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Medical Principles and Practice :... 2022IgE-mediated type I hypersensitivity reactions have many reported beneficial functions in immune defense against parasites, venoms, toxins, etc. However, they are best... (Review)
Review
IgE-mediated type I hypersensitivity reactions have many reported beneficial functions in immune defense against parasites, venoms, toxins, etc. However, they are best known for their role in allergies, currently affecting almost one third of the population worldwide. IgE-mediated allergic diseases result from a maladaptive type 2 immune response that promotes the synthesis of IgE antibodies directed at a special class of antigens called allergens. IgE antibodies bind to type I high-affinity IgE receptors (FcεRI) on mast cells and basophils, sensitizing them to get triggered in a subsequent encounter with the cognate allergen. This promotes the release of a large variety of inflammatory mediators including histamine responsible for the symptoms of immediate hypersensitivity. The development of type 2-driven allergies is dependent on a complex interplay of genetic and environmental factors at barrier surfaces including the host microbiome that builds up during early life. While IgE-mediated immediate hypersensitivity reactions are undoubtedly at the origin of the majority of allergies, it has become clear that similar responses and symptoms can be triggered by other types of adaptive immune responses mediated via IgG or complement involving other immune cells and mediators. Likewise, various nonadaptive innate triggers via receptors expressed on mast cells have been found to either directly launch a hypersensitivity reaction and/or to amplify existing IgE-mediated responses. This review summarizes recent findings on both IgE-dependent and IgE-independent mechanisms in the development of allergic hypersensitivities and provides an update on the diagnosis of allergy.
Topics: Humans; Anaphylaxis; Mast Cells; Immunoglobulin E; Hypersensitivity; Basophils; Hypersensitivity, Immediate
PubMed: 36219943
DOI: 10.1159/000527481 -
Cell Jan 2021Itch is an evolutionarily conserved sensation that facilitates expulsion of pathogens and noxious stimuli from the skin. However, in organ failure, cancer, and chronic...
Itch is an evolutionarily conserved sensation that facilitates expulsion of pathogens and noxious stimuli from the skin. However, in organ failure, cancer, and chronic inflammatory disorders such as atopic dermatitis (AD), itch becomes chronic, intractable, and debilitating. In addition to chronic itch, patients often experience intense acute itch exacerbations. Recent discoveries have unearthed the neuroimmune circuitry of itch, leading to the development of anti-itch treatments. However, mechanisms underlying acute itch exacerbations remain overlooked. Herein, we identify that a large proportion of patients with AD harbor allergen-specific immunoglobulin E (IgE) and exhibit a propensity for acute itch flares. In mice, while allergen-provoked acute itch is mediated by the mast cell-histamine axis in steady state, AD-associated inflammation renders this pathway dispensable. Instead, a previously unrecognized basophil-leukotriene (LT) axis emerges as critical for acute itch flares. By probing fundamental itch mechanisms, our study highlights a basophil-neuronal circuit that may underlie a variety of neuroimmune processes.
Topics: Acute Disease; Allergens; Animals; Basophils; Chronic Disease; Dermatitis, Atopic; Disease Models, Animal; Histamine; Humans; Immunoglobulin E; Inflammation; Leukotrienes; Mast Cells; Mice, Inbred C57BL; Neurons; Phenotype; Pruritus; TRPA1 Cation Channel; TRPV Cation Channels; Mice
PubMed: 33450207
DOI: 10.1016/j.cell.2020.12.033 -
International Journal of Molecular... Jul 2021Anaphylaxis is a severe, acute, life-threatening multisystem allergic reaction resulting from the release of a plethora of mediators from mast cells culminating in... (Review)
Review
Anaphylaxis is a severe, acute, life-threatening multisystem allergic reaction resulting from the release of a plethora of mediators from mast cells culminating in serious respiratory, cardiovascular and mucocutaneous manifestations that can be fatal. Medications, foods, latex, exercise, hormones (progesterone), and clonal mast cell disorders may be responsible. More recently, novel syndromes such as delayed reactions to red meat and hereditary alpha tryptasemia have been described. Anaphylaxis manifests as sudden onset urticaria, pruritus, flushing, erythema, angioedema (lips, tongue, airways, periphery), myocardial dysfunction (hypovolemia, distributive or mixed shock and arrhythmias), rhinitis, wheezing and stridor. Vomiting, diarrhea, scrotal edema, uterine cramps, vaginal bleeding, urinary incontinence, dizziness, seizures, confusion, and syncope may occur. The traditional (or classical) pathway is mediated via T cells, Th2 cytokines (such as IL-4 and 5), B cell production of IgE and subsequent crosslinking of the high affinity IgE receptor (FcεRI) on mast cells and basophils by IgE-antigen complexes, culminating in mast cell and basophil degranulation. Degranulation results in the release of preformed mediators (histamine, heparin, tryptase, chymase, carboxypeptidase, cathepsin G and tumor necrosis factor alpha (TNF-α), and of de novo synthesized ones such as lipid mediators (cysteinyl leukotrienes), platelet