Impact of shed blood products on stimulated cytokine release in an in vitro model of transfusion

Background Blood transfusion is reported to suppress the recipient's immune system. To avoid allogenic transfusion, post‐operative shed blood retransfusion is a commonly used method. The aim of this study was to investigate the dose‐related impact of post‐operatively collected shed blood products on the stimulated cytokine release in an in vitro model of transfusion. Methods Venous blood samples obtained from 20 patients undergoing hip arthroplasty were mixed with post‐operatively collected unprocessed, processed, and irradiated shed blood as well as normal saline as a control. Shed blood was processed by centrifugation and separating the cellular fraction from the soluble fraction and washing the cellular fraction with phosphate buffered saline to eliminate any cell fragments and other substances. Mixing ratios were 1 : 3, 1 : 1, and 3 : 1. Endotoxin‐stimulated release of Tumor Necrosis Factor‐alpha (TNF‐α) was measured after 24 h of culture by enzyme‐linked immunosorbent assay. Results Unprocessed, irradiated shed blood and the soluble fraction caused a significant suppression of stimulated TNF‐α release compared to control. The addition of the cellular shed blood fraction had no significant influence on the TNF‐α release compared to control. Conclusion Shed blood and its components caused a dose‐independent immunomodulation as indicated by a suppressed stimulated TNF‐α release. Leukocytes seem to play a minor role, as we observed a sustained suppression after transfusion of γ‐irradiated shed blood. Only the elimination of soluble factors by centrifugation and followed by an additional washing step prevented the observed suppression of TNF‐α. Thus, we assume that washing of shed blood can prevent potential detrimental effects.