JUERGEN BERGER / SCIENCE PHOTO LIBRARY JUERGEN BERGER / SCIENCE PHOTO LIBRARY
Leucocyte. Coloured scanning electron micrograph (SEM) of a white blood cell (leucocyte, yellow). There is a solitary staphylococcus aureus bacterium at bottom right. White blood cells are a major part of the immune system. Some of them directly attack pathogens, some release chemical toxins, and some help other cells kill foreign cells or infected body cells. White blood cells recognise foreign cells by antigens on the invading cell's surface. Some white blood cells synthesise and release antibodies which bind to the antigens and ultimately kill the invading cell. Magnification: x4000 at 6x4.5cm size.
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