It seems like they are good candidates for NK cell activation due to their lack of HLA Class I molecules - these molecules bind to inhibitory killer immunoglobulin-like receptors (KIRs) on NK cells.

Article Expression of ligands for activating natural killer cell rec...

Hello Huang Yuhua

The MHC class I deficient K562 cell line is used as a feeder cell to induce NK cell proliferation. Besides the lack of surface major histocompatibility complex class Ia ligands, K562 shows the expression of ligands for activating natural killer cell receptors. These cells express a higher intensity of ligands for Natural Killer G2D (NKG2D) and the natural cytotoxicity receptors, which are implicated in triggering natural killer cell cytotoxicity.

There are also genetically modified or ligand transfected K562 used to increase the number of activated NK cells. The modified K562 cells expressing 4-1BB ligand and IL-15 enhance NK cell expansion almost 100-fold. Also, genetically modified K562-based antigen presenting cells expressing membrane-bound IL-21 promotes NK cell expansion almost 47,000-fold.

These genetic modifications in K562 cells can be used to further enhance their potential to expand NK cells.

You may want to refer to the papers attached below for more information.

https://www.bloodresearch.or.kr/journal/view.html?uid=1733&vmd=Full

https://ashpublications.org/hematology/article/2013/1/234/20900/Bringing-natural-killer-cells-to-the-clinic-ex

Article Expression of ligands for activating natural killer cell rec...

Best.

Thank you so much. Your answer helps me a lot. I will read these articles to know more details. Best wish!@Malcolm Nobre @Carles Puig Saenz