Transfusion of stored RBCs synergizes with the inflammatory response to LPS. C57BL/6 mice were infused with a subclinical dose of LPS (E coli 0111:B4 strain; 30 μg per mouse by tail-vein injection) immediately followed by transfusion of 400 μL of fresh RBCs or stored RBCs. Mice were killed 24 hours after transfusion, and plasma cytokines were measured (n = 5 per group). Results are representative of 2 experiments. *P < .05; **P < .01; ***P < .001 compared with mice infused with LPS plus stored RBCs.