title: Licensing of natural killer cells by self-major histocompatibility complex class I.
abstract: Natural killer (NK) cells have potent capacities to immediately kill cellular targets and produce cytokines that may potentially damage normal self-tissues unless they are kept in check. Such tolerance mechanisms are incompletely understood. Here we discuss recent studies suggesting that NK cells undergo a host major histocompatibility complex (MHC) class I-dependent functional maturation process, termed 'licensing'. Ironically, licensing directly involves inhibitory receptors that recognize target cell MHC class I molecules and block activation of NK cells in effector responses. This process results in two types of tolerant NK cells: functionally competent (licensed) NK cells, whose effector responses are inhibited by self-MHC class I molecules through the same receptors that conferred licensing, and functionally incompetent (unlicensed) NK cells.
authors.affiliation: Howard Hughes Medical Institute, Washington University School of Medicine, St Louis, MO 63110, USA. yokoyama@im.wustl.edu
authors.forename: Wayne M
authors.initials: WM
authors.lastname: Yokoyama
authors.forename: Sungjin
authors.initials: S
authors.lastname: Kim
mesh_terms: D000818:Animals; D001324:Autoantigens / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology*; D017634:Self Tolerance / Q000276:immunology*
chemical_list: D001324:Autoantigens; D015395:Histocompatibility Antigens Class I