Ly49 gene expression in different inbred mouse strains

Mouse natural killer cells express receptors for class I MHC in the form of the Ly49 family of proteins. The Ly49 family contains at least 13 expresse d members (A, B, C, D, E, F, G, H, I, J, L, O, and P) and is further subdiv ided into activating and inhibitory subfamilies based on intracellular and transmembrane characteristics. The level of sequence identity between diffe rent members varies dramatically. However, comparison of the extracellular domain has revealed that several of the Ly49 molecules also form "pairs," w here one member is activating and the other is inhibitory. Until recently, most Ly49 molecules described have come from the C57B1/6 strain of inbred m ice. Using molecular cloning and immunochemical analysis we have found that different mouse strains express novel Ly49 molecules. Comparison of the al lelic forms of some Ly49 molecules has shown that the dividing line between different genes and different alleles is blurred.