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There is strong evidence of an association between severe anaphylaxis, especially hymenoptera venom induced, and mast cell (MC) disorders. It has been thought that intrinsic abnormalities in MCs, including the presence of the activating KIT D816V mutation in mastocytosis or of genetic trait, hereditary alpha-tryptasemia, may influence susceptibility to severe anaphylaxis. This article evaluates the potential mechanisms leading to severe MC activation, as well as the differential diagnosis of and range of symptoms attributable to MC mediator release. Also, we offer a global classification for disorders related to MC activation.

The diagnosis of mast cell activation syndrome (MCAS) is defined by 3 criteria: (1) typical clinical signs and symptoms of acute, recurrent (episodic), and systemic mast cell activation (MCA); (2) increase in tryptase level to >20% + 2 ng/mL within 1-4 hours after onset of the acute crisis; and (3) response of MCA symptoms to antimediator therapy. Classification of MCAS requires highly sensitive and specific methodological approaches for the assessment of clonal bone marrow mast cells at low frequencies. The Spanish Network on Mastocytosis score has been used successfully as a predictive model for selecting MCAS candidates for bone marrow studies based on a high probability of an underlying clonal mast cell disorder. In this article, we propose a diagnostic algorithm and focus on the practical evaluation and management of patients with suspected MCAS. Key words: Anaphylaxis. Antimediator therapy. Mast cell activation syndrome. Mast cell mediator release–related symptoms. Tryptase.

Hymenoptera venom anaphylaxis is the most frequent cause of anaphylaxis and responsible for about 20% of all fatal anaphylaxis cases in adults. We report two cases of fatal hymenoptera venom anaphylaxis with undiagnosed underlying mastocytosis and review the risk factors for severe or fatal hymenoptera venom anaphylaxis, as well as the specificities of its association with mastocytosis. As hymenoptera venom allergic patients with underlying clonal mast cell disorder generally lack typical skin lesions of mastocytosis, its diagnosis can easily be missed, underscoring the importance and need for diagnostic strategies in order to correctly identify these patients. Predominant cardiovascular symptoms in the absence of urticaria or angioedema following an insect sting are suggestive of underlying clonal mast cell disorder, and should be distinguished from panic attack or vasovagal syncope. Similarly, an unexplained syncope or an "idiopathic" anaphylaxis might reveal mastocytosis or hereditary alpha-tryptasemia. Acute and basal serum tryptase measurements should always be integrated in the diagnostic work-up of an insect sting reaction or unexplained syncope or shock of any origin.

Background Pituitary adenylate cyclase-activating polypeptide-38 (PACAP38) and vasoactive intestinal polypeptide can provoke cluster headache attacks in up to half of cluster headache patients in their active phase. At present, it is unknown whether provoked attacks are mediated via calcitonin gene-related peptide or mast cell activation. Methods All enrolled patients with cluster headache were randomly allocated to receive a continuous infusion of either PACAP38 (10 pmol/kg/min) or vasoactive intestinal polypeptide (8 pmol/kg/min) over 20 min. We collected clinical data and measured plasma levels of calcitonin gene-related peptide and markers of mast cell activation (tryptase and histamine) at fixed time points: at baseline (T0), at the end of the infusion (T20), 10 min after the infusion (T30), and 70 min after the infusion (T90). Results Blood was collected from episodic cluster headache patients in active phase (n = 14), episodic cluster headache patients in remission (n = 15), and chronic cluster headache patients (n = 15). At baseline, plasma levels of calcitonin gene-related peptide, tryptase, and histamine were not different among the three study groups. Plasma levels of calcitonin gene-related peptide ( p = 0.7074), tryptase ( p = 0.6673), or histamine ( p = 0.4792) remained unchanged during provoked attacks compared to attack-free patients. Conclusion Cluster headache attacks provoked by either PACAP38 or vasoactive intestinal polypeptide were not accompanied by alterations of plasma calcitonin gene-related peptide, tryptase or histamine. The provoked attacks may not be mediated by calcitonin gene-related peptide or mast cell activation. Trial Registration: The study is registered at ClinicalTrials.gov (NCT03814226).

Summary Background Tezepelumab is a human monoclonal antibody that blocks the activity of thymic stromal lymphopoietin (TSLP), an epithelial cell-derived cytokine. In phase 2b and 3 studies, tezepelumab significantly reduced exacerbations versus placebo in patients with severe uncontrolled asthma, irrespective of baseline levels of type 2 inflammatory biomarkers. We investigated the mechanism of action of tezepelumab by assessing its effects on airway inflammatory cells, airway remodelling, and airway hyperresponsiveness. Methods CASCADE was an exploratory, double-blind, randomised, placebo-controlled, parallel-group, phase 2 study done in 27 medical centres in Canada, Denmark, Germany, the UK, and the USA. Adults aged 18–75 years with uncontrolled, moderate-to-severe asthma were randomly assigned (1:1) to receive tezepelumab 210 mg or placebo administered subcutaneously every 4 weeks for a planned 28 weeks, extended to up to 52 weeks if COVID-19-related disruption delayed participants' end-of-treatment assessments. Randomisation was balanced and stratified by blood eosinophil count. The primary endpoint was the change from baseline to the end of treatment in the number of airway submucosal inflammatory cells in bronchoscopic biopsy samples. Eosinophils, neutrophils, CD3+ T cells, CD4+ T cells, tryptase+ mast cells, and chymase+ mast cells were evaluated separately. This endpoint was also assessed in subgroups according to baseline type 2 inflammatory biomarker levels, including blood eosinophil count. Airway remodelling was assessed via the secondary endpoints of change from baseline in reticular basement membrane thickness and epithelial integrity (proportions of denuded, damaged, and intact epithelium). Exploratory outcomes included airway hyperresponsiveness to mannitol. All participants who completed at least 20 weeks of study treatment, had an end-of-treatment visit up to 8 weeks after the last dose of study drug, and had evaluable baseline and end-of-treatment bronchoscopies were included in the primary efficacy analysis. All participants who received at least one dose of study drug were included in the safety analyses. This study is registered with ClinicalTrials.gov, NCT03688074. Findings Between Nov 2, 2018, and Nov 16, 2020, 250 patients were enrolled, 116 of whom were randomly assigned (59 to tezepelumab, 57 to placebo). 48 in the tezepelumab group and 51 in the placebo group completed the study and were assessed for the primary endpoint. Treatment with tezepelumab resulted in a nominally significantly greater reduction from baseline to the end of treatment in airway submucosal eosinophils versus placebo (ratio of geometric least-squares means 0·15 [95% CI 0·05–0·41]; nominal p 0·10). In assessment of secondary endpoints, there were no significant differences between treatment groups in reticular basement membrane thickness and epithelial integrity. In an exploratory analysis, the reduction in airway hyperresponsiveness to mannitol was significantly greater with tezepelumab versus placebo (least-squares mean change from baseline in interpolated or extrapolated provoking dose of mannitol required to induce ≥15% reduction in FEV1 from baseline: tezepelumab 197·4 mg [95% CI 107·9 to 286·9]; placebo 58·6 mg [−30·1 to 147·33]; difference 138·8 [14·2 to 263·3], nominal p=0·030). Adverse events were reported in 53 (90%) patients in the tezepelumab group and 51 (90%) patients in the placebo group, and there were no safety findings of concern. Interpretation The improvements in asthma clinical outcomes observed in previous studies with tezepelumab are probably driven, at least in part, by reductions in eosinophilic airway inflammation, as shown here by reduced airway eosinophil counts regardless of baseline blood eosinophil count. Tezepelumab also reduced airway hyperresponsiveness to mannitol, indicating that TSLP blockade might have additional benefits in asthma beyond reducing type 2 airway inflammation. Funding AstraZeneca and Amgen.

