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Atopic dermatitis (AD) is a common, chronic inflammatory skin disorder driven by an intricate interplay of genetic, environmental, and immunological factors. As a clinically heterogenous condition, AD may be stratified into subtypes based on factors including, chronicity, immunoglobulin E levels, severity, age, and ethnicity. Transcriptomic and proteomic analyses in skin and blood help elucidate the underlying molecular mechanisms of these AD subtypes, referred to as AD endotypes. Further characterizing AD endotypes using reliable biomarkers can facilitate the development of more effective and personalized therapeutics and improve our tools for monitoring disease progression and therapeutic response across a diverse subset of patients. Here, we aim to provide perspective on the latest research regarding AD stratification using skin and blood-based studies and insight into the implications of these findings on the future of AD research and clinical practice. The precise stratification of AD endotypes will allow for the development of reliable biomarkers and a more personalized medical treatment approach. Clinical practice and trials will eventually be able to bridge clinical with molecular data to optimize individualized treatments and more effectively monitor treatment response. [ABSTRACT FROM AUTHOR]

Background: Our knowledge of etiopathogenesis of atopic dermatitis (AD) is largely derived from skin biopsies, which are associated with pain, scarring and infection. In contrast, tape‐stripping is a minimally invasive, nonscarring technique to collect skin samples. Methods: To construct a global AD skin transcriptomic profile comparing tape‐strips to whole‐skin biopsies, we performed RNA‐seq on tape‐strips and biopsies taken from the lesional skin of 20 moderate‐to‐severe AD patients and the skin of 20 controls. Differentially expressed genes (DEGs) were defined by fold‐change (FCH) ≥2.0 and false discovery rate <0.05. Results: We detected 4104 (2513 Up; 1591 Down) and 1273 (546 Up; 727 Down) DEGs in AD versus controls, in tape‐strips and biopsies, respectively. Although both techniques captured dysregulation of key immune genes, tape‐strips showed higher FCHs for innate immunity (IL‐1B, IL‐8), dendritic cell (ITGAX/CD11C, FCER1A), Th2 (IL‐13, CCL17, TNFRSF4/OX40), and Th17 (CCL20, CXCL1) products, while biopsies showed higher upregulation of Th22 associated genes (IL‐22, S100As) and dermal cytokines (IFN‐γ, CCL26). Itch‐related genes (IL‐31, TRPV3) were preferentially captured by tape‐strips. Epidermal barrier abnormalities were detected in both techniques, with terminal differentiation defects (FLG2, PSORS1C2) better represented by tape‐strips and epidermal hyperplasia changes (KRT16, MKI67) better detected by biopsies. Conclusions: Tape‐strips and biopsies capture overlapping but distinct features of the AD molecular signature, suggesting their respective utility for monitoring specific AD‐related immune, itch, and barrier abnormalities in clinical trials and longitudinal studies. [ABSTRACT FROM AUTHOR]

Patients with atopic dermatitis (AD) have systemic biomarker dysregulation that differs by age group; however, the proteomic characteristics of these age-based changes are unknown. To profile blood proteins of patients with AD across different age groups versus age-appropriate controls. Using the Olink high-throughput proteomic platform, we profiled 375 serum proteins of 20 infants (age, 0-5 years), 39 children (age, 6-11 years), 21 adolescents (age, 12-17 years), and 20 adults (age, ≥18 years) with moderate-to-severe AD and 83 age-appropriate controls. Each group presented a distinct systemic proteomic signature. Th2-related proteins were increased in infant AD and further intensified with age through adolescence and adulthood (interleukin 4/CCL13/CCL17). In contrast, Th1 axis down-regulation was detected in infants with AD and gradually reversed to increased Th1 products (interferon γ/CXCL9/CXCL10/CCL2) in patients with AD from childhood to adulthood. Despite their short disease duration, infants already had evidence of systemic inflammation, with significant upregulation of innate immunity (interleukin 17C/ interleukin-1RN), T-cell activation/migration (CCL19), Th2 (CCL13/CCL17), and Th17 (PI3) proteins. Adults with AD present unique upregulation of cardiovascular proteins related to coagulation and diabetes. Cross-sectional observational study with a single time point. Systemic immune signatures of AD are age-specific beyond the shared Th2 immune activation. These data advocate for precision medicine approaches based on age-specific AD profiles. [ABSTRACT FROM AUTHOR]

Background: The mechanisms driving alopecia areata (AA) are still unclear, hindering development of targeted therapeutics. Specific Th2 targeting with dupilumab in AA provides a unique opportunity to dissect its pathogenesis and explore the role of Th2 pathway. Methods: We evaluated changes in scalp biomarkers in AA patients (with and without concomitant atopy) randomized to weekly dupilumab or placebo for 24 weeks, followed by open‐label dupilumab for 24 weeks. Changes in biomarker levels were measured at weeks 12, 24, and 48 and were also correlated with clinical hair regrowth. Results: At week 24, preceding clinical hair regrowth outcomes, only dupilumab‐treated patients presented significant suppression of cellular infiltrates, and multiple Th2‐related, markers (CCL13/MCP‐4, CCL18/PARC, CCL26/eotaxin‐3, CCL24/Eotaxin‐2), coupled with significant upregulation in the hair keratins. Th1‐related suppression was evident later (week 48) when all patients received open‐label dupilumab. Results were more pronounced in atopic AA patients, that showed 48% and 97% improvements in the lesional AA scalp profile at weeks 24 and 48, respectively, while 2% worsening was seen in the placebo arm at week 24. Moreover, placebo‐treated patients presented 54% worsening in hair keratins when compared with baseline at week 24. At week 24, increases in hair keratins showed significant correlations only with decreases in Th2‐related markers. Conclusions: Scalp biomarkers provide evidence of dupilumab efficacy in AA, detected even prior to clinical response, with exclusive correlations between early suppression of Th2 markers and increased hair keratins. These findings strengthen previous reports suggesting a possible role for Th2 cytokines as AA drivers. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) is a heterogeneous, chronic inflammatory skin disease linked to skin microbiome dysbiosis with reduced bacterial diversity and el)evated relative abundance of Staphylococcus aureus (S. aureus). Objectives: We aimed to characterize the yet incompletely understood association between the skin microbiome and patients' demographic and clinical cofactors in relation to AD severity. Methods: The skin microbiome in 48 adult moderate-to-severe AD patients was investigated using next-generation deep sequencing (16S rRNA gene, V1–V3 re)gion) followed by denoising (DADA2) to obtain amplicon sequence variant (ASV) composition. Results: In lesional skin, AD severity was associated with S. aureus relative abun)dance (rS = 0.53, p<0.001) and slightly better with the microbiome diversity measure Evenness (rS = −0.58, p<0.001), but not with Richness. Multiple regression confirmed the association of AD severity with microbiome diversity, including Shannon (in le)sional skin, p<0.001), Evenness (in non-lesional skin, p = 0.015) or S. aureus relative abundance (p<0.012), and with patient's IgE levels (p<0.001), race (p<0.032), age (p<0.034) and sex (p = 0.012). The lesional model explained 62% of the variation in AD severity, and the non-lesional model 50% of the variation. Conclusions: Our results specify the frequently reported “reduced diversity” of the AD-related skin microbiome to reduced Evenness, which was in turn mainly driven by S. aureus relative abundance, rather than to a reduced microbiome Richness. Finding associations between AD severity, the skin microbiome and patient's cofac)tors is a key aspect in developing new personalized AD treatments, particularly those targeting the AD microbiome. [ABSTRACT FROM AUTHOR]

Background: Treatment of inflammatory skin diseases, including atopic dermatitis (AD) and psoriasis, is undergoing transformative changes, highlighting the need to develop experimental models of skin inflammation in humans to predict treatment responses. Methods: We topically or intradermally administered four common sensitizers (dust mite (DM), diphencyprone (DPCP), nickel (Ni), and purified protein derivative (PPD)) to the backs of 40 healthy patients and the skin hypersensitivity response was biopsied and evaluated using immunohistochemistry, RNA‐seq, and RT‐PCR. Results: All agents induced strong increases in cellular infiltrates (T‐cells and dendritic cells) as compared to untreated skin (p <.05), with variable T helper polarization. Overall, DPCP induced the strongest immune responses across all pathways, including innate immunity (IL‐1α, IL‐8), Th1 (IFNγ, CXCL10), Th2 (IL‐5, CCL11), and Th17 (CAMP/LL37) products, as well as the highest regulatory tone (FOXP3, IL‐34, IL‐37) (FDR <0.01). Nickel induced Th17 (IL‐17A), Th1 (CXCL10) and Th2 (IL‐4R) immune responses to a lesser extent than DPCP (p <.05). PPD induced predominantly Th1 (IFNγ, CXCL10, STAT1) and Th17 inflammation (IL‐17A) (p <.05). DM induced modulation of Th2 (IL‐13, CCL17, CCL18), Th22 (IL‐22), and Th17/Th22 (S100A7/9/12) pathways (p <.05). Barrier defects that characterize both AD and psoriasis were best modeled by DPCP and Ni, followed by PPD, including downregulation of terminal differentiation (FLG, FLG2, LOR, LCEs), tight junction (CLDN1/CLDN8), and lipid metabolism (FA2H, FABP7)‐related markers. Conclusion: Our data imply that DPCP induced the strongest immune response across all pathways, and barrier defects characteristic of AD and psoriasis. [ABSTRACT FROM AUTHOR]

