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About Natural Killer Cells & How to Increase & Decrease Them

Written by Joe Cohen, BS | Reviewed by Selfhacked Science Team | Last updated:

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Natural Killer Cells
Natural Killer Cells are high and low in a variety of conditions. They can contribute to and prevent disease. Do YOU have low or high Natural Killer Cells?

Intro to Natural Killer (NK) Cells

Natural Killer (NK) cells are a type of toxic lymphocytes that are critical to the immune system.

NK cells are produced in the bone marrow, lymph nodes, spleen, tonsils, and thymus, where they then enter into the circulation.

They control several types of tumors and microbial infections by limiting their spread and future tissue damage that can occur.

The cells become active around 3 days after infection and respond to tumor formation in the body.

NK cells monitor tumors that may grow by directly triggering the death of tumor cells.

They have the ability to recognize stressed cells without having to have previous exposure to the pathogens, allowing for a fast immune reaction.

NK cells can develop long-lived and highly specific memories to a variety of targets [1].

Extreme genetic diversity is present in both mice and humans coding for NK cells [2].

What Function Does Natural Killer Cells Have?

Individuals lacking NK cells have regular viral infections and die prematurely [3].

Individuals deficient in NK cells are prone to early phases of herpesvirus infection [4] and NK cells help fight HIV.

Mice with less NK cell function are more prone to cancers [2].

Activation of NK Cells

Circulating NK cells remain in their resting phase. NK cells activated by cytokines lead to the invasion of these cells into tissues with pathogen-infected cells [5].

When activated, they secrete cytokines such as interferons [5] and TNF-a [6].

NK cells release a membrane-disrupting protein, perforin, which causes cell death of the target cell [5].

So perforin perforates the “skin” of the pathogen [7].

Conditions With Elevated Natural Killer Cells

Obesity promotes the expression of inflammatory genes in the abdominal fat.

It elevates the number and activity of NK cells in only the stomach fat.

When NK cells are removed, inflammation in abdominal fat is suppressed and insulin resistance is improved.

NK cells control insulin resistance by transmitting proteins that affect macrophages [8].

In Asthma, NK cells contribute to IgE mediated immune-responses and may exacerbate the condition [5].

In Type 1 diabetes, NK cells increase the destruction of the pancreas [5].

Higher NK cells form in women who have reoccurring miscarriages [9].

Th1 Dominance and NK Cells

Th1 dominance (IL-12, IL-2) increases NK Cell activity [10].

On the other hand, NK cells may, in turn, destroy and suppress Th1 cells [11].

I actually don’t do very well with the more potent stimulators of NK Cells. This could either be because I don’t do well with NK cell stimulants, or because NK Cell stimulators have other immune-boosting properties – or both.

Conditions That Have Low Natural Killer Cells

  • Cancer (low activity) [5] – NK cells ‘eat’ cancer cells.
  • Viral infections (low number and activity) [5] – NK cells fight off viruses.
  • CFS (low activity) [11]
  • Multiple Sclerosis (low activity) [11]
  • Rheumatoid Arthritis (low number and activity) [5]
  • Lupus (low number and activity) [5]

Impairment of Natural Killer cells is also associated with advanced aging [12].

Natural Ways to Increase Natural Killer Cells

These strategies lead to increased natural killer cells.




Natural Ways to Enhance Natural Killer Cell Function

These strategies lead to increased function or cytotoxicity of Natural Killer Cells.


  • Exercise [13]
  • Strength training [33]
  • Antioxidants [34]
  • Massage therapy [14]
  • White button mushrooms [35]

Supplements (if overactive immune system)

These supplements are safe if you are Th1 dominant and have an overactive immune system, but you’d still like to stimulate NK Cells.

Supplements (if underactive immune system)

Other: LSD [62]


NK Cell Inhibitors

  • Lectins initiate excess polyamine production, which may be the result of an effort to repair the damage to intestinal microvilli caused by lectins [66]. A high polyamine level may decrease NK cell populations [66].
  • Lipoic Acid [67]
  • CRH/ACTH/Cortisol [68] – from stress or other causes
  • Indoleamine 2,3-Dioxygenase (IDO) – activated by cortisol and inflammation [69]
  • Folic acid (synthetic form) [70]
  • Somatostatin (Growth Hormone-Inhibiting Hormone) [71]

NK Cell Cytotoxicity Inhibitors

Want More Targeted Ways to Combat Inflammation?

If you’re interested in natural and more targeted ways of lowering your inflammation, we at SelfHacked recommend checking out this inflammation wellness report. It gives genetic-based diet, lifestyle and supplement tips that can help reduce inflammation levels. The recommendations are personalized based on your genes.

SelfDecode is a sister company of SelfHacked. The proceeds from your purchase of this product are reinvested into our research and development, in order to serve you better. Thank you for your support.

About the Author

Joe Cohen, BS

Joe Cohen won the genetic lottery of bad genes. As a kid, he suffered from inflammation, brain fog, fatigue, digestive problems, anxiety, depression, and other issues that were poorly understood in both conventional and alternative medicine.Frustrated by the lack of good information and tools, Joe decided to embark on a journey of self-experimentation and self-learning to improve his health--something that has since become known as “biohacking”. With thousands of experiments and pubmed articles under his belt, Joe founded SelfHacked, the resource that was missing when he needed it. SelfHacked now gets millions of monthly readers.Joe is a thriving entrepreneur, author and speaker. He is the CEO of SelfHacked, SelfDecode and LabTestAnalyzer.His mission is to help people gain access to the most up-to-date, unbiased, and science-based ways to optimize their health.
Joe has been studying health sciences for 17 years and has read over 30,000 PubMed articles. He's given consultations to over 1000 people who have sought his health advice. After completing the pre-med requirements at university, he founded SelfHacked because he wanted to make a big impact in improving global health. He's written hundreds of science posts, multiple books on improving health, and speaks at various health conferences. He's keen on building a brain-trust of top scientists who will improve the level of accuracy of health content on the web. He's also founded SelfDecode and LabTestAnalyzer, popular genetic and lab software tools to improve health.

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