[Objective]: Mast cell (MC) activation (MCA) defines the mechanism by which certain patients have symptoms owing to the effect of a wide range of mediators released from MCs upon their activation, when triggered by different stimuli. When these symptoms are severe and recurrent, the diagnosis of MCA syndrome (MCAS) might be considered. Here, we review the relevant aspects related to the pathogenesis of MCAS, with special emphasis on the prevalence and diagnostic relevance of KIT mutations., [Data Sources]: PubMed was searched between 1980 and 2021 using the following terms: mast cell activation syndromes, mast cell activation, anaphylaxis, KIT mutations, KIT D816V, indolent systemic mastocytosis, bone marrow mastocytosis, cutaneous mastocytosis, IgE anaphylaxis, and idiopathic anaphylaxis., [Study Selections]: Only articles published in English were selected based on their relevance to MCAS or severe and recurrent anaphylaxis., [Results]: MCAS can be classified as clonal MCAS and nonclonal MCAS depending on the presence vs absence of an underlying KIT mutation (mostly KIT D816V), respectively. In contrast to clonal MCAS in which MCA is associated with a primary MC disorder (ie, primary MCAS) such as mastocytosis or monoclonal MCAS, nonclonal MCAS can be secondary to known or unidentified triggers (ie, secondary and idiopathic MCAS, respectively)., [Conclusion]: The clinical heterogeneity and complexity of the molecular assays needed for the study of patients with MCAS might lead to misdiagnosis, particularly when patients are evaluated at nonspecialized centers. Thus, referral of patients having clinical manifestations suggestive of MCAS to reference centers on mastocytosis and MC diseases is strongly recommended., This work was supported by grants from the Instituto de Salud Carlos III (Madrid, Spain), Fondos Europeos de Desarrollo Regional (reference numbers: PI19/01166 and Centro de Investigación Biomédica en Red de Cáncer, CB16/12/00400), Fundación Española de Mastocitosis (Madrid, Spain; reference number: FEM2021-SAM), and Asociación Española de Pacientes con Mastocitosis y otras Enfermedades Relacionadas (Madrid, Spain; reference number: AEDM2019-SAM).

Dysregulated mast cell-mediated inflammation and/or activation have been linked to a number of human diseases, including asthma, anaphylaxis, chronic spontaneous urticaria, and mast cell activation syndromes. As a major mast cell granule protein, tryptase is a biomarker commonly used in clinical practice to diagnose mast cell-associated disorders and -mediated reactions, but its mechanistic roles in disease pathogenesis remains incompletely understood. Here, we summarize recent advances in the understanding of human tryptase genetics and the effects that different genetic composition may have on the quaternary structure of tetrameric mature tryptases. We also discuss how these differences may impact clinical phenotypes including allergic inflammation, immediate hypersensitivity, and others seen in patients with mast cell-associated disorders. With the increased application of next-generation sequencing, we foresee that human genetic approaches will be a major focus of understanding human tryptase functions in various human mast cell disorders and in new therapeutic development.

Mast cells (MCs) are immune cells that are distributed in all tissues throughout the body, and their cytoplasm is rich in granules containing histamine and tryptase. When MCs recognize antigens through IgE bound to FceRI, they release these mediators by degranulation. Because degranulation induces various type I allergic reactions, such as anaphylactic shock and hay fever, elucidation of the control mechanism of degranulation is important to the development of a therapeutic strategy for allergic diseases. It is known that the antigen-induced degranulation response is fine-tuned by various humoral factors via the activation of G protein-coupled receptors. We found that extracellular ATP enhanced antigen-dependent and -independent MC degranulation via activation of ionotropic P2X4 receptors. P2X4 receptor activation itself had no effect on MC degranulation, but significantly enhanced antigen-triggered degranulation. Stimulation of the P2X4 receptor potentiated the FceRI-mediated tyrosine kinase signaling cascade. In addition to antigen-induced responses, P2X4 receptor signaling also affected antigen-independent MC responses. Thus, co-stimulation of ATP and Gi-coupled receptor agonists, such as prostaglandin E2 (PGE2) and adenosine, resulted in synergistic degranulation. The significance of P2X4 receptor signaling in allergic and inflammatory responses in vivo was confirmed by impaired responses of antigen-induced passive anaphylaxis and PGE2-induced increases in vascular permeability in P2rx4 knockout mice compared to that of wild-type mice. These results suggest that the P2X4 receptor is a potential therapeutic target for both antigen-dependent and -independent allergic reactions.

Degeneration of motor neurons, glial cell reactivity, and vascular alterations in the CNS are important neuropathological features of amyotrophic lateral sclerosis (ALS). Immune cells trafficking from the blood also infiltrate the affected CNS parenchyma and contribute to neuroinflammation. Mast cells (MCs) are hematopoietic-derived immune cells whose precursors differentiate upon migration into tissues. Upon activation, MCs undergo degranulation with the ability to increase vascular permeability, orchestrate neuroinflammation and modulate the neuroimmune response. However, the prevalence, pathological significance, and pharmacology of MCs in the CNS of ALS patients remain largely unknown. In autopsy ALS spinal cords, we identified for the first time that MCs express c-Kit together with chymase, tryptase, and Cox-2 and display granular or degranulating morphology, as compared with scarce MCs in control cords. In ALS, MCs were mainly found in the niche between spinal motor neuron somas and nearby microvascular elements, and they displayed remarkable pathological abnormalities. Similarly, MCs accumulated in the motor neuron-vascular niche of ALS murine models, in the vicinity of astrocytes and motor neurons expressing the c-Kit ligand stem cell factor (SCF), suggesting an SCF/c-Kit-dependent mechanism of MC differentiation from precursors. Mechanistically, we provide evidence that fully differentiated MCs in cell cultures can be generated from the murine ALS spinal cord tissue, further supporting the presence of c-Kit+ MC precursors. Moreover, intravenous administration of bone marrow-derived c-Kit+ MC precursors infiltrated the spinal cord in ALS mice but not in controls, consistent with aberrant trafficking through a defective microvasculature. Pharmacological inhibition of c-Kit with masitinib in ALS mice reduced the MC number and the influx of MC precursors from the periphery. Our results suggest a previously unknown pathogenic mechanism triggered by MCs in the ALS motor neuron-vascular niche that might be targeted pharmacologically. Supplementary Information The online version contains supplementary material available at 10.1186/s40478-021-01241-3.

