Expression of barrier proteins in the skin lesions and inflammatory cytokines in peripheral blood mononuclear cells of atopic dogs.

Atopic dermatitis (AD) is one of the most common skin diseases of dogs. Defects in the skin barrier and overproduction of inflammatory cytokines may be the pathogenesis of canine AD. Therefore, the present study was aimed to quantify the gene expression of certain skin barrier proteins and inflammatory cytokines in dogs with AD. Eleven dogs with AD and three healthy dogs were included in the present study. The skin barrier proteins, namely Filaggrin (FLG) and Involucrin (IVL), gene expression was quantified by Real-time PCR in the lesional skin tissues of the atopic dogs and normal skin of the healthy dogs. In addition to the skin proteins, the gene expressions of the interleukin (IL)-13, IL-31, and tumour necrosis factor (TNF)-α were also quantified in the peripheral blood mononuclear cells (PBMCs) of these dogs. Compared to the healthy dogs, significantly higher (P ≤ 0.01) FLG gene expression and significantly (P ≤ 0.05) lower expression of the IVL gene were quantified in the skin of atopic dogs. Further, the dogs with AD revealed significantly higher expression of TNF-α (P ≤ 0.01), IL-31 (P ≤ 0.05), and IL-13 (P ≤ 0.05) as compared to the healthy dogs. The findings of our present study evidently suggest significantly increased and decreased expressions of FLG and IVL genes, respectively, which may be responsible for disruption of the skin barrier in dogs with AD. While, the over-expressions of TNF-α, IL-31, and IL-13 genes might be attributed to the clinical pathology and manifestations of AD in dogs. However, further studies are warranted to substantiate our hypothesis about pathogenesis and clinical manifestation of AD in dogs by including a large number of animals.

Filaggrin expression via immunohistochemistry in basal cell carcinoma and squamous cell carcinoma.

BACKGROUND: Filaggrin is a protein integral to the structure and function of the epidermis. Filaggrin (FLG) loss-of-function (LOF) mutations are common and increase the risk of developing atopic dermatitis (AD) and ichthyosis vulgaris (IV). Epidemiologic data suggest a link between skin cancer and AD. We examined if FLG staining pattern can be used to characterize cutaneous squamous cell carcinomas (SCC), basal cell carcinomas (BCC), and reactive squamous epithelium. METHODS: Tissue microarrays (TMAs) were created from 196 cases of formalin-fixed paraffin-embedded (FFPE) SCC and 144 BCC cases. TMAs and sections of reactive squamous epithelium were stained with optimized anti-FLG antibody and evaluated for FLG expression (normal, abnormal, or negative). RESULTS: FLG was absent in poorly differentiated (PD) compared to well-differentiated (WD) SCC (P < .0001) and moderately-differentiated (MD) (P = .0231) SCC, and in MD compared to WD SCC (P = .0099). Abnormal staining was significantly increased in PD compared to WD cases (P = .0039) and in MD compared to WD cases (P = .0006). Most BCC did not exhibit FLG expression (P < .05). Reactive squamous epithelium demonstrated normal, but exaggerated FLG expression. CONCLUSIONS: Our findings demonstrate the differences in FLG expression patterns in types of keratinocyte carcinomas and their mimickers.

Epidermal mammalian target of rapamycin complex 2 controls lipid synthesis and filaggrin processing in epidermal barrier formation.