Background: Treatments for alopecia areata (AA) patients with extensive scalp hair loss are limited, and recent evidence supports a role for type 2 T‐cell (Th2)‐immune response in AA. Dupilumab, a monoclonal antibody inhibiting Th2 signaling, approved for type 2 diseases including atopic dermatitis, was evaluated in AA patients. Methods: Alopecia areata patients with and without concomitant atopic dermatitis were randomized 2:1 to receive weekly subcutaneous dupilumab (300 mg) or placebo for 24 weeks, followed by another 24‐week dupilumab open‐label phase. The primary outcome was change from baseline in the Severity of Alopecia Tool (SALT) score at week 24; secondary outcomes included a range of measures of hair regrowth. Results: Forty and 20 patients were assigned to the dupilumab and placebo arms, respectively. At week 24, disease worsening was documented in the placebo arm, with a least‐squares mean change in the SALT score of −6.5 (95% confidence‐interval [CI], −10.4 to −2.6), versus a change of 2.2 (95% CI, −0.6 to 4.94) in the dupilumab arm (p <.05). After 48 weeks of dupilumab treatment, 32.5%, 22.5% and 15% of patients achieved SALT30/SALT50/SALT75 improvement, respectively, while in patients with baseline IgE ≥ 200 IU/ml response rates increased to 53.8%, 46.2%, and 38.5%, respectively. Moreover, baseline IgE predicts treatment response with 83% accuracy. No new safety signals were detected. Conclusions: This hypothesis‐driven trial is the first to indicate the possible pathogenic role of the Th2 axis and Th2 targeting in AA patients. Patient selection based on baseline serum IgE levels may improve treatment results (Clinicaltrials.gov number, NCT03359356). [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is a common inflammatory skin disease associated with barrier disfunction and T SB H sb 2/T SB H sb 22 immune polarity.1,2 Patients with AD are often colonized or infected with I Staphylococcus aureus i ( I S. aureus i ).3 Recent large cohort studies and skin microbiome analyses have identified that AD is dominated by I S. aureus i .4 However, the interaction of cytokines and bacteria in AD skin remains unclear. Keywords: atopic dermatitis; dermatology; infections; inflammation; innate immunity; keratinocytes EN atopic dermatitis dermatology infections inflammation innate immunity keratinocytes 3534 3537 4 11/01/21 20211101 NES 211101 ACKNOWLEDGEMENTS KY was supported by Japan Society for the Promotion of Science (JSPS) overseas research fellowships from 2020 to 2022. TH2 cytokines and Staphylococcus aureus cooperatively induce atopic dermatitis-like transcriptomes. [Extracted from the article]

Background: In atopic dermatitis (AD), some studies have shown an association with increased cardiovascular disease in certain populations. However, other investigations found modest or no association. Despite conflicting results, molecular profiling studies in both AD skin and blood have demonstrated upregulation of atherosclerosis and cardiovascular risk‐related markers. However, the underlying mechanisms connecting AD to vascular inflammation/atherosclerosis are unknown. In this study, we aim to determine factors associated with vascular inflammation/atherosclerosis in AD patients. Methods: We used 18‐FDG PET‐CT to characterize vascular inflammation in AD patients and healthy subjects. In parallel, we assessed their skin and blood immune profiles to determine AD‐related immune biomarkers associated with vascular inflammation. We also assessed levels of circulating microparticles, which are known to be associated with increased cardiovascular risk. Results: We found significant correlations between vascular inflammation and Th2‐related products in skin and blood of AD patients as well as atherosclerosis‐related markers that were modulated by dupilumab. Circulating levels of endothelial microparticles were significantly higher in severe AD patients and tended to correlate with vascular inflammation assessed by PET‐CT. Conclusion: Vascular inflammation in AD is associated with enhanced Th2 response and clinical severity, which may explain cardiovascular comorbidities observed in select AD populations. Larger prospective studies are needed to further evaluate vascular inflammation and cardiovascular events and mortality in AD patients. Finally, as dupilumab treatment demonstrated significant modulation of atherosclerosis‐related genes in AD patients compared to placebo, these data suggest that modulation of vascular inflammation with systemic treatment should be explored in patients with AD. [ABSTRACT FROM AUTHOR]

Background: Flow cytometry is a well‐accepted approach for immune profiling; however, its value is restricted by the limited number of markers that can be analyzed simultaneously. Mass cytometry/CyTOF offers broad‐scale immune characterization integrating large number of parameters. While partial blood phenotyping was reported in atopic dermatitis (AD), patients' comprehensive profiling, critical for leveraging new targeted treatments, is not available. IL‐21 may be involved in inflammatory skin diseases but its role in AD is not well established. Methods: We studied T‐cell polarization in the blood of 20 moderate‐to‐severe AD and 15 controls. Using CyTOF and an unsupervised analysis, we measured the frequencies and mean metal intensities of activated polar CD4+/CD8+ T‐cell subsets. Immunohistochemistry, immunofluorescence, and qRT‐PCR were used to analyze skin samples. Results: Examining 24 surface, intracellular markers, and transcription factors, we identified six CD4+ and five CD8+ T‐cell metaclusters. A CD4+ skin‐homing IL‐13+monocytokine and a novel IL‐13+IL‐21+ multicytokine metaclusters were increased in AD vs. controls (p <.01). While IL‐13 signature characterized both clusters, levels were significantly higher in the IL‐21+ group. Both clusters correlated with AD severity (r = 0.49, p =.029). Manual gating corroborated these results and identified additional multicytokine subsets in AD. Immunohistochemistry and immunofluorescence, validated by mRNA expression, displayed significantly increasedIL‐21 counts and colocalization with IL‐13/IL‐4R in AD skin. Conclusion: A multicytokine signature characterizes moderate‐to‐severe AD, possibly explaining partial therapeutic responses to one cytokine targeting, particularly in severe patients. Prominent IL‐21 signature in blood and skin hints for a potential pathogenic role of IL‐21 in AD. [ABSTRACT FROM AUTHOR]

Although atopic dermatitis (AD) often presents in infancy and persists into adulthood, comparative characterization of AD skin among different pediatric age groups is lacking. We sought to define skin biopsy profiles of lesional and nonlesional AD across different age groups (0-5-year-old infants with disease duration <6 months, 6-11-year-old children, 12-17-year-old adolescents, ≥18-year-old adults) versus age-appropriate controls. We performed gene expression analyses by RNA-sequencing and real-time PCR (RT-PCR) and protein expression analysis using immunohistochemistry. T H 2/T H 22 skewing, including IL-13, CCL17/thymus and activation-regulated chemokine, IL-22, and S100As, characterized the common AD signature, with a global pathway-level enrichment across all ages. Nevertheless, specific cytokines varied widely. For example, IL-33, IL-1RL1/IL-33R, and IL-9, often associated with early atopic sensitization, showed greatest upregulations in infants. T H 17 inflammation presented a 2-peak curve, with highest increases in infants (including IL-17A and IL-17F), followed by adults. T H 1 polarization was uniquely detected in adults, even when compared with adolescents, with significant upregulation in adults of IFN-γ and CXCL9/CXCL10/CXCL11. Although all AD age groups had barrier abnormalities, only adults had significant decreases in filaggrin expression. Despite the short duration of the disease, infant AD presented robust downregulations of multiple barrier-related genes in both lesional and nonlesional skin. Clinical severity scores significantly correlated with T H 2/T H 22-related markers in all pediatric age groups. The shared signature of AD across ages is T H 2/T H 22-skewed, yet differential expression of specific T H 2/T H 22-related genes, other T H pathways, and barrier-related genes portray heterogenetic, age-specific molecular fingerprints. [ABSTRACT FROM AUTHOR]

Molecular studies in atopic dermatitis (AD) are largely restricted to patients with moderate-to-severe disease. Our aim was to evaluate skin and blood abnormalities in mild, moderate, and severe AD. Skin and blood samples were obtained from 61 patients with AD (20 with mild or limited disease, 17 with moderate disease, and 24 with severe disease) and 20 healthy subjects. Immune and barrier markers were measured in lesional, nonlesional, and healthy skin by quantitative real-time PCR and immunohistochemistry, and in blood by using the OLINK proteomic assay. Cellular markers of epidermal hyperplasia and T-cell/dendritic cell infiltration were increased in AD tissues of all patients in all severity groups versus in those of controls, whereas downstream T H 2 cell–, T H 22 cell–, T H 1 cell–, and T H 17 cell–related mediators demonstrated incremental elevations with increasing disease severity, in both lesional and nonlesional skin. Whereas the levels of the T H 2 (IL13, CCL17, and CCL26) and T H 22 (IL-22) cytokines were significantly elevated in both AD lesional and nonlesional skin of all patients regardless of the severity of their disease, patients with mild or limited AD showed increases in their levels of T H 1 cell (IFNG, CXCL9, and CXCL10) and T H 17 cell (IL-17A, CCL20, and CXCL1) markers in lesional but not nonlesional skin. Regulatory T-cell–related mediators (IL-10 and FOXP3) were comparably upregulated in all groups, without displaying the severity-based gradient in other immune axes. Unsupervised clustering aligned samples along a severity spectrum, where nonlesional mild or limited AD skin clustered with the samples from healthy controls. Furthermore, whereas the blood profiles of patients with moderate and severe AD showed gradual increases in the levels of T H 1 cell–, T H 2 cell–, and T H 17 cell–related and atherosclerosis and/or cardiovascular risk (CCL7, FGF21, and IGFBP1) proteins, the blood profiles of patients with mild or limited AD lacked significant differences from those of the controls. Mild and limited AD show high levels of T H 2/T H 22 cell activation that is primarily localized to skin lesions and lacks the systemic inflammation of moderate and severe disease. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Although there is increased understanding of the alopecia areata (AA) pathogenesis based on studies in scalp tissues, little is known about its systemic profile.Objective: To evaluate the blood proteomic signature of AA and determine biomarkers associated with increased disease severity.Methods: In a cross-sectional study, we assessed 350 inflammatory and cardiovascular proteins using OLINK high-throughput proteomics in patients with moderate to severe AA (n = 35), as compared with healthy individuals (n = 36), patients with moderate to severe psoriasis (n = 19), and those with atopic dermatitis (n = 49).Results: Seventy-four proteins were significantly differentially expressed between AA and control individuals (false discovery rate, <.05) including innate immunity (interleukin [IL] 6/IL-8), T helper (Th) type 1 (interferon [IFN] γ/CXCL9/CXCL10/CXCL11), Th2 (CCL13/CCL17/CCL7), Th17 (CCL20/PI3/S100A12), and cardiovascular-risk proteins (OLR1/OSM/MPO/PRTN3). Eighty-six biomarkers correlated with AA clinical severity (P < .05), including Th1/Th2, and cardiovascular/atherosclerosis-related proteins, including SELP/PGLYRP1/MPO/IL-18/OSM (P < .05). Patients with AA totalis/universalis showed the highest systemic inflammatory tone, including cardiovascular risk biomarkers, compared to control individuals and even to patients with atopic dermatitis and those with psoriasis. The AA profile showed some Th1/Th2 differences in the setting of concomitant atopy.Limitations: Our analysis was limited to 350 proteins.Conclusion: This study defined the abnormalities of moderate to severe AA and associated circulatory biomarkers. It shows that AA has systemic immune, cardiovascular, and atherosclerosis biomarker dysregulation, suggesting the need for systemic treatment approaches. [ABSTRACT FROM AUTHOR]

