Diversity of acute non-lymphocytic leukemia analyzed with monoclonal antibodies reactive with myeloid differentiation antigens.

The expression of myeloid differentiation antigens on acute nonlymphocytic leukemia cells (ANLL) was analyzed with four distinctive monoclonal antibodies (MoAbs); YM-1, HL-1, 20.2 and 20.3. These four MoAbs were shown to recognize different stages of differentiation of myeloid progenitor cells (CFU-GM) and/or mature myeloid cells. Consequently, leukemia cells of 68 adult patients with ANLL were able to be divided into four groups according to their expression of the antigens defined by these MoAbs: group 1 HL-1(-), YM-1(-), 20.2(-), 20.3(-) (13 cases); group 2 HL-1(+), YM-1(-), 20.2(-), 20.3(-) (16 cases); group 3 HL-1(+), YM-1(+), 20.2(-), 20.3(-) (13 cases) and group 4 HL-1(+), YM-1/20.2/20.3(+/(-)) (26 cases). This classification elucidated not only the maturation stages of ANLL but also the diversity of ANLL. When compared with the morphological classification, acute myeloblastic leukemia (AML) cases (M1 and M2 of the FAB classification) were evenly distributed among all four groups. These data suggest that the AML group was composed of heterogeneous leukemias which expressed surface phenotypes of different maturation stages ranging from the most immature stage to the mature stage. In contrast, the mature type (group 4) was composed of not only AML (M1 and M2), but also acute monocytic leukemia (M4) and acute myelomonocytic leukemia (M5). The clinical courses of these 68 patients revealed that the complete remission rate, remission duration and survival time were not significantly different among the four groups.