Effects Of Gamma Irradiation On The Quality Of Blood And Clinical Applications Of Gamma-radiated Blood Products

Objective:Transfusion associated graft versus host disease(TA-GVHD) is an often fatal complication occurring in severely immunocompromised patients,including those with congenital immunodeficiencies,those who have undergone bone marrowtr ansplantation(BMT),and those who have received aggressive cancer chemotherapy. Recently,it has been shown that nonimmunocompromised patients who have received blood from donors homozygous for shared HLA haplotypes have developed TAGVHD.Irradiation of cellular blood products using a gamma source inactivates T cells,so it is the only effective method for preventing TA-GVHD.But the selection of an best appropriate dose of gamma irradiation that eliminates the risk of TA-GVHD while preserving the quality of the transfused product remains an issue.Based on data showing the elimination of T-cell-mediated allogeneic reactivity in the mixed lymphocyte culture(MLC),many blood banks have been irradiating blood with 15Gy.A case of TA-GVHD has been reported in a BMT patient who had received packed red blood cells(RBCs) reportteod have been irradiated at 20Gy.Two other cases of TA-GVHD after transfusion of blood components reported to have been irradiatedat 15 and 20 Gy have also been described.We have therefore focused our attention on better delineating the radiation dose that is needed to inactivate T cells when irradiating RBC units.Gamma,representing ionizing radiation,break the DNA molecules of T lymphocytes and prevent the latter from inducing an immunologic response in the recipient.Blood irradiation incorporate one to four gamma-ray sources,usually 137Cs.In addition to damaging T lymphocytes,irradiation also damages other blood cells such as RBCs,PLTs,and granulocytes.It is still unclear,however,what dose eliminates the risk of TA-GVHD while preserving the quality of the transfused product.Brugnara and Churchill,with a 137Cs source,demonstrated a time-and dose-dependence effect on the external K⁺ level in the RBCs units Irradiated with 10,20,and 30 Gy.Additionally, other studies demonstrated that the increase of extracellular K⁺ level is one of the more apparent effects of ionizing radiation on the RBCs units.Ramirez and coworkers demonstrated that 30Gy is sufficient to increase plasma K⁺ levels from 2.2mmol/L on day 0 to 31.0 mmol/L on day2 and to 68.0 mmol/L on day 14.Davey and colleagues demonstrated that this dose is sufficient to increase plasma K⁺ levels in RBCs units from 1.6mmol/L on day 0 to 78.01mmol/L on day 42 of storage.Mintz and Anderson reported that RBCs units irradiated with 30Gy and stored for 35 days have extracellular K⁺ level of 68 mmol/L.Brugnara and Churchill irradiated RBCs units with dose of 10,20,and 30Gy.Between Days 25 and 30 postirradiation,they observed an extracellular K⁺ level of approximately 105 mmol/L in RBCs units irradiated with 30Gy.Goes and Ottoboni observed an extracellular K⁺ level of 2.4,20.0,45.0,54.0,and 55.0 mmol/L on day o,2,14,35,and 42 of storage,respectively,in RBCs units irradiated with 30Gy.Hillyer and colleagues observed an external K⁺ level of 57.0mmol/L in RBCs units irradiated with 35Gy on Day 42 postirradiation.Ramirez and coworkers also showed that the elevation in plasma-free Hb levels provoked by 30Gy became more evident only after 15 days of storage.Similarly,Davey and associates observed a significant increase in plasma-free Hb levels of 623.1mg/dl in RBCs units irradiated with 30Gy and stored for 45 days.Mintz and Anderson observed a free Hb level of 314.0mg/dl in RBCs units irradiated with 30Gy and stored for 34 days.In all the above-cited studies,we do not exclude the necessity of evaluating the RBCs lesion after irradiation.The reported cases of TA-GVHD have recently been summarized.To date,it has been documented after transfusion of unirradiated blood components to at least 87 patients:in patients with severe combined immunodeficiency,thymic hypoplasia,and Wiskott Aldrich syndrome premature newborns and those with erythroblastosis fetalis; patients with hematologic malignancies including Hodgkin's and non-Hodgkin's lymphomas,acute myelocytic and lymphoblastic leukemias,chronic lymphocytic leukemia,and aplastic patients with solid tumors including neuroblastomas, glioblastoma,rhabdomyosarcoma,cervical carcinoma,small cell lung cancer,and germ cell tumor;patients after cardiac surgery and cholecystectomp-60;and in an apparently healthy 22-year-old woman.This syndrome has developed after neonatal exchange and intrauterine transfusions;and after transfusion of whole blood,fresh(nonfrozen) plasma,red blood cells,and platelets.Leukocytes harvested from normal donors and from donors with chronic myelocytic leukemia transfused to patients with hematologic malignancies have also been implicated in TA-GVHD.TA-GVHD results in an overall mortality of 84%t a median of 21(8 to 1,050) days after transfusion。To assess current transfusion medicine practices regarding gamma irradiation of blood products,we must survey clinical applications of gamma-radiated blood products.Materials and methods:From June 2008 to November 2008,45,249 units whole blood were collected in ACD-B bags in the Blood Center of Zhejiang Province.Then they were centrifugated by 4790×g for 12 minutes to prepare red blood cell suspensions(RBCs). They were stored at 2-6℃in the refrigeratory.According to the hospital appointments, blood products were irradiated using 25Gy ¹³⁷Csγ-ray(Gammacell 3000ELAM,MDS Nordion,Canada)for 2 minutes 50 seconds.A sample of RBCs unit,approximately 20ml was collected from each blood bag of 173 RBCS units with a sterile connecting system(Baxter) before and after irradiation to monitor the quality.Lymphocytes were isolated by discontinuous gradient centrifugation and stimulated in vivo in a culture with PHA.In each sample,IL-2,IFN-γ,TNFa,free hemoglobin(FHb),extracellular potassium(K +) ions,ATP and 2,3-DPG content was determinated,respectively.TO analyse the main clinical application of irradiated RBCs,the incidence of TA-GVHD was observed in high-risk patients with TA-GVHD after transfusion.Results and conclusions:Our study shows:(1) Gamma ray at 25Gy showed a 96.15±1.91%inhibitive effect on lymphocytes;(2)Gamma ray at 25Gy could cause significant changes in the IL-2,IFN-γ,TNFa,but not FHb and ATP;(3) Extracellular K⁺ level increased and 2, 3-DPG level decreased generally;(4)There have been no reported cases of TA-GVHD in patients for transfusion.Therefore,conclusions of this study are drawn as follows:(1) 25 Gy137Cs gamma irradiation both inhibits lvmphocytes and effects on other blood components were general. (2) RBCs irradiated by 25 Gy137Cs can prevent TA-GVHD valudiatly.