Paired acute and baseline serum or plasma tryptase sampling and determination have recently been included as a mechanistic approach in the diagnostic and management guidelines of perioperative immediate hypersensitivity and anaphylaxis. The timing of this paired sampling is clearly defined in international consensus statements, with the optimal window for acute tryptase sampling between 30 minutes and 2 hours after the initiation of symptoms, whereas baseline tryptase should be measured in a sample collected before the event (preop) or at least 24 hours after all signs and symptoms have resolved. A transient elevation of the acute tryptase level greater than [2 D (1.2 3 baseline tryptase level)] supports the involvement and activation of mast cells. Here, we provide the clinical, pathophysiological, and technical rationale for the procedure and interpretation of paired acute and baseline tryptase. Clinical examples, upto-date knowledge of hereditary alpha-tryptasemia as a frequent cause of baseline tryptase of 7 mg/L and higher, mastocytosis, other clonal myeloid disorders, cardiovascular or renal failure, and technical improvements resulting in continued lowering of the 95th percentile value are discussed. Clues for improved management of perioperative immediate hypersensitivity and anaphylaxis include (1) sustained dissemination and implementation of updated guidelines; (2) preoperative sample storage for deferred analysis; (3) referral for thorough allergy investigation, screening for mast cellerelated disorders, and recommendations for future anesthetic procedures; and (4) sustained collaboration between anesthesiologists, immunologists, and allergists. (C) 2021 American Academy of Allergy, Asthma & Immunology

Hereditary alpha-tryptasemia (HαT) is an autosomal dominant genetic trait found in 4% to 6% of the general population and defined by excess copies of alpha-tryptase at TPSAB1. Elevated basal serum tryptase (sBT >8 ng/mL) is a defining feature of HαT and appears to result from increased pro-alpha-tryptase synthesis and secretion rather than mast cell activation. It is estimated that approximately one-third of individuals with HαT have associated symptoms, including cutaneous, gastrointestinal, atopic, musculoskeletal, autonomic, and neuropsychiatric manifestations. HαT is found at a disproportionately high rate in systemic mastocytosis and idiopathic anaphylaxis, and is a modifying factor that independently increases the incidence and severity of anaphylaxis. The varied phenotypes associated with HαT may, in part, result from coinheritance of other genetic variants, increased expression of α-/s-tryptase heterotetramers, and/or overexpression of pro-alpha-tryptase, although further studies are needed. There is an accurate diagnostic test available to confirm HαT in patients that can be used in combination with sBT to help risk-stratify individuals in whom bone marrow biopsy is being considered. There is no specific treatment for symptoms associated with HαT, and management is focused on controlling clinical manifestations with mast cell mediator antagonists, aspirin, inhalers, epinephrine, omalizumab, and involvement of other specialists.

Background Mast cells (MCs) are known to contribute to both acute and chronic inflammation. Bronchial epithelial cells are the first line of defence against pathogens and a deficient anti-viral response has been suggested to play a role in the pathogenesis of asthma exacerbations. However, effects of MC mediators on bronchial epithelial immune response have been less studied. The aim of this study is to investigate the direct effects of stimulation with MC proteases, tryptase and chymase, on inflammatory and anti-viral responses in human bronchial epithelial cells (HBECs). Method Cultured BEAS-2b cells and primary HBECs from 3 asthmatic patients were stimulated with tryptase or chymase (0.1 to 0.5 μg/ml) for 1, 3, 6 and 24 h. To study the effects of MC mediators on the anti-viral response, cells were stimulated with 10 μg/ml of viral mimic Poly (I:C) for 3 and 24 h following pre-treatment with 0.5 μg/ml tryptase or chymase for 3 h. Samples were analysed for changes in pro-inflammatory and anti-viral mediators and receptors using RT-qPCR, western blot and Luminex. Results Tryptase and chymase induced release of the alarmin ATP and pro-inflammatory mediators IL-8, IL-6, IL-22 and MCP-1 from HBECs. Moreover, tryptase and chymase decreased the expression of E-cadherin and zonula occludens-1 expression from HBECs. Pre-treatment of HBECs with tryptase and chymase further increased Poly (I:C) induced IL-8 release at 3 h. Furthermore, tryptase significantly reduced type-I and III interferons (IFNs) and pattern recognition receptor (PRR) expression in HBECs. Tryptase impaired Poly (I:C) induced IFN and PRR expression which was restored by treatment of a serine protease inhibitor. Similar effects of tryptase on inflammation and anti-viral responses were also confirmed in primary HBECs from asthmatic patients. Conclusion MC localization within the epithelium and the release of their proteases may play a critical role in asthma pathology by provoking pro-inflammatory and alarmin responses and downregulating IFNs. Furthermore, MC proteases induce downregulation of epithelial junction proteins which may lead to barrier dysfunction. In summary, our data suggests that mast cells may contribute towards impaired anti-viral epithelial responses during asthma exacerbations mediated by the protease activity of tryptase.

Tuberculosis (TB) is still a major worldwide health threat and primarily a lung disease. The innate immune response against Mycobacterium tuberculosis (Mtb) is orchestrated by dendritic cells, macrophages, neutrophils, natural killer cells and apparently mast cells (MCs). MCs are located at mucosal sites including the lungs and contribute in host-defence against pathogens, but little is known about their role during Mtb infection. This study investigates the location and characteristics of MCs in TB lesions to assess their contribution to TB pathology. To this purpose, number, location and phenotype of MCs was studied in 11 necropsies of pulmonary TB and 3 necropsies of non-TB infected lungs that were used as controls. MCs were localised at pneumonic areas, in the granuloma periphery and particularly abundant in fibrotic tissue. Furthermore, MCs displayed intracellular Mtb and IL-17A and TGF-β immunostaining. These findings were validated by analysing, post-mortem lung tissue microarrays from 44 individuals with pulmonary TB and 25 control subjects. In affected lungs, increased numbers of MCs expressing intracellularly both tryptase and chymase were found at fibrotic sites. Altogether, our data suggest that MCs are recruited at the inflammatory site and that actively produce immune mediators such as proteases and TGF-β that may be contributing to late fibrosis in TB lesions.

Suicidal ingestion of food which the victim is aware they are allergic to is an exceptional occurrence in the forensic field. To the best of our knowledge, no cases of suicidal food anaphylaxis have been reported to date. Therefore we present the first case described in the literature. A 30-year-old prisoner was found dead inside his cell with the remains of a peach remains next to his body, and a handwritten farewell note in his pocket. The autopsy revealed only non-specific findings, while laboratory investigations (serological, toxicological, histological, and immunohistochemical) played a pivotal role in determing the cause and manner of death. In particular, a high titer of both total and specific IgE antibodies was detected, as well as an increase of the tryptase level in cadaveric blood. Moreover, a massive concentration of salicylates was measured in the gastric contents. Microscopically, cellular residues characterized by a vegetal structure were observed in the gastric contents and elements suggestive of mast cells were detected in the glottis, lungs, and myocardium. The immunohistochemical investigation with anti-CD117 and anti-tryptase antibodies showed positivity for mast cells, some of which appeared degranulated. Such findings were entirely consistent with an acute systemic anaphylactic reaction triggered by allergy. Therefore, the prisoner’s death was attributed to self-induced food anaphylaxis caused by the ingestion of peaches. This conclusion was achieved based only on circumstantial data, anamnestic information, autopsy findings, and multiple laboratory results. This integrated approach should be used to pursue a post-mortem diagnosis of anaphylaxis.

Background: Many patients report questionable drug hypersensitivity reactions (DHR) to betalactam antibiotics. A workup is required for objectivation. Direct drug provocation tests (DPTs) omitting a prior allergy workup are increasingly recommended as the primary diagnostic approach. However, apart from the risk of severe side effects, DPTs often are a scarce resource in overloaded healthcare-systems. We investigated how many cases can be solved by drug-specific history, drug-specific IgE, and skin tests obviating the need for DPT. Methods: We conducted a chart review in a retrospective cohort of 932 patients in an allergy outpatient centre from 2016 to 2017. Patients had been submitted to drug-specific history and specific IgE-, skin prick-, intradermal- and patch-tests with early and late readings with a series of penicillins and cephalosporins but DPTs were no option. Results: Overall, positive in vitro and/or skin tests were found in 96/932 (10.3%) patients. Drug-specific IgE was detected in 40/932 (4.3%) patients, 61/787 (7.8%) patients had positive skin tests. In vitro tests to Pencillin V showed the highest rate of positivity 24/479 (5.0%) and early readings of ampicillin the highest amongst the skin tests (3/49, 6.1%). Immediate skin tests were more often positive than delayed ones (75:45). The combination of all parameters including drug-specific history solved 346/932 (37.1%) cases while 586/932 (62.9%) remained unresolved. Self-reported DHR could be less often confirmed in females and young children (p

Mastocytosis is a rare group of disorders characterized by abnormal accumulation of mast cells in the skin, bone marrow, and internal organs. In particular, patients with systemic mastocytosis are at an increased risk of frequent and severe episodes of anaphylaxis. Hymenoptera venom allergy is the most common trigger of anaphylaxis in these patients. Immunotherapy is an effective and safe therapy recommended for patients with mastocytosis and venom allergy. Although this therapy can be administered according to different protocols, the preferred protocol for patients with mastocytosis remains unclear. Systemic side effects can occur, in particular, during the up-dosing phase of immunotherapy, making progression to the maintenance phase of therapy challenging. This case report presents the diagnosis and ultrarush immunotherapy process ended with anaphylaxis of a 33-y-old male patient with Apis mellifera allergy.

