Cell-mediated immunity is depressed following cardiopulmonary bypass

Sequential in vitro lymphocyte function tests in 13 patients undergoing cardiac operation were performed to determine factors that contribute to depressed cell-mediated immunity following operation. Lymphocytes were stimulated with phytohemagglutinin (PHA), pokeweed mitogen, concanavalin A (Con A), and mitomycin-treated, pooled, allogeneic lymphocytes (MLC). Mitogen responses were measured by 3H-labeled thymidine incorporation. Circulating levels of T, B, and Fc-receptor lymphocytes were determined by counting E, EAC, and EA rosettes. Serum cortisol was measured by radioimmunoassay. The T-cell-dependent lymphocyte responses (PHA, Con A, and MLC) were significantly decreased 24 hours after operation, and this was accompanied by a 60% decrease in circulating T-cell levels. The PHA, Con A, and MLC responses, and circulating T-cell levels returned to preoperative values one week following operation. Lymphocyte responses to mitogens remained significantly decreased when the number of T cells in the postoperative cultures were adjusted to preoperative levels. This indicates that the T cells remaining after operation were functionally impaired. We conclude that lymphocyte proliferative responses and antigen recognition are significantly depressed following cardiac operation, and that these responses are related to decreased numbers of circulating T lymphocytes and depressed function of the remaining T lymphocytes.