Our current understanding of atopic dermatitis (AD) and psoriasis pathophysiology is largely derived from skin biopsy studies that cause scarring and may be impractical in large-scale clinical trials. Although tape strips show promise as a minimally invasive technique in these common diseases, a comprehensive molecular profiling characterizing and differentiating the 2 diseases in tape strips is unavailable. Our aim was to construct a global transcriptome of tape strips from lesional and nonlesional skin of adults with moderate-to-severe AD and psoriasis. A total of 20 tape strips were obtained from lesional and nonlesional skin of patients with AD and psoriasis and skin from controls (n = 20 each); the strips were subjected to RNA sequencing (RNA-seq), with quantitative RT-PCR validation of immune and barrier biomarkers. We detected RNA-seq profiles in 96 of 100 of samples (96%), with 4123 and 5390 genes differentially expressed in AD and psoriasis lesions versus in controls, respectively (fold change ≥ 2; false discovery rate [FDR] < 0.05). Nonlesional tape-stripped skin from patients with AD was more similar to lesional skin than to nonlesional skin of patients with psoriasis, which showed larger differentiation from lesions. AD and psoriasis tissues shared increases in levels of dendritic cell and T-cell markers (CD3, ITGAX/CD11c, and CD83), but AD tissues showed preferential T H 2 skewing (IL-13, CCL17/TARC, and CCL18), whereas psoriasis was characterized by higher levels of expression of T H 17-related (IL-17A/F and IL-36A/IL-36G), T H 1-related (IFN-γ and CXCL9/CXCL10), and innate immunity–related (nitric oxide synthase 2/inducible nitric oxide synthase and IL-17C) products (FDR < 0.05). Terminal differentiation (FLG2 and LCE5A), tight junction (CLDN8), and lipid biosynthesis and metabolism (FA2H and ALOXE3) products were significantly downregulated in both AD and psoriasis (FDR < 0.05). Nitric oxide synthase 2/inducible nitric oxide synthase expression (determined by quantitative PCR) differentiated AD and psoriasis with 100% accuracy. RNA-seq tape strip profiling detected distinct immune and barrier signatures in lesional and nonlesional AD and psoriasis skin, suggesting their utility as a minimally invasive alternative to biopsies for detecting disease biomarkers. [ABSTRACT FROM AUTHOR]

Background: Skin biopsies promote our understanding of atopic dermatitis/AD pathomechanisms in infants/toddlers with early‐onset AD, but are not feasible in pediatric populations. Tape strips are an emerging, minimally invasive alternative, but global transcriptomic profiling in early pediatric AD is lacking. We aimed to provide global lesional and nonlesional skin profiles of infants/toddlers with recent‐onset, moderate‐to‐severe AD using tape strips. Methods: Sixteen tape strips were collected for RNA‐seq profiling from 19 infants/toddlers (<5 years old; lesional and nonlesional) with early‐onset moderate‐to‐severe AD (≤6 months) and 17 healthy controls. Results: We identified 1829 differentially expressed genes/DEGs in lesional AD and 662 DEGs in nonlesional AD, vs healthy skin (fold‐change ≥2, FDR <0.05), with 100% sample recovery. Both lesional and nonlesional skin showed significant dysregulations of Th2 (CCL17 and IL4R) and Th22/Th17 (IL36G, CCL20, and S100As)‐related genes, largely lacking significant Th1‐skewing. Significant down‐regulation of terminal differentiation (FLG and FLG2), lipid synthesis/metabolism (ELOVL3 and FA2H), and tight junction (CLDN8) genes were primarily seen in lesional AD. Significant negative correlations were identified between Th2 measures and epidermal barrier gene‐subsets and individual genes (FLG with IL‐4R and CCL17; r < −0.4, P <.05). Significant correlations were also identified between clinical measures (body surface area/BSA, pruritus ADQ, and transepidermal water loss/TEWL) with immune and barrier mRNAs in lesional and/or nonlesional AD (FLG/FLG2 with TEWL; r < −0.4, P <.05). Conclusion: RNA‐seq profiling using tape strips in early‐onset pediatric AD captures immune and barrier alterations in both lesional and nonlesional skin. Tape strips provide insight into disease pathomechanisms and cutaneous disease activity. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is a prevalent inflammatory skin disease with a complex pathogenesis involving immune cell and epidermal abnormalities. Despite whole tissue biopsy studies that have advanced the mechanistic understanding of AD, single cell–based molecular alterations are largely unknown. Our aims were to construct a detailed, high-resolution atlas of cell populations and assess variability in cell composition and cell-specific gene expression in the skin of patients with AD versus in controls. We performed single-cell RNA sequencing on skin biopsy specimens from 5 patients with AD (4 lesional samples and 5 nonlesional samples) and 7 healthy control subjects, using 10× Genomics. We created transcriptomic profiles for 39,042 AD (lesional and nonlesional) and healthy skin cells. Fibroblasts demonstrated a novel COL6A5 + COL18A1 + subpopulation that was unique to lesional AD and expressed CCL2 and CCL19 cytokines. A corresponding LAMP3 + dendritic cell (DC) population that expressed the CCL19 receptor CCR7 was also unique to AD lesions, illustrating a potential role for fibroblast signaling to immune cells. The lesional AD samples were characterized by expansion of inflammatory DCs (CD1A + FCER1A +) and tissue-resident memory T cells (CD69 + CD103 +). The frequencies of type 2 (IL13 +)/type 22 (IL22 +) T cells were higher than those of type 1 (IFNG +) in lesional AD, whereas this ratio was slightly diminished in nonlesional AD and further diminished in controls. AD lesions were characterized by expanded type 2/type 22 T cells and inflammatory DCs, and by a unique inflammatory fibroblast that may interact with immune cells to regulate lymphoid cell organization and type 2 inflammation. [ABSTRACT FROM AUTHOR]

Background: Moderate-to-severe atopic dermatitis (AD) is increasingly recognized as a systemic disease, largely due to proteomic blood studies. There are growing efforts to develop AD biomarkers using minimal tissues.Objective: To characterize the AD skin proteomic signature and its relationship with the blood proteome and genomic skin profile in the same individuals.Methods: We evaluated lesional and nonlesional biopsy samples and blood from 20 individuals with moderate-to-severe AD and 28 healthy individuals using Olink Proteomics (Uppsala, Sweden), using 10 μg/10 μL for skin and blood and RNA sequencing of the skin.Results: The AD skin proteome demonstrated significant upregulation in lesional and even in nonlesional skin compared with controls in inflammatory markers (matrix metalloproteinase 12; T-helper cell [Th]2/interleukin [IL]-1 receptor-like 1[IL1RL1]/IL-33R, IL-13, chemokine [C-C motif] ligand [CCL] 17; Th1/C-X-C motif chemokine 10; Th17/Th22/PI3, CCL20, S100A12), and in cardiovascular-associated proteins (E-selectin, matrix metalloproteinases, platelet growth factor, myeloperoxidase, fatty acid binding protein 4, and vascular endothelial growth factor A; false discovery rate, <0.05). Skin proteins demonstrated much higher and significant upregulations (vs controls) compared with blood, suggesting a skin source for the inflammatory/cardiovascular profile. Gene and protein expressions were correlated (r = 0.410, P < .001), with commonly upregulated inflammatory and cardiovascular risk-associated products, suggesting protein translation in skin.Limitations: Our analysis was limited to 354 proteins.Conclusions: The AD skin proteome shows an inflammatory and cardiovascular signature even in nonlesional skin, emphasizing the need for proactive treatment. Skin proteomics presents a sensitive option for biomarker monitoring. [ABSTRACT FROM AUTHOR]