BACKGROUND: Perturbation of epidermal barrier formation will profoundly compromise overall skin function, leading to a dry and scaly, ichthyosis-like skin phenotype that is the hallmark of a broad range of skin diseases, including ichthyosis, atopic dermatitis, and a multitude of clinical eczema variants. An overarching molecular mechanism that orchestrates the multitude of factors controlling epidermal barrier formation and homeostasis remains to be elucidated. OBJECTIVE: Here we highlight a specific role of mammalian target of rapamycin complex 2 (mTORC2) signaling in epidermal barrier formation. METHODS: Epidermal mTORC2 signaling was specifically disrupted by deleting rapamycin-insensitive companion of target of rapamycin (Rictor), encoding an essential subunit of mTORC2 in mouse epidermis (epidermis-specific homozygous Rictor deletion [RicEKO] mice). Epidermal structure and barrier function were investigated through a combination of gene expression, biochemical, morphological and functional analysis in RicEKO and control mice. RESULTS: RicEKO newborns displayed an ichthyosis-like phenotype characterized by dysregulated epidermal de novo lipid synthesis, altered lipid lamellae structure, and aberrant filaggrin (FLG) processing. Despite a compensatory transcriptional epidermal repair response, the protective epidermal function was impaired in RicEKO mice, as revealed by increased transepidermal water loss, enhanced corneocyte fragility, decreased dendritic epidermal T cells, and an exaggerated percutaneous immune response. Restoration of Akt-Ser473 phosphorylation in mTORC2-deficient keratinocytes through expression of constitutive Akt rescued FLG processing. CONCLUSION: Our findings reveal a critical metabolic signaling relay of barrier formation in which epidermal mTORC2 activity controls FLG processing and de novo epidermal lipid synthesis during cornification. Our findings provide novel mechanistic insights into epidermal barrier formation and could open up new therapeutic opportunities to restore defective epidermal barrier conditions.

Rhabdomyosarcoma and Wilms tumors contain a subpopulation of noggin producing, myogenic cells immunoreactive for lens beaded filament proteins.

Myo/Nog cells are identified by their expression of the skeletal muscle specific transcription factor MyoD and the bone morphogenetic protein inhibitor noggin, and binding of the G8 monoclonal antibody. Their release of noggin is critical for morphogenesis and skeletal myogenesis. In the adult, Myo/Nog cells are present in normal tissues, wounds and skin tumors. Myo/Nog cells in the lens give rise to myofibroblasts that synthesize skeletal muscle proteins. The purpose of this study was to screen human lens tissue, rhabdomyosarcoma cell lines, and tissue sections from rhabdomyosarcoma, Wilms and tumors lacking features of skeletal muscle for co-localization of antibodies to Myo/Nog cell markers and the lens beaded filament proteins filensin and CP49. Immunofluorescence localization experiments revealed that Myo/Nog cells of the lens bind antibodies to beaded filament proteins. Co-localization of antibodies to G8, noggin, filensin and CP49 was observed in most RC13 and a subpopulation of RD human rhabdomyosarcoma cell lines. Western blotting with beaded filament antibodies revealed bands of similar molecular weights in RC13 and murine lens cells. Human alveolar, embryonal, pleomorphic and spindle cell rhabdomyosarcomas and Wilms tumors contained a subpopulation of cells immunoreactive for G8, noggin, MyoD and beaded filaments. G8 was also co-localized with filensin mRNA. Staining for beaded filament proteins was not detected in G8 positive cells in leiomyosarcomas, squamous and basal cell carcinomas, syringocarciomas and malignant melanomas. Lens beaded filament proteins were thought to be present only in the lens. Myo/Nog-like cells immunoreactive for beaded filaments may be diagnostic of tumors related to the skeletal muscle lineage.

Immunome and immune complex-forming components of Brugia malayi identified by microfilaremic human sera.

Adult Brugia malayi proteins with high potential as epidemiological markers, diagnostic and therapeutic targets, and/or vaccine candidates were revealed by using microfilaremic human sera and an immunoproteomic approach. They were HSP70, cytoplasmic intermediate filament protein, independent phosphoglycerate mutase, and enolase. Brugia malayi microfilaria-specific proteins that formed circulating immune complexes (ICs) were investigated. The IC-forming proteins were orthologues of hypothetical protein Bm1_12480, Pao retrotransposon peptidase family protein, uncoordinated protein 44, NAD-binding domain containing protein of the UDP-glucose/GDP-mannose dehydrogenase family which contained ankyrin repeat region, ZU5 domain with C-terminal death domain, C2 domain containing protein, and FLJ90013 protein of the eukaryotic membrane protein family. Antibodies to these proteins were not free in the microfilaremic sera, raising the possible role of the IC-forming proteins in an immune evasion mechanism of the circulating microfilariae to avoid antibody-mediated-host immunity. Moreover, detection of these ICs should be able to replace the inconvenient night blood sampling for microfilaria in an evaluation of efficacy of anti-microfilarial agents.

