Enrichment of NK Cells from Human Blood with the RosetteSep Kit from StemCell Technologies


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Natural killer cells are a small population of lymphocytes. Here we show how to isolate these cells from human blood by negative selection, using a kit from StemCell Technologies. The cells obtained are viable and untouched by antibodies, and therefore ready to be used for a number of procedures.

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Beeton, C., Chandy, K. G. Enrichment of NK Cells from Human Blood with the RosetteSep Kit from StemCell Technologies. J. Vis. Exp. (8), e326, doi:10.3791/326 (2007).


Natural killer (NK) cells are large granular cytotoxic lymphocytes that belong to the innate immune system and play major roles in fighting against cancer and infections, but are also implicated in the early stages of pregnancy and transplant rejection. These cells are present in peripheral blood, from which they can be isolated. Cells can be isolated using either positive or negative selection. For positive selection we use antibodies directed to a surface marker present only on the cells of interest whereas for negative selection we use cocktails of antibodies targeted to surface markers present on all cells but the cells of interest. This latter technique presents the advantage of leaving the cells of interest free of antibodies, thereby reducing the risk of unwanted cell activation or differenciation. In this video-protocol we demonstrate how to separate NK cells from human blood by negative selection, using the RosetteSep kit from StemCell technologies. The procedure involves obtaining human peripheral blood (under an institutional review board-approved protocol to protect the human subjects) and mixing it with a cocktail of antibodies that will bind to markers absent on NK cells, but present on all other mononuclear cells present in peripheral blood (e.g., T lymphocytes, monocytes...). The antibodies present in the cocktail are conjugated to antibodies directed to glycophorin A on erythrocytes. All unwanted cells and red blood cells will therefore be trapped in complexes. The mix of blood and antibody cocktail is then diluted, overlayed on a Histopaque gradient, and centrifuged. NK cells (>80% pure) can be collected at the interface between the Histopaque and the diluted plasma. Similar cocktails are available for enrichment of other cell populations, such as human T lymphocytes.


A detailed protocol is included with each Rosette Sep isolation cocktail and is available online on the StemCell technologies website 1.

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The cells isolated using this technique can be further separated into different populations using other cell separation kits.

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Name Type Company Catalog Number Comments
Rosette Sep cocktail for human NK cells Reagent Stem Cell Technologies 15065
PBS, steile, 1x Reagent GIBCO, by Life Technologies 14040-058
Fetal calf serum (FCS, FBS) Reagent GIBCO, by Life Technologies 16140-071
Histopaque-1077 Reagent Sigma-Aldrich 10771
PBS supplemented with 2% FCS and Histopaque solutions must be brought to room temperature before the begining of the procedure.



  1. Procedures and instruction manuals. http://www.stemcell.com/technical/technicalrsproc.aspx Forthcoming.



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