Abstract: Objective To investigate the apoptosis status of lymphocytes exposed to X-ray irradiation and evaluate changes in the quality of red blood cells (RBCs) at different preservation periods post-irradiation, thereby assessing the efficacy of X-ray irradiation and determining the optimal timing for clinical application of irradiated RBCs. Methods Thirteen blood samples donated by voluntary donors were selected. For each sample, 5 mL of whole blood was collected into four test tubes and divided into four groups: day 0 (d0), day 7 (d7), day 14 (d14) and day 21 (d21). Lymphocytes were extracted during the corresponding preservation periods and further categorized into a lymphocyte control group and an irradiation group. The irradiation group was exposed to 25 Gy X-ray irradiation, and the apoptosis rate of lymphocytes in each group was measured using flow cytometry. The remaining blood was processed into leukoreduced suspended RBCs and divided into an RBCs control group and irradiation groups (d0, d7, and d14).Each irradiation group was exposed to 25 Gy X-rays during the respective storage periods. Changes in potassium (K⁺), free hemoglobin (FHb), adenosine triphosphate (ATP), and 2, 3-diphosphoglyceric acid (2, 3-DPG) were detected on days 0, 7, and 14 post-irradiation and during the corresponding preservation periods. Results X-ray irradiation effectively induced lymphocyte apoptosis, with the apoptosis rate gradually decreasing as the preservation time of whole blood increased.The apoptosis rates of lymphocytes in the d0, d7, and d14 irradiation groups were significantly higher than those in the control groups during the same periods (P<0.05). However, no significant difference in apoptosis rate was observed between the d21 irradiation group and the control group (P>0.05). The K⁺ content in the d0 and d7 irradiation groups on days 7 and 14 post-irradiation, as well as in the d14 irradiation group on days 0, 7, and 14 post-irradiations, was significantly higher than that in the corresponding control groups (P<0.05). No statistically significant differences were observed in the other groups (P>0.05). The FHb content in the d7 irradiation group on day 14 post-irradiation and in the d14 irradiation group on days 7 and 14 post-irradiation was significantly higher than that in the corresponding control groups (P<0.05). No statistically significant differences were observed in the other groups (P>0.05).The ATP content in the d14 irradiation group was significantly lower than that in the control group on day 14 post-irradiation (P<0.05). No statistically significant differences were observed in the other groups (P>0.05). There were no statistically significant differences in 2, 3-DPG content between the irradiation groups and the control group (P>0.05). Conclusion Exposure to 25 Gy X-rays has a significant effect on lymphocytes within the first 14 days of preservation, inducing apoptosis. The timing of RBCs irradiation influences blood quality at different preservation periods post-irradiation. When administering irradiated RBCs to special patients, careful consideration should be given to the timing of irradiation and the preservation period post-irradiation.

Key words: X-ray, Irradiation, Lymphocyte, Apoptosis, Red blood cell, Blood quality