Antigenic phenotype of the myeloid leukaemic cells defined by monoclonal antibodies.

The antigenic characteristics of the leukaemic cell population in 31 patients with acute myeloid leukaemia (AML) and 5 patients with acute undifferentiated leukaemia (AUL) was investigated using a panel of 15 monoclonal antibodies (Mc Abs). We chose 14 Mc Abs that react with lineage--and stage related myeloid antigens and L243 Mc Ab that reacts with HLA-DR antigen. In AML cases we correlated the antigenic phenotype with morphological FAB classification. The study indicates a substantial antigenic heterogeneity of the surface antigen expression on leukaemia cells particularly in M1, M2 and M4 AML cases. The morphological subtype of these leukaemias tended to correlate with the immunologic phenotype, particularly in more differentiated AML cases such as M3 or M5. The most immature cell phenotype characterised "undifferentiated" AML, which was expressed by the reactivity or L243, BI3C5, MY9, VIM-2 and S3-13 Mc Abs with the majority of the patients. The analysis shows that although there is a tendency for the morphology to correlate with the surface antigen phenotype each morphological group contains patients having different surface antigen phenotype.