Atopic dermatitis endotypes and implications for targeted therapeutics.

Recent research advancements indicate that atopic dermatitis (AD) is a complex disease characterized by different subtypes/phenotypes based on age, disease chronicity, ethnicity, filaggrin and IgE status, and underlying molecular mechanisms/endotypes. This heterogeneity advocates against the traditional "one-size-fits-all" therapeutic approaches still used to manage AD. Precision medicine approaches, striving for targeted, tailored, endotype-driven disease prevention and treatment, rely on detailed definitions of the disease's variability across different phenotypes. Studies have shown that AD harbors different endotypes across different age groups and ethnicities and according to IgE levels and filaggrin mutation status. These include European American versus Asian patients, children versus adults, intrinsic versus extrinsic (IgE status) disease, and patients with and without filaggrin mutations. Therapies targeting different cytokine axes and other mechanisms involved in disease pathogenesis, which are currently being tested for patients with AD across the disease spectrum, will expand our ability to dissect the relative contribution of each of these pathways to disease perpetuation.

Refined Immunochemical Characterization in Healthy Dog Skin of the Epidermal Cornification Proteins, Filaggrin, and Corneodesmosin.

Filaggrin (FLG) and corneodesmosin (CDSN) are two key proteins of the human epidermis. FLG loss-of-function mutations are the strongest genetic risk factors for human atopic dermatitis. Studies of the epidermal distribution of canine FLG and CDSN are limited. Our aim was to better characterize the distribution of FLG and CDSN in canine skin. Using immunohistochemistry on beagle skin, we screened a series of monoclonal antibodies (mAbs) specific for human FLG and CDSN. The cross-reactive mAbs were further used using immunoelectron microscopy and Western blotting. The structure of canine CDSN and FLG was determined using publicly available databases. In the epidermis, four anti-FLG mAbs stained keratohyalin granules in the granular keratinocytes and corneocyte matrix of the lower cornified layer. In urea-extracts of dog epidermis, several bands corresponding to proFLG and FLG monomers were detected. One anti-CDSN mAb stained the cytoplasm of granular keratinocytes and cells of both the inner root sheath and medulla of hair follicles. Dog CDSN was located in lamellar bodies, in the extracellular parts of desmosomes and in corneodesmosomes. A protein of 52 kDa was immunodetected. Genomic DNA analysis revealed that the amino acid sequence and structure of canine and human CDSN were highly similar.

Autoantibody and metalloproteinase activity in early arthritis.

OBJECTIVES: The aim of the study was to evaluate the frequency of anti-mutated citrullinated vimentin antibodies (a-Sa), anti-citrullinated α-enolase peptide 1 antibodies (a-CEP-1), anti-filaggrin antibodies (AFAs), heterogeneous nuclear ribonucleoprotein compies/anti-RA33-antibodies (a-hnRNP/RA33), anti-carbamylated protein antibodies (a-CarP), and metalloproteinase (MMPs) activity in patients with early inflammatory arthritis (EIA). METHODS: Seventy-four patients with EIA: 51 diagnosed with RA (rheumatoid arthritis) and 23 with UA (undifferentiated arthritis), and 20 healthy volunteers were enrolled to the study. Inflammatory markers, rheumatoid factor (RF), and antibodies mentioned above were assessed in all patients. RESULTS: In the EIA group, we observed significantly higher concentration of a-CEP-1 (65.8 ± 111.6 RU/mL) than in controls (2.0 ± 0.0 RU/mL). In RF(+) RA patients, we observed higher concentration of a-Sa and a-CEP-1 than in other groups. A-Sa were positive in 69% of RF(+) RA, 37% of RF(-) RA, 26% of UA patients and in 10% of controls. A-CEP-1 were positive in 77% of RF(+) RA patients, in 56% of RF(-) RA patients, in 8.7% of UA patients, but they were negative in controls. In patients with RF(+) RA, positive a-CarP were present statistically significantly more often than in RF (-) RA patients. No statistically significant difference in frequency of a-hnRNP/RA33 and AFA between RF(+) RA, RF(-) RA, and UA was observed. CONCLUSIONS: Our results suggest that a-CEP-1 may help in differentiation between RF(-) RA and UA. a-CEP-1 and a-Sa may be useful while diagnosing EIA. a-CarP may be used in differentiation of RA RF(-) and UA. However, a follow-up study is needed to evaluate the prognostic value of analyzed antibodies.

