title: Interaction of monocytes with NK cells upon Toll-like receptor-induced expression of the NKG2D ligand MICA.
abstract: Reciprocal interactions between NK cells and dendritic cells have been shown to influence activation of NK cells, maturation, or lysis of dendritic cells and subsequent adaptive immune responses. However, little is known about the crosstalk between monocytes and NK cells and the receptors involved in this interaction. We report in this study that human monocytes, upon TLR triggering, up-regulate MHC class I-Related Chain (MIC) A, but not other ligands for the activating immunoreceptor NKG2D like MICB or UL-16 binding proteins 1-3. MICA expression was associated with CD80, MHC class I and MHC class II up-regulation, secretion of proinflammatory cytokines, and apoptosis inhibition, but was not accompanied by release of MIC molecules in soluble form. TLR-induced MICA on the monocyte cell surface was detected by autologous NK cells as revealed by NKG2D down-regulation. Although MICA expression did not render monocytes susceptible for NK cell cytotoxicity, LPS-treated monocytes stimulated IFN-gamma production of activated NK cells which was substantially dependent on MICA-NKG2D interaction. No enhanced NK cell proliferation or cytotoxicity against third-party target cells was observed after stimulation of NK cells with LPS-activated monocytes. Our data indicate that MICA-NKG2D interaction constitutes a mechanism by which monocytes and NK cells as an early source of IFN-gamma may communicate directly during an innate immune response to infections in humans.
authors.affiliation: Department of Hematology, Eberhard Karls University of Tuebingen, Germany.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Kloss
authors.forename: Patrice
authors.initials: P
authors.lastname: Decker
authors.forename: Katrin M
authors.initials: KM
authors.lastname: Baltz
authors.forename: Tina
authors.initials: T
authors.lastname: Baessler
authors.forename: Gundram
authors.initials: G
authors.lastname: Jung
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Rammensee
authors.forename: Alexander
authors.initials: A
authors.lastname: Steinle
authors.forename: Matthias
authors.initials: M
authors.lastname: Krusch
authors.forename: Helmut R
authors.initials: HR
authors.lastname: Salih
mesh_terms: D018122:B7-1 Antigen / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015395:Histocompatibility Antigens Class I / Q000276:immunology* / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008024:Ligands; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000276:immunology*; D020239:Receptor Cross-Talk / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051193:Toll-Like Receptors / Q000276:immunology* / Q000378:metabolism
chemical_list: D018122:B7-1 Antigen; D016207:Cytokines; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; C527085:KLRK1 protein, human; D008024:Ligands; C099187:MHC class I-related chain A; D055655:NK Cell Lectin-Like Receptor Subfamily K; D051193:Toll-Like Receptors; D007371:Interferon-gamma