BAL cytokines, airspace neutrophil counts, and lung MPO activity in endotoxemic mice 4 hours after transfusion of 1- to 2-day-old, stored RBC. (A) RBC transfusion increased BAL MIP-2 compared with HEX controls (P = .009). BAL KC, IL-6, and TNFα were not increased after RBC transfusion (P = .232, .281, and .955, respectively). (B) Total BAL mononuclear cell counts were not different between the 2 groups (P = .601). RBC transfusion increased airspace neutrophils compared with HEX (2433 vs 255, P < .001). Lung MPO activity was similar between the 2 groups. (C,D) GR-1 staining of lung sections from animals transfused with 1- to 2-day-old RBCs show increased interstitial and airspace neutrophils compared with HEX transfused controls. Magnification ×400. Data are representative of 3 independent experiments; n = 9-12 animals per group.