False statement about NK (natural killer) cells:

NK cell cytotoxicity is the nonimmune, MHC-unrestricted, non-antibody-mediated killing of target cells, which are usually malignant cell types, transplanted foreign cells, or virus-infected cells. NK cells account for ~5-15% of peripheral blood lymphocytes. NK cells express surface receptors for the Fc poion of IgG. They are derived from large granular cells. Ref: Harrisons principles of internal medicine, 18th edition, chapter: 314