Evidence of immunocyte stimulatory molecule(s) in plasma of patients undergoing cardiopulmonary bypass

Previous studies have demonstrated that cardiopulmonary bypass (CPB) induces a diffuse inflammatory response as well as cellular immunosuppression. To better characterize and localize this immune dysfunction, we examined the effect of CPB-exposed plasma on granulocytes and macrophages obtained from normal blood. Pre- and intra-CPB blood samples were obtained from seven patients admitted for elective coronary artery bypass graft surgery. Plasma from the pre-CPB samples served as controls. Evaluation of the behavior of the granulocytes and macrophages was based on their ability to respond by way of chemokinesis or chemotaxis versus a stimulus (D-Ala2-Met5-enkephalin [DAME], interleukin[IL]-1 alpha). Non-CPB exposed granulocytes and macrophages were found to be capable of chemotaxis when stimulated by DAME and by IL-1 alpha. Subjected to CPB, these cells were significantly more activated than controls (p < 0.005). They behaved in a chemokinetic fashion when incubated with cell-free CPB plasma and did not respond to either DAME or IL-1 alpha in a chemotaxic situation when compared with controls (p < 0.005). Plasma subjected to CPB as stimulus provoked a chemotaxic response in non-CPB exposed cells. Taken together, these results indicate that at least one type of potent signal molecule was present, and possibly generated, in plasma subjected to CPB.