A. GM-CSF−/− mice received GM-CSF−/−/PU.1Negative macrophages (mAM cells) or GM-CSF−/−,/PU.1Positive macrophages (mAMPU.1+ cells) and WT mice received mAM cells, all by passive intraperitoneal transfusion (n= 15, 15, 18 per group, respectively). Twenty-four hours later, all mice underwent CLP and mortality was evaluated every 12 hr for 7 days. B. GM-CSF−/− and WT mice were injected with either mAM or mAMPU.1+ cells as above (A) (n=12 mice/group). Twenty-four hours later all mice received LPS by intraperitoneal injection and mortality was evaluated every 12 hr for 7 days.