A type of immune cell that has granules (small particles) with enzymes that can kill tumor cells or cells infected with a virus. A natural killer cell is a type of white blood cell.

Natural killer cells are cells that resemble large granular lymphocytes. They do not express markers of either T or B cell lineage. They are positive for CD16, CD56, and CD 94. These cells do possess Fc receptors for IgG and can kill target cells using antibody-dependent cell-mediated cytotoxicity. They can also use perforin to kill cells in the absence of antibody and killing may occur without previous sensitization.

Type of cytotoxic leukocytes which attack and kill virus-infected or neoplastic cells independent of antibody coating or MHC restriction; may be derived from lymphocytes or monocytes.

A type of white blood cell of the immune system. These cells destroy other cells that fail to display the right chemical flags signaling that they are normal cells.

(killer cells, natural) Bone marrow-derived lymphocytes that possess cytotoxic properties, classically directed against transformed and virus-infected cells. Unlike T CELLS; and B CELLS; NK CELLS are not antigen specific. The cytotoxicity of natural killer cells is determined by the collective signaling of an array of inhibitory and stimulatory CELL SURFACE RECEPTORS. A subset of T-LYMPHOCYTES referred to as NATURAL KILLER T CELLS shares some of the properties of this cell type.