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BackgroundAtopic dermatitis (AD) is a major inflammatory condition of the skin caused by inherited skin barrier deficiency, with mutations in the filaggrin gene predisposing to development of AD. Support for barrier deficiency initiating AD came from flaky tail mice, which have a frameshift mutation in Flg and also carry an unknown gene, matted, causing a matted hair phenotype.ObjectiveWe sought to identify the matted mutant gene in mice and further define whether mutations in the human gene were associated with AD.MethodsA mouse genetics approach was used to separate the matted and Flg mutations to produce congenic single-mutant strains for genetic and immunologic analysis. Next-generation sequencing was used to identify the matted gene. Five independently recruited AD case collections were analyzed to define associations between single nucleotide polymorphisms (SNPs) in the human gene and AD.ResultsThe matted phenotype in flaky tail mice is due to a mutation in the Tmem79/Matt gene, with no expression of the encoded protein mattrin in the skin of mutant mice. Matt(ft) mice spontaneously have dermatitis and atopy caused by a defective skin barrier, with mutant mice having systemic sensitization after cutaneous challenge with house dust mite allergens. Meta-analysis of 4,245 AD cases and 10,558 population-matched control subjects showed that a missense SNP, rs6684514, [corrected] in the human MATT gene has a small but significant association with AD.ConclusionIn mice mutations in Matt cause a defective skin barrier and spontaneous dermatitis and atopy. A common SNP in MATT has an association with AD in human subjects.

Background: Atopic diseases are characterized by IgE antibody responses that are dependent on cognate CD4 T cell help and T cell‐produced IL‐4 and IL‐13. Current models of IgE cell differentiation point to the role of IgG memory B cells as precursors of pathogenic IgE plasma cells. The goal of this work was to identify intrinsic features of memory B cells that are associated with IgE production in atopic diseases. Methods: Peripheral blood B lymphocytes were collected from individuals with physician diagnosed asthma or atopic dermatitis (AD) and from non‐atopic individuals. These samples were analyzed by spectral flow cytometry, single cell RNA sequencing (scRNAseq), and in vitro activation assays. Results: We identified a novel population of IgG memory B cells characterized by the expression of IL‐4/IL‐13 regulated genes FCER2/CD23, IL4R, IL13RA1, and IGHE, denoting a history of differentiation during type 2 immune responses. CD23+IL4R+IgG+ memory B cells had increased occurrence in individuals with atopic disease. Importantly, the frequency of CD23+IL4R+IgG+ memory B cells correlated with levels of circulating IgE. Consistently, in vitro stimulated B cells from atopic individuals generated more IgE+ cells than B cells from non‐atopic subjects. Conclusions: These findings suggest that CD23+IL4R+ IgG+ memory B cells transcribing IGHE are potential precursors of IgE plasma cells and are linked to pathogenic IgE production. [ABSTRACT FROM AUTHOR]

The unique differentiation of IgE cells suggests unconventional mechanisms of IgE memory. IgE germinal centre cells are transient, most IgE cells are plasma cells, and high affinity IgE is produced by the switching of IgG1 cells to IgE. Here we investigate the function of subsets of IgG1 memory B cells in IgE production and find that two subsets of IgG1 memory B cells, CD80+CD73+ and CD80-CD73-, contribute distinctively to the repertoires of high affinity pathogenic IgE and low affinity non-pathogenic IgE. Furthermore, repertoire analysis indicates that high affinity IgE and IgG1 plasma cells differentiate from rare CD80+CD73+ high affinity memory clones without undergoing further mutagenesis. By identifying the cellular origin of high affinity IgE and the clonal selection of high affinity memory B cells into the plasma cell fate, our findings provide fundamental insights into the pathogenesis of allergies, and on the mechanisms of antibody production in memory B cell responses. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is a common inflammatory skin disease affecting up to 20% of children and 3% of adults worldwide and is associated with dysregulation of the skin barrier. Although type 2 responses are implicated in AD, emerging evidence indicates a potential role for the IL-17A signaling axis in AD pathogenesis. In this study we show that in the filaggrin mutant mouse model of spontaneous AD, IL-17RA deficiency (Il17ra-/-) resulted in severe exacerbation of skin inflammation. Interestingly, Il17ra-/- mice without the filaggrin mutation also developed spontaneous progressive skin inflammation with eosinophilia, as well as increased levels of thymic stromal lymphopoietin (TSLP) and IL-5 in the skin. Il17ra-/- mice have a defective skin barrier with altered filaggrin expression. The barrier dysregulation and spontaneous skin inflammation in Il17ra-/- mice was dependent on TSLP, but not the other alarmins IL-25 and IL-33. The associated skin inflammation was mediated by IL-5-expressing pathogenic effector Th2 cells and was independent of TCRgd T cells and IL-22. An absence of IL-17RA in nonhematopoietic cells, but not in the hematopoietic cells, was required for the development of spontaneous skin inflammation. Skin microbiome dysbiosis developed in the absence of IL-17RA, with antibiotic intervention resulting in significant amelioration of skin inflammation and reductions in skin-infiltrating pathogenic effector Th2 cells and TSLP. This study describes a previously unappreciated protective role for IL-17RA signaling in regulation of the skin barrier and maintenance of skin immune homeostasis. [ABSTRACT FROM AUTHOR]

