MOLECULAR-CLONING OF NKB1 - A NATURAL-KILLER-CELL RECEPTOR FOR HLA-B ALLOTYPES

The expression of certain MHC class I allotypes by potential target ce lls can inhibit NK cell-mediated cytotoxicity. We recently identified the NKB1 surface Ag, expressed on T and NK cell subsets, as a putative inhibitory receptor for HLA-B class I molecules possessing the Bw4 se rologic epitope. NKB1 is a 70-kDa glycoprotein that after deglycosylat ion migrates as a 50-kDa protein as determined by SDS-PAGE. A cDNA enc oding the NKB1 receptor was cloned from a NKB1(+) T cell cDNA library by expression in COS-7 cells using the anti-NKB1 mAb DX9. NKB1 is a me mber of the Ig superfamily containing three Ig-like domains in the ext racellular region and is related to the recently identified family (p5 8/NKAT) of human NK and T cell surface molecules that appear to functi on as inhibitory receptors for HLA class I.