NK Cell Function What Is it & Why is it So Important?

By Dr. Jeannie Thomason

 improving biological terrain in dogs


When the immune system is operating at peak efficiency, it should be able to seek and destroy any undesirable cell anywhere in the body. You see, It simply does not matter to the immune system where that undesirable cell or foreign organism is or what it is called; if it is not supposed to be there, it will attack and destroy it. They serve to contain viral infections while the adaptive immune response is generating antigen-specific cytotoxic T cells that can clear the infection.

Natural killer cells (also known as NK cells, K cells, and killer cells) are a type of lymphocyte (a white blood cell) and a component of innate immune system. NK cells, like cytotoxic T cells, contain granules filled with potent chemicals. They are called “natural” killers because they, unlike cytotoxic T cells, do not need to recognize a specific antigen before swinging into action. They target tumor cells and protect against a wide variety of infectious microbes. In several immunodeficiency diseases, in our pets (and in humans) or in case of cancer, natural killer cell function becomes abnormal. Natural Killer Cells may also contribute to immunoregulation by secreting high levels of infuential lymphokines

Both cytotoxic T Cells and Natural Killer Cells kill on contact. The killer binds to its target, aims its weapons and then delivers a lethal burst of chemicals that produces holes in the target cell’s membrane. Fluids seep in and leak out, and the cell bursts.

NK cell also play a role in adaptive immune response. Numerous experiments have worked to demonstrate their ability to readily adjust to the immediate environment and formulate antigen-specific immunological memory, fundamental for responding to secondary infections with the same antigen. The ability for NK cells to act in both the innate and adaptive immune response is becoming increasingly important in research utilizing NK cell activity and potential cancer therapies.

The main function of these cells is to kill damaged or infected cells. NK cells target any cell that is missing the “self” marker that identifies it as one of our own. Foreign cells and mutated cells like cancer cells are without these “self” markers. The NK cells attach and destroy these cells and spare normal cells that have high levels of “self” markers. The killing process begins when the NK cell binds to the target cell and releases it’s lethal burst of chemicals that produce holes in the target cell membrane. Fluids and salts seep in and the target cell eventually bursts.

Cells are continually being produced as a normal process of life. Occasionally a mutated cell is produced. Under normal, healthy conditions this mutated cell is destroyed by your immune system before any harm is done. However, if your immune system is not operating at peak efficiency, then these types of cells get by. If left unchecked they can multiply until a problem such as cancer arises.


December 8, 1999


A molecular lock and key complex of so-called natural killer cells in the blood stream has been found for the first time, scientists at the University of Maryland Biotechnology Institute (UMBI) report in today’s issue of the journal Nature.

Natural Killer (NK) cells are a critical, first line of defense against cancer tumor cells and cells infected with the AIDS virus and other harmful microbes. They have molecules on their cell surfaces called NK receptors that find and destroy diseased cells.

The scientists have captured the first real look a the subtle workings of NK cells, says co-author Roy A. Mariuzza, professor and molecular biologist at UMBI’s Center for Advanced Research in Biotechnology (CARB) in Rockville, Md. “This tells us for the first time how NK cells recognize the difference between normal and abnormal, infected cells.” He says the molecular machinery of NK cells is not as well understood as that of T or B while blood cells for fighting infections, but is also essential for maintaining health. “Lucky for us, there are NK cells”, says Mariuzza. Some viruses such as HIV, the cause of AIDS, have evolved camouflaging tricks and can’t be destroyed by T cells.” The NK cells find and destroy unprotected cells that are infected, those that no longer have markers called MHC molecules on their surface to say they are healthy,” he says. The NK cells patrol the bloodstream in all directions like molecular police cruisers, says Mariuzza, using their NK receptors to signal out abnormal cells without proper MHC identification. The NK cell punches the abnormal cell with toxic granules and kills it. At CARB, Mariuzza and collaborators discovered how an NK receptor molecule locks onto MNC molecules, which are on the surfaces of practically all normal cells. Once locked on, the NK cell “knows” the blood cell with the MHC marker is all right. It unlocks, then goes “cruising” off to check out other cells.

The laboratory breakthrough occurred when the researchers made a pure crystal of the molecular complex, or the checkup point, of an NK receptor and an MHC marker molecule. They then applied a powerful beam of X-rays to the crystal to compute the positions of the atoms making up the molecular lock-and-key structure. The result was the first 3-dimensional molecular structure known for the interaction of the NK receptor and an MHC marker.

“By identifying the molecular structure, the researchers have validated the missing self hypothesis that NK cells will attach only virus-infected or tumor cells that have lost their healthy self identity” says Jennie Hunter-Cevera, UMBI president.

Mariuzza adds, “Our results give us a basis for expanding research on NK cell receptors and MHC. We have actually found two distinct (molecular) binding sites. One was unexpected. Now we need to compare this to still unknown structures of other NK receptors to find out how each of them works.”

