Effect of HLA-G1 and HLA-G2 expression on sensitivity to NK lysis of PBMC. K562 transfected with either the vector alone, with HLA-G1, or with HLA-G2 were used as targets. Freshly isolated PBMC from (A) donor 4010 (HLA-A3, -B44, -B56, and -Cw1), (B) donor 845 (HLA-A1, -A28, -B8, -B51, and -Cw7), and (C) donor 813 (HLA-A2, -B27, -B51, and -Cw1) were used as effectors. 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.