IL-4Rα signalling in CD4+CD25+FoxP3+ T regulatory cells restrain airway inflammation via limiting local tissue IL-33.

Impaired tolerance to innocuous particles during allergic asthma has been linked to the increased plasticity of FoxP3+ regulatory T (Treg) cells, reprogramming into pathogenic effector cells, thus exacerbating airway disease. Failure in tolerance is suggested to be driven by TH2 inflammatory signals. The canonical IL-4Rα-signalling, an essential driver of TH2-type airway responses to allergens was investigated on its in vivo role on the regulatory function of FoxP3+ Tregs in allergic asthma. We used transgenic Foxp3creIL-4rα-/lox and littermate control mice to investigate the role of IL-4/IL-13 signalling via T regs in a house dust mite (HDM)-induced allergic airway disease. We sensitised mice intratracheally on day 0 and challenged them on day 6-10 and analysed airway hyperresponsiveness (AHR), airway inflammation, mucus production and cellular profile on day 14. In the absence of IL-4Rα responsiveness on FoxP3+ Tregs, there was an exacerbated AHR and airway inflammation in HDM-sensitised mice. Interestingly, a reduced induction of FoxP3+ Tregs accompanied increased IL-33 "alarmin" production and innate lymphoid cells type 2 (ILC2) activation in the lung exacerbating airway hyperreactivity and lung eosinophilia. We conclude that IL-4Rα unresponsive FoxP3+ T regulatory cells results in exaggerated innate TH2-type, IL-33-dependent airway inflammation and a break in tolerance during allergic asthma.