Since C/EBP-β binds to the SerpinB2 proximal promoter in an LPS-inducible manner both in vitro and in vivo, we wanted to address the question of whether C/EBP-β was an essential factor for driving transcription from the SerpinB2 promoter in cells in response to LPS. The ability of endogenous C/EBP-β to direct transcription from the SerpinB2 proximal promoter was examined by transfection of the pGLmP-539 murine SerpinB2 luciferase reporter construct into Cebpb+/+ and Cebpb−/− MEFs. We found that LPS-stimulated SerpinB2 promoter activity was significantly increased in Cebpb+/+ MEFs and abrogated in Cebpb−/− MEFs (Fig. 8A), indicating that endogenous C/EBP-β is required for LPS-induced SerpinB2 proximal promoter activity.