Development of a large-scale, ex-vivo NK cell expansion protocol for use in assessments of NK-targeting therapeutics.

What are NK cells?

Natural killer (NK) cells play a crucial role in our innate immune defence system, mainly by targeting tumour or virus-infected cells. Immunology assays that assess the efficacy and safety of biotherapeutics require the use of primary immune cells, including NK cells. 

NK cells are derived from blood products that rely on donations from healthy donors or patients. They represent only a small fraction of circulating peripheral blood mononuclear cells. This makes acquiring a sufficient quantity of NK cells for in vitro assessments challenging. There exists a need for a solution that would increase the availability of primary donor material. 

Download our NK cell expansion protocol poster by Pim Robertson, Dr Carolyn Rainer, and Dr Robert A. Benson. 

NK cell expansion 

Cryopreserved banks of expanded NK cells could improve assay quality by increasing consistency and repeatability for functional assays. Using artificial antigen presenting cells (aAPCs), we aim to expand NK cells isolated from cryopreserved peripheral blood mononuclear cell (PBMC). 

The protocol uses the following steps:

• Generation of aAPC

• Expansion of NK cells

• Expanded NK cell phenotyping 

• Functional assessment (degranulation and cytotoxicity)

We address the challenge of acquiring a sufficient quantity of NK cells for in vitro assessments. Using the leukemia cell line K562 modified to express membrane bound IL-21 and 4-1BBL, we are able to generate NK cells with enhanced cytotoxicity ex vivo.

While these expanded NK cells show therapeutic promise, further research is required to demonstrate their equivalence to NK cells and their use in in vitro assessments. Nevertheless, these results show future potential for expanded NK cells to be utilised for in vitro assays to determine cytotoxicity against cancer cell lines in conjunction with immunotherapies.