Resting T Lymphocytes, coloured scanning electron micrograph (SEM) of resting 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. Magnification: x6000 when printed at 10 centimetres wide