DOWN-REGULATION OF SURFACE MONOCYTE LIPOPOLYSACCHARIDE-RECEPTOR CD14 IN PATIENTS ON CARDIOPULMONARY BYPASS UNDERGOING AORTA-CORONARY BYPASSOPERATION

Objectives: Major operative trauma like aorta-coronary bypass operatio n may lead to postoperative immunodisturbance, putting the patient at an increased risk for infection and sepsis, The monocyte/macrophage sy stem and the endotoxin receptor CD14 are important in the early recogn ition and elimination of invading bacteria. The aim of this study was to analyze changes in membrane-associated CD14 and soluble CD14 during and after cardiac involving cardiopulmonary bypass, Methods: We studi ed numbers of leukocytes, monocytes, and monocyte subpopulations, expr ession of monocyte membrane-associated CD14 and plasma levels of solub le CD14 in 10 patients (63 +/- 8 years of age), who underwent elective cardiopulmonary bypass. Results: Cardiopulmonary bypass induced marke d postoperative monocytosis, which was maximal 20 hours after the oper ation (485 +/- 242 cells/mu l before, 1080 +/- 264 cells/mu l 20 hours after surgery). Expression of membrane-associated CD14 on classical C D14++ monocytes decreased significantly by 40%, reaching a nadir 20 ho urs after surgery (p < 0.05), At the time of maximal membrane-associat ed CD14 suppression, the levels of soluble CD14 measured by enzyme-lin ked immunosorbent assay were clearly increased (3.2 +/- 1.0 mu g/ml be fore versus 5.6 +/- 1.0 mu g/ml 20 hours after, p < 0.001). No signifi cant change of the percentage of small (alpha) and large (beta) forms of soluble CD14 was found. Conclusions: Cardiopulmonary bypass leads t o reduced membrane-associated CD14 expression on peripheral blood mono cytes and increased levels of soluble CD14 through shedding or secreti on of membrane-associated CD14 from the cell surface. These findings i ndicate that bypass is associated with significant monocyte activation .