Background: The immunomodulatory effects of allogeneic blood transfusions have been attributed to the white cells (WBCs) present in the cellular blood components transfused to patients.
Study design and methods: The effect of the transfusion of allogeneic red cells (RBCs) or allogeneic prestorage WBC-reduced RBCs (WBC-reduced RBCs) on host immune responsiveness was evaluated by measuring the lymphocyte subsets and the in-vitro cytokine production in response to phytohemagglutinin stimulation of WBCs of orthopedic surgery patients. Forty-seven patients undergoing hip replacement surgery were randomly assigned to receive allogeneic RBCs (n = 17) or WBC-reduced RBCs (n = 14; 99.95% WBC removal). Sixteen patients were not transfused. Patient blood samples taken before surgery and on Days 1 and 4 after surgery were tested for complete blood count, lymphocyte subset analysis, and measurement of cytokine levels.
Results: After surgery, the lymphocyte count was significantly decreased in patients transfused with > or = 3 units of allogeneic RBCs (2.0 +/- 0.5 vs. 1.3 +/- 0.3 x 10(9)/L; p = 0.017), but not in patients transfused with > or = 3 units of WBC-reduced RBCs (2.0 +/- 0.9 vs. 1.7 +/- 0.8 x 10(9)/L). Compared with preoperative levels, on Day 4 after surgery, patients transfused with > or = 3 units of allogeneic RBCs also had a decrease in the number of natural killer cells (0.07 +/- 0.05 vs. 0.04 +/- 0.03 x 10(9)/L; p = 0.018). Postoperatively, interleukin-2 was decreased in one patient who received WBC-reduced RBCs compared with that in four patients transfused with allogeneic RBCs (p = 0.32), and eight untransfused patients (p = 0.01). On Day 4, about 70 percent of patients transfused with allogeneic RBCs showed a 20-percent decrease in the interferon gamma level.
Conclusion: Taken together, these data support the hypothesis that transfusion of > or = 3 units of allogeneic RBCs is associated with early postoperative lymphopenia in otherwise healthy individuals undergoing surgery. These findings were not observed in those individuals transfused with RBCs that had undergone prestorage WBC reduction.