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 α (IL-4Rα) 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-4Rα in B cells is not clearly defined.

OBJECTIVE

We sought to find out whether IL-4Rα-responsive B cells or Be2 function was essential in experimental allergic asthma.

METHODS

Mice lacking IL-4Rα on B cells (mb1^creIL-4Rα^-/lox) or littermate controls (IL-4Rα^-/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 μg) or with low-dose house dust mite (<3 μg). We also adoptively transferred naive IL-4Rα^-/lox or IL-4Rα^-/- B cells into μMT^-/- mice a day before sensitization or a day before challenge. We analyzed lung inflammation, cellular infiltrate, and airway hyperresponsiveness.

RESULTS

We found that IL-4Rα signaling on B cells was important for optimal T_H2 allergic immune responses mainly when the load of antigen is limited. IL-4Rα 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-4Rα signaling on B cells is deleterious in allergic asthma because it is required for optimal T_H2 responses, Be2 function, germinal center formation, and T follicular helper cells, especially when the load of the antigen is limiting.

IL-4Rα signalling in B cells and T cells play differential roles in acute and chronic atopic dermatitis

Atopic dermatitis (AD) is a common pruritic inflammatory skin disease with complex environmental and genetic predisposing factors. Primary skin barrier dysfunction and aberrant T helper 2 (TH2) responses to common allergens, together with increased serum IgE antibodies, characterise the disease. B and T cells are essential in the disease manifestation, however, the exact mechanism of how these cells is involved is unclear. Targeting interleukin 4 receptor alpha (IL-4Rα), an IL-4/IL-13 signalling axis, with dupilumab shows efficacy in AD. We investigated the importance of IL-4Rα signalling specifically on B and T cells during acute and chronic models of AD. We used House dust mite (HDM) and Ovalbumin (OVA) in chronic models and a low-calcemic analog of vitamin D (MC903) for acute models of AD. We used mb1creIL-4Rα-/lox, iLCKcreIL-4Rα-/lox, LCKcreIL-4Rα-/lox, CD4creIL-4Rα-/lox, Foxp3creIL-4Rα-/lox and IL-4Rα-/lox littermate controls. IL-4Rα-responsive B cells were essential in serum IgE levels, but not in epidermal thickening in both chronic and acute models. IL-4Rα-responsive T cells were essential in epidermal thickening in the pan-T cell, but not CD4 or CD8 T cells suggesting the importance of γδT cells during acute AD. Our results suggest that IL-4Rα responsiveness on innate T cells regulates acute atopic dermatitis, while on B cells it regulates IgE.

IgM regulates airway hyperresponsiveness in allergic asthma through acetyl choline receptors

Allergic asthma is a disease driven by T helper 2 (TH2)-type cells secreting interleukin (IL-) 4, 5 and 13. It is characterized by eosinophils, airway hyperesponsiveness (AHR) and IgE secreting B cells. B cells play a role in allergic asthma in an allergen load dependent manner. IgM isotype secreted by naïve B cells is important for class switching. It is currently unclear how IgM isotype contributes in the development of allergic asthma. We investigated the role of IgM isotype in a house dust mite (HDM)-induced TH2 allergic asthma model. We sensitised wild type (wt), IgM-deficient (IgM−/−) and B cell-deficient (uMT−/−) mice with high (&gt;10 ug) and low (&lt;3 ug) dose of HDM extracts. We found IgM to be essential in antibody class switching and in AHR, but not in TH2 airway inflammation or eosinophilia. RNA seq suggested that IgM regulated AHR through modulating muscarinic receptor genes, particularly M3 and this was independent of microbiota. Transfer of wild type serum, but not B cells into IgM−/− mice could restore class switching but not AHR. These unprecedented findings suggest that IgM has a unique function in allergic asthma and regulates AHR by interacting with non-immune genes.