IL-2, IL-7, SCF, and stromal ligands generate NK cells from progeny of IL-3 and MIP-1α SNC cultures. CD34⁺/Lin⁻/DR⁻ cells were initially plated in SNC cultures for 14 days resulting in 47 ±7.3-fold cell expansion. These expanded cells (1 to 4 × 10⁵ from 2,000 to 4,000 initial CD34⁺/Lin⁻/DR⁻ cells) were plated in direct contact with stroma and the indicated cytokines for NK cell progenitor switch conditions. In a final step, conditions were changed again to those favoring NK cell differentiation. The combination of IL-2, IL-7, and SCF was best to induce NK cell progenitor commitment (n = 8) compared with no cytokines or other cytokines tested (n = 4).