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Mast cell-deficient mice are widely used to identify and quantify contributions of mast cells to diverse biological responses in vivo, including allergic inflammation. However, despite the fact that scores of genes have been identified as modifiers of allergic inflammation, most mast cell-deficient models have been available only on a single genetic background. We transferred the KitW-sh allele onto the BALB/c background to generate BALB/c mast cell-deficient mice (BALB/c-KitW-sh/W-sh). BALB/c-KitW-sh/W-sh mice have dramatically reduced mast cell numbers (0–2% of wild type) in all tissues examined, as well as subtle hematologic differences from the corresponding wild type mice, including splenomegaly with evidence of increased splenic hematopoiesis. We examined in BALB/c-KitW-sh/W-sh mice models of allergic inflammation that are substantially diminished in C57BL/6-KitW-sh/W-sh mast cell-deficient mice. In a model of acute allergic inflammation, i.e., IgE-dependent passive cutaneous anaphylaxis, both ear swelling and leukocyte infiltration were largely or entirely absent in BALB/c-KitW-sh/W-sh mice. In contrast, in two different models of allergic airway inflammation, airway hyperresponsiveness, lung inflammation, and airway remodeling developed robustly in mast cell-deficient BALB/c-KitW-sh/W-sh mice. These results support the conclusion that the importance of mast cell contributions in various models of allergic inflammation may be at least partially determined by genetic background. Unlike C57BL/6-KitW-sh/W-sh mice, BALB/c-KitW-sh/W-sh mice exhibit wild-type levels of airway hyperresponsiveness and lung inflammation and remodeling in two models of allergic airway inflammation. By contrast, neither genotype exhibits signs of IgE-dependent passive cutaneous anaphylaxis. Thus, genetic background influences the apparent importance of mast cells in different models of allergic diseases.

BACKGROUND: Although autoimmunity and hyperinflammation secondary to recombination activating gene (RAG) deficiency have been associated with delayed diagnosis and even death, our current understanding is limited primarily to small case series. OBJECTIVE: Understand the frequency, severity, and treatment responsiveness of autoimmunity and hyperinflammation in RAG deficiency. METHODS: In reviewing the literature and our own database, we identified 85 patients with RAG deficiency, reported between 2001 and 2016, and compiled the largest case series to date of 63 patients with prominent autoimmune and/or hyperinflammatory pathology. RESULTS: Diagnosis of RAG deficiency was delayed a median of 5 years from the first clinical signs of immune dysregulation. Most patients (55.6%) presented with more than 1 autoimmune or hyperinflammatory complication, with the most common etiologies being cytopenias (84.1%), granulomas (23.8%), and inflammatory skin disorders (19.0%). Infections, including live viral vaccinations, closely preceded the onset of autoimmunity in 28.6% of cases. Autoimmune cytopenias had early onset (median, 1.9, 2.1, and 2.6 years for autoimmune hemolytic anemia, immune thrombocytopenia, and autoimmune neutropenia, respectively) and were refractory to intravenous immunoglobulin, steroids, and rituximab in most cases (64.7%, 73.7%, and 71.4% for autoimmune hemolytic anemia, immune thrombocytopenia, and autoimmune neutropenia, respectively). Evans syndrome specifically was associated with lack of response to first-line therapy. Treatment-refractory autoimmunity/ hyperinflammation prompted hematopoietic stem cell transplantation in 20 patients. CONCLUSIONS: Autoimmunity/hyperinflammation can be a presenting sign of RAG deficiency and should prompt further evaluation. Multilineage cytopenias are often refractory to immunosuppressive treatment and may require hematopoietic cell transplantation for definitive management. (C) 2019 The Authors. Published by Elsevier Inc. on behalf of the American Academy of Allergy, Asthma & Immunology.

Background: The prevalence and impact of allergic and immune-mediated food disorders in pediatric acute-onset neuropsychiatric syndrome (PANS) are mostly unknown. Objective: We sought to explore the prevalence of atopic dermatitis (AD), asthma, allergic rhinitis (AR), IgE-mediated food allergies (FAs), and other immune-mediated food disorders requiring food avoidance in patients with PANS. In addition, to further understand the extent of food restriction in this population, we investigated the empiric use of dietary measures to improve PANS symptoms. Methods: Pediatric patients in a PANS Clinic and Research Program were given surveys regarding their caregiver burdens, allergic and food-related medical history, and whether food elimination resulted in perception of improvement of PANS symptoms. A review of health records was conducted to confirm that all responses in the survey were concordant with documentation of each patient's medical chart. Results: Sixty-nine (ages 4-20 years) of 80 subjects who fulfilled PANS criteria completed the surveys. Thirteen (18.8%) had AD, 11 (15.9%) asthma, 33 (47.8%) AR, 11 (15.9%) FA, 1 (1.4%) eosinophilic gastrointestinal disorders, 1 (1.4%) food protein-induced enterocolitis syndrome, 3 (4.3%) milk protein-induced proctocolitis syndrome, and 3 (4.3%) celiac disease. Thirty subjects (43.5%) avoided foods due to PANS; elimination of gluten and dairy was most common and was associated with perceived improvement of PANS symptoms (by parents). This perceived improvement was not confirmed with objective data. Conclusions: The prevalence of allergic and immune-mediated food disorders in PANS is similar to the general population as reported in the literature, with the exception of AR that appears to be more prevalent in our PANS cohort. More research will be required to establish whether diet or allergies influence PANS symptoms.