Mice with epidermal filaggrin deficiency show increased immune reactivity to nickel.

BACKGROUND: Nickel allergy and dermatitis have been associated with filaggrin gene mutations in epidemiological studies, but the mechanisms mediating these associations are unknown. OBJECTIVES: To investigate whether filaggrin-deficient flaky tail (ft/ft) mice show increased immune reactivity to nickel and elucidate the mechanisms mediating this. METHODS: The immune responses to nickel, 2,4-dinitrofluorobenzene (DNFB), cinnamal and p-phenylenediamine were assessed in ft/ft and wild-type (WT) mice. The amounts of nickel in the skin of ft/ft and WT mice were determined 20 hours after nickel exposure. The effect of blocking either the interleukin (IL)-17A pathway or the IL-1 pathway on the response to nickel in ft/ft mice was evaluated. RESULTS: Increased responsiveness to nickel, DNFB and cinnamal was observed in ft/ft mice as compared with controls. A reduced amount of nickel was found in the skin of ft/ft mice as compared with WT mice, suggesting increased nickel absorption by the skin of ft/ft mice. Blocking either the IL-17A pathway or the IL-1 pathway reduced nickel responsiveness in ft/ft mice. CONCLUSIONS: These findings suggest that the increased nickel responsiveness associated with epidermal filaggrin deficiency is mediated by a combination of increased nickel penetration and the steady-state inflammation found in the skin of filaggrin-deficient mice.

The atopic march and atopic multimorbidity: Many trajectories, many pathways.

The atopic march recognizes the increased occurrence of asthma, allergic rhinitis, or both after atopic dermatitis (AD) onset. Mechanisms for developing atopic comorbidities after AD onset are poorly understood but can involve the impaired cutaneous barrier, which facilitates cutaneous sensitization. The association can also be driven or amplified in susceptible subjects by a systemic TH2-dominant immune response to cutaneous inflammation. However, these associations might merely involve shared genetic loci and environmental triggers, including microbiome dysregulation, with the temporal sequence reflecting tissue-specific peak time of occurrence of each disease, suggesting more of a clustering of disorders than a march. Prospective longitudinal cohort studies provide an opportunity to explore the relationships between postdermatitis development of atopic disorders and potential predictive phenotypic, genotypic, and environmental factors. Recent investigations implicate disease severity and persistence, age of onset, parental atopic history, filaggrin (FLG) mutations, polysensitization, and the nonrural environment among risk factors for development of multiple atopic comorbidities in young children with AD. Early intervention studies to repair the epidermal barrier or alter exposure to the microbiome or allergens might elucidate the relative roles of barrier defects, genetic locus alterations, and environmental exposures in the risk and sequence of occurrence of TH2 activation disorders.

Topical administration of EGF suppresses immune response and protects skin barrier in DNCB-induced atopic dermatitis in NC/Nga mice.

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by a complex, heterogeneous pathogenesis including skin barrier dysfunction, immunology, and pruritus. Although epidermal growth factor (EGF) is essential for epithelial homeostasis and wound healing, the effect of EGF on AD remains to be explored. To develop a new therapy for AD, the anti-AD potential of EGF was investigated by inducing AD-like skin lesions in NC/Nga mice using 2,4-dinitrochlorobenzene (DNCB). EGF was administrated to NC/Nga mice to evaluate its therapeutic effect on DNCB-induced AD. EGF treatment improved dermatitis score, ear thickness, epidermal hyperplasia, serum total immunoglobulin E level, and transepidermal water loss in NC/Nga mice with DNCB-induced AD. In addition, levels of skin barrier-related proteins such as filaggrin, involucrin, loricrin, occludin, and zonula occludens-1 (ZO-1) were increased by EGF treatment. These beneficial effects of EGF on AD may be mediated by EGF regulation of Th1/Th2-mediated cytokines, mast cell hyperplasia, and protease activated receptor-2 (PAR-2) and thymic stromal lymphopoietin (TSLP), which are triggers of AD. Taken together, our findings suggest that EGF may potentially protect against AD lesional skin via regulation of skin barrier function and immune response.

