Monoclonal antibody directed to human T-cell malignancy antigen.

A murine monoclonal antibody (B2D) against a cultured pre-T acute lymphoblastic leukemia (ALL) cell line THP-6 has been produced. The antibody reacted with seven out of eight cultured T-ALL cell lines and with leukemic cells from three out of four T-ALL/lymphoma patients. The antibody did not react with normal T and B lymphocytes, monocytes, granulocytes, platelets, erythrocytes, bone marrow lymphoid-like precursor cells, thymocytes and other acute and chronic leukemic cells of non-T cell origin. Furthermore, B2D did not react with phytohemagglutinin-activated T cells nor with concanavalin A-activated T cells. The molecules immunoprecipitated with B2D had molecular weights of 50-55 kD. Thus, B2D seems to be highly specific for T-cell malignancies. These results show that B2D defines one of human leukemia antigens which are expressed on the cell surface of T-ALL cells. Monoclonal antibody B2D may be useful for the subclassification of T-ALL cells and has therapeutic potential for a certain type of T-ALL.