Then, in the present study, we first verified the potential roles of omental MSs in mediating the peritoneal immune response provoked by CLP-induced peritonitis, and further provided definitive evidence that the excision of omental MSs could diminish B1 cell responses, attenuate IgM production and impair neutrophils migration and function in the peritoneal cavity, which consequently leads to systemic infection and exacerbating sepsis. Here, CD40LG is linked to Sepsis.