Laparotomy And Laparoscopy Diversely Affect Macrophage-associated Antimicrobial Activity In A Murine Model

Objective:Surgical intervention-related trauma contributes largely to the development of postoperative immunosuppression and reduced resistance to secondary bacterial infection. Phagocytosis is a key factor of host resistance to pathogenic microorganisms. As the major phagocytic cells of the innate immunity, macrophages detect the intrusion of pathogens through the function of a variety of phagocytic receptors such as Fey receptors, complement receptor (CR), and integrate pathogenic microorganisms to activate a series of intracellular signal transduction pathways. At last, pathogenic microorganisms and necrotic cells are cleared. This study aims to compare the impact of laparotomy with that of laparoscopy on macrophage-associated bactericidal ability and examine whether laparotomy renders the host more susceptible to bacterial infection.Materials and Methods:Balb/c mice were randomized into control (n=70), laparotomy (n=70) and laparoscopy groups (n=70). Phagocytic receptor expression was assessed by FACS analysis. Macrophage-mediated bacterial uptake, phagocytosis and killing were determined after macrophages were chased with gram-negative or gram-positive bacteria. Bacterial clearance was assessed after mice were challenged with live E. coli or S. Aureus.Results:Laparotomy, but not laparoscopy, significantly down regulated CR3expression on macrophages, diminished macrophage-induced uptake and phagocytosis of E. coli and S. aureus, and impaired macrophage-mediated intracellular bacterial killing. Consistent with this, mice that underwent laparotomy displayed substantially higher bacterial counts in the blood and visceral organs following bacterial infection, whereas mice subjected to laparoscopy did not show any defects in their bacterial clearance. Conclusion:Laparotomy has an adverse effect on host innate immunity against microbial infection by impairing macrophage-mediated phagocytosis and killing invaded bacteria. By contrast, laparoscopy appears to preserve macrophage-associated bactericidal ability, thus alleviating the development of postoperative immunosuppression.