Are you well equipped to fight cancer and other diseases?


Your immune system works much the same way an army would, protecting you from foreign invaders trying to kill or damage your cells or organs. Your natural defense system fights pathogens such as bacteria, viruses and cancer cells to keep you healthy. Sometimes, these pathogens are small (e.g. a virus) and only require a few fighting cells (or soldiers) to kill them. Other times, pathogens are big (such as a tumour) and an entire squadron of soldiers is needed to kill them. When you have a strong immune system, or personal army, you are more likely to be well protected against infections, cancer and other diseases.


Your personal army is made up of two types of soldiers: the soldiers of the innate immune system and those of the adaptive immune system. The soldiers in the innate system are your first line of defense and hold down the fort until the soldiers in the adaptive system are trained and ready to attack invaders.


The soldiers in your innate immune system include natural killer (NK) cells, a type of white blood cell or “lymphocyte.” These cells play a key role in your immune system, as they are the first line of defense against dangerous foreign cells. When a foreign cell appears, the NK cells immediately recognize it and, like defending soldiers, they move through your body to confront the foreign cell.
Upon arrival, two things happen:


An NK cell attaches to the foreign cell, causing a chain reaction that directly kills the foreign cell.
This is called cytotoxicity - “cyto” for cell and “toxicity” for killing.


The NK cells work together to release a protein in the blood called cytokine (“cyto” for cell and “kine” for movement).
The cytokines are messengers that call upon other cells in the immune system to help the NK cells kill the foreign
cells (or help prevent tumour growth).


NK cell function, also called NK cell activity, indicates how well your body can defend itself against dangerous foreign cells. NK cell activity helps your doctor assess the strength of your immune system for fighting off infections or cancer cells.
Measuring NK cell activity does not tell your doctor if you have a disease or an illness; it does, however, help him or her decide what other types of tests you may need to have done.


A number of conditions and diseases may affect your NK cell activity. For example, people who are highly stressed or who are not sleeping or eating well may have lower NK cell activity.


NK cell activity has been shown to be much lower in people with cancer. Nevertheless, if your doctor finds that your NK cell activity is very low, this does not mean you have cancer. Rather, it may signal that you are at higher risk for cancer or that you have an unrecognized infection. Your doctor will discuss your test results with you and decide (based on your family history, symptoms and risk factors) whether you should be retested or have additional tests.



2 Billion

There are approximately 2 billion NK cells in your body at any one time.


A pathogen is anything that causes a disease.


The soldiers in the innate immune system are always on patrol,
they guard the front line and recognize and kill dangerous foreign
cells on sight (this is known as “immunosurveillance”).

» Found throughout your body
» No need for previous exposure to any pathogens
» Not specific about their targets
» React quickly to invaders


The adaptive immune system is made up of soldiers that are trained to
target very specific invaders; they are your “Special Forces”. Unlike the
front-line soldiers that kill all pathogens on sight, these soldiers are trained to attack only specific pathogens. They help your body to recollect attackers so that it is better prepared to fight them in the future.

» Training and initial deployment takes time
» Must learn to recognize their targets
» Once trained, will never forget a target
» React quickly ensuing exposure to invaders


If your NK cell activity is low and you are over the age of 50, your doctor may order certain screening tests.
If you are a man:
» PSA test and/or digital rectal exam to look for prostate cancer.
If you are a woman:
» Mammogram, and sometimes ultrasound, to look for breast cancer.
For men and women:
» Stool test and/or colonoscopy to look for colon cancer.
Based on your test results, your doctor will determine whether further tests are required.
Not all patients want to follow their doctor’s advice when it comes to recommended screening tests: some patients are uncomfortable with the stool test, others are afraid of colonoscopies, while some women do not like mammograms.

It is important to keep in mind that knowing your NK cell activity helps your doctor to better understand your situation, therefore these tests are important.


NK cell activity is measured with a simple and affordable blood test. At the blood collection centre or medical clinic, a nurse or technician collects 1 mL of blood for the test.


Based on your NK cell activity results, your doctor may also recommend some lifestyle changes (weight loss, exercise, diet changes, smoking cessation, etc.), which could help to improve your immune system and improve your ability to fight cancer and other diseases.

Be sure to speak to your doctor about NK cell activity and what you can do to improve your immune system.


Cheprasov A. What Is the Immune System? - Our Body's Defense Against Pathogens [Internet]. 2015 [cited 2015 Feb 4]. Available from:


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