activating factor (PAF), cytokines and growth factors such as vascular endothelial growth factor (VEGF). Of these, histamine, tryptase, cathepsin G, TNF-α, LTC, PAF and VEGF can increase vascular permeability. Recent data suggest that mast cell-derived histamine and PAF can activate nitric oxide production from endothelium and set into motion a signaling cascade that leads to dilatation of blood vessels and dysfunction of the endothelial barrier. The latter, characterized by the opening of adherens junctions, leads to increased capillary permeability and fluid extravasation. These changes contribute to airway edema, hypovolemia, and distributive shock, with potentially fatal consequences. In this review, besides mechanisms (endotypes) underlying IgE-mediated anaphylaxis, we also provide a brief overview of IgG-, complement-, contact system-, cytokine- and mast cell-mediated reactions that can result in phenotypes resembling IgE-mediated anaphylaxis. Such classifications can lead the way to precision medicine approaches to the management of this complex disease.
Topics: Anaphylaxis; Animals; Capillary Permeability; Endothelium, Vascular; Gap Junctions; Humans; Inflammation
PubMed: 34360549
DOI: 10.3390/ijms22157785 -
Allergy Jun 2021Basophils and mast cells contribute to the development of allergic reactions. Whereas these mature effector cells are extensively studied, the differentiation...
BACKGROUND
Basophils and mast cells contribute to the development of allergic reactions. Whereas these mature effector cells are extensively studied, the differentiation trajectories from hematopoietic progenitors to basophils and mast cells are largely uncharted at the single-cell level.
METHODS
We performed multicolor flow cytometry, high-coverage single-cell RNA sequencing analyses, and cell fate assays to chart basophil and mast cell differentiation at single-cell resolution in mouse.
RESULTS
Analysis of flow cytometry data reconstructed a detailed map of basophil and mast cell differentiation, including a bifurcation of progenitors into two specific trajectories. Molecular profiling and pseudotime ordering of the single cells revealed gene expression changes during differentiation. Cell fate assays showed that multicolor flow cytometry and transcriptional profiling successfully predict the bipotent phenotype of a previously uncharacterized population of peritoneal basophil-mast cell progenitors.
CONCLUSIONS
A combination of molecular and functional profiling of bone marrow and peritoneal cells provided a detailed road map of basophil and mast cell development. An interactive web resource was created to enable the wider research community to explore the expression dynamics for any gene of interest.
Topics: Animals; Basophils; Bone Marrow Cells; Cell Differentiation; Mast Cells; Mice; Stem Cells
PubMed: 33078414
DOI: 10.1111/all.14633 -
Frontiers in Immunology 2020Food allergy is a major health issue, affecting the lives of 8% of U.S. children and their families. There is an urgent need to identify the environmental and endogenous... (Review)
Review
Food allergy is a major health issue, affecting the lives of 8% of U.S. children and their families. There is an urgent need to identify the environmental and endogenous signals that induce and sustain allergic responses to ingested allergens. Acute reactions to foods are triggered by the activation of mast cells and basophils, both of which release inflammatory mediators that lead to a range of clinical manifestations, including gastrointestinal, cutaneous, and respiratory reactions as well as systemic anaphylaxis. Both of these innate effector cell types express the high affinity IgE receptor, FcϵRI, on their surface and are armed for adaptive antigen recognition by very-tightly bound IgE antibodies which, when cross-linked by polyvalent allergen, trigger degranulation. These cells also express inhibitory receptors, including the IgG Fc receptor, FcγRIIb, that suppress their IgE-mediated activation. Recent studies have shown that natural resolution of food allergies is associated with increasing food-specific IgG levels. Furthermore, oral immunotherapy, the sequential administration of incrementally increasing doses of food allergen, is accompanied by the strong induction of allergen-specific IgG antibodies in both human subjects and murine models. These can deliver inhibitory signals FcγRIIb that block IgE-induced immediate food reactions. In addition to their role in mediating immediate hypersensitivity reactions, mast cells and basophils serve separate but critical functions as adjuvants for type 2 immunity in food allergy. Mast cells and basophils, activated by IgE, are key sources of IL-4 that tilts the immune balance away from tolerance and towards type 2 immunity by promoting the induction of Th2 cells along with the innate effectors of type 2 immunity, ILC2s, while suppressing the development of regulatory T cells and driving their subversion to a pathogenic pro-Th2 phenotype. This adjuvant effect of mast cells and basophils is suppressed when inhibitory signals are delivered by IgG antibodies signaling FcγRIIb. This review summarizes current understanding of the immunoregulatory effects of mast cells and basophils and how these functions are modulated by IgE and IgG antibodies. Understanding these pathways could provide important insights into innovative strategies for preventing and/or reversing food allergy in patients.
