NKG2‐C is a receptor on human natural killer cells that recognizes structures on K562 target cells

Abstract

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 immunoprecipitation 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.