Killing of AML blasts by normal allogeneic NK cells.

(A) The lysis of AML blasts by normal allogeneic NCR^brightNK cells was evaluated either in the absence (black bars) or in the presence of anti-HLA class I mAb of IgM isotype (white bars) or of anti-CD16 mAb of IgG1 isotype (striped bars). The latter was used to induce redirected killing against AML blasts that are FcγR⁺. (B) The cytolytic activity mediated by a normal allogeneic NK cell population was evaluated in the presence of anti-NCR mAbs (of IgM isotype) as indicated. In blocking experiments the anti-NCR mAbs used were in all instances of IgM isotype to avoid redirected killing effects because of the presence of FcγR on leukemia target cells. These experiments were performed at an E/T ratio of 10:1.