<prompt> False statement about NK natural killer cells:They are derived from large granular cellsThey comprise about 5 of human peripheral lymphoid cellsThey are MHC restricted cytotoxic cellsThey express IgG Fc receptors  <response>: 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 