Ultrastructural and Immunocytochemical Study of the Uptake and Distribution ofBacterial Lipopolysaccharide in Human Monocytes

摘要

Interaction of bacterial lipopolysaccharide (LPS) with monocytes stimulatesproduction of a variety of mediators that are involved in the pathogenesis of septic shock and wound repair. The mechanisms of LPS uptake and intracellular distribution of LPS in human monocytes is reported here. Ficoll-Hypaque-purified peripheral mononuclear cells (PBMC) were exposed to LPS from rough Escherichia coli (J5) or to biotin-conjugated LPS of E. coli (055:B5) at 37 C for various times and processed for electron microscopy, immunocytochemistry, and flow cytometry. Monocytes were identified by the presence of numerous cytoplasmic peroxidase-positive granules or by monoclonal antibodies against monocyte. LPS micelles were identified by their specific bilayer structure, staining of horseradish peroxidase reaction product, or collodial gold using biotin-LPS or a monoclonal antibody to LPS. Binding of LPS to cell surface was observed 5 min after incubation with LPS. Intracellular localization of LPS micelles was found 30 min following exposure to LPS. Prolonged incubation with LPS increased intracellular LPS. Intracellularly, LPS micelles were found in large membrane-bound vacuoles, in small vesicles, and in the cytoplasm and nucleus. (TTL)