Natural killer (NK) cells are innate lymphoid cells (ILCs) that play key roles in immunosurveillance and immunoregulation. They constitute a heterogeneous population comprising three principal subpopulations: NK1 (cytotoxic), NK2 (regulatory), and NK3 (adaptive). In response to interleukin-2 (IL-2) stimulation, NK3 cells differentiate into adherent NK (A-NK) cells, which exhibit potent anti-tumor activity. Human A-NK cells are generated by priming and adherence-based selection of peripheral blood NK3 cells in nanomolar (nM) IL-2 concentrations, followed by prolonged restimulation and culture in the same IL-2 conditions. However, these A-NK cells are terminally differentiated, unresponsive to IL-2, prone to apoptosis, and are ineffective in cancer therapy. Here, we report previously unrecognized physiological properties of A-NK cells and describe a novel strategy for their in vitro generation. Specifically, we demonstrate that A-NK cells primed with nM IL-2 concentrations de novo express the high-affinity IL-2 receptor (IL-2Rαβγ). Upon subsequent transfer to picomolar (pM) IL-2 concentrations, these cells undergo sustained vigorous proliferation and retain robust anti-tumor activity in long-term cultures. These findings underscore the functional plasticity of NK3 cells, demonstrating that nM IL-2 priming can reprogram them to function efficiently in pM IL-2 as highly effective anti-tumor effectors. This cytokine-mediated reprogramming of NK3 cells provides a physiologically relevant strategy for generating fully functional therapeutic NK cells with reduced IL-2 dependency. This approach offers a promising venue for advancing NK cell-based cancer immunotherapies.

IL-2, IL-2 receptors, Activated NK cells, Adherent NK cells, Proliferation, Cytotoxicity