Effect of Irradiation on Microparticles in Red Blood Cell Concentrates

Changes in microparticles (MP) from red blood cell (RBC) concentrates in the context of irradiation have not been investigated. The aim of this study was to evaluate how irradiation affects the number of MPs within transfusion components. Twenty RBC concentrates, within 14 days after donation, were exposed to gamma rays (dose rate: 25 cGy) from a cesium-137 irradiator. Flow cytometry was used to determine the numbers of MPs derived from RBC concentrates before and 24 hr after irradiation. The mean number of MPs (±standard deviation) in RBC concentrates was 21.9×10⁹/L (±22.7×10⁹/L), and the total number of MPs ranged from 2.6×10⁹/L to 96.9×10⁹/L. The mean number of MPs increased to 22.6×10⁹/L (±31.6×10⁹/L) after irradiation. Before irradiation, the CD41-positive and CD235a-positive MPs constituted 9.5% (1.0×10⁹/L) and 2.2% (263×10⁶/L) of total MPs, respectively. After irradiation, CD41-positive MPs increased to 12.1% (1.5×10⁹/L) (P=0.014), but the CD235a-positive MPs decreased to 2.0% (214×10⁶/L) of the total MPs (P=0.369). Irradiation increases the number of CD41-positive MPs within RBC concentrates, suggesting the irradiation of RBC concentrates could be associated with thrombotic risk of circulating blood through the numerical change.