Deletion of IL-4Rα Signaling on B Cells Limits Hyperresponsiveness Depending on Antigen Load

Background: B cells play an important role in allergies through secretion of IgE. IL-4 receptor alpha (IL-4R alpha) is key in allergic asthma and regulates type 2 cytokine production, IgE secretion, and airway hyperresponsiveness. IL-4 activation of B cells is essential for class switching and contributes to the induction of B effector 2 (Be2) cells. The role of Be2 cells and signaling via IL-4R alpha in B cells is not clearly defined. Objective: We sought to find out whether IL-4R alpha-responsive B cells or Be2 function was essential in experimental allergic asthma. Methods: Mice lacking IL-4R alpha on B cells (mb1(cre)IL-4R alpha(-/lox)) or littermate controls (IL-4R alpha(-/lox)) and mice lacking IL-4 or IL-4/IL-13 on B cells were sensitized and challenged with high-dose house dust mite (>10 mu g) or with low-dose house dust mite (<3 mu g). We also adoptively transferred naive IL-4R alpha(-/lox) or IL-4R alpha(-/-) B cells into mu MT-/- mice a day before sensitization or a day before challenge. We analyzed lung inflammation, cellular infiltrate, and airway hyperresponsiveness. Results: We found that IL-4R alpha signaling on B cells was important for optimal T(H)2 allergic immune responses mainly when the load of antigen is limited. IL-4R alpha signaling on B cells was essential for germinal centers and in the effector phase of allergic responses. Be2 cells were essential in airway hyperresponsiveness, but not in other parameters. Conclusions: IL-4R alpha signaling on B cells is deleterious in allergic asthma because it is required for optimal T(H)2 responses, Be2 function, germinal center formation, and T follicular helper cells, especially when the load of the antigen is limiting.