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Natural killer cell

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Definition

noun, plural: natural killer cells

A large granular lymphocyte that destroys stressed (infected) cells and cancer cells


Supplement

Lymphocytes are a type of white blood cells. They may be grouped into two: small and large lymphocytes. The small lymphocytes include B lymphocytes (involved in humoral immune response, particularly in antibody production) and T lymphocytes (involved mostly in the cell-mediated immune response). The large lymphocytes include the natural killer cells.

Natural killer cells are immune cells that can recognize stressed cells (e.g. viral-infected cells) and subsequently kills them. It can also attack tumor or cancerous cells. It releases chemicals that lyse the target cell resulting to its death. Natural killer cells are one of the first cells to mount an immune response, especially against viral-infected cells. Unlike other lymphocytes, the natural killer cell can recognize a stressed cell and kill it even without a prior activation, i.e. the initial need to recognize antibodies or major histocompatibility complex (MHC) presented on the cell surface of the target cell.


Natural killer cells are derived from the prolymphocytes, which in turn came from the lymphoblasts from common lymphoid progenitor cells. The maturation of prolymphocytes into natural killer cells occurs in bone marrow, lymph nodes, thymus, spleen, and tonsils.

Natural killer cells should not be confused with a natural killer T cell. The latter is a type of T cell and can be identified by the receptor that binds with a CD1 molecule of an antigen-presenting cell. Natural killer T cell has antigen-specific receptors. This means that the natural killer T cell is more specific in its immune response. The natural killer cell is less specific and therefore attacks a wider range of pathogens.

In humans, the biomarkers of a natural killer cell are CD16 and CD56.


Abbreviation/Acronym:

  • NK cell

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