Notch Activation Induces the Generation of Functional NK Cells from Human Cord Blood CD34-Positive Cells Devoid of IL-15

Abstract

The development of NK cells from hematopoietic stem cells is thought to be dependent on IL-15. In this study, we demonstrate that stimulation of human cord blood CD34 ؉ cells by a Notch ligand, Delta4, along with IL-7, stem cell factor, and Fms-like tyrosine kinase 3 ligand, but no IL-15, in a stroma-free culture induced the generation of cells with characteristics of functional NK cells, including CD56 and CD161 Ag expression, IFN-␥ secretion, and cytotoxic activity against K562 and Jurkat cells. Addition of ␥-secretase inhibitor and anti-human Notch1 Ab to the culture medium almost completely blocked NK cell emergence. Addition of anti-human IL-15-neutralizing Ab did not affect NK cell development in these culture conditions. The presence of IL-15, however, augmented cytotoxicity and was required for a more mature NK cell phenotype. CD56 ؉ cells generated by culture with IL-15, but without Notch stimulation, were negative for CD7 and cytoplasmic CD3, whereas CD56 ؉ cells generated by culture with both Delta4 and IL-15 were CD7 ؉ and cytoplasmic CD3 ؉ from the beginning and therefore more similar to in vivo human NK cell progenitors. Together, these results suggest that Notch signaling is important for the physiologic development of NK cells at differentiation stages beyond those previously postulated.

Inducible Fli-1 gene deletion in adult mice modifies several myeloid lineage commitment decisions and accelerates proliferation arrest and terminal erythrocytic differentiation

“…8 Furthermore, activation of Notch signaling in HSCs has also been reported to stimulate the direct production of NK cells. 42 In that context, it is worth noting that our present study confirmed that Fli-1 loss also induced a significant increase in NK cells as already observed by others in chimeric Fli-1 Ϫ/Ϫ mice. 25 An exciting possibility suggested by our study, that could simultaneously explain both the increase in MEPs and NK cells induced by Fli-1 loss, would be therefore that Fli-1, as already reported for Ikaros, 43 might be a negative regulator of Notch signaling in HSCs.…”

Fate Decision Between Group 3 Innate Lymphoid and Conventional NK Cell Lineages by Notch Signaling in Human Circulating Hematopoietic Progenitors

“…In contrast to the suppressive function of Notch in IL-15-induced cNK cell differentiation from HPC-3 cells, Notch signaling augmented IL-7-induced cNK cell differentiation from HPC-1 cells, because a substantial proportion of the cNK cell population is generated from CD34 + Lin 2 CD7 + cells, which are induced from HPC-1 cells by Notch signaling. Similarly, Notch signaling was reported to induce cNK cell differentiation from human HPCs in culture (24,26,30,45) (47). It is known that Notch signaling is essential for T cell commitment in ETPs (32,48).…”

“…Recent studies have shown that Notch signaling is required for differentiation of NCR + ILC3 from NCR 2 ILC3 and for maintenance of the NCR + ILC3 population (22,23). In humans, Notch signals enhance cNK cell differentiation from HPCs in culture (24)(25)(26)(27). However, although only one report noted that ILC2 lineage cells can be induced from postnatal thymic CD34 + CD1a 2 cells by Notch signals using OP9-DL1 cells (28), the significance of Notch signaling in the commitment of human ILCs is largely unknown.…”

Notch signaling in the hematopoietic system

“…Several reports suggest that Notch signaling can promote development of certain NK subsets as well as their function. NK cells expressing certain T lineage markers such as CD7 + and cyCD3ε + could be generated from UCB cells in the presence of OP9 stromal cells expressing Dll1 [125] or Dll4 [126]. These human-like NK cells acquired cytolytic activity and produced granzyme B [125].…”