In the absence of sufficient signaling by their HLA class I-specific inhibitory receptors, @entity1 natural killer (NK) cells become activated and display potent @entity137 against cells that are either HLA class I negative or deficient. This indicates that the NK receptors responsible for the induction of @entity137 recognize ligands on target cells different from HLA class I molecules. On this basis, the process of NK-cell triggering can be considered as a mainly non-MHC-restricted mechanism. The recent identification of a group of NK-specific triggering surface molecules has allowed a first series of pioneering studies on the functional/molecular characteristics of such receptors. The first three members of a receptor family that has been termed natural @entity137 receptors (NCR) are represented by @entity3222 , @entity19124 and @entity3221 . These receptors are strictly confined to NK cells, and their engagement induces a strong activation of NK-mediated cytolysis. A direct correlation exists between the surface density of NCR and the ability of NK cells to kill various target cells. Importantly, mAb-mediated blocking of these receptors has been shown to suppress @entity137 against most NK-susceptible target cells. However, the process of NK-cell triggering during target cell lysis may also depend on the concerted action of NCR and other triggering receptors, such as @entity3223 , or surface molecules, including @entity36010 and @entity58819 , that appear to function as co-receptors rather than as true receptors. Notably, a dysfunction of @entity36010 has been associated with a severe form of @entity465 termed @entity1071 . Future studies will clarify whether also the altered expression and/or function of other NK-triggering molecules may represent a possible cause of @entity1200 .

XXXX natural killer cell receptors and co-receptors.

@entity1 :: ('9606', 'Species') :: ['human'] @entity137 :: ('MESH:D064420', 'Disease') :: ['cytotoxicity'] @entity3223 :: ('22914', 'Gene') :: ['NKG2D'] @entity1071 :: ('MESH:D008232', 'Disease') :: ['X-linked lymphoproliferative disease'] @entity3222 :: ('9437', 'Gene') :: ['NKp46'] @entity36010 :: ('51744', 'Gene') :: ['2B4'] @entity58819 :: ('51348', 'Gene') :: ['NKp80'] @entity465 :: ('MESH:D007153', 'Disease') :: ['immunodeficiency'] @entity1200 :: ('MESH:D007154', 'Disease') :: ['immunological disorders'] @entity3221 :: ('259197', 'Gene') :: ['NKp30'] @entity19124 :: ('9436', 'Gene') :: ['NKp44']
@entity1 :: (9606,Species) :: ['Human']
