Description

Human NK Cells

Human NK cells make up approximately 5-15% of PBMCs in a typical adult. These cells carry activating and inhibitory molecules that influence their activation status.

When activated, NK cells can lyse infected or transformed cells through natural cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC).

Human NK Cell Application Summary

Purified human blood NK cells are a good source of cells to study the biology of NK cells and their role in the immune system. They can be used for a variety of stimulation-dependent functional experiments to assess cytokine production and cytotoxicity.

With the current trend toward development of immuno-modulatory drugs, NK cells are an ideal source of cells to test cytotoxicity and cytokine production in the presence of therapeutic molecules.

The negative isolation of NK cells leaves them untouched without any antibody binding to cell surface markers that may influence function. This method leaves all cell surface proteins eligible to be bound to antibodies or other molecules for functional or population characterization studies.

In contrast, positive isolation of NK cells may lead to internalization of the marker that was used to isolate the cells.  In most cases, these markers are only used for identification purposes and may not have any effect on function, but it will depend on the organism and function.  Therefore, cells isolated using this method may also be employed for functional or population characterization studies with the knowledge that the isolation marker may be internalized and not

NK Cell Enrichment

Collection of samples

Leukapheresis was performed on verified healthy donors at a world-renowned blood center to obtain PBMCs. PBMCs were carefully washed to remove excess buffers according to iQ Biosciences’ standard operating procedures to obtain clean and healthy PBMCs.

Isolation of Human NK cells

To enrich for NK cells by the negative isolation method, PBMCs were incubated with antibodies against T cells, B cells, dendritic cells, monocytes, granulocytes, and erythrocytes, and subsequently subjected to a magnet. Cells labeled with the antibodies bound to the magnet through the test tube wall, while unlabeled cells, the NK cells, were decanted into a fresh tube to obtain the enriched population.

For the positive selection method, PBMCs were incubated in a test tube with antibodies against an NK cell-specific marker, which will vary depending on the species of the organism, and subsequently subjected to a magnet, similar to negative isolation.  However, the cells that were decanted into the fresh test tube were the non-NK cells, which can be used for other purposes, while the labeled NK cells were left bound to the magnet through the test tube wall.  The test tube was then removed from the magnet to release the purified NK cells directly into the test tube.

Contact us for more information about purchasing our magnetically isolated NK cells.

Purity

A small aliquot of cells was tested for post-sort purity by flow cytometry analysis. Purity of NK cells, as defined by CD56 expression, was > 96% (Figure 1).

Figure 1. Purity of NK cells after negative magnetic isolation from PBMCs.  In this representation, human PBMCs were incubated with antibodies against T cells, B cells, dendritic cells, monocytes, granulocytes, and erythrocytes and subjected to negative magnetic isolation to obtain untouched NK cells.  A small aliquot was taken after selection to evaluate post-sort purity (right).  Percent of NK (CD56+) cells in PBMCs is also shown (left).

Cryopreservation and storage

Purified NK cells were cryopreserved carefully using iQ Biosciences’ cryopreservation protocol that ensures high viability (> 90%) after thawing.

Cells should be stored at < -120°C once they are received, such as within a liquid nitrogen tank (vapor phase).