The circulating immune phenotype was defined in adults and young children with early atopic dermatitis (AD), but chronologic changes in the blood of infants and children with AD through adolescence have not been explored. We sought to compare immune activation and cytokine polarization in the blood of 0- to 5-year-old (n = 39), 6- to 11-year-old (n = 26), 12- to 17-year-old (n = 21) and 18-year-old or older (n = 43) patients with AD versus age-matched control subjects. Flow cytometry was used to measure IFN-γ, IL-9, IL-13, IL-17, and IL-22 cytokine levels in CD4+/CD8+ T cells, with inducible costimulator molecule and HLA-DR defining midterm and long-term T-cell activation, respectively, within skin-homing/cutaneous lymphocyte antigen (CLA)+ versus systemic/CLA− T cells. Unsupervised clustering differentiated patients based on their blood biomarker frequencies. Although CLA+ T H 1 frequencies were significantly lower in infants with AD versus all older patients (P <.01), frequencies of CLA+ T H 2 T cells were similarly expanded across all AD age groups compared with control subjects (P <.05). After infancy, CLA− T H 2 frequencies were increased in patients with AD in all age groups, suggesting systemic immune activation with disease chronicity. IL-22 frequencies serially increased from normal levels in infants to highly significant levels in adolescents and adults compared with levels in respective control subjects (P <.01). Unsupervised clustering aligned the AD profiles along an age-related spectrum from infancy to adulthood (eg, inducible costimulator molecule and IL-22). The adult AD phenotype is achieved only in adulthood. Unique cytokine signatures characterizing individual pediatric endotypes might require age-specific therapies. Future longitudinal studies, comparing the profile of patients with cleared versus persistent pediatric AD, might define age-specific changes that predict AD clearance. [ABSTRACT FROM AUTHOR]

Moderate-to-severe atopic dermatitis (AD) has been associated with significant disease burden and systemic abnormalities and often requires systemic treatments. Currently, safe and effective oral systemic treatments for moderate-to-severe AD are not yet available. ASN002 is an oral inhibitor of the Janus kinase/spleen tyrosine kinase signaling pathways, targeting several cytokine axes (T H 2/T H 22/T H 17/T H 1) and epidermal differentiation. We sought to evaluate the effect of ASN002 on the cellular and molecular biomarker profile of patients with moderate-to-severe AD and to correlate changes in biomarkers to improvements in clinical severity measures and pruritus. Thirty-six patients with moderate-to-severe AD were randomized to groups with dose escalation of ASN002 (20, 40, and 80 mg) and a placebo group. Skin biopsy specimens were performed at baseline, day 15, and day 29. Gene expression studies were conducted by using microarray and quantitative RT-PCR, and cellular infiltrates and protein expression were studied by using immunohistochemistry. ASN002 reversed the lesional skin transcriptome toward a nonlesional phenotype. It also rapidly and significantly suppressed key inflammatory pathways implicated in AD pathogenesis, including T H 2 (IL4 receptor [IL4R] , IL13 , CCL13 /monocyte chemoattractant protein 4, CCL17 /thymus and activation-regulated chemokine, CCL18 /pulmonary and activation-regulated chemokine, CCL22 /macrophage-derived chemokine, and CCL26 /eotaxin-3), T H 17/T H 22 (lipocalins, PI3 /elafin, CCL20 , S100A7 / S100A8 / S100A9 , and IL36G / IL36RN), and T H 1 (IFNG , CXCL9 / CXCL11 , and MX1) axes and barrier-related measures (filaggrin [FLG] and CLDN23). Significant improvements in AD gene signatures were observed predominantly in the 40- and 80-mg groups. Smaller and largely nonsignificant molecular changes were seen in the 20-mg and placebo groups. The Janus kinase/spleen tyrosine kinase inhibitor ASN002 significantly suppressed key AD inflammatory pathways, corresponding to clinical response. ASN002 might be an effective novel therapeutic agent for moderate-to-severe AD. [ABSTRACT FROM AUTHOR]

Background: Despite increasing evidence that adults with long-standing atopic dermatitis (AD) have systemic inflammation, little is known about systemic inflammation in recent-onset early pediatric AD.Objective: To analyze blood inflammatory proteins of early pediatric AD.Methods: Using high-throughput proteomics (proximity extension assay), we assessed 257 inflammatory and cardiovascular risk proteins in the blood of 30 children with moderate to severe AD younger than 5 years of age (within 6 months of onset) compared with age-matched pediatric control individuals and adult patients with AD.Results: In pediatric AD blood, T helper (Th) type 2 (CCL13, CCL22) and Th17 (peptidase inhibitor-3/elafin) markers were increased, together with markers of tissue remodeling (matrix metalloproteinases 3/9/10, urokinase receptor), endothelial activation (E-selectin), T-cell activation (IL2RA), neutrophil activation (myeloperoxidase), lipid metabolism (FABP4), and growth factors (FGF21, transforming growth factor-α). Total numbers of dysregulated proteins were smaller in pediatric AD (n = 22) than in adult AD (n = 61). Clinical severity scores were positively correlated with receptors for interleukins 33 and 36 and inversely correlated with some Th1 markers (interferon gamma, CXCL11).Limitations: Different baseline expression levels in healthy pediatric vs adult samples.Conclusions: Within months of pediatric AD onset, systemic immune activation is present, with Th2/Th17 skewing but otherwise different proteomic patterns from adult AD. Future correlation of proteomic patterns with disease course, comorbidity development, and drug response may yield predictive biomarkers. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) shows differential clinical presentation in older compared with younger patients. Nevertheless, changes in the AD molecular profile with age are unknown. We sought to characterize age-related changes in the AD profile. We evaluated age-specific changes in lesional and nonlesional tissues and blood from patients with moderate-to-severe AD (n = 246) and age-matched control subjects (n = 71) using immunohistochemistry, quantitative real-time PCR, and Singulex in a cross-sectional study. Patients were analyzed by age group (18-40, 41-60, and ≥61 years). Although disease severity/SCORAD scores were similar across AD age groups (mean, approximately 60 years; P =.873), dendritic cell infiltrates (CD1b+ and FcεRI+, P <.05) decreased with age. T H 2 measures (IL5 , IL13 , CCL13 , CCL18 , and CCL26) significantly decreased with age in patients with AD, despite increasing with age in control subjects. Consistent with T H 2 axis decreases, serum IgE levels and eosinophil counts negatively correlated with age in patients with AD (r = −0.24 and r = −0.23, respectively; P <.05). T H 22-secreted IL 22 expression levels also decreased with age uniquely in patients with AD (P <.05). Expression of T H 1-related (IFNG , IL12/23p40 , STAT1 , and CXCL9 ; P <.05 for CXCL9) and T H 17-related (IL 17A and IL 20 ; P <.05 for IL 20) markers increased with age in both patients with AD and control subjects. Expression of terminal differentiation measures significantly increased in older patients with AD (loricrin [LOR] and filaggrin [FLG] , P <.05), whereas expression of S100As (S100A8 , P <.01) and hyperplasia markers (epidermal thickness, keratin 16, and Ki67; P <.05 for keratin 16) decreased. Serum trends in AD mimicked skin findings, with T H 2 downregulation (CCL26; r = −0.32, P <.1) and T H 1 upregulation (IFN-γ; r = 0.48, P <.01) with age. The adult AD profile varies with age. Although T H 1/T H 17 skewing increases in both patients with AD and control subjects, patients with AD show unique decreases in T H 2/T H 22 polarization and normalization of epithelial abnormalities. Thus age-specific treatment approaches might be beneficial for AD. [ABSTRACT FROM AUTHOR]

Peripheral blood skin-homing/cutaneous lymphocyte antigen (CLA)+ T cells emerge as biomarkers of cutaneous immune activation in patients with inflammatory skin diseases (atopic dermatitis [AD] and alopecia areata [AA]). However, blood phenotyping across these subsets is not yet available in patients with vitiligo. We sought to measure cytokine production by circulating skin-homing (CLA+) versus systemic (CLA−) "polar" CD4+/CD8+ ratio and activated T-cell subsets in patients with vitiligo compared with patients with AA, AD, or psoriasis and control subjects. Flow cytometry was used to measure levels of the cytokines IFN-γ, IL-13, IL-9, IL-17, and IL-22 in CD4+/CD8+ T cells in the blood of 19 patients with moderate-to-severe nonsegmental/generalized vitiligo, moderate-to-severe AA (n = 32), psoriasis (n = 24), or AD (n = 43) and control subjects (n = 30). Unsupervised clustering differentiated subjects into groups based on cellular frequencies. Patients with Vitiligo showed the highest CLA+/CLA− T H 1/type 1 cytotoxic T-cell polarization, with parallel T H 2/T H 9/T H 17/T H 22 level increases to levels often greater than those seen in patients with AA, AD, or psoriasis (P <.05). Total regulatory T-cell counts were lower in patients with vitiligo than in control subjects and patients with AD or psoriasis (P <.001). Vitiligo severity correlated with levels of multiple cytokines (P <.1), whereas duration was linked with IFN-γ and IL-17 levels (P <.04). Patients and control subjects grouped into separate clusters based on blood biomarkers. Vitiligo is characterized by a multicytokine polarization among circulating skin-homing and systemic subsets, which differentiates it from other inflammatory/autoimmune skin diseases. Future targeted therapies should delineate the relative contribution of each cytokine axis to disease perpetuation. [ABSTRACT FROM AUTHOR]

