natural killer cell

biology

Also known as: NK cell

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Last updated

July 1, 2026

Quick Summary

Natural killer (NK) cells are a type of lymphocyte that plays a role in the innate immune system. Unlike other lymphocytes, NK cells do not require prior exposure to a target cell to act. They are capable of destroying the body's own cells that have become cancerous or infected with a virus.12

NK cells recognize dividing cells and bind to them, inserting granules that cause the cells to leak and die. They are the third most abundant type of lymphocyte and develop from hematopoietic stem cells. Interferons, a type of protein, can enhance immune surveillance by activating NK cells.23

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immune system
Activation of killer cells
…either cytotoxic T cells or natural killer cells, have receptors that bind to the tail portion of the IgG antibody molecule (the part that does not bind to antigen). Once bound, killer cells insert a protein called perforin into the target cell, causing it to swell and burst. Killer cells…
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…either cytotoxic T cells or natural killer cells, have receptors that bind to the tail portion of the IgG antibody molecule (the part that does not bind to antigen). Once bound, killer cells insert a protein called perforin into the target cell, causing it to swell and burst. Killer cells…
Read More

immune system
Natural killer (NK) cells
Natural killer cells do not attack invading organisms directly but instead destroy the body’s own cells that have either become cancerous or been infected with a virus. NK cells were first recognized in 1975, when researchers observed cells in the blood…
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Natural killer cells do not attack invading organisms directly but instead destroy the body’s own cells that have either become cancerous or been infected with a virus. NK cells were first recognized in 1975, when researchers observed cells in the blood…
Read More

white blood cell
Major classes of white blood cells
…included in this group are natural killer (NK) cells, so named for their inherent ability to kill a variety of target cells. In a healthy person, about 25 to 33 percent of white blood cells are lymphocytes.
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…included in this group are natural killer (NK) cells, so named for their inherent ability to kill a variety of target cells. In a healthy person, about 25 to 33 percent of white blood cells are lymphocytes.
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