Release of WBC-derived IL-1 receptor antagonist into supernatants of RBCs:influence of storage time and filtration

BACKGROUND: Transfusion-associated immunodepression may be related to the t ransfer of immunoinhibitory cytokines with blood components. STUDY DESIGN AND METHODS: After evidence of increasing concentrations of IL -l receptor antagonist (IL-l RA) but not of IL-10 was obtained in supernata nts of stored RBC units that were WBC-reduced by centrifugation (C-RBCs) in a pilot study, IL-l RA concentrations were determined weekly in supernatan ts of C-RBCs and in units that underwent prestorage WBC reduction by inline filtration (F-RBCs) over a 49-day storage. For assessing total IL-l RA con tent, complete cell lysis by repeated freezing and thawing was done. The re sults were related to the changes in WBC count during storage. The dependen cy of IL-l RA content on preparation procedures was assessed. RESULTS: The prestorage IL-l RA concentration in C-RBCs (859 +/- 218 pg/mL) was significantly higher than in F-RBC (75 +/- 13 pg/mL). Whereas no chang es were seen in F-RBCs during storage, IL-l RA levels in C-RBC supernatants drastically increased to levels about 50 times those in normal plasma (16, 327 +/- 2,686 pg/mL on Day 49). Follow-up analysis revealed stringent corre lation between IL-1RA release into supernatants and the current loss of WBC s (r = 0.79, n = 42; p<0.001). The total IL-l RA content did not change dur ing storage and was directly dependent on prestorage WBC count. Preparation procedures altered the IL-l RA content only by WBC reduction. CONCLUSION: The immunosuppressive cytokine IL-1 RA is transmitted by RBCs i n relation to WBC content and storage time.