Stored packed red blood cell transfusion up-regulates inflammatory gene expression in circulating leukocytes

Background Data: The transfusion of more than 6 units of packed red blood cells (PRBCs) within the first 12 hours of injury is the strongest independent predictor of multiple organ failure (MOF). This suggests that stored blood contains bioactive factors that may modify the immuno inflammatory response. Methods: To simulate postinjury major transfusions ex vivo, we obtained whole blood from 4 healthy adults and divided it into four 7-mL groups (I-IV). Group I was not diluted. Group II had 7 mL of 0.9% sterile saline (SS) added. Group III received 3.5 mL each of leuko-reduced stored PRBC and SS (simulating a major transfusion). Group IV received 3.5 mL each of SS and a hemoglobin-based oxygen carrier (PolyHeme) to evaluate the effects of hemoglobin alone. The hemoglobin content in groups III and IV was measured to be equal. Total leukocyte RNA was purified, and its gene array profiles were obtained. Results: Of the 56,475 oligonucleotide probe sets interrogated, 415 were statistically different (P < 0.001). Fourteen of the 415 probe sets were inflammatory-related. The PRBC group had a significantly different expression profile compared with the others and included up-regulation of the interleukin-8, toll-like receptor 4, cryropyrin, prostaglandin-endoperoxide synthase-2, and heparinase genes. Conclusions: PRBCs activate inflammatory genes in circulating leukocytes, which may be central to the pathogenesis of the adverse inflammatory responses that lead to postinjury MOF.