STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Activated T lymphocytes. Coloured scanning electron micrograph (SEM) of a clump of activated T lymphocytes from a human blood sample. T lymphocytes, or T cells, are a type of white blood cell and components of the body's immune system. They mature in the thymus. T lymphocytes recognise a specific site on the surface of pathogens or foreign objects (antigens), bind to it, and become activated to produce antibodies or cells to eliminate that antigen. Morphologically the cells become more adherent and flattened with many more processes when activated. Specimen courtesy of Professor Greg Towers, University College London. Magnification: x3500 when printed at 10 centimetres wide.
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