NK cells

What are Natural Killer (NK) Cells?   Natural killer (NK) cells are large, non-phagocytic lymphocytes that function as a part of the body’s innate immune system. Unlike other lymphocytes, NK cells do not have to be activated and are not as dependent upon MHC molecules to identify target cells, but participate in immunological surveillance.

How do NK Cells Function?

NK cells are cytotoxic lymphocytes, containing molecules such as cytokines, perforins, and granzymes. As NK cells come in contact with other cells, activation and inhibitory receptors found on the NK cells membranes can determine whether the cell is a healthy self cell, or a pathogenic or aberrant cell. Once the cell is identified as a target cell, the NK cell releases the cytotoxic proteins which destroy the abnormal cell through the induction of apoptosis and cytolysis. NK cells also activate other immunologic cells through the release of interferons.

NK Cells in Immuno-oncology

While there is evidence of the efficacy of the function of NK cells against cancer cells, it has limitations. The ratio of NK cells to other lymphocytes in the blood is quite small and cancer cells with fewer activating signals on their surface can evade detection and activation of NK cells.

The development of new therapies in immuno-oncology using NK cells while trying to circumvent the limitations of use is currently being explored.

Source: Shimasaki, N., Jain, A., & Campana, D. (2020, January 6). NK cells for cancer immunotherapy. Nature Reviews Drug Discovery, 19(3), 200–218. https://doi.org/10.1038/s41573-019-0052-1