Haemolysis is reported to be an artefact that may alter post-mortem tryptase levels. However, previous studies did not sample peripheral blood using newly standardised methods. Recent studies have shown that some previously recognised peri- and post-mortem confounders can be muted by careful sample collection with first clamping and then sampling the femoral vein. This prospective study investigated the relationship between the degree of haemolysis of the blood samples and femoral vein post-mortem tryptase levels when sampled using this recommended method. Seventy consecutive post-mortem tryptase levels in non-anaphylactic deaths were compared to the degree of haemolysis of these samples, and results showed no significant correlation between them. The mean post-mortem tryptase level was 9.5 μg/L. This study demonstrated that the effects of haemolysis on femoral vein post-mortem tryptase was negligible when the blood was sampled using the recommended sampling method. Future studies on post-mortem tryptase as well as other typically used blood markers in forensics are recommended to adopt this method of blood sampling in routine practice.

Background There is no trial to make a diagnostic tool of allergic rhinitis (AR) utilizing biomarkers from nasal fluid. Base on previous studies, we selected following five biomarkers in nasal fluids that represent the characteristics of allergic reactions: tryptase, eosinophil cationic protein (ECP), interleukin 5 (IL-5), Clara cell protein 16 (CC16) and CC16-to-albumin ratio. Objective This study aimed to identify biomarkers in nasal discharge that may be used in biosensors to diagnose AR as an additional diagnostic tool. Methods Patients showed rhinorrhea and tested positive on allergic skin and specific immunoglobulin E (IgE) tests were included in the AR group. The non-AR group included individuals no dominant nasal symptoms and tested negative on allergy tests. Nasal lavage fluid samples were collected from all participants. Biomarkers in the samples were quantified using enzyme-linked immunosorbent assay. Results Forty-five patients with AR and 28 non-AR subjects were enrolled in this study. Comparing the concentrations of biomarkers, the concentrations of tryptase and IL-5 were significantly higher in the AR group than in the NAR group. And CC16 level and CC16-to-albumin ratio were significantly lower in the AR group. In the combination of tryptase or CC16-to-albumin ratio, the sensitivity was 90.7% and the specificity was 64.3% ( p = 0.013). Conclusion The combination of “tryptase or CC16-to-albumin” could be used as a screening tool for AR. Although this diagnostic method could not replace conventional diagnostic tools, we could consider the method we proposed as an additional screening tool for patients who could not undergo allergy tests.

Mastocytosis is a hematopoietic neoplasm characterized by expansion of KIT D816V-mutated clonal mast cells in various organs and severe or even life-threatening anaphylactic reactions. Recently, hereditary α-tryptasemia (HαT) has been described as a common genetic trait with increased copy numbers of the α-tryptase encoding gene, TPSAB1, and associated with an increased basal serum tryptase level and a risk of mast cell activation. The purpose of our study was to elucidate the clinical relevance of HαT in patients with mastocytosis. TPSAB1 germline copy number variants were assessed by digital polymerase chain reaction in 180 mastocytosis patients, 180 sex-matched control subjects, 720 patients with other myeloid neoplasms, and 61 additional mastocytosis patients of an independent validation cohort. α-Tryptase encoding TPSAB1 copy number gains, compatible with HαT, were identified in 17.2% of mastocytosis patients and 4.4% of the control population (P < .001). Patients with HαT exhibited higher tryptase levels than patients without HαT (median tryptase in HαT+ cases: 49.6 ng/mL vs HαT− cases: 34.5 ng/mL, P = .004) independent of the mast cell burden. Hymenoptera venom hypersensitivity reactions and severe cardiovascular mediator-related symptoms/anaphylaxis were by far more frequently observed in mastocytosis patients with HαT than in those without HαT. Results were confirmed in an independent validation cohort. The high prevalence of HαT in mastocytosis hints at a potential pathogenic role of germline α-tryptase encoding TPSAB1 copy number gains in disease evolution. Together, our data suggest that HαT is a novel emerging robust biomarker in mastocytosis that is useful for determining the individual patient´s risk of developing severe anaphylaxis.

Introduction: Mast cells and their major protein, the serine proteinase tryptase, can be involved in cutaneous photodamage and carcinogenesis. The serum test of tryptase (S-tryptase) measures total tryptase protein (active tryptase and inactive protryptases), and S-tryptase is elevated in a variety of diseases, for example, in mastocytosis and α-tryptasemia. Objectives: The objective of this study is to study whether S-tryptase is a marker of cutaneous photodamage and carcinogenesis. Methods: Adult subjects (n = 399, aged 21–79) evaluated to be at risk for skin cancers were recruited at the dermatological policlinic and examined for photodamage severity, mole count, actinic keratoses (AKs), skin cancers, and immunosuppression (IS). A blood sample was analyzed for S-tryptase using the ImmunoCAP® Tryptase fluoroenzymeimmunoassay. Results: There was no difference in S-tryptase between non-IS (n = 321) and IS (n = 78) subjects or between genders. S-tryptase correlated slightly to photodamage and AKs in 321 non-IS subjects, and this association can be related, in part, to the age of subjects. In 34 subjects, S-tryptase was elevated (≥13.5 ng/mL), and in 20 males, but not in 14 females, the photodamage level was significantly (p = 0.031) more severe than in 179 males with normal S-tryptase. In contrast, there were more frequently subjects (n = 12) with past or present skin cancer (basal or squamous cell carcinoma or melanoma) in 14 females with elevated S-tryptase than in 186 female controls. So far, no explanation has been found for the elevated S-tryptase. Conclusion: There are significant associations between elevated S-tryptase and skin carcinogenesis, but the molecular mechanisms are unclear and gender differences can exist.

Epithelial damage and increase of intraepithelial mast cells (MC) are characteristics of asthma. The role of MC mediator tryptase and the protease-activated receptor-2 (PAR2) on epithelial wound healing is not fully investigated. Stimulation of bronchial epithelial cells (BECs) with tryptase promoted gap closure, migration and cellular speed compared to controls. Stimulated BECs had higher expression of migration marker CD151 compared to controls. Proliferation marker KI67 was upregulated in tryptase-stimulated BECs compared to controls. Treatment with PAR2 antagonist I-191 reduced gap closure, migration and cell speed compared to BECs stimulated with tryptase. We found that tryptase enhances epithelial wound healing by increased migration and proliferation, which is in part regulated via PAR2. Our data suggest that tryptase might be beneficial in tissue repair under baseline conditions. However, in a pathological context such as asthma with increased numbers of activated MCs, it might lead to epithelial remodeling and loss of function.

