Recent reports have highlighted that allogeneic blood transfusions decrease immune responses and affect patient outcomes. However, the effects of allogeneic red blood cell transfusions on the composition of immune cells are unclear. We aimed to clarify the alterations in host immune cells in patients who received allogeneic red blood cell transfusions during the perioperative period of cardiovascular surgery.

Eight non-transfused, 22 intraoperative autotransfusions, and 36 allogeneic red blood cell-transfused patients undergoing surgery were grouped, and lymphocyte subsets were analyzed using flow cytometry. Blood samples collected before surgery, approximately 1-week, and 1-month after surgery were used for analysis. Surgical parameters, operation time, blood loss, and length of hospital stay were also assessed.

The group receiving transfusions showed statistical significance compared to non-transfused in the above-mentioned surgical parameters. When comparing the autologous and allogeneic transfusion groups, only the allogeneic red blood transfusion group had a longer hospital stay. In comparing preoperative and 1-week and 1-month postoperative samples, there were almost no differences in CD4, CD20, or NK counts between the autotransfusions and the allogenic red blood cell transfusion groups. In contrast, a significant decrease in lymphocyte count was observed in the allogenic red blood cell transfused group 1-week postoperatively compared to preoperatively. Moreover, the number of CD8 + cells was statistically lowest in the allogeneic transfusion group 1 week after the operation.

Our results suggest that allogeneic red blood cell transfusion could alter immune cell composition especially CD8 + cells, potentially impacting immune function.