Effect of short-term liver X receptor activation on epidermal barrier features in mild to moderate atopic dermatitis: A randomized controlled trial.

BACKGROUND: Liver X receptors (LXRs) are involved in maintaining epidermal barrier and suppressing inflammatory responses in model systems. The LXR agonist VTP-38543 showed promising results in improving barrier function and inflammatory responses in model systems. OBJECTIVE: To assess the safety, tolerability, cellular and molecular changes, and clinical efficacy of the topical VTP-38543 in adults with mild to moderate atopic dermatitis (AD). METHODS: A total of 104 ambulatory patients with mild to moderate AD were enrolled in this randomized, double-blind, vehicle-controlled trial between December 2015 and September 2016. VTP-38543 cream in 3 concentrations (0.05%, 0.15%, and 1.0%) or placebo was applied twice daily for 28 days. Pretreatment and posttreatment skin biopsy specimens were obtained from a subset of 33 patients. Changes in SCORing of Atopic Dermatitis, Eczema Area and Severity Index, Investigator's Global Assessment, and tissue biomarkers (by real-time polymerase chain reaction and immunostaining) were evaluated. RESULTS: Topical VTP-38543 was safe and well tolerated. VTP-38543 significantly increased messenger RNA (mRNA) expression of epidermal barrier differentiation (loricrin and filaggrin, P = .02) and lipid (adenosine triphosphate-binding cassette subfamily G member 1 and sterol regulatory element binding protein 1c, P < .01) measures and reduced epidermal hyperplasia markers (thickness, keratin 16 mRNA). VTP-38543 nonsignificantly suppressed cellular infiltrates and down-regulated mRNA expression of several TH17/TH22-related (phosphatidylinositol 3, S100 calcium-binding protein A12) and innate immunity (interleukin 6) markers. CONCLUSION: Topical VTP-38543 is safe and well tolerated. Its application led to improvement in barrier differentiation and lipids. Longer-term studies are needed to clarify whether a barrier-based approach can induce meaningful suppression of immune abnormalities. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT02655679.

Mechanism for initiation of food allergy: Dependence on skin barrier mutations and environmental allergen costimulation.

BACKGROUND: Mechanisms for the development of food allergy in neonates are unknown but clearly linked in patient populations to a genetic predisposition to skin barrier defects. Whether skin barrier defects contribute functionally to development of food allergy is unknown. OBJECTIVE: The purpose of the study was to determine whether skin barrier mutations, which are primarily heterozygous in patient populations, contribute to the development of food allergy. METHODS: Mice heterozygous for the filaggrin (Flg)ft and Tmem79ma mutations were skin sensitized with environmental and food allergens. After sensitization, mice received oral challenge with food allergen, and then inflammation, inflammatory mediators, and anaphylaxis were measured. RESULTS: We define development of inflammation, inflammatory mediators, and food allergen-induced anaphylaxis in neonatal mice with skin barrier mutations after brief concurrent cutaneous exposure to food and environmental allergens. Moreover, neonates of allergic mothers have increased responses to suboptimal sensitization with food allergens. Importantly, responses to food allergens by these neonatal mice were dependent on genetic defects in skin barrier function and on exposure to environmental allergens. ST2 blockade during skin sensitization inhibited the development of anaphylaxis, antigen-specific IgE, and inflammatory mediators. Neonatal anaphylactic responses and antigen-specific IgE were also inhibited by oral pre-exposure to food allergen, but interestingly, this was blunted by concurrent pre-exposure of the skin to environmental allergen. CONCLUSION: These studies uncover mechanisms for food allergy sensitization and anaphylaxis in neonatal mice that are consistent with features of human early-life exposures and genetics in patients with clinical food allergy and demonstrate that changes in barrier function drive development of anaphylaxis to food allergen.

Eupatilin, an activator of PPARα, inhibits the development of oxazolone-induced atopic dermatitis symptoms in Balb/c mice.

