Cytolytic activity of NK cells derived from patients with acute leukemia.

Cultured AML-NK cells at diagnosis were tested, in comparison with control NKs from a healthy donor, for cytotoxicity against P815 murine target (A,B). (A) The spontaneous NK-mediated cytotoxicity was evaluated at different effector-to-target ratios (10:1, stripped bars; 3:1, black bars; 1:1, white bars). (B) NK cells were analyzed in redirected killing experiments either in the absence (white bars) or in the presence of IgG1 mAb directed to anti-CD16 (black bars) or anti-NKp46 (stripped bars) mAbs, at an effector-to-target (E/T) ratio 3:1. (C) The same 4 representative AML-NK cells were assessed for cytolytic activity against autologous AML blasts either in the absence (white bars) or presence (black bars) of an anti-HLA class I mAb (of IgM isotype) at an E/T ratio of 10:1. The same effector and target cells were also tested in the presence of anti-NKp46 (striped bars) or anti-NKp44 (shaded bars) of IgG1 isotype in a redirected killing assay in which the mAb is substituting the natural ligands for the receptors. The normal control is represented by a polyclonal NK cell population derived from a healthy individual that has been assessed for cytotoxicity against autologous PHA blasts. These panels are representative of 3 different experiments, and similar results were obtained with NK cells from 8 additional AML patients.