Involvement of different activating NK receptors in the lysis of AML. In these cytolytic assays, ⁵¹Cr-labeled AMLs were used as target cells and activated alloreactive polyclonal NK cell populations as effectors. AMLs were represented by ML1 (A), ML2 (B), ML14 (C), and ML19 (D). NK cells were preincubated with saturating amounts of mAb to the indicated receptors, washed, and then added to the cytolytic assay. The effector-to-target cell ratio used was 20:1. Data are expressed as percentage of lysis.