Eupatilin (5,7-dihydroxy-3',4',6-trimethoxyflavone) is the main lipophilic flavonoid obtained from the Artemisia species. Eupatilin has been reported to have anti-apoptotic, anti-oxidative and anti-inflammatory activities. Previously, we found that eupatilin increases transcriptional activity and expression of peroxisome proliferator-activated receptor α (PPARα) in a keratinocyte cell line and acts as an agonist of PPARα. PPARα agonists ameliorate atopic dermatitis (AD) and restore the skin barrier function. In this study, we confirmed that the effects of eupatilin improved AD-like symptoms in an oxazolone-induced AD-like mouse model. Furthermore, we found that eupatilin suppressed the levels of serum immunoglobulin E (IgE), interleukin-4 (IL-4), and AD involved cytokines, such as tumor necrosis factor α (TNFα), interferon-γ (IFN-γ), IL-1ß, and thymic stromal lymphopoietin (TSLP), IL-33, IL-25 and increased the levels of filaggrin and loricrin in the oxazolone-induced AD-like mouse model. Taken together, our data suggest that eupatilin is a potential candidate for the treatment of AD.

Comparative study of the diagnostic and prognostic value of antibodies against chimeric citrullinated synthetic peptides and CCP3/CCP3.1 assays.

BACKGROUND: The objective of the study was to compare the diagnostic yield of home-made ELISA tests based on synthetic chimeric fibrin/filaggrin citrullinated peptides (CFFCPs) with CCP3 and CCP3.1 commercial tests to detect anti-citrullinated protein/peptide antibodies (ACPAs) in rheumatoid arthritis (RA) patients. The prognostic value is also studied in a cohort of patients with early RA. Moreover, we transfer immunological assays from microtiter plates to microarray formats to allow the simultaneous analysis of several peptide sequences and reduce the volume of serum from patients. METHODS: The diagnostic study includes: 100 RA patients who fulfilled the 1987 ACR criteria; 100 healthy blood donors; 35 patients with SLE according ACR criteria; 35 patients with PsA fulfilling the Wright and Moll criteria and 30 patients with HCV infection. The prognostic value study includes 50 patients with early RA with follow-up data available. All samples are from outpatients attending the Rheumatology Department of the Hospital Clinic of Barcelona. RESULTS: Similar sensitivity, specificity and predictive values for the diagnosis of RA of CCFCPs compared to CCP3/CCP3.1 were obtained. Although a high concordance is observed between anti-CFFCPs and anti-CCP3/CCP3.1 in the early patients that rendered Larsen radiographic progression, CFFCPs could be a better marker of radiographic outcome. Strong correlations between the microarray and ELISA results were found for individual CFFCPs peptides. CONCLUSIONS: The development of multiplexing techniques combining a different spectrum of markers in a single analysis, including CFFCP peptides, could allow a more detailed analysis of the autoantibodies reactivity found in the sera of patients suffering of this heterogeneous disease.

Impaired intracellular pathogen clearance and inflammatory joint disease: Is Whipple's disease a guiding light?

Whipple's disease can mimic spondyloarthritis (SpA) or rheumatoid arthritis (RA) for many years and, in a few cases, induces the development of antibodies to cyclic citrullinated peptides. The causative agent Tropheryma whipplei can smolder within cells, including macrophages, by suppressing the xenophagic process, a type of selective autophagy that targets pathogens. Other inflammatory joint diseases may also stem from impaired xenophagy with persistence of bacteria or viruses that can eventually migrate from the mucous membranes to the joints and entheses, where they may exert adverse effects on immune responses, even if they fail to replicate. Xenophagy interferes with the loading of peptides (including self-peptides) onto major histocompatibility complex proteins. Another effect of xenophagy is the induction of citrullination, which accelerates pathogen clearance but can also contribute to loss of self-tolerance. Pathogens react to citrullination by becoming dormant. These facts suggest a role in SpA and RA for impaired xenophagy with migration of pathogens to joints and entheses, where they may remain dormant. Studies of fibroblast-like synoviocytes showed alterations in autophagy that correlated with citrullination of vimentin, alpha-enolase, and filaggrin, which are targets of RA-specific autoantibodies. Compared to autoimmune responses (T-cell or B-cell clones, autoantibodies) alone, metastatic spread of pathogens initially located in the mucous membranes as the event inducing inflammatory joint disease would constitute a better explanation to the heterogeneous distribution of the joint involvement, palindromic onset in some cases (as seen in Whipple's disease), occurrence of flares, and possible development of escape phenomenon to immunomodulating drugs in a manner reminiscent of delayed antibiotic resistance.

