Application of monoclonal antibodies in the antigenic characteristics of normal myeloid progenitor cells and clonogenic blasts in acute myeloid leukaemia.

The antigenic characteristics of "early" and "late" granulocyte-macrophage progenitor cells (CFU-GM) from normal bone marrow (NBM) and normal peripheral blood (NPB) were studied using 14 selected murine monoclonal antibodies (McAbs) in a complement dependent cytotoxicity assay followed by culture in methyl cellulose. The same panel of McAbs was used to determine the antigens on leukaemic colony-forming cells (CFU-L) from the blood of 14 patients with acute myeloid leukaemia (AML). McAbs L243 (anti-HLA-DR antigen), MY9, S3-13 and S17-25 were cytotoxic almost completely with CFU-GM from NBM as well as from NPB, McAbs R1, B19 and WGHS 29.1 reacted with a high percentage of NBM CFU-GM but not with those from NPB. The antigens expressed on normal CFU-GM were also found on the CFU-L in the majority of patients. However, PMN29 reacted strongly with "late" CFU-GM from NBM and did not react with CFU-L. In contrast, some of the McAbs (S4-7, VIM-2) recognized the antigens on a much higher proportion of CFU-L than "early" CFU-GM from NBM. The expression of the majority of the antigens on leukaemic clonogenic cells tends to vary between different patients and also between the different cells of an individual patient. We conclude that some of the McAbs could be used in the further investigations for their usefulness in the treatment of selected patients with AML, for example in the immunoseparation of leukaemic stem cells of an individual patient.