BAL cell counts, lung MPO activity, and microvascular permeability 4 hours after transfusion of unwashed 10-day-old RBCs in endotoxemic mice. (A) Transfusion of 10-day-old RBCs increased airspace neutrophil recruitment compared with transfusion of less than 1-day-old RBCs (P = .015). Lung MPO activity was similar between the 2 groups. (B) Transfusion of 10-day-old RBCs increased lung microvascular permeability compared with transfusion of less than 1-day-old RBCs (P = .021). Data are representative of 3 individual experiments; n = 9 animals in each group.