Allergic asthma (AA) and allergic rhinitis (AR) are both chronic allergic airway diseases characterised by the production of type 2 cytokines, leading to prototypic characteristics of allergic disease such as eosinophilia and elevated immunoglobulin (Ig) E levels, the latter reactive to inhaled allergens. The production of allergen specific IgE has classically been attributed to secondary lymphoid organs (SLO), where distinct B cell follicles can be found and where B cell selection and differentiation in response to antigen is governed in germinal centers. However, in chronic inflammatory diseases like AA and AR, the induction of tertiary lymphoid organs (TLO) has been described, and in both, evidence for localized germinal centers is found. Yet, the role of TLO in allergic airway disease remains unclear. This project aims to elucidate the division of labour between TLO and SLO in allergic airway disease by studying the B cell differentiation and selection processes therein. By studying both local and systemic humoral response to allergens, we aim to understand how these differentially contribute to inflammation in allergic airway disease, which in turn is important to optimise diagnostic and therapeutic procedures.