[Check! Health] What Is My Immune Score? Check with NK Cell Test

Immunity is the phenomenon by which our body's internal environment defends against external antigens. It refers to the ability to maintain internal balance by eliminating pathogens, infected cells, and other foreign substances through resistance to external invaders. The immune system consists of the first line of defense, which includes physical external barriers such as the skin and mucous membranes, and the second line of defense, which exists within the body to protect against pathogens that enter the body. The second line of defense involves defensive cells, inflammatory responses, defensive proteins, and actions through fever, with various immune cells such as macrophages, T cells, B cells, and NK cells performing these functions.

[Photo by GC Green Cross Medical Foundation]

Immune cells strengthen their defensive ability against invading pathogens, foreign substances, and viruses as they become activated. A representative natural immune cell is the natural killer (NK) cell. This is a type of white blood cell responsible for innate immune responses and is the only immune cell in the body that directly identifies and destroys abnormal cells such as virus-infected cells or cancer cells. NK cells also secrete proteins that induce the activation of other immune cells, playing an important role in maintaining overall immunity. There are approximately 100 million NK cells in the body, and generally, their activity peaks in the 20s and gradually decreases thereafter, dropping to half the level of the 20s by the 60s and to one-third by the 80s.

The anticancer immunity of NK cells has been shown through numerous studies to be proportional to their activity rather than their number. According to one study comparing NK cell activity between patients with the so-called five major cancers?stomach cancer, breast cancer, prostate cancer, pancreatic cancer, and colon cancer?and healthy control groups, the NK cell activity level in the control group was 800 pg/mL, whereas it was significantly lower at 150 pg/mL or less in the cancer patient group. If NK cell activity is high, abnormal cells can be attacked and destroyed, maintaining a healthy body; conversely, if activity is low, abnormal cells cannot be distinguished and the cells fail to perform their natural functions, weakening immunity and increasing the likelihood of various diseases such as infections and cancer.

This is why NK cell activity testing is consistently gaining attention as an immune measurement indicator among people concerned about immunity or seeking to prevent diseases including cancer. It is a simple, non-invasive test that requires only 1 mL of blood, artificially activating cells in the blood through stimulants and quantitatively measuring interferon-gamma secreted by NK cells to assess immunity against diseases including cancer.

NK cell activity testing is a popular test that healthy individuals can undergo to check their immunity for health management purposes. It allows early detection of the presence of abnormal cells such as cancer cells or environments that may lead to future disease onset. Patients with cancer or other diseases can also use this test under the guidance of their primary physician for monitoring treatment progress and early detection of recurrence, aiding in long-term health management.

Test results are provided based on large-scale data from tests conducted on healthy individuals, categorizing immune status into four sections: normal, attention, caution, and abnormal. These categories are statistically derived to help interpret the immune status of the test taker and are useful for result interpretation. However, since NK cell activity testing is not a definitive diagnostic test for diseases, a low value does not necessarily indicate the presence of any disease, so consultation with a specialist is recommended.

Dr. Lee Ji-won, a specialist at GC Green Cross Medical Foundation, stated, “Interest in immunity and health has increased since the COVID-19 pandemic, and with the continuing heat waves and rainy seasons, interest in immune enhancement is growing even more. NK cell activity testing, which indirectly assesses individual immune capacity, will be helpful in leading a healthy life.”