Topics: Allergens; Animals; Basophils; Desensitization, Immunologic; Food Hypersensitivity; Humans; Immunoglobulin E; Immunoglobulin G; Mast Cells; Phenotype; Receptors, Fc; Signal Transduction; Treatment Outcome
PubMed: 33362785
DOI: 10.3389/fimmu.2020.603050 -
Frontiers in Immunology 2022Despite being prone to reverse causation and having unmeasured confounding factors, many clinical observational studies have highlighted the critical association between...
BACKGROUND
Despite being prone to reverse causation and having unmeasured confounding factors, many clinical observational studies have highlighted the critical association between basophils, eosinophils, and lymphocytes and atopic dermatitis (AD). Whether these cells play a causal role in AD development remains uncertain.
METHODS
Data were obtained from the UK Biobank and the Blood Cell Consortium, from a large publicly available genome-wide association study (GWAS) with more than 500,000 subjects of European ancestry and for AD from three independent cohorts with more than 700,000 subjects of European ancestry. We performed single-variable Mendelian randomization (SVMR), followed by multivariable Mendelian randomization (MVMR) to assess the total and direct effects of immune cell counts on AD risk.
RESULTS
SVMR estimates showed that genetically predicted higher eosinophil [odds ratio (OR): 1.23, 95% confidence interval (CI): 1.17-1.29, = 5.85E-16] and basophil counts (OR: 1.11, 95% CI: 1.03-1.19, = 0.004) had an adverse effect on the risk of AD, while a higher lymphocyte count (OR: 0.93, 95% CI: 0.89-0.98, = 0.006) decreased the risk. Reverse MR analysis showed higher basophil (beta: 0.04, 95% CI: 0.01-0.07, = 0.014) and lower lymphocyte counts (beta: -0.05, 95% CI: -0.09 to -0.01, = 0.021) in patients with AD. In MVMR, the effects of eosinophils (OR: 1.19, 95% CI: 1.09-1.29, = 8.98E-05), basophils (OR: 1.19, 95% CI: 1.14-1.24, = 3.72E-15), and lymphocytes (OR: 0.93, 95% CI: 0.89-0.98, = 0.006) were still significant.
DISCUSSION
Mendelian randomization (MR) findings suggest that an increase in the eosinophil and basophil counts and a decrease in the lymphocyte counts are potential causal risk factors for AD. These risk factors are independent of each other.
Topics: Humans; Eosinophils; Basophils; Dermatitis, Atopic; Genome-Wide Association Study; Mendelian Randomization Analysis; Lymphocytes
PubMed: 36569933
DOI: 10.3389/fimmu.2022.1001911 -
Allergology International : Official... Jul 2023Chronic spontaneous urticaria (CSU) is a common skin disease without an etiology in the vast majority of cases. The similarity of symptoms and pathology to... (Review)
Review
Chronic spontaneous urticaria (CSU) is a common skin disease without an etiology in the vast majority of cases. The similarity of symptoms and pathology to allergen-induced skin reactions supports that skin mast cell IgE receptor activation is also involved in CSU. Accumulating evidence also supports a role for blood basophils in disease expression. Blood basopenia is noted in active CSU disease with the recruitment of blood basophils to skin lesion sites. Blood basophils further display altered IgE receptor mediated degranulation patterns in two phenotypes that improve in remission. In active CSU subjects, changes in IgE receptor signaling molecule expression levels accompany the altered degranulation function in blood basophils. The success of therapies targeting IgE in CSU patients have also shown that altered blood basophil phenotypes and enumeration have potential use as a disease biomarker.
