Breaking the Cryopreservation Bottleneck: New Pretreatment Technique Boosts NK Cell Recovery Rate to 90%–100% After Thawing
Release time:
2026-04-29
In the field of cell immunotherapy, NK cells are key members of the innate immune system. Due to their lack of graft-versus-host disease (GVHD) risk and low cytokine storm risk, they are considered ideal candidates for "off-the-shelf" cancer immunotherapy. However, the sharp decline in cell viability and function caused by cryopreservation damage has long been a critical bottleneck limiting their clinical translation.
Recently, a landmark study from the University of Pennsylvania team was published in the top international journal Nature Communications, revealing for the first time the core mechanism behind the massive death of NK cells after cryopreservation. By using a pretreatment protocol combining IL-15 and IL-18, the researchers successfully increased the 24‑hour post‑thaw survival rate from approximately 25% to 90%–100%, removing a key obstacle to the commercialization of NK cell therapies.
Mechanism Revealed: Granzyme B Leakage Triggers "Autolysis"
The study found that using traditional cryopreservation protocols optimized for T cells, about 75% of NK cells die within 24 hours after thawing. Using CRISPR‑Cas9 gene editing and confocal microscopy, the team unraveled the mystery: NK cell death is not caused by acute necrosis from ice crystals or by fratricide, but by "autolysis."
Specifically, cryopreservation damage disrupts the pre‑formed cytotoxic vesicles inside NK cells, leading to the leakage of potent granzyme B (GZMB). This leakage activates intracellular apoptotic pathways, triggering the cells' "suicide" behavior. Elucidating this mechanism provides a clear target for precise intervention.
Dual Protection: The Synergistic Effect of IL‑15 and IL‑18
Targeting this mechanism, the research team screened various cytokine combinations and ultimately found that pretreatment with IL‑15 and IL‑18 for 24 hours before cryopreservation is remarkably effective. This protective effect stems from two pathways: first, it rapidly induces NK cell degranulation, temporarily reducing intracellular granzyme B levels and thus reducing the risk of leakage at the source; second, it significantly upregulates the expression of the anti‑apoptotic gene BCL2L1 (Bcl‑XL), building an apoptosis‑resistant defense at the genetic level.
Function Preserved: In Vivo and In Vitro Efficacy Comparable to Fresh Cells
Experimental validation showed that pretreated cryopreserved NK cells achieved 24‑hour post‑thaw survival rates of 90%–100%. More importantly, their killing activity against lymphoma cells and antibody‑dependent cell‑mediated cytotoxicity (ADCC) were completely equivalent to those of fresh cells. In a mouse model of disseminated lymphoma xenograft, the cryopreserved cell group showed no significant differences in tumor control, in vivo expansion capacity, or mouse survival compared to the non‑cryopreserved group, achieving an industry breakthrough in which cryopreserved cells match the efficacy of fresh cells.
Clinical Translation: A Low‑Cost, High‑Efficiency Universal Solution
The clinical value of this approach lies in its extremely simple operation. It requires no specialized cryopreservation solutions or complex equipment, using only GMP‑grade compliant cytokines that can be removed by routine washing after pretreatment, posing no additional safety risks to patients and enabling rapid integration into existing cell production and cryopreservation workflows. As the large‑scale manufacturing of NK cells derived from umbilical cord blood and iPSCs becomes increasingly mature, combining this cryopreservation technology holds the potential to significantly reduce cell therapy costs and improve accessibility, opening new avenues for immunotherapy in hematological malignancies and solid tumors.
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