Lung tissue-resident memory T cells: the gatekeeper to respiratory viral (re)-infection

The discovery of lung tissue-resident memory T (T_RM) cells and the elucidation of their function in antiviral immunity have inspired considerable efforts to leverage the power of T_RM cells, in defense to the infections and reinfections by respiratory viruses. Here, we have reviewed lung T_RM cell identification, molecular regulation, and function after influenza and SARS-CoV-2 infections. Furthermore, we have discussed emerging data on T_RM responses induced by systemic and mucosal vaccination strategies. We hope that our current outstanding of T_RM cells in this review could provide insights toward the development of vaccines capable of inducing highly efficacious mucosal T_RM responses for protection against respiratory viral infections.