The bulk of the cells detected that express CD56 on their surface have a particular function that accounts for their name, “natural killer cell”. This function is, of course, the ability to identify and then kill foreign or abnormal cells. Identification of the number and activity of these cells gives us an idea of the strength of this killing capacity. However, it has been known for some time, that the only way to assess the activity of these cells in the body is to measure their activity in the laboratory. The most precise way to accomplish this is to mix the patient’s natural killer cells with target cells and then measure the amount of killing that the target cells experience. This killing activity is measured very precisely using a flow cytometer.

As was described in the A Guide to Interpreting the Results of the Reproductive Immunophenotype document, natural killer cells have a number of diverse functions. Aside from directly killing targeted cells, they can produce cytokines that direct the killing activity of other cells. One of these cytokines is tumor necrosis factor (TNF).

The test for NK cell activity is performed routinely in the Center’s laboratory. Natural Killer cells from the woman are separated from her blood and are cultured at different dilutions with target cells that they can kill. The target cells used are from a cancer cell line that, serendipitously, share many similarities to placentas and embryos. After two to four hours of culturing the patient’s NK cells with the target cells, a special DNA dye called propidium iodide is added to the culture. This dye is taken up by the DNA of the cells that have been killed. The living cells do not take up the dye. The cell suspensions are then put into the flow cytometer and the percentage of dead to live cells at the different dilutions determined.

How to Get the Test
Our registered patients may obtain this test by following the steps below:

1. The test must be scheduled with Chris Sanow at (408) 356-9500 or by e-mail at This e-mail address is being protected from spambots. You need JavaScript enabled to view it
2. Our physicians will interpret this test.
3. The blood is shipped at room temperature by overnight mail and must arrive Monday - Thursday. No blood is received on Friday or the Weekend since the test must be done immediately on fresh blood.
4. The test results are available to the patient 72 hours after receipt of the blood.
5. The couple must give a working telephone number, FAX or e-mail address for immediate communication at the time the test results are available.
6. Four (4) 10 cc Green Topped Tubes (heparin) are required from the woman. Blood drawing and shipping instructions are faxed, e-mailed or called into the laboratory or doctor's office selected to do the drawing. Some laboratories will not draw or ship blood unless their laboratory is doing the test. Couples should inquire about this prior to scheduling since the blood drawn must be air expressed to the laboratory in Chicago.
7. The insurance codes and the cost of the test will be given to the patient when scheduling is done. These codes can be presented to the insurance provider pre testing to determine benefits.

Reference
Gilman-Sachs A, DuChateau BK, Aslakson CJ, Wohlgemuth GP, Kwak JY, Beer AE, Beaman KD. Natural killer (NK) cell subsets and NK cell cytotoxicity in women with histories of recurrent spontaneous abortions. Am J Reprod Immunol. 1999 Jan;41(1):99-105.