Development of eosinophilic inflammation is independent of B-T cell interaction in a chronic house dust mite-driven asthma model.

Background Chronic exposure to environmental triggers, such as house dust mite (HDM), drives T helper 2 (Th2) cell-mediated asthma. Recent evidence has shown that B-T cell interaction, and in particular germinal centre reactions and follicular T helper (Tfh) cells are required for the development of eosinophilic airway inflammation in HDM-driven models containing a sensitization and challenge phase. Whether B-T cell interactions are essential for pulmonary eosinophilic inflammation following chronic allergen provocation remains unknown. Aims In this study, we investigated the importance of B-T cell interaction in the development of eosinophilic airway inflammation and pulmonary remodelling in a chronic HDM-driven asthma model. Methods We exposed C57BL/6, Cd40l(-/-), and Mb1(-/-) mice to HDM three times a week for five consecutive weeks. Results Chronic HDM exposure induced a pronounced eosinophilic allergic airway inflammation in broncho-alveolar lavage fluid (BALf) and lung tissue, associated with the formation of immunologically active inducible bronchus-associated lymphoid tissue (iBALT) in the lungs. The absence of B cells or lack of CD40L signalling did not hamper eosinophilic inflammation in the airways, although the number of Tfh and Th2 cells was substantially reduced in the lungs. Importantly, type 2 innate lymphoid cell (ILC2) numbers in BALf and lung were not affected by the absence of B cells or B-T cell interaction. Furthermore, eosinophilic airway inflammation is not sufficient to induce pulmonary remodelling and airway hyperresponsiveness. Conclusion and Clinical Relevance From these findings, we conclude that B-T cell interaction is required for robust Tfh and Th2 cell induction, but not essential for eosinophilic airway inflammation during a chronic HDM-driven asthma model.