Cytokine responses to LPS in reprogrammed monocytes are associated with the transcription factor PU.1

Myeloid-derived suppressor cells (MDSCs) are functionally immunosuppressive cellsthat arise and expand during extensive inflammatory conditions by increasedhematopoietic output or reprogramming of immune cells. In sepsis, an increase of circulatingMDSCs is associated with adverse outcomes, but unique traits that can beused to identify increased activity of MDSCs are lacking. By using endotoxin toleranceas a model of sepsis-induced monocytic MDSCs (M-MDSC-like cells), this studyaims to identify the mediator and transcriptional regulator profile associated with MMDSCactivity. After analyzing 180 inflammation-associated proteins, a profile of differentiallyexpressed cytokines was found in M-MDSC-like cells versus normal monocytesstimulated with LPS. These cytokines were associated with 5 candidate transcriptionfactors,where particularly PU.1 showed differential expression on both transcriptionaland protein levels in M-MDSC-like cells. Furthermore, inhibition of PU.1led to increased production of CXCL5 and CCL8 in M-MDSC-like cells indicating itsrole in regulating the ability ofM-MDSC-like cells to recruit other immune cells. Takentogether, the study identifies a unique profile in the pattern of immune mediatorsdefining M-MDSC activity upon LPS stimulation, which offers a functional link to theircontribution to immunosuppression.Funding Agency:General Electric