KLRG1 belongs to the killer cell lectin-like receptor (KLR) family, which is a group of transmembrane proteins preferentially expressed in NK cells. Natural killer (NK) cells are lymphocytes that can mediate lysis of certain tumor cells and virus-infected cells without previous activation. They can also regulate specific humoral and cell-mediated immunity. Cell surface expression of KLRG1 is up-regulated by expression of MHC class I molecules. Recombinant human KLRG1 protein, fused to His-tag at N-terminus, was expressed in E.coli.