Prolonged storage of purified granulocyte concentrates: Introduction of a new purification method

Background: Use of donor granulocyte concentrate (GC) has been limited due to its short storage time of 6-24 h, which is partially due to residual red blood cells (RBCs) and platelets and the resulting lactate production leading to an acidotic milieu. To increase this storage time, we developed a closed system procedure compatible with standard blood bank technologies to remove RBC and platelets and to enrich the GC. Methods: Standard GCs (sGCs) were sedimented, washed twice with 0.9% sodium chloride (NaCl), and resuspended in blood group-identical fresh frozen plasma. The resulting purified GCs (pGCs) were then stored in platelet bags at a cell concentration of about 5 × 107 ± 1.8 × 107 leukocytes/ml without agitation at room temperature for up to 72 h. Cell count and viability, pH, blood gases, phagocytosis, and oxidative burst were monitored daily. Results: A significant reduction in RBC (98%) through sedimentation, and platelets (96%) by washing, purified the white blood cell (WBC) population and enriched the granulocytes to 96% of the WBC in the pGC. After 72 h of storage, over 90% of the initial WBC count of pGC remained, was viable (>97%), and the granulocytes exhibited a high phagocytosis and oxidative burst functionality, comparable to sGC after 24 h. Conclusion: Purification extends the maximum storage period of GC from 24 to 72 h and may therefore improve the availability of GC and its clinical use.