The susceptibility of mice to infectious complications is dramatically increased in an accompaniment with systemic inflammatory response syndrome (SIRS). Polymorphonuclear neutrophils with immunosuppressive ability (PMN-II) that appear in response to SIRS have been classified as one of the cells responsible for the increased susceptibility of mice with SIRS (SIRS mice) to sepsis induced by cecal-ligation and puncture (CLP). Since a high level of norepinephrine (NE) is demonstrated in the plasma of SIRS mice, in the present study, the role of NE on the appearance of PMN-II in SIRS mice was studied. Similar to SIRS mice, normal mice became susceptible to CLP-induced infectious complications after inoculation with NE-treated PMN. CCL2 and IL-10 (biomarkers for PMN-II) were equally produced by PMN-II prepared from SIRS mice and NE-treated PMN. However, CCL3 and IL-12 (biomarkers for immunostimulatory PMN, PMN-I) were not detected in culture fluids from either PMN preparation. These results indicate that NE mass-produced in association with SIRS development plays a role on the generation of PMN-II and the appearing PMN-II are responsible, in part, for increased susceptibility of SIRS mice to CLP-induced infectious complications.