Protecting the Body from Internal and External Invaders: The Role of NK Cells in Natural Immunity

How Does the Immune System Work?

Our immune system protects us from harmful pathogens, eliminates foreign substances, and removes abnormal cells, including cells that divide incorrectly and may potentially develop into cancer. (Yes, abnormal cell division can occur daily in the body, but a healthy immune system typically identifies and eliminates these cells.)^[1]

If we compare the body to a city, the skin acts like the city wall, while the immune system functions as the soldiers guarding it against both external and internal threats.^[1,2] The first line of defense is the innate immune system, which we are born with. It includes Neutrophils, which are frontline responders that engulf and destroy bacteria. NK (Natural Killer) Cells are patrol units that eliminate virus-infected and abnormal cells, including early cancerous cells, by directly destroying them. Then, Dendritic Cells are intelligent units that capture information about invading pathogens and present it to other immune cells. If the innate immune system cannot fully control the threat, the adaptive immune system is activated. This system produces specific antibodies that target unique weaknesses of the invading pathogen.

In normal conditions, our immune system can handle most infections. In some cases, when pathogens are particularly aggressive, physicians may prescribe antimicrobial medications to support the body's defense. However, for many viral infections, there are limited specific antiviral treatments, and care is mainly supportive (for example, fever reducers or oxygen therapy). Therefore, the innate immune response, especially NK cells, plays a critical role in rapidly controlling viral infections and eliminating abnormal or cancerous cells.

Signs of a Weakened Immune System

We are often told to stay healthy to maintain strong immunity. But how can we recognize when our immune function may be compromised? The following signs may indicate that your immune system needs attention:^[3]

• Frequent colds

  Experiencing 1 or 2 colds per year is normal. However, frequent infections lasting longer than a week or becoming ill after periods of stress or insufficient rest may suggest reduced immune efficiency.

• Frequent digestive issues

  Symptoms such as constipation, diarrhea, bloating, or abdominal discomfort may reflect an immune imbalance, as a large portion of the immune system is located in the gastrointestinal tract to defend against pathogens entering through food.

• Slow wound healing

  Minor cuts or abrasions typically heal within two weeks. Delayed healing or chronic wounds may indicate infection or impaired immune cell response involved in tissue repair.

• Recurrent infections or inflammation

  Examples include requiring antibiotics more than twice per year (or more than four times annually in children), recurrent ear infections, chronic sinusitis, recurring shingles, or repeated pneumonia. Frequent infections may signal underlying immune dysfunction.

How to Restore Immune Function

If you have any of these symptoms and suspect that your immune system may not be functioning optimally, consider the following strategies to support immune health:

• Eat a balanced diet

  Consume adequate fruits and vegetables rich in vitamins and minerals, which are essential for proper immune function.

  ^[5,7]
• Get sufficient sleep

  Lack of sleep can degrade NK cell activity and disrupt the body's inflammatory balance. It is common to feel unwell after prolonged periods of overwork and insufficient rest. ^[5]

• Exercise appropriately

  Exercise should be moderate, neither excessive nor insufficient. The study shows that both overtraining and inactivity may reduce NK cell function.

  ^[5,7]
• Manage stress

  Chronic stress, particularly in high-pressure work environments, can negatively affect both innate and adaptive immune responses.

  ^[5]
• Monitor immune health regularly

  Many accredited laboratories now offer testing to evaluate the quantity and functional activity of white blood cells, including NK cells, which play an important role in eliminating virus-infected and abnormal cells.

NK Cell Immune Function Testing

Several studies have demonstrated a correlation between NK (Natural Killer) cell levels and the development of various types of cancer.^[8] which makes testing the level of NK cell activity (Strength) another option for those who want to take care of their health and monitor for potential abnormalities.

Some individuals may wonder whether NK cell levels can be directly enhanced, particularly since common recommendations may not always be suitable or sufficient, especially for those experiencing high levels of occupational stress or working in highly competitive environments. Fortunately, modern biotechnology now enables laboratories to isolate NK cells from peripheral blood and expand them before reinfusing them into the bloodstream to enhance immune efficiency. In certain countries, this method has been approved as an adjunctive therapy for patients with solid tumors, used alongside conventional cancer treatments. Different laboratories apply different techniques for NK cell isolation and expansion. MEDEZE uses the Osaki Method from Japan, which focuses on selectively expanding fully developed, highly functional NK cells (Active NK Cells)^[9] These active NK cells are optimized to eliminate cancer cells and virus-infected cells within the body more effectively.

Immune function testing with targeted enhancement of fully functional NK cells (Active NK Cells) at MEDEZE offers a potential proactive strategy for cancer prevention. This approach supports individuals seeking comprehensive and forward-looking health management.