Purified Granulocyte Concentrates from Buffy Coats with Extended Storage Time

Granulocyte concentrates (GCs) are usually prepared by single-donor apheresis after G-CSF pretreatment and have to be transfused within 24 h after cell collection because of the rapid decrease in pH and cell survival due to high lactate production by red blood cell contamination. GCs pooled from buffy coats of whole blood donations could improve the availability of these products. Methods to reduce red blood cell and platelet contamination may improve storability. We developed a manufacturing process for pooled GCs and investigated cell viability and functionality over time.

Six ABO blood group-identical buffy coats were pooled. Subsequently, the red blood cells spontaneously sedimented after the addition of hydroxyethyl starch. The resulting leukocyte-enriched supernatant was washed twice with saline to reduce platelets and was resuspended in ABO-identical donor plasma. The leukocyte concentrate was transferred to a platelet storage bag and stored up to 72 h at 20-24°C w/o agitation. Cell count and viability, pH, blood gases, phagocytosis, and oxidative burst activity were monitored.

The number of red blood cells and platelets was reduced to 0.4% and 6.1% of the baseline levels. About 50% of the original present leukocytes could be extracted (n = 76). In the course of 72 h of storage, there were no significant changes in white blood cell counts (p = 0.12). The viability exceeded 98% during the entire period. The rate of granulocytes performing phagocytosis and oxidative burst remained above 95% anytime.

GCs prepared from pooled buffy coats provide a precious alternative to granulocytes obtained from apheresis. Reduction of red blood cells and platelets by more than 90% extends the maximum shelf life of GCs from 24 h to 72 h. For a therapeutic dose of at least 1 × 10¹⁰ granulocytes, 15-20 buffy coats are required.