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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Transfusion. 2013 Apr 8;53(12):10.1111/trf.12203. doi: 10.1111/trf.12203

Figure 2. Neutrophils release extracellular DNA traps in RBC units.

Figure 2

(A) MPO in supernatants was detected in RBC units stored for 42 days (n=6). Leukoreduction of RBCs units (n=6) greatly reduced the amount of extracellular MPO. (B) Histone-MPO complexes were detected in supernatants of non-leukoreduced RBC units (n=5). Controls lacked either anti-histone or anti-MPO antibodies. The presence of histone-MPO complexes suggests that neutrophils undergo NETosis during blood storage. (C) Analysis of nuclear size of blood smears from fresh blood or RBC units stored for 14–16 days. Blood smears showed larger DNA staining in stored (n = 304) compared to fresh blood (n = 61). (D) Identification of NETs by immunocytochemistry. Blood smears of 14–16 day old RBC units were stained for myeloperoxidase (green) and DNA (blue). Neutrophils were identified as MPO positive cells with small nuclei (left panel). Neutrophils undergoing NETosis were characterized as MPO-positive cells with disintegrated nuclei (arrows, middle panel) and NETs were identified as an extracellular DNA web containing MPO (right panel). Bar represents 50 μm. Data are presented as mean. P-values are calculated using (A, C) Mann-Whitney test and (B) ANOVA (* P < 0.05, # P< 0.01, § P < 0.001).