NK cell test is used to evaluate various pathological conditions such as HIV infection, primary immune deficiencies with NK cell damage, NK cell lymphocytosis, solid organ transplantation, and restoration of the immune system following bone marrow or hematopoietic stem cell transplantation and evaluation of NK cells in neoplasms.
Natural killer cells (NK) are derived from primitive multipotent hematopoietic cells but grow independently of the thymus. They are an important subset of lymphocytes (about 10 - 15% of blood mononuclear cells) and are part of the innate immune system since these cells do not rearrange their DNA to acquire specificity. NK cells play an important role in the host's defense against viral infections as well as in tumor surveillance. They are also a component of the acquired immune response through the production of cytokines.
NK cells are determined by the expression of various receptors on their cell surface and do not constitute a homogeneous population. In general, the most common combination of surface markers used to determine most NK cells is the absence of CD3 (CD3-) together with the expression of CD56 and CD16 (CD56 + CD16 +). However, not all NK cells express CD56 and CD16 markers uniformly and therefore can be subdivided into sub-populations based on the expression of these two molecules. CD16 + CD56 +/-, which are CD3-, are referred to as cytotoxic NK cells, while CD56 + CD16- NK cells are called NK regulatory cells and are cytokine-secreting cells. Therefore, cytotoxicity and cytokine production are the main functions of NK cells. Cytotoxicity can be subdivided into natural cytotoxicity that is largely directed to virus-infected cells or cancer cells in the absence of prior stimulation or immunization and antibody-dependent cellular cytotoxicity (ADCC) directed against antigens covered with antibodies.
Deficiencies of NK cells may be part of a larger immune syndrome or an individual deficiency affecting the function or number of NK cells.
Individual NK cell deficiencies include absolute NK cell deficiency (ANKD), classical NK cell deficiency (CNKD) as well as functional NK cell deficiency (FNKD). NK cell dysfunction has been reported in systemic juvenile rheumatoid arthritis and macrophage activation syndrome. There are also more recent studies on the role of NK cells in allergies and autoimmune diseases. Patients with HIV-1 show a gradual loss of NK cells associated with the progression of the disease. NK cells also play an important role in regulating viral infections and their deficiency predisposes to susceptibility to herpes virus infections. NK cell lymphocytosis is observed in NK tumors, extranodal NK lymphoma, aggressive NK cell leukemia, and NK cell stem lymphoma.
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