Background Ichthyoses are a group of rare skin disorders lacking effective treatments. Although genetic mutations are progressively delineated, comprehensive molecular phenotyping of ichthyotic skin could suggest much-needed pathogenesis-based therapy. Objective We sought to profile the molecular fingerprint of the most common orphan ichthyoses. Methods Gene, protein, and serum studies were performed on skin and blood samples from 29 patients (congenital ichthyosiform erythroderma, n = 9; lamellar ichthyosis, n = 8; epidermolytic ichthyosis, n = 8; and Netherton syndrome, n = 4), as well as age-matched healthy control subjects (n = 14), patients with psoriasis (n = 30), and patients with atopic dermatitis (AD; n = 16). Results Using criteria of a fold change of greater than 2 and a false discovery rate of less than 0.05, 132 differentially expressed genes were shared commonly among all ichthyoses, including many IL-17 and TNF-α–coregulated genes, which are considered hallmarks of psoriasis (defensin beta 4A, kynureninase, and vanin 3). Although striking upregulation of TH17 pathway genes (IL17F and IL36B/G) resembling that seen in patients with psoriasis was common to all patients with ichthyoses in a severity-related manner, patients with Netherton syndrome showed the greatest T-cell activation (inducible costimulator [ ICOS ]) and a broader immune phenotype with T H 1/IFN-γ, OASL, and T H 2/IL-4 receptor/IL-5 skewing, although less than seen in patients with AD (all P <.05). Ichthyoses lacked the epidermal differentiation and tight junction alterations of patients with AD (loricrin, filaggrin, and claudin 1) but showed characteristic alterations in lipid metabolism genes (ELOVL fatty acid elongase 3 and galanin), with parallel reductions in extracellular lipids and corneocyte compaction in all ichthyoses except epidermolytic ichthyosis, suggesting phenotypic variations. Transepidermal water loss, a functional barrier measure, significantly correlated with IL-17–regulated gene expression (IL17F and IL36A/IL36B/IL36G). Conclusion Similar to patients with AD and psoriasis, in whom cytokine dysregulation and barrier impairment orchestrate disease phenotypes, psoriasis-like immune dysregulation and lipid alterations characterize the ichthyoses. These data support the testing of IL-17/IL-36–targeted therapeutics for patients with ichthyosis similar to those used in patients with psoriasis. [ABSTRACT FROM AUTHOR]

Background Dupilumab is an IL-4 receptor α mAb inhibiting signaling of IL-4 and IL-13, key drivers of type 2–driven inflammation, as demonstrated by its efficacy in patients with atopic/allergic diseases. Objective This placebo-controlled, double-blind trial (NCT01979016) evaluated the efficacy, safety, and effects of dupilumab on molecular/cellular lesional and nonlesional skin phenotypes and systemic type 2 biomarkers of patients with moderate-to-severe atopic dermatitis (AD). Methods Skin biopsy specimens and blood were evaluated from 54 patients randomized 1:1 to weekly subcutaneous doses of 200 mg of dupilumab or placebo for 16 weeks. Results Dupilumab (vs placebo) significantly improved clinical signs and symptoms of AD, was well tolerated, and progressively shifted the lesional transcriptome toward a nonlesional phenotype (weeks 4–16). Mean improvements in a meta-analysis–derived AD transcriptome (genes differentially expressed between lesional and nonlesional skin) were 68.8% and 110.8% with dupilumab and −10.5% and 55.0% with placebo (weeks 4 and 16, respectively; P <.001). Dupilumab significantly reduced expression of genes involved in type 2 inflammation (IL13 , IL31 , CCL17 , CCL18 , and CCL26), epidermal hyperplasia (keratin 16 [K16] and MKi67), T cells, dendritic cells (ICOS , CD11c , and CTLA4), and T H 17/T H 22 activity (IL17A , IL-22 , and S100As) and concurrently increased expression of epidermal differentiation, barrier, and lipid metabolism genes (filaggrin [FLG] , loricrin [LOR] , claudins, and ELOVL3). Dupilumab reduced lesional epidermal thickness versus placebo (week 4, P =.001; week 16, P =.0002). Improvements in clinical and histologic measures correlated significantly with modulation of gene expression. Dupilumab also significantly suppressed type 2 serum biomarkers, including CCL17, CCL18, periostin, and total and allergen-specific IgEs. Conclusion Dupilumab-mediated inhibition of IL-4/IL-13 signaling through IL-4 receptor α blockade significantly and progressively improved disease activity, suppressed cellular/molecular cutaneous markers of inflammation and systemic measures of type 2 inflammation, and reversed AD-associated epidermal abnormalities. [ABSTRACT FROM AUTHOR]

Background Although atopic dermatitis (AD) often starts in early childhood, detailed tissue profiling of early-onset AD in children is lacking, hindering therapeutic development for this patient population with a particularly high unmet need for better treatments. Objective We sought to globally profile the skin of infants with AD compared with that of adults with AD and healthy control subjects. Methods We performed microarray, RT-PCR, and fluorescence microscopy studies in infants and young children (<5 years old) with early-onset AD (<6 months disease duration) compared with age-matched control subjects and adults with longstanding AD. Results Transcriptomic analyses revealed profound differences between pediatric patients with early-onset versus adult patients with longstanding AD in not only lesional but also nonlesional tissues. Although both patient populations harbored T H 2-centered inflammation, pediatric AD also showed significant T H 17/T H 22 skewing but lacked the T H 1 upregulation that characterizes adult AD. Pediatric AD exhibited relatively normal expression of epidermal differentiation and cornification products, which is downregulated in adults with AD. Defects in the lipid barrier (eg, ELOVL fatty acid elongase 3 [ELOVL3] and diacylglycerol o-acyltransferase 2 [DGAT2]) and tight junction regulation (eg, claudins 8 and 23) were evident in both groups. However, some lipid-associated mediators (eg, fatty acyl-CoA reductase 2 and fatty acid 2-hydroxylase) showed preferential downregulation in pediatric AD, and lipid barrier genes (FA2H and DGAT2) showed inverse correlations with transepidermal water loss, a functional measure of the epidermal barrier. Conclusions Skin samples from children and adult patients with AD share lipid metabolism and tight junction alterations, but epidermal differentiation complex defects are only present in adult AD, potentially resulting from chronic immune aberration that is not yet present in early-onset disease. [ABSTRACT FROM AUTHOR]

Abstract: Atopic dermatitis (AD) and psoriasis are inflammatory skin diseases that negatively affect patients’ quality of life. Although distinctions exist between these diseases, both are characterized by erythematous, thickened epidermal lesions that vary in intensity and affected body surface area. Early models of aetiology attributed symptoms of both diseases to cutaneous inflammation at lesion sites, but recent studies have established that activated immune mediators in the circulation drive disease severity. Activation of T helper 2 (Th2) and Th22 cells in the circulation appears to be the principal initiator of acute AD pathology, with the emergence of Th1 and Th17/interleukin (IL)‐23 pathway activation marking the transition to a chronic state. The Th17/IL‐23 pathway also has an important role in psoriasis. The role of systemic inflammation in AD and psoriasis is supported by the occurrence of non‐cutaneous comorbidities that affect patients, most of which intensify morbidity and disability associated with lesional skin. Atopic dermatitis is associated with allergic disorders consisting of the “atopic march,” whereas psoriasis is frequently accompanied by psoriatic arthritis. Patients with both disorders are at significantly higher risk of obesity, metabolic disorders, and cardiovascular diseases, all of which feature inflammatory components in their pathology models. These insights have led to novel therapeutics aimed at addressing psoriasis by targeting tumor necrosis factor‐ and Th17‐related cytokine pathways. The success of these agents in psoriasis management is driving new therapeutic approaches for moderate‐to‐severe AD, including agents targeting the Th2 and Th17/Th22 cytokine pathways. [ABSTRACT FROM AUTHOR]

Skin barrier abnormalities have been suggested to play an essential role in initiation of early atopic dermatitis (AD). Antigen penetration through a compromised barrier likely leads to increased innate immune responses, antigen-presenting cell stimulation, and priming of overt cutaneous disease. In a T H 2-promoting environment, T-cell/B-cell interactions occurring in regional lymph nodes lead to excessive IgE switch. Concurrent redistribution of memory T cells into the circulation not only leads to exacerbation of AD through T-cell skin infiltration but also spreads beyond the skin to initiate the atopic march, which includes food allergy, asthma, and allergic rhinitis. Possible primary interventions to prevent AD are focusing on improving skin barrier integrity, including supplementing barrier function with moisturizers. As for secondary prophylaxis in children with established AD, this can be stratified into prevention of disease exacerbations by using proactive approaches (with either topical corticosteroids or topical calcineurin inhibitors) in mild AD cases or the prevention of other atopic disorders that will probably mandate systemic immunosuppression in severe AD cases. [ABSTRACT FROM AUTHOR]

Background Atopic dermatitis (AD) is caused by a complex interplay between immune and barrier abnormalities. Murine models of AD are essential for preclinical assessments of new treatments. Although many models have been used to simulate AD, their transcriptomic profiles are not fully understood, and a comparison of these models with the human AD transcriptomic fingerprint is lacking. Objective We sought to evaluate the transcriptomic profiles of 6 common murine models and determine how they relate to human AD skin. Methods Transcriptomic profiling was performed by using microarrays and quantitative RT-PCR on biopsy specimens from NC/Nga, flaky tail, Flg -mutated, ovalbumin-challenged, oxazolone-challenged, and IL-23–injected mice. Gene expression data of patients with AD, psoriasis, and contact dermatitis were obtained from previous patient cohorts. Criteria of a fold change of 2 or greater and a false discovery rate of 0.05 or less were used for gene arrays. Results IL-23–injected, NC/Nga, and oxazolone-challenged mice show the largest homology with our human meta-analysis–derived AD transcriptome (37%, 18%, 17%, respectively). Similar to human AD, robust T H 1, T H 2, and also T H 17 activation are seen in IL-23–injected and NC/Nga mice, with similar but weaker inflammation in ovalbumin-challenged mice. Oxazolone-challenged mice show a T H 1-centered reaction, and flaky tail mice demonstrate a strong T H 17 polarization. Flg -mutated mice display filaggrin downregulation without significant inflammation. Conclusion No single murine model fully captures all aspects of the AD profile; instead, each model reflects different immune or barrier disease aspects. Overall, among the 6 murine models, IL-23–injected mice best simulate human AD; still, the translational focus of the investigation should determine which model is most applicable. [ABSTRACT FROM AUTHOR]

