A simple method for preparing neocyte-enriched leukocyte-poor blood for transfusion-dependent patients

Recent treatment for patients with thalassemia and chronic anemia involves transfusion of young red cells (YRBCs) or "neocytes." We developed a technique enabling YRBCs to be separated based on their buoyant density in autologous plasma during centrifugation. Following this procedure, measurement of pyruvate kinase (PK), an age-dependent red cell enzyme, showed neocyte enrichment in the top one-third of the RBC layer corresponding to a mean of 47.5 percent of the total PK present in the unfractionated unit. To provide a neocyte transfusion preparation with an acceptable hemoglobin content, the top one-third fraction from each of three bags of blood was pooled. Leukocytes were removed from this "neocyte unit" by an initial sedimentation with 6 percent hydroxyethyl starch (HES) followed by filtration through a filter (IG 500, Imugard). This process resulted in removal of 99.3 +/- 0.5 percent (mean +/- SD) of the leukocytes with a mean RBC recovery of 89.5 +/- 5.5 percent and a final hemoglobin content of 53.4 +/- 2.3 g. Tests for plasma-free hemoglobin and HES in the supernatant of the final transfusion product gave acceptable mean values of 28 mg per dl and 3.0 mg per ml. Autologous mean RBC survival of Cr51-labeled YRBC fractions was 41.8 +/- 2.9 days (n = 5). This technique yields neocyte enrichment superior to that achieved using a cell processor (model 2991, IBM) and has the added advantage of being less costly to prepare ($45.00 [1984] U.S. per YRBC unit as compared to an estimated $135.00 [1984] U.S., IBM) and more economical in terms of blood use.