Expression and serologic reactivity of LY-49G molecules

The Ly-49 multigene family in C57BL/6 mice encodes at least eight cell-surface glycoproteins with C-type lectin-like domains that are NK cell receptors for MHC class I molecules. Ly-49G1, Ly-49G2, and Ly-49G3 polypeptides appear to be derived from the same gene but differ by deleted regions in the extracellular domain, suggesting that alternative splicing may be a mechanism for NK cell receptor diversification. We tested whether Ly-49G1, -G2 and -G3 could be expressed as distinct cell-surface proteins on cells transfected with their respective cDNAs. Since the Ly-49G2 appears to be an allelic form of the B ALB/c-derived LGL-1 molecule that reacts with monoclonal antibody (mAb) 4D11, we also examined whether the mAb 4D11 epitope is expressed on the C57BL/6-derived Ly-49G polypeptides. Indeed, flow cytometric and immunoprecipitation analyses demonstrated that Ly-49Gl and -G2 were reactive with 4D11. In contrast, surface expression of Ly-49G3 was not detectable even by immunoprecipitation analysis with an anti-Ly-49 ammo-terminus polyclonal antiserum that reacts with Ly-49G1 and -G2. Nevertheless, these data indicate that Ly-49G1 and -G2 are both expressed as functional cell surface molecules, suggesting that each may have different specificities.