We previously reported that the transcription factors Stat3 and C/EBPβ synergize to induces the expression of microRNA (miR)-21 and miR-181b to promote MDSC expansion in a mouse model of polymicrobial sepsis that progresses from an early/acute proinflammatory phase to a late/chronic immunosuppressive stage.
Adoptive transfer of C/EBPβ-deficient Gr1<sup>+</sup>CD11b<sup>+</sup> cells from late septic mice exacerbated inflammation in control mice undergoing early sepsis, confirming they were not immunosuppressive.
Mechanistically, transcription factor Rb phosphorylation supports Stat3 and C/EBPβ accumulation at both miRNA promoters, and C/EBPβ or Stat3 depletion by siRNA in sepsis Gr1<sup>+</sup>CD11b<sup>+</sup> MDSCs inhibits miR-21 and miR-181b expression.