Adhesion and Migration of Human Polymorphonuclear Leukocytes Across Cultured Bovine Brain Microvessel Endothelial Cells

Adhesion and migration of human polymorphonuclear leukocytes (PMN) across cerebral endothelium were studied in an in vitro model consisting of monolayers of bovine brain microvessel endothelial cells (BBMEC) grown on amniotic stroma or collagen membranes. Polymorphonuclear leukocytes were stimulated to adhere to and migrate across confluent BBMEC monolayers in response to chemotactic gradients produced by formyl-methionyl-leucyl phenylalanine (fMLP), leukotriene B4 (LTB4) or acetyl-glyceryl-ether-phosphorylcholine (AGEPC) placed below the cultures. Under these conditions, PMN adherence to endothelium was 2–10-foldgreater than that observed in the absence of chemoattractants or in the presence of equal concentrations of chemoattractants below and above the cultures . Transendothelial migration of PMN occurred rapidly and at focal points across the monolayers. Scanning and electron microscopic studies revealed that stimulated PMN migrated across the monolayers by first adhering to the apical surface of the endothelium and then moving between adjacent endothelial cells. Following their migrat ion, PMN accumulated beneath the endothelium. The overlying endothelial monolayers showed no evidence of disruption and the interendothelialjunctions appeared intact at the end of the migration period. Weconclude that this in vitro system reproduces the endothelial cell-leukocyte interactions occurring during acute inflammation in vivo and should provide a useful in vitro model for studying the molecular mechanisms underlying these interactions in inflammatory diseases of the central nervous system.