We investigated the mode of bovine endothelial cell death induced by lipopolysaccharide (LPS). Inter-nucleosomal DNA fragmentation was observed indicating apoptotic cell death. Apoptosis was confirmed by examining cell morphology using confocal laser scanning and transmission electron microscopy, which revealed characteristic nuclear condensation in LPS-treated endothelial cells. Apoptosis was blocked by a monoclonal antibody against CD14, suggesting that LPS triggers apoptosis via a soluble CD14 (sCD14) dependent mechanism. (C) 1998 Academic Press Limited.