Increased Expression of Leucocyte Adherence‐Related Glycoproteins by Polymorphonuclear Leucocytes during Phagocytosis of Staphylococci on an Endothelial Surface

Abstract

Phagocytosis of Staphylococcus aureus by human polymorphonuclear leucocytes (PMN) on the surface of endothelial cells is accompanied by adherence of the PMN to the endothelial surface and detachment of the endothelial cells from the culture monolayer. We studied the role of the leucocyte adherence-related glycoproteins (Leu-CAM: Mo1/LFA-1/150,95 or CD11a-c-CD18 complex) in these processes. Phagocytosis of S. aureus induced increased expression of the common beta chain (CD18) of Leu-CAM as demonstrated by flow cytometric analysis of PMN treated with a monoclonal antibody (MoAb) (CLB-LFA-1/1) directed against CD18 and fluorescein isothiocyanate (FITC)-conjugated anti-MoAb. This same MoAb also inhibited the increased adherence of the PMN to the endothelial cells which occurs during phagocytosis. Blocking of adherence during phagocytosis with MoAb CLT-LFA-1/1 had no effect on the detaching activity of the PMN on the endothelial cells. We conclude that adherence of PMN to endothelial cells during phagocytosis of S. aureus is mediated by the Leu-CAM complex. Adherence through the Leu-CAM, however, is not necessary for endothelial damage by the phagocytosing PMN.