Scientists estimate that NK cells make up five to 16 percent of the total number of white blood cells that the body uses to fight infections. Those with defective or absent NK cell activity can contract a wide spectrum of diseases, particularly cancers. In fact, results from a number of clinical trials indicate that NK cells can be used to control tumor metastates. The therapeutic uses of NK cell activity will likely increase as their relationships to healthy and diseased cells becomes better known.


Immunotherapy promises to be an important therapy when addressing autoimmune disease and cancer. Even when treated conventionally with radiation and chemotherapy, immunotherapy appears to be a good adjunct. By using the phenomenal recognition ability of the immune system, it gives a better way to target and treat dis-ease. If used in conjunction with the traditional methods, it offers a way to get the immune system involved.

Natural Immunotherapy Products:

Active Hexose Correlated Compound (AHCC)

An AHCC product specifically formulated for dogs

Active Hexose Correlated Compound (AHCC) is neither a drug nor a medicine. It is a food substance – a dietary supplement rich in polysaccharides processed from the mycelia of selected mushrooms (basidiocymetes) into a rich nutritive extract. Published research has shown that, in most patients, it can be effective in stimulating and enhancing macrophage immune cells and NK-Cells.


Humic/Fulvic Acid

Humic/Fulvic acid is composed of sugars that act as catalysts, encouraging the body to produce glycoproteins that bind to the two chief lymphocytes that perform immune functions – the Natural Killer Cells (NK) and T-Cells. This binding causes these immune system cells to remain balanced by establishing a communication pathway among them. This function of humic acid enables the immune system to identify the body’s own dead cells from infected cells which is very important in cases of serious injuries from burns and radiation as well as drugs and vaccines which can cause an inability to differentiate between dead and infected cells causing the immune system to attack the body’s own dead cells.  (Optimally Organic)



(medicinal mushrooms) The mushrooms in Myco Formulas work together to boost the body’s immune response to viruses, bacteria and many harmful pathogens. Their products contain the health benefits of over 200 naturally occurring mushroom molecules now known to optimize overall immune system performance and can be a vital force when facing the challenges associated with cancer treatments for our pets today.


Symbiotics Colostrum Plus Dog & Cat Supplement (with Immulox and Lactoferrin!)

“Oral administration of bovine colostrum affects intestinal immunity, including an increased percentage of natural killer (NK) cells”.  Science Direct April, 2014

Colostrum Plus comes in capsules or powder


Many members of the animal naturopathic community and even a few in the holistic veterinary community now view immunotherapy as the most promising new way of addressing cancers and compromised immune systems. With these products as well others coming on the market, research and immunology has shown that they increase the NK cell activity dramatically in both animal and human studies.

Please note:  Optimally Organic, Symbiotics and/or Myco Formulas Immune blends are designed to enhance and spark immune system function to it’s optimal level, not to cure disease itself. Any improvement in disease is a direct result of improvement of immune system function and efficiency.

Note: Dietary supplements are designed to improve nutrition and harmonize the body to aid and support the body in healing its self rather than to “treat” disease.



Arina A1, Murillo O, Dubrot J, Azpilikueta A, Alfaro C, Pérez-Gracia JL, Bendandi M, Palencia B, Hervás-Stubbs S, Melero I. (2007). “Cellular liaisons of natural killer lymphocytes in immunology and immunotherapy of cancer”

Vivier, E., Raulet, D.H., Moretta, A., Caligiuri, M.A., Zitvogel, L., Lanier, L.L., Yokoyama, W.M. & Ugolini, S. (2011). “Innate or Adaptive Immunity? The Example of Natural Killer Cells”. Science 331 (6013): 44–49. doi:10.1126/science.1198687


*A consultation is highly recommended before any preventative or healing program is started. A consultation includes a personalized diet and holistic program suggestions that are custom-tailored to your own dog’s individual and personal needs. While I continue to provide educational articles and information for you here, most of these are general in nature. Therefore, I encourage you to set up an appointment with me to tailor a program specifically for your pet’s needs. This is particularly imperative in pets that are aging or with complicated health issues, or if you’ve done a lot of outside reading and have conflicting information.


The information and material provided on this website and by Dr. Jeannie is intended to provide general guidance and education. Nothing on the website or during a regular consultation constitutes traditional allopathic veterinary advice. Consultations are designed to share and suggest additional options to think about, and other areas to explore, based on your individual dog’s condition.  The articles on this website are not intended to diagnose, treat, or cure any disease.

Copyright 2003 -2018 This article is the sole property of Dr Jeanette (Jeannie) Thomason and The Whole (Wholistic) Dog. It cannot be reproduced in any form whatsoever without the expressed written consent of the author.


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