LEUKOCYTE ACTIVATION WITH INCREASED EXPRESSION OF CR3 RECEPTORS DURING CARDIOPULMONARY BYPASS

The effects of cardiopulmonary bypass (CPB) on the expression of leukocyte adhesive receptors, ie, complement receptor type 3 (CR3), were studied in 16 patients. The CR3 expression on leukocytes was determined by time-resolved fluoroimmunoassay on a standardized number of cells isolated from blood samples taken during various times during CPB. The results demonstrated that CR3 expression on leukocytes increased immediately after the start of CPB (p < 0.05), concomitant with an early sharp increase of plasma concentrations of C3a (p < 0.01). After release of the aortic cross-clamp, a second peak of leukocyte CR3 expression was induced (p < 0.05), paralleled by a significant increase of leukotriene B4 (p < 0.05) and elastase (p < 0.05) levels in the late period of CPB. In vitro studies with leukocytes isolated from healthy donors (n = 5) showed a dose-dependent increase of CR3 expression stimulated by zymosan-activated plasma, indicating that the rapid CR3 expression on leukocytes is likely mediated by complement activation. However, the mechanisms for the second peak of leukocyte CR3 expression during CPB remain to be further elucidated. In conclusion, CR3 expression on leukocytes increased immediately after the start of CPB and *as followed by a second peak of expression in the late phase of CPB. Pharmacological blockage of these adhesive receptors might reduce the leukocyte-mediated deleterious effects of CPB.