Restoring NK Cell Cytotoxicity Post-Cryopreservation via Synthetic Cells.

Natural killer (NK) cells are critical components of the first-line immune defense, responsible for eliminating tumorigenic cells. NK cell-based adoptive immunotherapy has gained increasing attention; however, cryopreservation, a standard technique for NK cell storage, significantly impairs NK cell cytotoxicity, particularly in physiological 3D environments. Here, we demonstrate that short-term co-culture with effector T cells markedly enhances NK cell motility and killing functionality. Notably, a brief 1-day co-culture is sufficient to restore cryopreservation-impaired NK cell functionality in 3D environments. This enhancement requires direct contact between T cells and NK cells, which facilitates localized high concentrations of IL-2 at the cell contact sites. To develop a controled, donor-independent solution, we demonstrate that synthetic T cells with surface-bound IL-2 exhibit superior efficiency in revitalizing cryopreserved NK cells. These findings uncover a previously unrecognized role for physical contact-mediated local IL-2 signaling and provide an efficient, cost-effective, and tunable strategy to rescue NK cell functionality post-cryopreservation, paving the way for more scalable, potent, and clinically viable NK cell-based immunotherapies.