Barrier dysfunction in the skin allergy.

The skin is continuously exposed to external pathogens, and its barrier function is critical for skin homeostasis. Previous studies have shown that the barrier dysfunction is one of the most predisposing factors for the development of skin allergic diseases such as atopic dermatitis. In this article, we summarize how the physical barrier of the skin is organized and review its link to the pathomechanism of skin allergic diseases. We describe the formation of the SC barrier in terms of the following five categories: 1) filaggrin metabolism; 2) cornified envelope; 3) intercellular lipids; 4) corneodesmosome; and 5) corneocyte desquamation. New approaches to restoring the skin barrier function are also discussed.

Identification of atopic dermatitis subgroups in children from 2 longitudinal birth cohorts.

BACKGROUND: Atopic dermatitis (AD) is a prevalent disease with variable natural history. Longitudinal birth cohort studies provide an opportunity to define subgroups on the basis of disease trajectories, which may represent different genetic and environmental pathomechanisms. OBJECTIVES: We sought to investigate the existence of distinct longitudinal phenotypes of AD and test whether these findings are reproducible in 2 independent cohorts. METHODS: The presence of AD was examined in 2 birth cohort studies including 9894 children from the United Kingdom (ALSPAC) and 3652 from the Netherlands (PIAMA). AD was defined by parental report of a typical itchy and/or flexural rash. Longitudinal latent class analysis was used to investigate patterns of AD from birth to the age of 11 to 16 years. We investigated associations with known AD risk factors, including FLG null mutations, 23 other established AD-genetic risk variants, and atopic comorbidity. RESULTS: Six latent classes were identified, representing subphenotypes of AD, with remarkable consistency between the 2 cohorts. The most prevalent class was early-onset-early-resolving AD, which was associated with male sex. Two classes of persistent disease were identified (early-onset-persistent and early-onset-late-resolving); these were most strongly associated with the AD-genetic risk score as well as personal and parental history of atopic disease. A yet unrecognized class of mid-onset-resolving AD, not associated with FLG mutations, but strongly associated with asthma, was identified. CONCLUSIONS: Six classes based on temporal trajectories of rash were consistently identified in 2 population-based cohorts. The differing risk factor profiles and diverse prognoses demonstrate the potential importance of a stratified medicine approach for AD.

Physical Characteristics of a Citrullinated Pro-Filaggrin Epitope Recognized by Anti-Citrullinated Protein Antibodies in Rheumatoid Arthritis Sera.

Rheumatoid arthritis (RA) is an autoimmune disease of complex etiology. A characteristic feature of a subset of RA is the presence of anti-citrullinated protein antibodies (ACPA), which correlate with a progressive disease course. In this study, we employed streptavidin capture enzyme-linked immunosorbent assay to analyze ACPA reactivity. Using the pro-filaggrin peptide HQCHQEST-Cit-GRSRGRCGRSGS, as template, we analyzed the reactivity of RA sera and healthy donor sera to various peptides in order to determine the physical characteristics of the citrullinated pro-filaggrin epitope and to examine whether biotin labelling influence antibody recognition. The full-length cyclic pro-filaggrin peptide and a linear form with a N-terminal biotin, was recognized to the same level, whereas, a notable difference in ACPA reactivity to the linear peptides with a C-terminal biotin was found, probably due to steric hindrance. Screening of linear and cyclic truncated peptides, revealed that small cyclic peptides containing 10-12 amino acids are favored over the linear. Moreover, the charged amino acids C-terminal to citrulline were found to be essential for antibody reactivity, most important was the charged amino acid in position 4 C-terminal to citrulline. Collectively, peptide structure, length, the presence of charged amino acids and biotin labelling markedly influence antibody reactivity. In relation to the clinical diagnostics of ACPA, these findings may reflect the differences in diagnostic assays used for detection of ACPA, which relates to differences in sensitivity and specificity dependent on the assay applied.