Age-associated difference in plasma APC levels during endotoxemia. (A) Young (4 months, n = 6) and aged (24 months, n = 4) C57BL/6 mice were sacrificed 12 hours after LPS injection (2.5 mg/kg, intraperitoneal). Plasma APC levels were determined by immunocapture assay. For controls, plasma samples from young and aged mice (n = 4, each group) without LPS injection were assayed for APC. (B) Plasma APC levels were compared 12 hours after LPS injection in young mice with a high dose (20 mg/kg) versus aged mice with a low dose (2.5 mg/kg; n = 4 in each group). Data are mean ± SD. *Statistical significance (P < .05). **Statistical significance (P < .01).