Objectives The 2019 Workshop of the Society for Hematopathology/European Association for Haematopathology received and reviewed cases covering the spectrum of mastocytosis and related diseases, including morphologic mimics, focusing on recent updates and relevant findings for pathologists. Methods The workshop panel reviewed 99 cases of cutaneous and systemic mastocytosis (SM) and SM and associated hematologic neoplasms (SM-AHN). Results Despite a common theme of KIT mutation (particularly D816V), mastocytosis is a heterogeneous neoplasm with a wide variety of presentations. This spectrum, including rare subtypes and extramedullary organ involvement, is discussed and illustrated by representative cases. Conclusions In the age of targeted treatment aimed at KIT, the accurate diagnosis and classification of mastocytosis has major implications for therapy and further interventions. Understanding the clinical, pathologic, and genetic findings of mastocytosis is crucial for selecting the proper tests to perform and subsequent arrival at a correct diagnosis in this rare disease.

We studied the effect of bone marrow autotransplantation on the morphofunctional properties and numerical population of mast cells. The experiments were performed on 4-monthold male mice. The animals received an injection of a suspension of bone marrow obtained from the femoral epiphyses of these animals into the caudal vein. In 40 min and 2 h after autotransplantation, the number of tryptase-positive mast cells increased by 1.1 times. The formation of groups of mast cells near erythroid-neutrophil islets and near blood vessels was observed. The proportion of metachromatic mast cells significantly increased. By the degree of mast cells degranulation, we detected non-degranulated up to 48.0±1.4% (vs 55.2±1.2% in intact mice) and moderately degranulated mast cells 22.0±1.2% (vs 18.2±0.9% in intact mice); the percentage of actively degranulated cells was 10.0±0.8% (vs 3.6±0.9% in intact mice; p

Extensive activation of mast cells is the major switch that triggers systemic anaphylaxis, resulting in the subsequent release of anaphylactic mediators into circulation. We previously demonstrated that rapid changes in oxygen tension lead to mast cell degranulation, and the released tryptase triggers retinal angiogenesis in a murine oxygen-induced retinopathy model. However, whether a rapid shift from hyperoxia to normoxia (relative hypoxic stress) is a risk factor for systemic anaphylaxis remains unknown. In this study, we demonstrated that the relative hypoxia stress induces systemic mast cell activation via transient receptor potential ankyrin 1 (TRPA1) channels, which immediately leads to hypothermia and increased vascular permeability in adult mice. Although mast cell–deficient or TRPA1-deficient mice did not exhibit anaphylactic symptoms following a rapid sift to normoxia, preinjection with bone marrow–derived cultured mast cells (BMCMCs) derived from wild-type TRPA1-expressing mice restored anaphylactic responses. In addition, we found that the rapid reductions in oxygen tension in a culture atmosphere triggered the degranulation of BMCMCs derived from wild-type TRPA1-expressing mice but not that of BMCMCs derived from TRPA1-deficient mice. In human LAD2 mast cells, the relative hypoxic stress led to the degranulation, which was suppressed by the addition of a TRPA1 inhibitor. Gradual reductions from hyperoxia to normoxia led to no anaphylactic symptoms. Our results demonstrated that TRPA1-triggered mast cell degranulation is a novel pathway that induces anaphylactic shock without Ag–Ab reactions. These findings introduce a potential role for oxygen in inducing mast cell–dependent anaphylaxis and highlight the need to reconsider chronic pure oxygen therapy for anoxic diseases.

Mast cells (MCs) play a pivotal role in the hypersensitivity reaction by regulating the innate and adaptive immune responses. Humans have two types of MCs. The first type, termed MCTC, is found in the skin and other connective tissues and expresses both tryptase and chymase, while the second, termed MCT, which only expresses tryptase, is found primarily in the mucosa. MCs induced from human adult-type CD34+ cells are reported to be of the MCT type, but the development of MCs during embryonic/fetal stages is largely unknown. Using an efficient coculture system, we identified that a CD34+c-kit+ cell population, which appeared prior to the emergence of CD34+CD45+ hematopoietic stem and progenitor cells (HSPCs), stimulated robust production of pure Tryptase+Chymase+ MCs (MCTCs). Single-cell analysis revealed dual development directions of CD34+c-kit+ progenitors, with one lineage developing into erythro-myeloid progenitors (EMP) and the other lineage developing into HSPC. Interestingly, MCTCs derived from early CD34+c-kit+ cells exhibited strong histamine release and immune response functions. Particularly, robust release of IL-17 suggested that these early developing tissue-type MCTCs could play a central role in tumor immunity. These findings could help elucidate the mechanisms controlling early development of MCTCs and have significant therapeutic implications.

Postmortem tryptase is a commonly used biochemical test to aid in the diagnosis of fatal anaphylaxis, which is currently recommended to be sampled from peripheral (femoral) veins because of a research showing comparatively elevated levels from central blood sources. Previous studies have used nonstandardized or nondocumented sampling methods; however, more recent research demonstrates that tryptase levels may vary depending on the sampling method. This study used the recommended sampling method of aspirating the femoral vein after clamping and compared in a pairwise comparison with aspiration of central venous and arterial blood sources (inferior vena cava and aorta) in 2 groups of 25 nonanaphylactic deaths. We found no statistically significant differences in postmortem tryptase between central and femoral vein blood; however, sporadic outliers in central blood (particularly aortic blood reaching levels above documented cutoffs for fatal anaphylaxis) were observed. Our findings provide evidence for the existing recommendations that femoral vein blood remains the preferred sample for postmortem tryptase over central blood.

Background Patients with mastocytosis have an increased risk for severe anaphylaxis, particularly to hymenoptera venoms. These patients may also develop more often systemic hypersensitivity reactions to certain foods. However, this issue has not been systematically investigated. Objective We aimed to determine prevalence and severity of food-related hypersensitivity (FH) reactions among patients with clonal mast cell disorders (CMD). Methods A retrospective study was conducted among 204 (≥ 18 years) consecutive patients who presented with confirmed CMD (170 with mastocytosis and 34 with monoclonal mast cell activation syndrome [MMAS]). All patients underwent thorough allergy work-up where self-reported FH-reactions were evaluated. Results The prevalence of self-reported FH was 20.6%. The frequency of immunologically mediated reactions was uncommon, as only 3.4% were confirmed by relevant history and IgE-sensitization. Among patients with FH, five had severe anaphylaxis corresponding to an overall prevalence of 2.5%. Most symptoms were restricted to skin (86%), followed by gastrointestinal tract (45%); similar to symptoms that occur in mastocytosis patients also without food-intake. Nuts, spicy foods, seafood and alcohol were the most common incriminated elicitors. There was no significant difference between the groups regarding age, gender, atopic status or IgE levels. Conclusion Anaphylaxis from foods in mastocytosis does exist and is severe, although foods are less frequent elicitor than insect venoms. Further, the frequency of overall FH-reactions is comparable to the general population and most reactions are mild, non-allergic and unconfirmed. Consequently, our results do not support the elimination of any diet in CMD patients without history of FH.

Aim: Tryptase is a tetrameric trypsin-like serine protease contained within the secretory granules of mast cells and is an important mediator of allergic inflammatory responses in respiratory diseases. Detection of active tryptase in the airway may provide important information about asthma and other respiratory diseases. Materials & Methods: An activity based probe has been incorported within an immunoassay to allow for measurement of active tryptase in human tissues. Results: A specific Simoa immunoassay to measure active tryptase in nasosorption samples was developed and qualified using an activity-based probe label and a specific antitryptase capture antibody. Conclusion: The assay was capable of measuring active tryptase in human samples, which will enable evaluation of the role of tryptase proteolytic activity in human disease.

