to tackle patient's complaints, clinical reality still shows high rejection rates of cost-intensive prosthetic devices.Implications for rehabilitationAbandonment rates in prosthetic rehabilitation after upper limb amputation have shown to be 50% and higher.The advancements of the last decade in the arena of upper limb prosthetics have not yet achieved a significant change in prosthetic abandonment.Well-structured and patient-tailored prosthetic training as well as ensuring the amputee's active participation in the decision making process will most likely improve prosthetic acceptance.

Basophils control T cell priming through soluble mediators rather than antigen presentation.

Basophils play an important role in the development of type 2 immunity and have been linked to protective immunity against parasites but also inflammatory responses in allergic diseases. While typically classified as degranulating effector cells, different modes of cellular activation have been identified, which together with the observation that different populations of basophils exist in the context of disease suggest a multifunctional role. In this review we aim to highlight the role of basophils play in antigen presentation of type 2 immunity and focus on the contribution basophils play in the context of antigen presentation and T cell priming. We will discuss evidence suggesting that basophils perform a direct role in antigen presentation and relate it to findings that indicate cellular cooperation with professional antigen-presenting cells, such as dendritic cells. We will also highlight tissue-specific differences in basophil phenotypes that might lead to distinct roles in cellular cooperation and how these distinct interactions might influence immunological and clinical outcomes of disease. This review thus aims to consolidate the seemingly conflicting literature on the involvement of basophils in antigen presentation and tries to find a resolution to the discussion whether basophils influence antigen presentation through direct or indirect mechanisms.

Homeostatic IL-13 in healthy skin directs dendritic cell differentiation to promote TH2 and inhibit TH17 cell polarization.

The signals driving the adaptation of type 2 dendritic cells (DC2s) to diverse peripheral environments remain mostly undefined. We show that differentiation of CD11blo migratory DC2s-a DC2 population unique to the dermis-required IL-13 signaling dependent on the transcription factors STAT6 and KLF4, whereas DC2s in lung and small intestine were STAT6-independent. Similarly, human DC2s in skin expressed an IL-4 and IL-13 gene signature that was not found in blood, spleen and lung DCs. In mice, IL-13 was secreted homeostatically by dermal innate lymphoid cells and was independent of microbiota, TSLP or IL-33. In the absence of IL-13 signaling, dermal DC2s were stable in number but remained CD11bhi and showed defective activation in response to allergens, with diminished ability to support the development of IL-4+GATA3+ helper T cells (TH), whereas antifungal IL-17+RORγt+ TH cells were increased. Therefore, homeostatic IL-13 fosters a noninflammatory skin environment that supports allergic sensitization.