Title: Leukocyte integrin expression in patients undergoing cardiopulmonary bypass
Abstract: <h2>Abstract</h2> <i>Background</i>. The recruitment of leukocytes to vascular endothelium is controlled by adhesion events mediated through the β<sub>2</sub> integrins, whereas the response of extravasated leukocytes within the tissues is controlled through the β<sub>1</sub> integrins. Although cardiopulmonary bypass (CPB) has been shown to be associated with a systemic inflammatory response and elevated levels of β<sub>2</sub> integrins on leukocytes, its effect on the β<sub>1</sub> integrins is not known. This study investigated the effect of the protease inhibitor aprotinin on the expression of the β<sub>1</sub> and β<sub>2</sub> integrins on circulating leukocytes in patients undergoing CPB. <i>Methods</i>. Patients undergoing primary elective coronary artery bypass grafting were randomized into full-dose aprotinin or placebo groups. Blood samples were obtained at nine time points preoperatively, intraoperatively, and up to 6 days postoperatively. The surface expression of the β<sub>1</sub> integrins VLA-1, -3, -4, -5, and -6 and of the β<sub>2</sub> integrins CD11a/CD18, CD11b/CD18, and CD11c/CD18 was measured by flow cytometry on gated neutrophil and monocyte subpopulations in whole blood. <i>Results</i>. Expression of the β<sub>1</sub> integrins was not significantly altered during the study period and, therefore, aprotinin had no effect on the expression of these molecules. Of the β<sub>2</sub> integrins, CD11b/CD18 expression was significantly increased on neutrophils at 15 minutes after onset of CPB in the placebo group (<i>p</i> < 0.01) but not in the aprotinin group. <i>Conclusions</i>. This study showed that expression of the β<sub>1</sub> integrins on neutrophils and monocytes did not alter during the first 6 days after CPB. Expression of the β<sub>2</sub> integrin CD11b/CD18 increased significantly on neutrophils during CPB in control patients but not in patients treated with full-dose aprotinin.