Background Mast cells (MCs) have a profound impact on allergic asthma. Under such conditions, MCs undergo degranulation, resulting in the release of exceptionally large amounts of MC-restricted proteases. However, the role of these proteases in asthma is only partially understood. Objectives We sought to test our hypothesis that MC proteases can influence the functionality of human lung fibroblasts (HLFs). Methods Primary HLFs were treated with MC chymase or tryptase, followed by assessment of parameters related to fibroblast function. Results HLFs underwent major morphologic changes in response to chymase, showing signs of cellular contraction, but were refractory to tryptase. However, no effects of chymase on HLF viability or proliferation were seen. Chymase, but not tryptase, had a major impact on the output of extracellular matrix–associated compounds from the HLFs, including degradation of fibronectin and collagen-1, and activation of pro–matrix metalloprotease 2. Further, chymase induced the release of various chemotactic factors from HLFs. In line with this, conditioned medium from chymase-treated HLFs showed chemotactic activity on neutrophils. Transcriptome analysis revealed that chymase induced a proinflammatory gene transcription profile in HLFs, whereas tryptase had minimal effects. Conclusions Chymase, but not tryptase, has a major impact on the phenotype of primary airway fibroblasts by modifying their output of extracellular matrix components and by inducing a proinflammatory phenotype.

In the current classification of the World Health Organization (WHO), bone marrow mastocytosis (BMM) is a provisional variant of indolent systemic mastocytosis (ISM) defined by bone marrow involvement and absence of skin lesions. However, no additional diagnostic criteria for BMM have been proposed. Within the registry dataset of the European Competence Network on Mastocytosis, we compared characteristics and outcomes of 390 patients with BMM and 1175 patients with typical ISM. BMM patients were significantly older, predominantly male, had lower tryptase and lower burden of neoplastic mast cells, and displayed a higher frequency of allergic reactions, mainly triggered by Hymenoptera, than patients with typical ISM. The estimated 10-year progression-free survival of BMM and typical ISM was 95.9% and 92.6%, respectively. In BMM patients defined by WHO-based criteria, the presence of one B-Finding and tryptase level ≥125 ng/mL were identified as risk factors for progression in multivariate analyses. BMM patients without any of these risk factors were found to have better progression-free survival (p < 0.05) and better overall survival (p < 0.05) than other ISM patients. These data support the proposal to define BMM as a separate SM variant characterized by SM criteria, absence of skin lesions, absence of B-Findings, and tryptase levels

Type 2 cytokine responses promote parasitic immunity and initiate tissue repair; however, they can also result in immunopathologies when not properly restricted. Although basophilia is recognized as a common feature of type 2 inflammation, the roles basophils play in regulating these responses are unknown. Here, we demonstrate that helminth-induced group 2 innate lymphoid cell (ILC2) responses are exaggerated in the absence of basophils, resulting in increased inflammation and diminished lung function. Additionally, we show that ILC2s from basophil-depleted mice express reduced amounts of the receptor for the neuropeptide neuromedin B (NMB). Critically, NMB stimulation inhibited ILC2 responses from control but not basophil-depleted mice, and basophils were sufficient to directly enhance NMB receptor expression on ILC2s. These studies suggest that basophils prime ILC2s to respond to neuron-derived signals necessary to maintain tissue integrity. Further, these data provide mechanistic insight into the functions of basophils and identify NMB as a potent inhibitor of type 2 inflammation.

Idiopathic anaphylaxis is a condition caused by paroxysmal episodes of sudden-onset multiorgan involvement variably including laryngeal edema, urticaria, bronchoconstriction, dyspnea, hypoxia, abdominal pain, nausea, vomiting, diarrhea, and hypotension. Rarely, the episodes can lead to cardiovascular collapse and death in the absence of a clear trigger, especially in the presence of other cardiovascular comorbidities. Elevated mast cell mediators such as tryptase and histamine have been reported during episodes, and mast cells are considered the primary cells responsible for driving anaphylaxis in humans. Basophils also secrete histamine and LTC4 when activated and theoretically can contribute to symptoms. As our understanding of mast cell disorders continue to grow, the classification for these disorders evolves. The purpose of this article was 2-fold: to review the epidemiology, clinical manifestations, and diagnosis of idiopathic anaphylaxis and to discuss the classification of idiopathic anaphylaxis within the broader context of mast cell activation disorders.

Excessive fatty acids and glucose uptake support the infiltration of adipose tissue (AT) by a variety of immune cells including neutrophils, pro-inflammatory M1 macrophages, and mast cells (MCs). These cells promote inflammation by releasing pro-inflammatory mediators. The involvement of MCs in AT biology is supported by their accumulation in the AT of obese individuals along with significantly higher serum levels of MC-derived tryptase. AT-resident MCs under the influence of locally derived adipokines such as leptin become activated and release pro-inflammatory cytokines including TNFα that worsens the inflammatory state. MCs support angiogenesis in AT by releasing chymase and inducing preadipocyte differentiation and also the proliferation of adipocytes through 15-deoxy-delta PGJ2/PPARγ interaction. Additionally, they contribute to the remodeling of the AT extracellular matrix (ECM) and play a role in the recruitment and activation of leukocytes. MC degranulation has been linked to brown adipocyte activation, and evidence indicates an important link between MCs and the appearance of BRITE/beige adipocytes in white AT. Cell crosstalk between MCs and AT-resident cells, mainly adipocytes and immune cells, shows that these cells play a critical role in the regulation of AT homeostasis and inflammation.

Mast cells contain an abundance of tryptase, and preclinical models have shown elevated serum mast cell tryptase (SMCT) in the setting of posttraumatic joint contractures. Therefore, SMCT emerged as a potential biomarker to help recognize patients with more severe injuries and a higher likelihood of developing contractures. The objective of this study is to assess SMCT levels in participants with varying severity of elbow fractures and/or dislocations. A prospective cohort including 13 participants with more severe injuries that required an operation and 28 participants with less severe injuries managed nonoperatively were evaluated. A control group of eight individuals without elbow injuries was also evaluated. The SMCT levels were measured using an enzyme-linked immunosorbent assay kit specific for human mast cell tryptase. A one-way analysis of variance and Tukey's Honest Significance test was used to assess for statistical significance among and between the three groups. The average time from injury to the collection of the blood samples was 4 ± 2 days. Highly significant differences were identified between the operative, nonoperative, and control groups (P = .0005). In the operative group, SMCT levels were significantly higher than the nonoperative group (P = .0005) and the control group (P = .009), suggesting a correlation between SMCT levels and injury severity. There was no statistically significant difference in SMCT levels between the nonoperative and control groups. The SMCT levels were elevated in participants with acute elbow injuries requiring operative intervention, suggesting that SMCT levels were higher in injuries regarded as more severe.

