Nkg2-C Is a Receptor on Human Natural Killer Cells That Recognizes Sturctures on K562 Target Cells

　　NKG2-C is a member of the recently discovered NKG2 family of genes and proteins, which are preferentially expressed on human natural killer (NK ) cells. These potential NK cell receptors belong to a larger class of type II transmembrane proteins with a C-type lectin domain. We show here that NKG2-C is expressed as a 36-kDa glycoprotein by translation in vitro, recombinant expression　and immunoprecipitiation from a human NK cell clone. Further, a recombinant soluble NKG2-C-receptor binds specifically to K562 cells, which are target cells for NK cell killing , and to RPMI 8866 cells, which are feeder cells for NK cells; several other hematopoietic　cell lines tested do not show any binding. The binding structures on the surface of K562 cells disappear, concomitant with a loss in susceptibility to killing when the cells are induced to differentiate with phorbol ester and Ca2+ ionophore. Our data suggest the presence of specific target molecules for NKG2-C on K562 cells, since overall glycosylation, Lewis X and Lewis Y structures, as well as the mucin- like CD43 molecule, do not change following induction of the cells. We propose that NKG2-C mediates a specific interaction of NK cells and their target cells with functional importance for NK cell killing