Effect of FL in combination with various cytokines on the generation of CD56⁺CD3⁻ NK cells from CD34⁺ HPCs. Purified CD34⁺ HPCs were plated in complete RPMI-1640 medium in the presence of the indicated cytokines at the concentrations described in Materials and Methods. Results represent the mean ± SEM of total MNC number and absolute CD56⁺ NK cell number of five separate experiments. *P ≤ .01 and **P ≤ .005 compared with cultures with FL plus IL-15.