Human natural killer cell activating receptors

Natural killer (NK) cells were poorly characterized until 10 years ago and few molecules expressed on their cell surface were known. Now the situation has changed dramatically, since a plethora of receptors characterized by o pposite functions have been functionally and molecularly defined. NK cells express clonally distributed inhibitory receptors specific for different gr oups of HLA class I alleles, thus protecting normal cells from NK-mediated lysis. On the contrary various activating receptors are involved in trigger ing of NK-mediated natural cytotoxicity, Their engagement induces human NK cells to kill target cells that are either HLA class I-negative or -deficie nt. Here a brief description of the activating receptors and coreceptor and of their ligand(s) is given. (C) 2001 Elsevier Science Ltd. All rights res erved.