title: Cross-linking of MHC class I molecules on human NK cells inhibits NK cell function, segregates MHC I from the NK cell synapse, and induces intracellular phosphotyrosines.
abstract: Engagement of major histocompatibility complex (MHC) class I molecules on immune cells, where they are usually highly expressed, induces signal transduction events of unclear significance. We show here that antibody-mediated cross-linking of MHC-I molecules on human natural killer (NK) cells inhibits their cytotoxic activity against tumor target cells. Inhibition by anti-MHC class I monoclonal antibody exhibits molecular specificity and is an isotype and Fc-independent process. Physical hindrance of specific molecular recognition, induction of apoptosis, or reciprocal NK cell killing, which could be induced by cross-linking of MHC I molecules, has also been ruled out as putative mechanisms of inhibition. Confocal microscopy analysis revealed that MHC class I molecules on the surface of NK cells colocalize constitutively with GM1, a marker of lipid rafts. Cross-linking of MHC class I resulted in the asymmetric redistribution of GM1-enriched raft domains, which are concentrated to the immunological synapse, and MHC I molecules, which segregate to the opposite pole. Also, the cross-linking of MHC I on NK cells induced intracellular tyrosine phosphorylations. These results suggest that MHC I molecules on NK cells could transmit inhibitory signals upon engagement with putative ligands expressed on the surface of those cells that need to be protected from natural cytotoxicity.
authors.affiliation: Division of Immunology, Miguel Hernández University, San Juan de Alicante, Spain.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Rubio
authors.forename: Xavier
authors.initials: X
authors.lastname: Férez
authors.forename: María
authors.initials: M
authors.lastname: Sánchez-Campillo
authors.forename: Jesús
authors.initials: J
authors.lastname: Gálvez
authors.forename: Salvador
authors.initials: S
authors.lastname: Martí
authors.forename: Rocío
authors.initials: R
authors.lastname: Verdú
authors.forename: Trinidad
authors.initials: T
authors.lastname: Hernández-Caselles
authors.forename: Pilar
authors.initials: P
authors.lastname: García-Peñarrubia
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D002450:Cell Communication / Q000276:immunology; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003601:Cytotoxicity Tests, Immunologic; D005455:Fluorescent Antibody Technique; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D006801:Humans; D007694:Killer Cells, Natural / Q000502:physiology*; D021962:Membrane Microdomains / Q000276:immunology; D018613:Microscopy, Confocal; D019000:Phosphotyrosine / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D003432:Cross-Linking Reagents; D015395:Histocompatibility Antigens Class I; D019000:Phosphotyrosine