Terry & Lynda Sherback
Independent Univera Associates

Natural Killer (NK) Cells
Natural Killer (NK) cells - NK cells were discovered in the 1970's and are a subset of large granular lymphocytes that are cytotoxic cells. They are called "natural" killers because they, unlike cytotoxic T cells, do not need to recognize a specific antigen before swinging into action. They are capable of spontaneously killing tumor or virus-infected cells. In several immuno-deficiency diseases, including AIDS, natural killer cell function is abnormal. Natural killer cells may also contribute to immuno-regulation by secreting high levels of influential lymphokines.

Natural Killer (NK) cells have no immunological memory and are independent of the adaptive immune system, NK cells make up approximately 15% of the human white blood cells. Their specific function is to kill infected and cancerous cells.

Recent research reveals that NK cells are involved in multiple effector, regulatory and developmental activities of the immune system. Research has confirmed that low NK cell activity causes one to be more susceptible to autoimmune diseases such as CFS, viral infections and the development of cancer cells.

Natural Killer Cell killing a cancer cell.

"This photograph is of a Natural Killer Cell as it prepares to destroy a cancer cell by attaching a tentacle with venom bags to the cancer cell.
We thank Dr. Thornthwaite for his very early work in 1972 for the image of the Natural Killer Cell killing a cancer cell."

Role in Human Health
Any statement that natural killer (NK) cells play an "important role" in human health is as casual as saying that the brain is important for bodily function. If our brain is not present and active we cannot continue "living". If our immune system is not armed and working well we will also not continue "living" for very long. NK cell activity is to the immune system, what brain activity is to the body.

Activated NK cells produce a variety of cytokines, including interferons, interlukins, TNF (Tumor Necrosis Factor), hematopietic cell growth factors and other growth factors. There is substantial evidence that indicates the involvement of NK cells in the interactions of the immune system with the neuroendocrine axis. They also appear to be responsible for activities at the interface between the immune system and the reproductive and neurological systems.

NK Cell Activity
NK cell activity and NK cell count are not the same. NK cells may be present in sufficient numbers, but unless they are activated they are ineffective in doing their job. Decreased NK cell activity is linked to the development and progression of many diseases. According to the Center of Disease Control, low NK cell activity is present in all illness. NK cell function appears to be a biologic marker for disease and is an important indicator for declining or improving health.

The following assertion can be made; if one is suffering from an illness, be it chronic, recurring or acute, the NK cell activity would be below normal. The restoration of NK cell activity to a high normal would be desirable, if not necessary, for recovery.

Low NK cell activity begins with stress of some type. When the body is unable to adequately adapt to the environment there is a resulting compromise of body function. Stress comes through loss of sleep, overwork, emotional encounters, lack of exercise, poor nutrition, exposure to toxins, exposure to germs etc.

Excessive stress causes many detrimental changes in the body physiology and particularly the immune system. There is research evidence that there is a relationship between Natural Killer (NK) cell activity and reaction to emotional stress. There is low NK cell activity in individuals who have difficulty in handing stress and those suffering from behavioral disorders.

Acute low NK cell activity resulting from temporary stress can be eliminated with the elimination of the stress factor. For example, if we are over-tired and under-nourished we can simply rest and eat properly for a few days and recover. However when we become continually immune compromised we start developing recurring problems which may lead into serious or chronic conditions.

NK cell activity level is lowered in times of stress and can become chronically low with chronic stress. Research shows that normal NK cell activity is essential to the recovery and maintenance of good health. One way to offset the effects of stress is to normalize NK cell function.

"Reduced Natural Killer cell activity is present in all illness. Everyone with low NK activity is more vulnerable to infectious disease." Lewis L. Lanier of DNAX Research quoted in the publication Immunity.

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