TYPE-I TRANSMEMBRANE RECEPTOR WITH INHIBITORY FUNCTION IN MOUSE MAST-CELLS AND NK CELLS

The MHC class I-specific inhibitory receptors on human and mouse NK ce lls have surprisingly different structures. The mouse receptors (Ly-49 ) are type II transmembrane glycoproteins of the C-type lectin family, whereas the human receptors (killer cell inhibitory receptors (KIR)) belong to the Ig superfamily. This difference prompted a search for Ig -like inhibitory receptors in mice. Here we show that gp49, a mouse ma st cell protein of unknown function but with sequence similarity to KI R, is expressed in NK cells. The gp49 cytoplasmic tail, containing a s equence related to an inhibitory motif shared by KIR and Ly-49, delive red a strong inhibitory signal in both human and mouse NK cells when s ubstituted for a KIR cytoplasmic tail. These data show that Ig-like re ceptors with inhibitory properties exist in both species and that mous e mast and NK cells may recognize common inhibitory ligands.