Basophil activation test
BLOOD
Blood was collected in lithium heparin‐containing tubes, and the BAT was performed on the same day of blood collection. Per condition, 100 μL of whole blood was incubated with the same volume of egg extract (ALK‐Abello) or baked EW (Sigma‐Aldrich) diluted in RPMI (GIBCO). Baked EW was prepared as a single batch by heating in a oven at 180°C for 20 min and stored at −80°C thereafter. Anti‐IgE (1 μg/mL; Sigma‐Aldrich) and formyl‐methionyl‐leucylphenylalanine (fMLP, 1 μM; Sigma‐Aldrich) were used as positive controls and RPMI alone as a negative control. Cells were stained with CD123‐FITC, CD203c‐PE, HLA‐DR‐PerCP, and CD63‐APC (all Biolegend) which had been lyophilised in individual tubes as a single batch at the start of the study. Flow cytometry was performed using FACS Fortessa with FACSDiva software (BD Biosciences). The flow cytometry data were analysed using FlowJo software (version 7.6.1; TreeStar). Basophils were gated as SSC