The CD3 monoclonal antibody is directed against the CD3- antigen (T3-antigen), which is expressed on human T lymphocytes. The monoclonal antibody reacts with 80-90% human peripheral T lymphocytes and medullary thymocytes. The monoclonal antibody does not react with B-cells, monocytes, granulocytes and platelets. The monoclonal antibody is mitogenic for resting T lymphocytes and it blocks the cytolytic activity of CTL clones.The CD4 antibody is directed against the CD4-antigen (T4-antigen), which is expressed on human peripheral T lymphocytes and 80% of thymocytes. The monoclonal antibody reacts on a low level with human monocytes and macrophages. The monoclonal antibody does not react with B-cells , granulocytes and thrombocytes.