The Notch Ligands Jagged2, Delta1, and Delta4 Induce Differentiation and Expansion of Functional Human NK Cells from CD34⁺ Cord Blood Hematopoietic Progenitor Cells

Notch receptor signaling is required for T cell development, but its role in natural killer (NK) cell development is poorly understood. We compared the ability of the 5 mammalian Notch ligands (Jagged1, Jagged2, Delta1, Delta3, or Delta4) to induce NK cell development from human hematopoietic progenitor cells (HPCs). CD34⁺ HPCs were cultured with OP9 stromal cell lines transduced with 1 of the Notch ligands or with OP9 stromal cells alone, in the presence of IL-7, Flt3L, and IL-15. Differentiation and expansion of CD56⁺CD3^- cells were greatly accelerated in the presence of Jagged2, Delta-1, or Delta-4, versus culture in the absence of ligand or in the presence of Jagged1 or Delta3. At 4 weeks, cultures containing Jagged2, Delta1, or Delta4 contained 80% to 90% NK cells, with the remaining cells being CD33⁺ myelogenous cells. Notch-induced NK (N-NK) cells resembled CD56^bright NK cells in that they were CD16^-, CD94^-, CD117⁺, and killer immunoglobulin-like receptors (KIR^-). They also expressed NKp30, NKp44, NKp46, 2B4, and DNAM-1, with partial expression of NKG2D. The N-NK cells displayed cytotoxic activity against the K562 and RPMI-8226 cell lines, at levels similar to activated peripheral blood (PB) NK cells, although killing of Daudi cells was not present. N-NK cells were also capable of interferon (IFN)-γ secretion. Thus, Notch ligands have differential ability to induce and expand immature, but functional, NK cells from CD34⁺ HPCs. The use of Notch ligands to generate functional NK cells in vitro may be significant for cellular therapy purposes.