Background Cat allergen sensitization is common in childhood, yet the relationship between immunological test results and clinical symptoms remains unclear. Skin prick testing (SPT) and serum cat-specific immunoglobulin E (cat-sIgE) are widely used, but their optimal cut-off values according to symptom status are not well defined. Objective To evaluate cat allergen sensitization in pediatric patients, assess the diagnostic performance of SPT and cat-sIgE, and determine optimal cut-off values according to symptom status following cat exposure. Methods This retrospective cross-sectional study included children aged 0-18 years with cat allergen sensitization who underwent both SPT and cat-sIgE testing between January 2023 and January 2025. Patients were classified as symptomatic or asymptomatic based on documented allergic symptoms following cat exposure. Demographic characteristics, environmental exposures, comorbid allergic diseases, laboratory findings, and aeroallergen co-sensitization were analyzed. Multivariable logistic regression was used to identify factors associated with symptomatic status following cat exposure, and receiver operating characteristic (ROC) curve analysis was performed to evaluate diagnostic performance. Results A total of 428 children were included, of whom 211 (49.3%) were asymptomatic and 217 (50.7%) were symptomatic according to clinical history following cat exposure. Cat exposure-related symptoms were predominantly nasal, followed by ocular, respiratory, and cutaneous symptoms. In the multivariable model, asthma was associated with higher odds of symptomatic status, whereas pollen sensitization, prenatal cat exposure, and longer duration of cat ownership were inversely associated with symptomatic status. ROC analysis demonstrated high diagnostic accuracy for both SPT wheal size and cat-sIgE levels, with higher cut-off showing high specificity for symptomatic status following cat exposure. Conclusion SPT wheal size and cat-sIgE levels showed diagnostic value in pediatric cat allergen sensitization. Laboratory sensitization should be interpreted together with clinical history, and distinct cut-off values based on symptom status following cat exposure may improve diagnostic accuracy and clinical interpretation.

Introduction The 2020 Protection of Students with Life-Threatening Allergies Act, obligates schools across Alberta, Canada to hold a common use stock of at least one epinephrine autoinjector (EAI) and to maintain a protocol for the prevention and management of anaphylaxis Herein, we assessed the effectiveness of this policy by comparing pre-hospital EAI use before and after implementation of the act. Methods The Cross-Canada Anaphylaxis Registry (C-CARE) enrolls patients presenting to a participating emergency department with anaphylaxis defined as the involvement of ≥2 systems and/or hypotension. Specific to this project, we extracted data on pediatric patients recruited from the Stollery Children's Hospital in Edmonton, Alberta from 2016-2024. Data were collected on demographics, comorbidities, symptomatology, pre- and intra-hospital management, and outcome of anaphylaxis by standardized chart review. Multivariable logistic regression was used to assess pre-hospital EAI use for cases occurring at school before versus after the enactment of the Act on January 1, 2020. Evaluating pre-hospital EAI use in Quebec and Ontario and antihistamine use pre versus post act in Alberta were used as negative controls. Result Of the 59 cases of in-school anaphylaxis identified over the study period, 52.5% occurred post-Act. The median age was 13.0 years (IQR=9.5-15.8) and 40.7% were male. EAI use in schools was greater post-act versus pre-act (64.5% versus 35.7%, aOR=3.82, 95%CI=1.24-11.7). There was no difference in pre-hospital EAI use pre versus post 2020 in Quebec and Ontario, that did not use the act (aOR=0.72, 95%CI=0.31-1.70). There was no difference in pre-hospital antihistamine use pre versus post act (aOR=0.31, 95%CI=0.07-1.41). Conclusion Implementation of the provincial policy was associated with an increase in pre-hospital EAI use in cases of pediatric anaphylaxis occurring at school. These preliminary results support the effectiveness of policy interventions for anaphylaxis management.

Background Dendritic cells (DCs) serve as pivotal modulators of immune tolerance, with interleukin-10 (IL-10) secretion acting as a core mechanism to sustain this regulatory function. Rab27a, a small GTPase involved in vesicular trafficking processes, is well recognized for its critical role in cellular secretion events. However, its specific function in governing IL-10 release from DCs remains unclarified. This study aimed to decipher the molecular mechanisms through which Rab27a regulates IL-10 secretion in DCs and explore the relevance of this pathway to immune dysregulation in food allergy (FA). Methods Bone marrow-derived dendritic cells (BMDCs) were isolated from C57BL/6 mice and purified using flow cytometry. Plasmacytoid DCs (pDCs) were obtained from the peripheral blood of FA patients and age-matched healthy control individuals for comparative analysis. Results Peripheral pDCs from FA patients exhibited notably reduced Rab27a activation levels compared to those from healthy controls. Concurrently, DCs from FA patients showed impaired immune tolerogenic function, as evidenced by their decreased ability to induce type 1 regulatory T (Tr1) cells. A strong positive correlation was observed between Rab27a activation and the induction of Tr1 cells by DCs. Mechanistically, activated Rab27a formed a complex with IL-10, facilitating the extracellular release of IL-10 from DCs. The guanine nucleotide exchange factor MADD (MAPK-activating death domain) was identified as a key regulator of Rab27a activation; knockdown of MADD in DCs eliminated Rab27a activation and IL-10 secretion. Conclusions Activated Rab27a is essential for IL-10 secretion by DCs, and MADD acts as a critical upstream regulator of Rab27a activation. Defects in the MADD-Rab27a-IL-10 signaling pathway contribute to impaired DC tolerogenicity in FA, suggesting that this pathway may serve as a potential therapeutic target for restoring immune balance in allergic diseases.

Background Anaphylaxis is a potentially life-threatening systemic allergic reaction with an increasing incidence in children. The World Allergy Organization (WAO) recently introduced trigger-independent diagnostic criteria and severity grading, enabling standardized evaluation of acute systemic allergic reactions. Objective To evaluate clinical characteristics, etiological distribution, severity patterns, and risk factors for severe reactions in children presenting with acute systemic allergic reactions and anaphylaxis using the updated WAO criteria. Methods This retrospective study included children with acute systemic allergic reactions (WAO Grade 2-4) presenting to a tertiary university pediatric emergency department between January 2017 and December 2022. Clinical features, triggers, management, and outcomes were analyzed. Pediatric patients with confirmed anaphylaxis were divided into three subgroups based on etiology: food, drug, and other allergens. Severity was classified according to the WAO grading system, and logistic regression analysis was performed to identify independent risk factors for severe reactions. Results Among 75 children prediagnosed with anaphylaxis, 61 (81.3%) met the WAO criteria. Food was the most common trigger (49%), followed by drugs (21.3%) and other allergens (29.5%), with food-induced reactions occurring at a younger median age. Cutaneous (60.7%) and gastrointestinal symptoms (vomiting, 41.0%) were the most frequent clinical manifestations. Cardiovascular findings distinguished severe reactions, with hypotension observed in (45%) of Grade 4 cases and none in Grade 3 (p<0.001). Nausea was more common in reactions caused by other allergens compared with food (77.8% vs 11.1%, p<0.05). In multivariable analysis, drug-induced and other allergen-related reactions were associated with a lower likelihood of severe reactions compared with food-induced anaphylaxis (OR p=0.011 and OR=0.143, p=0.029, respectively). Adrenaline autoinjector were prescribed at discharge in a minority of patients, with a rate of 26.7% among food-allergic cases. Conclusion Applying the WAO criteria, cardiovascular compromise was the main determinant of severe pediatric anaphylaxis, emphasizing the need for severity-based assessment and optimized discharge practices.