Correlation of surface marker expression with morphologically and immunologically defined subclasses of acute myeloid leukaemias.

The expression of myeloid-associated cell surface antigens detected by monoclonal antibodies (MoAb: MCS-2, MCS-1, MY7, MY9, Leu-M1, OKM1, VIM-D5, Mol, My-1, MY8, MY4, Leu-M3, VIM-D2, Mo2) of the HLA-DR/Ia-like antigen and of the Fc-receptor was determined on the blast cells from 91 patients with acute myeloid leukaemias classified as M1-M5 in the French-American-British (FAB) system. The surface antigen analysis revealed a highly heterogeneous reaction profile. Nevertheless, distinctive patterns of marker expression referring to morphologically defined subgroups were delineated. Several MoAb (especially MCS-2 and MY7 which were positive in most cases of the five FAB subgroups) appear to be useful for the recognition of myelomonocytic cells regardless of the commitment to either the granulocytic or monocytic cell lineage whereas other Mo Ab (especially MY4, Leu-M3, VIM-D2, Mo2) react predominantly with the monocytic variants and are helpful in the identification of monocytic commitment. The 91 cases could be divided into three immunologically defined phenotypes (Types I-III) corresponding to sequential differentiation levels. Correlations of these MoAb-defined phenotypes with the FAB subtyping showed that immunological and morphological classifications are not completely concordant and that only the parameters Type I and FAB M1 were significantly related. A scheme of early myeloid differentiation sequences based on the expression of surface antigens is presented.