Ly-49A is an MHC class I-specific inhibitory receptor on mouse NK cells. Previously reported Southern blot analysis revealed five restriction fragment length polymorphic (RFLP) variants among inbred mouse strains suggesting the existence of allelic forms of Ly-49A. To address this possibility, we performed flow cytometric analysis on IL-2 activated NK cells from BALB/c, C57BL/6, C57L, NZW, and SWR strains, each representing a different RFLP group. There were differential reactivities between strains to monoclonal antibodies known to bind the C57BL/6 form of Ly-49A, consistent with Ly-49A alleles. To characterize these allelic variants further, mRNA was isolated from IL-2 activated NK cells from each strain and RT-PCR was performed using Ly-49A specific primers. Sequences were confirmed on multiple, independent PCR products. Analysis of deduced polypeptide sequences revealed that all variants demonstrate the same total and domain size. The overall amino acid identity between allelic variants was 93%-99%, suggesting that these represent allelic forms of Ly-49A rather than other Ly-49 family members that display < 85% amino acid identity to Ly-49A. Strikingly, several amino acid differences were observed in the extracellular domains while the intracellular domains were conserved. These results suggest that the alleles have similar functions but may have different specificities for MHC class I perhaps increasing the repertoire of NK cell receptors.
|State||Published - Dec 1 1996|