The present invention relates to the field of immunology, molecular biology and therapeutics. In particular, the invention relates to novel artificial feeder cells for activation and expansion of natural killer (NK) cells. The artificial feeder cell expresses endogenous ligands (HLA C1, C2, 5 and Bw4 type) for killer cell immunoglobulin-like receptors (KIRs), non-KIR binding Bw6 ligand, endogenous HLA-E-ligand for inhibitory NKG2A receptor, and comprises at least one stimulatory cytokine either membrane bound or secreted or at least one co-stimulatory ligand where those ligands and cytokines each specifically bind to a cognate receptor on a NK cell of interest, thereby mediating expansion of the NK cell. The invention can be used as an “off the 10 shelf” artificial feeder cell that can be readily designed to expand a NK cell or a NK subset of interest and also specifically expand NK cells modified with a chimeric antigen receptor (CAR). By genetically introducing or knockdown of candidate genes, the artificial feeder cell of the invention can be used to identify the stimulatory, co-stimulatory, and any other factors that mediate growth, expansion and cytotoxicity of a NK cell. Thus, the present invention provides 15 powerful tools for development of novel therapeutics where activation and expansion of the NK cell and of the CAR-NK cell can provide a benefit.