Pseudomonas aeruginosa-infected Myeloid-derived suppressor cells (MDSC) down-regulate lymphocyte activity and improves mice survival, following in vivo lung transfer

Pseudomonas aeruginosa ( P.a .) is a pathogenic opportunistic bacterium, classified as a priority by the WHO for the research of new treatments. As this bacterium is harmful trough the inflammation and tissue damage it causes, we investigated the role of Myeloid Derived Suppressor Cells (MDSC) in P.a. infections and their potential as a therapeutic target. We found that upon P.a. exposure, MDSC activity is increased and gain contact-independent properties. Interestingly, this activation is dependent on P.a. mobility but not its flagellin nor TLR5-MyD88 pathway. We also show that MDSC adoptive transfer increases mice survival in P.a. acute lung infection both in therapeutic and prophylactic set ups. Finally, using an in vitro scratch assay model, we suggest that MDSC acts directly on lung epithelium to stimulate its repair. Together, we highlight a potential beneficial role of MDSC in P.a. infection response. We believe that the unique properties of MDSC make them attractive potential new therapeutic tools for patients with acute or chronic inflammatory diseases, where inflammation has to be kept in check. ### Competing Interest Statement The authors have declared no competing interest.