Mast cell mediators: their subcellular localization, bacterial influence on their release and expression and their potential value as markers for predicting the severity of allergic reactions

Allergic reactions involve the explosive release of inflammatory mediators from mast cells including the proteases tryptase, carboxypeptidase A3 (CPA3) and chymase; and there have been suggestions that dipeptidyl peptidase I (DPPI) could be secreted as well. Our aim has been to investigate the levels of mast cell proteases and a panel of proinflammatory cytokines in serum during allergic reactions provoked by drugs or food to identify and replicate distinct clinico-immunological endotypes of allergic reactions using topological data analysis. In addition, we have investigated factors that can modulate the release and expression of mast cell mediators and their subcellular localization. Patients who had suffered drug- or food-induced allergic reactions were recruited from two separate centers (Southampton, UK and Doha, Qatar). Healthy individuals who had no history of allergic diseases were recruited to serve as controls. Detailed clinical assessment and measurements of mast cell proteases and pro-inflammatory cytokines were performed. The clinical and biochemical parameters were analyzed using topological data analysis. In addition, cells of the LAD2 mast cell line were employed to investigate the effect of bacterial infection on the release and expression of mast cell mediators. This cell line was also employed to investigate the subcellular localization of mast cell proteases through the application of immunocytochemical analysis. There were higher levels of CPA3 in baseline serum samples from patients with more severe historical allergic reactions than in those from healthy individuals (p< 0.0001). CPA3 levels of ≥ 6.5 ng/ml were associated with severe allergic reactions in patients with drug allergies (AUC: 0.61, 95% CI: 0.51-0.71, p= 0.048), and levels of ≥ 3 ng/ml in those with food allergies (AUC: 0.74, 95% CI: 0.62-0.86, p= 0.002). Higher serum levels of CPA3 were seen also in patients with one or more concomitant atopic conditions (including atopic dermatitis, hay fever and asthma) compared to those in healthy subjects (p< 0.0001). A strong association was found between the severity of allergic reactions and concomitant atopic illnesses (p< 0.0001). Topological data analysis allowed identification of four novel clinico-immunological clusters those with: (I) high CPA3 and IL-13 levels, females, drug reactions, more severe historical reactions; (II) high CPA3, low IL-13, males, food reactions, more severe historical reactions; (III) low CPA3 and IL-13 levels, young, females, food reactions, mild historical reactions; and (IV) low CPA3, high IL-13, females, drug reactions, mild historical reactions. These clusters were replicated in both geographical cohorts. In separate studies with cultured LAD2 cells, it was found that S. aureus infection could inhibit IgE- and non-IgE-dependent mast cell degranulation and down-regulate gene expression for major cytokines involved in anti-bacterial defense mechanisms (including that for TNFα, IL-8, and IL-1β). Bacterial exposure also altered the phosphorylation of protein kinases downstream of FcRI engagement. At the subcellular level, DPPI was observed inside the granules of mast cells and colocalized with tryptase, CPA3 and chymase. Our finding that DPPI may be present in association with other mast cell proteases within the granules suggests that DPPI is secreted upon mast cell stimulation and may have extracellular roles in immune modulation. DPPI could thus represent a novel marker for mast cell activation that can enhance the diagnosis of allergic reactions when measured in combination with tryptase and CPA3. The potential for bacterial infection to interfere with mast cell responses could reduce the susceptibility to allergic reactions and as the mechanisms involved deserve consideration as a novel therapeutic approach to prevent development of severe reactions. Serum levels of CPA3 have the potential to predict the severity of allergic reactions to drugs or food. Identification of four multidimensional endotypes underlines the connection between CPA3 and IL-13 levels and their association with clinical features of patients who have drug or food allergies. Their use as biomarkers can help to identify those at particular risk of allergic reactions and allow optimal interventions to be undertaken

Data for "Mast cell mediators: their sub cellular localisation, bacterial influence on their release and expression and their potential value as markers for predicting the severity of allergic reactions"

The data support the thesis &quot;Mast cell mediators: their sub cellular localisation, bacterial influence on their release and expression and their potential value as markers for predicting the severity of allergic reactions&quot;. It contains spreadsheets and SPSS files of clinical and immunological parameters for Southampton and Qatar cohort studies. It also contains prism files for LAD2 infection with Staph aureus, including levels of b-hexasominidase and cytokines and gene expression data. The results for MAPK is also included (spreadsheet and prism files). </span

Comprehensive characterisation of difficult-to-treat asthma reveals near absence of T2-low status

Background: asthma is conventionally stratified as type 2-inflammation (T2) high or T2-low disease. Identifying T2-status has therapeutic implications for patient management but real-world understanding of this T2 paradigm in difficult-to-treat/ severe asthma remains limited.Objectives: to identify prevalence of T2-high status in difficult-to-treat asthma patients using a multicomponent definition and compare clinical and pathophysiological characteristics between patients classified as T2-high and T2-low.Methods: 388 biologic naïve patients from the Wessex Asthma Cohort of difficult asthma (WATCH) study, United Kingdom, were evaluated. T2-high asthma was defined as fractional exhaled nitric oxide (FeNO)≥20ppb and/or peripheral blood eosinophils (PBE) ≥150 cells/ul and/or need for maintenance oral corticosteroids and/or clinically allergy-driven asthma.Results: this multicomponent assessment identified T2-high asthma in 93% (360/388) of patients. Body Mass Index, inhaled corticosteroid dose, asthma exacerbations and common comorbidities did not differ by T2-status. Significantly worse airflow limitation was found in T2-high compared to T2-low patients (FEV1/FVC 65.9% vs 74.6%). 75% patients defined as T2-low asthma had raised PBE within the preceding 10-years, leaving only 7 patients (1.8%) who never had T2-signals. Incorporation of sputum eosinophilia ≥2% into the multicomponent definition in a subset of 117 patients with induced sputum data similarly found that 96% (112/117) met criteria for T2-high asthma of which 50% (56/112), had sputum eosinophils ≥2%.Conclusions: amost all patients with difficult-to-treat asthma have T2-high disease with &lt;2% of patients never displaying T2-defining criteria. This highlights a need to comprehensively assess T2 status in clinical practice before labelling a patient with difficult-to-treat asthma as T2-low.</p