SUPERNATANT FROM STORED RED-CELLS ACTIVATES NEUTROPHILS

Bioreactive substances including cytokines and lipids accumulate durin g storage of red blood cells (RBCs) but their clinical importance is u ncertain. The goal of this study was to evaluate the effect of stored RBC supernatant on neutrophil activity in vitro. Packed RBCs (PRBCs) w ere collected and divided into two aliquots, one leukodepleted and the other nonleukodepleted. Plasma supernatant from PRBCs were collected on days 1, 8, 15, 29 and 35 and its effect on neutrophil expression of CD11b, CD16 and oxidative burst was measured by flow cytometry. Level s of tumour necrosis factor alpha (TNF alpha) and interleukin-8 (IL-8) were also measured. The supernatant from PRBC units stored for greate r than 15 days activated and primed neutrophils as evidenced by an inc rease CD11b and CD16 expression and oxidative burst. The greatest effe ct was seen in the oldest concentrates (35-day-old) (P < 0.008). Leuko depletion abrogated the effects of stored supernatant on CD11b and CD1 6 expression (P < 0.02) but did not reduce priming of the neutrophil o xidative burst (P > 0.1). Very low levels of IL8 and TNF alpha were de tected in stored supernatants. Stored PRBC supernatant contains substa nces which directly enhance neutrophil expression of adhesion protein CD11b, CD16 and prime neutrophil oxidative burst. The exceedingly low level of IL8 and TNF alpha found in this study suggests that other fac tors may play a more important role in neutrophil priming and activati on.