Natural killer cell activation and inhibition by receptors for MHC class I

Several recent advances have been made in our understanding of the mechanis ms which human natural killer cells recognize MHC class I molecules. Three are of special relevance: the identification of a novel molecule (DAP12) wi th a key role in the activation pathways; the observation that certain immu noglobulin-like receptors for HLA class I molecules are also utilized by ot her leucocyte lineages; and the definition of MHC class 1b proteins (i.e. H LA-E and Qa-1b) as specific ligands for the phylogenetically conserved CD94 -NKG2 lectin-like receptors.