Mast cells are essential in mediating inflammatory processes. When activated, mast cells can rapidly release characteristic granules and various mediators into the interstitium. Tryptase (TPS) and β-hexosaminidase (HEXB) are typical protease mediators stored in granules and released upon activation. They have been recognized as important biomarkers of anaphylaxis, and the released level is associated with the severity of allergic reactions. In this study, a sensitive, accurate, and selective liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneously quantifying the two biomarkers was developed and validated in LAD2 cell culture supernatant, and P

Background: Given our previous findings that low intratumoral and high extratumoral mast cell numbers are associated with higher risk of biochemical recurrence after radical prostatectomy, we now assessed this relationship with race and the development of metastases. Methods: We stained for mast cell tryptase via IHC and fluorescent immunolabeling in 885 men across multiple tissue microarray sets designed to assess biomarkers in association with race and prostate cancer outcomes (median follow-up, 7.0 years). Results: Intratumoral and extratumoral mast cell counts were significantly lower in tissues from African-American compared with European-American men, but not within strata of cancer grade. There was no association between mast cell counts and ERG positivity, PTEN loss, or TP53 missense mutation. Higher minimum extratumoral mast cells were associated with an increased risk of biochemical recurrence [comparing highest with lowest tertiles: HR, 1.61; 95% confidence interval (CI), 1.12–2.29; P trend = 0.01]; this pattern was similar among European-American and African-American men and by grade of disease. There was no significant association between minimum intratumoral mast cell count and biochemical recurrence, overall or within strata of race and grade. Finally, high minimum number of extratumoral mast cells was associated with prostate cancer metastases (comparing highest with lowest tertiles: HR, 2.12; 95% CI, 1.24–3.63; P trend = 0.01). Conclusions: High extratumoral mast cell numbers are associated with biochemical recurrence and the development of metastases after radical prostatectomy. Impact: Higher numbers of benign tissue mast cells are associated with a higher risk of adverse outcomes after radical prostatectomy, including metastatic prostate cancer.

One of the most important blood tests in the field of allergy, mast cell tryptase has numerous diagnostic uses, particularly for anaphylactic reactions and for the diagnosis of mastocytosis. However, there are numerous other non-anaphylactic conditions where clinicians may see elevated serum tryptase (hypertryptasemia) and the practicing clinician ought to be aware of these important differential diagnoses. Such conditions include systemic mastocytosis, hematological malignancies, and chronic kidney disease. This article provides a comprehensive, updated summary on the variety of non-anaphylactic conditions where hypertryptasemia may be seen.

Postmortem tryptase is a useful biochemical test to aid the diagnosis of anaphylaxis. Multiple perimortem and postmortem factors have been documented to cause an elevation in postmortem tryptase level. One factor that was recently recognized to have an impact on postmortem tryptase level is correct sampling technique. A recent study recommended aspirating blood samples from a clamped femoral/external iliac vein to be used for reliable postmortem tryptase analysis. This study sampled 120 consecutive nonanaphylactic deaths in which all the peripheral bloods were sampled as recommended. Postmortem interval, resuscitation, different nonanaphylactic causes of death, sex, and age did not show any statistical significant relation to postmortem tryptase level in Student t test, Pearson correlation, and univariate and multivariate analyses. The mean (SD) postmortem tryptase level was 8.4 (5.2) μg/L (minimum, 1.0 μg/L; maximum, 36.1 μg/L; median, 7.3 μg/L). Using nonparametric methods, the postmortem tryptase reference range in nonanaphylactic death was established as

Background Mast cells are involved in the host immune response controlling infection with the non-invasive intestinal protozoan parasite Giardia intestinalis. Experimental infections in rodents with G. intestinalis showed increased intestinal expression of mucosal and connective mast cell specific proteases suggesting that both mucosal and connective tissue mast cells are recruited and activated during infection. During infection Giardia excretory-secretory proteins (ESPs) with immunomodulatory capacity are released. However, studies investigating potential interactions between Giardia ESPs and the connective tissue mast cell specific serine proteases, i.e. human chymase and mouse mast cell protease (mMCP)-4 and, human and mouse tryptase (mMCP-6) remain scarce. Results We first investigated if soluble Giardia proteins (sGPs), which over-lap extensively in protein content with ESP fractions, from the isolates GS, WB and H3, could induce mast cell activation. sGPs induced a minor activation of bone marrow derived mucosal-like mast cells, as indicated by increased IL-6 secretion and no degranulation. Furthermore, sGPs were highly resistant to degradation by human tryptase while human chymase degraded a 65 kDa sGP and, wild-type mouse ear tissue extracts degraded several protein bands in the 10 to 75 kDa range. In striking contrast, sGPs and ESPs were found to increase the enzymatic activity of human and mouse tryptase and to reduce the activity of human and mouse chymase. Conclusion Our finding suggests that Giardia ssp. via enhancement or reduction of mast cell protease activity may modulate mast cell-driven intestinal immune responses. ESP-mediated modulation of the mast cell specific proteases may also increase degradation of tight junctions, which may be beneficial for Giardia ssp. during infection.

Mastocytosis is a rare disease characterized by clonal proliferation of mast cells (MCs) in different organs. Clinical manifestations of mastocytosis are mostly due to release of mediators from MCs and, in many cases, such as urticaria, flushing, angioedema, and anaphylaxis, are an expression of the biological effects of mediators on endothelial cells. Chronic secretion of mediators in patients with mastocytosis can lead to alteration of endothelial function.We sought to investigate endothelial function in patients with mastocytosis using a noninvasive technique of flow-mediated dilation (FMD).Twenty-five adult patients with indolent and advanced forms of mastocytosis and 20 healthy control subjects were enrolled in the study. Ultrasound assessment of FMD was performed by measuring changes in the diameter of the brachial artery after 5 minutes of arterial occlusion. Changes in FMD were correlated with clinical parameters and serum tryptase levels.Patients with mastocytosis had lower FMD compared with healthy control subjects (P .001). Advanced and smoldering forms showed a lower FMD compared with indolent forms (P .001). FMD inversely correlated with age and serum tryptase levels and directly with median arterial pressure and recurrent flushing episodes. No correlation was found between FMD and osteoporosis, recurrent anaphylaxis, presence of skin lesions, and long-term antihistamine treatment.Endothelial dysfunction, as demonstrated by FMD reduction, is detectable in patients with mastocytosis and is more severe in patients with high tryptase levels and advanced disease. Endothelial function appears to be negatively influenced by MC proliferation rather than by the severity of mediator-related symptoms.

Mast cells (MCs) induce the progression of liver diseases including, but not limited to, hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), alcoholic and non-alcoholic fatty liver disease (ALD/NAFLD), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC). The effects of MCs during disease progression includes alterations in ductular reaction, steatosis, hepatic fibrosis and inflammation. In addition, there is significant crosstalk between MCs, MC mediators (histamine, tryptase, chymase) and MC-derived cytokines (transforming growth factor beta, tumor necrosis factor alpha, interleukins). Studies have been performed in rodent models, cultured cells, and human tissues to demonstrate the intracellular signaling implications of MC infiltration during liver disease. Targeting MCs may offer novel therapeutic strategies to treat liver disease. Our concise review will encompass the most recent studies involving MCs, their mediators and liver disease with the overall goal to inform the reader about the diverse role of these inflammatory immune cells in liver damage.

In recent years, knowledge about mechanisms underlying mast cell activation (MCA) and accumulation in various pathologic conditions increased substantially. In addition, criteria and a classification of MCA syndromes (MCASs) have been set forth. MCAS is defined by typical clinical symptoms, a substantial increase in serum tryptase level during an attack over the patient's baseline tryptase, and a response of the symptoms to drugs targeting mast cells, mediator production, and/or mediator effects. Alternative diagnostic criteria of MCAS have also been suggested, but these alternative criteria often lack specificity and validation. In this report, we critically review the contemporary literature relating to MCAS and compare the specificity, sensitivity, and strength of MCAS-related parameters within proposals to diagnose and classify MCAS and its variants. Furthermore, we highlight the need to apply specific consensus criteria in the evaluation and classification of MCAS in individual patients. This is an urgent and important medical necessity because as an increasing number of patients are being given a misdiagnosis of MCAS based on nonspecific criteria, which contributes to confusion and frustration by patients and caregivers and sometimes may delay recognition and treatment of correct medical conditions that often turn out to be unrelated to MCA. (C) 2021 The Authors. Published by Elsevier Inc. on behalf of the American Academy of Allergy, Asthma & Immunology.