Atopic dermatitis ( AD) is the most common inflammatory skin disease, but treatment options for moderate-to-severe disease are limited. Ustekinumab is an IL-12/ IL-23p40 antagonist that suppresses Th1, Th17 and Th22 activation, commonly used for psoriasis patients. We sought to assess efficacy and safety of ustekinumab in patients with moderate-to-severe AD. In this phase II, double-blind, placebo-controlled study, 33 patients with moderate-to-severe AD were randomly assigned to either ustekinumab (n=16) or placebo (n=17), with subsequent crossover at 16 weeks, and last dose at 32 weeks. Background therapy with mild topical steroids was allowed to promote retention. Study endpoints included clinical ( SCORAD50) and biopsy-based measures of tissue structure and inflammation, using protein and gene expression studies. The ustekinumab group achieved higher SCORAD50 responses at 12, 16 (the primary endpoint) and 20 weeks compared to placebo, but the difference between groups was not significant. The AD molecular profile/transcriptome showed early robust gene modulation, with sustained further improvements until 32 weeks in the initial ustekinumab group. Distinct and more robust modulation of Th1, Th17 and Th22 but also Th2-related AD genes was seen after 4 weeks of ustekinumab treatment (i.e. MMP12, IL-22, IL-13, IFN-γ, elafin/ PI3, CXCL1 and CCL17; P<.05). Epidermal responses ( K16, terminal differentiation) showed faster (4 weeks) and long-term regulation (32 weeks) from baseline in the ustekinumab group. No severe adverse events were observed. Ustekinumab had clear clinical and molecular effects, but clinical outcomes might have been obscured by a profound 'placebo' effect, most likely due to background topical glucocorticosteroids and possibly insufficient dosing for AD. [ABSTRACT FROM AUTHOR]

Background Atopic dermatitis (AD) affects 15% to 25% of children and 4% to 7% of adults. Paradigm-shifting discoveries about AD have been based on adult biomarkers, reflecting decades of disease activity, although 85% of cases begin by 5 years. Blood phenotyping shows only T H 2 skewing in patients with early-onset pediatric AD, but alterations in early pediatric skin lesions are unknown, limiting advancement of targeted therapies. Objective We sought to characterize the early pediatric AD skin phenotype and its differences from pediatric control subjects and adults with AD. Methods Using immunohistochemistry and quantitative real-time PCR, we assessed biopsy specimens from 19 children with AD younger than 5 years within 6 months of disease onset in comparison with adults with AD or psoriasis and pediatric and adult control subjects. Results In lesional skin children showed comparable or greater epidermal hyperplasia (thickness and keratin 16) and cellular infiltration (CD3 + , CD11c + , and FcεRI + ) than adults with AD. Similar to adults, strong activation of the T H 2 (IL-13, IL-31, and CCL17) and T H 22 (IL-22 and S100As) axes and some T H 1 skewing (IFN-γ and CXCL10) were present. Children showed significantly higher induction of T H 17-related cytokines and antimicrobials (IL-17A, IL-19, CCL20, LL37, and peptidase inhibitor 3/elafin), T H 9/IL-9, IL-33, and innate markers (IL-8) than adults ( P < .02). Despite the characteristic downregulation in adult patients with AD, filaggrin expression was similar in children with AD and healthy children. Nonlesional skin in pediatric patients with AD showed higher levels of inflammation (particularly IL-17A and the related molecules IL-19 and LL37) and epidermal proliferation (keratin 16 and S100As) markers ( P < .001). Conclusion The skin phenotype of new-onset pediatric AD is substantially different from that of adult AD. Although excess T H 2 activation characterizes both, T H 9 and T H 17 are highly activated at disease initiation. Increases in IL-19 levels might link T H 2 and T H 17 activation. [ABSTRACT FROM AUTHOR]

Background Topical glucocorticosteroids are considered an efficient treatment option for atopic dermatitis (AD), but a global assessment of glucocorticosteroid responses on key disease circuits upon weeks to months of treatment is currently lacking. Objective We sought to assess short (4 weeks) and long-term (16 weeks) application of topical glucocorticosteroids on AD skin and define response biomarkers. Methods The effects of triamcinolone acetonide cream 0.025% were assessed based on gene expression and immunohistochemistry studies at baseline, 4 weeks, and 16 weeks in biopsy specimens from 15 patients with moderate-to-severe AD. Results At 16 weeks, only 3 patients were clinical responders (by using SCORAD50 criteria), but 6 patients qualified as responders based on histologic criteria. Baseline characteristics indicated more severe disease in nonresponders. While 3 of 15 patients experienced only transient benefit after 4 weeks, others showed progressive improvements toward 16 weeks. Topical glucocorticosteroid use in patients with AD resulted in improvements of the AD genomic signature of 25.6% at 4 weeks and 71.8% at 16 weeks, respectively, and even 123.9% in the histologic responder group. Cytokines (IL-12p40, IL-13, IL-22, CCL17, CCL18, peptidase inhibitor 3 [PI3]/elafin, and S100As) showed consistent decreases from baseline toward 16 weeks with corresponding improvements in epidermal disease hallmarks (keratin 16 and loricrin) in lesional skin from responders ( P < .05). Nonresponders largely showed lesser/nonsignificant reductions in key inflammatory and barrier markers (keratin 16, IL-13, IL-22, CCL17, CCL18, PI3/elafin, S100As, and loricrin). The combination of IL-21 and IFN-γ baseline expression closely predicted individual clinical glucocorticosteroid responses at 16 weeks of treatment. Conclusion Our study indicates that even low-potency glucocorticosteroids can broadly affect immune and barrier responses in patients with moderate-to-severe AD, associating higher baseline severity with increased steroid resistance in patients with AD. [ABSTRACT FROM AUTHOR]

Diphencyprone (DPCP) is a hapten that induces delayed-type hypersensitivity (DTH) reactions. MicroRNAs (miRNAs) are short non-coding RNAs that negatively regulate gene expression and have been implicated in various inflammatory skin diseases, but their role in DTH reactions is not well understood. We generated global miRNA expression profiles (using next-generation sequencing) of DPCP reactions in skin of seven healthy volunteers at 3, 14 and 120 days after challenge. Compared to placebo-treated sites, DPCP-challenged skin at 3 days (peak inflammation) had 127 miRNAs significantly deregulated. At 14 days (during resolution of inflammation), 43 miRNAs were deregulated and, at 120 days (when inflammation had completely resolved), six miRNAs were upregulated. While some miRNAs have been observed in psoriasis or atopic dermatitis, most of the deregulated miRNAs have not yet been studied in the context of skin biology or immunology. Across the three time points studied, many but not all miRNAs were uniquely expressed. As various miRNAs may influence T cell activation, this may indicate that the miRNAs exclusively expressed at different time points function to promote or resolve skin inflammation, and therefore, may inform on the paradoxical ability of DPCP to treat both autoimmune conditions (alopecia areata) and conditions of ineffective immunity (melanoma). [ABSTRACT FROM AUTHOR]

Background Atopic dermatitis (AD) shows very high prevalence in Asia, with a large unmet need for effective therapeutics. Direct comparisons between European American (EA) and Asian patients with AD are unavailable, but earlier blood studies detected increased IL-17 + –producing cell counts in Asian patients with AD. Objective We sought to characterize the Asian AD skin phenotype and compare it with the EA AD skin phenotype. Methods We performed genomic profiling (real-time PCR) and immunohistochemistry on lesional and nonlesional biopsy specimens from 52 patients with AD (25 EAs and 27 Asians), 10 patients with psoriasis (all EAs), and 27 healthy subjects (12 EAs and 15 Asians). Results Although disease severity/SCORAD scores were similar between the AD groups (58.0 vs 56.7, P = .77), greater acanthosis, higher Ki67 counts, and frequent parakeratosis were characteristics of lesional epidermis from Asian patients with AD ( P < .05). Most (24/27) Asian patients had high IgE levels. A principal component analysis using real-time PCR data clustered the Asian AD phenotype between the EA AD and psoriasis phenotypes. T H 2 skewing characterized both Asian and EA patients with AD but not patients with psoriasis. Significantly higher T H 17 and T H 22 ( IL17A, IL19 , and S100A12 in lesional and IL-22 in nonlesional skin; P < .05) and lower T H 1/interferon ( CXCL9, CXCL10, MX1 , and IFNG in nonlesional skin; P < .05) gene induction typified AD skin in Asian patients. Conclusion The Asian AD phenotype presents (even in the presence of increased IgE levels) a blended phenotype between that of EA patients with AD and those with psoriasis, including increased hyperplasia, parakeratosis, higher T H 17 activation, and a strong T H 2 component. The relative pathogenic contributions of the T H 17 and T H 2 axes in creating the Asian AD phenotype need to be tested in future clinical trials with appropriate targeted therapeutics. [ABSTRACT FROM AUTHOR]

