Natural Killer Cell Activation Assay (NKa)
Introduction
Natural
Killer (NK) cells are a lymphocyte subset that express CD56+ on their cell
surface. They are large granular lymphocytes that arise from the bone
marrow and circulate peripherally before localizing to specific tissues.
NK cells are the most prevalent lymphocyte population in secretory
endometrium and in decidua of early pregnancy. They are believed to play a
role in regulating trophoblastic cell migration.
The NK cell activation assay tests the killing function of circulating
NK cells as well as the ability of interleukin-2 (IL2) to stimulate and
intravenous immunoglobulin (IVIg) to suppress that activity. NK activity
can be measured as a bioassay that determines the ability of activated NK
cells to kill their target (K562 cell line).
Increased peripheral and endometrial NK killing activity have been
demonstrated among patients undergoing in vitro fertilization (IVF) who
experienced spontaneous pregnancy loss or IVF failure. Interestingly, 40%
of patients undergoing IVF with a diagnosis of endometriosis displayed
increased NK activity. Identification of patients with increased NK cell
activity will allow appropriate treatment for those who will benefit from
it.
Indications for
Testing
All women who have unexplained infertility,
endometriosis or other pelvic pathology such as pelvic adhesions, a
history of recurrent IVF failures, have elevated APA or ATA and are
undergoing an IVF procedure, or a history of two or more consecutive
pregnancy losses should be tested with the NK Cell Activation Assay
(NKa).
Detection Method
The
percentage of lysed K562 cells is detected by flow cytometry using an
immunofluorescence technique.
Interpretation of Test
Results
Normal NK activity is less than 10% activated NK cells.
Increased NK activity is greater than 10% killing, with increased killing
activity in the presence of IL-2, and decreased activity of at least 50%
from the natural state in the presence of IVIg.
Specimen Collection and Shipping
Requirements
- Collect one (1) green top tube.
- Ship at room temperature in prepaid FedEx mailers overnight, next
day morning.
Turn around Time
Processing
of specimens begins immediately upon receipt at our facilities. Results
are routinely available within 7 to 10 days and are initially faxed, then
mailed to the requesting physician.
Cost
Included in our fees
are specimen collection and shipping materials, all courier and shipping
charges, telephone and written reports, and consultation with physicians.
Please call 1-877-737-7652 for pricing information.
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References
Fukui A, Fujii S,
Yamaguchi E, Kimura H, Sato S, Saito Y. Natural killer cell subpopulations
and cytotoxicity for infertile patients undergoing in vitro Fertilization.
Am J Reprod Immunol 1999;41:413-22.
Kwak JY, Kwak FM, Ainbinder SW, Ruiz AM, Beer AE. Elevated peripheral
blood natural killer cells are effectively downregulated by immunoglobulin
G infusion in women with recurrent spontaneous abortions. Am J Reprod
Immunol 1996;35:363-69.
Kane KL, Ashton FA, Schmitz JL, Folds JD. Determination of natural
killer cell function by flow cytometry. Clin Diagn Lab Immunol
1996;3:295-300.
Sher G, Fisch JD, Maassarani G, Matzner W, Ching W, Chong P. Antibodies
to phosphytidylethanolamine and phosphatidylserine correlate with
increased natural killer cell activity in non-male factor infertility
patients. Hum Reprod 2000;15:XXX-XXX.
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