The blood test for NK cells typically involves assessing either the number of Natural Killer (NK) cells or, more commonly and clinically relevantly, their activity or functionality. This test helps evaluate a part of your immune system.
Understanding NK Cell Tests
Natural Killer (NK) cells are a type of white blood cell crucial for your immune defense. They are particularly important for recognizing and killing virus-infected cells and some cancer cells without prior sensitization. Blood tests for NK cells can provide different types of information:
1. NK Cell Count (Phenotyping)
This test measures the absolute number or percentage of NK cells in a blood sample. It is usually performed using a technique called flow cytometry, which identifies NK cells based on specific markers (like CD16 and CD56) on their surface.
- What it shows: Provides information about the quantity of NK cells circulating in your blood.
- Limitations: A normal count doesn't necessarily mean the cells are working correctly.
2. NK Cell Activity/Functionality Test
This test assesses how well your NK cells are performing their job – primarily their ability to kill target cells. Blood is incubated with laboratory-grown target cells (often cancer cells or cells designed to be easily killed by NK cells), and the test measures how effectively the patient's NK cells destroy these targets.
- What it shows: Measures the functional capacity of your NK cells.
- Significance: As stated in the reference, low NK cell activity is one of the indicators for the diagnosis of diseases and weak immune system. If NK cell activity is consistently low, you should find the reason and further tests should be taken in accordance to a physician's investigation. A person with low NK cell activity might have a lower immune capacity.
- Clinical Relevance: This test is often considered more informative than just the count when evaluating immune function related to NK cells, especially in the context of recurrent infections, certain autoimmune conditions, or evaluating immune status in specific diseases.
Why NK Cell Testing is Done
Healthcare providers may order an NK cell test for several reasons:
- Investigating recurrent infections, especially viral ones.
- Evaluating immune deficiencies or disorders.
- Assessing immune function in certain cancers or autoimmune diseases.
- Monitoring immune status.
A simplified comparison of the two types of tests:
| Test Type | What it Measures | What it Tells You |
|---|---|---|
| NK Cell Count | Number of NK cells | Quantity of cells present |
| NK Cell Activity | Ability of NK cells to kill | How well the cells are functioning |
In summary, the blood test for NK cells can measure their quantity or their activity. The activity test is particularly important as low NK cell activity is one of the indicators for the diagnosis of diseases and weak immune system, suggesting that further investigation by a physician is necessary.
