NK cell
Meaning of NK cell: An NK cell is a white blood cell of the innate immune system able to kill infected or abnormal cells on first contact.
Definition of NK cell
An NK cell, short for natural killer cell, is a type of lymphocyte that functions as part of the innate immune system rather than the adaptive immune system that T cells and B cells belong to. It patrols the blood and tissues, ready to act against abnormal cells immediately, without first needing to be trained to recognize a specific target.
An NK cell identifies a target largely by detecting the absence or alteration of certain surface markers that healthy cells normally display, a change commonly seen in cells infected by a virus or transformed into a tumor cell. Once triggered, it releases proteins that cause the abnormal cell to break apart.
Because an NK cell does not require prior sensitization, it can respond within a short time of encountering a threat, complementing the slower but more targeted response that develops later through T cells and antibodies.
Also known as
Used in a sentence
The immunology panel included a measurement of the patient's NK cell count.
Good to know
An NK cell responds to abnormal cells through the loss of normal surface markers rather than the recognition of a specific foreign antigen, a distinction from how T cells identify their targets.