Background Alopecia areata (AA) is a common T cell–mediated disorder with limited therapeutics. A molecular profile of cytokine pathways in AA tissues is lacking. Although studies have focused on T H 1/IFN-γ responses, several observations support a shared genetic background between AA and atopy. Objective We sought to define the AA scalp transcriptome and associated biomarkers with comparisons with atopic dermatitis (AD) and psoriasis. Methods We performed microarray and RT-PCR profiling of 27 lesional and 17 nonlesional scalp samples from patients with AA for comparison with normal scalp samples (n = 6). AA gene expression was also compared with samples from patients with lesional or nonlesional AD and those with psoriasis. A fold change of greater than 1.5 and a false discovery rate of less than 0.05 were used for differentially expressed genes (DEGs). Results We established the AA transcriptomes (lesional vs nonlesional: 734 DEGs [297 upregulated and 437 downregulated]; lesional vs normal: 4230 DEGs [1980 upregulated and 2250 downregulated]), including many upregulated immune and downregulated hair keratin genes. Equally impressive as upregulation in T H 1/interferon markers ( IFNG and CXCL10/CXCL9 ) were those noted in T H 2 ( IL13 , CCL18, CCL26 , thymic stromal lymphopoietin, and periostin), T H 9/IL-9, IL-23 (p40 and p19), and IL-16 mediators (all P < .05). There were no increases in T H 17/T H 22 markers. Hair keratin (KRT) expressions (ie, KRT86 and KRT85 ) were significantly suppressed in lesional skin. Greater scalp involvement (>25%) was associated with greater immune and keratin dysregulation and larger abnormalities in nonlesional scalp samples (ie, CXCL10 and KRT85 ). Conclusions Our data associate the AA signature with T H 2, T H 1, IL-23, and IL-9/T H 9 cytokine activation, suggesting consideration of anti-T H 2, anti-T H 1, and anti–IL-23 targeting strategies. Similar to psoriasis and AD, clinical trials with selective antagonists are required to dissect key pathogenic pathways. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) is a common inflammatory skin disease with limited treatment options. Several microarray experiments have been conducted on lesional/LS and non-lesional/NL AD skin to develop a genomic disease phenotype. Although these experiments have shed light on disease pathology, inter-study comparisons reveal large differences in resulting sets of differentially expressed genes (DEGs), limiting the utility of direct comparisons across studies. Methods: We carried out a meta-analysis combining 4 published AD datasets to define a robust disease profile, termed meta-analysis derived AD (MADAD) transcriptome. Results: This transcriptome enriches key AD pathways more than the individual studies, and associates AD with novel pathways, such as atherosclerosis signaling (IL-37, selectin E/SELE). We identified wide lipid abnormalities and, for the first time in vivo, correlated Th2 immune activation with downregulation of key epidermal lipids (FA2H, FAR2, ELOVL3), emphasizing the role of cytokines on the barrier disruption in AD. Key AD "classifier genes" discriminate lesional from nonlesional skin, and may evaluate therapeutic responses. Conclusions: Our meta-analysis provides novel and powerful insights into AD disease pathology, and reinforces the concept of AD as a systemic disease. [ABSTRACT FROM AUTHOR]

Background Genomic profiling of lesional and nonlesional skin of patients with atopic dermatitis (AD) using microarrays has led to increased understanding of AD and identification of novel therapeutic targets. However, the limitations of microarrays might decrease detection of AD genes. These limitations might be lessened with next-generation RNA sequencing (RNA-seq). Objective We sought to define the lesional AD transcriptome using RNA-seq and compare it using microarrays performed on the same cohort. Methods RNA-seq and microarrays were performed to identify differentially expressed genes (criteria: fold change, ≥2.0; false discovery rate ≤0.05) in lesional versus nonlesional skin from 18 patients with moderate-to-severe AD, with real-time PCR (RT-PCR) and immunohistochemistry used for validation. Results Both platforms showed robust disease transcriptomes and correlated well with RT-PCR. The common AD transcriptome identified by using both techniques contained 217 genes, including inflammatory ( S100A8/A9/A12, CXCL1 , and 2′-5′-oligoadenylate synthetase-like [ OASL ]) and barrier ( MKi67 , keratin 16 [ K16 ], and claudin 8 [ CLDN8 ]) AD-related genes. Although fold change estimates determined by using RNA-seq showed somewhat better agreement with RT-PCR (intraclass correlation coefficient, 0.57 and 0.70 for microarrays and RNA-seq vs RT-PCR, respectively), bias was not eliminated. Among genes uniquely identified by using RNA-seq were triggering receptor expressed on myeloid cells 1 (TREM-1) signaling (eg, CCL2 , CCL3 , and single immunoglobulin domain IL1R1 related [ SIGIRR ]) and IL-36 isoform genes. TREM-1 is a surface receptor implicated in innate and adaptive immunity that amplifies infection-related inflammation. Conclusions This is the first report of a lesional AD phenotype using RNA-seq and the first direct comparison between platforms in this disease. Both platforms robustly characterize the AD transcriptome. Through RNA-seq, we unraveled novel disease pathology, including increased expression of the novel TREM-1 pathway and the IL-36 cytokine in patients with AD. [ABSTRACT FROM AUTHOR]

Background Atopic dermatitis (AD) is the most common inflammatory disease. The prevalence of allergic contact dermatitis to allergens (eg, fragrance) is higher in patients with AD, despite a trend toward weaker clinical allergic contact dermatitis reactions. The role of the AD skin phenotype in modulating allergic sensitization to common sensitizers has not been evaluated. Objective We sought to investigate whether patients with AD have altered tissue immune responses on allergen challenge. Methods Gene expression and immunohistochemistry studies were performed on biopsy specimens from 10 patients with AD and 14 patients without AD patch tested with common contact allergens (nickel, fragrance, and rubber). Results Although 1085 differentially expressed genes (DEGs) were commonly modulated in patch-tested skin from patients with AD and patients without AD versus control skin, 1185 DEGs were uniquely altered in skin from patients without AD, and only 246 DEGs were altered in skin from patients with AD. Although many inflammatory products (ie, matrix metalloproteinase 12/matrix metalloproteinase 1/S100A9) were upregulated in both groups, higher-magnitude changes and upregulation of interferon responses were evident only in the non-AD group. Stratification by allergen showed decreased expression of immune, T H 1-subset, and T H 2-subset genes in nickel-related AD responses, with increased T H 17/IL-23 skewing. Rubber/fragrance showed similar trends of lesser magnitude. Negative regulators showed higher expression in patients with AD. Conclusions Through contact sensitization, our study offers new insights into AD. Allergic immune reactions were globally attenuated and differentially polarized in patients with AD, with significant decreases in levels of T H 1 products, some increases in levels of T H 17 products, and inconsistent upregulation in levels of T H 2 products. The overall hyporesponsiveness in skin from patients with background AD might be explained by baseline immune abnormalities, such as increased T H 2, T H 17, and negative regulator levels compared with those seen in non-AD skin. [ABSTRACT FROM AUTHOR]

Psoriasis and atopic dermatitis (AD) are common inflammatory skin diseases characterized by immune-mediated inflammation and abnormal keratinocyte differentiation. Although T-cell infiltration characterizes both diseases, T-cell polarization differs. Psoriasis is currently the best model for translational medicine because many targeted therapeutics have been developed and testing of targeted therapeutics has cemented psoriasis as IL-23/T H 17 polarized. In patients with AD, although therapeutic development is approximately a decade behind that in patients with psoriasis, there is now active development and testing of targeted therapeutics against various immune axes (T H 2, T H 22, and IL-23/T H 17). These clinical trials and subsequent molecular analyses using human samples will be able to clarify the relative roles of polar cytokines in patients with AD. [ABSTRACT FROM AUTHOR]

Background The molecular signature of atopic dermatitis (AD) lesions is associated with T H 2 and T H 22 activation and epidermal alterations. However, the epidermal and dermal AD transcriptomes and their respective contributions to abnormalities in respective immune and barrier phenotypes are unknown. Objective We sought to establish the genomic profile of the epidermal and dermal compartments of lesional and nonlesional AD skin compared with normal skin. Methods Laser capture microdissection was performed to separate the epidermis and dermis of lesional and nonlesional skin from patients with AD and normal skin from healthy volunteers, followed by gene expression (microarrays and real-time PCR) and immunostaining studies. Results Our study identified novel immune and barrier genes, including the IL-34 cytokine and claudins 4 and 8, and showed increased detection of key AD genes usually undetectable on arrays (ie, IL22 , thymic stromal lymphopoietin [TSLP] , CCL22 , and CCL26 ). Overall, the combined epidermal and dermal transcriptomes enlarged the AD transcriptome, adding 674 upregulated and 405 downregulated differentially expressed genes between lesional and nonlesional skin to the AD transcriptome. We were also able to localize individual transcripts as primarily epidermal (defensin, beta 4A [DEFB4A] ) or dermal ( IL22 , cytotoxic T-lymphocyte antigen 4 [CTLA4] , and CCR7 ) and link their expressions to possible cellular sources. Conclusions This is the first report that establishes robust epidermal and dermal genomic signatures of lesional and nonlesional AD skin and normal skin compared with whole tissues. These data establish the utility of laser capture microdissection to separate different compartments and cellular subsets in patients with AD, allowing localization of key barrier or immune molecules and enabling detection of gene products usually not detected on arrays. [ABSTRACT FROM AUTHOR]

