DETECTION OF MYELOPEROXIDASE BY FLOW-CYTOMETRY IN ACUTE-LEUKEMIA

The value of flow cytometric detection of myeloperoxidase (MPO) in the differential diagnosis of acute leukemia was evaluated in 57 cases of acute leukemia and in 9 leukemia cell lines. Cells were fixed and per meabilized with Fix & Perm cell permeabilization kit at room temperatu re for 15 min each, and stained with anti-MPO monoclonal antibody (MPO -7) by direct immunofluorescence. One myeloid cell line, HL-60, was MP O-positive, while the other myeloid cell lines (KG-l, K-562, and MEG-0 1) as well as lymphoid cell lines (KM-3, NALM-6, Raji, REH, and T-ALL- 1) were MPO-negative as previously described. Among acute leukemias, M PO was detected in 23 of 26 cases of acute myeloid leukemia (AML), 7 o f 23 cases of B-lineage acute lymphoblastic leukemia (ALL), 1 of 6 cas es of T-lineage ALL CT-ALL), and 1 of 2 cases of acute unclassified le ukemia (AUL). The intensity of MPO expression in 6 of 7 B-lineage ALL cases was weak compared with AML labeling. There was no detectable cyt ochemical MPO in the cells of ALL, AUL, or AML that stained negative f or anti-MPO. No relationship between the expression of MPO and myeloid lineage surface antigens was observed in ALL. Three cases of MPO-posi tive ALL and AUL could be reclassified as biphenotypic leukemia accord ing to the revised Catovsky scoring system. These results indicate tha t anti-MPO is an excellent marker for the diagnosis and classification of acute leukemia and can be reliably detected by flow cytometry. Thi s rapid technique should be a valuable addition to routine immunopheno typing of acute leukemia. Cytometry (Comm. Clin. Cytometry) 34:198-202 , 1998. (C) 1998 Wiley-Liss, Inc.