Monoclonal antibody that defines a unique human T-cell leukemia antigen

We have generated and characterized a hybridoma monoclonal antibody, termed SN1, that defines a unique human T-cell leukemia antigen. This antibody was generated by using a human leukemia antigen preparation isolated from cell membranes of MOLT-4, a leukemia T-cell line derived from a patient with T-cell-type acute lymphoblastic leukemia (T-ALL). SN1 was characterized by a sensitive microscale radioimmunoassay using a variety of cultured and uncultured human cells. In selected cases, the cell specimens were further tested by immunoperoxidase staining and an immunofluorescence staining test. The results of the radioimmunoassay were in agreement with those of the two other tests. Among the various cultured malignant and nonmalignant cell lines, SN1 reacted only with leukemia T-cell lines derived from patients with T-ALL; it reacted with all six T-ALL cell lines tested-i.e., JM, CCRF-CEM, CCRF-H-SB2, RPMI 8402, PEER, and MOLT-4. In the case of uncultured cell specimens derived from cancer patients, SN1 reacted with four of four cases of T-ALL but did not react with specimens derived from 41 patients with other types of cancer. SN1 did not react with any normal human cell specimens tested, both cultured and uncultured. These specimens include normal lymphoblastoid cell lines, thymocytes, bone marrow cells, spleen cells, lymph node cells, peripheral blood mononuclear cells, lymphocytes containing B and T cells, purified T cells, monocytes, granulocytes, erythrocytes, and platelets. Furthermore, SN1 did not react with phytohemagglutinin-activated T cells nor with concanavalin A-activated T cells. The results show that monoclonal antibody SN1 defines a type of human leukemia antigen that is expressed on the cell surface of T-cell-type ALL cells. The results further show the usefulness of SN1 in the diagnosis of cancer patients and suggest its therapeutic potential. We designate this antigen TALLA, a T-cell ALL antigen.