Lymphocyte white blood cell. Coloured transmission electron micrograph (TEM) of a section through a lymphocyte from a lymph node. Lymphocytes are involved in the immune system's defence mechanisms, lymph system, and antibody production. This cell will divide to give rise to small lymphocytes, which will migrate to blood vessels and circulate around the body. Magnification: x10, 000 when printed 10 centimetres wide.