Sudden-onset severe obsessive-compulsive symptoms and/or severely restrictive food intake with at least two coinciding, similarly debilitating neuropsychiatric symptoms define Pediatric Acute-onset Neuropsychiatric Syndrome (PANS). When associated with Group A Streptococcus, the syndrome is labeled Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal infections (PANDAS). An abnormal immune response to infection and subsequent neuroinflammation is postulated to play an etiologic role. Most patients have a relapsing-remitting course. Treatment outcome data for youth with PANS and PANDAS are limited.One hundred seventy-eight consecutive patients were seen in the Stanford PANS clinic between September 1, 2012 and January 15, 2016, of whom 98 met PANS or PANDAS criteria, had a single episode of PANS or relapsing/remitting course, and collectively experienced 403 flares. Eighty-five flares were treated with 102 total courses of oral corticosteroids of either short (4-5 days) or long (5 days-8 weeks) duration. Response to treatment was assessed within 14 days of initiating a short burst of corticosteroids and at the end of a long burst based on clinician documentation and patient questionnaires. Data were analyzed by using multilevel random-effects models.Patients experienced shorter flares when treated with oral corticosteroids (6.4 ± 5.0 weeks vs. 11.4 ± 8.6 weeks) than when not treated (p 0.001), even after controlling for presumed confounding variables, including age at flare, weeks since onset of PANS illness, sex, antibiotic treatment, prophylactic antibiotics, previous immunomodulatory treatment, maintenance anti-inflammatory therapy, psychiatric medications, and cognitive behavioral therapy (p 0.01). When corticosteroids were given for the initial PANS episode, flares tended to be shorter (10.3 ± 5.7 weeks) than when not treated (16.5 ± 9.6 weeks) (p = 0.06). This difference was statistically significant after controlling for the relevant confounding variables listed earlier (p 0.01). Earlier use of corticosteroids was associated with shorter flare durations (p 0.001). Longer courses of corticosteroids were associated with a more enduring impact on the duration of neuropsychiatric symptom improvement (p = 0.014).Corticosteroids may be a helpful treatment intervention in patients with new-onset and relapsing/remitting PANS and PANDAS, hastening symptom improvement or resolution. When corticosteroids are given earlier in a disease flare, symptoms improve more quickly and patients achieve clinical remission sooner. Longer courses of corticosteroids may result in more durable remissions. A double-blind placebo-controlled clinical trial of corticosteroids in PANS is warranted to formally assess treatment efficacy.

International audience; Anaphylaxis is a severe systemic hypersensitivity reaction that is rapid in onset; characterized by life-threatening airway, breathing, and/or circulatory problems; and usually associated with skin and mucosal changes. Because it can be triggered in some persons by minute amounts of antigen (eg, certain foods or single insect stings), anaphylaxis can be considered the most aberrant example of an imbalance between the cost and benefit of an immune response. This review will describe current understanding of the immunopathogenesis and pathophysiology of anaphylaxis, focusing on the roles of IgE and IgG antibodies, immune effector cells, and mediators thought to contribute to examples of the disorder. Evidence from studies of anaphylaxis in human subjects will be discussed, as well as insights gained from analyses of animal models, including mice genetically deficient in the antibodies, antibody receptors, effector cells, or mediators implicated in anaphylaxis and mice that have been "humanized" for some of these elements. We also review possible host factors that might influence the occurrence or severity of anaphylaxis. Finally, we will speculate about anaphylaxis from an evolutionary perspective and argue that, in the context of severe envenomation by arthropods or reptiles, anaphylaxis might even provide a survival advantage.

Asthma has multiple features, including airway hyperreactivity, inflammation and remodelling. The TNF superfamily member TNFSF14 (LIGHT), via interactions with the receptor TNFRSF14 (HVEM), can support TH2 cell generation and longevity and promote airway remodelling in mouse models of asthma, but the mechanisms by which TNFSF14 functions in this setting are incompletely understood. Here we find that mouse and human mast cells (MCs) express TNFRSF14 and that TNFSF14:TNFRSF14 interactions can enhance IgE-mediated MC signalling and mediator production. In mouse models of asthma, TNFRSF14 blockade with a neutralizing antibody administered after antigen sensitization, or genetic deletion of Tnfrsf14, diminishes plasma levels of antigen-specific IgG1 and IgE antibodies, airway hyperreactivity, airway inflammation and airway remodelling. Finally, by analysing two types of genetically MC-deficient mice after engrafting MCs that either do or do not express TNFRSF14, we show that TNFRSF14 expression on MCs significantly contributes to the development of multiple features of asthma pathology., TNFSF14 (LIGHT) contributes to airway inflammation and remodelling. Here the authors show that TNFSF14 acting on its receptor TNFRSF14 on mast cells enhances their IgE-dependent activation and that interference with this pathway attenuates features of asthma pathology in mice.