The aim of this study was to evaluate splenic eosinophil and mast cell accumulation using pagoda red stain in a series of anaphylaxis-related deaths that underwent medico-legal investigations. Our goal was to assess whether fatal reactions to insect stings, intramuscularly administered antibiotics and intravenously injected contrast media are responsible for specific patterns of eosinophil and mast cell accumulation. Two study groups were prospectively formed, an anaphylaxis-related death group and a control group. Autopsy, histology (haematoxylin-eosin stain, pagoda red stain and immunohistochemistry using anti-tryptase antibodies), toxicology and postmortem biochemistry (beta-tryptase, total IgE and specific IgE) were performed in all cases. All tested parameters (spleen weight, beta-tryptase and total IgE levels as well as eosinophil, mast cell and degranulated mast cell numbers in the spleen) were significantly higher in the anaphylaxis-related death group. No statistically significant differences were observed among the various groups (intramuscular antibiotic injection, intravenous contrast medium administration and stinging insects) in any combination, suggesting that mast cell and eosinophil accumulation in the spleen during anaphylaxis does not have any specific pattern related to the triggering allergen. Despite a lower sensitivity than immunohistochemical staining in discriminating eosinophil and mast cells, pagoda red stain allowed these cells to be identified and could therefore be proposed as a low-cost, first-line diagnostic procedure in those situations where immunohistochemistry is not systematically performed or cannot be carried out.

Mastocytosis is a rare hematological neoplasm characterized by the proliferation of abnormal clonal mast cells (MCs) in different cutaneous and extracutaneous organs. Its diagnosis is based on well-defined major and minor criteria, including the pathognomonic dense infiltrate of MCs detected in bone marrow (BM), elevated serum tryptase level, abnormal MCs CD25 expression, and the identification of KIT D816V mutation. The World Health Organization (WHO) classification subdivides mastocytosis into a cutaneous form (CM) and five systemic variants (SM), namely indolent/smoldering (ISM/SSM) and advanced SM (AdvSM) including aggressive SM (ASM), SM associated to hematological neoplasms (SM-AHN), and mast cell leukemia (MCL). More than 80% of patients with SM carry a somatic point mutation of KIT at codon 816, which may be targeted by kinase inhibitors. The presence of additional somatic mutations detected by next generation sequencing analysis may impact prognosis and drive treatment strategy, which ranges from symptomatic drugs in indolent forms to kinase-inhibitors active on KIT. Allogeneic stem cell transplant (SCT) may be considered in selected SM cases. Here, we review the clinical, diagnostic, and therapeutic issues of SM, with special emphasis on the translational implications of SM genetics for a precision medicine approach in clinical practice.

International audience; Background: Serum total tryptase has been shown to increase during acute allergic reactions (acute tryptase, TA ); however, few studies have investigated the values of TA or a combination of TA and baseline tryptase (TB ) to discriminate positive from negative testing in perioperative hypersensitivity reaction (POH) allergy work-up. The aim of this study was to determine the diagnostic performance of TA in order to differentiate positive from negative allergy testing suspected POH and analyse the diagnostic performance of serial tryptase levels using several formulas.Methods: All patients from the University hospital of Montpellier and Strasbourg, France, who presented with suspected POH and underwent complete drug allergy work-up between March 2011 and December 2019 with available TA and TB were included. Four formulas, including a change in TA > 11 (F1), or >2 + 1.2 × TB (F2), or >3 + TB (F3), or >120%TB (F4), were applied.Results: One hundred and sixty-two patients were included, and 131 of them (80.8%) had Grade III or IV reactions. Ninety patients had positive allergy testing. The optimal cut-off value of TA to distinguish positive from negative allergy testing patients was 9.8 μg/L with an AUC of 0.817 (95% CI: 0.752-0.882, p < .001). The 93% PPV threshold for TA was 33 μg/L (95.8% specificity). Paired tryptase levels according to formulas F2 and F3 yielded the highest Youden index (0.54 and 0.53, respectively).Conclusion: The optimal cut-off point for TA for distinguishing positive from negative allergy testing suspected POH was 9.8 μg/L. TA value of 33 μg/L was required to achieve >90% PPV.

BackgroundPerioperative hypersensitivity reaction (HR) is an IgE-FcϵRI-mediated hypersensitivity reaction with degranulation and activation of mast cells and basophils. Several studies have focused on assessing the degranulation and activation of mast cells and basophils to diagnose and predict the prognosis of drug induced HR. However, it is challenging to isolate sufficiently pure mast cells and basophils from human sources to investigate. Effective biomarkers to assess mast cells and basophils activationin vivocould potentially have high diagnostic and prognostic values. In the present study, we investigated EVs pelleted from serum in patients with succinylated gelatin induced HR.MethodsExtracellular vesicles (EVs) were isolated using a total exosome isolation kit and ultracentrifugation, characterized by Western blot, transmission electron microscopy, and nanoparticle tracking analysis. Basophils were isolated from fresh peripheral blood by negative selection using Basophil Isolation Kit II. Human mast cell line was stimulated with IL4. The expression levels of proteins related to the hypersensitive response were evaluated by Western blotting and flow Cytometer. Histamine and tryptase levels were tested using a commercial ELISA kit, and gene expression of inflammatory mediators was evaluated by qRT-PCR. The receiver operating characteristic (ROC) curve was used to evaluate the specificity and sensitivity of biomarker in predicting HR.ResultsThe concentration of EVs and protein expression level of CD63, FcϵRI, CD203c and tryptase were significantly (p< 0.05) increased in HR samples. The expression level of mast cell/basophil specific CD203c were significantly increased in EVs derived from serum and basophils of HR patients, and the CD203c+-EVs production in mast cells is dramatically increased in the presence of IL4, which positively correlated with histamine, tryptase and inflammatory mediators. Moreover, the ROC curve of EVs concentration and CD203c expression indicated that CD203c+-EVs had a strong diagnostic ability for HR.ConclusionSerum CD203c+-EVs serves as a novel diagnostic and prognostic biomarker for HR.

The biological significance of the CD38 molecule goes beyond metabolic, enzymatic, and proliferative functions. CD38 possesses the functions of an exoenzyme and receptor, and is actively involved in the mechanisms of adhesion, migration, intercellular signaling, formation of immune synapses, and modulation of the activity of a wide range of immune and non-immune cells. The aim of this study was the immunohistochemical assessment of the cytological and histotopographic characteristics of CD38 expression in mast cells. CD38 expression was found in a minority of the mast cell population. It is characterized by wide variability from low to high levels. The intensity of CD38 expression in mast cells has organ-specific features and depends on the development of pathological processes in a specific tissue microenvironment. The mechanisms of intercellular interaction between mast cells and CD38+ cells foster new understanding of the protumorigenic or antitumor potential of tryptase.

The diagnosis of drug-induced anaphylactic death is an important component of forensic medicine. The purpose of this study was to explore the expression of FceRIα and tryptase in human lung tissue during drug-induced anaphylactic death and its value for forensic medicine. The expression of FceRIα and tryptase in lung tissues of the drug-induced anaphylactic death group (n = 30) and control group (who died due to sudden cardiac death, falling from a height, or traffic accidents, n = 30) was detected by immunohistochemistry and immunofluorescence staining. The difference in FceRIα and tryptase expression in the lung tissue between the drug-induced anaphylactic death group and the control group was statistically significant (p