Topics: Humans; Basophils; Receptors, IgE; Chronic Disease; Urticaria; Chronic Urticaria
PubMed: 37221123
DOI: 10.1016/j.alit.2023.05.001 -
The Journal of Allergy and Clinical... Aug 2021Eosinophilic asthma and nasal polyposis are hallmarks of aspirin-exacerbated respiratory disease (AERD), and IL-5 inhibition has been shown to provide therapeutic... (Clinical Trial)
Clinical Trial
BACKGROUND
Eosinophilic asthma and nasal polyposis are hallmarks of aspirin-exacerbated respiratory disease (AERD), and IL-5 inhibition has been shown to provide therapeutic benefit. However, IL-5Rα is expressed on many cells in addition to eosinophils, and the mechanisms by which IL-5 inhibition leads to clinical benefit in eosinophilic asthma and nasal polyposis are unlikely to be due exclusively to antieosinophil effects.
OBJECTIVE
We sought to identify the mechanisms by which anti-IL-5 treatment with mepolizumab improves respiratory inflammation in AERD.
METHODS
The clinical characteristics, circulating granulocytes, nasal scraping transcripts, eosinophilic cationic protein, tryptase, and antibody levels, and urinary and nasal eicosanoid levels were measured for 18 subjects with AERD who were taking mepolizumab and compared with those of 18 matched subjects with AERD who were not taking mepolizumab.
RESULTS
Subjects taking mepolizumab had significantly fewer peripheral blood eosinophils and basophils, and those cells that remained had higher surface CRTH2 expression than did the cells from subjects not taking mepolizumab. Nasal prostaglandin F, prostaglandin D metabolites, leukotriene B, and thromboxane levels were lower in subjects taking mepolizumab, as were urinary levels of tetranor-prostaglandin D and leukotriene E. The nasal epithelial cell transcripts that were overexpressed among subjects with AERD who were taking mepolizumab were enriched for genes involved in tight junction formation and cilium organization. Nasal and urinary prostaglandin E, tryptase, and antibody levels were not different between the 2 groups.
CONCLUSION
IL-5 inhibition in AERD decreases production of inflammatory eicosanoids and upregulates tight junction-associated nasal epithelial cell transcripts, likely due to decreased IL-5 signaling on tissue mast cells, eosinophils, and epithelial cells. These direct effects on multiple relevant immune cells contribute to the mechanism of benefit afforded by mepolizumab.
Topics: Adolescent; Adult; Aged; Antibodies, Monoclonal, Humanized; Asthma, Aspirin-Induced; Basophils; Eicosanoids; Eosinophils; Female; Humans; Interleukin-5; Interleukin-5 Receptor alpha Subunit; Male; Middle Aged; Nasal Polyps
PubMed: 34144111
DOI: 10.1016/j.jaci.2021.05.043 -
The Journal of Allergy and Clinical... May 2024Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and... (Review)
Review
Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and basophils are the key pathogenic drivers of CSU; their activation results in histamine and cytokine release with subsequent dermal inflammation. Two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU: type I autoimmunity, also called autoallergy, which is mediated via IgE against various autoallergens, and type IIb autoimmunity, which is mediated predominantly via IgG directed against the IgE receptor FcεRI or FcεRI-bound IgE. Both mechanisms involve cross-linking of FcεRI and activation of downstream signaling pathways, and they may co-occur in the same patient. In addition, B-cell receptor signaling has been postulated to play a key role in CSU by generating autoreactive B cells and autoantibody production. A cornerstone of FcεRI and B-cell receptor signaling is Bruton tyrosine kinase (BTK), making BTK inhibition a clear therapeutic target in CSU. The potential application of early-generation BTK inhibitors, including ibrutinib, in allergic and autoimmune diseases is limited owing to their unfavorable benefit-risk profile. However, novel BTK inhibitors with improved selectivity and safety profiles have been developed and are under clinical investigation in autoimmune diseases, including CSU. In phase 2 trials, the BTK inhibitors remibrutinib and fenebrutinib have demonstrated rapid and sustained improvements in CSU disease activity. With phase 3 studies of remibrutinib ongoing, it is hoped that BTK inhibitors will present an effective, well-tolerated option for patients with antihistamine-refractory CSU, a phenotype that presents a considerable clinical challenge.
Topics: Humans; Agammaglobulinaemia Tyrosine Kinase; Chronic Urticaria; Signal Transduction; Mast Cells; Animals; Receptors, IgE; Basophils; Protein Kinase Inhibitors
PubMed: 38141832
DOI: 10.1016/j.jaci.2023.12.008