DAVID SCHARF / SCIENCE PHOTO LIBRARY DAVID SCHARF / SCIENCE PHOTO LIBRARY
Dendritic and T-cells. Coloured Scanning Electron Micrograph (SEM) of two types of protective cell of the human immune system. A long dendritic or Langerhans cell is seen at top stretching to lower centre. Dendritic cells are phagocytic cells which are found in the epidermis. The cell recognises foreign proteins (antigens) and ingests them into Birbeck granules in its cytoplasm, "processing" the antigen and then secreting it to be dealt with by other immune cells. At lower left is a T-cell, a lymphocyte white blood cell which actively seeks out and destroys microorganisms like viruses. Some T-cells are known as killer T- cells. Magnification: x2370 at 6x7cm size.
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