Changes in lymphocyte subpopulations as a result of cardiopulmonary bypass. The effect of blood transfusion.

Cardiopulmonary bypass is associated with postoperative humoral and cellular immune changes. Postoperative decrease in T helper (CD4), T suppressor (CD8), and B lymphocyte counts; decrease or reversal of the CD4/CD8 ratio; and poor in vitro response to mitogens have also been observed. Similar changes in lymphocyte number and function have also been noted in patients receiving transfusions. To determine whether observed changes after cardiopulmonary bypass are related to the bypass itself or to associated blood transfusions, we conducted a study of lymphocyte subsets in transfused and nontransfused patients. A flow cytometric analysis of seven lymphocyte subpopulations was conducted in 18 patients undergoing bypass, eight of whom did not receive a transfusion. The transfused group comprised recipients of both homologous (n = 8) and autologous (n = 2) blood. Total lymphocytes and lymphocytes with markers for CD3 (pan-T cells), CD4, and CD8 decreased significantly postoperatively independent of transfusion. B lymphocytes decreased postoperatively in both the autologous transfusion and no transfusion groups. However, this trend was not seen in patients receiving homologous blood, and three of these patients had evidence of T cell activation, suggestive of an immune response to homologous transfusion. Bypass produces significant changes in selected lymphocyte subsets. Furthermore, simultaneous homologous blood transfusion may specifically elicit an immune response in some patients undergoing cardiopulmonary bypass.