Sex differences in survival after endotoxin. N5 C57BL/6 females (solid lines) and males (dotted lines) from the colonies used for the studies in Figures 2, 3, 4, 5, 6 were injected intraperitoneally with high-dose LPS (60 mg/kg; left) or low-dose LPS (30 mg/kg for females, 20 mg/kg for males; right) and monitored for 26 and 72 hours, respectively. P values as determined by log-rank test are shown only when less than .05.