Natural Killer Cells (NK Cells)
What are Natural Killer (NK) Cells
Natural Killer cells, or NK cells, are specialized immune cells that help protect the body by identifying and destroying abnormal cells.
They form part of our natural immune defense and are particularly important for recognizing:
- Cancer cells
- Virus-infected cells
- Damaged and stressed cells
- Certain senescent (aged) cells
At StemCells21, our NK cell therapy is autologous, meaning the cells originate from the patient’s own blood.
A blood sample is collected, immune cells are isolated, and the NK-cell population is activated and expanded in our laboratory. Following quality testing, the activated cells are administered back to the same patient.
How Does NK Cell Therapy Work:
Natural Killer Cells continuously patrol the body as part of the immune system’s natural surveillance network, looking for cells that show signs of infection, damage, abnormal growth or cellular stress.
Healthy cells normally display molecular signals that tell NK cells they belong to the body and should not be attacked. Cancerous, virus-infected, stressed or senescent cells can lose some of these normal protective signals or develop abnormal stress signals on their surface. NK cells use a combination of activating and inhibitory receptors to detect these changes and determine whether a cell may represent a potential threat.
When an NK cell identifies a susceptible abnormal cell, it can attach directly to the target and form a close connection through which it delivers its cytotoxic molecules.
The NK cell then releases perforin and granzymes. Perforin helps these cytotoxic proteins enter the target cell, while granzymes activate internal pathways that trigger apoptosis — a controlled form of programmed cell death.
NK cells can also use additional mechanisms to eliminate susceptible abnormal cells, including death-receptor pathways and antibody-dependent cellular cytotoxicity (ADCC), where NK cells recognize antibody-coated target cells.
Importantly, the NK cell itself does not necessarily die after destroying its target. It can detach and continue its immune-surveillance activity, potentially recognizing and attacking additional susceptible abnormal cells.
This combination of rapid recognition, targeted cytotoxicity and continued immune surveillance is what makes NK cells particularly interesting in the fields of cancer immunotherapy, immune support and senescent-cell research.
Potential Benefits of NK Cell Therapy
Cancer Immune Surveillance
Direct Cancer Cell Killing
Supporting the Immune System
Antibody-Dependent Cancer Killing
NK Cells, Senescent Cells & Healthy Aging
NK cells may also play an important role in healthy aging and longevity.
As we age, damaged cells can sometimes stop dividing but remain within our tissues. These are called senescent cells.
When senescent cells accumulate, they can release inflammatory substances known collectively as SASP — the Senescence-Associated Secretory Phenotype.
Increasing senescent-cell burden has been associated with chronic inflammation and age-related tissue dysfunction.
Importantly, NK cells are one of the body’s natural mechanisms for identifying and removing certain senescent cells.
Because NK-cell function can also change as we age, researchers are investigating whether improving NK-cell activity could support senescent-cell surveillance, immune function and healthier aging.
This emerging field is sometimes described as NK cell-based senotherapy.
SC21 NK Cell Quality Control
Producing large numbers of NK cells is only part of the process.
We also want to understand whether the resulting cells are viable, appropriately characterized and functionally active.
Testing can include:
- Cell count and expansion
- Cell viability
- NK-cell phenotype
- CD56 / CD3 analysis
- Sterility and microbiological testing
- Functional cytotoxicity testing
Cytotoxicity testing evaluates how effectively the expanded immune cells can destroy susceptible target cells under controlled laboratory conditions.
See SC21 NK Cells in Action
At Our Laboratories, we can directly observe the interaction between our expanded NK cells and cancer cells during laboratory cytotoxicity testing.
The videos below demonstrate the real-time functional activity of SC21 expanded NK cells against two different cancer cell models.
Video 1 — NK Cells vs HeLa Cervical Cancer Spheroid
This laboratory video shows our expanded NK cells interacting with a 3D HeLa cervical cancer spheroid.
Unlike a simple single layer of cancer cells, a 3D spheroid creates a more complex tumor-like environment. The video allows us to observe NK cells interacting with the spheroid and the resulting cancer-cell damage and death.
Our HeLa laboratory cytotoxicity testing has demonstrated strong NK-cell activity across different NK cell-to-target cell ratios, providing functional evidence that the expanded cells retain their ability to recognize and destroy susceptible cancer cells.
Video 2 — NK Cells vs K562 Leukemia Cells
The second laboratory video demonstrates SC21 expanded NK cells interacting with K562 leukemia cells, a widely used target-cell model for evaluating NK-cell cytotoxic function.
The video shows NK cells engaging the target cells and inducing cancer-cell death under controlled laboratory conditions.
K562 cells are particularly useful for evaluating NK-cell function because of their susceptibility to NK-cell-mediated cytotoxicity, allowing our laboratory team to assess whether the expanded NK-cell population remains functionally active following culture and expansion.
SC21 Autologous NK Cell Therapy
Our NK cell program begins with the patient’s own peripheral blood. Blood is collected and processed to isolate peripheral blood mononuclear cells (PBMCs), which contain the patient’s naturally occurring NK cells. These immune cells are then placed into carefully controlled laboratory culture conditions where the NK-cell population is activated and expanded, substantially increasing the number of available functional immune cells.
Following expansion, the cellular preparation undergoes comprehensive quality control and functional assessment, including evaluation of cell number, viability, cellular phenotype, sterility and cytotoxic activity. Once the required quality criteria have been met, the activated and expanded autologous NK-cell preparation is administered back to the same patient according to their individualized medical protocol.
This autologous process allows us to begin with the patient’s own immune cells, activate and expand them under controlled laboratory conditions, verify their quality and functional activity, and return them to the patient as part of a personalized cellular immunotherapy program.
Who May Consider NK Cell Therapy?
NK-cell therapy is being researched across several areas of medicine, particularly:
Cancer & Oncology
Supporting natural anti-tumor immune surveillance and cellular immunotherapy strategies.
Immune Support
Supporting innate immune surveillance against abnormal and virus-infected cells.
Healthy Aging & Longevity
Investigating NK-cell activity in relation to immunosenescence, senescent-cell clearance and healthy aging.
Every patient is different. Our medical team reviews your medical history, diagnosis, current treatments, laboratory results and overall health before determining whether an NK-cell program may be appropriate.