Allergy & Immunology

Real-world European EGPA data show biologics spare steroids and improve control

This multicountry chart review included 407 patients with eosinophilic granulomatosis with polyangiitis from five European nations. Vasculitic-phase patients had the greatest comorbidity burden, most clinical manifestations, and highest hospitalization rates versus prodromal or eosinophilic phases. Oral corticosteroid use was nearly universal across phases, highlighting chronic steroid dependence in routine EGPA care. Among 162 evaluable patients, biologic initiation reduced oral steroid prescriptions per person-year from 0.69 to 0.12. After biologics, relapse rates decreased and remission rates approximately doubled, indicating better disease control in practice. 1

Cat allergy review highlights component-based AIT and novel combination strategies

This review summarizes cat allergy epidemiology, molecular allergens, clinical phenotypes, and current and emerging treatments. Fel d 1 and Fel d 4 are particularly associated with asthma development and severity, stressing the importance of component-level sensitization assessment. Avoidance and pharmacotherapy are often inadequate because cat allergens are ubiquitous, including in non–cat-owning households. Subcutaneous and sublingual allergen immunotherapy are disease-modifying but limited by extract composition, potency, and low prescription rates. Formulations incorporating allergens beyond Fel d 1 and combinations with monoclonal antibodies may enhance control of cat-induced asthma and rhinitis. 2

Hereditary angioedema features increased eosinophil activation without eosinophilia

This single-center retrospective study compared 48 hereditary angioedema patients with 1,880 controls at a tertiary allergy and angioedema clinic. Bayesian multilevel modeling, adjusted for demographic and allergic factors, showed a 1.52-fold increase in serum eosinophil cationic protein in hereditary angioedema. Absolute eosinophil counts were not elevated, indicating enhanced eosinophil activation independent of circulating eosinophil numbers. Findings suggest a previously unrecognized eosinophilic inflammatory component beyond bradykinin-driven edema formation in hereditary angioedema. Further work is needed to determine how eosinophil activation contributes to phenotypic variability and comorbidities. 3

IL-33/ST2 signaling directly triggers eosinophil LTC4 synthesis in allergy models

This mechanistic study tested whether IL-33/ST2 activation can directly induce leukotriene C4 production by eosinophils. In a murine allergic inflammation model, ST2 activation was a key step for leukotriene C4 synthesis by lipid body–enriched eosinophils. Exogenous IL-33 elicited leukotriene C4 synthesis from activated eosinophils in vivo and from human eosinophils in vitro. These data link epithelial alarmin IL-33 to eosinophil-derived cysteinyl leukotrienes as a distinct effector pathway. The IL-33/ST2–LTC4 axis represents a potential therapeutic target in cysteinyl leukotriene–mediated conditions such as asthma and nasal polyposis. 4