Coloured scanning electron micrograph (SEM) of a T-lymphocyte. 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 attract antibodies or cells to eliminate that antigen. Magnification: 10,820X at 10 centimetres wide.