DFO treatment decreases the proinflammatory response induced by transfusion of stored RBCs. (A) Mice were pretreated with a PBS vehicle control (n = 28) or with 3 mg of DFO, with (n = 15) or without (n = 31) the addition of equimolar ferric citrate, immediately before transfusion with stored RBCs (400 μL). Mice were killed 2 hours after transfusion, and plasma cytokine levels were measured; *P < .05; **P < .01; ***P < .001 compared with mice infused with PBS vehicle and transfused stored RBCs. (B) Bioluminescence was quantified for 24 hours after transfusion over the hepatosplenic region of SAA1-luciferase reporter mice transfused with 200 μL of fresh RBCs (n = 3; ), the PBS vehicle control and stored RBCs (n = 3; ■), or 3 mg of DFO and stored RBCs (n = 6; ); P = .095 at 4 and 6 hours after transfusion comparing vehicle-treated and DFO-treated mice. (C) Proposed mechanistic pathway (the “iron hypothesis”) explaining how transfusion of older stored RBCs may induce adverse effects in patients. Transfusion of stored, but not fresh, RBCs delivers an acute bolus of RBCs and RBC-derived iron to the monocyte/macrophage system resulting in oxidative stress and inflammatory cytokine secretion. Some of the macrophage-ingested iron is also released back into the circulation (ie, NTBI) where it can also cause oxidative damage and enhance bacterial proliferation. SIRS indicates systemic inflammatory response syndrome.