Impact of storage at 22°C and citrate anticoagulation on the cytokine secretion of mononuclear leukocytes

Background and Objectives: Peripheral blood mononuclear cells (PBMC) and cytokines accumulating in platelet concentrates (PC) during storage have been implicated in causing non-hemolytic transfusion reactions, in particular after prolonged PC storage. We investigated the impact of major storage parameters, such as storage time, anticoagulation and temperature, on the capability of PBMC to secrete cytokines. Materials and Methods: In a first study, PBMC from whole blood donations (n = 16) were exposed to standard PC storage conditions: 22 degrees C, citrate phosphate dextrose (CPD) anticoagulation. Secretion of the cytokines interleukin-1 beta (IL-1 beta), IL-2, IL-6 and interferon-gamma (IFN-gamma) on mitogenic stimulation was measured directly after blood donation and after 1, 3 and 5 days of storage. In a second study, paired whole blood samples (n = 24) were investigated for the mitogenic induction of IL-2, IL-6, IFN-gamma and IFN-alpha. Cytokine values were compared with respect to incubation temperature (22 vs. 37 degrees C) and anticoagulant (CPD vs. lithium-heparin). Results: PBMC stored at 22 degrees C with CPD anticoagulation showed an altered cytokine secretion pattern in comparison to freshly donated cells. After storage for 3 days, IL-2 release was decreased (p < 0.05) and after 5 days secretion of all cytokines was significantly decreased, though still detectable (p < 0.01). In the second study, CPD anticoagulation resulted in a significantly impaired cytokine secretion compared with lithium-heparin. Cytokine secretion at 22 degrees C were significantly lower (p < 0.001) compared with 37 degrees C for both anticoagulants. Conclusion: Storage of PBMC at 22 degrees C with CPD leads to an impaired cytokine response, but PBMC are still capable of secreting cytokines after 5 days of storage. PBMC remain a potential source of cytokines even after 5 days of storage in CPD at 22 degrees C.