title: Ultrastructural and functional effects of lipopolysaccharide and interleukin-2 on human NK cells.
abstract: Bacterial endotoxin (lipopolysaccharide, LPS) and interleukin-2 (IL-2) are known to stimulate NK cell mediated cytotoxicity against tumor cells. In the present report we sought to correlate the stimulatory effect of LPS and IL-2 on NK cell activity with ultrastructural changes which occurred as a result of such stimulation. Peripheral blood mononuclear cells (PBMC) were purified from healthy donors by a Ficoll-Hypaque density gradient technique. Leu-11a+ NK cells were isolated by flow microfluorometry using a monoclonal FITC conjugated anti-Leu-11a antibody and a FACS II cell sorter. The PBMC were incubated, respectively, with E. coli LPS or recombinant IL-2 (IL-2) for various time periods. Sorted Leu-11a+ NK cells were incubated with LPS for 24 hours. The NK cytotoxicity in the PBMC and sorted Leu-11a+ cells was assessed by a 51Cr release technique using K562 tumor cells as targets. Leu-11a+ NK cells were identified by immunoelectron microscopy using anti-Leu-11a antibody and labeling with horseradish peroxidase or colloidal gold. Results showed that both LPS and IL-2 significantly enhanced the cytotoxic activity of PBMC. The cytotoxicity of sorted Leu-11a+ cells was augmented by LPS. Recombinant IL-2 induced a significant increase in the number of dense granules, hypertrophy of Golgi apparatus and rough endoplasmic reticulum, and mitosis of Leu-7+ cells and Leu-11a+ cells 4 or 7 days after stimulation. These data indicate that: (1) the effect of LPS on the enhancement of NK cytotoxicity in PBMC may be a direct and/or indirect process involving production of lymphokines; (2) LPS has a direct effect on sorted Leu-11a+ cells; (3) IL-2 stimulates mitosis of Leu-7+ cells and Leu-11a+ cells; and (4) the LPS or IL-2 induced ultrastructural changes in Leu-11a+ cells are consistent with the enhanced NK cytotoxicity.
authors.affiliation: Naval Medical Research Institute, Bethesda, Maryland 20814-5055.
authors.forename: Y H
authors.initials: YH
authors.lastname: Kang
authors.forename: M
authors.initials: M
authors.lastname: Carl
authors.forename: L P
authors.initials: LP
authors.lastname: Watson
mesh_terms: D002469:Cell Separation; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D007376:Interleukin-2 / Q000494:pharmacology*; D007694:Killer Cells, Natural / Q000276:immunology / Q000648:ultrastructure*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning
chemical_list: D007376:Interleukin-2; D008070:Lipopolysaccharides