Natural killer (NK) cells are a subset of white blood cells within the immune system, that are the frontline mechanism for destroying the body’s own cells that are potentially harmful, such as cancer cells or cells infected with pathogens. It has been a great immunological puzzle to explain how these cells are able to distinguish between cells to leave alone and cells to destroy.

The scientists, from Imperial College London and led by Professor Dan Davis, from the Department of Life Sciences, have used high speed microscopy imaging techniques to watch the NK cells in action while they decide to kill or spare a given cell. Receptors on the surface of the NK cells are able to interact with proteins expressed on the surface of the other body cells. These NK surface receptors activate or inhibit the killing mechanism of the NK cell. Healthy cells express more of the “inhibitor” surface proteins so more inhibitory receptors become activated. The scientists were able to watch the NK cell “capture” its prey and spread out over the cell surface. Then, depending on whether more activator or inhibitor receptors located their corresponding surface protein, the NK cell decided to kill the captured cell or move off in search of another target.

Dr Fiona Culley, writing in the Public Library of Science detailing the study said: “NK cells play such an important part in our immune response this study adds significantly to our understanding of how NK cells distinguish between healthy and diseased cells”.

By Georgina Lavender