Figure 3.

Cytotoxic activity of reconstituted natural killer (NK) cells post SCT. (A) Cytotoxic activity against the cell line K562. Resting NK cells from patients showed good activity against K562 early post SCT (gray diamonds), which could be further enhanced by overnight stimulation with IL-2 (black rectangles). Cytotoxic activity against this target in the first 50 days post SCT was in the same range as in later time periods. (B) ADCC activity at early time points post SCT against cryopreserved leukemic blasts (at day +14) or a neuroblastoma cell line (between day +14 and +21). Cytotoxic activity was significantly enhanced against both targets using appropriate antibodies (P= 0.03 for leukemic blasts, P=0.01 for neuroblastoma). (C) Activity of patients’ cells post SCT against autologous blasts. Both resting (gray diamonds) and IL-2 activated cells (black rectangles) showed low but significant specific lysis. Exploiting ADCC with the CD19 antibody significantly enhanced specific lysis of both resting and activated NK cells (E:T=20:1, P=0.02 for resting and P=0.0004 for activated NK cells).