The expression of mature myeloid cell differentiation markers in acute leukemia

Cells from 82 patients with leukemia in acute phase (40 ANLL, 1 AUL, 36 ALL, 5 CGL in blast crisis)¶ were studied for the expression of mature cell markers of the major nonlymphocytic cell lineages (monocytes, granulocytes, erythrocytes and platelets) using monoclonal antibodies. In addition, cells were examined for the presence of HLA-A, B, C antigens, la antigens and common ALL antigen, as well as Fc receptors capable of binding murine immunoglobulins. Approximately one-third of ANLL specimens lacked any of the mature-cell differentiation markers studied. These were always in the relatively undifferentiated morphological subgroups (M1 and M2). Some of the specimens in these groups also expressed little or no HLA-A, B, C and/or la antigen. Of the lineage-specific MAb, FMC32 and FMC34, which bind to monocytes, and monocytes plus granulocytes respectively, gave the most interesting results. Together with the anti-CALLA antibody J5, they contributed to the differential diagnosis of ANLL and ALL. In addition they detected phenotypic heterogeneity within the FAB types of ANLL, particularly the M1 and M2 groups. Binding of murine lgG2a and lgG3 antibodies, apparently via Fc receptors, was commonly observed with ANLL cells. This is a potentially serious source of “false positives" in studies using murine MAb with human leukemic cells.