B cells have been described as having the capacity to regulate cellular immune responses and suppress inflammatory processes. One such regulatory B-cell population is defined as IL-10-producing CD19+CD1dhi cells. Previous work has identified an expansion of these cells in mice infected with the helminth, Schistosoma mansoni. Here, microarray analysis of CD19+CD1dhi B cells from mice infected with S. mansoni demonstrated significantly increased Tlr7 expression, while CD19+CD1dhi B cells from uninfected mice also demonstrated elevated Tlr7 expression. Using IL-10 reporter, Il10−/− and Tlr7−/- mice, we formally demonstrate that TLR7 ligation of CD19+CD1dhi B cells increases their capacity to produce IL-10. In a mouse model of allergic lung inflammation, the adoptive transfer of TLR7-elicited CD19+CD1dhi B cells reduced airway inflammation and associated airway hyperresponsiveness. Using DEREG mice to deplete FoxP3+ T regulatory cells in allergen-sensitized mice, we show that that TLR7-elicited CD19+CD1dhi B cells suppress airway hyperresponsiveness via a T regulatory cell dependent mechanism. These studies identify that TLR7 stimulation leads to the expansion of IL-10-producing CD19+CD1dhi B cells, which can suppress allergic lung inflammation via T regulatory cells. [ABSTRACT FROM AUTHOR]

Background: Filaggrin (FLG) mutations result in reduced stratum corneum (SC) natural moisturizing factor (NMF) components and consequent increased SC pH. Because higher pH activates SC protease activity, we hypothesized an enhanced release of proinflammatory IL-1 cytokines from corneocytes in patients with atopic dermatitis (AD) with FLG mutations (AD FLG ) compared with that seen in patients with AD without these mutations (AD NON-FLG ). Objectives: We sought to investigate SC IL-1 cytokine profiles in the uninvolved skin of controls and patients with AD FLG versus patients with AD NON-FLG . We also sought to examine the same profiles in a murine model of filaggrin deficiency (Flgft/Flgft [FlgdelAPfal ] mice). Methods: One hundred thirty-seven patients were studied. NMF levels were ascertained using confocal Raman spectroscopy; transepidermal water loss and skin surface pH were measured. IL-1α, IL-1β, IL-18, IL-1 receptor antagonist (IL-1RA), and IL-8 levels were determined in SC tape strips from 93 patients. All subjects were screened for 9 FLG mutations. Flgft/Flgft (FlgdelAPfal) mice, separated from maFlgft/maFlgft (flaky tail) mice, were used for the preparation and culture of primary murine keratinocytes and as a source of murine skin. RT-PCR was performed using primers specific for murine IL-1α, IL-1β, and IL-1RA. Results: SC IL-1 levels were increased in patients with AD FLG ; these levels were inversely correlated with NMF levels. NMF values were also inversely correlated with skin surface pH. Skin and keratinocytes from Flgft/Flgft mice had upregulated expression of IL-1β and IL-1RA mRNA. Conclusions: AD FLG is associated with an increased SC IL-1 cytokine profile; this profile is also seen in a murine homologue of filaggrin deficiency. These findings might have importance in understanding the influence of FLG mutations on the inflammasome in the pathogenesis of AD and help individualize therapeutic approaches. [Copyright &y& Elsevier]

B cells have been described as having the capacity to regulate cellular immune responses and suppress inflammatory processes. One such regulatory B-cell population is defined as IL-10-producing CD19(+) CD1d(hi) cells. Previous work has identified an expansion of these cells in mice infected with the helminth, Schistosoma mansoni. Here, microarray analysis of CD19(+) CD1d(hi) B cells from mice infected with S. mansoni demonstrated significantly increased Tlr7 expression, while CD19(+) CD1d(hi) B cells from uninfected mice also demonstrated elevated Tlr7 expression. Using IL-10 reporter, Il10(-/-) and Tlr7(-/-) mice, we formally demonstrate that TLR7 ligation of CD19(+) CD1d(hi) B cells increases their capacity to produce IL-10. In a mouse model of allergic lung inflammation, the adoptive transfer of TLR7-elicited CD19(+) CD1d(hi) B cells reduced airway inflammation and associated airway hyperresponsiveness. Using DEREG mice to deplete FoxP3(+) T regulatory cells in allergen-sensitized mice, we show that that TLR7-elicited CD19(+) CD1d(hi) B cells suppress airway hyperresponsiveness via a T regulatory cell dependent mechanism. These studies identify that TLR7 stimulation leads to the expansion of IL-10-producing CD19(+) CD1d(hi) B cells, which can suppress allergic lung inflammation via T regulatory cells., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The activation of B cells by pathogens to elicit antibody production is a central facet of immunity. Pathogens also evoke the expansion of B cells that can function in the regulation of immunity. Different pathogens have been described with the capacity to drive such regulatory B (Breg) cells. One group of pathogens, parasitic helminths, has been used experimentally to identify and explore immunological mechanisms of Breg cells. Several species of helminths have demonstrated the capacity to expand Breg cell populations in mice, while the presence of Breg cells in humans infected with certain helminths has also been identified. Herein, we outline how the helminth Schistosoma mansoni can expand Breg cellular responses in vitro. We describe the establishment of a laboratory-based S. mansoni life cycle and methodology for detecting Breg cells via flow cytometry.