This antibody reacts with the CD7-antigen (3A1-antigen), which is expressed on human T lymphocytes.The monoclonal antibody reacts with the cells of the T lymphocyte linage, with the cells of patients with a Lymphocytic Leukaemia of the T lymphocyte origin, and with the cells of patients with the Sezary Syndrome. Platelets and cells of the B lymphocyte myelocytic and monocytic lineage are found negative.