CD16,56 Percent (Natural Killer Cell)

This test quantifies the absolute number and percentage of natural killer (NK) cells in the blood by identifying the expression of surface markers CD16 and CD56 on lymphocytes. NK cells are a crucial component of the innate immune system and play a pivotal role in identifying and destroying virally infected or malignant cells. This test is part of a broader immunophenotyping panel often used to assess immune function.

 CD16/56 absolute count analysis helps in diagnosing and monitoring immune deficiencies, certain hematologic malignancies, and autoimmune disorders. In patients with recurrent infections, especially viral infections, reduced NK cell activity may indicate an underlying immune defect. Conversely, elevated levels may be associated with chronic inflammation or certain lymphoproliferative conditions.

It is typically recommended for individuals with unexplained infections, suspected immunodeficiency syndromes, or as part of the evaluation for bone marrow or stem cell transplant eligibility. It may also be used in cancer patients to monitor immune recovery post-therapy or to evaluate the efficacy of immunomodulatory treatments.

Low absolute NK cell counts may indicate a primary immunodeficiency such as NK cell deficiency or severe combined immunodeficiency (SCID). High levels can be found in conditions like chronic viral infections, autoimmune diseases, or certain leukemias and lymphomas. Interpretation of results should always be done in context with clinical presentation and other immune markers.

The test requires a peripheral blood sample collected in an EDTA tube. Flow cytometry is used to identify and count the lymphocyte populations expressing CD16 and CD56. Results are typically available within a few days and are reported as both absolute count (cells/μL) and percentage of total lymphocytes.