This report describes the production and characterization of two new monoclonal antibodies (MoAb), WM-53 and WM-54, reacting with a human myeloid differentiation antigen, which has recently been assigned by the Third International Leucocyte Workshop on Human Differentiation Antigens into cluster CD-33 ('gp67'). To date, only three other MoAb (MY-9, L1B2, L4F3) have been reported to react with this antigen. In peripheral blood, WM-53 and WM-54 were found to bind to monocytes, but failed to react with erythrocytes, platelets and lymphoid cells. WM-54 was also faintly reactive with granulocytes. Myeloid 'specificity' was also observed with leukaemias as both WM-53 and WM-54 were reactive with most cases of acute myeloid leukaemia (AML), but with only a minority of lymphoid leukaemias. Fluorescence activated cell sorting of normal bone marrow cells demonstrated that both MoAb bound to the majority of CFUgm and CFUmix progenitor cells. Immunoprecipitation studies confirmed that these MoAb, in parallel with MY-9, bound to a protein of approximately 70 KD molecular weight, together with a previously undescribed higher molecular weight component of approximately 140 KD on non-reduced gels, possibly representing a disulphide linked dimer of the lower molecular weight protein. Competitive binding assays, using MoAb WM-53 and WM-54 as well as MY-9, L1B2, and L4F3, demonstrated that all five CD-33 MoAb are capable of competing with each other for binding onto HL-60 cells, suggesting that all recognize a single epitopic site on 'gp67'.
|Number of pages||11|
|Publication status||Published - Dec 1987|