Cannabinoid receptor 2 signal promotes type 2 immunity in the lung

Type 2 immunity in the lung protects against pathogenic infection and facilitates tissue repair, but its dysregulation may lead to severe human diseases. Notably, cannabis usage for medical or recreational purposes has increased globally. However, the potential impact of the cannabinoid signal on lung immunity is incompletely understood. Here, we report that cannabinoid receptor 2 (CB2) is highly expressed in group 2 innate lymphoid cells (ILC2s) of mouse and human lung tissues. Of importance, the CB2 signal enhances the IL-33-elicited immune response of ILC2s. In addition, the chemogenetic manipulation of inhibitory G proteins (Gi) downstream of CB2 produces a similarly promotive effect. Conversely, the genetic deletion of CB2 mitigates the IL-33-elicited type 2 immunity in the lung. Also, such ablation of the CB2 signal ameliorates papain-induced tissue inflammation. Together, these results have elucidated a critical aspect of the CB2 signal in lung immunity, implicating its potential involvement in pulmonary diseases.