Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
This test measures the absolute number of natural killer cells in your blood. These cells are identified by surface markers called CD16 and CD56 on white blood cells that also carry CD45. The measurement is performed by flow cytometry, a method that tags cells with fluorescent antibodies to count and classify them.
Natural killer cells are part of your innate immune system. They help the body respond quickly to infected or abnormal cells. The result is reported as an absolute count, and it is often ordered together with other lymphocyte subsets such as T cells and B cells to give a broader picture of immune health.
Your natural killer cell count helps your clinician understand how well your immune system is functioning. The test may be ordered if you have frequent or unusual infections, to evaluate suspected immune deficiencies, to monitor recovery after chemotherapy or stem cell transplant, or to follow the effects of medicines that can influence lymphocytes.
Changes in natural killer cell numbers can occur with viral infections, autoimmune or inflammatory conditions, and certain blood disorders. The information can guide further testing or treatment decisions, including adjusting medications that affect the immune system or planning vaccinations and infection prevention strategies.
Your result is interpreted in the context of your symptoms, other blood counts, and medical history. Small day-to-day variations are common, and temporary shifts can occur with stress, illness, or recent vaccination. If a result is unexpected, your clinician may repeat the test to confirm it and review factors such as sample timing, transport, or recent medications.
If your count is lower than anticipated, next steps may include checking other lymphocyte subsets, assessing overall white blood cell counts, screening for infections, or considering a functional natural killer cell assay. If it is higher than anticipated, your clinician may look for signs of active inflammation, review recent illnesses, and correlate with additional laboratory or imaging studies. In all cases, discuss what the result means for you and whether any follow-up is needed.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Viral illnesses and recent immunizations can transiently raise or lower natural killer cell numbers. Tell your clinician about any recent fevers, symptoms, or shots when interpreting results.
Corticosteroids, chemotherapy, biologics, and immunomodulators can reduce or shift lymphocyte subsets, including natural killer cells. Provide a complete medication list, including infusions and steroids.
Delayed processing, extreme temperatures, or collection late in the day can alter flow cytometry counts. Consistent collection conditions and prompt laboratory handling support reliable results.
Acute stress, vigorous exercise, and nicotine can temporarily mobilize natural killer cells into the bloodstream. Avoid intense workouts and note tobacco use before testing when possible.
Natural killer cell numbers vary across the lifespan and during immune reconstitution after chemotherapy or transplant. Your clinician will interpret results in light of your age and recovery stage.
Active autoimmune disease or systemic inflammation can change natural killer cell distribution. Sharing current symptoms and treatments helps align the count with clinical context.
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