Airway-Resident Memory CD8 T Cells Provide Antigen-Specific Protection against Respiratory Virus Challenge through Rapid IFN-γ Production.

CD8 airway resident memory T (TRM) cells are a distinctive TRM population with a high turnover rate and a unique phenotype influenced by their localization within the airways. Their role in mediating protective immunity to respiratory pathogens, although suggested by many studies, has not been directly proven. This study provides definitive evidence that airway CD8 TRM cells are sufficient to mediate protection against respiratory virus challenge. Despite being poorly cytolytic in vivo and failing to expand after encountering Ag, airway CD8 TRM cells rapidly express effector cytokines, with IFN-γ being produced most robustly. Notably, established airway CD8 TRM cells possess the ability to produce IFN-γ faster than systemic effector memory CD8 T cells. Furthermore, naive mice receiving intratracheal transfer of airway CD8 TRM cells lacking the ability to produce IFN-γ were less effective at controlling pathogen load upon heterologous challenge. This direct evidence of airway CD8 TRM cell-mediated protection demonstrates the importance of these cells as a first line of defense for optimal immunity against respiratory pathogens and suggests they should be considered in the development of future cell-mediated vaccines.