Source:http://linkedlifedata.com/resource/umls/id/C1155064
GO: The change in morphology and behavior of a natural killer cell in response to a cytokine, chemokine, cellular ligand, or soluble factor. [GOC:mgi_curators, ISBN:0781735140],NCI: NK Cell Activation involves interaction with virus-infected or transformed cells by diverse adhesion or co-stimulatory molecules and release of cytokines, chemokines, and lethal chemicals from granules.