Evaluation of the effectiveness of packed red blood cell irradiation by a linear accelerator

摘要

Irradiation of blood components with ionizing radiation generated by a specific device is recommended to prevent transfusion-associated graft-versus-host disease. However, a linear accelerator can also be used in the absence of such a device, which is the case of the blood bank facility studied herein. In order to evaluate the quality of the irradiated packed red blood cells, this study aimed to determine whether the procedure currently employed in the facility is effective in inhibiting the proliferation of T lymphocytes without damaging blood components.The proliferation of T lymphocytes, plasma potassium levels, and the degree of hemolysis were evaluated and compared to blood bags that received no irradiation. Packed red blood cell bags were irradiated at a dose of 25?Gy in a linear accelerator. For this purpose, a container was designed to hold the bags and to ensure even distribution of irradiation as evaluated by computed tomography and dose-volume histogram.Irradiation was observed to inhibit the proliferation of lymphocytes. The percentage of hemolysis in irradiated bags was slightly higher than in non-irradiated bags (p-value >0.05), but it was always less than 0.4% of the red cell mass. Although potassium increased in both groups, it was more pronounced in irradiated red blood cells, especially after seven days of storage, with a linear increase over storage time.The findings showed that, at an appropriate dosage and under validated conditions, the irradiation of packed red blood cells in a linear accelerator is effective, inhibiting lymphocyte proliferation but without compromising the viability of the red cells. class="kwd-title">Keywords: Blood safety, Hemotherapy service, T-lymphocytesIntroductionTransfusion-associated graft-versus-host disease (TA-GvHD) is a rare and acute delayed transfusion reaction which occurs after the transfusion of blood components; this complication is correlated to a high mortality rate. The main mechanism for the occurrence of TA-GVHD is the transfer of T lymphocytes from the blood donor that damage and promote a response in the tissues of the recipient. After recognizing host tissues as foreign, the cytokines released by transfused T lymphocytes, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF), drive an inflammatory response. These cytokines activate inflammatory cells, including natural killer (NK) cells, macrophages, and other T lymphocytes, resulting in the destruction of host tissues thereby causing TA-GVHD.1,2 Another mechanism for the occurrence of TA-GVHD occurs through donor-recipient HLA incompatibility.3 The development of this transfusion reaction appears to relate to the number and viability of T lymphocytes transfused in blood components (although this number is not yet known), to the level of immunosuppression of the patient, and to the extent that antigens of the HLA system are common to both the donor and recipient.4,5 Therefore, the greater the number of blood components received, the greater the chance of TA-GVHD occurring in at-risk patients.In susceptible patients, TA-GVHD occurs when the number of viable transfused lymphocytes is more than 1?×?104?cells/kg of body weight.3,5 It is known that non-leukodepleted packed red blood cell (PRBC) bags have approximately 2–3?×?109 leukocytes, whereas leukodepleted PRBC bags have from 2–3?×?106 leukocytes. Therefore, even leukodepletion is not able to protect these patients from TA-GVHD.3,6 In situations in which the patient has a healthy immune system, lymphocytes are destroyed. However, in immunosuppressed patients, these cells are not destroyed by the recipient's immune system and so after proliferation and producing cytokines, the lymphocytes may cause a TA-GvHD-related inflammatory response. Thus, the only effective method to prevent this disease completely is to inactivate donor lymphocytes by irradiating blood components.Determination No. 34 of the Ministry of Health of Brazil/National Health Surveillance Agency (ANVISA) states that the irradiation of blood and blood components should be performed in a specific cell irradiator, and that when this equipment is not available, irradiation can be carried out in a linear accelerator used for radiation therapy.7 Using linear accelerators instead of cell irradiators has been the subject of discussion among authors. Although Vetter and Dodd consider the performance of both methods to be similar,8 dose uniformity may fail to meet the quality standards in linear accelerators if the method is not standardized. This was also reported by Janatpour et al. on comparing the irradiation of blood components with X-rays and gamma-rays.9 Bashir et al. demonstrated similar effects in the dosage of potassium and in the degree of hemolysis in red blood cells subjected to X-rays and gamma radiation, and suggested employing linear accelerators in the place of radioactive equipment due to the lower maintenance c