ANTIBODIES TC-12 (UNIQUE) AND TH-111 (CD96) CHARACTERIZE T-CELL ACUTELYMPHOBLASTIC-LEUKEMIA AND A SUBGROUP OF ACUTE MYELOID-LEUKEMIA

To extend the panel of monoclonal antibodies useful for immunophenotyp ing of acute leukemias, two new reagents, TC-12 and TH-111, were devel oped. TC-12 was found ''unique,'' and TH-111 was assigned to the recen tly defined CD96 cluster. Both reagents show little reactivity with bl ood and bone marrow nucleated cells but define a major (TH-111: 78.3%) or an important (TC-12: 45.6%) subset of T-cell acute lymphoblastic l eukemia (ALL). In addition, in acute myeloid leukemia (AML), the expre ssion of TC-12 was found in 64 (20.2%) of 317 and TH-111 in 97 (29.1%) of 333 of these patients. TC-12 positivity in AML was virtually restr icted to the Fab subtypes MO, M1, M2, and M6. In the group of immature AML characterized by the coexpression of CD7 as well as CD117 and CD3 4 positivity, leukemic blasts frequently disclosed the TC-12 and TH-11 1 antigen. Although the TC-12 antigen could not be determined, TH-111 immunoprecipitated the TACTILE (CD96) antigen and, when expressed, was found to be associated with the transferrin receptor. These reagents may help not only to define and dissect T-cell ALL, but also to charac terize a subgroup of immature AML at the divergence of T-cell and myel oid lineage.