[Flow cytometric analysis of myeloperoxidase negative acute unclassifiable leukemias by monoclonal antibodies. Acute myelogenous and acute megakaryocytic leukemia].

Pretreatment peripheral and/or bone marrow blasts from 14 patients with acute unclassifiable leukemia (AUL) expressing myeloid related cell-surface antigen (CDII) or megakaryocyte-platelet related cell-surface antigen (OKM6), were isolated for further analysis in this study. Among 11 cases of CD11+AUL, despite a lack of myeloperoxidase (MPO) activity, one patient's blasts possessed Auer rod in a basophilic cytoplasm and another one's blasts expressed MPO maintaining the same surface phenotype after 20 months of his clinical course. The blast from 2 cases possessed both myelomonocytic and monocyte-specific antigens on the cell-surface, whereas the remaining nine cases completely lacked monocyte-specific antigen which is detectable by monoclonal antibodies, Mo2, My4 and Leu M3 (CD14). In addition, we revealed the presence of MPO protein in the cytoplasm of 3 cases of AUL patients by cytoplasmic immunofluorescence test utilizing monoclonal antibody (MA1). Following these results, the former was diagnosed as acute myelomonocytic leukemia (AMMoL) and the latter as acute myelogenous leukemia (AML) by immunophenotypic analysis using flow cytometry (FACS IV) and cytoplasmic immunofluorescence test. We have also described three cases of acute megakaryocytic leukemia which were demonstrated by the presence of megakaryocyte-platelet-related cell-surface antigens detected by utilizing flow cytometry and monoclonal antibodies in addition to both the PPO activity which was shown by ultrastructural cytochemistry, and the emergence of differentiation antigens while culturing these leukemic cells. The blast of 1 case possessed both platelet GPIb and GPIIb/IIIa cell-surface antigens detected by 5F1 (CD36), AN51 (CDw42), and J15, P2 and HPL2 (CDw41), respectively, whereas the remaining two cases almont lacked the GPIb cell-surface antigen. Hence, the former was diagnosed as immature (pro) megakaryocytic leukemia and the latter as acute megakaryoblastic leukemia from the viewpoint of immunophenotypic analysis as will be discussed in this article. These leukemic blasts did not express both T-cell lineage antigens which are detectable by monoclonal antibodies, T6 (CD1), T11 (CD2), T3 (CD3), T4 (CD4), T1 (CD5), Tp40, Leu9 (CD7), T8 (CD8), and B-cell lineage antigens which are detectable by monoclonal antibodies, B4 (CD19), B1 (CD20), B2 (CD21) and J5 (CD10).(ABSTRACT TRUNCATED AT 400 WORDS)