HLA-E chimeric molecules for providing nonhuman mammalian cells resistant to cytotoxic human NK cells, nucleotide sequences encoding these chimeric molecules, and nonhuman mammalian cells and nonhuman mammals transformed with such nucleotide sequences are disclosed herein. The HLA-E chimeric molecules of the invention contain a peptide that reforms all or part of the signal peptide region, α1 domain and/or α2 domain of HLA-E, and a nucleotide sequence of the invention encodes a HLA-E chimeric molecule. A transformant incorporating a nucleotide sequence of the invention expresses HLA-E efficiently.