Background Severe atopic dermatitis (AD) has a high unmet need for effective and safe therapeutics. In early-phase trials, dupilumab, a fully human mAb targeting IL-4 receptor α, markedly improved disease activity, but the effect of IL-4/IL-13 blockade on AD at the molecular level has not been characterized. Objectives We sought to evaluate dupilumab modulation of the AD molecular signature. Methods We performed transcriptomic analyses of pretreatment and posttreatment skin biopsy specimens from patients with moderate-to-severe AD treated weekly with 150 or 300 mg of dupilumab or placebo. Results Exacerbation of the AD transcriptome was observed in placebo-treated patients. Dupilumab improved the AD signature in a dose-dependent manner. Expression of genes upregulated in AD lesions decreased in patients treated with dupilumab by 26% (95% CI, 21% to 32%) and 65% (95% CI, 60% to 71%) for treatment with 150 and 300 mg, respectively. Genes downregulated in AD lesions increased by 21% (95% CI, 16% to 27%) and 32% (95% CI, 26% to 37%) with dupilumab (150 and 300 mg, respectively). The molecular changes paralleled improvements in clinical scores. A dupilumab treatment signature of 821 probes (>2-fold change, P < .05) significantly modulated in the 300-mg dupilumab group at week 4 compared with baseline was identified in this sample set. Significant ( P < .05) decreases in mRNA expression of genes related to hyperplasia ( K16 and MKI67 ), T cells, and dendritic cells ( CD1b and CD1c ) and potent inhibition of T H 2-associated chemokines ( CCL17 , CCL18 , CCL22 , and CCL26 ) were noted without significant modulation of T H 1-associated genes (IFNG) . Conclusions This is the first report showing rapid improvement of the AD molecular signature with targeted anti–IL-4 receptor α therapy. These data suggest that IL-4 and IL-13 drive a complex, T H 2-centered inflammatory axis in patients with AD. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) is classified as extrinsic and intrinsic, representing approximately 80% and 20% of patients with the disease, respectively. Although sharing a similar clinical phenotype, only extrinsic AD is characterized by high serum IgE levels. Because most patients with AD exhibit high IgE levels, an “allergic”/IgE-mediated disease pathogenesis was hypothesized. However, current models associate AD with T-cell activation, particularly TH2/TH22 polarization, and epidermal barrier defects. Objective: We sought to define whether both variants share a common pathogenesis. Methods: We stratified 51 patients with severe AD into extrinsic AD (n = 42) and intrinsic AD (n = 9) groups (with similar mean disease activity/SCORAD scores) and analyzed the molecular and cellular skin pathology of lesional and nonlesional intrinsic AD and extrinsic AD by using gene expression (real-time PCR) and immunohistochemistry. Results: A significant correlation between IgE levels and SCORAD scores (r = 0.76, P < 10−5) was found only in patients with extrinsic AD. Marked infiltrates of T cells and dendritic cells and corresponding epidermal alterations (keratin 16, Mki67, and S100A7/A8/A9) defined lesional skin of patients with both variants. However, higher activation of all inflammatory axes (including TH2) was detected in patients with intrinsic AD, particularly TH17 and TH22 cytokines. Positive correlations between TH17-related molecules and SCORAD scores were only found in patients with intrinsic AD, whereas only patients with extrinsic AD showed positive correlations between SCORAD scores and TH2 cytokine (IL-4 and IL-5) levels and negative correlations with differentiation products (loricrin and periplakin). Conclusions: Although differences in TH17 and TH22 activation exist between patients with intrinsic AD and those with extrinsic AD, we identified common disease-defining features of T-cell activation, production of polarized cytokines, and keratinocyte responses to immune products. Our data indicate that a TH2 bias is not the sole cause of high IgE levels in patients with extrinsic AD, with important implications for similar therapeutic interventions. [Copyright &y& Elsevier]

Atopic dermatitis (AD), as well as irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD), are common skin diseases. These diseases are characterized by skin inflammation mediated by activated innate immunity or acquired immune mechanisms. Although AD, ICD, and ACD can be encountered in pure forms by allergists and dermatologists, patients with AD often present with increased frequency of ICD and ACD. Although a disturbed barrier alone could potentiate immune reactivity in patients with AD through increased antigen penetration, additional immune mechanisms might explain the increased susceptibility of atopic patients to ICD and ACD. This review discusses cellular pathways associated with increased skin inflammation in all 3 conditions and presents mechanisms that might contribute to the increased rate of ICD and ACD in patients with AD. [Copyright &y& Elsevier]

Background: Atopic dermatitis (AD) is a common disease with an increasing prevalence. The primary pathogenesis of the disease is still elusive, resulting in the lack of specific treatments. AD is currently considered a biphasic disease, with TH2 predominating in acute disease and a switch to TH1 characterizing chronic disease. Elucidation of the molecular factors that participate in the onset of new lesions and maintenance of chronic disease is critical for the development of targeted therapeutics. Objectives: We sought to characterize the mechanisms underlying the onset and maintenance of AD. Methods: We investigated intrapersonal sets of transcriptomes from nonlesional skin and acute and chronic lesions of 10 patients with AD through genomic, molecular, and cellular profiling. Results: Our study associated the onset of acute lesions with a striking increase in a subset of terminal differentiation proteins, specifically the cytokine-modulated S100A7, S100A8, and S100A9. Acute disease was also associated with significant increases in gene expression levels of major TH22 and TH2 cytokines and smaller increases in IL-17 levels. A lesser induction of TH1-associated genes was detected in acute disease, although some were significantly upregulated in chronic disease. Further significant intensification of major TH22 and TH2 cytokines was observed between acute and chronic lesions. Conclusions: Our data identified increased S100A7, S100A8, and S100A9 gene expression with AD initiation and concomitant activation of TH2 and TH22 cytokines. Our findings support a model of progressive activation of TH2 and TH22 immune axes from the acute to chronic phases, expanding the prevailing view of pathogenesis with important therapeutic implications. [Copyright &y& Elsevier]

Atopic dermatitis (AD) and psoriasis are among the most common inflammatory skin diseases. In the first part of this 2-part review, we discussed the similarities and differences between AD and psoriasis with respect to clinical features and pathology. The diseases are characterized by infiltration of skin lesions by large numbers of inflammatory cells; the second part of this review focuses on immune cell subsets that distinguish each disease and the therapeutic strategies that might be used or developed based on this information. We discuss the interactions among different populations of immune cells that ultimately create the complex inflammatory phenotype of AD and compare these with psoriasis. Therapeutic strategies have been developed for psoriasis based on the cytokine network that promotes inflammation in this disease. Antibodies against IL-12 and IL-23p40 antibody and antagonists of TNF are used to treat patients with psoriasis, and studies are underway to test specific antagonists of IL-23, IL-17, IL-17 receptor, IL-20, and IL-22. We discuss how these therapeutic approaches might be applied to AD. [ABSTRACT FROM AUTHOR]

Atopic dermatitis and psoriasis are 2 of the most common inflammatory skin diseases. They are similar in that they are complex inherited diseases involving genes that encode immune components and structural proteins that regulate differentiation of epidermal cells. Each disease is characterized by proliferation of epidermal keratinocytes and abnormal cornification or terminal differentiation in the epidermis; skin lesions contain immune infiltrates of T cells, dendritic cells, and other types of leukocytes. We review similarities between the diseases and differences in epidermal barrier defects and immune cells. We also propose mechanisms of pathogenesis based on differences in the balance of immune cell subsets that could cause the phenotypes that distinguish these diseases. The first part of this 2-part review focuses on the clinical and pathologic features of the diseases; the second part discusses differences in immune cell subsets between atopic dermatitis and psoriasis and recent therapeutic strategies. [ABSTRACT FROM AUTHOR]

IL-22 is a cytokine that acts mainly on epithelial cells. In the skin, it mediates keratinocyte proliferation and epidermal hyperplasia and is thought to play a central role in inflammatory diseases with marked epidermal acanthosis, such as psoriasis. Although 11-22 was initially considered a Th17 cytokine, increasing evidence suggests that T helper cells can produce lL-22 even without 11-17 expression. In addition, we have shown the existence of this unique IL-22-producing T cell in normal skin and in the skin of psoriasis and atopic dermatitis patients. In the present study, we investigated the ability of cutaneous resident dendritic cells (DCs) to differentiate IL-22-producing cells. Using FACS, we isolated Langerhans cells (LCs; HLA-DR+CD207+ cells) and dermal DCs (HLA-DR+CD11c+BDCA-1+ cells)from normal human epidermis and dermis, respectively. Both LCs and dermal DCs significantly induced IL-22-producing CD4+ and CD8+ T cells from peripheral blood I cells and naive CD4+ T cells in mixed leukocyte reactions. ICs were more powerful in the induction of IL-22-producing cells than dermal DCs. Moreover, in vitro-generated LC-type DCs induced IL-22-producing cells more efficiently than monocyte-derived DCs. The induced IL-22 production was more correlated with IFN-γ than IL-17. Surprisingly, the majority of IL-22-producing cells induced by LCs and dermal DCs lacked the expression of IL-17, IFN-γ, and lL-4. Thus, LCs and dermal DCs preferentially induced helper T cells to produce only IL-22, possibly "Th22" cells. Our data indicate that cutaneous DCs, especially LCs, may control the generation of distinct IL-22 producing Th22 cells infiltrating into the skin. [ABSTRACT FROM AUTHOR]

Background: Atopic dermatitis (AD) and psoriasis represent contrasting poles of the TH1 versus TH2 paradigm. Both diseases have been associated with increased numbers of dendritic cells (DCs) in the skin, but the similarities and differences in DC populations need to be established. Objective: We aimed to characterize the specific DC subsets, as well as chemokine and cytokine environment in chronic AD compared with psoriasis. Methods: Skin biopsies were obtained from patients with acute exacerbation of chronic AD (n = 18), psoriasis (n = 15), and healthy volunteers (n = 15) for microarray analysis, RT-PCR, immunohistochemistry, and double-label immunofluorescence. Results: Myeloid DCs upregulate CCL17 and CCL18 in AD, as opposed to TNF-α and inducible nitric oxide synthase (iNOS) in psoriasis. In our study, we identified cells phenotypically identical to the inflammatory dendritic epidermal cells in the dermis in both diseases, although to a lesser extent in psoriasis. We found substantially higher numbers of dermal CCL22 producing plasmacytoid DCs in AD. The thymic stromal lymphopoietin receptor showed significantly higher expression in AD, whereas the thymic stromal lymphopoietin ligand was upregulated more in psoriasis. Conclusion: There are major differences in myeloid and plasmacytoid subsets of cutaneous DCs and the chemokine/cytokine environment between AD and psoriasis. Distinct subsets within the CD11c+ population may influence polarization through the production of regulatory mediators, including iNOS, TNF, CCL17, and CCL18. Plasmacytoid DCs may also influence TH2 polarization, having a more important role in AD than previously appreciated. Clinical implications: Dermal inflammatory dendritic cells in AD and TNF and iNOS–producing DCs in psoriasis, and/or their regulatory products, may be potential targets for future therapeutic interventions. [Copyright &y& Elsevier]