IL33 and asthma: In some circumstances (e.g., dermatitis, asthma, and graft-versus-host disease), MCs possess immunosuppressive properties mediated by the production of immunoregulatory cytokines such as IL-2, IL-10, IL-33, and TGF-β.19,20 Considering these previous results together with our current ones (Fig. 6), it is plausible to suggest that desensitized MCs behave as a form of regulatory cells producing these regulatory cytokines and categorized as regulatory MCs, and that they directly or indirectly (via the induction of Treg cells) suppress undesired allergic responses.