Effect of HLA-G1 and HLA-G2 expression on sensitivity to lysis of polyclonal NK cells. K562 transfected with either the vector alone, with HLA-G1, or with HLA-G2, were used as targets for NK cells (>90% CD3− CD16+ CD16+) isolated from donor 303 (HLA-A29, -B44, -B62, and -Cw3, -Cw5) at 1:1 effector/target (E/T) ratio, donor 395 (HLA-A2, -B13, -B44, and -Cw1) at 1:1 E/T ratio, and donor 481 (HLA-A3, -A26, -B27, -B35, and -Cw4, -Cw2) at 5:1 E/T ratio. The results are expressed as the percentage lysis recorded in a 4-h 51Cr-release assay. The standard deviation of the mean of the triplicates was below 5%, and the spontaneous release never exceeded 10% of the maximum release.