title: Human monocyte mediated cytotoxicity to K-562 cells: a freeze-fracture-, scanning- and thin section electron microscopic study.
abstract: The structural features of "natural"human monocyte-mediated cytotoxicity towards K-562 leukemia cells in vitro have been examined. Human monocytes bound K-562 cells firmly and mediated a slow cytolysis of the leukemia cells. Monocyte binding of target cells was shown to be trypsin sensitive. Freeze-fracture and thin section electron microscopy revealed that effector and target cells were separated by a irregular space larger than 20 nm. There was no evidence for the involvement of specialized membrane junctions or organelle transfer between monocytes and target cells. Scanning electron microscopy revealed that K-562 cells bound to monocytes progressively lost their microvilli. This process started in the membrane areas close to the effector-target cell interaction. The results suggest that binding of target cells by monocytes followed by action of short-range soluble cytotoxic mediators may be the mechanism for the monocyte-mediated cytotoxicity towards K-562 cells.
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002450:Cell Communication; D002462:Cell Membrane / Q000648:ultrastructure; D003602:Cytotoxicity, Immunologic; D005614:Freeze Fracturing; D006801:Humans; D007942:Leukemia, Experimental / Q000276:immunology* / Q000648:ultrastructure; D008222:Lymphokines / Q000494:pharmacology; D008928:Mitochondria / Q000648:ultrastructure; D009000:Monocytes / Q000276:immunology* / Q000648:ultrastructure
chemical_list: D008222:Lymphokines