Medical Research Council - London Institute of Medical Sciences

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Friend or Foe?
27 January 2012

Friend or Foe?

White blood cells are a crucial part of our immune system, responsible for defending our bodies against harmful disease. Here, a type of human white blood cell called a natural killer cell (coloured red) comes into contact with a virus-infected cell (shown in blue). When the two cells meet, they have a chemical ‘conversation’ exchanging tiny signalling proteins (yellow dots) between their outer membranes via thin, finger-like structures. Different types of cell display different protein ‘signatures’ on their membranes, and this allows them to communicate and recognise one another. Diseases caused by viruses can alter cell surface proteins, which means white blood cells can recognise infected cells as foe, triggering an immune response. The cells pictured measure only a few thousandths of a millimetre across. To capture these cells in conversation, they must be fixed in formaldehyde, coated with platinum and viewed with an electron microscope.

Written by Emma Stoye

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