Inhibition of NK cell-mediated killing with pAb to NKG2D on NK cells. (A) A NK cell line (KHYG-1) expressed NKG2D, a receptor for ULBPs (shaded histogram). The cells were negative for CD16, which is needed for ADCC. Dotted lines show nonspecific background staining with isotype-matched control Ig. (B) Antibodies to NKG2D (100 μg/mL) inhibited the killing and virtually abolished the difference in the killing of GPI⁺ (□) and GPI^- (▪) K562 cells. Each value represents the mean (± SD) of triplicate assays (E/T ratio, 16:1). Control indicates isotype-matched control Ig. ^*P < .01; ^**P < .05.